Dental caries prevalence and caries-associated risk factors of students aged 12–15 in Xide County of Liangshan Prefecture, China: a cross-sectional study

Abstract

Objective

About 2 billion people have caries in permanent teeth, and 514 million children have caries in primary teeth worldwide. Regional disparities in caries prevalence are evident in various areas of China. A comprehensive understanding of the status of dental caries and its associated risk factors is essential for developing effective dental health policies in economically disadvantaged regions. Thus, this study aims to examine the prevalence of dental caries and its risk factors among students aged 12–15 in Xide County, a remote mountainous area in China.

Design

In this cross-sectional study, dental health surveys were conducted using self-administered questionnaires and the Decayed-Missing-Filled Tooth (DMFT) Index. An oral clinical examination was carried out by the criteria and guidelines set forth by WHO.

Setting

Xide County, Liangshan prefecture, China in 2022.

Participants

558 students aged 12–15 years completed the survey.

Results

The study conducted in Xide County found a dental caries prevalence of 42.5% among 12–15 year-old students, with a mean DMFT of 1.50 (SD=2.25). Multivariable logistic regression analysis identified several significant risk factors for dental caries (p<0.05), including starting brushing after the age of six (OR 0.34, 95% CI 0.17 to 0.65), brushing teeth less than once a day (OR 9.24, 95% CI 5.53 to 15.33) and consuming carbonated drinks more than once a day (OR 0.28, 95% CI 0.14 to 0.53). Additionally, the use of fluoride (OR 0.61, 95% CI 0.43 to 0.85) and awareness of its protective effect on teeth (OR 0.75, 95% CI 0.59 to 0.98) were found to be associated with a lower risk of dental caries (p<0.05).

Conclusion

The prevalence of dental caries among students aged 12–15 in Xide County was identified as a significant public oral health concern. The oral health behaviours of students were found to be influenced by factors at the family and community levels.

STRENGTHS AND LIMITATIONS OF THIS STUDY.

• Participants exhibited homogeneity in terms of age and geographic background.

• Rigorous training and standardisation of examiners, following guidelines established by the WHO, ensure the comparability of results.

• The use of questionnaires in this study to gather information on subjects’ previous oral habits may introduce recall bias.

Introduction

Dental caries is the most prevalent oral condition, affecting 530 million children and 2.3 billion adults worldwide.¹ The burden of dental caries can last a lifetime as once the tooth structure is destroyed, it will need restoration and additional maintenance throughout life.² The effects of dental caries on children include pain, swelling, difficulty in eating and speaking, temporomandibular joint dysfunction,^{3 4} impact on quality of life⁵ and costs for individuals and society.⁶

According to the Third National Oral Survey of China, dental caries affect 28.9% of the population. Although caries prevalence has fallen in the past 30 years, great variations exist between and within populations.⁷ Low socioeconomic status was associated with severe caries and less use of dental services.⁸ Xide County, a state-level poor county in Liangshan, located in the southwest Sichuan Province of China, has a population of 158 139. With poor oral healthcare awareness, insufficient preventive measures and unavailable dental health services, dental caries in Xide County remain extremely common.

The investigation of dental caries status and its risk factors is helpful for the government in formulating effective oral health policies. However, the data on adolescent dental caries are unavailable in Xide County. The students aged 12–15 are in the early period of permanent dentition and can be used to study the severity and the development trend of dental caries.^{9 10} Therefore, this study aims to investigate the dental caries status and analyse the caries-related risk factors among 12–15 year-old students in Xide County, contributing to effective public dental health policy development.

Methods

Patient and public involvement

The public and patients were not involved in the study’s design, conduct, report or dissemination plans.

Study design

A cross-sectional survey was conducted in Xide County, Liangshan Prefecture, China in 2022.

Design

To determine the required sample size, the following formula was used:

$${\displaystyle n=deff\frac{{\mu }^{2}p\left(1-p\right)}{{\epsilon }^2}}$$

Where n is the sample size, deff is the design effect set as 1, $\mu$ is the level of confidence, p is the caries prevalence 28.9% (according to the Third National Oral Survey of China) and $\epsilon$ is the margin of error. The non-response rate is set as 20%. This estimation resulted in a final sample size of 607.

A stratified cluster sampling method was adopted to recruit students aged 12–15 years in four grades from nine schools. We stratified by grade and took the class as a cluster, amounting to 639. Exclusion criteria were (1) parents who had psychiatric or cognitive dysfunctions, (2) students who were unable to cooperate with the examiner or (3) students whose answers to the questionnaire survey were missing or illogical. Therefore, a total of 558 students were enrolled according to the exclusion criteria.

Oral examination

The clinical examinations were performed by three dentists from The First Affiliated Hospital of Ningbo University. To assess dental caries, the visual examination combined with probing was carried out using an artificial light source, a flat oral mirror and a No.5 probe in a supine position. Before the inspection, the dirt on the surface of the teeth was cleaned and dried out to ensure accurate results. Decayed, missing, and filled teeth (DMFT) following the WHO criteria was used to evaluate dental caries.¹⁰

Quality control

A standard examiner (SS) trained the three examiners. Each examiner was calibrated with the standard examiner and other examiners by assessing 10 students on two occasions 1-month apart. The 10 students were enrolled in this study and were randomly selected. A further 5% of the samples were randomly re-examined to test the reproducibility of interexaminer and intraexaminer, guaranteeing the Kappa value ranged from 0.81 to 0.96.

Questionnaire survey

Structured questionnaires (online supplemental table 1, the first part of the questionnaires was taken by the participants, and their parents took the second part.) were used to collect information including

1. Social demographic factors: age, gender, fathers’ education level and mothers’ education level.

2. Dental health behaviours: age at first brush, toothbrushing frequency, toothbrushing method, dessert frequency, soft drink frequency and fluoride toothpaste usage.

3. Dental health attitude: health self-assessment, tooth status self-assessment and dental health importance.

4. Dental health knowledge: is gum bleeding normal when brushing teeth? Are gum infections and dental caries caused by bacteria? Does fluoride help protect teeth? Does pit and fissure sealant help protect teeth?

5. Troubles caused by dental problems: pain, eating and communicating.

Four experts (two epidemiology and health statistics professors and two chief clinical dentists) modified the questionnaire.

Data analysis

IBM SPSS (SPSS V.24.0 for Windows, Chicago, Illinois, USA) was used for all statistical analyses. χ² or Fisher’s exact tests were conducted to compare the prevalence of dental caries among different groups and evaluate the related variables. Logistic regression analysis was performed to estimate the relationship between dental caries and its risk factors. Results were expressed as means and standard deviations (mean±SD) and the significance level was set at p<0.05.

Results

A total of 613 students aged 12–15 years old participated in this study, and their parents were provided with a questionnaire. Missing answers and illogical data were resolved by contacting parents through a telephone interview. Finally, we enrolled a total of 558 students with complete information. This study obtained a response rate of 91.03%. The Kappa values used to evaluate the reproducibility of interexaminers and intraexaminers ranged from 0.81 to 0.96.

Social demographic factors

The mean age of the 558 students was 13.13 (SD=1.14) years. 52.5% of them (293 students) were males while 47.5% (265 students) were females. A total of 237 (42.5%) students experienced dental caries in permanent teeth and the mean value of DMFT was 1.50 (SD=2.25). The prevalence of dental caries was slightly lower in females (41.5%) than in males (43.3%), but there was no statistically significant difference. Also, the difference was not statistically significant between the age groups. As for the parent education level, most fathers (51.4%) and mothers (74.3%) received an education of fewer than 9 years. The prevalence of dental caries decreased with a higher father or mother education level but the statistical difference was not significant.

Dental health behaviours

The mean age of the participants at first brushing their teeth was 5.98 (SD=2.49). Approximately 40.5% of the participants didn’t brush their teeth until they were 7 years old. According to the statistical results, the caries prevalence of students who started brushing before 6 years old was significantly lower than those who started brushing after 6 years old (p<0.05). As table 1 shows, students who brushed their teeth more than once a day suffered lower caries prevalence (32.6%) than those who brushed only once a day (45.4%) and less than once a day (47.5%), with the difference statistically significant (p<0.05). In terms of diet, both desserts and carbonated drink consumption more than once a day were associated with a higher prevalence of dental caries (p<0.05). Approximately one-third of all respondents were unaware of fluoride use, and the prevalence of dental caries was statistically different in the group (p<0.05). No significant toothbrushing method-related difference.

Table 1. Prevalence of dental caries in different groups.

Variable	Category	Dental caries		P value
		Presence	Absence
Total		237 (42.5%)	321 (57.5%)
Social demographic factors
Sex	Male	127 (43.3%)	166 (56.7%)	0.669
	Female	110 (41.5%)	155 (58.5%)
Age (years old)	12	97 (41.5%)	137 (58.5%)	0.974
	13	51 (42.5%)	69 (57.5%)
	14	45 (43.3%)	59 (56.7%)
	15	44 (44.0%)	56 (56.0%)
Father’s educational level (years)	<9	134 (46.7%)	153 (53.3%)	0.104
	9–12	87 (38.7%)	138 (61.3%)
	>12	16 (34.8%)	30 (65.2%)
Mother’s educational level (years)	<9	184(44.3%)	231 (55.7%)	0.241
	9–12	44 (38.6%)	70 (61.4%)
	>12	9 (31.0%)	20 (69.0%)
Dental health behaviours
Age at first brushing (years old)	<7	127 (38.3%)	205 (61.7%)	<0.05
	>6	110 (48.7%)	116 (51.3%)
Toothbrushing frequency (times/day)	<1	114 (47.5%)	126 (52.5%)	<0.05
	1	94 (45.4%)	135 (54.6%)
	>1	29 (32.6%)	60 (67.4%)
Toothbrushing method	Horizontally	92 (41.8%)	128 (58.2%)	0.390
	Vertically	25 (34.2%)	48 (65.8%)
	Mixed	23 (43.4%)	30 (56.6%)
	Casually	97 (45.8%)	115 (54.2%)
Frequency of desserts intake (times/day)	<1	38 (33.3%)	76 (66.7%）	<0.05
	1	53 (39.0%)	83 (61.0%)
	>1	146 (47.4%)	162 (52.6%)
Frequency of carbonated drink intake (times/day)	<1	52 (33.3%)	104 (66.7%)	<0.05
	1	46 (37.1%)	78 (62.9%)
	>1	139 (50.0%）	139 (50.0%)
Use of fluoride	Yes	24 (31.2%)	53 (68.8%)	<0.05
	No	109 (36.2%)	192 (63.8%)
	Unknown	104 (57.8%)	76 (42.2%)
Dental health attitude
Health self-assessment	Good	91 (43.1%)	120 (56.9%)	0.514
	Generally	107 (44.0%)	136 (56.0%)
	Bad	39 (37.5%)	65 (62.5%)
Tooth status self-assessment	Good	56 (39.4%)	86 (60.6%)	0.654
	Generally	167 (43.3%)	219 (56.7%)
	Bad	14 (46.7%)	16 (53.3%)
Dental health importance	Agree	213 (43.6%)	276 (56.4%)	0.165
	Disagree	9 (47.4%)	10 (52.6%)
	Unaware	15 (30.0%)	35 (70.0%)
Dental health knowledge
Is gum bleeding normal when brushing teeth?	Agree	36 (43.4%)	47 (56.6%)	0.738
	Disagree	176 (41.7%)	246 (58.3%)
	Unknown	25 (47.2%)	28 (52.8%)
Are gum infection and dental caries caused by bacteria?	Agree	145 (41.5%）	204 (58.5%)	0.597
	Disagree	31 (40.3%)	46 (59.7%)
	Unknown	61 (46.2%)	71 (53.8%)
Does fluoride help protect teeth?	Agree	47 (35.6%)	85 (64.4%)	<0.05
	Disagree	55 (37.2%)	93 (62.8%)
	Unknown	135 (48.6%)	143 (51.4%)
Does pit and fissure sealant help protect teeth?	Agree	50 (41.7%)	70 (58.3%)	0.073
	Disagree	83 (37.4%)	139 (62.6%)
	Unknown	104 (48.1%)	112 (51.9%)
Trouble caused by dental problem
Pain caused by dental problems	Never	109 (41.8%)	152 (58.2%)	0.741
	Occasionally	106 (42.2%)	145 (57.8%)
	Always	22 (47.8%)	24 (52.2%)
Eating troubles caused by dental problems	Never	140 (43.3%)	183 (56.7%)	0.446
	Occasionally	80 (43.2%)	105 (56.8%)
	Always	17 (34.0%)	33 (66%)
Communicating troubles caused by dental problems	Never	207 (42.0%)	285 (58.0%)	0.869
	Occasionally	13 (44.8%)	16 (55.2%)
	Always	17 (46.0%)	20 (54.0%)

Dental health attitude and knowledge

The dental health attitude survey showed that 243 (43.5%) students rated their general health as fair and 386 (69.1%) students self-assessed their tooth status as general. Almost all participants (87.6%) agreed on the importance of oral health to general health, while a few (9.0%) were not aware. From the dental health knowledge survey result, most of the participants (75.6%) disagreed that it is normal to bleed when brushing teeth. 62.5% of students agreed that gum infection and dental caries were caused by bacteria. Remarkably, few (21.5%) approved pit and fissure sealants could help protect teeth. The data also indicated that students with a high awareness of dental caries prevention by fluoride toothpaste had a lower prevalence of dental caries (p<0.05). As for troubles caused by dental problems, there was no statistical difference in pain, eating troubles and communication troubles between caries and caries-free groups.

Multivariable logistic regression analysis

Table 2 indicates the results of the logistic regression analysis. Age at first brushing, frequency of brushing teeth, frequency of dessert intake, frequency of carbonated drink intake, use of fluoride and dental health knowledge about whether fluoride could help protect teeth were displayed as risk factors. Among these, starting brushing after 6 years old, brushing teeth less than once a day and consuming carbonated drinks more than once a day were the most critical risk factors for dental caries among 12–15 year-old students in Xide County. On the contrary, the use of fluoride and awareness of its protective effect on teeth could reduce the risk of dental caries.

Table 2. Multivariable logistic regression analysis of risk factors.

Variable	B	SE	Wald	P value	OR	95% CI
Age at first brushing	−1.08	0.33	10.56	<0.05	0.34	0.17 to 0.65
Frequency of brushing teeth	2.22	0.26	74.56	<0.05	9.24	5.53 to 15.33
Frequency of dessert intake	0.09	0.31	0.08	0.76	1.09	0.60 to 2.01
Frequency of carbonated drink intake	−1.29	0.33	15.55	<0.05	0.28	0.14 to 0.53
Use of fluoride	−0.50	0.17	8.32	<0.05	0.61	0.43 to 0.85
Does fluoride help protect teeth?	−0.28	0.13	4.43	<0.05	0.75	0.59 to 0.98

B, regression coefficient;, standard error, Wald, Chi-squareχ2 value.; OR odds ratios

Discussion

The prevalence of dental caries has shown a recent increase in many developing countries compared with developed countries. China, as the largest developing country globally, has been the subject of numerous studies examining the dental caries status among its population.¹¹ However, variations in dental caries status across regions are attributed to differences in cultural practices, economic conditions, educational attainment and dietary habits. This study aimed to assess the dental issues among 12–15 year-old students in Xide County, Liangshan prefecture, and investigate a potential association between these variables and dental caries.

The third Chinese Oral Survey conducted in 2005¹² reported a dental caries prevalence of 28.9% in 12-year-old children, with a mean DMFT of 0.54. In contrast, the prevalence of dental caries (42.5%) and mean DMFT (1.50) in Xide County (42.5%) was significantly higher than the national average. The presence of underdeveloped regional economies and inadequate medical resources likely played a role in the observed poor oral hygiene and dietary habits.¹³ Furthermore, a study examining the oral health of children in 8446 families in Wuhan, China, revealed a notable correlation between parental education levels and the frequency of toothbrushing. Specifically, children with parents possessing higher levels of education were more inclined to brush their teeth at least two times per day. This finding may have also contributed to the higher prevalence of dental caries in Xide County compared with Wuhan.¹⁴

The efficacy of toothbrushing in preventing dental caries has been substantiated in previous studies.^{15 16} Regular brushing can promote optimal oral hygiene by reducing plaque accumulation, thereby influencing the survival and acid production of oral bacteria.^{17 18} Research indicates that establishing proper oral hygiene habits in childhood can lead to the maintenance of these habits in adulthood.^{17 19} A study revealed that a significant portion of students did not begin brushing their teeth until they reached primary school, suggesting a lack of adequate oral health education, possibly due to the educational background of their parents. Furthermore, the study identified a correlation between the frequency of toothbrushing and the incidence of dental caries. Individuals in Xide County who reported brushing their teeth more than once a day exhibited lower levels of caries compared with those who reported less frequent toothbrushing. The findings of this study support the efficacy of toothbrushing in caries prevention, consistent with previous research.²⁰,²²

The consumption of sugar-containing foods and beverages has been linked to elevated rates of dental caries and erosion.²³,²⁵ In the present investigation, individuals who frequently consumed desserts or carbonated beverages exhibited a higher prevalence of caries, with statistical significance (p<0.05). Sugars serve as a source of energy and nutrients for bacterial growth, a key determinant in the development of dental caries. Over time, excessive sugar intake can result in the creation of an acidic oral environment and demineralisation of enamel, ultimately increasing the risk of dental caries.^{26 27} Research indicates that restricting sugar intake to 5% of total energy consumption can be advantageous in reducing the likelihood of developing dental caries.²⁷ Consequently, it is proposed that modifications in oral hygiene practices and dietary patterns potentially mitigate or eradicate the aetiology of dental caries.

The fluoride application is another strategy to increase tooth resistance to caries. Moreover, fluoridated water, salt and milk were successful in public prevention.²⁸ In the present study, a correlation was observed between the use of fluoride and knowledge of its preventive effects on dental caries among students, aligning with findings from previous literature.²⁹,³¹ In Xide County, there was a lack of public awareness regarding dental health among parents, schools and health administration departments. Sufficient and correct dental health knowledge can effectively reduce the prevalence of dental caries. Therefore, it is recommended that efforts be made to enhance the dissemination of dental health knowledge in Xide County to prevent dental caries effectively.

This study presents multiple strengths, including participant homogeneity in age and geographic background, detailed data collection based on school affiliation leading to a high response rate, rigorous training and calibration of the examiners and adherence to WHO standards for results comparable. However, it is important to acknowledge the limitations of this study, notably the inability to draw causal inferences from cross-sectional studies. It was also difficult to avoid some limitations with cross-sectional data, such as selection and recall bias. Subsequent research endeavours will conduct randomised controlled trials to validate a causal relationship.

Conclusion

The current cross-sectional study identified a notable prevalence of dental caries among students aged 12–15 in Xide County, highlighting a significant public health concern. Emphasising the importance of oral hygiene for caries prevention, it is imperative to promote the adoption of oral health habits among children. Furthermore, educational initiatives on dental health should be implemented by schools and health administration departments.

Data availability statement

Data are available upon reasonable request.