Pre-study calibration and sample size calculation
PD, tooth
One examiner (AT) unaware of group assignment performed all clinical examinations. Prior to initiation of the study, two separate calibration exercises were performed: 1: Examiner AT was calibrated with an experienced periodontist (KNL) and 2: Examiner AT performed an exercise to assess intra-examiner reproducibility for the primary outcome variables probing depth (PD) and clinical attachment level (CAL). In a study sample of five subjects (100 teeth/600 sites), PD and CAL were examined twice, 10 min apart, at six sites per tooth. Intraclass correlation coefficients (ICCs) were calculated separately for each site. ICC for repeated measures ranged between 0.84 and 0.93 for PD and between 0.82 and 0.95 for CAL.The pre-study sample size calculation was based on change in PD. A difference of 0.5 mm was considered clinically relevant [