2.3. Sample Size Calculation
The sample size calculation was made based on the primary outcome, i.e., peri-implant MBL change. Assuming that the mean MBL change may differ up to one mm between the groups with a standard deviation of one mm in each group and accounting for even 30% of possible dropouts during the observation period (five years), the calculation showed that 26 participants should be included in each group, with the type I probability error alpha set at 