Biocompatibility of eight different orthodontic materials: in-vivo rat model study

Different materials are used in orthodontic treatments. These materials are subjected to damp oral environment which can modify their properties. The purpose of this study was to evaluate the in-vivo biocompatibility of eight orthodontic materials, which were implanted in rat connective tissues. Through an interventional experimental study, the biocompatibility of eight clinically used materials were evaluated. These materials were composed of two coil springs (S.L.S and NiTi), two glass ionomer cements (Bandtate and Ariadent), two O-ring (American ortho and Pooyan tebbe nour) as well as two orthodontic acrylic resins (Acropars and Bayer). Ninety-six white female rats were included in the study. Five sites were marked on the dorsal subdermal connective tissue of each rat, and then two pieces of each material measured at one centimeter long were implanted in the right side and two pieces of another material on the left. Also a similar incision was made at the two other marked sites, and then sutured, without inserting any material. Biopsies were taken from the specified sites, 15, 30 and 60 days following implantation. Tissue reactions were reported after microscopic evaluation, using the inflammation assessment chart. Non-parametric tests such as Kruskal-Wallis and Mann-Whitney tests were used for data analysis. This study demonstrated biocompatibility of acrylic resins and O-rings in the 15- and 30-day experiments. In the glass ionomer cement biopsies significant inflammatory reaction was detected In the 60-day experiment. Significant biocompatibility difference was observed between the coil springs groups (S.L.S-NiTi) and controls In the 30 and 60-day experiments. This study suggests that coil springs and glass ionomer cements can be considered as cytotoxic materials. Although, further studies are recommended in order to support these findings.