The objective of this study was to assess how the application mode of a universal adhesive system affects the microshear bond strength (μSBS) of bulk‐fill and conventional composite resins to enamel and dentin in primary teeth.
A total of 80 caries‐free primary second molars were randomly assigned to eight experimental groups ( n = 10) based on the bonding substrate (enamel or dentin), the application mode of the universal adhesive system (etch and rinse [E&R], or self‐etch [SE]), and the type of composite resin used (bulk‐fill or conventional). After bonding the composite resin to enamel or dentin, the μSBS of the bonded composite resins was measured.
The mean μSBS value of bulk‐fill composite resin was significantly higher than that of conventional composite resin for both enamel and dentin substrates, regardless of the application mode ( p < 0.001). An interaction effect between the bonding substrate and the application mode of the adhesive system was observed, indicating a significant relationship ( p < 0.001). The highest μSBS values for primary teeth enamel were achieved using the E&R mode with bulk‐fill composite resin, while for dentin specimens, the SE mode with bulk‐fill composite resin yielded the highest μSBS values. The μSBS of the E&R group was significantly higher than that of the SE group for enamel specimens ( p < 0.001), whereas the μSBS of the SE group was significantly higher than that of the E&R group for dentin specimens ( p < 0.001).
Bulk‐fill composite resin demonstrated higher μSBS in comparison to conventional composite resin. The universal adhesive system exhibited superior performance in the SE mode compared to the E&R mode on primary dentin. Pre‐etching the enamel before the application of the universal adhesive enhanced the μSBS to primary teeth enamel, highlighting the importance of selectively acid etching the enamel of primary teeth.