Cytotoxicity of an experimental light-cured orthodontic adhesive

The objective of this study was to compare the cytotoxicity of a domestically-made light-cured orthodontic adhesive to a commercial adhesive, Transbond XT (3M Unitek, USA). An in-house orthodontic adhesive composed of a filler 60-70 weight % and a monomer ratio (BisGMA:TEGDMA) of 6:4 with 0.5% of photoinitiator was mixed. The potential cytotoxic effect of this experimental and a control adhesive was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay according to ISO 10993-5: 2009(E). The L929 cell line was grown in 96-well tissue culture plates (1x10⁵ cells/mm³ ). Thin cured-resin discs of each material weighing 0.4 gram were prepared and incubated for 1, 3, 5, 7, 14, and 30 days in Dulbecco’s modified Eagle medium (DMEM) at 37˚C and 95% humidity with 5% CO₂. The percentage of cell viability was reported by descriptive statistics. The result showed that the cell viability of the experimental adhesive was higher than Transbond XT in all measured periods. The cytotoxicity of both the adhesives gradually decreased with the progression of time. In conclusion, the in-house adhesive showed a good biocompatibility since the first day following polymerization. On the other hand, Transbond XT started with a cytotoxic potential, then, turned to be non-cytotoxic after 5 days of curing.