Figure 1A shows scratches left by the SiC abrasive paper and a regular smear layer over the entire surface, occluding the dentinal tubules. The air abrasion resulted in an irregular selleck chem dentin surface without any patent tubules (Figure 1B). SEM examination of sono-abraded surfaces showed an amorphous layer of debris with completely obliterated dentin tubules (Figure 1C). Laser-treated dentin micromorphology showed lack of smear layer and a very rough, irregular surface. The peritubular dentin is evident around the tubules (Figure 1D). Figure 1 SEM of the prepared dentin surfaces (1A: 600-grit SiC-paper; 1B: air-abrasion with aluminum oxide particles; 1C: diamond sono-abrasion and 1D: laser Er:YAG irradiation) Original magnification 5000X.
Resin-dentin interdiffusion zone and resin tags were noted in all bonded interfaces on which both self-etching and etch & rinse adhesive systems were used (Figures 2A, 2B, 2C, 2D and 2E). The thickness of hybrid layer and the length of resin tags varied according to the dentin treatment and the type of adhesive system applied. SEM of bonded specimens that were treated with the Er:YAG laser showed collar-like structures around resin tags for all bonded interfaces (Figures 2D and 2E). Table 3 shows the failure pattern observed in this study. The most predominant failure patterns on experimental groups were partial cohesive failure within adhesive layer and fracture between adhesive resin and dentin (47% �C 90%) (Figure 3A). Laser-treated dentin tended to fail more cohesively in dentin after testing (Figure 3B). Figure 2 SEM of the bonded interfaces.
Resin-dentin interface of Tyrian SPE/One-Step Plus bonded to dentin treated with SiC paper (2A). Resin-dentin interface of Clearfil SE Bond applied to air-abraded dentin (2B). Resin-dentin interface of Single Bond applied … Figure 3 SEM photomicrographs illustrating fractured surfaces. Fractured dentin-adhesive (Unifil Bond) interface in dentin side (3A) (D-dentin; AL-adhesive layer). Cohesive fracture in dentin for Single Bond adhesive applied after laser irradiation (3B) Original … Table 3 Failure mode (%) of tested specimens. DISCUSSION The null hypothesis for this study had to be rejected. In this study, in order to verify the effects of Er:YAG laser irradiation, air- and sono-abrasion preparation methods on bonding of composite resin to dentin, four adhesive systems were selected.
Although the smear layer removal and the superficial demineralization promoted by the acid etching, the conventional, etch-and-rinse adhesive Single Bond was affected by the type of dentin preparation. This could have happened due to superficial changes promoted Brefeldin_A by surface treatments, modifying the way this adhesive system interacts with treated dentin. Higher bond strength values were observed when Single Bond was applied to SiC-abraded dentin than when it was applied to diamond sono- and laser-treated dentin.