Bone regeneration in sinus augmentation procedures with calcium sulphate. Microstructure and microanaytical investigations

Background: The aim of this study was a histological and ultrastructural evaluation of the bone formed in human sinus augmentation procedures with calcium sulphate (CaS). Methods: Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were used to evaluate the relationship between CaS and newly-formed bone, while birefringence was used to evaluate the bone structure around the CaS particles by polarized light microscopy. Unstained sections were studied with an Axiovert 200 M using the fluorescence in reflected UV light to evaluate the interface between CaS and newly-formed bone. Twenty specimens retrieved from the sinus after a healing period of six months were studied. Results: EDS analysis of six specimens showed that little sulphur remained and residual particles appeared to have transformed to calcium phosphate. Under polarized light a few biomaterial remnants were present in some areas and covered by mature bone. The relationship between residual particles and bone due to the different photon emission under UV light stimulation was observed under fluorescence microscopy. Conclusions: The present results confirm the high biocompatibility and rapid resorption rate of CaS. The mechanism of transformation of CaS to calcium phosphate, already demonstrated in animal studies, has been confirmed in the present human study.