求助下面这个是怎么计算来的呀，看不懂，真是太难了? To detect a difference of 1 mm in probing pocket depths and clinical attachment levels between three treatment groups (α = 0.05, β = 0.20, estimated SD = 5 mm), the number of patients was calculated, and according to calculation, 393 measuring sites in each group were needed. Assuming that each patient had had at least one periodontal pocket, out of six at one of 20 single-rooted teeth, deeper than 4 mm, yielded the number of 20 patients in each group. All together, 193 teeth were included, 65 in the SRP group, 65 in the Er group, and 63 in the NdErNd group. Among 60 patients included in the study, 34 patients (57%) were females and 26 were males (43%), 31–79 years of age (Table 1). Inclusion criteria were a diagnosis of generalized chronic periodontitis [26] w i t h p e r i - odontal pockets of 5 mm or deeper at single-rooted teeth. Exclusion criteria were an active periodontal treatment, intake of antibiotics within the last 12 months, pregnancy, diabetes, and smoking.