Influence of the keratinized mucosa on the stability of peri-implant tissues and brushing discomfort: A 4-year follow-up study

Objective The purpose of the present prospective follow-up study was to evaluate the long-term influence of the peri-implant keratinized mucosa (KM) on marginal bone level (MBL), peri-implant tissues health, and brushing discomfort. Material and Methods Eighty patients were initially recruited during their maintenance visit from January to October 2013 and allocated in two groups according to KM width around implants: Wide Group (KM >= 2 mm) and Narrow Group (KM < 2 mm). In the four-year follow-up examination (T4), marginal bone level (MBL), modified plaque index (mPI), probing depth (PD), clinical attachment level (CAL), bleeding on probing (BoP), and brushing discomfort (BD) were reassessed and compared to the initial assessments (T0). Mann-Whitney, Wilcoxon signed-rank test, and a multilevel model were used for the statistical analysis. Results Fifty-four patients with 202 implants returned at T4. Mean mPI (0.91 +/- 0.60), BoP (0.67 +/- 0.21), and BD (12.28 +/- 17.59) were higher in the Narrow Group than in the Wide Group (0.54 +/- 0.48, 0.56 +/- 0.26, and 4.25 +/- 8.39, respectively). Marginal bone loss was higher in the Narrow Group (0.26 +/- 0.71) than in the Wide Group (0.06 +/- 0.48). Multilevel analysis suggested that KM width and time in function had a statistically significant effect on MBL. Conclusions The findings of the present study indicate that KM width had an effect on MBL, plaque accumulation, tissue inflammation, and brushing discomfort over the studied period. Thus, the presence of a KM >= 2 mm around implants appears to have a protective effect on peri-implant tissues.