Histomorphometric and densitometric changes in bone volume and structure after avascular bone grafting in the extremely atrophic maxilla

Abstract

Aim: To evaluate changes in volume and structure of bone after autogenous iliac crest bone grafting to the maxilla. To discover the predictive value of computed tomographic (CT) measurements of bone density and study their correlation with the results of his tomorphometric analyses of bone structure. Patients and methods: In 25 patients with atrophic maxillae (mean age 47 years, range 15–71), who had onlay bone grafting and sinus floor augmentation with autogenous iliac crest bone, a CT analysis was carried out immediately before and after grafting, and 5 months (range 4–6) later, at the time of endosseous implantation. On both occasions, bone biopsy specimens were taken. Histology of bone: After preparing and digitizing semithin sections, histomorphometry (NH-Image) was done to establish the ratio of trabeculae to medullary cavity. CT analysis: The available transverse and vertical bone and the bone density of natural and augmented bone were analyzed using the Simplant Program and the CT data. As reference, the bone density of the first cervical vertebra was used. By regression analysis, the correlation of CT bone density and histological bone structure was investigated. Results: After a median healing period of 4.5 months, no significant changes were found in bone volume compared with the measurements made immediately after grafting. The changes in density in the cancellous portion of the grafted bone showed no correlation (correlation coefficient: +0.16) with the results of histomorphometric analysis of bone structure. Conclusions: The predictive value of measurement of bone density to evaluate bone structure on the basis of the D1–D4 classification needs to be reconsidered. The most favourable time for secondary implantation is 4–6 months after iliac crest bone grafting.