en Oral & maxillofacial surgery Oral & maxillofacial surgery Original article Original article <p style="text-align: justify;"><strong>Background and Aim:</strong> Autogenous bone grafts are considered the gold standard although they have several disadvantages, leading to a search for suitable alternative graft biomaterials. This study evaluates the histological and histomorphometric properties of regenerated bone in defects in rabbits following the application of two commercially available xenografts (Bio-Oss and Osteon).<br> <strong>Materials and Methods</strong>: This animal study was carried out on 14 New Zealand rabbit calvaria. Four 6.5-mm critical-size defect (CSD) models of bone regeneration were formed in each surgical site. The first defect was filled with Bio-Oss, the second with large Osteon (L-Osteon), the third with small Osteon (S-Osteon), and the last one remained unfilled (the control group). The cases were sacrificed. Bone forming properties (amount of new bone formation, inflammation, and foreign body reaction) were observed at 4- and 8-week intervals through histological and histomorphometric examinations. The Friedman test, Kruskal-Wallis test, and Wilcoxon test for multiple comparisons were used for data analysis. The level of statistical significance was set at 0.05.<br> <strong>Results: </strong>There was no statistically significant difference for regenerated bone among the four groups (P>0.05). The L-Osteon site showed more inflammation and foreign body reaction compared to the other groups.&nbsp;<br> <strong>Conclusion:</strong> The results of this study showed that Bio-Oss and Osteon appear to be highly biocompatible and osteoconductive and can thus successfully be used as bone substitutes in augmentation procedures.</p> Biocompatible Materials, Bio-Oss, Bone Grafting, Bone Formation, Bone Substitutes, Histology, Osteon 26 33 http://jrdms.dentaliau.ac.ir/browse.php?a_code=A-10-560-3&slc_lang=en&sid=1 F Sarkarat 10031947532846008812 10031947532846008812 No Associated Prof, Department of Oral and Maxillofacial Surgery and Craniomaxillofacial Research Center, Dental Faculty, Tehran Medical Sciences SA Vahdati 10031947532846008813 10031947532846008813 No Doctor of Dental Surgery, Advanced Specialty Education Programs in Endodontics and Implant Dentistry HR Mahaseni aghdam hamidmahaseni@gmail.com 10031947532846008814 10031947532846008814 Yes Assistant Prof, Department of Oral and Maxillofacial Surgery and Craniomaxillofacial Research Center, Dental Faculty, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran. Z Nematallahi 10031947532846008815 10031947532846008815 No Doctor of Dental Surgery, Craniomaxillofacial Research Center, Dental Faculty, Tehran Medical Sciences M Farahmand 10031947532846008816 10031947532846008816 No Postgraduate Student, Department of Orthodontics, Dental Faculty, Tehran Medical Sciences