Biocompatibility of Two Orthodontic Alloys in Rat Subcutaneous Connective Tissue

Objectives: In orthodontic therapy, different materials are used and subjected to a damp oral environment which can modify their properties. The purpose of this study was to evaluate the in vivo biocompatibility of stainless steel and nickel titanium alloys, implanted in rat connective tissue. Methods: Twelve white female rats were used. Five sites were marked on the dorsal subdermal connective tissue of each rat, then two stainless steel pieces each one centimeter long were implanted in the right side and two nickel titanium pieces each one centimeter long were implanted in the left side and finally one controll site was placed between them, in the controll site an incision was made the same way as before without implantation and then sutured. The implants were removed after 15, 30 and 60 days, fixed, and then histologically prepared for microscopic evaluation. The tissue reactions were located according to the inflammation assessment chart. Results: After data analysis,there were no significant differences between the controll group and the nickel titanium group at the three intervals. In the stainless steel group, significant inflammatory reactions were observed on the 30th day, but no significant differences were noted on the 15th and 60th days. Conclusions: This study suggests that under these experimental conditions these alloys can be considered non cytotoxic. However the results of this research indicates that tissue biocompatibility of stainless steel varies at various times. Consequently, in order to obtain more accurate results, further researches with more accuracy are necessary.