Vertical subclassification predicts survival of molars with class II furcation involvement during supportive periodontal care

BackgroundFurcation involvement is a major predictor of tooth survival. Focus has so far been on the predictive value of the horizontal component of furcation involvement. Residual periodontal support on each of the roots is likely to play a major role on retention of the furcated molar. Aim of this clinical audit study was to preliminarily assess the impact of vertical subclassification on tooth retention. MethodsTooth retention of class II furcated molars in 200 consecutive patients compliant with periodontal supportive care for a minimum of 10years was retrospectively evaluated in a single practice. Randomly selected furcated molars were retrospectively diagnosed in terms of vertical subclassification (residual periodontal support on the most compromised root), and time to tooth extraction/loss was determined in clinical records. Kaplan-Meier survival curves were constructed. ResultsTen-year survival of molar with class II furcation involvement was 52.5%. Survival was 91% for subclass A, 67% for subclass B and 23% for subclass C. Mean years of survival were 9.5-10.1, 8.5-9.3 and 6-7.3 for subclasses A, B and C, respectively. Tests of equality of the survival distributions showed highly significant differences in all portions of the curve (p<.001). Stratified analyses by smoking showed significant differences for the two groups (p<.001). Hazard rates for tooth extraction/loss were 4.2 and 14.7 for subclasses B and C, respectively. ConclusionsResidual periodontal support assessed as vertical subclassification of furcation involvement seems to be a good predictor of survival of molar with class II horizontal furcation. This has implication for prognosis, treatment planning and development of effective molar retention strategies.