Dental Caries and Related Factors in 6-Year-Old Schoolchildren in Chile: National Evidence for Assessment and Decision-Making (6yOH-Chile)

Detailed Description

Background and Rationale:

Dental caries affects approximately 43% of children under 10 years of age globally (WHO, 2022). Evidence indicates that early detection of initial non-cavitated lesions enables non-invasive and highly effective interventions. Chile has not had a nationally representative oral health survey for the WHO index age of 6 years since 2007. In addition, the First National Child Health Survey (ENSI) excluded oral examinations due to operational complexity, maintaining a critical information gap. This project is aligned with the National Oral Health Plan 2021-2030, which includes a population-based oral health survey conducted by higher education institutions as a process indicator for 2025.

Study Design:

This is a quantitative, observational, cross-sectional study based on a probabilistic stratified two-stage cluster sampling design. The sample will be stratified by school administrative dependency and rurality (urban/rural), covering all 16 regions of Chile. The primary sampling unit will be the first grade classroom, and the secondary sampling unit will be the student. Ten students will be selected per classroom using simple random sampling. Survey weights will be applied and adjusted by sex.

Sample Size:

The estimated sample size is 2,421 schoolchildren, based on an expected prevalence of 50% to maximize variance, a 95% two-sided confidence interval, a 2.5% margin of error, a design effect of 1.5, and an estimated non-response rate of 5%. An additional replacement sample of 461 schoolchildren will be selected, resulting in a total selected sample of 2,882 participants.

Clinical Oral Examination:

Field examinations will be conducted in school classrooms using a flat dental mirror, a CPI periodontal probe, and LED illumination. Dental caries will be assessed using ICDAS-ICCMS criteria, with scores from 0 to 6 recorded at the tooth surface level, including lesion activity classification. with WHO-compatible indicators derived from ICDAS scores 5 and 6 for international comparability. Dentomaxillary anomalies will be assessed by calibrated dentists.

Questionnaire and Data Management:

A structured paper-based questionnaire was administered to parents or caregivers. The questionnaire collected information on sociodemographic characteristics, including region, school type, rurality, and parental educational attainment; oral hygiene habits, including toothbrushing frequency, use of fluoride toothpaste, and parental supervision; fluoride exposure, including fluoridated water and supplements; dental care utilization; and school-based preventive programs.

Electronic data capture using REDCap for exams register was initially considered during the planning phase. However, before field implementation, the research team conducted an operational feasibility assessment under the expected conditions of nationwide school-based data collection. This assessment identified several constraints that could have compromised fieldwork continuity and data completeness, including limited and variable internet connectivity in rural areas and some urban settings, uncertain access to electrical outlets for charging electronic devices during school visits, the cost and time required for electronic form design and secure implementation, and practical limitations of offline electronic data capture for this large-scale field operation. Based on this assessment, the research team adopted paper-based source data collection followed by independent double data entry in EpiData. This approach was selected as the most feasible and reliable strategy for the field conditions while preserving data integrity. All paper-based source documents, including clinical examination forms, parent/caregiver questionnaires, school questionnaires, and fieldwork logs, were scanned and digitally archived. Original paper forms were stored under controlled custody procedures, and the scanned copies provide a digital backup to support traceability, quality control, and discrepancy review.

Independent double data entry in EpiData is currently being performed by trained personnel. Quality-control procedures include standardized paper forms, custody and storage procedures for original forms, scanning and digital archiving of paper records, independent double digitization, programmed validation checks, discrepancy review, and database consolidation prior to statistical analysis.

Therefore, although electronic data capture was considered, paper-based collection was adopted as a risk-based methodological decision to ensure completeness, traceability, and data quality under real-world fieldwork conditions.

Examiner Training and Calibration:

Eight dentist examiners will be trained and calibrated in ICDAS-ICCMS detection and recording criteria. A minimum interrater reliability of ICC ≥ 0.80 will be required before fieldwork activation. A random subsample of participants will be re-examined throughout data collection to monitor examiner reliability.

Statistical Analysis:

Prevalence estimates and 95% confidence intervals will be calculated incorporating the complex survey design and sampling weights using Stata svy commands. Associations will be assessed using binary and ordinal logistic regression models, as well as Poisson regression models when appropriate. Potential confounders will be identified a priori. Results will be disaggregated by region, school type, rurality, and sex.