Histomorphometric and Radiographic Analysis of Biological Responses Following the Use of Pure Hydroxyapatite and Hydroxyapatite with Collagen

Background and Objectives: The objective of this study was to evaluate in vivo two new biomaterials for bone substitution aiming to determining their ability to enable bone neoformation in critical-size defects in rats’ calvaria. Methods: Synthetic hydroxyapatite were developed – Pure hydroxyapatite (HaP) and Hydroxyapatite with collagen (HCol). The third synthetic hydroxyapatite used as a comparing element was the commercial hydroxyapatite Alobone® (HaAl). Sixty Wistar rats divided randomly into four groups (Group 1, HaP; Group 2, HaCol; Group 3, HaAl and Group 4, Control). Critical size defects of 8mm were performed in the calvaria, and the three biomaterials were implanted. All groups also received a collagen membrane. Results: On day 30, the inflammatory response on the defect was practically absent in all groups, mainly when compared to the period of 7 days. Some areas of bone neoformation were seen. There was predominance of osteoblasts, osteocytes, and macrophages in lower amounts. Regarding the radiographic aspect, after 30 days, a marked biodegradation of the hydroxyapatite and signs of bone neoformation were observed. Conclusions: It was concluded that the results of our study in vivo can be used as a preliminary source of information about biocompatibility, biodegradability, and bone neoformation from the implant of new biomaterials in vivo.