The goal of this observational study is to compare the diagnostic performance of three detection methods for approximal carious lesions in primary molars among pediatric patients aged 4-10 years. The study focuses on children in three age groups: 4-6 years, 6-8 years, and 8-10 years. The main questions it aims to answer are:

• Are the sensitivity, specificity, accuracy, and area under the curve (AUC) different across the three diagnostic techniques (bitewing radiography, near-infrared light transillumination, and their combination)?
• Are these diagnostic parameters influenced by patient age?
• Which technique yields the highest level of patient acceptance?

Researchers will compare the three diagnostic approaches to determine whether age influences diagnostic performance and patient acceptance.

Participants will:

• Be examined using bitewing radiography and near-infrared light transillumination
• Undergo tooth separation for 7 days using orthodontic elastic separators
• Receive clinical examination of the target approximal surface
• Be asked to rate their experience using the Simplified Facial Pain Scale (S-FPS)

• 58 carious lesions classified as RA2 and RA3 according to the ICDAS II criteria from three groups of 4-6 years, 6-8 years, and 8-10 years pediatric patients will be examined by near-infrared light transillumination
• The patient acceptance towards bitewing radiograph and near-infrared light transillumination will be evulated by Simplified Facial Pain Scale (S-FPS)
• Diagnostic performance will be assessed by calculating sensitivity, specificity, accuracy, and the area under the curve (AUC)
• The diagnostic efficacy of the caries detection methods will be analyzed using repeated measures ANOVA, and patient acceptance will be assessed using the Chi-square test, with statistical significance set at p < 0.05 and a 95% confidence level.

Inclusion Criteria:

• Healthy Children aged 4-10 years
• Low risk for periodontal disease
• At least one quadrant contains fully erupted, well-aligned adjacent primary molars that are free of restorations, exhibit no clinically visible cavitated caries, demonstrate tooth mobility of grade 2 or less, show no developmental dental anomalies
• Bitewing radiographs show at least one radiolucent lesion in the proximal surface of a primary molar classified as RA2 or RA3 according to the ICDAS II radiographic criteria

Exclusion Criteria:

• Root resorption exceeding two-thirds of the root length
• Demonstrate Frankl's behavior rating scale of 1 during either near-infrared light transillumination examination or tooth separation

Pediatric dental clinic

The individual participant data (IPD), as required by the ethical approval granted by MU-DT/PY-IRB, will remain confidential and will not be disclosed. All data will be reported in aggregate form in publications or reports, ensuring that no individual participant can be identified. Any disclosure beyond these conditions will require an amendment to the approved ethical protocol.