Methods: Dentin samples were obtained from twenty-seven healthy molars and randomly divided into three groups, with different adhesion strategies: G1-etch-and-dry technique, Scotchbond Universal (3M ESPE-Seefeld, Germany), G2-2-step etch-and-rinse technique, Scotchbond Universal (3M ESPE-Seefeld, Germany), G3-3-step etch-and-rinse technique, Adper™ Scotchbond™ Multi-purpose plus (3M ESPE-Seefeld, Germany). Filtek Z250 (3M ESPE-Seefeld, Germany) was the restorative material. Each group was divided into three subgroups (n=3), according to the laboratory procedure: First subgroup-control; second subgroup submitted to thermal fatigue (10000 cycles/30s/5º-55ºC); third subgroup submitted to thermal fatigue + pressure (15 pressure cycles, 0-3 atmospheres). Samples were stored in a drying oven for 24 hours and subsequently cut with a diamond blade at low speed, in X and Y directions, in order to get sticks with a 1±0.2 mm2section. Microtensile bond strengths (MTBS) were tested in an universal testing machine at a constant crosshead speed of l mm/min. Inferential statistics analysis was performed at a 10% significance level. One-way ANOVA and the Chi-square test were used.
Results: None of the adhesives showed statistically significant variations in terms of MTBS upon being submitted to thermal fatigue only, or to thermal fatigue and atmospheric pressure variation.
Control Mean (SD) (MPa) |
Thermocycling Mean (SD) (MPa) |
Thermocycling + Atmospheric pressure Mean (SD) (MPa) |
Sign. | |
| G1 (etch-and-dry) | 37.49 (20.04) | 42.93 (20.11) | 42.37 (19.88) | 0.245 |
| G2 (etch-and-rinse 2) | 39.57 (19.72) | 41.94 (24.71) | 37.58 (23.94) | 0.538 |
| G3 (etch-and-rinse 3) | 27.26 (15.10) | 26.34 (18.60) | 28.27 (15.54) | 0.803 |
Conclusion: Atmospheric pressure variation had no influence on the adhesion of the different adhesive systems to dentin aged with 10000 thermocycles