Background
Oral disease is a major public health problem with a high prevalence and incidence, especially in low-income populations[
1]. More than half of China’s population resides in rural areas with lower average incomes than urban areas[
2]. In the third Chinese National Oral Health Survey, conducted in 2005, the dental caries prevalence among 5-year-old children was higher in rural areas (70.2%) than in urban areas (62%). In 2005, 28.6% of rural 12-year-olds had dental caries, a prevalence that had not declined significantly since the second Chinese National Oral Health Survey 10 years earlier[
3,
4]. Moreover, although average income had increased with growth of the rural economy[
5], the percentage of untreated carious teeth was also higher among rural children than urban children, with no obvious decrease since the previous survey. Additionally, gingival bleeding and calculus were prevalent conditions in rural China; calculus was present in 72.2% of 12-year-olds in western rural areas[
3].
The economy of Shaanxi Province in China ranks in the middle to lower level in China. There is little systematic data available from this region to analyze oral health status among its inhabitants. An oral epidemiological survey conducted in selected areas in Shaanxi Province in 1992 and 1993 showed that the caries prevalence was 36% among rural 5-year-olds and 18% among rural 12-year-olds[
6]. The third National Oral Health Survey (2005) reported that the prevalence of caries among rural 5-year-olds in Shaanxi Province was 58.5%[
7]. This value was far from the oral health goal established in 1994 by the World Health Organization that 90% of 5- to 6-year-olds should be caries-free by 2010. The current dental caries prevalence and gingival health status of rural children in Shaanxi Province were unknown before the present survey.
Adequate oral health knowledge is essential to instill appropriate oral health behavior to prevent oral diseases[
8‐
10]. Analysis of oral health knowledge, attitudes and behavior in a population allows us to determine the risk factors for oral diseases and to develop behavior modification strategies. However, information about the oral health knowledge, attitudes and behavior among rural children in Shaanxi Province has been scare. Therefore, the objectives of the present analysis were two-fold. Our first goal was to describe the oral health status, and oral health knowledge, attitudes and behavior among 4- to 6-year-olds and 12- to 15-year-olds in villages in Shaanxi Province, western China. Our second goal was to analyze the relationship between dental status and oral health knowledge, attitudes and behavior to identify the possible risk factors for dental caries and gingival bleeding in this population.
Methods
Sample size and selection of children
Multi-stage cluster sampling was used to select the sample in this study performed from March to May 2012, with assistance from the local health and education authority. The ethics committee of the School of Stomatology at Xi’an Jiaotong University approved this study.
The sample size was calculated based on the prevalence of dental caries reported by a recent survey in Yunnan Province, western China (73.6% among 5-year-olds and 53.5% among 12-year-olds)[
11], an error margin of 10%, a 95% confidence interval and a design effect of 1.5. The estimated sample size was 207 for 4- to 6-year-olds and 501 for 12- to 15-year-olds.
Because the objectives of the present survey were to describe the oral health status and risk factors of children living in villages in Shaanxi Province, and because children attending the township schools all lived in the villages, the sample was selected from township schools. In 2012, there were 90 townships in Shaanxi Province. With reforms in the distribution of primary and middle schools in Shaanxi Province from 2006 to 2010, there are generally one or two primary schools and one middle school in each township. According to our pre-survey, each primary school has approximately 150–200 students and each middle school has approximately 200 students. Details of our sampling strategy are as follows. First, the three major counties of Shaanxi Province were chosen for the survey, mainly based on their geographic location. Second, one rural township was selected in each region with simple random cluster sampling. Third, all 4- to 6-year-olds in the key kindergarten and key primary schools of each township were recruited, and all 12- to 15-year-olds in key middle schools were selected.
Questionnaire
The informed consent forms and structured questionnaires were provided to the 12- to 15-year-olds and to the caregivers of the 4- to 6-year-olds before the physical examination. The structured questionnaire, which collected information about the subject’s demographic background, oral health knowledge, attitudes and behavior, and perceived oral health conditions, had been used in the third National Oral Health Survey in China. If the children and their parents or caregivers agreed the study, the 12- to 15-year-olds and the caregivers of the 4- to 6-year-olds signed the informed consent. Then they were interviewed face-to-face by trained interviewers. To avoid potential information bias, interviewers explained the purposes and confidentiality of the survey and explained specifically that the study had no impact on participants’ examinations. Interviewers verified the completeness of questionnaires at collection.
Clinical examination
All children underwent a clinical examination to assess dental caries and 12- to 15-year-olds also underwent evaluation of their periodontal condition. Randomly selected duplicate examinations of 10% of participants were performed to assess inter-rater reliability of two examiners with Cohen’s kappa statistic. The kappa value was 0.7 about dental caries and 0.8 about the gingival bleeding, indicating a better agreement in the two examiners. The World Health Organization’s 1997[
12] caries diagnostic criteria for decayed, missing and filled teeth (DMFT) were used to evaluate dental caries status. Gingival bleeding and calculus of all teeth were examined in participating 12- to 15-year-olds by trained dentists using the World Health Organization’s method[
12] to evaluate periodontal condition (0 = no gingival bleeding, 1 = gingival bleeding, X = missing tooth; 0 = no calculus, 1 = calculus, X = missing tooth). Clinical examinations were performed under field conditions, with the use of plane mouth mirrors, CPI periodontal probes and portable clinic lights.
Data analysis
Seven questions were posed to 12- to 15-year-old students concerning the causes and prevention of tooth decay and gum disease; the caregivers of 4- to 6-year-olds were asked three oral health questions, mainly on prevention of tooth decay. A "dental knowledge score" was calculated by adding the total number of items answered correctly by the subjects, excluding responses such as, "do not know". Thus, dental knowledge scores ranged from 0 to 7 for 12- to 15-year-olds and from 0 to 3 for 4- to 6-year-olds, with higher scores indicating better dental knowledge. Four items concerning the importance of oral health were included to explore subjects’ attitudes toward oral health. Dental attitude scores were calculated by counting the total number of statements to which the subjects showed a positive attitude. This score ranged from 0 to 4, with a higher score indicating a more positive attitude. Sweets consumption was scored in this study based on frequency of consumption of desserts, sugar/chocolate, sugar water, carbonated beverages/juice and sweetened milk. For each type of sweet, 1 point = rarely or never consumed, 2 points = less than four times per month, 3 points = once per week, 4 = more than once per week but less than seven per week, 5 = once per day, 6 = more than once a day. Scores ranged from 0 to 30, with higher scores indicating more frequent consumption of sweets.
All data were entered in Microsoft Access with double entry. SPSS 17.0 statistical software (SPSS, Inc., Chicago, IL, USA) was used to analyze the data. Simple frequency tables and descriptive statistics (means and standard deviations) were processed and analyzed by chi-square and Fisher’s exact tests. To assess the relative effect of oral health knowledge, attitudes and behavior on the presence of dental caries and gingival bleeding, the scores for these items were first analyzed with bivariate associations. Those items associated with dental caries or gingival bleeding were further analyzed with multiple linear regression and logistic regression analysis, respectively.
Discussion
There is little systematic data available to analyze oral health status among village children in China. In the present study, the oral health status and related risks of children in this region were analyzed. Although this is a regional survey with a limited sample, it does provide insights into the oral health status and oral health knowledge, attitudes and behavior among rural children in western China. In the present study, the caries prevalence among 4- to 6-year-olds and 12- to 15-year-olds in the villages of Shaanxi Province were 67% and 23.9%, respectively. These values are similar to those reported by the third Chinese national survey among rural 5-year-olds and 12-year-olds in western China[
3]. The caries prevalence among 4- to 6-year-olds in the present survey was higher than that reported among 5-year-olds in developed countries, such as Norway[
13]. Moreover, caries prevalence in this population remains far from the oral health goal set in 1994 by the World Health Organization, that 90% of 5- to 6-year-olds should be caries-free by 2010. Additionally, dominant dt/DT-components were found both in rural 4- to 6-year-olds and in 12- to 15-year-olds in this study. The findings indicate that caries prevalence was relatively high among village children in Shanxi Province and that dental caries did not usually receive treatment, similar to the situation in most developing countries[
14‐
16]. The periodontal health condition of the 12- to 15-year-old rural children surveyed was generally poor, but it was slightly better than that reported among 12-year-olds in Laos[
15].
In general, oral health knowledge among 12- to 15-year-olds and among caregivers of 4- to 6-year-olds in the rural areas of Shaanxi Province was poor and was worse than that in southern China[
17,
18]. For example, only 28.3% of caregivers of 4- to 6-year-olds disagreed with the statement that dental caries in deciduous teeth did not require treatment, whereas the corresponding percentage in southern China was 51.6%[
18]. Lack of knowledge about fluoride toothpaste was found in 93.7% of 12- to 15-year-olds, a percentage higher than that among school children in Nepal[
16]. Additionally, oral health information was primarily received from television and radio, a finding similar to that among adults of Guangdong Province in southern China[
17]. Although oral health education programs such as the annual Love Teeth Day campaign to encourage the implementation of oral health education have been conducted since 1989[
19], education at school was indicated as a source of oral health information by only 5% of 12- to 15-year-olds in the present survey. This low percentage indicates that oral health education programs are less common in rural areas in western China and that they should be enhanced in these areas. Although Shaanxi remains a relatively poor province in China, with the continuous economic growth of the last 20 years, television was present in 100% of the rural participants’ homes in this study, and television is a primary means of disseminating oral health messages to the rural population. Thus, more oral health education could be conducted via television to improve oral health knowledge among village children. Despite their poorer dental knowledge, the subjects in this study held very positive attitudes toward oral health, similar to those found among children and adults in Guangdong Province in southern China[
17], a finding that might be partly explained by over-reporting.
Few participants in this survey reported tooth brushing at least twice daily and very few were using fluoridated toothpaste, percentages worse than those found in central and eastern China[
3] and in other developing[
15,
16,
20] and developed countries[
21]. These findings may result from poor oral health knowledge in this region. Toothache was the most common reason for the most recent dental visit, and preventive dental care was very uncommon. These results indicate that rural children lack awareness of how to prevent dental disease.
To assess the possible risk factors for dental caries and gingival bleeding, oral health knowledge, attitude and behaviors were evaluated with bivariate associations and multiple regression analysis. Many studies have reported an association between oral health knowledge scores and oral health status[
8,
9,
17], an association confirmed among 12- to 15-year-olds in the present study. This association suggests that oral health knowledge should be enhanced via increased oral health education among village children to improve their oral health status. However, the oral health knowledge of the caregivers of 4-to 6 year-olds was not associated with dental caries among the children, a result not consistent with that of another survey[
22]. Additionally, higher frequency of sweets consumption was associated with higher dmft among the 4-to 6 year-olds in this survey. Previous studies have found a similar correlation[
23,
24], suggesting that preschool oral health education should focus on the consumption of sugars to more effectively prevent deciduous dental caries. However, no significant association between sweets consumption and DMFT scores was found among 12-to 15-year-olds, a finding similar to that reported in a previous study[
15]. Frequent tooth brushing was strongly associated with lower DMFT scores and less gingival bleeding in 12- to 15-year-olds in the present study, whereas no significant association was found among 4-to 6-year-olds. This difference might be explained by the fact that most of the 4- to 6-year-olds seldom brushed their teeth, suggesting that tooth brushing should be encouraged in rural areas. Additionally, high caries values were found to be associated with a recent dental visit among village children in Shaanxi province. This finding agreed with that of a survey in Laos, and somewhat indicated that dental visits are often prompted by pain and discomfort rather than by the need for regular preventive care[
15].
Conclusion
Dental caries prevalence among 4- to 6-year-old village children in Shaanxi Province, western China, was relatively high, while the prevalence of dental caries among 12- to 15-year-olds was low, although periodontal condition was poor in that age group. Moreover, children lacked knowledge about dental caries, gum disease and the use of fluoride. A strong association was found between sweets consumption and the presence of dental caries among 4- to 6 year-old village children. Preschool oral health education should emphasize reduced consumption of sugars in the rural areas of Shaanxi Province. Tooth brushing and oral health knowledge were inversely associated with dental caries and gingival bleeding in 12- to 15-year-olds. More oral health education programs should be organized in rural schools to improve oral health knowledge and the frequency of tooth brushing in this population.
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Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
JG performed the clinical examinations and drafted the manuscript. JR designed the study and helped to draft the manuscript. LZ participated in administering the questionnaire. HZ participated in study design. RH and JT performed statistical analysis. All authors read and approved the final manuscript.