Reposition of the bone plate over the antrostomy in maxillary sinus augmentation: A histomorphometric study in rabbits

OBJECTIVE: To test if repositioning the bony plate secured with a cyanoacrylate over the antrostomy in maxillary sinus augmentation was superior to covering the antrostomy with a collagen membrane in terms of the bone augmentation area and the bone density. MATERIAL AND METHODS: After the exposure of the nasal bone in eighteen rabbits, a rectangular access window was prepared with a sonic instrument, and the bony plate was removed. A bilateral sinus mucosa elevation was performed, and the space was filled with a resorbable xenograft. On the test side, the bone plate was repositioned over the antrostomy and fixed with a cyanoacrylate. On the control side, a collagen membrane was placed over the opening. Per group, six animals were sacrificed after 2, 4, and 8 weeks of healing, respectively. Histological ground sections were prepared. RESULTS: The augmented area after elevation decreased between 2 and 8 weeks from 9.4 ± 1.8 to 4.8 ± 2.8 mm2 at the test and from 9.5 ± 2.6 and 5.1 ± 1.6 mm2 at the control sites. Small amounts of new bone were seen after 2 weeks in both groups (~1.6%-2.5%) forming from the bony sinus walls. New bone density increased over time in both groups reaching ~ 10%-11% and ~ 23%-25% after 4 and 8 weeks, respectively. No statistically significant differences were found. Small residual defects were present both at the test sites in the margin of the bone plate, and at the control sites in the center of the antrostomy. CONCLUSIONS: The bone healing in the elevated sinus space was similar irrespective of the coverage of the antrostomy. After 8 weeks, the bone plate repositioned on the antrostomy was incorporated while at the control sites the healing was still incomplete. Residual defects were still present in both groups