RESUMEN
The use of various techniques of teeth bleaching as a conservative and low-cost procedure is common and generally accepted today. The purpose of this study was to evaluate the bleaching effect of sodium perborate mixed with four different concentrations of H[2]O[2] on artificial stained pulpless teeth. In this experimental single-blind study, 64 extracted human premolars were stained in vitro with human RBCs mixed with iron sulfide II, and randomly divided into 4 test groups and one control group. The bleaching agents of sodium perborate mixed with 7.5%, 15% and 30% H[2]O[2] and distilled water were placed in pulp chambers of the teeth. The bleaching effects of each group were evaluated using a digital camera and L*a*b system. Adobe Photoshop 7.0 software was used to measure the color changes through the procedure. Delta E was used to describe color changes numerically. The data were analyzed by Kolmogorov Smirnov, ANOVA and SPSS Ver. 9.0 software. The results revealed that sodium perborate mixed with H[2]O[2] 30% significantly had more whitening effect than the other groups [P=0.001], but there was no significant difference among the bleaching effect of the other groups. The most bleaching effect was gained by H[2]O[2] 30% .On the other hand due to no significant difference between 15% and 7.5% of H[2]O[2] with water, using sodium perborate mixed with water is one of the safest methods in teeth bleaching