THE PERIODONTAL-LIGAMENT OF TEETH CONNECTED TO OSSEOINTEGRATED IMPLANTS - AN EXPERIMENTAL-STUDY IN THE BEAGLE DOG

The aim of the present investigation was to analyze the periodontal ti ssues at immobilized teeth connected to osseointegrated implants. 10, 1-year old beagle dogs, were used. Bilaterally, the mandibular 2nd (P- 2(2)) and 3rd premolars (P-3(3)) and Ist molars ((1)M(1)) were extract ed. 2 titanium fixtures were installed in the edentulous segment of th e right side of the mandible, one about 10 mm mesial and the other abo ut 10 mm distal to P-4 (test tooth). 3 months later, abutment connecti on was performed and healing allowed for one month. The dogs were rand omly divided into 2 groups of 5 each, group A. and group B. In group A , a fixed gold splint, rigidly connecting the tooth and the 2 implants , was installed on day 0 and P-4 was hereby immobilized. The controlat eral 4th premolar (P-4) served as the non-splinted control tooth. Plaq ue control measures continued until the end of the experiment (day 180 ). In group B, plaque control measures were abandoned 1 month after ab utment connection and a 4-month period of experimental periodontal tis sue breakdown was initiated. This was accomplished by placing cotton f loss ligatures submarginally around P-4 and P-4 At the end of this 4-m onth period, the ligatures were removed, and an apically positioned fl ap procedure was performed. Healing was allowed for another 2 months. Plaque control measures were re-established and continued throughout t he experiment. A given day was termed day 0 and P-4 was rigidly connec ted to the adjacent implants in the manner described for group A. At t he end of a subsequent 6-month period, radiographs of P-4 and P-4 were taken and biopsies harvested from all the dogs. The results of measur ements, made in histological sections, revealed that the splinting of mandibular premolars to osseointegrated implants failed to induce mark ed alterations (qualitative and quantitative) in the gingiva and perio dontal tissues of the immobilized teeth. These findings offer a biolog ical explanation for the fact that a fixed bridge, utilizing both teet h and implants as abutments, seems to function well in the rehabilitat ion of partially edentulous patients.