Purpose:To study the relevance of dentin moisture state on micro-tensile bond strength (µTBS) and bonded interface morphology when using two universal adhesives with different compositions.
Materials and Methods:Sixty third molars randomly allocated into 12 groups based on adhesive types (Prime & Bond Universal [P&BU], Dentsply Sirona, New York, USA and Single Bond Universal [SBU], 3M ESPE, Neuss, Germany), adhesives application approach (etch and rinse or self-etch), and the amount of moisture on dentin surface(dry, wet & visible moist). Thirty-six molars were divided into beams of adhesive-dentin for µTBS (n=20) after restoration. Twenty-four molars were used to create specimens for scanning electron microscope evaluation of bonded interface (n=2).For statistical analysis,three-way ANOVA was used,followed by multiple comparison with Bonferroni adjustment.
Results:in etch and rinse,P&BU had higher µTBS than SBU when the dentin surface was dry, SBU had higher µTBS when dentin surface was wet.No differences between both adhesives on moist dentin surface.In self-etch,SBU had higher µTBS than P&BU on moist dentin,no significant differences between the two adhesives on dry and on wet dentin surfaces.For both adhesives,SEM images revealed better hybrid layer morphology and integrity with greater number of resin tags and deeper penetration in etch and rinse approach than self-etch.Moist dentin surface developed better interface morphology than dry dentin surface, wet dentin surface had the poorest hybrid layer quality with scarce resin tags in both adhesives.
Conclusion:When dentin was moist or dry, universal adhesive demonstrated good adhesive performance. Universal adhesives are better utilized in etch and rinse approach than the self-etch approach.