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DSHS Dentists is committed to providing each patient with an exceptional level of care and attention. At DSHS Dentists, we are proud to be listed as a five-star dentist. Our dedicated staff works together as a team to provide high-quality comprehensive care. Our compassionate and understanding doctors take pride in paying close attention to each patient's needs.

DSHS Dentists is conveniently located. We offer convenient hours and accept same-day appointments (based on availability).

DSHS Dentists accepts most major insurance plans.

 

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DSHS Dentists
Phone: (253) 479-1898
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Testimonials

"Dr. Jones made me feel comfortable right away. I had a toothache that was interfering with my life. Dr. Jones brought me relief after just one visit. He didn't make m feel bad for neglecting my teeth, and didn't try to sell me more treatment than I needed. Thanks! - George P.
Dr. Watson was incredibly responsive to the stress and pain I was experiencing. She listened to my needs and managed to bring me relief. I used to fear the dentist.but no more! Thanks! - Mariah C.
Dr. Jones not only relieved my pain, but my smile looks better than ever before. This has brought me much joy! - Mark M.
You made me feel comfortable right away. Using your services was the best decision I ever made! - Cynthia E.
Not only do your cleanings make my teeth feel better, but they promote good health. I have never felt better! Thanks! - Bailey T.
Since using your services, I get complimented on my smile often! Thank you so much! - Earl J
When I injured my tooth during a gardening accident, I thought I would never smile again. Thanks to Dr. Jones' patience and amazing technique, I am now a successful hat model. Thanks! - Keith W.

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Services

We proudly provide care for children, adults, and seniors. We understand the need for consistent care. We treat each patient like family. Our compassionate, professional staff is dedicated to providing the highest level of care possible. Because we are dentist owned, we are patient driven. This means that we can focus more on providing excellent care, and less on the bottom line. We are not tied to any large dental corporation. We provide effective care that is responsive to the needs of the community. Being independently owned means that we are able to focus on you!

Our services include:

  • Teeth whitening
  • Ultrasonic Cleaning and Hygiene
  • Periodic Examination
  • Cosmetic Dentistry
  • Restorative Dentistry
  • Oral Surgery
  • Bridges
  • Porcelain Veneers
  • Cosmetic Fillings
  • Dental Implants
  • Crowns
  • Dentures
  • Endodontic Care
  • Laser Diagnosis
  • Laser Care
  • Nitrous Oxide

Although we do offer same-day appointments when available, we encourage making appointments as far in advance as possible. Our friendly staff will be happy to answer any questions you have regarding scheduling and payment arrangements.

We accept the following dental insurance companies:

  • Cosmetic Fillings
  • Dental Implants
  • Crowns
  • Dentures
  • Endodontic Care
  • Laser Diagnosis
  • Laser Care
  • Nitrous Oxide
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About Us

DSHS Dentists was founded with the vision of creating a dental practice that treats every patient with dignity and first-rate care. The nurses and office staff at DSHS Dentists are highly-trained and exceptionally friendly. We understand that for many, visiting a doctor can be a stressful experience. Our comfortable surroundings and compassionate dental professionals will ease your fears.

We accept most major insurance plans.  

No need to worry. We are here to help!

 

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dental implants

Dental implant

From Wikipedia, the free encyclopedia

 

This article may require cleanup to meet Wikipedia's quality standards. Please improve this article if you can. (August 2010)

 

 

A Straumann-brand root-form endosseous dental implant placed in the site of the maxillary left permanent first molar with bone graft used to elevate the sinus floor

A dental implant is an artificial tooth root used in dentistry to support restorations that resemble a tooth or group of teeth.

Virtually all dental implants placed today are root-form endosseous implants. In other words, virtually all dental implants placed in the 21st century appear similar to an actual tooth root (and thus possess a "root-form") and are placed within the bone (end- being the Greek prefix for "in" and osseous referring to "bone").

Prior to the advent of root-form endosseous implants, most implants were either blade endosseous implants, in that the shape of the metal piece placed within the bone resembled a flat blade, or subperiosteal implants, in which a framework was constructed to lie upon and was attached with screws to the exposed bone of the jaws.

Dental implants can be used to support a number of dental prostheses, including crowns, implant-supported bridges or dentures.

Contents [hide]

1 History

2 Composition

3 Training

4 Surgical procedure

4.1 Surgical planning

4.2 Basic procedure

4.3 Detail procedure

4.4 Surgical incisions

4.5 Healing time

4.6 One-stage, two-stage surgery

4.7 Surgical timing

4.8 Immediate placement

4.9 Use of CT scanning

5 Complementary procedures

6 Considerations

7 Success rates

8 Failure

9 Contraindications

10 Market

11 See also

12 References

13 External links

[edit]History

 

The Mayan civilization has been shown to have used the earliest known examples of endosseous implants (implants embedded into bone), dating back over 1,350 years before Per-Ingvar Brånemark started working with titanium. While excavating Mayan burial sites in Honduras in 1931, archaeologists found a fragment of mandible of Mayan origin, dating from about 600 AD. This mandible, which is considered to be that of a woman in her twenties, had three tooth-shaped pieces of shell placed into the sockets of three missing lower incisor teeth. For forty years the archaeological world considered that these shells were placed after death in a manner also observed in the ancient Egyptians. However, in 1970 a Brazilian dental academic, Professor Amadeo Bobbio studied the mandibular specimen and took a series of radiographs. He noted compact bone formation around two of the implants which led him to conclude that the implants were placed during life.

In the 1950s research was being conducted at Cambridge University in England to study blood flow in vivo. These workers devised a method of constructing a chamber of titanium which was then embedded into the soft tissue of the ears of rabbits. In 1952 the Swedish orthopaedic surgeon, P I Brånemark, was interested in studying bone healing and regeneration, and adopted the Cambridge designed ‘rabbit ear chamber’ for use in the rabbit femur. Following several months of study he attempted to retrieve these expensive chambers from the rabbits and found that he was unable to remove them. Per Brånemark observed that bone had grown into such close proximity with the titanium that it effectively adhered to the metal. Brånemark carried out many further studies into this phenomenon, using both animal and human subjects, which all confirmed this unique property of titanium.

Meanwhile an Italian medical doctor called Stefano Melchiade Tramonte, understood that titanium could be used for dental restorations and after designing a titanium screw to support his own dental prosthesis, started to use it on many patients in his clinic in 1959. The good results of his clinical studies on humans were published in 1966.[1]

Although Brånemark had originally considered that the first work should centre on knee and hip surgery, he finally decided that the mouth was more accessible for continued clinical observations and the high rate of edentulism in the general population offered more subjects for widespread study. He termed the clinically observed adherence of bone with titanium as ‘osseointegration’. In 1965 Brånemark, who was by then the Professor of Anatomy at Gothenburg University in Sweden, placed his first titanium dental implant into a human volunteer, a Swede named Gösta Larsson.

Contemporaneous independent research in the United States by Stevens and Alexander led to a 1969 US patent filing for titanium dental implants.[2]

Over the next fourteen years Brånemark published many studies on the use of titanium in dental implantology until in 1978 he entered into a commercial partnership with the Swedish defense company, Bofors AB for the development and marketing of his dental implants. With Bofors (later to become Nobel Industries) as the parent company, Nobelpharma AB (later to be renamed Nobel Biocare) was founded in 1981 to focus on dental implantology. To the present day over 7 million Brånemark System implants have now been placed and hundreds of other companies produce dental implants. The majority of dental implants currently available are shaped like small screws, with either tapered or parallel sides. They can be placed at the same time as a tooth is removed by engaging with the bone of the socket wall and sometimes also with the bone beyond the tip of the socket. Current evidence suggests that implants placed straight into an extraction socket have comparable success rates to those placed into healed bone.[3] The success rate and radiographic results of immediate restorations of dental implants placed in fresh extraction sockets (the temporary crowns placed at the same time) have been shown to be comparable to those obtained with delayed loading (the crowns placed weeks or months later) in carefully selected cases[4]

Some current research in dental implantology is focusing on the use of ceramic materials such as zirconia (ZrO2) in the manufacture of dental implants. Zirconia is the dioxide of zirconium, a metal close to titanium in the periodic table and with similar biocompatability properties.[5] Although generally the same shape as titanium implants, zirconia, which has been used successfully for orthopaedic surgery for a number of years, has the advantage of being more cosmetically aesthetic owing to its bright tooth-like colour.[6] However, long-term clinical data is necessary before one-piece ZrO2 implants can be recommended for daily practice.[7]

[edit]Composition

 

A typical implant consists of a titanium screw (resembling a tooth root) with a roughened or smooth surface. The majority of dental implants are made out of commercially pure titanium, which is available in 4 grades depending upon the amount of carbon and iron contained.[8] More recently grade 5 titanium has increased in use. Grade 5 titanium, Titanium 6AL-4V, (signifying the Titanium alloy containing 6% Aluminium and 4% Vanadium alloy) is believed to offer similar osseointegration levels as commercially pure titanium. Ti-6Al-4V alloy offers better tensile strength and fracture resistance. Today most implants are still made out of commercially pure titanium (grades 1 to 4) but some implant systems (Endopore and NanoTite) are fabricated out of the Ti-6Al-4V alloy.[9] Implant surfaces may be modified by plasma spraying, anodizing,[10] etching or sandblasting to increase the surface area and the integration potential of the implant.

[edit]Training

 

Implant surgery may be performed as an outpatient under general anesthesia, oral conscious sedation, nitrous oxide sedation, intravenous sedation or under local anesthesia by trained and certified clinicians including general dentists, oral surgeons, prosthodontists, and periodontists.

The legal training requirements for dentists who carry out implant treatment differ from country to country. In the UK implant dentistry is considered by the General Dental Council to be a postgraduate sphere of dentistry. In other words it is not sufficiently covered during the teaching of the university dental degree course and dentists wishing to practice in dental implantology legally need to undergo additional formal postgraduate training. The General Dental Council has published strict guidelines on the training required for a dentist to be able to place dental implants in general dental practice.[11] UK dentists need to complete a competency assessed postgraduate extended learning program before providing implant dentistry to patients.

The degree to which both graduate and post-graduate dentists receive training in the surgical placement of implants varies from country to country,[12][13][14] but it seems likely that lack of formal training will lead to higher complication rates.[15]

[edit]Surgical procedure

 

[edit]Surgical planning

Prior to commencement of surgery, careful and detailed planning is required to identify vital structures such as the inferior alveolar nerve or the sinus, as well as the shape and dimensions of the bone to properly orient the implants for the most predictable outcome. Two-dimensional radiographs, such as orthopantomographs or periapicals are often taken prior to the surgery. In most instances, a CT scan will also be obtained. Specialized 3D CAD/CAM computer programs may be used to plan the case.

Whether CT-guided or manual, a 'stent' may sometimes be required to facilitate the placement of implants. A surgical stent is an acrylic wafer that fits over either the teeth, the bone surface or the mucosa (when all the teeth are missing) with pre-drilled holes to show the position and angle of the implants to be placed. The surgical stent may be produced using stereolithography following computerized planning of a case from the CT scan.

[edit]Basic procedure

In its most basic form the placement of an osseointegrated implant requires a preparation into the bone using either hand osteotomes or precision drills with highly regulated speed[16] to prevent burning or pressure necrosis of the bone. After a variable amount of time to allow the bone to grow on to the surface of the implant (osseointegration) a tooth or teeth can be placed on the implant. The amount of time required to place an implant will vary depending on the experience of the practitioner, the quality and quantity of the bone and the difficulty of the individual situation.

[edit]Detail procedure

At edentulous (without teeth) jaw sites, a pilot hole is bored into the recipient bone, taking care to avoid the vital structures (in particular the inferior alveolar nerve or IAN and the mental foramen within the mandible). Drilling into jawbone usually occurs in several separate steps. The pilot hole is expanded by using progressively wider drills (typically between three and seven successive drilling steps, depending on implant width and length). Care is taken not to damage the osteoblast or bone cells by overheating. A cooling saline or water spray keeps the temperature of the bone to below 47 degrees Celsius (approximately 117 degrees Fahrenheit). The implant screw can be self-tapping, and is screwed into place at a precise torque so as not to overload the surrounding bone (overloaded bone can die, a condition called osteonecrosis, which may lead to failure of the implant to fully integrate or bond with the jawbone). Typically in most implant systems, the osteotomy or drilled hole is about 1mm deeper than the implant being placed, due to the shape of the drill tip. Surgeons must take the added length into consideration when drilling in the vicinity of vital structures.

[edit]Surgical incisions

Traditionally, an incision is made over the crest of the site where the implant is to be placed. This is referred to as a 'flap'. Some systems allow for 'flapless' surgery where a piece of mucosa is punched-out from over the implant site. Proponents of 'flapless' surgery believe that it decreases recovery time while its detractors believe it increases complication rates because the edge of bone cannot be visualized.[17][18] Because of these visualization problems flapless surgery is often carried out using a surgical guide constructed following computerized 3D planning of a pre-operative CT scan.

[edit]Healing time

The amount of time required for an implant to become osseointegrated is a hotly debated topic.[19] Consequently the amount of time that practitioners allow the implant to heal before placing a restoration on it varies widely. In general, practitioners allow 2–6 months for healing but preliminary studies show that early loading of implant may not increase early or long term complications.[20] If the implant is loaded too soon, it is possible that the implant may move which results in failure. The subsequent time to heal, possibly graft and eventually place a new implant may take up to eighteen months. For this reason many are reluctant to push the envelope for healing.

[edit]One-stage, two-stage surgery

When an implant is placed either a 'healing abutment', which comes through the mucosa, is placed or a 'cover screw' which is flush with the surface of the dental implant is placed. When a cover screw is placed the mucosa covers the implant while it integrates then a second surgery is completed to place the healing abutment.

Two-stage surgery is sometimes chosen when a concurrent bone graft is placed or surgery on the mucosa may be required for esthetic reasons. Some implants are one piece so that no healing abutment is required.

In carefully selected cases, patients can be implanted and restored in a single surgery, in a procedure labeled "Immediate Loading". In such cases a provisional prosthetic tooth or crown is shaped to avoid the force of the bite transferring to the implant while it integrates with the bone.

[edit]Surgical timing

There are different approaches to place dental implants after tooth extraction. The approaches are:

Immediate post-extraction implant placement.

Delayed immediate post-extraction implant placement (2 weeks to 3 months after extraction).

Late implantation (3 months or more after tooth extraction).

According to the timing of loading of dental implants, the procedure of loading could be classified into:

Immediate loading procedure.

Early loading (1 week to 12 weeks).

Delayed loading (over 3 months)

[edit]Immediate placement

An increasingly common strategy to preserve bone and reduce treatment times includes the placement of a dental implant into a recent extraction site. In addition, immediate loading is becoming more common as success rates for this procedure are now acceptable. This can cut months off the treatment time and in some cases a prosthetic tooth can be attached to the implants at the same time as the surgery to place the dental implants.

Most data suggests that when placed into single rooted tooth sites with healthy bone and mucosa around them, the success rates are comparable to that of delayed procedures with no additional complications.[21]

[edit]Use of CT scanning

When computed tomography, also called cone beam computed tomography or CBCT (3D X-ray imaging) is used preoperatively to accurately pinpoint vital structures including the inferior alveolar canal, the mental foramen, and the maxillary sinus, the chances of complications are dramatically reduced as is chairtime and number of visits.[22] Cone beam CT scanning, when compared to traditional medical CT scanning, utilizes less than 2% of the radiation, provides more accuracy in the area of interest, and is safer for the patient.[23] CBCT allows the surgeon to create a surgical guide, which allows the surgeon to accurately angle the implant into the ideal space, increasing success rates and decreasing post-operative healing.[24]

[edit]Complementary procedures

 

Sinus lifting is a common surgical intervention. A dentist or specialist with proper training such as a periodontist, prosthodontist, or oral surgeon thickens the inadequate part of atrophic maxilla towards the sinus with the help of bone transplantation or bone expletive substance. This results in more volume for a better quality bone site for the implantation. Prudent clinicians who wish to avoid placement of implants into the sinus cavity pre-plan sinus lift surgery using the precision diagnostic guidance afforded by a 3D CBCT X-ray, as in the case of posterior mandibular implants discussed earlier.

Bone grafting will be necessary in cases where there is a lack of adequate maxillary or mandibular bone in terms of front to back (lip to tongue) depth or thickness; top to bottom height; and left to right width. Sufficient bone is needed in three dimensions to securely integrate with the root-like implant. Improved bone height—which is very difficult to achieve—is particularly important to assure ample anchorage of the implant's root-like shape because it has to support the mechanical stress of chewing, just like a natural tooth.

Typically, implantologists try to place implants at least as deeply into bone as the crown or tooth will be above the bone. This is called a 1:1 crown to root ratio. This ratio establishes the target for bone grafting in most cases. If 1:1 or better cannot be achieved, the patient is usually advised that only a short implant can be placed and to not expect a long period of usability.

A wide range of grafting materials and substances may be used during the process of bone grafting / bone replacement. They include the patient's own bone (autograft), which may be harvested from the hip (iliac crest) or from spare jawbone; processed bone from cadavers (allograft); bovine bone or coral (xenograft); or artificially produced bone-like substances (calcium sulfate with names like Regeneform; and hydroxyapatite or HA, which is the primary form of calcium found in bone). The HA is effective as a substrate for osteoblasts to grow on. Some implants are coated with HA for this reason, although the bone forming properties of many of these substances is a hotly debated topic in bone research groups. Alternatively the bone intended to support the implant can be split and widened with the implant placed between the two halves like a sandwich. This is referred to as a 'ridge split' procedure.

Bone graft surgery has its own standard of care. In a typical procedure, the clinician creates a large flap of the gingiva or gum to fully expose the jawbone at the graft site, performs one or several types of block and onlay grafts in and on existing bone, then installs a membrane designed to repel unwanted infection-causing microbiota found in the oral cavity. Then the mucosa is carefully sutured over the site. Together with a course of systemic antibiotics and topical antibacterial mouth rinses, the graft site is allowed to heal (several months).

The clinician typically takes a new radiograph to confirm graft success in width and height, and assumes that positive signs in these two dimensions safely predict success in the third dimension; depth. Where more precision is needed, usually when mandibular implants are being planned, a 3D or cone beam radiograph may be called for at this point to enable accurate measurement of bone and location of nerves and vital structures for proper treatment planning. The same radiographic data set can be employed for the preparation of computer-designed placement guides.

Correctly performed, a bone graft produces live vascular bone which is very much like natural jawbone and is therefore suitable as a foundation for implants.

[edit]Considerations

 

For dental implant procedure to work, there must be enough bone in the jaw, and the bone has to be strong enough to hold and support the implant. If there is not enough bone, more may need to be added with a bone graft procedure discussed earlier. Sometimes, this procedure is called bone augmentation. In addition, natural teeth and supporting tissues near where the implant will be placed must be in good health.

In all cases careful consideration must be given to the final functional aspects of the restoration, such as assessing the forces which will be placed on the implant. Implant loading from chewing and parafunction (abnormal grinding or clenching habits) can exceed the biomechanic tolerance of the implant bone interface and/or the titanium material itself, causing failure. This can be failure of the implant itself (fracture) or bone loss, a "melting" or resorption of the surrounding bone.

The dentist must first determine what type of prosthesis will be fabricated. Only then can the specific implant requirements including number, length, diameter, and thread pattern be determined. In other words, the case must be reverse engineered by the restoring dentist prior to the surgery. If bone volume or density is inadequate, a bone graft procedure must be considered first. The restoring dentist may consult with the periodontist, endodontist, oral surgeon, or another trained general dentist to co-treat the patient. Usually, physical models or impressions of the patient's jawbones and teeth are made by the restorative dentist at the implant surgeons request, and are used as physical aids to treatment planning. If not supplied, the implant surgeon makes his own or relies upon advanced computer-assisted tomography or a cone beam CT scan to achieve the proper treatment plan.

Computer simulation software based on CT scan data allows virtual implant surgical placement based on a barium impregnated prototype of the final prosthesis. This predicts vital anatomy, bone quality, implant characteristics, the need for bone grafting, and maximizing the implant bone surface area for the treatment case creating a high level of predictability. Computer CAD/CAM milled or stereolithography based drill guides can be developed for the implant surgeon to facilitate proper implant placement based on the final prosthesis' occlusion and aesthetics.

Treatment planning software can also be used to demonstrate "try-ins" to the patient on a computer screen. When options have been fully discussed between patient and surgeon, the same software can be used to produce precision drill guides. Specialized software applications such as 'SimPlant' (simulated implant) or 'NobelGuide' use the digital data from a patient's CBCT to build a treatment plan. A data set is then produced and sent to a lab for production of a precision in-mouth drilling guide.[25]

[edit]Success rates

 

Dental implant success is related to operator skill, quality and quantity of the bone available at the site, and the patient's oral hygiene. The consensus is that implants carry a success rate of around 95%[26]

One of the most important factors that determine implant success is the achievement and maintenance of implant stability.[27] The stability is presented as an ISQ (Implant Stability Quotient) value. Other contributing factors to the success of dental implant placement, as with most surgical procedures, include the patient's overall general health and compliance with post-surgical care.

[edit]Failure

 

Failure of a dental implant is often related to failure to osseointegrate correctly. A dental implant is considered to be a failure if it is lost, mobile or shows peri-implant (around the implant) bone loss of greater than 1.0 mm in the first year and greater than 0.2mm a year after.

Dental implants are not susceptible to dental caries but they can develop a condition called peri-implantitis. This is an inflammatory condition of the mucosa and/or bone around the implant which may result in bone loss and eventual loss of the implant. The condition is usually, but not always, associated with a chronic infection. Peri-implantitis is more likely to occur in heavy smokers, patients with diabetes, patients with poor oral hygiene and cases where the mucosa around the implant is thin.[28]

Currently there is no universal agreement on the best treatment for peri-implantitis. The condition and its causes is still poorly understood.[29]

Risk of failure is increased in smokers. For this reason implants are frequently placed only after a patient has stopped smoking as the treatment is very expensive. More rarely, an implant may fail because of poor positioning at the time of surgery, or may be overloaded initially causing failure to integrate. If smoking and positioning problems exist prior to implant surgery, clinicians often advise patients that a bridge or partial denture rather than an implant may be a better solution.

Failure may also occur independently of the causes outlined above. Implants like any other object suffers from wear and tear. If the implants in question are replacing commonly used teeth, then these may suffer from wear and tear and after years may crack and break up. This is a very rare occurrence, however possible. The only way to minimize the risk of this happening is to visit your dentist for regular reviews.

In the majority of cases where an implant fails to integrate with the bone and is rejected by the body the cause is unknown. This may occur in around 5% of cases. To this day we still do not know why bone will integrate with titanium dental implants and why it does not reject the material as a 'foreign body'. Many theories have been postulated over the last five decades. A recent theory argues that rather than being an active biological tissue response, the integration of bone with an implant is the lack of a negative tissue response. In other word for unknown reasons the usual response of the body to reject foreign objects implanted into it does not function correctly with titanium implants. It has further been postulated that an implant rejection occurs in patients whose bone tissues actually react as they naturally should with the 'foreign body' and reject the implant in the same manner that would occur with most other implanted materials.[30]

[edit]Contraindications

 

There are few absolute contraindications to implant dentistry. However there are some systemic, behavioral and anatomic considerations that should be assessed.

Particularly for mandibular (lower jaw) implants, in the vicinity of the mental foramen (MF), there must be sufficient alveolar bone above the mandibular canal also called the inferior alveolar canal or IAC (which acts as the conduit for the neurovascular bundle carrying the inferior alveolar nerve or IAN).

Failure to precisely locate the IAN and MF invites surgical insult by the drills and the implant itself. Such insult may cause irreparable damage to the nerve, often felt as a paresthesia (numbness) or dysesthesia (painful numbness) of the gum, lip and chin. This condition may persist for life and may be accompanied by unconscious drooling.

Uncontrolled type II diabetes is a significant relative contraindication as healing following any type of surgical procedure is delayed due to poor peripheral blood circulation. Anatomic considerations include the volume and height of bone available. Often an ancillary procedure known as a block graft or sinus augmentation are needed to provide enough bone for successful implant placement.

There is new information about intravenous and oral bisphosphonates (taken for certain forms of breast cancer and osteoporosis, respectively) which may put patients at a higher risk of developing a delayed healing syndrome called osteonecrosis. Implants are contraindicated for some patients who take intravenous bisphosphonates.

The many millions of patients who take an oral bisphosphonate (such as Actonel, Fosamax and Boniva) may sometimes be advised to stop the administration prior to implant surgery, then resume several months later. However, current evidence suggests that this protocol may not be necessary. As of January, 2008, an oral bisphosphonate study reported in the February 2008 Journal of Oral and Maxillofacial Surgery, reviewing 115 cases that included 468 implants, concluded "There is no evidence of bisphosphonate-associated osteonecrosis of the jaw in any of the patients evaluated in the clinic and those contacted by phone or e-mail reported no symptoms."[31]

The American Dental Association had addressed bisphosphonates in an article entitled "Bisphosphonate medications and your oral health,"[32] In an Overview, the ADA stated "The risk of developing BON [bisphosphonate-associated osteonecrosis of the jaw] in patients on oral bisphosphonate therapy appears to be very low...". The ADA Council on Scientific Affairs also employed a panel of experts who issued recommendations [for clinicians] for treatment of patients on oral bisphosphonates, published in June, 2006. The overview may be read online at ada.org but it has now been superseded by a huge study—encompassing over 700,000 cases—entitled "Bisphosphonate Use and the Risk of Adverse Jaw Outcomes." Like the 2008 JOMS study, the ADA study exonerates oral bisphosphonates as a contraindication to dental implants.[33]

Bruxism (tooth clenching or grinding) is another consideration which may reduce the prognosis for treatment. The forces generated during bruxism are particularly detrimental to implants while bone is healing; micromovements in the implant positioning are associated with increased rates of implant failure. Bruxism continues to pose a threat to implants throughout the life of the recipient.[34] Natural teeth contain a periodontal ligament allowing each tooth to move and absorb shock in response to vertical and horizontal forces. Once replaced by dental implants, this ligament is lost and teeth are immovably anchored directly into the jaw bone. This problem can be minimized by wearing a custom made mouthguard (such an NTI appliance) at night.

Postoperatively, after implants have been placed, there are physical contraindications that prompt rapid action by the implantology team. Excessive or severe pain lasting more than three days is a warning sign, as is excessive bleeding. Constant numbness of the gingiva (gum), lip and chin—usually noticed after surgical anesthesia wears off—is another warning sign. In the latter case, which may be accompanied by severe constant pain, the standard of care calls for diagnosis to determine if the surgical procedure insulted the IAN. A 3D cone beam X-ray provides the necessary data, but even before this step a prudent implantologist may back out or completely remove an implant in an effort to restore nerve function because delay is usually ineffective. Depending upon the evidence visible with a 3D X-ray, patients may be referred to a specialist in nerve repair. In all cases, speed in diagnosis and treatment are necessary.

[edit]Market

 

In the United States and the United Kingdom, there is no exclusive specialty in 'implantology'.

Any practitioner who carries out implant treatment, whether in the surgical insertion or the final provision of the prosthesis, must be adequately trained. Legal training requirements differ between countries.

In 2008, in the UK the General Dental Council (GDC) laid down strict training requirements[35] for dentists involved in dental implantology. Any dentist in the UK who wishes to train in the field of dental implantology must take part in an extended learning program which covers a detailed theory syllabus, as approved by the GDC,[36] in addition to formal supervised surgical training and mentoring. Dentists must not take part in implant dentistry in the UK until they have been approved by the training provider as having passed a formal competency assessment. Failure to comply with the GDC regulations may result in a dentist being removed from the Dental Register and hence losing the right to practice dentistry in the UK.[37]

[edit]See also

 

Periodontist

Oral and maxillofacial surgery

Bone grafts in Dental Implantology

Dental bridge

Osseointegration

Dental tourism

Gold teeth

American Association of Oral and Maxillofacial Surgeons

European Association for Osseointegration

British Society of Oral Implantology

[edit]References

 

^ Annali di Stomatologia - Su alcuni casi particolarmente interessanti di impianto endosseo con vite autofilettante - Vol XV - Aprile 1966

^ US patent 3579831, Stevens, Irving J.; Alexander, Jerry, "Bone Implant", granted 1971-05-25

^ Quirynen M, Van Assche N, Botticelli D, Berglundh T (2007). "How does the timing of implant placement to extraction affect outcome?". The International Journal of Oral & Maxillofacial Implants 22 Suppl: 203–23. PMID 18437797.

^ Crespi R, Capparé P, Gherlone E, Romanos GE (2008). "Immediate versus delayed loading of dental implants placed in fresh extraction sockets in the maxillary esthetic zone: a clinical comparative study". The International Journal of Oral & Maxillofacial Implants 23 (4): 753–8. PMID 18807574.

^ Gahlert M, Röhling S, Wieland M, Sprecher CM, Kniha H, Milz S (November 2009). "Osseointegration of zirconia and titanium dental implants: a histological and histomorphometrical study in the maxilla of pigs". Clinical Oral Implants Research 20 (11): 1247–53. doi:10.1111/j.1600-0501.2009.01734.x. PMID 19531104.

^ Depprich R, Zipprich H, Ommerborn M, et al. (2008). "Osseointegration of zirconia implants: an SEM observation of the bone-implant interface". Head & Face Medicine 4: 25. doi:10.1186/1746-160X-4-25. PMID 18990214.

^ Andreiotelli M, Kohal RJ (June 2009). "Fracture strength of zirconia implants after artificial aging". Clinical Implant Dentistry and Related Research 11 (2): 158–66. doi:10.1111/j.1708-8208.2008.00105.x. PMID 18657150.

^ Arturo N. Natali (ed.) (2003). "Dental Biomechanics". Taylor & Francis, London / New York, 273 pp., ISBN 9-780-415-30666-9, pp. 69-87.

^ Osseointegration, Zard et al. Quintessence 2009.[verification needed]

^ Palmer R (March 2007). "Ti-unite dental implant surface may be superior to machined surface in replacement of failed implants". The Journal of Evidence-based Dental Practice 7 (1): 8–9. doi:10.1016/j.jebdp.2006.12.001. PMID 17403502.

^ General Dental Council (October 30, 2008). "Doing implants? Make sure you’re up to scratch, warns GDC". Press release. Retrieved 2010-03-25.

^ Melo MD, McGann G, Obeid G (December 2007). "Survey of implant training in oral and maxillofacial surgery residency programs in the United States". Journal of Oral and Maxillofacial Surgery 65 (12): 2554–8. doi:10.1016/j.joms.2007.06.685. PMID 18022483.

 

^ Jokstad A (July 2008). "Where can I learn how to place dental implants? Perspectives from Scandinavia and Canada". International Journal of Oral and Maxillofacial Surgery 37 (7): 593–6. doi:10.1016/j.ijom.2007.12.009. PMID 18295450.

^ Addy LD, Lynch CD, Locke M, Watts A, Gilmour AS (December 2008). "The teaching of implant dentistry in undergraduate dental schools in the United Kingdom and Ireland". British Dental Journal 205 (11): 609–14. doi:10.1038/sj.bdj.2008.1027. PMID 19079107.

 

^ Binon PP (July 2007). "Treatment planning complications and surgical miscues". Journal of Oral and Maxillofacial Surgery 65 (7 Suppl 1): 73–92. doi:10.1016/j.joms.2007.03.014. PMID 17586352.

^ Brisman DL (1996). "The effect of speed, pressure, and time on bone temperature during the drilling of implant sites". The International Journal of Oral & Maxillofacial Implants 11 (1): 35–7. PMID 8820120.

^ Berdougo M, Fortin T, Blanchet E, Isidori M, Bosson JL (February 2009). "Flapless Implant Surgery Using an Image-Guided System. A 1- to 4-Year Retrospective Multicenter Comparative Clinical Study". Clinical Implant Dentistry and Related Research 12 (2): 142–52. doi:10.1111/j.1708-8208.2008.00146.x. PMID 19220842.

^ Becker W, Goldstein M, Becker BE, Sennerby L, Kois D, Hujoel P (February 2009). "Minimally invasive flapless implant placement: follow-up results from a multicenter study". Journal of Periodontology 80 (2): 347–52. doi:10.1902/jop.2009.080286. PMID 19186977.

^ Gerds TA, Vogeler M (December 2005). "Endpoints and survival analysis for successful osseointegration of dental implants". Statistical Methods in Medical Research 14 (6): 579–90. doi:10.1191/0962280205sm420oa. PMID 16355545.

^ Fischer K, Stenberg T, Hedin M, Sennerby L (May 2008). "Five-year results from a randomized, controlled trial on early and delayed loading of implants supporting full-arch prosthesis in the edentulous maxilla". Clinical Oral Implants Research 19 (5): 433–41. doi:10.1111/j.1600-0501.2007.01510.x. PMID 18371094.

^ Bhola M, Neely AL, Kolhatkar S (October 2008). "Immediate implant placement: clinical decisions, advantages, and disadvantages". Journal of Prosthodontics 17 (7): 576–81. doi:10.1111/j.1532-849X.2008.00359.x. PMID 18761580.

^ Spector L (October 2008). "Computer-aided dental implant planning". Dental Clinics of North America 52 (4): 761–75, vi. doi:10.1016/j.cden.2008.05.004. PMID 18805228.

^ Ludlow JB (November 2008). "Regarding 'Influence of CBCT exposure conditions on radiation dose'". Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics 106 (5): 627–8; author reply 628–9. doi:10.1016/j.tripleo.2008.06.031. PMID 18801676.

^ Viegas VN, Dutra V, Pagnoncelli RM, de Oliveira MG (January 2010). "Transference of virtual planning and planning over biomedical prototypes for dental implant placement using guided surgery". Clinical Oral Implants Research 21 (3): 290–5. doi:10.1111/j.1600-0501.2009.01833.x. PMID 20074239.

^ http://www.materialise.com/materialise/view/en/554529-SurgiGuide.html

^ Esposito M, Grusovin MG, Willings M, Coulthard P, Worthington HV (2007). "The effectiveness of immediate, early, and conventional loading of dental implants: a Cochrane systematic review of randomized controlled clinical trials". The International Journal of Oral & Maxillofacial Implants 22 (6): 893–904. PMID 18271370.

^ Albrektsson T, Zarb GA (1993). "Current interpretations of the osseointegrated response: clinical significance". The International Journal of Prosthodontics 6 (2): 95–105. PMID 8329101.

^ Fransson C, Wennström J, Tomasi C, Berglundh T (April 2009). "Extent of peri-implantitis-associated bone loss". Journal of Clinical Periodontology 36 (4): 357–63. doi:10.1111/j.1600-051X.2009.01375.x. PMID 19426183.

^ Pye AD, Lockhart DE, Dawson MP, Murray CA, Smith AJ (June 2009). "A review of dental implants and infection". The Journal of Hospital Infection 72 (2): 104–10. doi:10.1016/j.jhin.2009.02.010. PMID 19329223.

^ Mavrogenis AF, Dimitriou R, Parvizi J, Babis GC (2009). "Biology of implant osseointegration". Journal of Musculoskeletal & Neuronal Interactions 9 (2): 61–71. PMID 19516081.

^ Grant BT, Amenedo C, Freeman K, Kraut RA (February 2008). "Outcomes of placing dental implants in patients taking oral bisphosphonates: a review of 115 cases". Journal of Oral and Maxillofacial Surgery 66 (2): 223–30. doi:10.1016/j.joms.2007.09.019. PMID 18201600.

^ "Bisphosphonate medications and your oral health". Journal of the American Dental Association 137 (7): 1048. July 2006. PMID 16803833.

^ Cartsos VM, Zhu S, Zavras AI (January 2008). "Bisphosphonate use and the risk of adverse jaw outcomes: a medical claims study of 714,217 people". Journal of the American Dental Association 139 (1): 23–30. PMID 18167381.

^ McCoy G (2002). "Recognizing and managing parafunction in the reconstruction and maintenance of the oral implant patient". Implant Dentistry 11 (1): 19–27. PMID 11915541.

^ http://www.gdc-uk.org/Our+work/Education+and+quality+assurance/Policy+statement+on+implantology.htm

^ Training Standards in Implant Dentistry. The Royal College of Surgeons of England; London 2008[page needed]

^ Policy Statement on Implant Dentistry. The General Dental Council; London. 9th April 2008[page needed]

[edit]External links

 

 

This article's use of external links may not follow Wikipedia's policies or guidelines. Please improve this article by removing excessive and inappropriate external links or by converting links into footnote references. (February 2010)

OsseoNews Expert Discussions on Dental Implants

American Academy of Implant Dentistry

Academy of Osseointegration, professional association of implant dentists

ITI:International Team for Implantology, professional association of implant dentists

American Academy of Periodontology, dental implants guide

Association of Dental Implantology UK

Implant Dentistry

American Dental Implant Association

International Congress of Oral Implantologists

South African Society for Periodontology

Dental Implants Before and After

Journal of Implant and Advanced Clinical Dentistry

Journal of Dental Implantology

Encyclopedia about Dental Implants in Russian

Nelson S, Thomas G (May 2009). "Bacterial Persistence in Dentoalveolar Bone Following Extraction: A Microbiological Study and Implications for Dental Implant Treatment". Clinical Implant Dentistry and Related Research. doi:10.1111/j.1708-8208.2009.00165.x. PMID 19438939.

Website for determining implants from just a radiograph

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Dentistry

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Endodontics - Oral and Maxillofacial Pathology - Oral and Maxillofacial Radiology - Oral and Maxillofacial Surgery - Orthodontics and Dentofacial Orthopedics - Pediatric Dentistry - Periodontics - Prosthodontics - Dental public health

Unrecognized Specialties

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Cosmetic Dentistry - Dental Implantology - Temporomandibular Joint Disorder - Geriatric dentistry - Restorative Dentistry - Forensic Odontology - Dental Traumatology

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Categories: Dentistry | Implants | Restorative dentistry | Prosthetics | Oral surgery | Oral and maxillofacial surgery | Medical technology


Dr. Hugh Leung DDS DMD dentist


Dr. Hugh Leung DDS DMD dentist

Dr. Hugh Leung DDS DMD dentist

Dr. Hugh Leung DDS DMD dentist

Dr. Hugh Leung DDS DMD dentist

Dr. Hugh Leung DDS DMD dentist

Dr. Hugh Leung DDS DMD dentist

Dr. Hugh Leung DDS DMD dentist

Dr. Hugh Leung DDS DMD dentist

 

dental implants

Dental implant

From Wikipedia, the free encyclopedia

 

This article may require cleanup to meet Wikipedia's quality standards. Please improve this article if you can. (August 2010)

 

 

A Straumann-brand root-form endosseous dental implant placed in the site of the maxillary left permanent first molar with bone graft used to elevate the sinus floor

A dental implant is an artificial tooth root used in dentistry to support restorations that resemble a tooth or group of teeth.

Virtually all dental implants placed today are root-form endosseous implants. In other words, virtually all dental implants placed in the 21st century appear similar to an actual tooth root (and thus possess a "root-form") and are placed within the bone (end- being the Greek prefix for "in" and osseous referring to "bone").

Prior to the advent of root-form endosseous implants, most implants were either blade endosseous implants, in that the shape of the metal piece placed within the bone resembled a flat blade, or subperiosteal implants, in which a framework was constructed to lie upon and was attached with screws to the exposed bone of the jaws.

Dental implants can be used to support a number of dental prostheses, including crowns, implant-supported bridges or dentures.

Contents [hide]

1 History

2 Composition

3 Training

4 Surgical procedure

4.1 Surgical planning

4.2 Basic procedure

4.3 Detail procedure

4.4 Surgical incisions

4.5 Healing time

4.6 One-stage, two-stage surgery

4.7 Surgical timing

4.8 Immediate placement

4.9 Use of CT scanning

5 Complementary procedures

6 Considerations

7 Success rates

8 Failure

9 Contraindications

10 Market

11 See also

12 References

13 External links

[edit]History

 

The Mayan civilization has been shown to have used the earliest known examples of endosseous implants (implants embedded into bone), dating back over 1,350 years before Per-Ingvar Brånemark started working with titanium. While excavating Mayan burial sites in Honduras in 1931, archaeologists found a fragment of mandible of Mayan origin, dating from about 600 AD. This mandible, which is considered to be that of a woman in her twenties, had three tooth-shaped pieces of shell placed into the sockets of three missing lower incisor teeth. For forty years the archaeological world considered that these shells were placed after death in a manner also observed in the ancient Egyptians. However, in 1970 a Brazilian dental academic, Professor Amadeo Bobbio studied the mandibular specimen and took a series of radiographs. He noted compact bone formation around two of the implants which led him to conclude that the implants were placed during life.

In the 1950s research was being conducted at Cambridge University in England to study blood flow in vivo. These workers devised a method of constructing a chamber of titanium which was then embedded into the soft tissue of the ears of rabbits. In 1952 the Swedish orthopaedic surgeon, P I Brånemark, was interested in studying bone healing and regeneration, and adopted the Cambridge designed ‘rabbit ear chamber’ for use in the rabbit femur. Following several months of study he attempted to retrieve these expensive chambers from the rabbits and found that he was unable to remove them. Per Brånemark observed that bone had grown into such close proximity with the titanium that it effectively adhered to the metal. Brånemark carried out many further studies into this phenomenon, using both animal and human subjects, which all confirmed this unique property of titanium.

Meanwhile an Italian medical doctor called Stefano Melchiade Tramonte, understood that titanium could be used for dental restorations and after designing a titanium screw to support his own dental prosthesis, started to use it on many patients in his clinic in 1959. The good results of his clinical studies on humans were published in 1966.[1]

Although Brånemark had originally considered that the first work should centre on knee and hip surgery, he finally decided that the mouth was more accessible for continued clinical observations and the high rate of edentulism in the general population offered more subjects for widespread study. He termed the clinically observed adherence of bone with titanium as ‘osseointegration’. In 1965 Brånemark, who was by then the Professor of Anatomy at Gothenburg University in Sweden, placed his first titanium dental implant into a human volunteer, a Swede named Gösta Larsson.

Contemporaneous independent research in the United States by Stevens and Alexander led to a 1969 US patent filing for titanium dental implants.[2]

Over the next fourteen years Brånemark published many studies on the use of titanium in dental implantology until in 1978 he entered into a commercial partnership with the Swedish defense company, Bofors AB for the development and marketing of his dental implants. With Bofors (later to become Nobel Industries) as the parent company, Nobelpharma AB (later to be renamed Nobel Biocare) was founded in 1981 to focus on dental implantology. To the present day over 7 million Brånemark System implants have now been placed and hundreds of other companies produce dental implants. The majority of dental implants currently available are shaped like small screws, with either tapered or parallel sides. They can be placed at the same time as a tooth is removed by engaging with the bone of the socket wall and sometimes also with the bone beyond the tip of the socket. Current evidence suggests that implants placed straight into an extraction socket have comparable success rates to those placed into healed bone.[3] The success rate and radiographic results of immediate restorations of dental implants placed in fresh extraction sockets (the temporary crowns placed at the same time) have been shown to be comparable to those obtained with delayed loading (the crowns placed weeks or months later) in carefully selected cases[4]

Some current research in dental implantology is focusing on the use of ceramic materials such as zirconia (ZrO2) in the manufacture of dental implants. Zirconia is the dioxide of zirconium, a metal close to titanium in the periodic table and with similar biocompatability properties.[5] Although generally the same shape as titanium implants, zirconia, which has been used successfully for orthopaedic surgery for a number of years, has the advantage of being more cosmetically aesthetic owing to its bright tooth-like colour.[6] However, long-term clinical data is necessary before one-piece ZrO2 implants can be recommended for daily practice.[7]

[edit]Composition

 

A typical implant consists of a titanium screw (resembling a tooth root) with a roughened or smooth surface. The majority of dental implants are made out of commercially pure titanium, which is available in 4 grades depending upon the amount of carbon and iron contained.[8] More recently grade 5 titanium has increased in use. Grade 5 titanium, Titanium 6AL-4V, (signifying the Titanium alloy containing 6% Aluminium and 4% Vanadium alloy) is believed to offer similar osseointegration levels as commercially pure titanium. Ti-6Al-4V alloy offers better tensile strength and fracture resistance. Today most implants are still made out of commercially pure titanium (grades 1 to 4) but some implant systems (Endopore and NanoTite) are fabricated out of the Ti-6Al-4V alloy.[9] Implant surfaces may be modified by plasma spraying, anodizing,[10] etching or sandblasting to increase the surface area and the integration potential of the implant.

[edit]Training

 

Implant surgery may be performed as an outpatient under general anesthesia, oral conscious sedation, nitrous oxide sedation, intravenous sedation or under local anesthesia by trained and certified clinicians including general dentists, oral surgeons, prosthodontists, and periodontists.

The legal training requirements for dentists who carry out implant treatment differ from country to country. In the UK implant dentistry is considered by the General Dental Council to be a postgraduate sphere of dentistry. In other words it is not sufficiently covered during the teaching of the university dental degree course and dentists wishing to practice in dental implantology legally need to undergo additional formal postgraduate training. The General Dental Council has published strict guidelines on the training required for a dentist to be able to place dental implants in general dental practice.[11] UK dentists need to complete a competency assessed postgraduate extended learning program before providing implant dentistry to patients.

The degree to which both graduate and post-graduate dentists receive training in the surgical placement of implants varies from country to country,[12][13][14] but it seems likely that lack of formal training will lead to higher complication rates.[15]

[edit]Surgical procedure

 

[edit]Surgical planning

Prior to commencement of surgery, careful and detailed planning is required to identify vital structures such as the inferior alveolar nerve or the sinus, as well as the shape and dimensions of the bone to properly orient the implants for the most predictable outcome. Two-dimensional radiographs, such as orthopantomographs or periapicals are often taken prior to the surgery. In most instances, a CT scan will also be obtained. Specialized 3D CAD/CAM computer programs may be used to plan the case.

Whether CT-guided or manual, a 'stent' may sometimes be required to facilitate the placement of implants. A surgical stent is an acrylic wafer that fits over either the teeth, the bone surface or the mucosa (when all the teeth are missing) with pre-drilled holes to show the position and angle of the implants to be placed. The surgical stent may be produced using stereolithography following computerized planning of a case from the CT scan.

[edit]Basic procedure

In its most basic form the placement of an osseointegrated implant requires a preparation into the bone using either hand osteotomes or precision drills with highly regulated speed[16] to prevent burning or pressure necrosis of the bone. After a variable amount of time to allow the bone to grow on to the surface of the implant (osseointegration) a tooth or teeth can be placed on the implant. The amount of time required to place an implant will vary depending on the experience of the practitioner, the quality and quantity of the bone and the difficulty of the individual situation.

[edit]Detail procedure

At edentulous (without teeth) jaw sites, a pilot hole is bored into the recipient bone, taking care to avoid the vital structures (in particular the inferior alveolar nerve or IAN and the mental foramen within the mandible). Drilling into jawbone usually occurs in several separate steps. The pilot hole is expanded by using progressively wider drills (typically between three and seven successive drilling steps, depending on implant width and length). Care is taken not to damage the osteoblast or bone cells by overheating. A cooling saline or water spray keeps the temperature of the bone to below 47 degrees Celsius (approximately 117 degrees Fahrenheit). The implant screw can be self-tapping, and is screwed into place at a precise torque so as not to overload the surrounding bone (overloaded bone can die, a condition called osteonecrosis, which may lead to failure of the implant to fully integrate or bond with the jawbone). Typically in most implant systems, the osteotomy or drilled hole is about 1mm deeper than the implant being placed, due to the shape of the drill tip. Surgeons must take the added length into consideration when drilling in the vicinity of vital structures.

[edit]Surgical incisions

Traditionally, an incision is made over the crest of the site where the implant is to be placed. This is referred to as a 'flap'. Some systems allow for 'flapless' surgery where a piece of mucosa is punched-out from over the implant site. Proponents of 'flapless' surgery believe that it decreases recovery time while its detractors believe it increases complication rates because the edge of bone cannot be visualized.[17][18] Because of these visualization problems flapless surgery is often carried out using a surgical guide constructed following computerized 3D planning of a pre-operative CT scan.

[edit]Healing time

The amount of time required for an implant to become osseointegrated is a hotly debated topic.[19] Consequently the amount of time that practitioners allow the implant to heal before placing a restoration on it varies widely. In general, practitioners allow 2–6 months for healing but preliminary studies show that early loading of implant may not increase early or long term complications.[20] If the implant is loaded too soon, it is possible that the implant may move which results in failure. The subsequent time to heal, possibly graft and eventually place a new implant may take up to eighteen months. For this reason many are reluctant to push the envelope for healing.

[edit]One-stage, two-stage surgery

When an implant is placed either a 'healing abutment', which comes through the mucosa, is placed or a 'cover screw' which is flush with the surface of the dental implant is placed. When a cover screw is placed the mucosa covers the implant while it integrates then a second surgery is completed to place the healing abutment.

Two-stage surgery is sometimes chosen when a concurrent bone graft is placed or surgery on the mucosa may be required for esthetic reasons. Some implants are one piece so that no healing abutment is required.

In carefully selected cases, patients can be implanted and restored in a single surgery, in a procedure labeled "Immediate Loading". In such cases a provisional prosthetic tooth or crown is shaped to avoid the force of the bite transferring to the implant while it integrates with the bone.

[edit]Surgical timing

There are different approaches to place dental implants after tooth extraction. The approaches are:

Immediate post-extraction implant placement.

Delayed immediate post-extraction implant placement (2 weeks to 3 months after extraction).

Late implantation (3 months or more after tooth extraction).

According to the timing of loading of dental implants, the procedure of loading could be classified into:

Immediate loading procedure.

Early loading (1 week to 12 weeks).

Delayed loading (over 3 months)

[edit]Immediate placement

An increasingly common strategy to preserve bone and reduce treatment times includes the placement of a dental implant into a recent extraction site. In addition, immediate loading is becoming more common as success rates for this procedure are now acceptable. This can cut months off the treatment time and in some cases a prosthetic tooth can be attached to the implants at the same time as the surgery to place the dental implants.

Most data suggests that when placed into single rooted tooth sites with healthy bone and mucosa around them, the success rates are comparable to that of delayed procedures with no additional complications.[21]

[edit]Use of CT scanning

When computed tomography, also called cone beam computed tomography or CBCT (3D X-ray imaging) is used preoperatively to accurately pinpoint vital structures including the inferior alveolar canal, the mental foramen, and the maxillary sinus, the chances of complications are dramatically reduced as is chairtime and number of visits.[22] Cone beam CT scanning, when compared to traditional medical CT scanning, utilizes less than 2% of the radiation, provides more accuracy in the area of interest, and is safer for the patient.[23] CBCT allows the surgeon to create a surgical guide, which allows the surgeon to accurately angle the implant into the ideal space, increasing success rates and decreasing post-operative healing.[24]

[edit]Complementary procedures

 

Sinus lifting is a common surgical intervention. A dentist or specialist with proper training such as a periodontist, prosthodontist, or oral surgeon thickens the inadequate part of atrophic maxilla towards the sinus with the help of bone transplantation or bone expletive substance. This results in more volume for a better quality bone site for the implantation. Prudent clinicians who wish to avoid placement of implants into the sinus cavity pre-plan sinus lift surgery using the precision diagnostic guidance afforded by a 3D CBCT X-ray, as in the case of posterior mandibular implants discussed earlier.

Bone grafting will be necessary in cases where there is a lack of adequate maxillary or mandibular bone in terms of front to back (lip to tongue) depth or thickness; top to bottom height; and left to right width. Sufficient bone is needed in three dimensions to securely integrate with the root-like implant. Improved bone height—which is very difficult to achieve—is particularly important to assure ample anchorage of the implant's root-like shape because it has to support the mechanical stress of chewing, just like a natural tooth.

Typically, implantologists try to place implants at least as deeply into bone as the crown or tooth will be above the bone. This is called a 1:1 crown to root ratio. This ratio establishes the target for bone grafting in most cases. If 1:1 or better cannot be achieved, the patient is usually advised that only a short implant can be placed and to not expect a long period of usability.

A wide range of grafting materials and substances may be used during the process of bone grafting / bone replacement. They include the patient's own bone (autograft), which may be harvested from the hip (iliac crest) or from spare jawbone; processed bone from cadavers (allograft); bovine bone or coral (xenograft); or artificially produced bone-like substances (calcium sulfate with names like Regeneform; and hydroxyapatite or HA, which is the primary form of calcium found in bone). The HA is effective as a substrate for osteoblasts to grow on. Some implants are coated with HA for this reason, although the bone forming properties of many of these substances is a hotly debated topic in bone research groups. Alternatively the bone intended to support the implant can be split and widened with the implant placed between the two halves like a sandwich. This is referred to as a 'ridge split' procedure.

Bone graft surgery has its own standard of care. In a typical procedure, the clinician creates a large flap of the gingiva or gum to fully expose the jawbone at the graft site, performs one or several types of block and onlay grafts in and on existing bone, then installs a membrane designed to repel unwanted infection-causing microbiota found in the oral cavity. Then the mucosa is carefully sutured over the site. Together with a course of systemic antibiotics and topical antibacterial mouth rinses, the graft site is allowed to heal (several months).

The clinician typically takes a new radiograph to confirm graft success in width and height, and assumes that positive signs in these two dimensions safely predict success in the third dimension; depth. Where more precision is needed, usually when mandibular implants are being planned, a 3D or cone beam radiograph may be called for at this point to enable accurate measurement of bone and location of nerves and vital structures for proper treatment planning. The same radiographic data set can be employed for the preparation of computer-designed placement guides.

Correctly performed, a bone graft produces live vascular bone which is very much like natural jawbone and is therefore suitable as a foundation for implants.

[edit]Considerations

 

For dental implant procedure to work, there must be enough bone in the jaw, and the bone has to be strong enough to hold and support the implant. If there is not enough bone, more may need to be added with a bone graft procedure discussed earlier. Sometimes, this procedure is called bone augmentation. In addition, natural teeth and supporting tissues near where the implant will be placed must be in good health.

In all cases careful consideration must be given to the final functional aspects of the restoration, such as assessing the forces which will be placed on the implant. Implant loading from chewing and parafunction (abnormal grinding or clenching habits) can exceed the biomechanic tolerance of the implant bone interface and/or the titanium material itself, causing failure. This can be failure of the implant itself (fracture) or bone loss, a "melting" or resorption of the surrounding bone.

The dentist must first determine what type of prosthesis will be fabricated. Only then can the specific implant requirements including number, length, diameter, and thread pattern be determined. In other words, the case must be reverse engineered by the restoring dentist prior to the surgery. If bone volume or density is inadequate, a bone graft procedure must be considered first. The restoring dentist may consult with the periodontist, endodontist, oral surgeon, or another trained general dentist to co-treat the patient. Usually, physical models or impressions of the patient's jawbones and teeth are made by the restorative dentist at the implant surgeons request, and are used as physical aids to treatment planning. If not supplied, the implant surgeon makes his own or relies upon advanced computer-assisted tomography or a cone beam CT scan to achieve the proper treatment plan.

Computer simulation software based on CT scan data allows virtual implant surgical placement based on a barium impregnated prototype of the final prosthesis. This predicts vital anatomy, bone quality, implant characteristics, the need for bone grafting, and maximizing the implant bone surface area for the treatment case creating a high level of predictability. Computer CAD/CAM milled or stereolithography based drill guides can be developed for the implant surgeon to facilitate proper implant placement based on the final prosthesis' occlusion and aesthetics.

Treatment planning software can also be used to demonstrate "try-ins" to the patient on a computer screen. When options have been fully discussed between patient and surgeon, the same software can be used to produce precision drill guides. Specialized software applications such as 'SimPlant' (simulated implant) or 'NobelGuide' use the digital data from a patient's CBCT to build a treatment plan. A data set is then produced and sent to a lab for production of a precision in-mouth drilling guide.[25]

[edit]Success rates

 

Dental implant success is related to operator skill, quality and quantity of the bone available at the site, and the patient's oral hygiene. The consensus is that implants carry a success rate of around 95%[26]

One of the most important factors that determine implant success is the achievement and maintenance of implant stability.[27] The stability is presented as an ISQ (Implant Stability Quotient) value. Other contributing factors to the success of dental implant placement, as with most surgical procedures, include the patient's overall general health and compliance with post-surgical care.

[edit]Failure

 

Failure of a dental implant is often related to failure to osseointegrate correctly. A dental implant is considered to be a failure if it is lost, mobile or shows peri-implant (around the implant) bone loss of greater than 1.0 mm in the first year and greater than 0.2mm a year after.

Dental implants are not susceptible to dental caries but they can develop a condition called peri-implantitis. This is an inflammatory condition of the mucosa and/or bone around the implant which may result in bone loss and eventual loss of the implant. The condition is usually, but not always, associated with a chronic infection. Peri-implantitis is more likely to occur in heavy smokers, patients with diabetes, patients with poor oral hygiene and cases where the mucosa around the implant is thin.[28]

Currently there is no universal agreement on the best treatment for peri-implantitis. The condition and its causes is still poorly understood.[29]

Risk of failure is increased in smokers. For this reason implants are frequently placed only after a patient has stopped smoking as the treatment is very expensive. More rarely, an implant may fail because of poor positioning at the time of surgery, or may be overloaded initially causing failure to integrate. If smoking and positioning problems exist prior to implant surgery, clinicians often advise patients that a bridge or partial denture rather than an implant may be a better solution.

Failure may also occur independently of the causes outlined above. Implants like any other object suffers from wear and tear. If the implants in question are replacing commonly used teeth, then these may suffer from wear and tear and after years may crack and break up. This is a very rare occurrence, however possible. The only way to minimize the risk of this happening is to visit your dentist for regular reviews.

In the majority of cases where an implant fails to integrate with the bone and is rejected by the body the cause is unknown. This may occur in around 5% of cases. To this day we still do not know why bone will integrate with titanium dental implants and why it does not reject the material as a 'foreign body'. Many theories have been postulated over the last five decades. A recent theory argues that rather than being an active biological tissue response, the integration of bone with an implant is the lack of a negative tissue response. In other word for unknown reasons the usual response of the body to reject foreign objects implanted into it does not function correctly with titanium implants. It has further been postulated that an implant rejection occurs in patients whose bone tissues actually react as they naturally should with the 'foreign body' and reject the implant in the same manner that would occur with most other implanted materials.[30]

[edit]Contraindications

 

There are few absolute contraindications to implant dentistry. However there are some systemic, behavioral and anatomic considerations that should be assessed.

Particularly for mandibular (lower jaw) implants, in the vicinity of the mental foramen (MF), there must be sufficient alveolar bone above the mandibular canal also called the inferior alveolar canal or IAC (which acts as the conduit for the neurovascular bundle carrying the inferior alveolar nerve or IAN).

Failure to precisely locate the IAN and MF invites surgical insult by the drills and the implant itself. Such insult may cause irreparable damage to the nerve, often felt as a paresthesia (numbness) or dysesthesia (painful numbness) of the gum, lip and chin. This condition may persist for life and may be accompanied by unconscious drooling.

Uncontrolled type II diabetes is a significant relative contraindication as healing following any type of surgical procedure is delayed due to poor peripheral blood circulation. Anatomic considerations include the volume and height of bone available. Often an ancillary procedure known as a block graft or sinus augmentation are needed to provide enough bone for successful implant placement.

There is new information about intravenous and oral bisphosphonates (taken for certain forms of breast cancer and osteoporosis, respectively) which may put patients at a higher risk of developing a delayed healing syndrome called osteonecrosis. Implants are contraindicated for some patients who take intravenous bisphosphonates.

The many millions of patients who take an oral bisphosphonate (such as Actonel, Fosamax and Boniva) may sometimes be advised to stop the administration prior to implant surgery, then resume several months later. However, current evidence suggests that this protocol may not be necessary. As of January, 2008, an oral bisphosphonate study reported in the February 2008 Journal of Oral and Maxillofacial Surgery, reviewing 115 cases that included 468 implants, concluded "There is no evidence of bisphosphonate-associated osteonecrosis of the jaw in any of the patients evaluated in the clinic and those contacted by phone or e-mail reported no symptoms."[31]

The American Dental Association had addressed bisphosphonates in an article entitled "Bisphosphonate medications and your oral health,"[32] In an Overview, the ADA stated "The risk of developing BON [bisphosphonate-associated osteonecrosis of the jaw] in patients on oral bisphosphonate therapy appears to be very low...". The ADA Council on Scientific Affairs also employed a panel of experts who issued recommendations [for clinicians] for treatment of patients on oral bisphosphonates, published in June, 2006. The overview may be read online at ada.org but it has now been superseded by a huge study—encompassing over 700,000 cases—entitled "Bisphosphonate Use and the Risk of Adverse Jaw Outcomes." Like the 2008 JOMS study, the ADA study exonerates oral bisphosphonates as a contraindication to dental implants.[33]

Bruxism (tooth clenching or grinding) is another consideration which may reduce the prognosis for treatment. The forces generated during bruxism are particularly detrimental to implants while bone is healing; micromovements in the implant positioning are associated with increased rates of implant failure. Bruxism continues to pose a threat to implants throughout the life of the recipient.[34] Natural teeth contain a periodontal ligament allowing each tooth to move and absorb shock in response to vertical and horizontal forces. Once replaced by dental implants, this ligament is lost and teeth are immovably anchored directly into the jaw bone. This problem can be minimized by wearing a custom made mouthguard (such an NTI appliance) at night.

Postoperatively, after implants have been placed, there are physical contraindications that prompt rapid action by the implantology team. Excessive or severe pain lasting more than three days is a warning sign, as is excessive bleeding. Constant numbness of the gingiva (gum), lip and chin—usually noticed after surgical anesthesia wears off—is another warning sign. In the latter case, which may be accompanied by severe constant pain, the standard of care calls for diagnosis to determine if the surgical procedure insulted the IAN. A 3D cone beam X-ray provides the necessary data, but even before this step a prudent implantologist may back out or completely remove an implant in an effort to restore nerve function because delay is usually ineffective. Depending upon the evidence visible with a 3D X-ray, patients may be referred to a specialist in nerve repair. In all cases, speed in diagnosis and treatment are necessary.

[edit]Market

 

In the United States and the United Kingdom, there is no exclusive specialty in 'implantology'.

Any practitioner who carries out implant treatment, whether in the surgical insertion or the final provision of the prosthesis, must be adequately trained. Legal training requirements differ between countries.

In 2008, in the UK the General Dental Council (GDC) laid down strict training requirements[35] for dentists involved in dental implantology. Any dentist in the UK who wishes to train in the field of dental implantology must take part in an extended learning program which covers a detailed theory syllabus, as approved by the GDC,[36] in addition to formal supervised surgical training and mentoring. Dentists must not take part in implant dentistry in the UK until they have been approved by the training provider as having passed a formal competency assessment. Failure to comply with the GDC regulations may result in a dentist being removed from the Dental Register and hence losing the right to practice dentistry in the UK.[37]

[edit]See also

 

Periodontist

Oral and maxillofacial surgery

Bone grafts in Dental Implantology

Dental bridge

Osseointegration

Dental tourism

Gold teeth

American Association of Oral and Maxillofacial Surgeons

European Association for Osseointegration

British Society of Oral Implantology

[edit]References

 

^ Annali di Stomatologia - Su alcuni casi particolarmente interessanti di impianto endosseo con vite autofilettante - Vol XV - Aprile 1966

^ US patent 3579831, Stevens, Irving J.; Alexander, Jerry, "Bone Implant", granted 1971-05-25

^ Quirynen M, Van Assche N, Botticelli D, Berglundh T (2007). "How does the timing of implant placement to extraction affect outcome?". The International Journal of Oral & Maxillofacial Implants 22 Suppl: 203–23. PMID 18437797.

^ Crespi R, Capparé P, Gherlone E, Romanos GE (2008). "Immediate versus delayed loading of dental implants placed in fresh extraction sockets in the maxillary esthetic zone: a clinical comparative study". The International Journal of Oral & Maxillofacial Implants 23 (4): 753–8. PMID 18807574.

^ Gahlert M, Röhling S, Wieland M, Sprecher CM, Kniha H, Milz S (November 2009). "Osseointegration of zirconia and titanium dental implants: a histological and histomorphometrical study in the maxilla of pigs". Clinical Oral Implants Research 20 (11): 1247–53. doi:10.1111/j.1600-0501.2009.01734.x. PMID 19531104.

^ Depprich R, Zipprich H, Ommerborn M, et al. (2008). "Osseointegration of zirconia implants: an SEM observation of the bone-implant interface". Head & Face Medicine 4: 25. doi:10.1186/1746-160X-4-25. PMID 18990214.

^ Andreiotelli M, Kohal RJ (June 2009). "Fracture strength of zirconia implants after artificial aging". Clinical Implant Dentistry and Related Research 11 (2): 158–66. doi:10.1111/j.1708-8208.2008.00105.x. PMID 18657150.

^ Arturo N. Natali (ed.) (2003). "Dental Biomechanics". Taylor & Francis, London / New York, 273 pp., ISBN 9-780-415-30666-9, pp. 69-87.

^ Osseointegration, Zard et al. Quintessence 2009.[verification needed]

^ Palmer R (March 2007). "Ti-unite dental implant surface may be superior to machined surface in replacement of failed implants". The Journal of Evidence-based Dental Practice 7 (1): 8–9. doi:10.1016/j.jebdp.2006.12.001. PMID 17403502.

^ General Dental Council (October 30, 2008). "Doing implants? Make sure you’re up to scratch, warns GDC". Press release. Retrieved 2010-03-25.

^ Melo MD, McGann G, Obeid G (December 2007). "Survey of implant training in oral and maxillofacial surgery residency programs in the United States". Journal of Oral and Maxillofacial Surgery 65 (12): 2554–8. doi:10.1016/j.joms.2007.06.685. PMID 18022483.

 

^ Jokstad A (July 2008). "Where can I learn how to place dental implants? Perspectives from Scandinavia and Canada". International Journal of Oral and Maxillofacial Surgery 37 (7): 593–6. doi:10.1016/j.ijom.2007.12.009. PMID 18295450.

^ Addy LD, Lynch CD, Locke M, Watts A, Gilmour AS (December 2008). "The teaching of implant dentistry in undergraduate dental schools in the United Kingdom and Ireland". British Dental Journal 205 (11): 609–14. doi:10.1038/sj.bdj.2008.1027. PMID 19079107.

 

^ Binon PP (July 2007). "Treatment planning complications and surgical miscues". Journal of Oral and Maxillofacial Surgery 65 (7 Suppl 1): 73–92. doi:10.1016/j.joms.2007.03.014. PMID 17586352.

^ Brisman DL (1996). "The effect of speed, pressure, and time on bone temperature during the drilling of implant sites". The International Journal of Oral & Maxillofacial Implants 11 (1): 35–7. PMID 8820120.

^ Berdougo M, Fortin T, Blanchet E, Isidori M, Bosson JL (February 2009). "Flapless Implant Surgery Using an Image-Guided System. A 1- to 4-Year Retrospective Multicenter Comparative Clinical Study". Clinical Implant Dentistry and Related Research 12 (2): 142–52. doi:10.1111/j.1708-8208.2008.00146.x. PMID 19220842.

^ Becker W, Goldstein M, Becker BE, Sennerby L, Kois D, Hujoel P (February 2009). "Minimally invasive flapless implant placement: follow-up results from a multicenter study". Journal of Periodontology 80 (2): 347–52. doi:10.1902/jop.2009.080286. PMID 19186977.

^ Gerds TA, Vogeler M (December 2005). "Endpoints and survival analysis for successful osseointegration of dental implants". Statistical Methods in Medical Research 14 (6): 579–90. doi:10.1191/0962280205sm420oa. PMID 16355545.

^ Fischer K, Stenberg T, Hedin M, Sennerby L (May 2008). "Five-year results from a randomized, controlled trial on early and delayed loading of implants supporting full-arch prosthesis in the edentulous maxilla". Clinical Oral Implants Research 19 (5): 433–41. doi:10.1111/j.1600-0501.2007.01510.x. PMID 18371094.

^ Bhola M, Neely AL, Kolhatkar S (October 2008). "Immediate implant placement: clinical decisions, advantages, and disadvantages". Journal of Prosthodontics 17 (7): 576–81. doi:10.1111/j.1532-849X.2008.00359.x. PMID 18761580.

^ Spector L (October 2008). "Computer-aided dental implant planning". Dental Clinics of North America 52 (4): 761–75, vi. doi:10.1016/j.cden.2008.05.004. PMID 18805228.

^ Ludlow JB (November 2008). "Regarding 'Influence of CBCT exposure conditions on radiation dose'". Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics 106 (5): 627–8; author reply 628–9. doi:10.1016/j.tripleo.2008.06.031. PMID 18801676.

^ Viegas VN, Dutra V, Pagnoncelli RM, de Oliveira MG (January 2010). "Transference of virtual planning and planning over biomedical prototypes for dental implant placement using guided surgery". Clinical Oral Implants Research 21 (3): 290–5. doi:10.1111/j.1600-0501.2009.01833.x. PMID 20074239.

^ http://www.materialise.com/materialise/view/en/554529-SurgiGuide.html

^ Esposito M, Grusovin MG, Willings M, Coulthard P, Worthington HV (2007). "The effectiveness of immediate, early, and conventional loading of dental implants: a Cochrane systematic review of randomized controlled clinical trials". The International Journal of Oral & Maxillofacial Implants 22 (6): 893–904. PMID 18271370.

^ Albrektsson T, Zarb GA (1993). "Current interpretations of the osseointegrated response: clinical significance". The International Journal of Prosthodontics 6 (2): 95–105. PMID 8329101.

^ Fransson C, Wennström J, Tomasi C, Berglundh T (April 2009). "Extent of peri-implantitis-associated bone loss". Journal of Clinical Periodontology 36 (4): 357–63. doi:10.1111/j.1600-051X.2009.01375.x. PMID 19426183.

^ Pye AD, Lockhart DE, Dawson MP, Murray CA, Smith AJ (June 2009). "A review of dental implants and infection". The Journal of Hospital Infection 72 (2): 104–10. doi:10.1016/j.jhin.2009.02.010. PMID 19329223.

^ Mavrogenis AF, Dimitriou R, Parvizi J, Babis GC (2009). "Biology of implant osseointegration". Journal of Musculoskeletal & Neuronal Interactions 9 (2): 61–71. PMID 19516081.

^ Grant BT, Amenedo C, Freeman K, Kraut RA (February 2008). "Outcomes of placing dental implants in patients taking oral bisphosphonates: a review of 115 cases". Journal of Oral and Maxillofacial Surgery 66 (2): 223–30. doi:10.1016/j.joms.2007.09.019. PMID 18201600.

^ "Bisphosphonate medications and your oral health". Journal of the American Dental Association 137 (7): 1048. July 2006. PMID 16803833.

^ Cartsos VM, Zhu S, Zavras AI (January 2008). "Bisphosphonate use and the risk of adverse jaw outcomes: a medical claims study of 714,217 people". Journal of the American Dental Association 139 (1): 23–30. PMID 18167381.

^ McCoy G (2002). "Recognizing and managing parafunction in the reconstruction and maintenance of the oral implant patient". Implant Dentistry 11 (1): 19–27. PMID 11915541.

^ http://www.gdc-uk.org/Our+work/Education+and+quality+assurance/Policy+statement+on+implantology.htm

^ Training Standards in Implant Dentistry. The Royal College of Surgeons of England; London 2008[page needed]

^ Policy Statement on Implant Dentistry. The General Dental Council; London. 9th April 2008[page needed]

[edit]External links

 

 

This article's use of external links may not follow Wikipedia's policies or guidelines. Please improve this article by removing excessive and inappropriate external links or by converting links into footnote references. (February 2010)

OsseoNews Expert Discussions on Dental Implants

American Academy of Implant Dentistry

Academy of Osseointegration, professional association of implant dentists

ITI:International Team for Implantology, professional association of implant dentists

American Academy of Periodontology, dental implants guide

Association of Dental Implantology UK

Implant Dentistry

American Dental Implant Association

International Congress of Oral Implantologists

South African Society for Periodontology

Dental Implants Before and After

Journal of Implant and Advanced Clinical Dentistry

Journal of Dental Implantology

Encyclopedia about Dental Implants in Russian

Nelson S, Thomas G (May 2009). "Bacterial Persistence in Dentoalveolar Bone Following Extraction: A Microbiological Study and Implications for Dental Implant Treatment". Clinical Implant Dentistry and Related Research. doi:10.1111/j.1708-8208.2009.00165.x. PMID 19438939.

Website for determining implants from just a radiograph

[hide]

v • d • e

Dentistry

Recognized Specialties

(in the United States) 

Endodontics - Oral and Maxillofacial Pathology - Oral and Maxillofacial Radiology - Oral and Maxillofacial Surgery - Orthodontics and Dentofacial Orthopedics - Pediatric Dentistry - Periodontics - Prosthodontics - Dental public health

Unrecognized Specialties

(in the United States) 

Cosmetic Dentistry - Dental Implantology - Temporomandibular Joint Disorder - Geriatric dentistry - Restorative Dentistry - Forensic Odontology - Dental Traumatology

Procedures      

Dental extraction - Tooth filling - Root canal therapy - Root end surgery - Scaling and root planing - Teeth cleaning -Tooth bonding - Tooth polishing - Tooth bleaching

See also          

List of oral health and dental topics - List of basic dentistry topics - Oral hygiene - Dental instruments - Restorative materials

M: TTH

anat/devp/phys

noco/cong/jaws/tumr, epon, injr

dent, proc (orth, pros, endo)

Categories: Dentistry | Implants | Restorative dentistry | Prosthetics | Oral surgery | Oral and maxillofacial surgery | Medical technology

 

Comments (338)

cosmetic dentistry

Cosmetic dentistry

From Wikipedia, the free encyclopedia

 

This article is written like an advertisement. Please help rewrite this article from a neutral point of view. For blatant advertising that would require a fundamental rewrite to become encyclopedic, use {{db-spam}} to mark for speedy deletion. (September 2010)

The meaning of Cosmetic It is probably helpful, at this point, to point out that the term 'cosmetic', while it is in common use in dentistry, actually has a specific meaning. The word is derived from the Greek 'cosmetikos' meaning adornment and, strictly speaking, should be used in relationship to things that are temporary, superficial and readily reversible. Cosmetics do not alter the material on which they are placed. They have to be replaced every time one wants a particular look. Cosmetics do not damage the underlying structure on which they are placed. 'Cosmetic' would usually relate to something like lipstick or eye shadow which will temporarily alter the area on which the cosmetic is placed. Such 'cosmetics' do not adhere to the underlying tissue and if one doesn't like the appearance, it is easy to remove the cosmetic and replace it with something that is more acceptable. There is a huge lucrative international cosmetic industry founded on this principle, much of which preys on some people's vanities, self image and insecurities.

Cosmetic dentistry is dental work that improves the appearance and function of a person's teeth. The American Dental Association does not recognize cosmetic dentistry as a formal specialty area of dentistry.[1][2] This has been misunderstood by many general dentists; there is no restriction on a dentist saying that he or she is a cosmetic dentist.[3]

Fashions and 'aesthetic dentistry'

The provision of aesthetic dentistry is to improve the beauty of the teeth, the smile, or the face as perceived by the patient. There is nothing more controversial in dentistry than what constitutes a beautiful smile. If you were to ask ten dentists to look at a patient's teeth and ask for their comments about the dental appearance, you will get eleven different opinions. These will range from the dentists who like the 'natural look' to dentists who prefer the 'false teeth' look. As in most areas of life there are fashions. Fashions come and go. In the early years of this century, i.e. from the year 2000 to the present time, there has been an American dominated 'All Teeth and Have a Nice Day' look. This has led to the provision of ultra white, very even and very big teeth. The whiteness of the teeth and their graduated size and regularity extending widely and backwards have the effect of making the teeth and mouth a very dominant part of the face. This look has been popularised by various actresses, models and minor celebrities.

Very few of these actresses, celebrities or models would be candidates for Mensa and some people would call them 'airheads'. However, many gullible, younger people worship their celebrity status, money and lifestyle. There has been a rise in acceptance of the views of such 'airheads'. Airheads are superficial and self absorbed. They are not concerned about themselves in the future and want provision of 'The Look' here and now. Many of the images appearing in glossy magazines which target young people are of airbrushed models that are heavily made up and the images are 'cropped and improved' by various bits of computer technology before appearing in these magazines. This is likely to produce unrealistic expectations in younger people who, as a consequence, seek elective aesthetic or 'cosmetic dentistry'.

However, unlike changing someone's hair or the colour of their skin with cosmetics or tanning (either by real sun or fake tan with various chemicals) the provision of dentistry for such patients is often a much more complex, irreversible and dangerous process. The promotion of such dentistry requires a very delicate balance between improving the patient's appearance and avoiding doing inappropriate and unnecessary biologic damage to the teeth, especially when such treatment is viewed in the much longer term.

Contents [hide]

1 Fields

1.1 General dentistry

1.2 Prosthodontics

1.3 Orthodontics

2 Common cosmetic dental treatment options

3 Materials

4 Credentialing

4.1 American Academy of Cosmetic Dentistry

4.2 American Society For Dental Aesthetics

5 See also

6 References

[edit]Fields

 

[edit]General dentistry

Many general dentists refer to themselves as "cosmetic dentists" regardless of their specific education, training and experience in this field. In addition, there are certain ADA recognized specialty areas, most notable Prosthodontics and Orthodontics, which are distinct disciplines from cosmetic dentistry but which may overlap with some aspects of cosmetic dentistry.

[edit]Prosthodontics

According to the ADA, prosthodontics is the dental specialty pertaining to the diagnosis, treatment planning, rehabilitation and maintenance of the oral function, comfort, appearance and health of patients with clinical conditions associated with missing or deficient teeth and/or oral and maxillofacial tissues using biocompatible substitutes. (Adopted April 2003) Prosthodontics[4] and dentists who have these additional 3 years of training are called Prosthodontists.

[edit]Orthodontics

According to the ADA, orthodontics is the dental specialty that includes the diagnosis, prevention, interception, and correction of malocclusion, as well as neuromuscular and skeletal abnormalities of the developing or mature orofacial structures. (Adopted April 2003) Orthodontics[4] and dentists who have these additional 3 years of training are called Orthodontists.

[edit]Common cosmetic dental treatment options

 

Whitening, or "tooth bleaching", is the most common cosmetic dental procedure. While many whitening options are now available, including over the counter products, dentist-supervised treatments remain the recommended procedures for lightening discolored teeth.[citation needed]

Enamel shaping removes parts of the contouring enamel to improve the appearance of the tooth. It may be used to correct a very small chip. The removed enamel is irreplaceable, and may sometimes expose dentin. It is also known as enameloplasty, odontoplasty, recontouring, reshaping, slenderizing and stripping.[citation needed]

Contouring, also known as tooth reshaping, is one of few instant treatments now available in cosmetic dentistry. Dental reshaping and contouring is a procedure to correct crooked teeth, chipped teeth, cracked teeth or even overlapping teeth in just one session. The dental contouring procedure can even be a substitute for braces under certain circumstances. It is also a procedure of subtle changes. A few millimeters of reduction and a few millimeters of tooth-colored laminate is involved. Tooth reshaping, or dental contouring, is commonly used to alter the length, shape or position of teeth.[citation needed]

Bonding is a process in which an enamel-like dental composite material is applied to a tooth's surface, sculpted into shape, hardened and then polished.[citation needed]

Dental bridges are false teeth, known as a pontics, which are fused between two porcelain crowns to fill in the area left by a missing tooth. The two crowns holding it in place that are attached onto your teeth on each side of the false tooth. This is known as a fixed bridge. This procedure is used to replace one or more missing teeth. Fixed bridges cannot be taken out of your mouth as you might do with removable partial dentures. In areas of your mouth that are under less stress, such as your front teeth, a cantilever bridge may be used. Cantilever bridges are used when there are teeth on only one side of the open space. Bridges can reduce your risk of gum disease, help correct some bite issues and even improve your speech. Bridges require your commitment to serious oral hygiene, but will last as many as ten years or more.

Veneers are ultra-thin, custom-made porcelain laminates that are bonded directly to the teeth. They are an option for closing gaps or disguising discolored teeth that do not respond well to whitening procedures. Depending on the procedure, tooth reduction may be necessary.[5][6]

Gum lift is a cosmetic dental procedure that raises and sculpts the gum line. The procedure involves reshaping the tissue and/or underlying bones to create the appearance of longer or more symmetrical teeth.[citation needed]

[edit]Materials

 

In the past, dental fillings and other tooth restorations were made of gold, amalgam and other metals—some of which were veneered with porcelain. Now, dental work can be made entirely of porcelain or composite materials that more closely mimic the appearance of natural tooth structure. These tooth colored materials are bonded to the underlying tooth structure with resin adhesives. Unlike silver fillings (amalgams) they are entirely free of mercury. Many dentists offer procedures to be cosmetic and because their patients prefer natural looking teeth.[citation needed]

[edit]Credentialing

 

[edit]American Academy of Cosmetic Dentistry

The American Academy of Cosmetic Dentistry (AACD) is the largest international dental organization in the world, composed of general dentists, specialists, and lab technicians focused on the art and science of cosmetic dentistry. Founded in 1984, the AACD has over 7,000 members in the United States and more than 70 countries around the globe. Members of the Academy include cosmetic and reconstructive dentists, dental laboratory technicians, educators, researchers, students, hygienists, corporations and dental auxiliaries. AACD members seek out continuing education through lectures, workshops, and publications in order to keep up-to-date with all of the advancements in cosmetic dental techniques and technology. In 1984, the AACD was formed and has filled the dire need for credentialing in cosmetic dentistry. The purpose of the American Board of Cosmetic Dentistry (ABCD) is the testing, analyzing, and evaluation of the services of dentists and laboratory technicians for the purpose of awarding AACD Accreditation in cosmetic dentistry.[7]

[edit]American Society For Dental Aesthetics

Conceived in 1976, the American Society for Dental Aesthetics was developed with a single purpose in mind: continuing dental education to teach dental health professionals the most advanced aesthetic and restorative techniques available. To become a member of the ASDA, a dentist must show a minimum of five years in dental practice, or postgraduate training of two years in an approved program; attendance to at least two ASDA sponsored continuing dental education seminars; nomination by a member accompanied by two letters of recommendation by Society members; presentation of five (5) cases illustrating the concepts of aesthetic dentistry.[8]

 

dental crown

Crown (dentistry)

From Wikipedia, the free encyclopedia

  (Redirected from Dental crown)

 

 

A porcelain-fused-to-metal crown for tooth #45 on its stone model. It is now ready to be cemented into the patient's mouth. The prosthetic crown does not extend distally to tooth #47 (molar to the left in photo) because the span is too large, as tooth #46 is missing. This edentulous area, together with a much larger one across the arch in the area of teeth #37-34, will be restored with a removable partial denture.

 

 

The stone model die for the same PFM crown on tooth #45. Notice how much tooth structure has been removed in order to facilitate placement of a crown. The original dimensions of the tooth approach if not duplicate the contours of the restoration in the photo above. The silvery paint on the stone die of tooth #45 is a die spacer, placed to allow for a minute amount of space between the tooth structure and the internal surface of the crown, which will later fill with cement upon final insertion of the crown into the mouth.

A crown is a type of dental restoration which completely caps or encircles a tooth or dental implant. Crowns are often needed when a large cavity threatens the ongoing health of a tooth[1] (usually caused by not brushing one's teeth well enough[2]). They are typically bonded to the tooth using a dental cement. Crowns can be made from many materials, which are usually fabricated using indirect methods. Crowns are often used to improve the strength or appearance of teeth. While unarguably beneficial to dental health, the procedure and materials can be relatively expensive[3].

The most common method of crowning a tooth involves using a dental impression of a prepared tooth by a dentist to fabricate the crown outside of the mouth. The crown can then be inserted at a subsequent dental appointment. Using this indirect method of tooth restoration allows use of strong restorative materials requiring time consuming fabrication methods requiring intense heat, such as casting metal or firing porcelain which would not be possible to complete inside the mouth. Because of the expansion properties, the relatively similar material costs, and the aesthetic benefits, many patients choose to have their crown fabricated with gold[4].

As new technology and materials science has evolved, computers are increasingly becoming a part of crown and bridge fabrication, such as in CAD/CAM Dentistry.

Contents [hide]

1 Other reasons to restore with a crown

1.1 Implants

1.2 Endodontically treated teeth

1.3 Surveyed crown

1.4 Aesthetics

2 Tooth preparation

2.1 Dimensions of preparation

2.2 Taper

2.3 Margin

2.4 Ferrule effect

3 Adequate and appropriate restoration of tooth structure

4 3/4 and 7/8 crowns

5 All-ceramic restorations

6 Longevity

7 Advantages and disadvantages

8 Types and materials

8.1 Metal-containing restorations

8.1.1 Full gold crown

8.2 Porcelain-fused-to-metal crowns

8.3 Restorations without Metal

8.3.1 Chairside CAD/CAM Dentistry

8.3.2 Empress

8.3.3 In-ceram

8.3.4 Procera

9 See also

10 References

11 External links

[edit]Other reasons to restore with a crown

 

There are additional situations in which a crown would be the restoration of choice.

[edit]Implants

Dental implants are placed into either the maxilla or mandible as an alternative to partial or complete edentulism. Once placed and properly integrated into the bone, implants may then be fitted with a number of different prostheses:

crowns or bridges

precision attachments for either removable partial dentures, complete dentures or a hybrid sort of prosthetic appliance.

[edit]Endodontically treated teeth

When teeth undergo endodontic treatment, or root canal therapy, they are devitalized when the nerve and blood supply are cut off and the space which they previously filled, known as the "pulp chamber" and "root canal", are thoroughly cleansed and filled with various materials to prevent future invasion by bacteria. Although there may very well be enough tooth structure remaining after root canal therapy is provided for a particular tooth to restore the tooth with an intracoronal restoration, this is not suggested in most teeth. The vitality of a tooth is remarkable in its ability to provide the tooth with the strength and durability it needs to function in mastication. The living tooth structure is surprisingly resilient and can sustain considerable abuse without fracturing. Consequently, after root canal therapy is performed, a tooth becomes extremely brittle and is significantly weaker than its vital neighbors.

 

 

Fractures of endodontically treated teeth increase considerably in the posterior dentition when cuspal protection is not provided by a crown.[5]

The average person can exert 150-200 lbs. of muscular force on their posterior teeth, which is approximately nine times the amount of force that can be exerted in the anterior. If the effective posterior contact area on a restoration is .1 mm², over 1 million PSI of stress is placed on the restoration. Therefore, posterior teeth (i.e. molars and premolars) should in almost all situations be crowned after undergoing root canal therapy to provide for proper protection against fracture (mandibular premolars, being very similar in crown morphology to canines, may in some cases be protected with intracoronal restorations). Should an endodontically treated tooth not be properly protected, there is a chance of it succumbing to breakage from normal functional forces. This fracture may well be difficult to treat, such as a "vertical root fracture" . Anterior teeth (i.e. incisors and canines), which are exposed to significantly lower functional forces, may effectively be treated with intracoronal restorations following root canal therapy if there is enough tooth structure remaining after the procedure.

[edit]Surveyed crown

Another situation in which a crown is the restoration of choice is when a tooth is intended as an abutment tooth for a removable partial denture, but is initially unfavorable for such a task. If the abutment teeth onto which the RPD is supposed to clasp do not possess the proper dimensions or features required, these aspects can be built into what is known as a surveyed crown.

[edit]Aesthetics

A fourth situation in which a crown would be the restoration of choice is when a patient desires to have his or her smile aesthetically improved but when partial coverage (i.e., a veneer/laminate) is not an option for one or more reasons. If the patient's occlusion does not permit for a mildly-retentive restoration, or if there is too much decay or a fracture within the tooth structure, a porcelain or composite veneer may not be placed with any adequate guarantee for its durability. Similarly, a "bruxer" (someone who clenches or grinds their teeth) may produce enough force to repeatedly dislodge or irreversibly abrade any veneer a dentist can plan for. In such a case, full coverage crowns can alter the size, shape or shade of a patient's teeth while protecting against failure of the restoration.

Makeover shows such as Extreme Makeover make extensive use of crowns, as the time-frame of the makeover is too short to allow up to 18 months for orthodontic treatment for problems that might otherwise be corrected more conservatively.

[edit]Tooth preparation

 

 

 

A full-arch vinylpolysiloxane impression of the teeth prepared for the 5-unit PFM bridge shown in the photographs below. The salmon-colored impression material used near the crown preparations is of a lower viscosity than the blue, allowing for the capture of greater detail.

Preparation of a tooth for a crown involves the irreversible removal of a significant amount of tooth structure. All restorations possess compromised structural and functional integrity when compared to healthy, natural tooth structure. Thus, if not indicated as desirable by an oral health-care professional, the crowning of a tooth would most likely be contraindicated. It should be evident, though, that dentists trained at different institutions in different eras and in different countries might very well possess different methods of treatment planning and case selection, resulting in somewhat diverse recommendations for treatment.

Traditionally more than one visit is required to complete crown and bridge work, and the additional time required for the procedure can be a disadvantage; the increased benefits of such a restoration, however, will generally offset these considerations.

[edit]Dimensions of preparation

When preparing a tooth for a traditional crown, the enamel may be totally removed and the finished preparation should, thus, exist primarily in dentin. As elaborated on below, the amount of tooth structure required to be removed will depend on the material(s) being used to restore the tooth. If the tooth is to be restored with a full gold crown, the restoration need only be .5 mm in thickness (as gold is very strong), and therefore, a minimum of only .5 mm of space needs to be made for the crown to be placed. If porcelain is to be applied to the gold crown, an additional minimum of 1 mm of tooth structure needs to be removed to allow for a sufficient thickness of the porcelain to be applied, thus bringing the total tooth reduction to minimally 1.5 mm.

If there is not enough tooth structure to properly retain the traditional prosthetic crown, the tooth requires a build-up material. This can be accomplished with a pin-retained direct restoration, such as amalgam or a composite resin, or in more severe cases, may require a post and core. Should the tooth require a post and core, endodontic therapy would then be indicated, as the post descends into the devitalized root canal for added retention. If the tooth, because of its relative lack of exposed tooth structure, also requires crown lengthening, the total combined time, effort and cost of the various procedures, together with the decreased prognosis because of the combined inherent failure rates of each procedure, might make it more reasonable to have the tooth extracted and opt to have an implant placed.

In recent years, the technological advances afforded by CAD/CAM Dentistry offer viable alternatives to the traditional crown restoration in many cases. [6][7] Where the traditional indirectly fabricated crown requires a tremendous amount of surface area to retain the normal crown, potentially resulting in the loss of healthy, natural tooth structure for this purpose, the all-porcelain CAD/CAM crown can be predictably used with significantly less surface area. As a matter of fact, the more enamel that is retained, the greater the likelihood of a successful outcome. As long as the thickness of porcelain on the top, chewing portion of the crown is 1.5mm thick or greater, the restoration can be expected to be successful. The side walls which are normally totally sacrificed in the traditional crown are generally left far more intact with the CAD/CAM option. In regards to post & core buildups, these are generally contraindicated in CAD/CAM crowns as the resin bonding materials do best bonding the etched porcelain interface to the etched enamel/dentin interfaces of the natural tooth itself. The crownlay is also an excellent alternative to the post & core buildup when restoring a root canal treated tooth.

[edit]Taper

The prepared tooth also needs to possess 3 to 5 degrees of taper to allow for the restoration to be properly placed on the tooth. The taper should not exceed 20 degrees. Fundamentally, there can be no undercuts on the surface of the prepared tooth, as the restoration will not be able to be removed from the die, let alone fit on the tooth (see explanation of lost-wax technique below to understand of the processes involved in crown fabrication). At the same time, too much taper will severely limit the grip that the crown has on the prepared tooth, thus contributing to failure of the restoration. Generally, 6º of taper around the entire circumference of the prepared tooth, giving a combined taper of 12º at any given sagittal section through the prepared tooth, is appropriate to both allow the crown to fit yet provide enough grip.

[edit]Margin

The most coronal position of untouched tooth structure (that is, the continual line of original, undrilled tooth structure at or near the gum line) is referred to as the margin. This margin will be the future continual line of tooth-to-restoration contact, and should be a smooth, well-defined delineation so that the restoration, no matter how it is fabricated, can be properly adapted and not allow for any openings visible to the naked eye, however slight. An acceptable distance from tooth margin to restoration margin is anywhere from 40-100 μm[citation needed]. However, the R.V. Tucker method of gold inlay and onlay restoration produces tooth-to-restoration adaptation of potentially only 2 μm[citation needed], confirmed by scanning electron microscopy; this is less than the diameter of a single bacterium.

Naturally, the tooth-to-restoration margin is an unsightly thing to have exposed on the visible surface of a tooth when the tooth exists in the aesthetic zone of the smile. In these areas, the dentist would like to place the margin as far apical (towards the root tip of the tooth) as possible, even below the gum line. While there is no issue, per se, with placing the margin at the gumline, problems may arise when placing the margin too subgingivally (below the gumline). First, there might be issues in terms of capturing the margin in an impression to make the stone model of the prepared tooth (see stone model replication of tooth in photographs, above). Secondly, there is the seriously important issue of biologic width. Biologic width is the mandatory distance to be left between the height of the alveolar bone and the margin of the restoration, and if this distance is violated because the margin is placed too subgingivally, serious repercussions may follow. In situations where the margin cannot be placed apically enough to provide for proper retention of the prosthetic crown on the prepared tooth structure, the tooth or teeth involved should undergo a crown lengthening procedure.

 

 

The natural tooth's crown (A) meets the root (B) at the cementoenamel junction, and it is roughly at this point that the gingival attachment begins at the base of the gingival sulcus (G). The margin of the prosthetic crown may not violate the 2 mm of biologic width from the base of this sulcus to the height of the alveolar bone (C) if complications are to be avoided.

There are a number of different types of margins that can be placed for restoration with a crown. There is the chamfer, which is popular with full gold restorations, which effectively removed the smallest amount of tooth structure. There is also a shoulder, which, while removing slightly more tooth structure, serves to allow for a thickness of the restoration material, necessary when applying porcelain to a PFM coping or when restoring with an all-ceramic crown (see below for elaboration on various types of crowns and their materials). When using a shoulder preparation, the dentist is urged to add a bevel; the shoulder-bevel margin serves to effectively decrease the tooth-to-restoration distance upon final cementation of the restoration.

[edit]Ferrule effect

A very important consideration when restoring with a crown is the incorporation of the ferrule effect. As with the bristles of a broom, which are grasped by a ferrule when attached to the broomstick, the crown should envelop a certain height of tooth structure to properly protect the tooth from fracture after being prepared for a crown. This has been established through multiple experiments as a mandatory continuous circumferential height of 2 mm; any less provides for a significantly higher failure rate of endodontically-treated crown-restored teeth. When a tooth is not endodontically treated, the remaining tooth structure will invariably provide the 2 mm height necessary for a ferrule, but endodontically treated teeth are notoriously decayed and are often missing significant solid tooth structure. Because they are weaker after the additional removal of tooth structure that occurs during a root canal procedure, endodontically treated teeth require proper protection against vertical root fracture. Contrary to what some dentists believe, a bevel is not at all suitable for implementing the ferrule effect, and beveled tooth structure may not be included in the 2 mms of required tooth structure for a ferrule. Some have speculated that a shoulder preparation on an all ceramic crown that will be bonded in place may have the same effect as a ferrule.

[edit]Adequate and appropriate restoration of tooth structure

 

As crowns are fabricated indirectly (outside of the mouth) free of the encumbrances of saliva, blood, and tight quarters, they can be made to fit more precisely than restorative materials placed directly (inside the mouth). In regards to marginal adaptations (the circumferential seal which keeps bacteria out), anatomically correct contacts (touching adjacent teeth properly so food will not be retained), and proper morphology, the indirect fabrication of the restorations are unprecedented. Indirectly fabricated crowns may be fabricated one of two ways. In the traditional sense, the tooth in question is prepared, a mold is taken, a temporary crown is placed and then the patient leaves. The mold is then sent to a dental laboratory whereby a model is constructed from the mold, and a crown is created on the model (usually out of porcelain, gold, or porcelain fused to metal) to replace the missing tooth structure. The patient returns to the dental office a week or two later and then the temporary is removed and the crown is fitted and cemented in place. Alternatively, a crown may be indirectly fabricated utilizing technology and techniques relating to CAD/CAM Dentistry, whereby the tooth is prepared and computer software is used to create a virtual restoration which is milled on the spot and bonded permanently in place an hour or two later.

[edit]3/4 and 7/8 crowns

 

There are even restorations that fall between an onlay and a full crown when it comes to preservation of natural tooth structure. In the past, it was somewhat common to find dentists who prepared teeth for 3/4 and 7/8 crowns. Such restorations would generally be fabricated for maxillary second premolars or first molars, which might only be slightly visible when a patient smiled. Thus, the dentist would preserve healthy natural tooth structure that existed on the mesiobuccal corner of the tooth for aesthetic purposes, the remainder of the tooth would be enclosed in restorative material. Even when porcelain-fused-to-metal and all-ceramic crowns were developed, preserving any amount of tooth structure adds to the overall strength of the tooth. As one can imagine, though, those dentists who took issue with the increased marginal length of the onlay restoration would surely take issue with the purported advantages of increased remaining tooth structure when it translated into the enormously increased marginal length of a 3/4 or 7/8 crown.

[edit]All-ceramic restorations

 

 

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Inlays, onlays, porcelain veneers, crownlays and all varieties of crowns can also be fabricated out of ceramic materials, such as in CAD/CAM Dentistry or traditionally in a dental laboratory setting. CAD/CAM technology can allow for the immediate, same day delivery of these types restorations which are milled out of blocks of solid porcelain which matches the shade or color of the patients teeth. Traditionally, all-ceramic restorations have been made off site in a dental laboratory either out of feldspathic porcelains or pressed ceramics. This indirect method of fabrication involves molds and temporaries, but can yield quite beautiful end-results if communication between the laboratory and the dentist is sound. The greatest difference between these two differing modalities lies in the fact that the CAD/CAM route does not require temporization, while the laboratory-fabricated route does. Some argue that this lack of temporization can result in a decreased need for root canal therapy, as there is no temporary leakage between visits.

Restorations that are all-ceramic require wide shoulder margins and reductions of at least 1.0 - 1.5 mm across the occlusal (chewing) surfaces of the teeth. There are times where this reduction would be considered excessive, just as there are times when previous restorations or pathology require this much removal or more. Arguments against using all-ceramic restorations include a greater chance of fracture, when little to no enamel remains for proper adhesive bonding, or potentially when the patient clenches or grinds their teeth ("bruxes") excessively. Indications for using all-ceramic restorations include more aesthetic results, when metal compatibility issues exist, and when removal of less tooth structure is desired. All-ceramic restorations do not require resistance and retention form and consequently less surface area need be removed and the restoration will still stay in place by virtue of micromechanical and chemical bonding.

Ceramic materials such as lithium disilicate dental ceramics have recently been developed which provide greater strength and life-expectancy of dental restorations.

[edit]Longevity

 

Although no dental restoration lasts forever, the average lifespan of a crown is around 10 years. While this is considered comparatively favorable to direct restorations, they can actually last up to the life of the patient (50 years or more) with proper care. One reason why a 10 year mark is given is because a dentist can usually provide patients with this number and be confident that a crown that the dental lab makes will last at least this long. It should be noted that many dental insurance plans in North America will allow for a crown to be replaced after only five years.

The most important factor affecting the lifespan of any restorative is the continuing oral hygiene performed by the patient. With crowns, as with most things, a poorly-made object can last well past its predicted lifetime if it is properly cared for, and even a well-made item can last only a day if handled improperly. Other factors depend on the skill of the dentist and their lab technician, the material used and appropriate treatment planning and case selection.

Full gold crowns last the longest, as they are fabricated as a single piece of gold. PFMs, or porcelain-fused-to-metal crowns possess an additional dimension in which they are prone to failure, as they incorporate brittle porcelain into their structure. Although incredibly strong in compression, porcelain is terribly fragile in tension, and fracture of the porcelain increased the risk of failure, which rises as the amount of surfaces covered with porcelain is increased. A traditional PFM with occlusal porcelain (i.e. porcelain applied to the biting surface of a posterior tooth) has a 7% higher chance of failure per year than a corresponding full gold crown.

When crowns are used to restore endodontically treated teeth, they increase the life of the tooth not only by preventing fracture of the brittle devitalized tooth but also by providing a better seal against invading bacteria. Although the inert filling material within the root canal blocks against microbial invasion of the internal tooth structure, it is actually a superior coronal seal, or marginal adaptation of the restoration in or on the crown of the tooth, which prevents reinvasion of the root canal.

[edit]Advantages and disadvantages

 

 

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Whenever considering any irreversible process, especially in the field of surgery, one must conduct a thorough cost-benefit analysis.

The main disadvantages of restoration with a crown are extensive irreversible tooth preparation (grinding away) and higher costs than for direct restorations such as amalgam or Dental composite. The benefits, as described above, include long-term durability and evidence-based success as compared to other restorations or no treatment. The crowning of two fairly large molars to sling a bridge between them for a missing tooth is a costly and sometimes oversold procedure.The increased food and bacteria trapping of the underside of the bridge often offsets the benefits of the bridge element in maintaining the positions of the opposing teeth and the loss of the ease of use and mouth feel of two big natural teeth.

It is important to bear in mind that it is usually the damage to a tooth that dictates the need for a crown, and alternative treatments are usually less effective. However, it is also important to realise that even if risks and benefits are objectively analysed, their significance depends on the priorities of the patient. An example of this occurs when a patient would like to restore an edentulous area between healthy adjacent teeth. Before implants, there were three options:

Fixed partial denture (bridge)

Removable partial denture

No treatment

Those who could afford it were usually told by their dentists that a bridge was their best choice, because it is much sturdier than removable dentures and requires less looking after. When implants became available, however, they were recommended as the best possible treatment, because the virgin teeth adjacent to the edentulous area no longer needed to be cut in order to fit the bridge. The affluent are thus told that a fixed partial denture is no longer desirable, now that implants are available. However, implants are significantly more expensive than a bridge, and the results are generally much less immediate.

[edit]Types and materials

 

 

 

In order to determine the shade for the future crowns, the shade of adjacent teeth are matched to preformed shade guides. Here, the shade is determined to match best with B1. (The two maxillary central incisors have already been cut down and prepared for crowns.)

There are many different methods of crown fabrication, each using a different material. Some methods are quite similar, and utilize either very similar or identical materials.

[edit]Metal-containing restorations

[edit]Full gold crown

Full gold crowns (FGCs) consist entirely of a single piece of alloy. Although referred to as a gold crown, this type of crown is actually composed of many different types of elements, including but not limited to gold, platinum, palladium, silver, copper and tin. The first three elements listed are noble metals, while the last three listed are base metals. Full gold crowns are of better quality when they are high in noble content. According to the American Dental Association, full gold crown alloys can only be labeled as high noble when they contain at least 60% noble metal, of which at least 40% must be gold.

Full gold crowns are cast metal restorations that are made using the lost-wax technique. After the dentist prepares a tooth for a crown, he or she will take an impression of the prepared tooth, the adjacent teeth in the same arch and the opposing teeth in the opposing arch. With all of the necessary boundaries of the future cast crown defined in three dimensions within the impression material (i.e. the necessary height, width and depth of the crown is now recorded in impression material), the impression(s) are sent to a dental laboratory where they will be poured up in various types of dental stone or plaster. After the stone models are formed, they are ditched, died and articulated so that the laboratory technician can see how the two arches meet and properly access the tooth replicates to perform his tasks. (See photographs at the beginning of the article to see the stone model dies and the completed crown on the die.) The lab technician will then apply wax to the die (analog of the prepared tooth) and manipulate and craft the wax until he or she has built it up into what appears like and conforms to the specific dimensions of the tooth being restored. Prior to applying the wax, though, a die spacer is applied to the die. This is a thin coat of material that is painted onto the die to provide a space between the gold crown and the actual tooth structure to be filled with cement upon final cementation. A lubricant is also applied so that the wax pattern, as the wax-up of the crown is referred to, can be easily removed when completed.

The wax pattern is removed from the die and invested in a sort of plaster while connected to a short plastic stick, called a "sprue former", which will stick out of the investing plaster. The investment, as it is called now, is placed in a furnace, which will completely burn off the wax and plastic that formed the wax pattern/sprue complex. What is left is a hollow within the investment material, known as an "investment pattern". Because the sprue former stuck out a little bit from the investment material, there is a communication between the outside and the investment pattern. The investment pattern is then placed in a sort of simple centrifuge where pennyweights of gold are melted down and rapidly shot through the communication in the investment pattern, through the sprue that was formed by the sprue former, and into the hollow that used to be inhabited by the wax pattern of the crown waxed-up by the technician, thus called the lost-wax technique. After properly cooling, the single piece crown-and-sprue of gold is sectioned, and the sprue can be recycled in another casting. The crown is touched-up in the location of the sprue attachment, finished and polished to a high shine, and delivered to the dentist so that he or she can try it in the mouth, make certain it has all of the proper contacts with the adjacent and opposing teeth, and cement it to the prepared tooth.

[edit]Porcelain-fused-to-metal crowns

Porcelain-fused-to-metal dental crowns (PFMs) have a metal shell on which is fused a veneer of porcelain in a high heat oven. The metal provides strong compression and tensile strength, and the porcelain gives the crown a white tooth-like appearance, suitable for front teeth restorations. These crowns are often made with a partial veneer that covers only the aspects of the crown that are visible. The remaining surfaces of the crown are bare metal. A variety of metal alloys containing precious metals and base metals can be used. The porcelain can be color matched to the adjacent teeth.

[edit]Restorations without Metal

[edit]Chairside CAD/CAM Dentistry

The CAD/CAM method of fabricating all-ceramic restorations is by electronically capturing and storing a photographic image of the prepared tooth and, using computer technology, crafting a 3D restoration design that conforms to all the necessary specifications of the proposed inlay, onlay or single-unit crown; there is no impression. After selecting the proper features and making various decisions on the computerized model, the dentist directs the computer to send the information to a local milling machine. This machine will then use its specially designed diamond burs to mill the restoration from a solid ingot of a ceramic of pre-determined shade to match the patient's tooth. After about 20 minutes, the restoration is complete, and the dentist sections it from the remainder of the unmilled ingot and tries it in the mouth. If the restoration fits well, the dentist can cement the restoration immediately. A dental CAD/CAM machine costs roughly $100,000, with continued purchase of ceramic ingots and milling burs.

Typically, over 95% of the restorations made using Dental CAD/CAM and Vita Mark I and Mark II blocks are still clinically successful after 5 years.[8] [9] Further, at least 90% of restorations still function successfully after 10 years.[8] [9] Advantages of the Mark II blocks over ceramic blocks include: they wear down as fast as natural teeth,[10] [9], their failure loads are very similar to those of natural teeth, [11] [9] and the wear pattern of Mark II against enamel is similar to that of enamel against enamel.[12] [13] [9]

[edit]Empress

The Empress system is superficially similar to a lost-wax technique in that a hollow investment pattern is made, but the similarities stop there. A specially designed pressure-injected leucite-reinforced ceramic is then pressed into the mold by using a pressable-porcelain-oven, as though the final all-ceramic restoration has been "cast." The Empress can be utilized for anything the lost-wax technique can be used for, in addition to veneers (which would not be made of cast metal).

[edit]In-ceram

Introduced in 1989, In-ceram, by Vita, infused the fragile new "all-ceramic crown" with glass to produce what was then thought to be a superior product.

[edit]Procera

Procera AllCeram, owned by Nobel Biocare, is a CAD/CAM based method which produces a crown by overlaying a very durable ceramic coping of either alumina or zirconia, referred to as a "core", with Vitadur Alpha porcelain. Introduced in 1991, Procera can now be used to produce crowns, bridges and veneers.

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