Influência do nível de bateria de unidades LED sem fio na intensidade de luz emitida e nas características de cimento resinoso dual utilizado para cimentação de retentores reforçados por fibra de vidro

Abstract

The aim of this study was to investigate the influence of the battery level of different cordless LED units on the emitted light and characteristics of a dual cure resin cement used for luting fiber reinforced posts. First, the light characteristics of the two cordless LED units (Bluephase G2 e Radii Xspert) were checked for all light-curing cycles of the dfferent battery levels. Sixty bovine root canals were endodontically treated, the post spaces were prepared and the roots were randomly divided into the experimental groups (n=10). After surface treatment, the posts were cemented with a self-adhesive dual-cure resin cement, light-cured with different battery levels (100%; 50%; 10%) for the both LED units. Then, roots were sectioned and two disks were obtained from each root third to be submitted to the push-out bond strength test (PBS) and failure pattern analysis. Resin cement specimens (n=5) were obtained to evaluate degree of conversion (DC), simulating the influence of the distinct battery levels and LED units on the resin cement at the different root thirds. The PBS and DC data were analysed using a 2-way ANOVA (light curing unit and battery level) with repeated measures (root canal region) followed by Tukey HSD test (α=.05). The light intensity of the LED units decreased according to reduced battery levels. ANOVA showed significant influence for the all isolated factors: light curing unit (P = 0.003), battery level (P < 0.001) and root region (P < 0.001); and also for interaction between the light curing unit and root region factors (P = 0.013). No difference was found for interaction between light curing unit and battery level (P = 0.173), battery level and root region (P = 0.954), light curing unit, battery level and root region (P = 0.829). The root depth reduced significantly the PBS values for all the tested groups. The cervical region showed the highest PBS values while the apical region had the lowest values. The 100% and 50% battery levels showed significant higher PBS values than the 10% level for both LED units. Mixed failure mode was predominantly found for all groups. The DC showed no significant differences for all the factors, with the resin cement exceeding 60% for all the situations. The light characteristics of cordless LED units can be affected by low battery levels, and although the degree of conversion was not affected for this factor, it has influenced the bond strength. Cordless LED units should be kept with 50%-100% battery levels in order to achieve better properties for resin cements, thus reducing the risk of retention loss for glass fiber posts. The polywave light curing unit tested resulted in better performance for the bond strength in all variables.