Bone Regeneration in Critical-size Defects Using Hydroxyapatite, Collagen and Chitosan

Objectives: Biodegradable bone grafts were widely employed on bone regeneration. The purpose of this study was to evaluate the osteoconductive potential of hydroxyapatite (HA), chitosan (Chi) and collagen (Col) composites in a rat critical-size calvaria defect model.

Methods: Two implants types were employed: HA(0,2mm-1,18mm)/Chi and HA(<0,2mm)/Col. A critical size defect (8mm) was created in the skull of Wistar rats (weight 200-300 g) and treated with autologous bone (positive control group) obtained during the confection of the defect,  HA/Chi, HA/Col or left untreated as a negative control (n=5). After at 30, 60 and 90 days, the animals were killed and the calvaria removed for histomorphometric analysis (stained by hematoxylin-eosin). New bone area was measured. Analysis of variance and Tukey's test were conducted (p<0.05).

Results: No adverse reactions were noted. No bone repair was observed in untreated surgical defects. The control group showed complete closure of the defect at 90 days. For the HA/Chi and HA/Col groups, the defect sites exhibited marked bone formation at the defect margin, and a dense connective tissue was observed in the center of the defect at 60 days. There was a tendency of remaining implant area to decrease and new bone area to increase at 90 days in both implant groups. Although degradation of the implants had occurred, some fragments of HA remains surrounded by new bone tissue after 90 days. The new bone area was highest in the autologous bone group, followed by HA/Col and HA/Chi groups, and the least was the negative control group.

Conclusion: The results of this study have demonstrated that HA/Col and HA/Chi composites have significant potential to promote new bone formation as a scaffold in rat critical size defects.