The influence of various light curing units on the cytotoxicity of dental adhesives

ObjectivesThe objective of this study was to test the hypothesis that various light curing units (LCUs) have an influence on the cytotoxic action of adhesive systems.MethodsSamples of the dental adhesives (Syntac®, iBondTM, Clearfil™ Protect Bond, Prime & Bond™ NT, Adper™ Prompt™ L-Pop™) were prepared in microwell plates, making use of the LCUs Voco Polofil Lux (VPL), EMS Swiss Master Light® (SML) and the LED prototype developed by the IMT of Jena University. To obtain extracts, the samples were topped with cell culture medium, which was changed daily on the 1st to 7th days and then on the 14th, 21st and 28th day, and stored for further use at −20 °C. Human gingival fibroblasts (HGFs) were cultivated in the extract-containing medium for 48 h. The viability of the HGFs was determined by the neutral red (NR) uptake test. The statistical test was performed by one-way ANOVA according to Bonferroni.ResultsDuring the first few days, reduction of the viability rates of the HGFs by 85–90% were observed in all adhesives. A rise up to a plateau phase was observed at different times depending on the materials. The influence of the LCUs on the cytotoxic action of the dental adhesives was clearly evident for the adhesives Syntac® and Clearfil™ Protect Bond. In case of the Syntac® extracts, cytotoxicity after polymerization with the VPL was statistically significant reduced compared to the other LCUs used (p < 0.001). A comparison between all the adhesives used proved that Adper™ Prompt™ L-Pop™ and Prime & Bond NT® had the lowest overall cytotoxicities.SignificanceIn practice, one should use combinations of dental adhesive and LCU in which the material has the least toxic influences.