The bone integration effects of platelet-rich fibrin by removal torque of titanium screw in rabbit tibia.

Platelet-rich fibrin (PRF) is nowadays often used in various fields, but no removal torque studies have yet been done to evaluate the effects of the platelet-rich fibrin on the bone integration at the initial healing period. An experimental study have been performed in rabbits to evaluate whether the complete PRF clots can accelerate the bone integration of implants at the initial healing period after creating bone defects in tibias. The effect of the complete PRF clots on bone integration was studied in two rabbit groups, 4-week group (group A) and 6-week group (group B) after preparing bony defects. Artificial bony defects were prepared in the tibias of rabbits. The complete PRF clots was applied to the defects in the experimental group, whereas the defects were unfilled in the control group. Four weeks later, machined implants were installed into the rabbit tibias (group A). Six weeks after installation, the removal torque from nine rabbits was measured to examine the bone healing effect of PRF. In another rabbits (group B), 6 weeks after preparing bony defects, installation was performed, and another 6 weeks after installation, the removal torque from nine rabbits was measured. The authors found a positive significant effect of the complete PRF clots on bone integration (higher bone density) in group A installed at 4 weeks after preparing bony defects (p = 0.008; t-test), but not in group B installed at 6 weeks after preparing bony defects (p = 0.677).

New bone formation following sinus membrane elevation without bone grafting: histologic findings in humans.

PURPOSE: To determine whether sinus membrane elevation alone can lead to new bone formation on the maxillary sinus floor. MATERIALS AND METHODS: Among patients who were to receive implant treatment, those who had 4 to 5 mm of bone height in the maxillary sinus floor (as measured radiographically) were selected as candidates for sinus membrane elevation. The lateral sinus wall was exposed through a buccal mucoperiosteal incision. The sinus membrane was elevated through a bone window, and the space underneath the membrane was filled with absorbable collagen sponge (Collaplug). In the presence of blood in the space, the collagen sponge was left to soak up the blood; in the deficiency of blood, the sponge was saturated with venous blood drawn from the brachial vein. The mucoperiosteal flap was repositioned and closed with interrupted silk sutures. The sinus was left to heal for 6 months. Core specimens of the maxillary sinus floor were obtained using a trephine bur at 6 months after sinus elevation in patients treated between January 2006 and June 2009. The trephined sites were used for implant placement. The biopsy specimens were analyzed histologically to identify the presence and amount of new bone tissue. RESULTS: Thirteen specimens from eight patients were included in the study. Microscopically, 11 specimens exhibited no recognizable new bone tissue. Two specimens exhibited a small amount of woven bone on the surface of the sinus floor. CONCLUSION: Within the limits of this study of eight patients, little to no new bone formation was observed on the maxillary sinus floor at 6 months following sinus membrane elevation and support with blood-soaked collagen sponges.

Bone tissue formation in extraction sockets from sites with advanced periodontal disease: a histomorphometric study in humans.

PURPOSE: To investigate postextraction bone formation over time in both diseased and healthy sockets. MATERIALS AND METHODS: Core specimens of healing tissues following tooth extraction were obtained at the time of implant placement in patients treated between October 2005 and December 2007. A disease group and a control group were classified according to socket examination at the time of extraction. The biopsy specimens were analyzed histomorphometrically to measure the dimensional changes among 3 tissue types: epithelial layer, connective tissue area, and new bone tissue area. RESULTS: Fifty-five specimens from sites of previously advanced periodontal disease from 45 patients were included in the disease group. Another 12 specimens of previously healthy extraction sockets were collected from 12 different patients as a control. The postextraction period of the disease group varied from 2 to 42 weeks. In the disease group, connective tissue occupied most of the socket during the first 4 weeks. New bone area progressively replaced the connective tissue area after the first 4 weeks. The area proportion of new bone tissue exceeded that of connective tissue by 14 weeks. After 20 weeks, most extraction sockets in the disease group demonstrated continuous new bone formation. The control group exhibited almost complete socket healing after 10 weeks, with no more new bone formation after 20 weeks. CONCLUSIONS: Osseous regeneration in the diseased sockets developed more slowly than in the disease-free sockets. After 16 weeks, new bone area exceeded 50% of the total newly regenerated tissue in the sockets with severe periodontal destruction. In the control group, after 8 weeks, new bone area exceeded 50% of the total tissue.