Background: Considering the differences in the filler particles between giomer and conventional composite resins and the importance of these fillers in the repair bond strength, the aim was to evaluate the effects of different etching strategies with phosphoric acid (PA) and hydrofluoric acid (HF) on the microtensile repair bond strength (µTRBS) of giomer.
Material and methods: Ten giomer blocks were randomly assigned into 10: 1) control; 2) 37%PA-20s; 3) 3%HF-20s; 4) 3%HF-120s; 5) 9.6%HF-20s; 6) 9.6%HF-120s; 7) 37%PA-20s + 3%HF-120s; 8) 37%PA-20s + 9.6%HF-120s; 9) 3%HF-120s + 37%PA-20s; 10) 9.6%HF-120s + 37%PA-20s. In all groups, the One-Step Plus bonding system was applied and the new giomer block was bonded to the existing giomer. After cross-sectional cutting, 18 samples were prepared from each block and the µTRBS of the samples was measured at a strain rate of 0.5 mm/min. Data were analyzed with one-way ANOVA and post hoc Tukey tests (P<0.05).
Results: The µTRBS in groups 4, 5, 6, 7, 8 and 10 were significantly higher than that in the control group (P<0.05). The µTRBS in group 2 was even less than that in the control group (P<0.001). The highest µTRBS was recorded in group 10, which was significantly different from those in groups 3, 4 and 9 (P<0.05). In addition, the differences between group 9 and groups 6, 7 and 8 were significantly different (P<0.05).
Conclusions: Etching with PA resulted in a decrease in µTRBS. Etching with HF, except for 3%HF-20s and HF after etching with PA, resulted in a significant increase in giomer`s µTRBS. An increase in the application time of 3%HF resulted in a significant increase in the µTRBS. Key words:Dental restoration repair, Hydrofluoric acid, Phosphoric acid, etching.