Method: One cervical V-shaped preparation (3mm×2mm×1.5mm, occlusal margin in enamel, cervical margin in dentin) was cut in each of 40 extracted premolars and maxillary anterior teeth using a FG-245 carbide bur, in high-speed with abundant water refrigeration. Each bur was used for five preparations and discarded. Specimens were equally and randomly assigned to one of four groups (n=10): CP - One Coat Self-Etching Bond (Coltene), selective etching mode (SE) + Componeer Class V (Coltene)+Synergy D6 (Coltene) composite resin; SYN - One Coat Self-Etching Bond (Coltene), SE + Synergy D6 (Coltene) composite resin; FLO - Scotchbond Universal Adhesive (3M ESPE), SE + Filtek Supreme Ultra Flowable (3M ESPE); TET – ExciTE (Ivoclar-Vivadent), total-etch + Tetric EvoCeram (Ivoclar Vivadent) composite resin, all as per the respective manufacturers’ instructions. Impressions were taken with light-body VPS (Affinis Precious, Coltene). The teeth were then subjected to thermo-mechanical fatigue (one-million cycles, 5-55±2oC/30s each, intermittent axial force of 50 N at 2 Hz). New impressions were taken with light-body VPS. All impressions were poured with epoxy resin (Epo-thin, Buehler Ltd) and observed under a FESEM (Hitachi). Image J (NIH) was used to measure marginal gaps. Statistical analyses (SPSS 18.0, IBM SPSS) - Kruskal-Wallis non-parametric test, p<0.05.
Results:
% of gaps
|
CP |
SYN |
FLO |
TET |
Occlusal |
1.12±3.5
|
0.76±2.4 |
1.84±3.9 |
3.41±4.4 |
Cervical |
1.03 ± 3.6
|
0.95±2.7 |
0.98±2.5 |
3.24±4.2 |
Gap width (μm) |
CP |
SYN |
FLO |
TET |
Occlusal |
0.27±0.9
|
0.23±0.7 |
0.86±1.9 |
0.62±0.9 |
Cervical |
0.11 ± 0.3
|
0.32±1.1 |
0.24±0.8 |
0.87±1.3 |
Conclusion: Although there was a tendency for fewer and narrower marginal gaps for groups CCV and SYN, no statistical differences were found for any of the parameters tested, p>0.05.