The prevalence and risk factors of Early Childhood Caries among 3-year-old children in Wenzhou

Background: This study aimed to investigate the prevalence and risk factors of Early Childhood Caries (ECC) among 3-year-old children in Wenzhou China. Methods: Preschool children aged 3 were recruited using a stratified cluster sampling method. Dental examinations were carried out by one trained dentist, and oral health-related data were collected. Examinations were surface-specific for dental caries, following World Health Organization (WHO) criteria. Bivariate tests and logistic regression models were used to investigate the risk factors of dental caries. Results: A total of 693 children were recruited for the study, and 445 completed the dental examination. Among the 445 children, the prevalence of ECC was 59.8%. The mean decayed, missing, and filled primary teeth (dmft) was 2.9, and of the total dmft, only 6.3% were filled. The mean decayed, missing, and filled primary surface (dmfs) was 4.9. Logistic regression analyses identified age and parents’ oral health knowledge level were associated with the experience of ECC (P<0.05). Conclusions: A higher prevalence of ECC was observed and most of the carious teeth were not restored. The experience of ECC was related to age and parents’ oral health knowledge level.

during last three decades [ 4 ]. In contrast, because of the easy availability of refined sugars than earlier, compromised dental care and prevention, very few programs to eradicate the disease and poor public knowledge about the disease, dental caries in China has become a new threat and been on the rise [ 5 , 6 ,7,8]. The Third National Oral Health Epidemiology Survey reported that the prevalence of caries was 66% and the mean decayed, missing, and filled primary teeth (dmft) score was 3.5 among 5-year-old children in China [ 7 ]. The high prevalence of early childhood caries exist in China is alarming.
ECC is a chronic and multifactorial infectious disease. The risk factors found to be responsible for ECC included low family socioeconomic status [ 9 , 10 ], sugary snacks or beverages consumption [ 10 , 11 ], nutritional problems, improper bottle use [ 12 ], poor oral hygiene status [ 9 , 12 ], and higher levels of Streptococci mutans bacteria [ 10 ]. A systematic review revealed that longer duration of breastfeeding up to age 12 months would be a protective factor for dental caries [ 13 ]. However, children who were breastfed > 12 months were more likely to develop dental caries [ 13 ]. Owing to the different study designs and statistical analysis, the reports of risk factors for ECC in different population differ in part [ 14 ]. It has been revealed that the prevalence of 3 years old children in Wenzhou was very high [15]. However, the risk factors of dental caries among Wenzhou preschool children remained unknown. This investigation aimed to assess the relationships between the prevalence of ECC and dietary lifestyle, oral health behaviors, demographic risk indicators and socio-economic status in Wenzhou preschool children.

Selection of participants and sample size
Data from a longitudinal observational study in Wenzhou were used and analyzed. A stratified cluster sampling method was used. 6 kindergartens were sampled from three districts of Wenzhou. Three glasses from Grades 1 (aged 3-4 years) were sampled in the selected 6 kindergartens. It was reported that the prevalence of ECC in the 5-year-old age group in China was 66%[ 7 ] [Qi, 2008 #45]. The sample size estimation was found to be 92. Because the participants were younger than 5 years old, it was speculated that the corresponding prevalence of dental caries would be less than 66%. Therefore, lager sample size was required. Eventually, 693 children aged 3-4 years were surveyed. Children with systemic diseases were excluded. The ethical approval for this study was obtained from the Institutional Ethics Committee of Wenzhou Medical University. The purpose and details of this study was explained, and written informed consent was obtained from parents or legal guardians.

Dental examination and diagnostic criteria
All eligible subjects received oral health examinations in the kindergarten. Only one calibrated examiner carried out the examination under natural light by using a World Health Organization (WHO) probe and a mouth-mirror. The examiners evaluated caries experience by using the WHO criteria [ 16 ] and without radiographs. 10% of children were re-examined to assess the intra-examiner reliability. Intra-examiner weighted kappa on tooth status was 0.96.

Data collection
Parents or other caregivers were asked to complete the survey questionnaire. Data were collected with the use of structured questionnaires. It mainly collected information included dietary lifestyle (e.g. frequency of snacks and drinks consumption, meals and drinks at night), and feeding habit (night-time nursing bottle use), oral hygiene practices (e.g. age brushing started and toothbrushing frequency), parental oral health behavior, utilization of dental services, and socio-demographic characteristic (e.g. parental education level, annual household income). Parental oral health knowledge about caries was collected.

Statistical analysis
The collected data were entered into Epidata software, version 3.1, and analyzed using SPSS version 19. The analysis first resulted in the reporting of descriptive statistics.
Bivariate analyses were performed using the chi-square and Wilcoxon rank sum tests. We performed a t-test to test the differences in mean age between the children with and without caries. The risk factors associated with dental caries were founded out using multivariable logistic regression model. P-value < 0.05 were considered of significance in this study.

Caries experiences
A total of 693 children from six kindergarten were recruited for the study. 445 completed the dental examination, while the rest 248 children not examined as they were absent (often repeatedly) on the day of examination for undetermined reasons or of dental phobia.
The percentage of unrestored decayed teeth in this study was 93.7%. Approximately 30 percent (31.2%) of the children had four or more teeth with caries experience, consist of 80 percent of the decay.
Questionnaires were completed by the majority of parents (95%). There was no significant difference between ECC group and caries-free group.

Bivariate analysis
The relationship between ECC and dietary factors and oral hygiene practices were presented in Table 1

Multivariable logistic regression analyses
The final multivariable logistic regression analyses revealed age and parental dental knowledge levels were associated with the experience of ECC (P<0.05) ( Table 3).

Discussion
This study showed that the prevalence of dental caries among 3-year olds children in Wenzhou was 59.8%; it was higher than the prevalence of ECC in 3-4 years old in Beijing (49%) [ 8 ]. On average, the prevalence of dental caries among 3 years old children in China was 50.8% [6]. In Asian countries, such as India [ 18 ] and Singapore [19], the prevalence of dental caries in preschool children was found to be 47.3% and 49% respectively. The prevalence of dental caries among 3 years old children in Japan was 14.7% [20]. In some developed countries, the prevalence was low which was largely attributed to increasing awareness of oral hygiene behaviors, increasing access to fluoridation, and parental concern about the dental health [ 18 ].
It has been reported that about 80 percent of decayed teeth was found in 25 percent of children [ 21 ]. Similarly, this study reported that approximately 30 percent (31.2%) of children had more than 3 teeth with caries experience, which consists of 80 percent of the total decay detected. In this study, the percentage of unrestored carious teeth was 93.7%. It may be due to the lack of public knowledge about primary prevention and the shortage of dental health workers.
This study depicted that older children were more vulnerable to develop dental caries. [ 23 ]showed that increase with age children were more likely to develop caries.

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These results are likely to be due to caries progression exposed to early caries challenge, and caries susceptibility [ 24 ].
Our study showed a negative association between parental dental knowledge levels and the experience of ECC. Similarly, Chen et al reported that parental oral knowledge levels were associated with dmft scores [ 25 ]. During the early years of life, parents play a vital role in taking appropriate health-related action for their children. Positive attitude and health knowledge of parents is of paramount importance to child's quality of life [ 26 ].
This study depicted that age toothbrushing started and parental check after toothbrushing would be predictors of dental caries, while it was unable to found the association between frequency of toothbrushing and dental caries. A longitudinal prospective study has shown that the children who brushed their teeth less often at age 2 were more likely to develop caries at age 5 [ 27 ]. In this study, the effect of twice daily tooth brushing was probably in part attenuated because of unaided toothbrushing. Collett et al stated that child's oral health was associated with parent-supervised toothbrushing [ 28 ].
It was unable to found the association between breastfeeding and dental caries in this study. However, Kato T et al stated that there was an association between bottlefeeding and dental caries [ 29 ],[, #12973] while another authors have not found such an association [ 22 ]. Tham et al stated that longer duration of breastfeeding up to age 12 months would be a protective factor for dental caries, while breastfed > 12 months would be a risk factor [ 13 ]. The relationship between breastfeeding and development of ECC is still a contentious issue and further investigations are needed.
However, there are some potential limitations of this study, such as recall bias and social desirability bias existed. In addition, the study has not assessed other potential indicators, including oral counts of mutans streptococci; maternal oral health status; and the numbers of people in the household. Further prospective studies are needed which would give a better insight into the complex multi-factorial etiology of dental caries.

Conclusions
The prevalence of ECC among Wenzhou 3-4 years old children was very high and most of the carious teeth were untreated. There appears to be a relationship between consumption of candies/chocolate, the age at which toothbrushing was started, whether parents supervised to brush or not, and parents' oral health knowledge level and ECC.

Bullet Points
Why this paper is important to paediatric dentists

Declarations
Ethics approval and consent to participate: This study was approved by the institutional review board of School and Hospital of Stomatology, Wenzhou Medical University. The purpose and details of this study was explained, and written informed consent was obtained from parents or legal guardians of the participants.

Consent for publication:
Not applicable Availability of data and materials: The datasets analyzed during the current study will not be publicly available to protect patient confidentiality.

Competing interests:
The authors declare that they have no actual or potential conflicts of interest.

Funding:
The study was supported by Zhejiang province education department project (No. : Y201223271). Financially support of the funding body was received in the design of the study and collection of data.
Author's contributions: LM designed the studies, carried out the dental examination and drafted the manuscript; ZW performed the statistical analysis and participated in its design; QL collected data, performed data analysis and made the charts in the manuscript; and XW carried out the studies, collected data, and helped to draft the manuscript. All authors read and approved the final manuscript. feeding with early childhood dental caries: Japanese population-based study. BMJ Open 2015;5:e006982.