Diederik Hentenaar

88 Chapter 4 (BoP, SoP, Plq, PPD and MBL) were also analysed using GLMM, whilst taking the multilevel structure into account. Differences in full mouth periodontal outcomes and midbuccal recession between groups were analysed using an independent samples t-test. A paired samples t-test was applied to analyse differences in overall mean full mouth periodontal outcomes before and 12 months after therapy. The log-transformed mean peri-implant and periodontal microbiological outcomes were analysed at T12 using a Mann-Whitney U test for microbiological between-group differences. A Wilcoxon signed rank test was used for within-group differences. The data collected at baseline, 3, 6, 9 and 12 months are presented with descriptive statistics (see Table 2). RESULTS The flow of patients throughout the study is depicted in Figure 1. A total of 62 patients were screened for eligibility. Four patients declined to participate after which 58 patients (mean age 58.9 ± 11.7, male N = 25, female N = 33) were randomized over the test and control group. Between baseline and 12 month follow-up, 22% of the patients and 18% of the implants (5 patients (7 implants) in the test group and 8 patients (10 implants) in the control group) discontinued the study, all due to implant removal because of persisting peri-implantitis. In total, 27 patients (n = 54 implants) in the test group and 31 patients (n= 40 implants) in the control group were available for analysis. The overall baseline patient and implant characteristics are shown in Table 1. The clinical and radiographical peri-implant outcomes and periodontal full mouth scores are shown in Table 2. In Table 3, the unstandardized β coefficient and significance levels for the mean difference in BoP, SoP, Plq, PPD and MBL between the control and test group during follow-up are presented. The distribution of sites with BoP in implants with PPD < 5mm, without suppuration and without progressive bone loss > 0.5mm is shown in table 4. The prevalence of patients positive for the selected marker species for peri-implant and periodontal samples (in partial edentulous patients) are presented in figure 2 and 3. Both treatments went uneventful; no cases of emphysema after air- polishing therapy were reported. Primary outcome No statistical significant difference was found between the test and control group over 12-month time for mean BoP, neither in the crude nor in the adjusted analysis (Table 3). Within both groups a significant reduction in mean BoP was seen between baseline and 12-months follow-up (test group: p < 0.001 and control group: p = 0.042) (Table 2).