*2.9. Statistical and Power Analysis*

The Statistical Package for Social Sciences (SPSS) version 21.0 was used to perform statistical analysis. The goodness of fit test was carried out to assess the normality of the data. Unless otherwise specified, the results were shown as mean ± SD of the mean. To assess between-group differences of non-normal data distribution, the Kruskal–Wallis nonparametric test was conducted. Bivariate multiple regression analysis was carried out to evaluate the association between PICF cytokine levels and SPP. A total of 15 patients were required with 25 dental implants per group to attain a power of 90% with a probing depth of 1 mm. To allow a 20% attrition for compensation, a total of 20 patients were selected. A *p*-value of <0.05 was considered statistically significant.

#### **3. Results**

#### *3.1. General Description of Study Participants*

A total of 60 patients (29 males and 31 females) participated in this study and signed the written informed consent and completed the clinical trial. Group-1 and group-2 participants had a mean age of 41.7 ± 6.6 and 39.4 ± 5.8 years, respectively, while the control group had a mean age of 38.2 ± 7.3 years. Among the smokers and never smokers with peri-implantitis, 42 and 36 dental implants were examined, respectively, while 28 dental implants were evaluated among never smokers without peri-implantitis. Among group-1 and group-2, an average of dental implants in service was 37.4 ± 3.2 and 31.6 ± 2.1 months, respectively, while among the control group an average of dental implants in use was 29.9 ± 5.0 months (Table 1).

**Table 1.** Demographics of the study groups.

