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

Objectives: To assess amounts of residual dentine retained after using three excavation techniques; the microtensile bond strengths (mu TBS) to residual dentine, comparing etchrinse vs. self-etching adhesives. Methods: 42 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 (TM) 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 mm(2) beams per tooth underwent mu TBS testing/microscopic analysis of fractured surfaces. Three cavities from each excavation group were analysed using SEM. Results: SEM 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 (TM) left affected dentine and SFC-V slightly under-prepared clinically. Mean mu TBS values from etchrinse samples (27 MPa (SD 3.9), hand; 22 MPa (SD 5.1), Carisolv (TM); 26 MPa (SD 4.4), SFC-V) showed statistical differences between hand and Carisolv (TM) groups. Mean mu TBS data for self-etch samples (22 MPa (SD 3.3), hand; 27 MPa (SD 6.1), Carisolv (TM); 25 MPa (SD 4.7), SFC-V) showed significant differences between hand and Carisolv (TM), 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. Conclusions: Data indicated that all null hypotheses were disproved. (C) 2010 Elsevier Ltd. All rights reserved.