An in vitro evaluation of microtensile bond strengths of two adhesive bonding agents to residual dentine after caries removal using three excavation techniques

ObjectivesTo assess amounts of residual dentine retained after using three excavation techniques; the microtensile bond strengths (μTBS) to residual dentine, comparing etch-rinse vs. self-etching adhesives.Methods42 carious molars were subdivided (N = 21) dependent upon adhesive/composite system (Adper Scotchbond 1XT and Filtek Supreme vs. Filtek Silorane adhesive and composite). Dividing into three (N = 7), dependent upon caries excavation technique employed (hand vs. chemo-mechanical: Carisolv™ gel vs. experimental enzymatic gel (SFC-V)), caries removal was assessed using visual/tactile criteria and in situ autofluorescence (AF) confocal fibre-optic micro-endoscopy (CFOME). Post-restoration/four-week hydrated storage, four 0.9 mm2 beams per tooth underwent μTBS testing/microscopic analysis of fractured surfaces. Three cavities from each excavation group were analysed using SEM.ResultsSEM revealed surface roughness with smear layer occluding tubule orifices in hand-excavated samples and a reduced, variable smear layer for both chemo-mechanical systems. CFOME AF assessment indicated hand excavation left sound dentine, Carisolv™ left affected dentine and SFC-V slightly under-prepared clinically. Mean μTBS values from etch-rinse samples (27 MPa (SD 3.9), hand; 22 MPa (SD 5.1), Carisolv™; 26 MPa (SD 4.4), SFC-V) showed statistical differences between hand and Carisolv™ groups. Mean μTBS data for self-etch samples (22 MPa (SD 3.3), hand; 27 MPa (SD 6.1), Carisolv™; 25 MPa (SD 4.7), SFC-V) showed significant differences between hand and Carisolv™, and hand vs. SFC-V. Failure loci distribution in etch-rinse samples was between dentine–adhesive, within adhesive and within composite whereas self-etch samples exhibited failure predominantly between adhesive and composite.ConclusionsData indicated that all null hypotheses were disproved.