Abstract
Dental caries epidemiology has rarely been studied from the life course perspective, and statistical approaches to analysing such data have been little discussed in the dental literature.
Aim: To describe developmental trajectories of dental caries experience in the permanent dentition between ages 9 and 32 years.
Methods: Longitudinal DMFS data from the Dunedin Multidisciplinary Health and Development Study at ages 9, 12, 15, 18, 26, and 32 years were analysed using group-based trajectory analysis (Nagin, 2005).
Results: Some 914 of the original 1037 were included in this study. Three trajectories of cumulative dental caries experience were identified; these were categorised as "high" (~15%), "medium" (~43%), and "low" (~42%). Plotting mean DMFS data for each trajectory group against age showed the mean DMFS scores diverging at an effectively constant rate from age 9. By age 32, the mean DMFS was 5.5 (sd 3.8), 18.6 (sd 7.0), and 42.6 (sd 12.9) in the "low", "medium", and "high" trajectory groups, respectively. All DMFS trajectories were relatively linear, although the plots for the higher trajectories were initially more 's-shaped' than for the lowest group. This effect disappeared following adjustment for the number of tooth surfaces remaining (relative to DMFS) at each age. Participants' childhood SES was strongly associated with trajectory group membership, with proportionally more low-SES people in the medium or high DMFS trajectory groups. There were consistent, marked SES differences in the experience of caries-associated tooth-loss within the trajectory groups.
Conclusions: On average, the caries rate is virtually constant across time for groups of individuals following the approximate same caries developmental trajectory. Trajectory analysis appears to be a useful tool in the investigation of disparities in dental caries experience through the life course.