Biocomponents Based on Hydroxiapatite: Influence of Sterilization on the Mechanical Resistance

Objective  This study aimed to evaluate the influence of sterilization on the compressive and flexural mechanical strength of hydroxyapatite-based biocomponents obtained through freeze-dried bovine bone, and its association with chitosan. Methods  Freeze-dried bovine bone was processed into 100 μm particles and mixed with 50% of its weight in chitosan. The mixture was packed in metallic molds for preparing the specimens, and sterilized at 127°C using an autoclave for subsequent experimentation. The specimens were subjected to compression and flexion tests following norm 5833 of the International Organization for Standardization (ISO), with 6 × 12 mm cylindrical blocks (for compression tests) and 75 × 10 × 3.3 mm plates (for flexion tests) as samples. The samples were divided into four groups of 20 specimens each, with 10 for compression and 10 for flexion tests. Three groups were sterilized (autoclave, gamma rays, and ethylene oxide), whereas the fourth group (control) was not. The mechanical tests obtained from the different sterilization processes were compared using analysis of variance (ANOVA, p  < 0.05), followed by the Tukey multiple comparison test of means, with a 95% confidence interval. Results  The specimens presented mean compressive strengths of 10.25 MPa for the control group and 3.67 MPa, 9.65 MPa, and 9.16 MPa after ethylene oxide, gamma ray, and autoclave sterilization, respectively. Flexion test results showed an average resistance of 0.40 MPa in the control group, and 0.15 MPa, 0.17 MPa, and 0.30 MPa after ethylene oxide, gamma ray, and autoclave sterilization, respectively. There were statistically significant differences observed in the maximum compression of the ethylene oxide-sterilized group compared with that of the control group ( p  = 0 . 0002), gamma ray-sterilized ( p  = 0.0003), and the autoclaved ( p  = 0.0006) groups. There was a statistically significant difference in maximum flexion of the specimens sterilized by gamma rays when compared with the control group ( p  = 0.0245). However, low flexural strengths were observed in all specimens. Conclusion  The autoclave sterilization group did not result in statistically significant differences in either compression or flexion strength tests. Thus, the autoclave proved to be the best sterilization option for the hydroxyapatite-based biocomponents in this study.