Method: UV light-cured circular discs (5 mm) were prepared from Clearfil SE Bond® (SE), Clearfil SE Protect® (PB), Adper Scotchbond SE® (ASE), and Adper Single Bond Plus (ASB+). Conditioned media (CM) were prepared by incubating the discs in DMEM culture medium at 37°C (1 h to 40 days). Normal human gingival fibroblasts and epithelial cells were grown in DMEM and then exposed to CM for 48 h. Toxicity of the CM of each bonding agent was measured by MTT viability assay (Roche Labs). Data analysis: ANOVA and Scheffe’s F procedure.
Result: The four adhesive systems differed in their toxicity. 79% of the cells were viable after exposure to SE 1 h CM, but viability decreased upon exposure to CM of longer periods. PB 1h to 3d CM was toxic but CM of longer periods had no effect. 74% of the cells were viable when exposed to ASB+ 1 h CM, but viability was decreased 20% by ≥7 d CM. On the other hand, ASE ≤ 7d CM was non-toxic, but CM of greater periods decreased viability by 36%.
Conclusion: The study suggests that cellular toxicity for all adhesive systems, in addition to bond strength and microleakage, should be considered when choosing a self-etching bonding agent system in clinical practice.