Objectives: To investigate the bonding performance of different adhesives to unprepared erosively and/or abrasively altered dentin.
Methods: Dentin samples underwent erosive pH-cycling for five days (6x5min demineralization/ 6x3.5h remineralization per day) and toothbrush-abrasion (2x15 strokes/day), or only toothbrush-abrasion (control), respectively. The micro-tensile bond strength (µTBS) of three different adhesives (Optibond FL [O-Fl], Clearfil SE Bond [C-SE], AdheSE One [A-SE]) was measured after 1-week water storage. Fracture analysis was performed using light microscopy and SEM. Statistical differences were analysed by ANOVA and Tukey-test (a=0.05).
Erosion had a significant effect on bond strength. An 'adhesive' fracture mode was more frequent in the eroded than the control groups. The difference was most prominent for O-Fl, where the µTBS decreased 20 MPa due to pH-cycling. C-SE performed best on eroded surfaces. A-SE showed a low bonding performance in the eroded, but also the non-eroded groups, and was the solely adhesive for which pre-testing failures were recorded.
Conclusions: Erosion highly affected the µTBS of the etch-and-rinse adhesive. After erosion, the highest bond strength was recorded for the 2-step self-etch adhesive. The 1-step self-etch adhesive might not be suitable on unprepared erosively altered surfaces.