Objective: Test null hypothesis that decay variables from first mailing of parental consent are no different from those generated from second mailing.
Method: An oral survey of school Year 1 (children aged 5-6) undertaken in Wales during 2011-12. Sampling and survey criteria complied with British Association for the Study of Community Dentistry (BASCD) guidance. Sampling frame was designed to sample 250 children from the smallest Unitary Authority (UA) in Wales, Merthyr Tydfil (population 58,000). Similar proportions were drawn from other UAs. Examiners reported visual signs of caries (d3mft) in the deciduous dentition. Comparison of dental epidemiological variables generated from data collected via first mailing and second mailing.
Result: The average dmft for the first mailing was 1.50 (95%CI: 1.42-1.58, 6678 children) compared with a dmft of 2.21 (95% CI: 1.96-2.46, 1056 children) for the second mailing. The aggregate dmft for all 7734 children examined as a part of the survey was 1.59 (95% CI: 1.52-1.66). Equivalent data for dt and %dmft>0 was: dt 1.01 (95%CI: 0.95-1.07) first mailing compared with dt 1.56 (95% CI: 1.38-1.74) second mailing; and %dmft>0 39.5% (95%CI: 38.4 - 40.7%) first mailing compared with %dmft>0 54.1% (95% CI: 51.1-57.2%) second mailing.
Conclusion: The null hypothesis is rejected. Responses to the second mailing suggest that non-responders to the first mailing do have higher levels of decay. Therefore future surveys should include at least two mailings.
Acknowledgements: Welsh Government supported this survey. Email: morganmz@cardiff.ac.uk