RESUMO
OBJECTIVES: To investigate the presence and composition of residual bone graft substitute material in bone biopsies from the maxillary sinus of human subjects, following augmentation with calcium sulphate (CaS). MATERIAL AND METHODS: Bone cores were harvested from the maxillary sinus of patients who had undergone a sinus lift procedure using CaS G170 granules 4 months after the initial surgery. Samples from seven patients, which contained residual biomaterial particles, were examined by field emission scanning electron microscopy and energy dispersive X-ray spectroscopy was used to determine the composition of the remaining bone graft substitute material. RESULTS: Residual graft material occurred in isolated areas surrounded by bone and consisted of individual particles up to 1 mm in length and smaller spherical granules. On the basis of 187 separate point analyses, the residual material was divided into three categories (A, B and C) consisting of: A, mainly CaS (S/P atomic% ratio > or =2.41); B, a heterogeneous mixture of CaS and calcium phosphate (S/P=0.11-2.4) and C, mainly calcium phosphate (S/P< or =0.11; C), which had a mean Ca : P ratio of 1.63+/-0.2, consistent with Ca-deficient hydroxyapatite. Linescans and elemental maps showed that type C material was present in areas which appeared dense and surrounded, or were adjacent to, more granular CaS-containing material, and also occurred as spherical particles. The latter could be disintegrating calcium phosphate in the final stages of the resorption process. CONCLUSIONS: CaS resorption in the human maxillary sinus is accompanied by CaP precipitation which may contribute to its biocompatibility and rapid replacement by bone.