RESUMO
BACKGROUND: Despite widespread clinical uses of resin-modified glass-ionomers (RMGIs), their sealing ability is still a concern. This study evaluated the effect of delayed light activation (DLA) of RMGI on marginal sealing in differently pretreated cavities. MATERIALS AND METHODS: In this in vitro study, two standardized Class V cavities were prepared on the buccal and lingual surfaces of 56 sound maxillary premolars at the cementoenamel junction. The cavities were randomly divided into eight equal groups. In groups 1-4 (immediate light activation [ILA]), no pretreatment (negative control [NC]) and three surface pretreatments were used, respectively as follows: Cavity conditioner, Vitremer primer, cavity conditioner plus and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP). Fuji II LC (GC, Japan) was prepared and placed in the cavities and immediately light-cured according to manufacturer's instructions. In groups 5-8 (DLA), the same pretreatments were applied, respectively. After placing Fuji II LC in the cavities, the restorations were light-cured after a 3-min delay. After finishing the restorations, the specimens were placed in water for 1-week and thermocycled. Microleakage scores were determined using the dye penetration technique. Kruskal-Wallis test and Mann-Whitney U-test were used to analyze the obtained data (α = 0.05). RESULTS: At the dentin margins, DLA resulted in a lower microleakage for no treatment (NC), cavity conditioner and cavity conditioner plus ACP-CPP pretreatments groups (P ≤ 0.004); however, no difference was observed for Vitremer group (P > 0.05). At the enamel margins, no difference was observed between DLA and ILA for all groups (P > 0.05); only NC group exhibited a lower microleakage in case of DLA (P = 0.007). CONCLUSION: Delayed light activation of RMGI may lead to different effects on marginal sealing, depending on pretreatment procedures used in the cavity. It might improve dentin sealing when no treatment and conditioner alone or with CCP-ACP is used.
RESUMO
OBJECTIVE: This study evaluated the effect of superpulse CO2 laser irradiation and deglazing of porcelain surfaces on the shear bond strength (SBS) of metal orthodontic brackets, and compared it with two conventional etching techniques. METHODS: Forty-eight Feldspathic porcelain fused to metal specimens embedded in cylindrical acrylic resin tubes were fabricated, and all the specimens were divided into four groups. In Group 1, the specimens were roughened with a diamond bur and etched with hydrofluoric acid (HFA) gel for 4 min. In Group 2, the specimens were roughened with a bur and irradiated by a CO2 laser with a 2 W power setting for 20 sec. In Group 3, the specimens were only irradiated by a CO2 laser. In Group 4, the porcelain surface was sandblasted with 50 µm aluminum oxide. Before bonding, the bracket silane was applied on the porcelain surfaces. SBS was evaluated by a Universal testing machine (Zwickroll, Germany). The remaining adhesive after the bond failure was evaluated using an adhesive remnant index (ARI). Statistical analysis was conducted by analysis of variance (ANOVA), Tukey, and Kruskal-Wallis tests. RESULTS: ANOVA revealed significant differences in SBS among the four groups (p<0.001). Group 1 demonstrated significantly higher bond strength (13.13±2.47) when compared with the other groups. Group 2 showed higher bond strength (9.60±1.91) when compared with group 4 (6.40±1.67) (p=0.016). Group 1 displayed the highest ARI scores among the groups. CONCLUSIONS: Deglazing combined with HFA etching produced the highest bond strength, but CO2 laser irradiation provided adequate bond strength and allowed for elimination of the HFA step. Deglazing is not recommended as a preliminary step before CO2 laser conditioning.
