This study is designed as a cross-sectional diagnostic agreement study conducted in accordance with the Standards for Reporting Diagnostic Accuracy Studies (STARD 2015) and the Guidelines for Reporting Agreement and Precision of Patient-reported Assessments (GRAPPA). The study evaluates the diagnostic agreement between the Digital Caries Risk Questionnaire (DCRQ), a novel patient self-administered digital instrument, and the Caries Management by Risk Assessment (CAMBRA) protocol as the primary clinical comparator. The Decayed, Missing, and Filled Teeth (DMFT) index is used as the reference standard for cumulative caries experience, with a threshold of DMFT ≥ 4 to identify individuals with high caries experience. Although the DMFT index reflects previous disease experience rather than future disease risk, it provides an objective clinical outcome for assessing construct validity. Accordingly, CAMBRA serves as the primary comparator for risk classification, whereas the DMFT index supports validation by evaluating the relationship between questionnaire-derived risk categories and cumulative clinical disease burden.

The methodological rationale for this study is based on the current evidence supporting contemporary caries risk assessment models. CAMBRA is recognized as one of the most extensively validated and widely implemented caries risk assessment systems and has demonstrated diagnostic performance comparable to other internationally accepted risk assessment models. Systematic evidence has shown that these validated models provide acceptable discriminatory ability and calibration for identifying individuals at increased risk of developing dental caries. Furthermore, recent evidence synthesizing longitudinal cohort studies has identified a consistent set of adult caries risk factors, including smoking, systemic diseases, water fluoridation exposure, educational level, fluoride toothpaste use, dietary sugar intake, bacterial plaque accumulation, and previous caries experience. These established determinants are comprehensively represented within the nine domains of the DCRQ, supporting its content validity. In addition, previous validation studies of simplified questionnaire-based caries risk assessment instruments have demonstrated acceptable internal consistency, good test-retest reliability, and significant associations between increasing risk categories and objective clinical indicators such as DMFT scores, plaque accumulation, white spot lesions, and active cavitated lesions. Collectively, these findings support the use of a cross-sectional diagnostic agreement design in which questionnaire-derived risk classification is evaluated against an established clinical risk assessment protocol and validated using objective measures of cumulative caries experience.