Rate of Initial Proximal Caries Lesion Progression in High Caries-Risk Adults

In adults, caries lesions develop predominantly on proximal surfaces; however, evidence regarding the rate of proximal caries progression in this population remains limited. A clearer understanding of the progression rate of proximal caries in adults is essential for establishing appropriate radiographic examination intervals and optimizing the timing of operative interventions.

To evaluate the rate of radiographic progression of initial proximal caries lesions and the factors associated with it.

Serial bitewing radiographs from 105 patients, aged 18-61 years, were retrospectively analyzed for the progression of 364 enamel and outer dentin proximal caries lesions. The interval between baseline and follow-up radiographs ranged from six to 72 months. Lesion progression across study variables was summarized using descriptive statistics. A multivariable generalized estimating equation (GEE)-based Poisson regression model with robust variance estimation was performed to identify factors associated with proximal caries progression, including patient-level variables (age, gender, fluoride varnish exposure, plaque score, BOP score, DMFT, and DMFS) and tooth-level variables (jaw, tooth type, surface, and initial lesion depth), while accounting for clustering of lesions within patients and variable follow-up duration (p < 0.05; 95% CI).

The mean interval between the initial and follow-up radiographs was 19.9 ± 12.6 months (median = 18 months). Caries progression was observed in approximately one-third of the initial proximal lesions (112 lesions; 30.8%). No lesions progressed from enamel to inner dentin, and only 12 of 43 outer dentin lesions advanced to inner dentin. According to multivariable GEE Poisson regression analysis, maxillary lesions exhibited a higher rate of progression than mandibular lesions (IRR 1.52; 95% CI 1.07 - 2.16), and lesions on distal surfaces demonstrated a higher progression rate than those on mesial surfaces (IRR 1.37; 95% CI 1.01 - 1.85).

The rate of proximal caries progression was relatively low. Tooth location (maxillary arch) and distal surfaces were the only significant predictors of lesion progression.