## 2 Materials and Methods  
This retrospective study included a records review of pediatric patients who visited the dental hospital at the College of Dentistry at Imam Abdulrahman Bin Faisal University (IAU) in Dammam, Saudi Arabia. The study was conducted in accordance with the Declaration of Helsinki and was approved by the Institutional Review Board at Imam Abdulrahman Bin Faisal University (#2017-02-48). The records of all patients who visited the dental hospital over a six-year period (2015-2020) were reviewed. For records to be included in the study, they had to meet the following inclusion criteria: (1) records must contain a complete set of bitewings and periapical intraoral radiographs of all the primary molars; (2) patients must be in primary or mixed dentition. Patients with exfoliated primary teeth, trauma that caused tooth loss, missing teeth due to extraction, and patients with syndromes and medical conditions that affect caries patterns or the number of teeth were excluded. The identified radiographs of these patients were examined using a standardized method by means of the MiPACSDental Enterprise Viewer, software version 3.1.1404 (Medicor imaging, Charlotte, NC, USA). The magnification option in the software was used as needed. Patients' identifiable information (name and ID) was not recorded, and confidentiality was maintained. The legal guardians of the pediatric patients signed an informed consent form prior to the radiographic examination. The sample size was calculated prior to the completion of the study. The calculation was based on the following assumptions: confidence intervals = 95%; margin of error = 2%; proportion of the population with caries on the proximal surfaces of the primary molars = 20%; and the total population size = 2000 ([[https://www.calculator.net/sample-siez-calculator](https://www.calculator.net/sample-siez-calculator)]([https://www.calculator.net/sample-siez-calculator](https://www.calculator.net/sample-siez-calculator)), accessed on 29 August 2020. The estimated sample size was 870 records. A total of four medical and radiographic records reviewers completed three consecutive training and calibration sessions prior to the completion of the study. The training consisted of radiographic cases of randomly selected radiographic records of bitewings and periapical views of the first and second primary molars. Reviewers were asked to record the sound, decayed, or filled proximal distal surfaces of the first primary molars and the mesial surfaces of the second primary molars. Caries was recorded if the proximal radiolucency reached half the thickness of the enamel or more. Caries that reached the pulp and recurrent caries beneath a failed restoration was recorded as caries. Responses were compared to those of a gold standard pediatric dentist using Kappa statistics to determine inter- and intra-examiner reliability. Demographical data (gender, age, nationality, medical history, and patient behavior) were recorded for each patient based on the information available in their medical records. Significant medical history was considered if the patient had any medical conditions recorded on file, including medications or medication allergies. Patient behavior was recorded based on [PERSON]'s Behavior Rating Scale (FBRS): definitely negative (\(--\)); negative (\(-\)); positive (\(+\)); and definitely positive (\(++\)) [22]. This instrument has shown satisfactory reliability and validity [23], and it is the routinely used method to report patient behavior in the medical records of all pediatric patients who attend the dental hospital. Children's behaviors and radiographs were extracted from their initial visit records. The Statistical Package for the Social Sciences (SPSS), version 25.0.0.2 (IBM Corp., Armonk, NY, USA), was used to analyze the data. The frequencies and percentages were calculated for categorical demographical variables.