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).
Results:
Table: µTBS (MPa).
ADHESIVE
| EROSION+ABRASION
| ABRASION (CONTROL)
| |||||
n
| ptf
| µTBS | % µTBS control
| n
| ptf
| µTBS
| |
O-FL
| 30
| 0
| 10.9(±5.0)3,4 | 27.3
| 31
| 0
| 39.8(±12.1)1 |
C-SE
| 32
| 0
| 16.3(±11.4)3 | 58.2
| 32
| 0
| 28.0(±12.4)2 |
A-SE
| 30
| 10
| 5.3(±6.1)4
| 49.5
| 30
| 1
| 10.7(±9.6)3,4 |
n=number of specimens; ptf=pre-testing failures; groups with the same superscript are not statistically significantly different; '% µTBS control' indicates the proportional µTBS in % of the mean control µTBS.
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.