Surface-specific distribution and co-occurrence patterns of dental caries in adults: an ICDAS-based analysis

Adult dental caries is not randomly distributed, yet surface-level clustering and co-occurrence patterns remain incompletely described. A retrospective cross-sectional survey was conducted on 987 adults (mean age 40.0 ± 14.1 years, range 18–94) treated between 2020 and 2022. Clinical and radiographic records were coded using ICDAS and reported with a combined A/B/C scheme (A: 1–2, B: 3–4, C: 5–6); patient-level caries experience was summarized using DMFT. Secondary caries lesions were recorded but were not included in the analytical models, which focused exclusively on primary caries. Distribution was evaluated by tooth group, surface, and jaw using descriptive statistics and heat maps. Group comparisons used chi-square tests, and right-left symmetry was assessed with Wilcoxon signed-rank and McNemar tests. Co-occurrence patterns were assessed with association rule analysis (Apriori algorithm; support, confidence, lift) and visualized with network analysis. Overall, 77.1% of surfaces and 54.4% of teeth were sound; primary caries (ICDAS A-C) accounted for 8.2% of surfaces and 22.8% of teeth. Mean DMFT was 11.8 (D 5.9; M 2.1; F 3.7). No right-left difference was detected (Wilcoxon p = 0.18; McNemar p = 0.56). Caries burden differed between jaws (χ² = 402.3; p < 0.001), with more decayed teeth in the maxilla than the mandible (56.4% vs. 43.6%). Among manifest lesions (ICDAS B + C), molars accounted for 58.5% of decayed teeth (first molars 29.5%; second molars 29.0%), with occlusal and approximal surfaces most frequently affected. Anterior-only involvement was uncommon (2.6%); combined anterior and posterior involvement occurred in 29.3%, and posterior involvement was inversely associated with anterior caries (OR = 0.19; 95% CI 0.09–0.38). Approximal lesions were strongly associated with concomitant occlusal involvement (77.9%; OR = 3.52; 95% CI 3.14–3.94). The strongest co-occurrence was observed for opposing mandibular molars (37–47; 27.5% of patients; lift = 1.41). Adult dental caries demonstrates a non-random distribution with pronounced posterior and segment-level clustering, particularly involving molar occlusal and approximal surfaces, with consistent bilateral and adjacent co-occurrence patterns.