Application of low-crystalline carbonate apatite granules in 2-stage sinus floor augmentation: a prospective clinical trial and histomorphometric evaluation

PURPOSE: The purpose of this study was to elucidate the efficacy and safety of carbonate apatite (CO(3)Ap) granules in 2-stage sinus floor augmentation through the radiographic and histomorphometric assessment of bone biopsy specimens. METHODS: Two-stage sinus floor augmentation was performed on 13 patients with a total of 17 implants. Radiographic assessment using panoramic radiographs was performed immediately after augmentation and was also performed 2 additional times, at 7±2 months and 18±2 months post-augmentation, respectively. Bone biopsy specimens taken from planned implant placement sites underwent micro-computed tomography, after which histological sections were prepared. RESULTS: Postoperative healing of the sinus floor augmentation was uneventful in all cases. The mean preoperative residual bone height was 3.5±1.3 mm, and this was increased to 13.3±1.7 mm by augmentation with the CO(3)Ap granules. The mean height of the augmented site had decreased to 10.7±1.9 mm by 7±2 months after augmentation; however, implants with lengths in the range of 6.5 to 11.5 mm could still be placed. The mean height of the augmented site had decreased to 9.6±1.4 mm by 18±2 months post-augmentation. No implant failure or complications were observed. Few inflammatory cells or foreign body giant cells were observed in the bone biopsy specimens. Although there were individual differences in the amount of new bone detected, new bone was observed to be in direct contact with the CO(3)Ap granules in all cases, without an intermediate layer of fibrous tissue. The amounts of bone and residual CO(3)Ap were 33.8%±15.1% and 15.3%±11.9%, respectively. CONCLUSIONS: In this first demonstration, low-crystalline CO(3)Ap granules showed excellent biocompatibility, and bone biopsy showed them to be replaced with bone in humans. CO(3)Ap granules are a useful and safe bone substitute for two-stage sinus floor augmentation. TRIAL REGISTRATION: ICTRP Identifier: JPRN-UMIN000019281