Background <p>This study investigated the relevant factors influencing the caries increment among schoolchildren in Liaoning Province and constructed a structural equation model to analyze the complex interrelationships among these factors.</p> Methods <p>Baseline data of 7,904 schoolchildren were collected through clinical oral examinations and questionnaire surveys in 2024 and oral examinations for the cohort were collected in 2025.</p> Results <p>The prevalence of dental caries was 31.1% in 2024, with a mean DMFT/dmft of 0.84 ± 1.57, which increased to 50.6% and 1.63 ± 2.24, respectively, in 2025. A total of 2,865 individuals showed caries increment (defined as △DMFT/dmft ≥ 1), corresponding to an incidence of 36.2%. The results of the multivariate logistic regression analysis indicated that socioeconomic region, grade, gender, weight status, and deliberate exclusion from or isolation in group activities were significantly associated with the caries increment. Structural Equation Modeling analysis (SEM) converged to identify socioeconomic factors as a factor associated with caries incidence, showing both direct associations and indirect associations mediated by poorer dietary habits, although the observational one-year design precludes strong causal clclaims. Notably, the model also indicated a protective association with higher weight status, a finding that merits further investigation.</p> Conclusions <p>While conventional factors such as socioeconomic status, dietary habits, and weight status are well-established influencers of caries increment in schoolchildren aged 9–12, our findings highlight that psychological factors, such as experiences of social isolation, constitute a significant determinant. This dimension merits particular attention in both future research and preventive strategies.</p>