Does orthodontic treatment affect caries levels?

Design A prospective cohort study.Exposure/sample selection In 2005/2006, the authors analysed data from participants in a previous oral epidemiological study conducted in 1988/1989. Children whom were clinically examined in the School Dental Clinics in South Australia in 1988/1989 were invited to a follow-up in 2005/2006. Respondents competed a questionnaire concerning their sociodemographic characteristics, dental health behaviours and the receipt of orthodontic treatment, and were invited for a clinical examination. Oral health information concerning decayed, missing and filled teeth (DMFT) and occlusal status using the Dental Aesthetic Index (DAI) were recorded by multiple trained calibrated dentists in accordance with the NIDR procedures. The study obtained ethical approval from the University of Adelaide and maintained informed consent at each stage of the study.Data analysis Data analysis was performed independently by the principle researcher. Analysis involved descriptive statistics, frequency distribution and cross tabulation. Explanatory variables for orthodontic treatment and dental outcomes were investigated for each DAI category using negative binominal regression using the online computer programme 'effect size calculator'. The statistical analysis was preformed using IBM SPSS statistics version 24. All explanatory variables were introduced into the adjusted negative binominal regression models based on their statistical significance from multiple linear regression models, with the p value set at 0.05.Results The response rate for the questionnaire was 34% (n = 632), with 74% (n = 473) of those attending for clinical examination. After exclusions, 24% (n = 448) of those originally contacted participated. Statistically significant differences in clinical outcomes were observed between those who had and had not visited the dentist in the last two years. These outcomes included missing teeth (MT), filled teeth (FT) and a higher DMFT score. In addition, brushing at least twice daily was associated with fewer decayed teeth (DT) and MT (p <0.001). Increased MT was observed among individuals who had orthodontic treatment across all DAI categories except for participants with very severe malocclusion. In this group, there were significantly more MT among the untreated participants (p <0.001). Thirty-five percent (n = 157) of participants reported a history of orthodontic treatment by the age of 30. No statistically significant associations were found between orthodontic treatment and all aspects of DMFT using adjusted models for participant self-reported sociodemographics, dental health behaviours and malocclusion.Conclusions Caries experience does not correlate with previous orthodontic treatment. Sociodemographic variables and dental health behaviours have a greater impact, and are associated with long-term disease outcomes, including numbers of DMFT. Caries experience is also associated with educational attainment and income level, frequency of tooth brushing and dental office attendance. In summary, orthodontic treatment does not provide superior long-term dental health outcomes in relation to caries. The hypothesis that those with previous orthodontic treatment would have lower caries experience was rejected.