title: Evaluation of the impact of national oral health improvement programmes of Chile on the oral health of the child population
Creators: name: Celis Sersen, Andrés Osvaldo
Publisher: name: University of Glasgow
Year: 2022

description: Background: Dental caries is reportedly the most prevalent disease worldwide and represents a significant challenge for public health, especially in childhood, with 7.8% of children suffering from untreated caries in their primary teeth worldwide. The Chilean Government is making efforts to gradually improve oral health across the population, with the incorporation of new public health programmes that aim to improve oral health and reduce oral health inequalities, including a community water fluoridation programme; oral health preventive interventions in primary care public clinics, and “Sembrando Sonrisas”, a daily supervised toothbrushing and fluoride varnish application programme in state-funded nurseries based on the “Childsmile” national child oral health improvement programme for Scotland. In Chile, there are few published studies that determine the burden of caries in children, and thus far, there has been no formal evaluation of the impact of the national oral health improvement programmes for Chile on child caries outcomes. Aim: The overarching aim of this thesis was to undertake a quantitative outcome evaluation of the national oral health improvement programmes for Chile on oral health outcomes and related inequalities in children. This overarching aim was met by fulfilling the following objectives: (1) To collect, collate and manage data from the national oral health programmes, along with data on child dental caries and sociodemographic characteristics at the national, regional, and municipality level in Chile; and to assess quality and completeness across datasets; (2) To design and develop an area-based ecological longitudinal cohort to assess the trends in dental caries of six-years-old children in Chile at the national, regional, and municipality levels, and to analyse related area-based socioeconomic inequalities and the impact of the sociodemographic characteristics of the municipalities on child caries levels; (3) To assess the impact of the national oral health programmes, including: community fluoridated water, the preventive interventions delivered in primary care public clinics on the caries levels of six-year-old children in the Chilean public health system at the municipality level, and related inequalities; and (4) To evaluate the impact of the Sembrando Sonrisas programme interventions on dental caries outcomes of five-year-old children covered by the programme since its establishment and rollout, and to assess the programme effect over and above community water fluoridation on child dental caries and related inequalities. Methods: National information governance approvals were obtained to access, collect and collate aggregated municipality level data (n=346 municipalities) for each year (2008 to 2019) from datasets on child dental caries outcomes; the national oral health improvement programmes (community water fluoridation; preventive interventions delivered in primary care public clinics; Sembrando Sonrisas); area-based socioeconomic deprivation (Socioeconomic Development Index; Multidimensional Poverty Index) and rurality (Rurality Proportion Index; Rurality Level Index) data indexes. Data quality and completeness checks were performed to assemble the ecological cohort. A novel ecological longitudinal cohort was assembled using the “municipality/years” unit of analysis, along with the design of a continuous variable for the evaluation of child caries outcomes: “Caries Experience”, measured as the presence of decay (into dentine), missing (extracted) due to decay, or filled primary teeth, in six-year-old children living in Chile who attend primary care public clinics. Univariate and multivariate weighted linear regression models assessed the trends and the effect of socioeconomic deprivation and rurality on caries experience. The most parsimonious model to evaluate the impact of the national oral health improvement programmes was selected with a forward selection model including significant potential confounders of caries experience. Socioeconomic inequalities in the distribution of caries experience by deprivation category were assessed by summary inequality measures. A detailed description of caries experience and related sociodemographic characteristics was performed at the national, regional, and municipality levels. Univariate and multivariate weighted linear regression models assessed the independent potential effect of the national oral health improvement programmes interventions on caries experience, including community water fluoridation coverage and annual fluoride concentration, along with the oral health preventive interventions performed in the primary care public clinics: individual toothbrushing advice to parents; application of sealants on primary teeth; and fluoride varnish applications. Potential inequalities in the delivery of the programmes interventions where evaluated via weighted linear regression models. To assess the impact of Sembrando Sonrisas interventions on caries outcomes of children covered by the programme another, further, separate area-based longitudinal cohort was assembled by merging the data of the two birth cohorts that had being exposed to the Sembrando Sonrisas interventions since its establishment and rollout in 2015. An outcome variable was used, “Sembrando caries experience” in five-year-old children covered by the programme in 2018 and 2019 and examined in the nurseries covered by the programme. Univariate and multivariate weighted linear regression models assessed the independent potential effect of the Sembrando Sonrisas interventions on “Sembrando caries experience”, including the delivery of oral health kits for supervised daily toothbrushing in nurseries (including four toothbrushes and one toothpaste with 1000 ppm of fluoride annually per child) and the application of fluoride varnish in nurseries. Also, multivariate weighted linear regression models assessed the potential impact of those interventions over and above community water fluoridation. Finally, weighted linear regression models evaluated potential inequalities in the delivery of Sembrando Sonrisas interventions. Results: A novel ecological longitudinal cohort was built including dental examination municipality-level data recorded in the primary care public clinics on 1,397,377 six-year-old children available from 3608 municipality/years. Caries experience significantly reduced from 83% in 2008 to 66% in 2019. Those areas with 90% or greater water fluoridation coverage and fluoride concentrations of 0.6 mg/L or higher demonstrated between 7% to 15% lower caries experience than those not exposed to community water fluoridation. A socioeconomic gradient was observed with those municipality from the most socioeconomic deprived category of the Socioeconomic Development Index bearing a 15% higher dental caries burden, while also having a 50% lower water fluoridation coverage when compared to those from the least socioeconomic deprived category of the Socioeconomic Development Index. For the preventive interventions performed at primary care public clinics, a higher rate of these interventions prior to age six was associated with a significantly higher caries experience. Also, a higher rate of these interventions was observed in the most socioeconomic deprived municipalities, in comparison with the least deprived communities. Dental examination municipality-level data recorded in the nurseries covered by the Sembrando Sonrisas programme on 309,360 five-year-old children were available from 637 municipality/years. The delivery of oral health kits for the daily supervised toothbrushing in nurseries to all children participating in the programme was associated with a 5% decrease in caries experience in comparison to those municipality where this was not achieved, even after adjusting for deprivation and the exposure to fluoridated water. The application of fluoride varnish in nurseries covered by the programme was not a significant explanatory variable on the differences in caries experience at the municipality level. Five-year-olds from municipalities with community water fluoridation and where all children received the oral health kits for daily supervised toothbrushing in nurseries showed a caries experience of 52%. In contrast, those from municipalities unexposed to CWF and where not all children received the kits showed a significantly higher caries experience of 65%. Conclusions: A continuing and significant decrease in the caries experience of six-year-old children at the national and municipality level was observed between 2008 and 2019 in Chile. These improvements were shown to be associated with community water fluoridation coverage and annual fluoride concentration. However, by the end of the study period, the high childhood caries levels and inequalities observed remain a public health challenge in Chile. Significant inequalities were identified in the national delivery of community water fluoridation, with the least socioeconomic deprived municipalities having lower annual fluoride concentrations. However, for community water fluoridation coverage —the variable with the higher significant explanatory power in the model, a social gradient was observed, with the most socioeconomic deprived municipalities having significantly lower coverage than the least deprived municipalities. A positive association between caries experience and the preventive interventions delivered in primary care clinics was identified. Some explanations for this observation can be that the variables used in this thesis only accounted for the number of interventions delivered at the population level, without considering the variability of individual contexts and even the possible unintended consequences that can occur as a result of intervening. Most importantly, the circumstances in which children were likely to receive these interventions were probably related to going to the dentist for pain or the need for restorative treatment, causing these interventions to be performed more frequently in children with caries experience. The caries experience of five-year-olds covered by the Sembrando Sonrisas programme since its establishment and rollout was significantly lower in municipalities where all children received oral health kits for daily supervised toothbrushing in nurseries before the age of five years, even after adjusting for deprivation and over and above the presence of the community water fluoridation programme. The lowest caries experience in five-year-olds was observed in those municipalities that were exposed to both programmes. These findings call for continued action at national and municipality level to improve child oral health and to address associated inequalities, including the optimisation of community water fluoridation delivery and the Sembrando Sonrisas programme. In addition, further upstream (policy) and midstream (community-level) interventions delivered via a proportionate universal approach need to be considered.