Abstract: Objective: To compare the bone dimensional changes following tooth extraction alone with extraction plus ridge preservation (using deproteinized boving bone mineral Bio-Oss^® and bioresorbable collagen mambrane Bio-Gide^®) in periodontal compromised extraction sockets.  Methods: Eighteen molars of sixteen subjects requiring tooth extraction because of periodontal destruction were enrolled in this study. The subjects were assigned to the control group (extraction alone, EXT) or to the test group (ridge-preservation procedure with Bio-Oss^® and Bio-Gide^®, RP). Parallel periapical X-rays and cone-beam computed tomography (CBCT) scans were taken immediately after tooth extraction alone or plus ridge-preservation (baseline) and 6 months later. The changes of horizontal ridge width and vertical ridge height were assessed. Results: At the central buccal aspect, the ridge height increased 2.9 mm in RP group, and reduced 1.0 mm in EXT group. At the distal buccal aspect, the ridge height increased 1.45 mm in RP group, and reduced 1.45 mm in EXT group. The differences between the groups reached statistical significance (P<0.05). The mean ridge width increased at the 1 mm below the crest (the horizontal ridge width was measured with grafting material at three levels at 1 mm below the most coronal aspect of the crest, HW1), which amounted to 3.40 to 5.80 mm in RP group, and 1.45 to 2.90 mm in EXT group. The mean ridge increased at the 4 mm below the crest (the horizontal ridge width was measured with grafting material at three levels at 4 mm below the most coronal aspect of the crest，HW4), which amounted to 0.40 to 3.50 mm in RP group, and reduced 0.10 to increased 0.15 mm in EXT group. The test group and the control group were not significantly different (P>0.05).Conclusion: The ridgepreservation approach using Bio-Oss^® in combination with Bio-Gide^® can significantly increase vertical ridge height and horizontal ridge width after tooth extraction compared with extraction alone in periodontal compromised molars.

Key words: Tooth extraction, Space maintenance, Alveolar bone loss, Biocompatible materials, Molar