Shear Bond Strengths Of A Two-Step Self-Etch Adhesive And A Three-Step Etch-And-Rinse Adhesive In Artificial Dentin Caries Lesions Of Various Depths: An In Vitro Study

Abstract

Background: Minimally invasive caries management philosophy advocates leaving carious dentin as a substrate for adhesive bonding. However, the performance of current resin adhesives in incompletely excavated caries lesions is unknown. Understanding the limitations of bonding to carious dentin is critical for the restoring clinician. Objective: To compare the shear bond strengths of a two-step self-etch adhesive and a three-step etch-and-rinse adhesive to moderate and severe artificial dentin caries. Methods: 96 bovine incisors were prepared and assigned to experimental groups of moderate or severe artificial dentin caries lesions or control groups (sound dentin). Specimens were randomly assigned to a two-step self-etch (Clearfil SE Bond 2) or three-step etch-and-rinse (OptiBond FL) adhesive for bonding to a nanohybrid composite resin. TMR analysis determined lesion depth. Specimens were stored for 30 days in Millipore water (5oC), shear bond strengths were measured, and failure modes observed. Two-way ANOVA with interactions evaluated the effects of adhesive type and demineralization severity on shear bond strength. Failure modes were compared using ordinal logistic regression. A two-sided 5% significance level was used for all tests. Results: Clearfil SE performed significantly better than Optibond FL in both moderate and severe lesions. Both adhesives performed adequately on sound dentin, but poorly in severe lesions. For OptiBond FL, bond strengths were lowest in moderate lesions; failures were predominantly mixed or cohesive within composite resin in both moderate and severe lesions, as well as in sound dentin specimens. For Clearfil SE, bond strengths were lowest in severe lesions; failures were predominantly adhesive in moderate lesions, cohesive within composite resin in severe lesions, and mixed adhesive/cohesive in sound dentin specimens. Discussion: Bonding to demineralized dentin was highly variable for both adhesives. Bonding to sound dentin yielded higher bond strengths. Conclusions: A three-step etch-and-rinse adhesive did not perform better than a two-step self-etch adhesive in this study. A self-etch adhesive may be the better choice when bonding to demineralized dentin. Either adhesive may be acceptable when bonding to sound dentin.