80 Theories and techniques of oral implantology

Preparation of involved teeth

The teeth to be included in a fixed denture must be free from periodontal pockets and in good health. The gingiva should be firm and pink, with a normal, healthy gingival sulcus. This is essential, for the gingival margins of the sulcus must reach the coronal attachment of the epithelial cuff. Here, and here only, will the marginal gingiva be adequately braced against the crown, preventing the entrance of bacteria and food debris. If a healthy gingival sulcus is not established prior to impression-making, the crown may leave part of the tooth ex-posed to infection and decay.

After the treatment of inflamed or degenerated tissues, adequate time must be allowed for healing. A trough may be left adjacent to the tooth's surface after treatment of a periodontal pocket. Unless the tissues are allowed to heal against the tooth, the trough will persist, collect debris, and become the focus of another infection.

Frequently the position of the teeth shifts during periodontal disease, and the teeth move hack to their original positions after the periodontal fibers regenerate. A prosthesis made to fit over periodontally involved teeth will not only be unsuitable for these teeth when healed, but it may also harm the teeth as they attempt to return to their original positions.

During the course of periodontal disease inflammation often spreads into the mucosa around the teeth and over into edentulous areas. The mucosa becomes swollen, disfigured, and changes its shape and consistency. Impressions should not be taken of these tissues until they have healed or a poorly fitting prosthesis will result.

A good general rule is this: until diseased conditions are eliminated and the tissues have healed, fabricating a prosthesis should be postponed.

Occlusal adjustments

When a tooth has not had a functional antagonist for a long period of time, it will very likely have moved out of its proper occlusal relationships. Furthermore its supporting alveolar bone will have become osteoporotic, and its periodontal ligament may have reverted to little more than a connective tissue membrane. For these reasons, when an implant-supported prosthesis restores a functional antagonist, the opposing teeth must be carefully occluded and balanced. Coronal reshaping may be necessary to prevent traumatizing a highly unstable tooth.

Traumatic relationships between all existing teeth, whether or not they are to be included in the restoration, should he eliminated before constructing the prosthesis. The restoration should be designed to conform with the resulting occlusal patterns. Immediately after the prosthesis has been inserted, the occlusion should he carefully checked again and balanced. Because time and wear may change the occlusal relationships, periodic occlusal pattern studies are necessary. Even a fixed denture stabilized by implants leads eventually to occlusal shifts. although these develop more slowly than when the prosthesis is secured only by natural abutments. Prior studies of the patient's chewing patterns, plus an investigation of possibly harmful oral habits, should help the dentist anticipate these shifts.

When designing the occlusal surfaces of the pontics, the patient's natural teeth and newly established occlusal patterns should serve as a guide. The restoration should be harmonious with the functional pat-terns of the entire dentition. Abnormal relationships remaining in both jaws, and the periodontia of both will jeopardize the opposing teeth, the other teeth natural teeth and implant abutments.