DELAYED IMMEDIATE IMPLANTS - ALVEOLAR BONE CHANGES DURING THE HEALINGPERIOD

Delaying the placement of immediate fixtures by 6-8 weeks after extrac tion of the natural dentition allows for the elimination of associated infective processes, the achievement of maximum osteoblastic activity that theoretically could help the osseointegration process and comple te wound covering that simplifies the placement of grafts or membranes . This study examines the healing associated with 21 fixtures in 14 pa tients. The fixtures were placed into sockets 6-8 weeks after tooth ex traction without the use of barrier membranes or bone substitutes. Mea surements were taken immediately prior to fixture placement and 3-6 mo nths later at the abutment placement. Alveolar bone height, the remain ing socket depth and diameter and the depth to which a 3.75 mm fixture could be inserted into the socket were measured. After fixture placem ent the vertical and horizontal measurements from the cover screw to t he surrounding alveolar bone and the distance from the cover screw to the CEJ of the adjacent tooth were recorded. All fixtures were integra ted at exposure with 1 failure during the follow-up period. The distan ce from the cover screw to the buccal plate decreased by a mean of 2.1 7 mm. There was an increase in the mean vertical bone height at all 4 surfaces. When horizontal defects were present, the mean vertical dist ance decreased from 2.5+/-0.37 mm to 0.36+/-0.64 mm. When horizontal d efects were absent, the mean vertical distance decreased from 3.86+/-0 .58 mm to 0.48+/-0.25 mm. There was also a marked decrease in the hori zontal distance between the bone margin and the surface of the fixture from 1.6+/-1.73 mm to 0.02+/-0.02 mm. These results indicate a strong tendency for the defects to fill-in in the horizontal plane and for b one growth to occur in the vertical plane to the height of the cover s crew. In conclusion the delayed immediate placement of fixtures has a good short-term prognosis with bone regeneration occurring around the defect without the use of barrier membranes or bone substitutes.