RESUMO
OBJECTIVES: To evaluate the effect of application protocol in resin-enamel microshear bond strength (µSBS), in situ degree of conversion, and etching pattern of three universal adhesive systems. METHODS AND MATERIALS: Sixty-three extracted third molars were sectioned in four parts (buccal, lingual, and proximals) and divided into nine groups, according to the combination of the main factors-Adhesive (Clearfil Universal, Kuraray Noritake Dental Inc, Tokyo, Japan; Futurabond U, VOCO, Cuxhaven, Germany; and Scotchbond Universal Adhesive, 3M ESPE, St Paul, MN, USA)-and enamel treatment/application time (etch-and-rinse mode [ER], self-etch [SE] application for 20 seconds [SE20], and SE application for 40 seconds [SE40]). Specimens were stored in water (37°C/24 h) and tested at 1.0 mm/min (µSBS). The degree of conversion of the adhesives at the resin-enamel interfaces was evaluated using micro-Raman spectroscopy. The enamel-etching pattern was evaluated under a scanning electron microscope. Data were analyzed with two-way analysis of variance and Tukey test (α=0.05). RESULTS: In general, the application of the universal adhesives in the SE40 produced µSBS and degree of conversion that were higher than in the SE20 (p<0.01) and similar to the ER mode. The deepest enamel-etching pattern was obtained in the ER mode, followed by the SE40. CONCLUSIONS: The active and prolonged application of universal adhesives in the SE mode may be a viable alternative to increase the degree of conversion, etching pattern, and resin-enamel bond strength.
RESUMO
OBJECTIVE: To investigate the shear bond strength of the nano-filled resin-modified glass ionomer (RMGI) to dentin using different self-etch adhesives. MATERIALS AND METHODS: Two resin-based restorative materials, a nano-filled RMGI (Ketac Nano-100, 3M ESPE) and a restorative composite (Grandio, VOCO) were bonded to bovine dentin using four self-etch adhesives (Futurabond M, VOCO; Adper Easy Bond, 3M ESPE; G Bond, GC Corp; and One Coat, Coltène). One hundred bovine anterior teeth were used in this study. Subsequent to labial enamel removal, each adhesive was applied according to manufacturer instructions. Fifty teeth were restored with the nano-filled RMGI and the other 50 were restored with the resin composite. Cylinders of 3×2 mm from the two restorative materials were bonded to dentin, and the specimens were stored in distilled water for 24 hours. Shear bond strength testing was performed in a universal testing machine at a crosshead speed of 0.5 mm/min. Two randomly selected specimens from each group were chosen for evaluation by scanning electron microscopy (SEM). Failure modes were evaluated using the stereomicroscope. All data for shear bond strength in MPa were expressed as mean ± standard deviation (SD). Statistical analysis was carried out using SAS program (SAS, 1988). RESULTS: Two-way analysis of variance revealed that the adhesives, the restorative materials, and their interactions (adhesives and restorative materials) had a significant effect on the shear bond strength to bovine dentin. CONCLUSIONS: Self-etch adhesives used in this study can adequately bond the nano-filled RMGI to dentin.