The impact of supportive periodontal therapy on the progression of molar furcation involvement: a time-to-event retrospective analysis

Objective: To determine the association between the frequency of supportive periodontal therapy (SPT) and the time to progression of initial Class I and Class II molar furcation involvements, using a time-to-event analysis that accounts for clustered data. Method and materials: This retrospective cohort study utilized electronic health records from the multi-center BigMouth network (2011 to 2022). The analysis was conducted at the tooth level. Molars with an initial Class I (N = 311) or Class II (N = 154) furcation were followed over time. The exposure was SPT frequency, categorized as regular (≥ 2 visits/year) or irregular (< 2 visits/year). The primary outcome was time to furcation progression (Class I to II, or Class II to III). Mixed-effects Cox proportional hazards models were used to analyze the data, accounting for the clustering of teeth within patients and variable follow-up times. Models were adjusted for baseline furcation grade, patient demographics, smoking, diabetes, hypertension, full-mouth plaque and bleeding scores, and tooth-level clinical parameters. Results: The incidence of progression for Class I furcations was 8.1 per 100 tooth-years in the irregular SPT group versus 5.9 in the regular SPT group. For Class II furcations, the incidence was 11.2 per 100 tooth-years (irregular) versus 6.8 (regular). After multivariable adjustment, regular SPT was significantly associated with a reduced hazard of progression for both Class I (hazard ratio [HR] = 0.51, 95% CI 0.28– 0.92) and Class II (HR = 0.47, 95% CI 0.22–0.99) furcations. Conclusions: In this time-to-event analysis, adherence to a regular SPT schedule of at least two visits per year is significantly associated with a longer time to progression for molars with initial Class I and Class II furcation involvement. These findings provide quantitative evidence that clinicians can use to emphasize the critical importance of consistent, biannual SPT for preserv ing the stability of these high-risk teeth.