Implant Site Preservation
Since the introduction of dental implants into North America in the early 1980’s, we have witnessed an evolution in how implants are used to replace missing teeth. At the outset, implants were seen as a means to provide support to overdentures for edentulous patients. Subsequently, implants began being considered for single tooth replacement and even full arch dental replacement. In the infancy of this type of usage, implants were generally placed in the most available area of bone without regard to prosthetic restorability. As it became apparent that many of these restorations were not very functional and were difficult to maintain, implant dentistry became a much more prosthetically driven discipline.
The current ideal would have the implant placed in such a way that it ideally supports the proposed restoration. If the hard or soft tissue in the proposed placement region are deficient, then these can be augmented prior to implant placement. The development of new and innovative ways to augment both hard and soft tissue as well as to preserve existing hard and soft tissue have greatly enhanced our ability to perform highly esthetic and functional implant restorations.
Clearly the time to begin to preserve an implant site is at the time that a tooth is extracted from that site. If a patient is referred for an extraction of a tooth, the patient is asked at the consultation visit if he has considered his options for replacement of that tooth. The various options are reviewed with the patient and if a dental implant is a possibility, then site preservation is discussed with the patient. This generally involves a discussion of cleaning the socket out well and then grafting the site with a processed bone matrix. There are several that are quite good, one of the most popular being Bio-Oss, which is the bovine derived and purified mineralized matrix of bone. It is explained to the patient that this material when placed in the socket and covered over in proper fashion serves as a scaffolding to prevent soft tissue in-growth into the socket and maintains the optimal amount of bone height and density for subsequent implant placement. It is further explained that this will require a consolidation time for the graft of approximately four to six months before implants can be placed at the site.
While we all know that extraction sockets heal well without grafts, it is common to lose 1-2 mm of bone height at the area of an extraction site in general. In implant dentistry this is unacceptable in a proposed implant site for many reasons. In an esthetic area 1-2 mm of bone and soft tissue loss results in an overly elongated restoration. In posterior maxillary areas, 1-2 mm of bone loss may place the crest of the ridge too close to the maxillary sinus to place an implant of adequate length without a more extensive procedure such as a sinus floor augmentation (aka “sinus lift”). In the posterior mandible, 1-2 mm of bone loss can be the difference between being able to place an implant safely above the nerve, or having to modify or even abandon implant treatment planning.
Once the patient agrees to this type of socket preservation, then it is the responsibility of the surgeon to preserve the site in a number of ways. One of the most obvious ways is to perform an atraumatic extraction, often sectioning the tooth to avoid having to remove bone around the tooth root itself. Extra time is involved in attempting to remove the tooth without removal of any of its bony walls. If incisions are necessary, then papilla-sparing incisions are used to ensure optimal esthetics with regard to the adjacent teeth. Once the root is removed, the area is curetted out aggressively to remove any debris at the root apices and provide an optimal bed for the subsequent graft. The socket is then packed densely with a material such as Bio-Oss or freeze-dried demineralized bone or a mixture of the two, and covered with a resorbable membrane, or in many instances, a plug of gelfoam. Depending on the circumstances, attempts are made to close the soft tissue flap over the extraction socket in a tension free manner. In the anterior regions, every attempt is made to not have to make an incision in removing the tooth, and the labial and lingual flaps are pulled together over the graft with suture tension. Finally, a non-absorbable suture is used and removed typically one week later. Depending on the needs of the case, soft tissue grafting can also be done at that time in the proper setting, or can be deferred two to three months later and performed as a separate procedure prior to or at the time of implant placement. It is certainly easier, in clinical experience, to retain hard and soft tissues than to replace these tissues at a later date. By carefully planned site preparation through socket preservation, subsequent, more extensive surgical augmentation procedures can often be avoided.
One can see with the substantial advances in hard and soft tissue grafting techniques as well as in hard tissue grafting materials, that the potential for implant replacement has expanded exponentially. By working together with the surgeon who thinks prosthetically and works to not only prepare implant sites, but also to preserve them, the optimally functional and esthetic implant restoration can be achieved for our patients with a minimum of surgical procedures.