Single tooth implants 323

mobility of the involved implants was reduced to the range of about a Class II, with no pain on palpation or pressure. By being splinted, the implants had definitely become less mobile over a period of months. Although mobility still did exist, however, it was a type that was supported by a dense tissue tenaciously attached to the implants. Whereas after the first 90 or so hours the implants could have been pulled out merely with two fingers, a great deal of luxation with an extraction forceps was now required to remove them.

As a number of years went by, Group I implants never became any firmer than a Class II mobility. However, no pain occurred. These results apparently support the idea that once an implant has drastically loosened, the thick, soft tissue membrane that forms around it prevents bone from ever re-generating close to the implant. Thus the implant always remains slightly loose.

The Group II implants, which were immediately splinted with ligature wire and kept that way for 6 months or more, exhibited far less mobility, but mobility just the same. The slight mobility probably resulted from the ligature wires not being stable enough. Therefore, as the wire loosened it caused the implants to loosen.

The Group III implants, which were immediately stabilized with tiny acrylic wing splints ex-tending to a neighboring tooth on each side, remained fairly stable over a long period. This stabilization procedure, which has little effect on the structure and appearance of its neighboring teeth, seems very promising.

Those implants in Group IV, which were A-splinted to neighboring teeth, were the most secure over a long period. Interestingly enough, those implants whose splints were purposely disassembled after about a year remained far more stable over a period of several years than those left unsplinted. Perhaps the teeth nearest the unsplinted implants shifted slightly, moving themselves as well as the approximating implant restoration out of good occlusion. It is Linkow's belief that the danger caused by the trauma to the bone induced by the implantation was the predisposing cause for the failure of the unsplinted implants.

SINGLE TOOTH IMPLANTS WITH ONE NATURAL ABUTMENT TOOTH

There are times when the patient and dentist do not want to prepare the teeth neighboring the edentulous space. The reasons for this hesitancy may

be quite valid. For example, if a lower first bicuspid is missing, it would necessitate preparing the cuspid as well as the second bicuspid for a three-unit fixed partial denture. Often, the cuspid crown restoration is much bulkier than the original tooth and the patient is disappointed in the esthetic appearance of the restoration.

Another valid reason is, why ruin a perfectly good tooth that has no filling or evidence of caries? Also, after preparing a perfectly good tooth for a full crown restoration, postoperative sensitivity sometimes occurs, necessitating the eventual removal of the tooth's nerve. This can be very embarrassing for the dentist.

In some situations where one tooth is missing, the construction of a one-tooth crown with a cantilevered pontic can often be effective. This is particularly true if the missing tooth is a lateral incisor that can be supported by a much stronger cuspid crown restoration. However, to replace a molar with another molar crown or to replace a bicuspid with another bicuspid crown is not sensible. When it is feasible, the introduction of an implant using one neighboring tooth, usually the distal one, as one of the abutments for a two-unit bridge usually gives fine results. The abutment tooth can be prepared for a two-surfaced inlay or for a full crown restoration. The following cases illustrate some single tooth implants stabilized with one abutment tooth.

Case 6

Stabilizing a single tooth implant with an inlay

Here a maxillary first bicuspid was replaced with an implant and crown attached to an inlay. This in-lay was locked into a mesioocclusal inlay preparation that was previously made into an existing gold inlay of the second bicuspid. On the first visit, an inlay preparation was prepared inside the existing inlay (Fig. 8-41). A hydrocolloid impression was taken of the inlay, edentulous space, and at least one tooth anterior to the space. A wax interocclusal record of centric relation and an opposing jaw alginate impression were also taken. A one-piece casting of an inlay and acrylic-over-gold thimble crown was fabricated on the master stone model. It was tried in the mouth on the second visit, and all necessary adjustments were made. The fabrication of the two-unit restoration was accomplished on the master stone model (Fig. 8-42), and the two-unit splint (inlay and crown) was tried in the mouth. Its occlusion and the marginal adaptation of the inlay were carefully checked.