The prevalence and severity of root surface caries across Australian generations

Background: The “failure of success” theory predicts that as subsequent generations of older adults retain more teeth, those additional teeth will experience more oral disease like root surface caries. The theory in relation to root surface caries has never been tested in a cross-generational study. This study aims to compare root surface caries across generations of South Australian older adults to test the theory and explore risk indicators for root surface caries. Methods: Data were from the baseline of two South Australian studies separated by 22 years. In both studies, stratified random samples of people aged 60+ years from Adelaide and Mount Gambier were recruited. Dental examinations were performed by trained and calibrated dentists. One of the dental examiners from the earlier study was the gold standard examiner in the second study. Risk indicators included behavioural factors, clinical oral conditions, sociodemographic and socioeconomic status. Root surface caries was assessed as untreated root surface caries (root decayed surfaces [RDS]), treated root surface caries (root filled surfaces [RFS]) and treated or untreated root surface caries (root decayed and filled surfaces [RDFS]) and was presented as the prevalence and summed count. Multivariable models for Poisson and negative binomial distributions were used to estimate prevalence ratios (PR) and mean ratios (MR), respectively, and their 95% confidence intervals (95% CI). Results: The current generation of South Australian older adults has significantly lower RDS (PR [95% CI] = 0.65 [0.47-0.89]; MR [95% CI] = 0.51 [0.35-0.73]) and RDFS (PR [95% CI] = 0.84 [0.71-0.99]; MR [95% CI] = 0.76 [0.65-0.90]) than the previous generation. The RFS in the previous and current generation was similar. Gingival recession, irregular brushing, dental visiting for a problem and smoking were the indicators for RDS, while age, gingival recession, tooth brushing frequency, time since last dental visit and reason of visiting were the indicators for RFS or RDFS. Conclusions: These results do not support the “failure of success” theory in relation to root surface caries among South Australian older adults. Despite the higher number of teeth retained, the current generation of older adults has less root surface caries than the previous generation. Behavioural factors remain the indicators of root surface caries across the generations.