The purpose of this study was to evaluate bone formation around recombinant human bone morphogenetic protein (rhBMP-2)-coated implants placed with or without absorbable collagen sponge (ACS) in rabbit maxillary sinuses.

The Schneiderian membrane was elevated and an implant was placed in 24 sinuses in 12 rabbits. The space created beneath the elevated membrane was filled with either blood ( n =6) or ACS ( n =6). In the rabbits in which this space was filled with blood, rhBMP-2-coated and non-coated implants were alternately placed on different sides. The resulting groups were referred to as the BC and BN groups, respectively. The AC and AN groups were produced in ACS-grafted rabbits in the same manner. Radiographic and histomorphometric analyses were performed after eight weeks of healing.

In micro-computed tomography analysis, the total augmented volume and new bone volume were significantly greater in the ACS-grafted sinuses than in the blood-filled sinuses ( P <0.05). The histometric analysis showed that the areas of new bone and bone-to-implant contact were significantly larger in the AC group than in the AN group ( P <0.05). In contrast, none of the parameters differed significantly between the BC and BN groups.

The results of this pilot study indicate that the insertion of ACS after elevating the Schneiderian membrane, simultaneously with implant placement, can significantly increase the volume of the augmentation. However, in the present study, the rhBMP-2 coating exhibited limited effectiveness in enhancing the quantity and quality of regenerated bone.