Interpreting Population Survey Measures of Periodontal Disease Experience Under Severity-Dependent Tooth Loss

Clinical attachment loss (CAL) measured at retained teeth is used as an indicator of periodontal disease experience. Because CAL can be measured only on teeth present at examination, retained-dentition summaries are conditioned on the observable dentition. Where tooth loss is severity-dependent, severely affected teeth may be preferentially removed from observation, causing these summaries to diverge from cumulative disease experience across the original dentition. We hypothesised that CAL summaries more sensitive to severe attachment loss would show earlier and stronger attenuation at older ages than broader summaries that are less dependent on extreme values.

Using nationally representative data from adults aged ≥ 30 years in NHANES 2009-2014, we examined age-specific trajectories across mean and threshold-based CAL summaries and assessed whether divergence between summaries followed the pattern predicted under severity-dependent tooth loss.

The proportion of sites measured declined from 93% at ages 30-34 to 68% at ≥ 80 years, establishing the structural basis for divergence across CAL summaries. Attenuation increased across higher CAL thresholds: higher threshold extent measures were most affected, while lower threshold measures showed more stable trajectories.

Cross-sectional CAL summaries reflect disease among surviving teeth rather than cumulative damage across teeth originally at risk. Attenuation at older ages is consistent with depletion of severely affected teeth rather than biological slowing. Distortion varies by the measure, with higher threshold and mean-based indices most affected; CAL ≥ 3 mm threshold provides a more stable basis for age comparisons.