OBJECTIVETo investigate the effect of new bone formation in sinus augmentation with guided bone regeneration (GBR) using collagen membranes.

METHODSThe first maxillary molars of 18 adult female Beagle dogs were extracted and the sinus floors of both sides were lifted with simultaneous implantation. A combination of autografts and Bio-Oss in a 2:1 ratio was placed in the space under the membrane. On the experimental side in each dog, the collagen membrane was folded at the lateral osteotomy window, the apex of the implants and a certain part of palatal bone. On the contralateral control side, the collagen membrane only covered the osteotomy window. Six animals were sacrificed at 4, 12, and 24 weeks respectively after surgery. Gross observation, biomechanical testing and histological examinations were performed.

RESULTSThe translocation of grafted materials and bone absorption were found on the top of implants in the control side, and the grafted materials kept original shape at the experimental side at 4th week. The granule of Bio-oss absorbed obviously at 12th and 24th week. The pull-out force increased with time. At 24th week, the force of pull out was 558.1 ± 37.4 N at the study side, and 471.4 ± 31.5 N at the control side. There was a significant difference in the pull-out force was noted between the two groups (P < 0.01). Histological examination showed new bone formation on the sinus floor, and the grafted materials gradually reduced with time

CONCLUSIONSGBR with the enfolded-coverage of the membrane can effectively decrease absorption of the grafted materialon the apical surface of implants and stimulate new bone formation in the sinus augmentation.