Effect of light-curing time on bond streght and degree of conversión of universal adhesives: preliminary results

Abstract

Objective: To evaluate the effect of different light-curing times on micoshear bond strength and degree of monomer conversion of two universal adhesive systems.

Methods: Two universal adhesives (Single Bond Universal – 3M ESPE and All Bond Universal – BISCO) were analyzed, applied using a self-etch strategy on dentin. Light-curing was performed with an LED lamp (VALO - Ultradent) for 10 or 40 seconds, forming four experimental groups. Bond strength was evaluated by immediate microshear testing on ten third molars per group (MTS SANS). Degree of monomer conversion was determined by infrared spectroscopy (FTIR-ATR), measuring the variation in aliphatic bonds before and after light-curing. For statistical analysis, a two-way ANOVA was performed with a significance level of α=0.05.

Results: In microshear testing, SBU 10s showed significantly lower values than all other groups (p<0.05), which did not differ from each other. Regarding degree of conversion, ABU showed no differences between light-curing times, whereas SBU 40s obtained the highest value, followed by SBU 10s, with both ABU groups showing the lowest conversion and no differences between them. These differences may be related to the distinct composition of each system, including their base monomers and photoinitiator systems.

Conclusions: Preliminary data suggest that the response to light-curing time is material-dependent, influencing both degree of conversion and bond strength. Increasing light-curing time was not detrimental for any group and could be beneficial for some adhesive systems. Future studies should expand the number of materials evaluated and incorporate artificial aging to determine the clinical relevance of these findings.