No abstract

Background:Bleaching treatments decrease shear bond strength between orthodontic brackets and teeth; although definite results have not been reported in this regard.Objectives:This study determined the effects of different bleaching protocols on the shear bond strength of orthodontic brackets to teeth.Materials and Methods:This experimental study was performed in Iran. Forty-eight extracted human premolars were randomly assigned into four groups. In the control group, no bleaching treatment was performed. In groups 2 - 4, the bleaching procedures were performed using carbamide peroxide 45%, carbamide peroxide 20% and diode laser, respectively. Two weeks later, brackets were bonded to teeth and thermocycled. The shear bond strengths of the brackets to the teeth were measured. Data was analyzed by one-way ANOVA and Dunnett post-hoc test.Results:Shear bond strength of the brackets to the teeth were 10.54 ± 1.51, 6.37 ± 0.92, 7.67 ± 1.01 and 7.49 ± 1.19 MPa, in groups 1 - 4, respectively. Significant differences were found between control group and all other groups (P < 0.001); and also between groups 2 and 3 (P < 0.05). No significant differences were found between the other groups.Conclusions:The bleaching procedures using 20% carbamide peroxide and 45% carbamide peroxide and diode laser significantly decreased shear bond strength of brackets to the teeth. 45% carbamide peroxide had a more significant effect on bond strength compared to 20% carbamide peroxide. The difference in bond strength was not significant between laser group and either carbamide peroxide groups.

We were interested to read the paper by Witkowski S and colleagues published in the June 2012 issue of Clinical Oral Investigations. The authors' aim was to evaluate the accuracy and reproducibility of human tooth shade selection using a digital spectrophotometer. They report the mean colour difference from the mean metric for measurement precision (reliability)! Also, least square test was used to assess inter-and intra-observer reliability [1]. Why did the authors not use well-known statistical tests for reliability analysis such as intra-class correlation coefficient for quantitative variables, weighted kappa for qualitative ones [2][3][4][5] or other methods such as coefficient of variance for repeatability [2][3][4][5], considering that the mean of the variables and using paired t test, least square test or correlation coefficient (r) are among the common mistakes in reliability analysis [2-5]? Regarding reliability or agreement, it is good to know that not only avoiding common mistakes in reliability analysis but also taking into account clinical importance instead of statistical significance is a crucial issue in clinical reliability researches [2][3][4][5].The authors computed the confidence interval (CI) value 5.23 (4.66-5.86) to represent the accuracy (validity) of the measurements! As the authors point out in their conclusion, the accuracy and reproducibility of dental shade selection using the tested spectrophotometer with respect to examiner and illumination conditions reflected the reliability of this device [1]. A narrow CI has nothing to do with accuracy. We have seven well-known statistical tests for validity (accuracy) analysis, as follows: sensitivity, specificity, positive predictive value, negative predictive value, likelihood ratio positive (LR+), likelihood ratio negative (LR−) and finally odds ratio [2][3][4][5]. Briefly, accuracy and precision (validity and reliability) are two completely different methodological issues in clinical researches, having their own statistical tests, and should not be confused with each other; otherwise, misdiagnosis, mistreatment and mismanagement of the patients will be the result of such researches.

No abstract

No abstract