# Retrospective Study of the Association between Peri-Implantitis and Keratinized Mucosa
## 3 Results  
A total of 203 implants in 60 patients (19 men and 31 women) were analyzed, of which 100 implants in 25 patients presented peri-implantitis (peri-implantitis group) and 103 implants in 35 patients presented peri-implant health (control group). Fifteen patients were excluded after not meeting these inclusion criteria. Ten of them presented active periodontitis and were not receiving their periodontal support therapy, three had systemic diseases that affected their immune system, and two had not completed the year since the prosthesis placement. The analysis of individual characteristics (gender, age, tobacco consumption) did not reveal any significant differences between the two groups. The mean time from implant placement was 6.7 years in the control group. However, it went up to 12.3 years in the peri-implantitis group, a statistically significant difference (\(p=0.001\)). Most of the implants sampled in this study belonged to patients with multiple implants in their oral cavity. 82% in the peri-implantitis group and 66% in the control group, but the difference between them was not statistically significant. The main characteristics of the patients are enlisted in Table 1. The most common pathologies presented by the patients in both groups were hypertension and hypercholesterolemiaemia, but their influence is not described in the literature. Figure 4: Bone loss. Table 2 presents the descriptive and statistical results which help evaluate whether there is an association between the peri-implantitis and control groups and the variables analyzed. From the total sample (203 implants), 151 implants (74.4%) presented KM. The mean KM value was 2.14 \(\pm\) 1.68 mm, with a range of 0 to 8 mm. Among the implants in the peri-implantitis group, the presence of KM was detected in 51% vs. 97.1% of the implants in the control group. Therefore, the presence of KM seems to significantly reduce the risk of peri-implantitis (OR = 0.03; \(p\) < 0.001). Regarding the amount of peri-implant mucosa, for every 1 mm of KM, the risk of peri-implantitis is reduced by 44% as can be seen in Figures 5 and 6. The mean plaque index was 1.16 \(\pm\) 0.96, being 1.7 in the peri-implantitis group and 0.6 in the control group. A statistically significant association between the plaque index and the peri-implant diagnosis was confirmed (OR = 6.24; \(p\) < 0.001). For each additional degree in the index, the risk of peri-implantitis was more than six times greater. In addition, it was observed that patients whose implants were surrounded by KM had a lower plaque index than those whose implants were not. The mean probing depth was 3.76 \(\pm\) 1.43 mm. There is a significant association between probing depth and KM. The mean probing depth was 5.1 mm when there was no KM and 3.3 mm in the presence of KM, being this difference statistically significant. Of all implants, 59.6% showed bleeding on probing. All the implants in the peri-implantitis group presented bleeding on probing compared to 20.4% of those considered healthy. Of all the implants analyzed, 47% of the implants with KM bled on probing compared to 96.2% in the absence of KM. Regarding suppuration, 27.1% showed suppuration; 55% of the implants in the peri-implantitis group suppurated versus 0% suppuration in the controls. Considering the variable KM, 16.6% of the implants with KM suppurated versus 57.7% when there was no KM. This difference was statistically significant (\(p\) < 0.001). Figure 5: Presence rate (%) and quantity (mm) of keratinized mucosa by Groups. PI (peri-implantitis). Figure 6: Decreased probability of peri-implantitis in terms of mm of keratinized mucosa. PI (peri-implantitis), KM (keratinized mucosa). The mean bone loss was 2.2 \(\pm\) 2.3 mm, ranging from 0 to 9.9 mm and it was significantly higher in patients with peri-implantitis (3.8 \(\pm\) 2.1 mm), since the reduced bone loss in healthy implants (0.5 \(\pm\) 0.6 mm) was attributed to the physiological remodeling produced after implant loading.