Effect of Dimethyl Sulfoxide Primer on Microtensile Bond Strength and Micromorphological Pattern of HEMA-free Universal Adhesive to Dry/Wet Dentin After Thermomechanical Aging.

Abstract

To evaluate the effect of dimethyl sulfoxide (DMSO) primer on microtensile bond strength (μTBS) and the micromorphological pattern of a hydroxyethyl methacrylate (HEMA)-free universal adhesive (UA) applied on wet/dry dentin in etch and rinse (E&R) mode before/after thermomechanical aging. For the μTBS test, the mid-coronal dentin of 80 human mandibular first molars was exposed and etched with 35% phosphoric acid. Teeth were randomly divided into two equal groups: dry and wet dentin (n = 40). Then, each group was subdivided according to dentin pretreatment by DMSO before UA (Gluma Bond Universal, Heraeus Kulzer, Hanau, Germany) application into unpretreated and 10% DMSO/water (OT Primer S100, OT Oy Dent, Turku, Finland) pretreated (n = 20). Resin composite blocks were built up using a specially designed Teflon mold. In every subgroup, both the μTBS test and failure analysis by stereomicroscope were evaluated immediately after 24 h and after thermomechanical aging (n = 10). The data were statistically analyzed using a three-way analysis of variance (ANOVA) (p = 0.05). For the micromorphological pattern, 16 maxillary first premolars were distributed as mentioned in the μTBS test, prepared, and buccolingually sectioned. The dentin-resin interface was examined using an environmental scanning electron microscope (ESEM) (n = 2). Three-way ANOVA revealed that the main effects and interactions between dentin wetness, dentin pretreatment, and evaluation time (thermomechanical aging) were not significant for µTBS (p> 0.05). Adhesive failure was the predominant type in all immediate and delayed specimens. Longer and more prominent resin tags were observed at dentin-resin interfaces after DMSO application. Neither the initial dentin wetness condition, dentin pretreatment, nor thermomechanical aging could affect the dentin bond strength. No correlation was found between the bond strength and the micromorphology findings. Key words:Wet/dry dentin bonding, Microtensile bond strength, Micromorphology, Universal adhesive, Dimethyl sulfoxide, Thermomechanical aging.