The results of this study indicate that alveolar bone resorption following tooth extraction may be prevented or reduced by the use of a bioabsorbable synthetic sponge of polylactide-polyglycolide acid. The quality of bone formed seemed to be optimal for dental implant insertion.

The aims of the present study were to analyze (i) which tissue changes may occur in the zone of co-destruction to better understand why trauma from occlusion may induce additional attachment loss, and (ii) whether changes occur in the periodontal ligament tissue when an inflammatory lesion (ICT) approaches the periodontal ligament space. 16, 1-year-old beagle dogs, were selected and divided into 2 groups, group A and group B, consisting of 6 and 10 dogs, respectively. In group A, on day 0, a bucco-lingual jiggling type movement was induced resulting in increasing tooth mobility at P3 (test tooth) by the application of an orthodontic elastic which traversed the buccal surface of the crown of the test tooth. The elastic was exchanged either in a buccal or in a lingual position 2x a week during a 3-month period. 3P served as non-jiggled control tooth. Tooth mobility measurements were recorded on days 0, 30, 60, 90. A plaque control regimen was maintained until the end of the experiment (day 90). On day 90, biopsies including P3 and 3P were harvested. The dogs representing group B, were divided into 2 subgroups of 5 each, group BI and group BII. On day 0, a 4-month period of experimental periodontal tissue breakdown was initiated by placing cotton floss ligatures submarginally around the mandibular fourth premolars (4P4) in group BI and around the mandibular third premolars GP3) in group BII. All ligatures were exchanged, replaced 1x every month, and on day 120 permanently removed. On the same day, biopsies included 4P4 were harvested. Following supragingival debridement 3P3 were allowed to accumulate plaque until the end of the study (day 225). On this occasion, biopsies including 3P3 were harvested. The results of the histological measurements revealed that in the most coronal portion of the periodontal ligament of teeth exhibiting increasing mobility, there was an increased width, a reduced % tissue volume of collagen, and an increased volume of vascular structures and leukocytes. Furthermore, the number of osteoclasts bordering this portion of the alveolar bone was increased and the number of collagen fibers inserting into the root cementum and into the alveolar bone was reduced. It was also demonstrated that in teeth with normal mobility, the position of the gingival ICT failed to influence the composition of the tissue within the coronal portion of the periodontal ligament.

The aim of the present investigation was to analyze the periodontal tissues at immobilized teeth connected to osseointegrated implants. 10, 1‐year old beagle dogs, were used. Bilaterally, the mandibular 2nd (2P2) and 3rd pre‐molars (3P3) and 1st molars (1M1) were extracted. 2 titanium fixtures were installed in the edentulous segment of the right side of the mandible, one about 10 mm mesial and the other about 10 mm distal to 4P (test tooth). 3 months later, abutment connection was performed and healing allowed for one month. The dogs were randomly 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 4P was hereby immobilized. The controlateral 4th premolar (P4) served as the non‐splinted control tooth. Plaque control measures continued until the end of the experiment (day 180). In group B, plaque control measures were abandoned 1 month after abutment connection and a 4‐month period of experimental periodontal tissue breakdown was initiated. This was accomplished by placing cotton floss ligatures submarginally around 4P and P4. At the end of this 4‐month period, the ligatures were removed, and an apically positioned flap procedure was performed. Healing was allowed for another 2 months. Plaque control measures were re‐established and continued throughout the experiment. A given day was termed day 0 and 4P was rigidly connected to the adjacent implants in the manner described for group A. At the end of a subsequent 6‐month period, radiographs of 4P and P4 were taken and biopsies harvested from all the dogs. The results of measurements, made in histological sections, revealed that the splinting of mandibular premolars to osseointegrated implants failed to induce marked alterations (qualitative and quantitative) in the gingiva and periodontal tissues of the immobilized teeth. These findings offer a biological explanation for the fact that a fixed bridge, utilizing both teeth and implants as abutments, seems to function well in the rehabilitation of partially edentulous patients.

The aim of the present investigation was to analyze the periodontal tissues at immobilized teeth connected to osseointegrated implants. 10, 1-year old beagle dogs, were used. Bilaterally, the mandibular 2nd (2P2) and 3rd premolars (3P3) and 1st molars (1M1) were extracted. 2 titanium fixtures were installed in the edentulous segment of the right side of the mandible, one about 10 mm mesial and the other about 10 mm distal to 4P (test tooth). 3 months later, abutment connection was performed and healing allowed for one month. The dogs were randomly 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 4P was hereby immobilized. The controlateral 4th premolar (P4) served as the non-splinted control tooth. Plaque control measures continued until the end of the experiment (day 180). In group B, plaque control measures were abandoned 1 month after abutment connection and a 4- month period of experimental periodontal tissue breakdown was initiated. This was accomplished by placing cotton floss ligatures submarginally around 4P and P4. At the end of this 4-month period, the ligatures were removed, and an apically positioned flap procedure was performed. Healing was allowed for another 2 months. Plaque control measures were re-established and continued throughout the experiment. A given day was termed day 0 and 4P was rigidly connected to the adjacent implants in the manner described for group A.(ABSTRACT TRUNCATED AT 250 WORDS)