Tenting effect of the elevated sinus membrane over an implant with adjunctive use of a hydroxyapatite-powdered collagen membrane in rabbits

Purpose: The aim of this study was to determine the de novo bone formation beneath the Schneiderian membrane supported by an implant and with the adjunctive use of a hydroxyapatite-powdered collagen (HAC) membrane without bone grafting in rabbit sinuses. Material and methods: After sinus-floor elevation procedure, an experimentally devised mini-implant (4 mm in length and 3 mm in diameter) was placed in eight rabbits. For the experimental group, an HAC membrane was placed onto the elevated sinus mucosa prior to implant placement. The animals were allowed a healing period of either 4 or 8 weeks. Microcomputed tomography and histologic analyses were performed. Results: All implants placed at the thin lateral bony wall were histologically osseointegrated. The topography of the newly formed bone appeared to slope gently from the medial side down to the lateral side. The volume of new bone was significantly greater in the experimental group than in the control group at 4 weeks (P < 0.05), but not at 8 weeks. However, none of the samples in the two groups was entirely covered to the apex by bone tissue. Conclusions: It can be concluded that using the HAC membrane in combination with placement of an implant resulted in substantial bone formation around the implant, which might have been influenced by the proximity of the axial bony wall.