Study of cellular toxicity in vitro of two resins for orthodontic use.

The objective of this work is to compare cellular toxicity in vitro of two resins for orthodontic use: an auto-polymerizable composite and a photo-polymerizable composite. Samples were obtained by joining a couple of steel orthodontic brackets by using auto-polymerizing or photo-polymerizing resin. We used a halogen lamp, a mini LED lamp and a fast LED lamp used for orthodontics cure for 40 seconds. The 3T3 Swiss cellular line of fibroblasts was used. The samples obtained were used to determine the cellular toxicity in vitro using the Neutral Red Up-take (NRU) and the 3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Toxicity of the extract appraised at a low level at MTT and NRU assays. There were statistically relevant differences between the toxicity induced by the auto-polymerizing material and the toxicity induced by the photo-polymerizing composite material, polymerized with the blue-light lamp (p < 0.001) and with the mini LED lamp (p < 0.05). From the data collected in this study, we can conclude that both resins show a low level of cytotoxicity that, in the case of photochemical polymerizing resin, depends on the characteristics of the lamp.