Optical Imaging

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)