[Comparative evaluation of the effect of CPP-ACP and resin infiltration on brown spot color parameters after using 20% carbamide peroxide]

Tooth colored restorations are the commonly used current approach for aesthetic problems associated with brown spots. Considering the importance of conservative dentistry, the aim of this in vitro study was to evaluate the efficacy of color correction using casein phophopeptide amorphous calcium phosphate [CPP-ACP] and resin infiltration after using 20% carbamide peroxide for brown spots in esthetic areas. In this experimental study, 70 humans teeth samples with brown spots were collected. In the first step, 20% carbamide peroxide was applied and then samples were divided into two groups to be treated with CPP-ACP or resin infiltration. Color parameters of the samples were evaluated at baseline, after bleaching, after using infiltration resin and CPP-ACP. Any color shift was measured using spectrophotometer. The results were analyzed by SPSS version 20. For statistical analysis, paired t test, indeipendent t-test and repeated measures ANOVA were used. P value <0.05 was considered significant. After using 20% carbamide peroxide, L[asterisk] and b[asterisk] increased and a [asterisk] decreased significantly [p<0.001]. By using CPP-ACP, decreases in a [asterisk] and b[asterisk] were not significant [p>0.05] but L[asterisk] increased significantly [p<0.001]. Application of infiltration resin caused a significant decrease in a [asterisk] [p<0.001]; however, the decrease in L[asterisk] and the increase in b[asterisk] were not statistically significant [p>0.05]. Comparison of the two groups showed that the degree of color shift [delta E] in brown spots and adjacent sound enamel did not change significantly in the two subgroups [p>0.05]. The results show that for esthetically unfavorable brown spots, using 20% carbamide peroxide with CPP-ACP or resin infiltration can improve the appearance. In general, application of resin infiltration with carbamide peroxide is preferably recommended for improving translucency

[Comparison of gradient AC/A ratio with different deviation measurement techniques]

To compare the effect of different deviation measurement techniques and different lens powers on gradient accommodative convergence to accommodation [AC/A] ratio. We randomly selected 78 eligible students of different majors from Zahedan University of Medical Sciences. Following retinoscopy for refractive errors, alternate prism cover test, von Graefe and Maddox rod without additional lenses and with +/- 1, +/- 2 and +/- 3 D lenses were performed for measurement of deviation at near and determination of gradient AC/A Ratio. Data were analyzed using within subject factorial repeated measurement ANOVA and correlation tests. Mean AC/A ratio was 3.6, 3.7 and 4 prism diopter to diopter using alternate cover test, Maddox rod and von Graefe methods, respectively [P=0.2]. The highest and lowest AC/A ratios were related to von Graefe method with +3D and cover test with -1D lens power, respectively. Only differences between AC/A ratios with -1 and +2 lenses as well as with -1 and +3D were significant [P<0.05]. For all different deviation measurement methods, AC/A ratios with plus lenses were higher than minus lenses. The type of deviation measurement method had no effect on AC/A ratio but selected lens power affected the results. We recommend using 2 or 3 diopter instead of 1 diopter lenses to avoid possible effects of depth of focus