Study-Specific Morphological Signs of Non-Carious Tooth Surface Loss in Second Permanent Molars and Caries Experience in a Clinical Sample of Adolescents from Southwest Romania: A Multicenter Cross-Sectional Study.

Background/Objectives: Morphological signs of non-carious tooth surface loss are clinically heterogeneous, and their prevalence depends strongly on the diagnostic framework and threshold used. This exploratory secondary analysis evaluated a study-specific combined morphological outcome restricted to second permanent molars and its association with cumulative caries experience in a regional clinical sample of adolescents. Methods: The analysis included 231 adolescents aged 13-19 years from Dolj, Gorj, and Olt counties, selected from a parent clinical database of 638 participants. The study-specific outcome was coded when a clearly discernible non-carious hard-tissue change compatible with an abrasive, erosive, or abfraction-related morphology was identified on any clinically accessible surface of tooth 17, 27, 37, or 47. This study did not use BEWE, the Smith and Knight Tooth Wear Index, or another validated severity-based tooth wear index; subtype, surface, and severity were not retained separately in the analytical dataset. Dental caries experience was measured using DMF-T. Group comparisons, correlations, and multivariable logistic regression were performed in JASP version 0.96.0. Sensitivity analyses included a participant-level coding audit and a logistic model using DMF-T recalculated after excluding the contribution of teeth 17, 27, 37, and 47. Results: The study-specific morphological outcome was present in 50/231 participants (21.6%). A coding audit confirmed that 181 participants had no positive second molar and 50 had exactly one positive second molar; tooth-specific counts were 14, 15, 12, and 9 for teeth 17, 27, 37, and 47, respectively. In the primary model, male sex (adjusted OR = 3.34, 95% CI 1.67-6.71) and DMF-T (adjusted OR = 1.15 per point, 95% CI 1.01-1.31) were associated with the outcome. After excluding the four evaluated second molars from DMF-T, the caries experience association remained positive but borderline (OR = 1.198, 95% CI 1.000-1.435, p = 0.049), while male sex remained associated (OR = 3.310, 95% CI 1.647-6.652, p < 0.001). Conclusions: A modest exploratory association was observed between the study-specific morphological outcome and cumulative caries experience in this clinical sample. The result should not be interpreted as a standardized NCDL prevalence estimate, a causal relationship, or a prediction model. Confirmation using validated whole-mouth tooth wear measures, outcome-specific reliability assessment, and population-based longitudinal data is required.