STATISTICAL ANALYSIS
Shapiro-Wilk test was used to check the normality of the data. The data was found to be non-normal. Baseline characteristics between the two groups of retainers were investigated using descriptive statistics. P-values were calculated using Independent t-test and Chi-square test. Due to the ordinal data, the four indices were compared and evaluated between two groups of retainers using Mann Whitney test. SPSS v. 21 was used for all data analysis, and the level of significance for all analysis was set to 0.05.