Maxillary sinus augmentation prior to placement of endosseous implants: A histomorphometric analysis

The aim of this prospective study was to histomorphometrically evaluate at various time intervals the mineralization stage and process of an allogenei c-xenogeneic bone graft used in sinus augmentation procedures. One biopsy w as taken from 20 patients at either 6, 8, 10, or 12 months after sinus augm entation. Immediately following the biopsy, an endosseous implant was place d into the biopsy site. This protocol provided 4 groups of 5 patients each, based on healing time following sinus augmentation. Using backscattered el ectron image analysis, the specimens were histomorphometrically analyzed to determine the volume fractions of residual cancellous bone, newly formed b one, soft tissue, bovine hydroxyapatite, and "remineralized" freeze-dried d emineralized bone allograft (rDFDBA). "Remineralization" of DFDBA particles was observed in a few areas in all specimens. Polarized light microscopy s howed that only the 12-month biopsies had a predominance of lamellar bone f ormation. The area within the biopsies that represented the residual alveol ar ridge consisted of 32.6% +/- 8.6% (mean +/- SD) of bone. In the grafted area of the biopsies the volume fraction of newly formed bone at 12 months (20.7% +/- 8.3%) was significantly higher (P < .05, analysis of variance) t han at 6 months (8.1% +/- 3.0%). There was no statistically significant dif ference between newly formed bone in the inferior, central, and superior gr afted areas in all 4 time intervals. This prospective study indicates that the mineralization process of an allogeneic-xenogeneic sinus graft is incom plete 6 months after the sinus augmentation procedure. New bone formation i ncreased up to 12 months postaugmentation; however, it remained lower than the volume of residual bone.