This systematic review assessed the pattern and magnitude of Dietary Free Sugar (DFS) consumption and dental caries in schoolchildren aged 6 to 12 years. Most studies included in our review showed a significant relationship between sugar consumption in the form of sweet or drink and dental caries using different indices in school children though few studies showed not any association. Consumption of sugary beverage and snack especially when started from early ages were significantly associated with the higher incidence or progression of enamel and dentinal lesions. Having bedtime intake of NMEs drink and food, fatty food, processed starch consumption and early exposure to Streptococcus Mutans in addition to omitting breakfast, lunch or dinner were associated with higher caries incidence or progression. Frequent consumption of water and dairy products were considered as protective factor of caries development.
The odds ratio was reported in some longitudinal studies. One study reported high association between consumption of processed starch in snack times and caries in children under 6 years of age; odds ratio of 3.87 was reported in the longitudinal study of Chankanka et al., on 5 years old children followed for 4 years [15]. The effect of starch on dental caries has been further emphasized by Halvorsrud et al., in his recent review [23].
In our review the recent study of Ghazal et al., in 2019 following up of American 6-years old children for 6 years reported no significant association between sugar consumption and caries measured on tooth surfaces as DMFS. This study reported the protective effect of water consumption on dental caries [12]. Also the study of Leroy in Belgium in 2005 and Bruno-Ambrosius in Sweden in 2005 reported no significant association between sugar consumption and dental caries. Other papers included in our reviews showed some association between sweet diet and caries measured with different indices in children aged 6-12 years old. In one study only girls were followed and this limits the generalizabiliy of the study [21].
In our review there was strong evidence confirmed the impact of soft drinks on caries development as reported in the study of Hooley et al in 2012 [14]. Despite the fact that some studies did not report any association between consumption of SSB including soft drink and other sugary drinks and caries in the primary and permanent dentition such as the study of Lueangpiansamut, et al., in 2012 [24].
In our review, a significant relationship between sweet food and snacks consumption and dental caries has been reported in most studies. However, 3 studies couldn’t show any such association [12, 21, 22]. A 4-years cohort study of Chankanka in 2011, indicated that existing of new cavitated lesions was associated with consumption of processed starches at snack time. This is in line with the study of Hujoel and Lingström in their narrative review in 2017, discussed that fermentable carbohydrates especially sugars are responsible for caries development. The susceptibility of teeth for dental caries in presence of fermentable carbohydrates including sucrose, glucose, fructose, lactose, maltose and starch has been discussed in the literature [25].
Studies included in our review are heterogeneous in terms of age and the follow up period. Studies included in our review reported 2 to 7 years of follow up in studies on children less than 6 years of age. Few studies reported longer period of follow up as part of a randomized controlled trial on other health issues like cholesterol. Moreover, studies included are heterogeneous in terms of indices used to measure caries, which makes the comparison different.
Bedtime consumption of sugary food or drinks reported as a risk factor of caries in different types of studies. There is evidence that sugar consumed before bed increases the risk of caries due to the reduced saliva flow and sustained low plaque pH. The study of Baghlaf et al., in 2017 has been addressing the relationship between dental caries experience and the consumption of foods and drinks containing free sugars at bedtime in 3 to 16 years old children. Despite the low quality of evidence, they found a positive association between dental caries and free sugar consumption at bedtime in children. This systematic review emphasized on more consistent evidence for preschool children compared with older groups [26]. Tagi et al., in 2018 showed that children who consumed cariogenic food or drinks between main meals (p=0.01) and within two hours before bedtime (p=0.04) had significantly higher mean caries as measured according to the D4-6MFT index compared with children who did not have this habit [27].
In our review only dietary factors reported however, there are other predisposing factors evaluated in different studies. In the study by Ollila et al, in 2007 eating candies more than once a week and insufficient oral hygiene at two years old were key risk factor for dental caries development in deciduous and permanent molar teeth. They showed that children who used nursing bottle at night for a long time similarly had harmful habits of using candies more than once a week, did not brush their teeth often, and did not use fluoride pills. It can be concluded that most of life style habits of children such as tooth brushing or dietary habits form from first childhood years considered important which was shown in the ten-year cohort study done by Mattila et al in 2005 [28]. Our review confirms the necessity of diet advice along with other preventive measure to control caries in school children which is in line with other preventive measures as discussed in the review study of Pakdaman et al., on caries progression [29].
In our study, a meta-analysis to address the review question was not feasible as the heterogeneous nature of the studies. In our review, there was variability in the caries outcome measure (i.e., DMFS, dmfs, DMFT, dmft, caries, and ICDAS/BASCD criteria). In addition, various dietary outcome measures and tools being used (24-hour recall, FFQ, 4-day food record, 3-day diary, and questionnaire). In addition, there was variation in the follow-up periods.
Strength
One of the strength of this study is to select high level of evidence including the longitudinal studies. Those studies included as trials of other health factors such as cholesterol also considered. Although association between diet and dental caries was observed in several cross-sectional studies, no study reported just the evidence of cohort studies. Moreover, we used STROBE checklist for grading of the studies. Two independent reviewers scored the included papers according to the checklist. In some studies further analysis of data including survival analysis performed such as the study of Ollila, Ghazal, and Leroy [9, 12, 22].
Limitations
Evidence reporting the association between diet and dental caries in schoolchildren are heterogeneous in terms of using different indices to measure caries and diet assessment tools. Moreover, in our systematic review articles published in non-English language, also unpublished and grey literatures have not been included which is considered as limitation. It is important to consider that there are no pure interventional studies on high-sugar diet due to ethical issues despite the fact that in some studies the sample was derived from a trial on other health issues.