Anorganic bone matrix retrieved 14 years after a sinus augmentation procedure: a histologic and histomorphometric evaluation.

BACKGROUND: Anorganic bone matrix (ABM) is reported to have osteoconductive properties. No inflammatory or adverse responses have been reported when this material is used in sinus augmentation procedures. ABM is said to be a bioabsorbable biomaterial, but histologic data seem to suggest that the resorption process is slow. Long-term histologic data in humans are lacking. The aim of this case report was to evaluate the bone response to ABM used in maxillary sinus augmentation and retrieved 14 years after surgery. METHODS: Titanium dental implants were inserted in two sinuses augmented with ABM. The implants were osseointegrated and functioned well for 14 years. After this period of loading, the connecting screw of one of the implants inserted in the left maxilla broke, and it was necessary to remove the implant. A bone core of the augmented area was harvested separately during the implant removal. RESULTS: A very high quantity of mature, compact bone and a small percentage of residual grafted biomaterial were found. About 5% to 7% of the bone was undergoing remodeling. In most cases, residual ABM particles were surrounded by marrow spaces. In other areas, lamellar bone was found in tight contact with the particle surfaces. Histomorphometry showed that the mean amount of mature, compact bone was 71.0% +/- 2.28%, the mean amount of ABM was 22.1% +/- 3.18%, and the mean amount of marrow spaces was 11.2% +/- 5.42%. CONCLUSIONS: ABM seemed to resorb very slowly; after 14 years, only a small quantity of residual grafted particles was present. ABM is an effective graft material for sinus augmentation procedures. Vital, mature bone was formed and maintained over a long period with no chronic inflammatory cell infiltrate, foreign body response, or other adverse effects.