This study presents the clinical, radiological, histological and histomorphometric results on the use of a biphasic calcium phosphate (Straumann® bone ceramic) in a MSFE procedure with healing times of 9 and 12 months. During the clinical evaluation, it appeared that both 9-month and 12-month healing times resulted in integration of the grafted BCP with the original maxillary bone (sinus floor), which was stable enough to ensure successful dental implant placement. It should be mentioned that in this study, a minimal native alveolar bone height of 4 mm was preferred, ensuring a certain primary stability of the dental implants placed. An adequate and stable tissue height in the grafted area was observed radiologically in a 5-year follow-up in all patients in both 9-month and 12-month healing time groups.

Radiological observations show very stable results in different healing times, in a previous 6-month study [27] and after 9- and 12-month healing times in the present study. However, this does not reveal the actual vital bone height available for attachment to the dental implant surface. This can only be measured by histological investigations. Reviews show that the loss of dental implants with an intra-osseous length of 8 mm or more, placed in native bone, is minimal [4]. Previously, the histomorphometrical and histological evaluation, 6 months after an MSFE procedure, using Straumann® bone ceramic was reported with a 1-year follow-up. At that time, no loss of dental implants was reported. In the present study, none of the implants in the 9- and 12-month groups were lost. Histological investigation showed that mineralized bone tissue was observed to be in intimate contact with the bone substitute particles, indicating that the graft material possesses osteoconductive properties [27] (which is in agreement with other observations) [16, 24, 34]. This positive effect might be explained by its chemical composition. BCP materials have shown bone formation simultaneously with material degradation [24, 25]. BCP exhibited moderate signs of substitute degradation in humans not only after 6 months, as previously reported by Frenken et al. [27]. The present study still observed remnants of BCP after 9 and 12 months which suggests that the ossification rate is not the same as the resorption rate of the BCP. Because osteoclasts were detected next to the characteristic outlines of the substitute particles, it is suggested that BCP is resorbed by osteoclasts. The high bone formation in the newly formed bone area indicates that after 12 months, bone cells are still actively forming new bone matrix, thereby absorbing and replacing BCP in vital bone tissue.