A typical implant consists of a titanium screw (resembling a tooth root) with a roughened surface. This surface is treated either by plasma spraying, etching or sandblasting to increase the integration potential of the implant. An osteotomy or precision hole is carefully drilled into jawbone and the implant is installed in the osteotomy.
Implant surgery is typically performed as an outpatient under general anesthesia or with Local anesthesia by trained and certified clinicians including oral surgeons, and periodontists. The most common treatment plan calls for several surgeries over a period of months, especially if bone augmentation (bone grafting) is needed to support implant placements. At the other end of the surgery scale, some patients can be implanted and restored in a single surgery, in a procedure labeled "immediate function" and "teeth in an hour."
Healing and integration of the implant(s) with jawbone occurs over several months in a process called osseointegration. At the appropriate time, the restorative or cosmetic dentist or prosthodontist uses the implant(s) to anchor crowns or a prosthetic restoration containing several "teeth". Since the implants supporting the restoration are integrated, which means they are biomechanically stable and strong, the patient is immediately able to masticate (chew) normally.
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, what must be addressed is the functional aspect of the final implant restoration, the final occlusion. How much force per area is being placed on the bone implant interface? Implant loads from chewing and parafunction can exceed the physio 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 restorative 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 reversed 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 consults with the oral surgeon, trained general dentist, or periodontist 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 surgeon's request, and are used as physical aids to treatment planning. If not supplied, the surgeon makes his own or relies upon advanced computer-assisted tomography or a cone beam CAT scan to achieve the proper treatment plan.
Computer simulation software based on CAT 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 stereo lithography 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. Software products like Materialise' SimPlant (simulated implant) use the digital data from a CAT scan (such as an iCAT or a NewTom) to provide extremely accurate simulations that are easily understood by patients. When options have been fully discussed between patient and surgeon, the same software can be used to produce precision drill guides. |
