Longevity of retained deciduous teeth: A retrospective cohort study

Objective

This study aimed to investigate the factors related to the survival of retained deciduous teeth (RDTs).

Materials and methods

RDTs were identified in panoramic X-ray images in 13,516 patients at Nagasaki University Hospital from 2014 to 2018. The survival status of the RDTs was tracked using medical records; survival rates were calculated. The RDTs were divided into two groups: before and after the completion of stable permanent dentition. A shared frailty analysis was performed in each group, estimating hazard ratios and 95% confidence intervals for variables related to survival.

Results

A total of 138 patients (50 male and 88 female participants, 1.02%) had RDTs. The total number of RDTs was 274, with survival rates of 62.48% at 10 years and 53.30% at 20 years. Before the completion of permanent dentition, the longevity of RDTs was associated with two variables: tooth type (anterior/molar) and presence or absence of successive permanent teeth. No variables were associated with RDT survival after permanent dentition was stabilized.

Conclusion

Multiple congenital factors affect the longevity of RDTs before the stabilization of permanent dentition. However, no significant influence was observed based on factors identified retrospectively after the permanent dentition was stabilized.