Efecto de mezclas experimentales para blanqueamiento interno preparadas con perborato de sodio o percarbonato de sodio y diferentes vehículos sobre las propiedades mecánicas de la dentina coronal

This study evaluated the effects of experimentally prepared internal bleaching mixtures containing sodium perborate (SP) or sodium percarbonate (SPC) combined with distilled water (DW) or 20% hydrogen peroxide (HP) on maximum failure load, fracture pattern, and dentin microhardness. Fifty endodontically treated bovine incisors were distributed into five experimental groups (n=10): CO-RE (control restored with composite resin), SP-DW, SP-HP, SPC-DW, and SPC-HP. After two intracoronal bleaching sessions, the specimens were immediately restored with composite resin and subjected to maximum failure load testing and fracture pattern analysis. For microhardness evaluation, fifty bovine dentin specimens were submitted to the same bleaching protocols and assessed using the Knoop microhardness test. Data were analyzed using ANOVA and Tukey’s test at a significance level of 5%. The SP-HP and SPC-HP groups exhibited the lowest maximum failure load values and the greatest reduction in dentin microhardness, differing significantly from the remaining groups (P<0.05), while no differences were observed between them (P>0.05). In contrast, the CO-RE, SP-DW, and SPC-DW groups showed similar maximum failure load and microhardness values (P>0.05). Non-complicated fractures predominated in all groups. Internal bleaching protocols associated with hydrogen peroxide reduced maximum failure load and dentin microhardness regardless of the bleaching agent used, whereas protocols employing distilled water preserved the mechanical properties of the dental structure, with similar behavior observed for sodium perborate and sodium percarbonate.