Implant Treatment: Advanced Concepts and Complex Cases

Immediate Postextraction Placement of Implants

When implant placement is planned before tooth extraction, consideration should be given to the most desirable time for implant placement. The implant may be placed immediately (i.e., at the time of extraction), early (i.e., 2 months after extraction), or late (i.e., more than 6 months after extraction). Each of these times has its indications, advantages, and disadvantages.

The primary advantage of immediate placement is that this allows the overall shortest healing time and combines tooth extraction with surgical implant placement. Placing a provisional restoration at the same procedure may provide the best opportunity for maintenance of soft tissue anatomy and the best immediate and long-term esthetic results. The primary disadvantage of immediate placement is related to the difference in the anatomy of the root or roots of the extracted tooth compared with the shape and size of the implant. This is particularly true of a multirooted tooth that is being replaced by an implant. Even in the case of an incisor, the difference in the shape of the root and that of the implant creates some difficulty in implant placement. Another disadvantage is that if the implant is exposed to excessive occlusal forces, the immediate and long-term stability of the implant can be jeopardized.

Immediate placement can be considered if the tooth to be removed is not infected and can be removed without the loss of alveolar bone. A critical component in the success of this technique is to complete the extraction of the tooth with minimal bone removal and without distorting or weakening the bony support. An atraumatic extraction technique using periotomes will help minimize damage to bone and help facilitate implant placement. Initial implant stability at the time of placement is also critical to long-term success. When the implant is placed, at least 4 mm of the implant apex should be precisely seated in firm bone to provide this initial stability ( Fig. 15.1 ). Surgical guides are extremely helpful in placing the implant because drilling the implant site at the correct angulation can sometimes be difficult because the drill can be easily deflected when bouncing off the wall of the socket ( Fig. 15.2 ). The implant should be countersunk slightly below the height of crestal bone to allow for resorption of bone resulting from extraction. In the esthetic zone (maxillary anterior), the platform of the implant is ideally placed 3 mm below the free gingival margin. This allows for development of optimal emergence contour of the final restoration and soft tissue maintenance. In general the implant is also positioned 1 mm palatal to the center of the extracted tooth root. This accounts for anticipated facial bone and soft tissue remodeling that decreases the facial crestal volume.

The gap between the implant and the residual tooth socket must be evaluated and managed according to its size. If the gap is less than 1 mm and the implant is stable, often no treatment modification is needed. If the gap is greater than 1 mm, grafting with a particulate bone material may be indicated. At present the need for this is controversial. In most cases, with flapless, atraumatic extraction techniques, primary closure may not be possible or desirable. In this situation, a resorbable collagen pellet may be placed over the implant and held in place with a figure-of-eight suture. The surgeon may consider extending the time allowed for integration before loading.

In isolated cases, restoration at the time of implant placement may be considered. It is extremely important to ensure that the restoration is in ideal firm contact with adjacent teeth, which will help to reduce unfavorable loading on the implant until it is osseointegrated.

Bone Grafting and Graft Substitutes

In many cases, areas to be restored with implants have insufficient bone for implant placement. This may be a result of extraction and bone atrophy, sinus pneumatization, previous trauma, congenital defects, or removal of pathologic lesions. In these cases, bone will need to be augmented to provide adequate support for implant placement. Several potential sources of graft material can be considered, depending on the volume and configuration of bone needed.

Autogenous Grafts

Autogenous bone can be harvested from several anatomic areas. Intraorally, bone can be harvested from the mandibular symphysis, ramus, or maxillary tuberosity areas. Bone in the tuberosity is primarily cancellous, whereas in the ramus–posterior body area of the mandible, the bone is primarily cortical. The symphysis provides the best intraoral source for a reasonable volume of cortical and cancellous bone ( Fig. 15.3 ). When more bone is required for situations such as atrophic edentulous mandible or bilateral sinus lifts, an extraoral site should be considered if autogenous bone is to be used. The most common site of graft harvest is the anterior iliac crest. Other areas where bone is sometimes harvested include the tibia, the fibula, and the calvarium.