The calculation of the sample size was conducted with the statistical software G-Power 3.1 applying the chi-square homogeneity test. Identical sample sizes were considered for the aPDT group and the sham group. The percentage of type error was set at 5% and the statistical power at 80%, obtaining n = 30 considering 10% losses. The distribution of data within each group and the homogeneity of the variants will be verified for the choice of an analysis of variance or not. With this information the most proper statistical test will be conducted. The sample size calculation is based on the literature and a 5% significance level will be adopted