Glossary: Dental Implants
A dental implant is used in prosthetic dentistry. There are several types. The most widely accepted and successful is the osseointegrated implant, based on the discovery by Professor Br?nemark that titanium could be successfully incorporated into bone when osteoblasts grow on and into the rough surface of the implanted titanium. This forms a structural and functional connection between the living bone and the implant. A typical implant consists of a titanium screw, with a roughened surface. This surface is treated either by plasma spraying, etching or sandblasting to increase the integration potential of the implant. At jaw sites where no prior tooth has existed for many months, a pilot hole is bored into the recipient bone, taking care to avoid vital structures (in particular the inferior alveolar nerve within the mandible). This pilot hole is then expanded by using progressively wider drills. Care is taken not to damage the osteoblast cells by overheating. A cooling saline spray keeps the temperature of the bone to below 47 degrees Celsius. The implant screw is usually self-tapping and is screwed into place at a precise torque so as not to overload the surrounding bone. Once in the bone, a cover screw is placed and the operation site is allowed to heal for a few months for integration to occur. After some months the implant is uncovered and a healing abutment and temporary crown is placed onto the implant. This encourages the gum to grow in the right scalloped shape to approximate a natural tooth's gums and allows assessment of the final aesthetics of the restored tooth. Once this has occurred a permanent crown will be constructed and placed on the implant. 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 of the treatment time and in some cases a prosthetic can be attached to the implants at the same time as the surgery to place the dental implants. Typically in the United Kingdom a single tooth implant plus crown costs around ?2000 or about $3500 USD in the United States. Full mouth reconstructions with dental implants can start around $12,000 per arch and can approach $50,000 per arch depending on the complexity of the case. A variation on the implant procedure is the implant-supported bridge, or implant-supported denture.
Failure of a dental implant is usually related to failure to osseointegrate correctly. A dental implant is considered to be a failure if it is lost, mobile or shows peri-implant bone loss of greater than one mm in the first year after implanting and greater than 0.2mm a year after that. Dental implants are not susceptible to dental caries but they can develop a periodontitis condition called peri-implantitis where correct oral hygiene routines have not been followed. Failure in dental implants is found to be increased in the anterior mandible where bone quality is not as dense. Risk of failure is increased in smokers. For this reason implants are frequently placed only after a patient has quit 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.