Our epidemiological survey revealed that the prevalence rate of caries was high among children aged 7–9 years in Jinzhou City. Dental caries were found in 1,194 of 1,603 students (dmft > 0).We also identified several risk factors associated with dental caries, including sociodemographic factors, socioeconomic status factors, oral hygiene behaviors, and dietary habits. Caries are more likely to occur in certain susceptible teeth, but not on all teeth. Some papers [11, 14] have shown that molars are more prone to caries than incisors and cusps, mandibular molars were the most susceptible to caries, and mandibular incisors and cusps were the least sensitive teeth, consistent with the findings of this study. There are three reasons for this. First, mandibular teeth generally appear before maxillary teeth, and are exposed to the mouth for a long time. Second, related to the specific macro morphology of the occlusal surface, there are many irregular, narrow, and deep pits and cracks on the surface of molars. In these parts, the enamel thickness is often insufficient and is located behind the teeth, resulting in poor oral cleaning and more accumulated plaques [15–16]. Third, the mandibular anterior teeth are located at the opening of salivary glands such as the submandibular gland. Saliva provides lubrication and mechanical cleaning for the mouth so that dietary sugars and acids produced by plaque metabolism are flushed away after being exposed to carbohydrates. This effectively controls the PH value in the biofilm and prevents enamel demineralization [17]. In addition, the mandibular anterior teeth are located in the front of the mouth and are therefore easier to clean.
In this study, the prevalence of caries in deciduous teeth in children aged 7–9 years in Jinzhou was higher than that in Wuhan (67.7%) [7] and Guangzhou (30.7%) [18].Results cannot be directly compared with any other studies because of differences in age groups, however. According to the report Chinese Students and Health Study in 2005, the prevalence of deciduous teeth caries and dmft of 5-year old children in Liaoning Province were 73.86% and 4.38, respectively, both of which were lower than those in 1995 (89.49% and 6.77, respectively) [5]. However, compared to our study, the incidence of caries in Jinzhou was slightly higher than that in Liaoning province (74.4% vs. 73.86%), possibly because the one-child policy implemented by the Chinese government had a greater impact in the northeast region, leading to more only children whose parent may have been more inclined to “spoil” them. Second, most of the children in our sample lived in cities, where the socioeconomic status level was slightly higher than in rural areas, and it was easier for them to obtain carbohydrates in their diet. Finally, this results may also have been closely related to the low level of oral health care for children.
In terms of social demography, we found a positive correlation between sex, age, household registration type and the prevalence of caries (P < 0.05).In terms of gender, the prevalence of caries in boys was higher than in girls, which is the same result as several previous studies [18–22]. This difference may be attributed to the fact that girls tend to pay more attention to the appearance of their bodies and teeth, have lower self-esteem than boys, are more sensitive to oral diseases, and are impacted more by all these aspects in terms of quality of life [22–23]. As a result, girls tend to have a more positive attitude towards oral health, a healthier lifestyle, and a better level of oral hygiene.
For age, our results were consistent with some existing studies as well[20, 25] that showed that the caries rate of deciduous teeth decreased with age, which is related to deciduous tooth loss and permanent tooth eruption. As for the type of household registration, we found that the prevalence of caries among children in urban households was higher than that in rural households, which is also consistent with the literature [19, 26]. However, most studies have shown that the prevalence of caries in rural areas is higher than that in urban areas [11–12, 25]. This difference in results may be attributable to the different age groups between such studies and ours and the fact that the majority of the children in our study came from urban areas. Second, Changes in dietary patterns in Northeast China have made it easier for urban populations to obtain processed sugary foods and consume less coarse grains.
In terms of socioeconomic status, parents' education level is typically used as an individual measurement standard [20]. A study in 2020 showed that [27] mothers pay more attention than fathers to their children’s teeth brushing habits, to their children’s diets, and to seeking dental services when needed. The main responsibility of fathers is to manage the financing of medical care. Therefore, we only looked at the relationship between maternal education level and tooth decay and found a significant negative association between mother's education level and the prevalence of dental caries (P < 0.05),consistent with multiple other studies [2, 28–29]. Binary Logistic regression showed that the incidence of caries in children with a low maternal education level was 2.058 times that in children with a high maternal education level (OR: 2.058, 95%CI: 1.129–3.752).The lower the mother's level of education, the more likely the child was to have tooth decay. The reason is that the education level of the mother has an impact on her and her child oral health knowledge, attitude, and behavior toward oral care. The higher the education level of the mother, typically the richer the oral health knowledge, the greater the demand for oral health care, and the better the oral health status of the child [27, 30].
Next, although the effect of oral hygiene behaviors on the prevention of dental caries is controversial [31–33], we found that there was statistically significant difference between different oral hygiene behaviors and habits on the prevalence of dental caries (P < 0.05).The higher the frequency of brushing and the longer the duration of brushing, the lower the prevalence of dental caries, which is consistent with most studies [20, 26, 29]. However, Alraqiq [31] and Kamran [32] showed that there was no correlation between the occurrence of dental caries and the frequency of brushing, only a negative relationship between the brushing time and dental caries. The correlation between the two was also found in our regression analysis. At present, the relationship between dental floss and dental caries is unclear, and there is little literature on the correlation between the two. A meta-analysis showed that the proportion of children under the age of 6 who use dental flossing is very low, at 12.60%[34]. only some research [22, 35] has shown that floss can prevent the occurrence of proximal dental caries, however. This maybe because floss can remove the impaction of food near the teeth and physically interfere with the adhesion of bacteria in the plaque biofilm, thus reducing the amount of caries-causing bacteria and thereby reducing the prevalence of dental caries [22]. Chi-squared tests and binary logistic regression analysis also revealed the same correlation in this study, indicating that dental floss may indeed play a certain role in preventing dental caries, but further longitudinal analysis is needed.
In terms of dental treatment, we found that the caries rate for children with time since last dental treatment > 1 year was higher than that of children with time since last dental treatment ≤ 1 year. Most of the children went to see a doctor because of the pain caused by dental caries, and only 394 children had regular examinations accompanied by their parents, indicating that parents still pay insufficient attention to the need for preventive and restorative dental treatment. Moreover, binary logistic regression showed that children suffering from dental caries were more likely to go to the dentist (OR: 2.617, 95% CI: 1.714–3.995), which agrees with the literature [31–32, 36].
The relationship between dietary habits and dental caries has been studied since the 1940s and is now a recognized and modifiable risk factor [10, 37]. However, the association with dental caries is different between countries due to differences in dietary patterns, and even different within countries due to differences between different ethnic groups. In our study, we only looked at some of the sugary processed products that children in this age group like to consume, but both Chi-squared tests and regression analysis showed that soft drinks, desserts, and especially confections, were significantly positively correlated with the prevalence of caries (P < 0.05).These results agree the results of many other studies [10, 30, 36, 38–39].The higher the frequency of eating sugary foods, the greater the incidence of dental caries. The mechanism for this has been attributed to the fact that the plaque in the tooth biofilm decomposes carbohydrates, releases acid products such as lactic acid and acetate, and changes the pH value in saliva and plaque. When the pH value is lower than the critical level of 5.5–5.7, a large amount of calcium and phosphate on the enamel surface is dissolved, which increases cariogenic potential [40–41].
Our study has some advantages over other studies. First, a comprehensive and systematic analysis of the modifiable risk areas leading to the occurrence of dental caries was conducted, which goes beyond several previous studies in this field [26–27, 29, 31]. Second, a larger sample size was used to evaluate the current dental caries status of deciduous teeth. There have been few previous studies on the dental caries status of children aged 7–9 years old, and there is a lack of such studies on northeast China. Finally, a comprehensive analysis of the caries of each tooth of the primary teeth in the mouth was made, which has rarely occurred in previous studies.
There are some limitations to our study, however. First, this is a cross-sectional study that cannot establish a causal relationship between risk factors and tooth decay, so further longitudinal studies are needed to obtain more accurate data. Second, risk factors were investigated in the form of questionnaires, which have a certain degree of recall bias. Finally, the sample of this study only involved the investigation of decayed teeth in children aged 7–9 years old, so it may not be generalizable the whole province or country.