De novo bone formation after the sinus lift procedure.

BACKGROUND The primary objective of this study is to use histomorphometric techniques to evaluate the concept that the new bone formed in the maxillary sinus lift procedure emanates from the endosteum of the sinus floor. In addition, the effect of the residual crest vertical dimension on the graft outcome and assessment of osteoclast numbers as an indirect measure of a connection between the crest and graft compartment are reported. METHODS After grafting the maxillary sinus with irradiated allogenic bone, 37 intact, vertical bone cores with a 2.7 mm diameter were trephined at right angles to the alveolar crest. Quantitative measures were derived from a histomorphometric analysis of new bone and residual graft particles at contiguous zones along the long axis of the cores. Mean and median data were analyzed for associations with the distance from the sinus floor, dimensions of the residual crest, and other descriptive variables. A parallel series of tartrate resistant acid phosphatase-stained sections were evaluated for osteoclast counts. RESULTS Mean new bone formation ranged from 24.3% to 30.2%. A statistically significant gradient of graft-particle area combined with this uniform distribution of new bone resulted in a false impression of less consolidation with the distance from the floor. There was no significant relationship between the distance from the sinus floor or dimension of the residual crest and the graft result. Mean osteoclast counts revealed a statistically significant difference (P <0.001) between the residual crest and the graft compartment with increased counts in the graft. CONCLUSIONS Histologically, the process of new bone formation resembled a combination of de novo appositional and intramembraneous ossification. The findings suggested a passive role for the graft material and implicated the ingrowth of vascular and perivascular tissues as the most logical source of osteogenic capacity.