Objective: The objective of this study was to evaluate the biocompatibility of five commercially available orthodontic miniscrews/ temporary anchorage devices. Materials and Methods:A cell culture system using commercially available human gingival fibroblasts was utilized. Miniscrews/ temporary anchorage devices obtained from Ormco, Ortho Organizer, 3M Unitek, American Orthodontics, and Rocky Mountain Orthodontics were immersed in culture medium for either 48 hours or two weeks. The surface area to volume character of the eluates produced by this method was within the suggested ISO range. Gingival fibroblasts were exposed to miniscrew/temporary anchorage device conditioned culture medium for 24 hours. Biocompatibility and cytotoxicity were measured using colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays. Results were analyzed using ANOVA with Tukey's post-test and P < 0.05).Results: LDH analysis showed no differences in disruption of cell membrane integrity, suggesting that the miniscrews/temporary anchorage devices were not cytotoxic to gingival fibroblasts (P > 0.05 for all comparisons). MTT analysis, used to quantify viable cells, demonstrated that 48 hour conditioned medium significantly affected cell viability (P < 0.001 for all treatments compared to control). In contrast two week conditioned medium from all five devices did not affect cell viability compared to control. Conclusion:The results of this study suggest that miniscrews/ temporary anchorage devices demonstrate longer-term biocompatibility with gingival fibroblasts and that the composition of the devices is not cytotoxic to oral cells. The general lack of data regarding the cytotoxicity of miniscrews/temporary anchorage devices in orthodontic treatment warrants further investigation.