Comparison of two caries prevention programs among Thai kindergarten: a randomized controlled trial

Although there have been dramatic declines in the dental caries burden in the last 20 years in several industrialized countries, the dental caries experience in Thailand has remained approximately unchanged for 30 years, particularly in 3–5-year-old Thai children [1]. These data indicated the need for an effective caries control regimen among young children. Some studies argued that prevention strategies that focused solely on those at higher risk have less impact compared with strategies that focused on the whole population, because the majority of dental caries will occur among those not at high risk [2, 3]. However, strategies that impact whole populations frequently require action beyond the health care sector and are politically more difficult to achieve.

Although caries preventive measures, such as early detection, risk assessment, supervised tooth brushing, sealant application, and topical fluoride application have proven effective in clinical trials [4‐8], there is little investigation of the high-risk regimen in real-life conditions, especially for young children. In our study, the basic preventive regimen including supervised tooth brushing was given to the whole population and an intensified regimen of fluoride varnish, sealant, and silver diamine fluoride application comprised the intensified preventive regimen. Various effective preventive measures have been separately implemented among the children with dental caries but there is little evidence of their effect when they were applied together. Moreover, it wondered that high cost and time consume procedure would give high result or not. Therefore, the aim of this study was to evaluate whether the intensified preventive regimen was more effective compared with the basic preventive regimen for decreasing caries development in young children.

This study was registered in the Registry of Clinical Trials run by the Thai Clinical Trials Registry (TCTR) (TCTR20180124001). Ethical approval was obtained from the institute’s committee on human research of the Faculty of Dentistry, Chulalongkorn University (HREC_DCU 2017–084). Written informed consent was obtained from the parents or guardians. The recruitment period started in September 2017 and ended in January 2018. The last follow-up examination was performed in December 2019.

A total of 121 kindergarten children (67 boys, 54 girls) with 28, 47, and 46 children in the LRB, HRB, and HRI group, respectively, were recruited in this trial. At baseline, the mean (standard deviation (SD)) caregiver age was 36.6 (9.2) years. The children’s mean (SD) decayed, missing, and filled score was 5.68 (5.07) teeth and 13.04 (15.37) surfaces, respectively. Plaque was found on the children’s tooth surfaces with a visible plaque index score (VPI = 1.11). There was no significant difference between the children in the three study groups regarding their demographic background, oral health–related behaviors, perceptions related to dental caries, and tooth brushing self-efficacy (χ² test and ANOVA at p > 0.05) (Table 1). Clinically, the children whose risk was considered high (HRI and HRB) had markedly higher baseline dmft/dmfs scores compared with those for whom the risk was considered low (LRB). However, there was no significant difference between the two high-risk (HRI and HRB) groups in baseline dmft/dmfs (p = 0.992).

A total of 96, 94 and 89 children were re-evaluated at 6-, 12-, 24-month follow-up. The overall dropout rate was 26.4% with 32.1, 25.5, and 23.9% in the LRB, HRB, and HRI group, respectively. Moving to another school and absent from school on the examination date were the reasons for leaving this study (Fig. 1). There were no significant differences in the demographic background, oral health–related behaviors, and clinical characteristics between the children who completed the study and those who were lost to follow-up (p > 0.05) [see Additional file 1]. At least one tooth of newly developed caries was found in 35.4% of total children at the 6-month follow-up and this percentage rose to 60.7% at the 24-month follow-up (Table 2). Caries increment highly increased over time in all groups, particularly in the children classified as high caries risk The percentage of new caries development in the HRB group increased from 45.9% (at 6 months) to 75% (at 24 months), similar to those in the HRI group demonstrated an increase from 40% (at 6 months) to 65.7% (at 24 months) (Table 2). Notably, the intensified preventive regimen intended for use in high caries children did not help to control new dental caries development. A total active lesion of 138 surfaces from 159 surfaces (86.8%) became arrested caries after SDF-treatment for HRI group.

The increment dmfs/DMFS and increment dmft/DMFT at 6-, 12-, 24-month follow-up were significantly higher in the two high-risk groups compared with the low-risk group. However, there were no significant differences between the HRB and HRI groups in caries increment for pairwise comparisons at 6-, 12-, 24-month-follow up. For the children in the HRB group, the total increment (6.75 surfaces) was higher than those in the HRI group (5.91 surfaces). However, there was no significant difference between the HRB and HRI groups at the end of our study (p = 0.709) (Table 3).

Bivariate analyses of the independent variables are shown in Table 4. The variables of children’s gender, dmft score, risk group, perceived susceptibility, perceived severity to dental caries and treatment were selected for the multivariate analysis. The crude odd ratios (ORs) indicated that these variables were different between the children with absent and present new caries.

The multiple logistic regression modeling resulted in a model containing 6 variables. Table 4 also presents the adjusted ORs, and the 95% confidence intervals (CIs) of the final model for new caries development. Risk group and perceived susceptibility still significantly affected new caries development after adjusting for other variables. Being in the high risk group had an OR of 7.52, signifying that the chance of new caries development would be 7.52 -fold higher than that of the low risk children. Moreover, for every 1 score increment in perceived susceptibility, odds of new caries increase 21%.

The results indicated that the children in the LRB group developed significantly fewer carious lesions compared with the high-risk children in both groups. These results indicate prediction of future caries in children by past caries experience, similar to those of several studies [8, 11‐14]. At the end of the present study, there was no significant difference between the HRB and HRI groups in caries increment. Our results indicated that the additional intensified preventive regimen intended to control caries use in high caries populations did not further control dental caries, which is similar to previous studies showing intensifying prevention produced practically no additional benefit [15‐17]. Hausen et al. found a no significant difference between intensified prevention and basic preventive programs in 12- to 13-year-old children. In contrast, there is a study indicated benefit from an intensified prevention program (fluoride varnish application, fissure sealing, and restorative therapy) in decreasing caries development [18]. These disparate results may be due to the absence of any oral hygiene instructions provision for the control groups while our basic preventive regimen group received interventions for achieving quality tooth brushing with no restorative therapy (oral health education with hand-on tooth brushing practice, supervised tooth brushing by their teachers during after-lunch brushing, and received a tooth brushing by their teacher at least once a week). The present study proposed a basic preventive regimen that differed from those of other studies, i.e. the provision of quality tooth brushing at least once a week. The provision of quality tooth brushing by the teacher once a week might be an important factor in the small dental caries increment among the three groups which was confirmed by several studies [19, 20]. In our study, every child brushed their teeth after-lunch under the supervision of their teacher every day, additionally, each child received tooth brushing by their teacher at least once a week. This strategy is practical as each teacher do the brushing for 5 children in 1 day during the assistant teacher supervised the children’s after-lunch tooth brushing. This practical strategy helped increase the quality of the child tooth brushing while reduce burden to the teacher. Provision of oral health education and hand-on tooth brushing practice to the teacher was arranged prior to the program commencement for emphasizing their crucial role and increasing the essential of their role. The session of oral health education emphasized the identification of plaque that causes carious lesions. They were also informed that white lesions could be reversed by a quality tooth brushing with fluoride toothpaste.

Although this study indicated no significant difference in caries increment between the two high-risk groups, the total increment in the HRB group was slightly higher than the HRI group at the end of study. One reason might be that the HRI group received additional professional preventive care at an early stage of caries progression, while the HRB group received the intensified tooth brushing regimen for preventing dental caries development. The potentially caries-preventive measures of sealant and fluoride varnish application used in HRI group protects against new caries development, while SDF is used for non-operative treatment for active caries. In this study, carious teeth became arrested caries after SDF-treatment for HRI group (86.8%). The active caries treated with SDF usually turns into arrested caries, which is normally brown or black, hard, glossy, and non-progressive. SDF inhibits tooth demineralization and promotes remineralization [21, 22]. However, this study did not alter the child eating habit which might affect the caries development. Moreover, the weekly quality tooth brushing with fluoride toothpaste by a teacher might be an effective potential caries prevention regimen. Then, the disappointingly low effect of the intensified prevention regimen was showed in the small difference between the high risk groups.

Factor associated with newly developed caries were identified by a multiple logistic regression model. The results, at baseline, indicated risk group is an important factor for new caries development among Thai kindergarten as children in high risk group have tendency to develop new caries more than others. These results re-emphasize the importance of ECC risk assessment among children.

Despite the rich data emerging from this study, limitations exist. The loss to follow up in our study was fairly high, especially in the low-risk group (32.1%). The number of lost children in the HRB group (25.5%) was higher than the HRI group (23.9%). High loss at follow up cannot be avoided in field studies.

The negligible difference in caries increment between the HRI and HRB groups implies that intensified prevention produced minimal additional benefit. Offering all children only basic prevention could obtain virtually the same preventive effect with substantially less effort and lower cost. However, this strategy needs long term compliance from both teachers and parents to maintain the child’s good oral health. Tooth brushing should be performed on a regular basis and this habit should be instilled as a lifelong healthy behavior.