Oral health of preschool children in Shenzhen and prevention of decay in their primary teeth through the use of fluoride toothpaste

Abstract

This thesis consists of an analysis of data collected in a territory-wide oral health survey of preschool children in Shenzhen, a short-term clinical study on oral microbiome and a 24-month clinical trial on using fluoride toothpaste for caries prevention.

Objectives: Analysis of the survey data aimed to describe the dental caries situation and the associated factors among the preschool children in Shenzhen. The two clinical trials aimed to evaluate the effects of daily toothbrushing with fluoride toothpaste. Methods: In the survey, clinical examinations were conducted to assess the caries status of a randomly selected sample of preschool children and their parents completed a questionnaire about their children’s demographic background, oral health related behaviours, and their own oral health knowledge and attitudes. In the clinical trial, kindergarten children were randomly assigned into a test group with provision of a 1000 ppm fluoride toothpaste for daily toothbrushing and a negative control group with no toothpaste provided. The development of new caries over a 24 month period was assessed by conducting clinical examinations. Results: The mean dmft scores of the survey children aged 3, 4, and 5 years were 2.7, 4.2, and 5.4, respectively, while the caries prevalences were 55%, 68%, and 78%. Higher dmft scores were found in children who started brushing their teeth late, had breastfeeding in the first six months, consumed sugary food before bedtime, and whose parents had lower education level. Children whose parents had lower dental knowledge and attitude scores had more dental caries. In the clinical trial, the test group children had significant lower caries increment after 24 months. The prevented fraction was 20%. Conclusion: The prevalence and the severity of dental caries among Shenzhen preschool-children are high. Their caries status is related to their background and dietary behaviours, and the dental knowledge and attitudes of their parents. Fluoridated toothpaste at 1000 ppm is effective for caries prevention in preschool children.

Objective: The oral microbiome analysis of the two clinical trials was to investigate the relative abundance and changes in the diversity of oral microbiome in preschool children after using fluoride toothpaste. Methods: In the short-term study, non-F, low-F, and standard-F toothpaste were distributed randomly to kindergarten children for toothbrushing after lunch. In the 24-month trial, 1000 ppm-F toothpaste was provided to the test group children for use at home. Supragingival plaque on buccal surfaces of all teeth was collected at baseline and follow-ups. 16S rRNA gene sequences was used to identify the microorganisms by ASVs. Alpha diversity and beta diversity of oral microbiomes within and between study groups were analyzed. Results: No significant change in bacterial alpha diversity was observed but beta diversity analysis revealed compositional differences in the oral microbiomes of the test and control groups in both studies (p<0.05, ANOSIM). A panel of oral pathogenic bacteria or commensal bacteria showed consistent temporal changes in all groups. Conclusion: This study has identified a group of bacteria in the plaque of preschool children that could be consistently modulated by using fluoride toothpaste.