Oral health status and associated factors among 12 to 15-year-old Chinese adolescents in Southeast China: A cross-sectional study

Abstract

This study assessed oral health conditions and associated factors (including sociodemographic characteristics and self-reported oral health-related behaviors) among Chinese adolescents. This cross-sectional study enrolled 3840 adolescents aged 12 to 15 years from 12 middle schools in Foshan, Southeast China, in 2016, using multistage, stratified cluster sampling. Participants underwent a clinical oral examination and completed a questionnaire. The prevalence of dental caries, probe bleeding, and calculus was 37.6%, 46.2%, and 39.7%, respectively; the mean decayed/missed/filled teeth index was 0.86 ± 1.58. A mean of 2.09 ± 3.65 and 1.85 ± 3.52 teeth showed probe bleeding and calculus, respectively. Only 0.3% and 0.1% of adolescents aged 15 years had periodontal pockets (depth ≥ 4 mm) and attachment loss, respectively, which were most common in tooth positions 46 and 36 (Federation Dentaire International 2-digit system). Regarding oral health-related behavior, 49.1% of the participants failed to brush their teeth at least twice daily, 98.5% never or rarely used dental floss, and 58.7% reported middle–high frequency sugar consumption. Older age, female, administrative region, maternal education lower than university, brushing teeth less than twice daily, flossing less than once daily, and frequent sugar consumption were significant risk factors of caries. Older age, female, administrative region, brushing less than twice daily, and flossing less than once daily significantly increased periodontal risk. Despite the overall low prevalence of adverse dental conditions among adolescents in Foshan, their oral hygiene habits were undeveloped. Thus, their identified risk factors need close monitoring, and families, schools, communities, and the government should jointly promote adolescents’ oral health.

1. Introduction

According to the Global Burden of Disease Study 2017, approximately 3.5 billion people worldwide have oral diseases, including caries, periodontal disease, and oral cancer. Nevertheless, these conditions are preventable through adequate oral health awareness, healthy behavior, and preventive treatment.^[1,2] In 2019, The Lancet published a series of papers highlighting the global health challenge of oral disease, the need to end global oral health neglect, and the necessity of radical action, especially regarding oral disease prevention and healthcare systems reform.^[3,4]

Permanent teeth, replacing deciduous teeth, play an important role throughout an individual life. The protection of permanent teeth has become an urgent concern, especially since oral health is a fundamental component of general health.^[5] Oral health problems may cause loss of school time and poor school performance, negatively affect their development, exacerbate social inequality,^[6] and decrease life quality,^[7] particularly among adolescents. Studies have shown that oral diseases share common risk factors with other non-communicable diseases.^[4,8] Nevertheless, many dental problems experienced during adolescence can be treated. However, the lack of timely prevention and control may cause irreversible harm during adulthood.

In China, adolescent oral health receives inadequate attention due to historical, cultural, and political factors. According to the Fourth National Oral Health Survey of China held in 2015 to 2016, caries prevalence (decayed, missed, filled teeth index [DMFT] > 0) was 38.5% (mean DMFT score = 1.04) among adolescents aged 12 to 15 years,^[9] and probe bleeding and calculus prevalence were as high as 61.0% and 67.3%, respectively.^[10] Moreover, the population oral health may largely differ among regions due to China vast territory, which has resulted in uneven economic development and great differences in culture, eating habits, and customs. A national-level oral survey in China^[10,11] reports some epidemiological data on oral health status in Guangdong and 3 recent studies in Zhejiang (a province of East China),^[12] Yunnan (a province of Southwest China),^[13] and Shenzhen (a large city of Southeast China)^[14] report oral health problems in Chinese adolescents. However, these findings could not sufficiently provide an overall view of the oral health status of adolescents in Southeast China. Further, it may be inappropriate to extrapolate the conclusions of studies on adolescents in Zhejiang and Yunnan to those in Southeast China, or those of studies on the populations of Shenzhen, a large city, to populations of medium-sized or small cities. Medium-sized cities account for the majority of China urban agglomeration, which is highly representative economically and culturally; thus, it is necessary to increase oral health research on medium-sized cities.

We aimed to assess the oral health conditions and associated factors (including sociodemographic characteristics and self-reported oral health-related behaviors) of adolescent students aged 12 to 15 years in Foshan, a typical, medium-sized city located in Southeast China, in 2016. The findings are expected to support interventions and policies for promoting the oral health of the adolescent population in middle-sized cities of Southeast China.

2. Methods

2.1. Study design and setting

This was a cross-sectional study on participants aged 12 to 15 years. The study was conducted between 2016 and 2017 in Foshan, a typical, medium-sized city in Southeast China located in the central part of Guangdong Province, divided into 5 districts: Chancheng, Shunde, Nanhai, Sanshui, and Gaoming (Fig. 1). Owing to its location in the core area of the Pearl River Delta Economic Circle, its economic development ranks among the top 3 in Guangdong Province. Before 2014, Guangdong Province implemented a strict family planning policy, advocating “a couple has only one child.” The participants included in this study were mainly born in 2000 to 2004, within the scope of the aforementioned policy. Therefore, the number of people corresponding to each age group was similar, and the same number of participants could be defined for each age group. To further eliminate the influence of internal composition (factors such as sex and administrative region) on the overall result, the same number of participants was set for subgroups by sex or region.

Figure 1.

Geographical map of Foshan, Guangdong Province, China and the flow chart of the sampling program.

This study was approved by the ethics committee of the Center for Oral Disease Control of Foshan (No. 201522). Written consent from adolescents and parents/guardians was collected before the implementation of the study. This study was conducted in full accordance with the Helsinki Declaration. All participants were examined in their middle schools.

2.2. Sample size calculation and participant selection

Multistage stratified cluster sampling method was planned to use in this study. The required sample size was calculated according to the following formula:

$${\displaystyle \begin{array}{l}{\displaystyle n=deff\frac{{u_{\alpha /2}}^{2}p(1-p)}{{\delta }^2}}\end{array}}$$

setting the design effect “deff” at 4.5, the level of confidence “μ_α/2” at 1.96, and the margin of error “δ” at 10%. Regarding the problem of within-cluster homogeneity brought about by whole cluster sampling, in this study, the deff coefficient used in the sample size calculation formula was set to 4.5 (consistent with the deff setting in the latest Chinese official sampling plan for oral health epidemiologic survey), in order to increase the sample size to 4.5 times of the sample size of simple random sampling, and thus to reduce the problem of reduced sampling efficiency brought about by cluster sampling. If “p” was set at 50.0%, the sample size was estimated to be 433. According to the Third National Oral Survey, dental caries prevalence and the detection rate of probe bleeding and calculus in a 12-year-old group were 28.9%, 57.7%, and 59.1%, respectively.^[15] Applying the above data to sample size calculations, we calculated the sample size between 356 and 422, that is, less than 433. The above was also applicable to the calculation of the sample size of other age groups (13–15 years old). Therefore, when the sample size for each age group was set to more than 433, the total sample size was not only suitable for dental caries, but also for periodontal conditions (including probe bleeding and calculus). To facilitate implementation, a sample size of 960 for each age group was finalized, yielding a total sample size of 3840.

Accordingly, the multistage stratified cluster sampling method was applied. In the first stage, 4 of the 5 districts of Foshan City (Chancheng, Shunde, Nanhai, and Sanshui) were selected: the first 3 represented the faster-developing regions and the last one represented the less developed region. In the second stage, 3 middle schools were randomly selected from each district, summing to 12 middle schools. In the third stage, the cluster sampling method was used to select 320 adolescents aged 12 to 15 years from each middle school, with 80 included in each of 4 age groups (12–15 years); the ratio of boys to girls per group was 1:1. Students within each age and sex group were randomly selected from the eligible candidates listed on the students’ registration records provided by the administrative offices of these middle schools. In this on-site survey, 3840 adolescents completed clinical examinations and questionnaires and were included in the statistical analyses. Please see Figure 1 for details of the sampling program.

2.3. Oral examination

Each participant underwent a clinical oral examination in his/her school. The results of the examination were recorded on a standardized checklist used in the 4th National Oral Health Survey. The examination methods and standards were formulated according to the latest examination standards recommended by the World Health Organization (2013).^[16] Clinical examinations were conducted in the form of visual inspection under an artificial light source and combined with consultation when necessary. The examiners used a set of unified instruments, including portable dental chairs, disposable plane mouth mirrors attached to an intraoral light-emitting diode light, and community periodontal index probes. The Federation Dentaire International system (FDI) 2-digit system was used when referring to specific teeth. The dental status was evaluated using the following indices and calculation formulas: DT = number of decayed teeth; missed teeth = number of missing teeth due to caries; FT = number of filled teeth; caries prevalence (DMFT > 0) = number of patients with caries/number of people tested*100%; mean DMFT score = decayed, missing, and FT/number of people tested. The periodontal status was evaluated by assessing probe bleeding and calculus. Based on the above examination and indices, 2 additional indices were included for participants aged 15 years, namely, periodontal pocket depth and attachment loss.

The examiners responsible for the oral clinical examination were dentists, had been engaged in oral clinical work for more than 3 years, and had participated in the Fourth National Oral Health Survey. They underwent a week-long unified theoretical training and practice specifically for this study before data collection. Those responsible for recording the examination results were dentists or nurses with oral health clinical experience. Fifteen survey participants were selected for trial, and standard consistency tests were performed on the examination results of different doctors and on the same doctor 2 examination results of the same participant. All Kappa values were > 0.8, indicating that the technical error among examiners was small. Moreover, the diagnostic error originating from the examiner was also small.

2.4. Self-reported questionnaire

A standardized questionnaire, used in the 4th National Oral Health Survey, was provided to all participants after the clinical examination. The participants were asked to fill out the questionnaire on site. Each participant completed the questionnaire and submitted it to the investigator for verification before leaving the survey site. The investigators responsible for the questionnaire survey had been trained uniformly by the technical group of the Fourth National Oral Health Survey in China and were trained specifically for this study for 1 week before data collection. They checked whether the questionnaires were filled completely and accurately. When problems were found, the participants were contacted and asked to make corresponding corrections in time. Each survey site was equipped with 3 examiners, 3 recorders, and 1 questionnaire investigator.

The information collected included family background, sugar consumption habits, and oral hygiene behavior. Family background included age, sex, household registration (hukou), administrative region, being an only child or not, and parental education level. For age, 4 groups were scored as follows: “12-year-old” was scored as 1, “13-year-old” as 2, “14-year-old” as 3, and “15-year-old” as 4. For sex, 2 groups were scored as follows: “female” as 0 and “male” as 1. For household registration (hukou), 2 options were scored as follows: “rural” as 0 and “urban” as 1. For administrative region, the 4 districts were scored as follows: “Chancheng” as 1, “Nanhai” as 2, “Shunde” as 3, and “Sanshui” as 4. For being an only child or not, “no” was scored as 0 and “yes” as 1. For father or mother education level, the options were scored as follows: “middle school or below” as 1, “high school” as 2, and “university or above” as 3.

Sugar consumption habits were measured by the frequency of consuming sweet foods, including the following 3 typical categories: sweet dessert (biscuit/cake/bread) and candy (chocolate and sugary gum), sweet drinks (sweet water/cola and other carbonated beverages, orange/apple juice and other juices, and lemonade and other non-fresh juices), and sweetened milk/yoghurt/tea/coffee. Six options were provided to the participants per category and scored as follows: “rarely or never” was scored as 1, “1 to 3 times a month” as 2, “once a week” as 3, “2 to 6 times a week” as 4, “once a day” as 5, and “more than 2 times a day” as 6. These scores were added together to obtain the total score, which was then divided into the following 4 categories: 3 to 6, 7 to 9, 10 to 12, 13 to 15, and 16 to 18, defined as low, relatively low, middle, relatively high, and high frequencies, respectively. Oral hygiene behavior was measured by the frequency of brushing teeth and using dental floss daily. For the frequency of brushing teeth, 4 options were provided to the participants and scored as follows: “never” was scored as 1, “<1 time/day” as 2, “1 time/day” as 3, and “≥2 times/day” as 4. For the frequency of flossing, 4 options were also provided and scored as follows: “never” as 1, “rarely” as 2, “1 time/day > f ≥ 1 time/week” as 3, and “≥1 time/day” as 4.

Smoking habits were also investigated in the questionnaire. Three options were provided to the participants and scored as follows: “never” was scored as 1, “1 time/day > f ≥ 1 time/week” as 2, “≥1 time/day” as 3.

2.5. Statistical analysis

All data were analyzed using SPSS Statistics version 20.0 (IBM Corporation, Armonk, NY, USA). Chi-squared tests were conducted to assess group differences in the prevalence of dental caries (including DMFT, DT, missed teeth, and FT), probe bleeding, calculus, periodontal pocket, and attachment loss. The relationship between oral health status and related influencing factors was explored through logistic regression analysis. P < .05 was considered statistically significant. “I can’t remember” responses to the questionnaire were treated as missing values. The percentages presented in the tables were calculated after excluding the missing values. If the samples had missing values for the corresponding variables, then these samples with missing values were excluded from the model in the regression analysis.

3. Results

The final sample comprised 3840 participants aged 12 to 15 years, of whom 1030 (26.8%) were from single child homes. As 39 students planned to be investigated were not in school due to illness, a corresponding number of students were invited to participate in the survey to ensure that the number of adolescents remained at 3840. In total, 1563 (40.7%) adolescents were from an urban area. The rate of missing data in many key variables, except “father educational level” and “mother educational level,” was 0% to 0.13%; 490 (12.8%) adolescents did not know their father educational level and 471 (12.3%) did not know that of their mother. DMFT scores and the number of teeth with probe bleeding, calculus, periodontal pocket, or attachment loss were not normally distributed in this study.

The prevalence of dental caries (DMFT > 0) was 37.6% (referring to per person, the mean number of teeth with caries was 0.86 ± 1.58) (Tables 1 and 2) and that of probe bleeding and calculus was 46.2% and 39.7%, respectively. The mean number of teeth (referring to per person) with gingival bleeding and calculus was 2.09 ± 3.65 and 1.8 ± 3.52, respectively. Only 0.3% and 0.1% of 15-year-old adolescents had periodontal pockets (depth ≥ 4 mm) and attachment loss, respectively. The first permanent molar of the mandible (tooth positions 46 and 36) was the most commonly registered tooth with dental caries. Approximately 18% and 12% of the adolescents had DMFT > 0 and DT > 0, respectively, in this tooth position (Fig. 2). The top 3 tooth positions prone to caries were the first permanent mandibular (tooth positions 46 and 36) and maxillary molars (tooth positions 16 and 26) and the second permanent mandibular molars (tooth positions 47 and 37).

Table 1.

Oral health status of 12 to 15-yr-old adolescents presented in groups by sociodemographic factors in Foshan, China.

	N (%)	DMFT (%)				Teeth number > 0 (%)
		DMFT > 0	DT > 0	MT > 0	FT > 0	Probe bleeding	Calculus	Period pocket*	Attachment loss
Total	3840 (100.0)	37.6	32.4	0.3	9.2	46.2	39.7
Age group
12-yr-olds	960 (25.0)	32.6***	28.1***	0.2	7.1	47.9	35.5***
13-yr-olds	960 (25.0)	34.7	28.6	0.3	9.5	45.0	37.1
14-yr-olds	960 (25.0)	41.3	36.4	0.1	10.2	47.5	41.0
15-yr-olds	960 (25.0)	42.0	36.4	0.6	10.0	44.6	44.9	0.3	0.1
Sex
Female	1920 (50.0)	42.3***	36.6***	0.4	10.5**	43.8**	38.2	0.2	0.2
Male	1920 (50.0)	33.0	28.2	0.2	7.9	48.8	41.0	0.4	0.0
Household registration (Hukou)†
Rural	2272 (59.2)	39.1*	34.5***	0.4	8.5	45.7	41.5**	0.2	0.2
Urban	1563 (40.7)	35.4	29.2	0.3	10.2	47.0	36.9	0.5	0.0
Administrative region
Chancheng	960 (25.0)	33.5***	28.8***	0.2	9.1**	52.0***	50.5	0.4	0.0
Nanhai	960 (25.0)	33.5	26.3	0.2	10.6	46.4	29.7	0.0	0.0
Shunde	960 (25.0)	44.7	39.0	0.2	10.5	42.0	40.6	0.8	0.4
Sanshui	960 (25.0)	38.8	35.5	0.6	6.6	44.7	37.7	0.0	0.0
Only child†
No	2809 (73.2)	38.4	33.5*	0.3	8.8	45.7	40.2	0.3	0.1
Yes	1030 (26.8)	35.5	29.2	0.4	10.3	47.8	38.3	0.4	0.0
Father education level†
Middle school or below	2096 (54.6)	39.1*	34.9*	0.2*	8.8	47.3	42.1**	0.3	0.0
High school	923 (24.0)	38.1	30.8	0.0	11.2	45.1	38.1	0.0	0.4
University or above	331 (8.6)	32.0	26.3	0.9	9.4	44.1	33.2	1.3	0.0
Mother education level†
Middle school or below	2358 (61.4)	38.9***	34.5***	0.3*	8.5**	47.6*	41.9***	0.3	0.0
High school	725 (18.9)	39.7	32.1	0.1	12.8	42.3	36.4	0.0	0.6
University or above	286 (7.4)	27.6	20.6	1.0	9.1	42.7	30.4	1.4	0.0

DMFT = decayed/missed/filled teeth index, DT = decayed teeth, FT = filled teeth, MT = missed teeth.

^*P ≤ .05.

^**P ≤ .01.

^***P ≤ .001.

*Periodontal.

^†Missing value: 1 to 490.

Table 2.

Oral health status of 12 to 15-yr-old adolescents presented in groups by oral health-related behavior factors in Foshan, China.

	N (%)	DMFT (%)				Teeth number > 0 (%)
		DMFT > 0	DT > 0	MT > 0	FT > 0	Probe bleeding	Calculus	Periodontal pocket	Attachment loss
Total	3840 (100.0)	37.6	32.4	0.3	9.2	46.2	39.7
Brushing teeth
Never	53 (1.4)	28.3	26.4*	0.0	3.8*	49.1*	39.6	0.0	0.0
<1 time/d	33 (0.9)	42.4	33.3	0.2	12.1	60.6	51.5	0.0	0.0
1 time/d	1799 (46.8)	38.9	34.6	0.4	7.9	48.1	40.7	0.4	0.0
≥2 times/d	1955 (50.9)	36.6	30.4	0.3	10.5	44.2	38.5	0.2	0.2
Using dental floss*
Never	3484 (90.7)	37.5	32.5	0.3	8.6***	46.8	40.2	0.3	0.1
Rarely	299 (7.8)	37.5	28.8	0.7	13.7	39.8	34.8	0.0	0.0
1 time/d > f ≥ 1 time/wk	28 (0.7)	42.9	42.9	0.0	21.4	57.1	40.9	0.0	0.0
≥1 time/d	27 (0.7)	48.1	37.0	0.0	22.2	40.7	22.2	0.0	0.0
Smoking*
Never	3763 (98.0)	37.7	32.4	0.3	9.3	46.3	39.5	0.1	0.3
Rarely	65 (1.7)	29.2	24.6	0.0	6.2	40.0	43.1	0.0	0.0
1 time/d > f ≥ 1 time/wk	4 (0.1)	75.0	75.0	0.0	0.0	75.0	50.0	0.0	0.0
≥1 time/d	7 (0.2)	42.9	42.9	0.0	0.0	57.1	57.1	0.0	0.0
Sugar consumption habits (frequency)*
Low	547 (14.2)	33.8**	28.9**	0.2	8.2	46.8	43.3	1.6	0.8
Relatively low	1031 (26.8)	36.2	30.7	0.3	8.7	47.2	39.2	0.0	0.0
Middle	1342 (34.9)	37.0	31.5	0.3	9.8	46.3	39.5	0.0	0.0
Relatively high	690 (18.0)	41.0	36.5	0.1	8.3	44.5	38.3	0.5	0.0
High	221 (5.8)	47.5	40.7	1.4	13.1	44.8	37.6	0.0	0.0

DMFT = decayed/missed/filled teeth index, DT = decayed teeth, FT = filled teeth, MT = missed teeth.

^*P ≤ .05.

^**P ≤ .01.

^***P ≤ .001.

*Missing value: 1 to 9.

Figure 2.

Permanent teeth caries status among adolescents in Foshan, China, presented by tooth position. Histogram of dental caries in different tooth positions in adolescents. The histogram shows the prevalence of DMFT and DT in the overall study population. N = 3840. DMFT = decayed, missed, filled teeth; DT = decayed teeth.

The most common tooth positions for probe bleeding exceeding 10% were 46, 12, 36, 13, 41, 31, and 42, while those most likely to have calculus exceeding 10% were positions 46, 36, 41, 31, 42, and 32 (Fig. 3). Most dental calculus was found in the first permanent molar of the mandible and mandibular incisor (in 15%–16% of the adolescents). Periodontal pockets and attachment loss were relatively rare and were thus not included in the histogram of Figure 3.

Figure 3.

Periodontal status among adolescents in Foshan, China, presented by tooth position. Histogram of the periodontal health of adolescents in different tooth positions. The histogram shows the prevalence of probe bleeding and dental calculus in the overall study population. N = 3840.

Regarding oral health-related behavior, 49.1% of the participants failed to brush their teeth at least twice daily, 98.5% never or rarely used dental floss, and 58.7% consumed sugar at middle to high frequency.

Single-factor analysis showed that age, sex, household registration (hukou), administrative region, parents’ education level, and sugar intake frequency were significant factors that affected dental caries prevalence. Regarding the periodontal status, sex, administrative region, mother education level, and teeth brushing significantly affected probe bleeding prevalence. Moreover, age, household registration (hukou), administrative region, and parents’ education level significantly affected dental calculus prevalence.

Multifactor analysis revealed age, sex, household registration (hukou), administrative region, mother education level, frequency of brushing teeth, frequency of flossing, and frequency of sugar consumption as being significantly associated with oral diseases or problems.

Binary logistic regression analysis (Table 3) showed that older age was a shared risk factor for dental caries and calculus. The 12-, 13-, and 14-year-old groups were less likely to have dental caries (odds ratio [OR] = 0.69, 0.69, and 0.97, respectively) and dental calculus (OR = 0.62, 0.73, and 0.86, respectively) than the 15-year-old group. Boys were significantly more likely than girls to have probe bleeding (OR = 1.16), but less likely to have dental caries (OR = 0.66).

Table 3.

Odds ratio (95%) for dental caries, probe bleeding, and dental calculus from binary logistic regression analysis (N = 3840).

Variable	Model 1: Dental caries		Model 2: Probe bleeding		Model 3: Dental calculus
	(DMFT > 0)		(Teeth number > 0)		(Teeth number > 0)
	OR	95%Cl	OR	95%Cl	OR	95%Cl
Age group (Reference group: 15-yr-olds)
12-yr-olds	0.69***	(0.56, 0.85)	1.15	(0.94, 1.40)	0.62***	(0.51, 0.77)
13-yr-olds	0.69***	(0.57, 0.85)	1.08	(0.89, 1.32)	0.73**	(0.59, 0.89)
14-yr-olds	0.97	(0.79, 1.18)	1.19	(0.98, 1.44)	0.86	(0.70, 1.05)
Sex (Reference group: Male)
Female	0.66***	(0.57, 0.77)	1.16*	(1.01, 1.34)	1.16	(1.00, 1.34)
Household registration (Reference group: Urban)
Rural	1.07	(0.91, 1.26)	0.96	(0.82, 1.12)	1.23*	(1.04, 1.45)
Administrative region (Reference group: Sanshui)
Chancheng	0.86	(0.70, 1.07)	1.37**	(1.12, 1.68)	1.94***	(1.57, 2.39)
Nanhai	0.9	(0.72, 1.13)	1.18	(0.95, 1.46)	0.84	(0.67, 1.06)
Shunde	1.35**	(1.10, 1.66)	0.89	(0.73, 1.09)	1.24*	(1.01, 1.52)
Only child (Reference group: Yes)
No	1.04	(0.87, 1.24)	1.03	(0.87, 1.22)	0.96	(0.81, 1.15)
Father education level (Reference group: University or above)
Middle school or below	1.14	(0.85, 1.53)	1.11	(0.84, 1.47)	1.08	(0.80, 1.44)
High school	1.05	(0.77, 1.41)	1.08	(0.81, 1.43)	0.97	(0.72, 1.31)
Mother education level (Reference group: University or above)
Middle school or below	1.44*	(1.04, 2.00)	1.14	(0.85, 1.55)	1.35	(0.98, 1.86)
High school	1.60**	(1.14, 2.24)	0.94	(0.69, 1.29)	1.21	(0.87, 1.69)
Brushing teeth (Reference group: ≥2 times/d)
Never	0.85	(0.41, 1.76)	1.18	(0.61, 2.30)	0.67	(0.33, 1.35)
<1 time/d	1.02	(0.44, 2.37)	2.59*	(1.10, 6.11)	2.04	(0.90, 4.63)
1 time/d	1.18*	(1.01, 1.37)	1.12	(0.97, 1.30)	1	(0.87, 1.17)
Using dental floss (Reference group: ≥1 time/d)
Never	0.47	(0.20, 1.08)	1.44	(0.62, 3.34)	3.14*	(1.12, 8.85)
Rarely	0.48	(0.20, 1.15)	1.01	(0.42, 2.44)	2.83	(0.97, 8.21)
1 time/d > f ≥ 1 time/wk	0.67	(0.21, 2.18)	2.47	(0.76, 8.01)	4.17*	(1.11, 15.63)
Smoking (Reference group: ≥1 time/d)
Never	0.74	(0.14, 3.84)	0.54	(0.09, 3.05)	0.7	(0.13, 3.94)
Rarely	0.59	(0.10, 3.40)	0.41	(0.07, 2.55)	0.7	(0.11, 4.26)
1 time/d > f ≥ 1 time/wk	3.44	(0.21, 56.76)	1.69	(0.10, 29.42)	0.69	(0.05, 9.56)
Sugar consumption habits by frequency (Reference group: High frequency)
Low	0.63**	(0.44, 0.90)	1.07	(0.76, 1.51)	1.24	(0.87, 1.78)
Relatively low	0.65**	(0.47, 0.90)	1.03	(0.75, 1.42)	1.03	(0.75, 1.44)
Middle	0.65**	(0.47, 0.88)	1.01	(0.74, 1.37)	1.1	(0.79, 1.51)
Relatively high	0.78	(0.56, 1.09)	0.98	(0.71, 1.37)	1.03	(0.73, 1.46)

(1) Binary logistic regression analysis.

(2) Dependent variable: Model 1—dental caries (0: “DMFT = 0”; 1: “DMFT > 0”); Model 2—probe bleeding (0: “teeth number with probe bleeding = 0”; 1: “teeth number with probe bleeding > 0”); Model 3—dental calculus (0: “teeth number with dental calculus = 0”; 1: “teeth number with dental calculus > 0”); (3) Independent variables: age group; sex; household registration (hukou); administrative region; only child; father education level; mother education level; brushing teeth; using dental floss; smoking; sugar consumption habits.

^*P ≤ .05.

^**P ≤ .01.

^***P ≤ .001.

Dental calculus prevalence (OR = 1.23) was significantly higher among adolescents living in rural than in urban areas. Dental caries prevalence (OR = 1.35) and dental calculus (OR = 1.24) were significantly higher among those living in Shunde than in Sanshui. Moreover, probe bleeding prevalence (OR = 1.37) and dental calculus (OR = 1.94) were significantly higher among adolescents living in Chancheng than in Sanshui. Rural household registration (OR = 1.23) was significantly more likely to lead to higher dental calculus prevalence than urban household registration did.

Adolescents whose mothers had middle-school or below and high-school degrees were more likely to have dental caries (OR = 1.44 and 1.60, respectively) than those whose mothers had a university degree or above.

Participants who brushed their teeth < 1 time/day and 1 time/day were more likely to have dental caries than those who did so ≥ 2 times/day, (OR = 1.02, and 1.18, respectively). Moreover, participants with a habit of brushing teeth ≥ 2 times/day were less likely to have probe bleeding than those in other groups. Participants who never or rarely used dental floss or used it > 1 time/day but ≤ 1 time/week were more likely to have dental calculus than those who used it ≥ 1 time/day, (OR = 3.14, 2.83, and 4.17, respectively).

Finally, adolescents with high-frequency sugar consumption were more likely to have dental caries than those with a low to relatively high frequency (OR = 0.63, 0.65, 0.65, and 0.78, respectively).

4. Discussion

The important strengths of this study compared to other studies in terms of public health contribution are the following 3: This study reveals the overall oral health level of adolescents in Foshan City, Guangdong Province, China, and to some extent, it represents the oral health status of adolescents in medium-sized cities of Southeast China. And it is the first oral health epidemiologic survey in Foshan City, revealing the latest data. This study shows that oral diseases/conditions were most common in tooth positions 46 and 36 (FDI 2-digit system), the first permanent molars of the mandible, suggesting the importance of protecting these teeth in adolescents. This paper suggests that the government, communities, schools, and families should pay attention to specific risk factors (older age, female sex, high frequency of sugar consumption, regional diet culture, mother educational background lower than university, and having no habit of using dental floss) and jointly promote oral health improvement among Chinese adolescents through mutual cooperation and integration.

This study revealed that the oral status of 12 to 15-year-old adolescents in Southeast China is better than the overall average level among Chinese adolescents. However, these students’ oral hygiene habits were undeveloped, with most young students not habitually using dental floss and many failing to brush their teeth twice daily. Thus, to a certain extent, our results suggest that many students have lost their self-discipline for brushing their teeth at least twice daily and that flossing is not popularized among adolescents.

Regarding dental health status, dental caries prevalence (37.6%) was lower than the national average rate (41.9%) in China.^[9,11] The DMFT score (0.86) was also lower than the national average score (1.04).^[9,11] The status of dental caries was better than that in some provinces or cities of China,^[12–14] possibly because families and schools in this region attach importance to adolescent oral health education. The top 3 tooth positions prone to caries found in this study are similar to those reported in the national findings^[9] or findings from other Chinese provinces.^[12,13]

The prevalence of probe bleeding and dental calculus in the surveyed adolescents were lower than the national average rates (46.3% and 39.6%, vs 61.0% and 67.3%,^[10] respectively). The number of teeth with probe bleeding and calculus were lower than the national average numbers (2.09 and 1.85 per person, vs 4.94 and 4.90 per person,^[10] respectively). Moreover, fewer of the 15-year-olds in this study had periodontal pockets and loss of tooth attachment (0.3% and 0.1%, respectively) than the corresponding national population (6.5% and 5.0%).^[10] Thus, the periodontal health status of adolescents in Southeast China is better than the national average level in China. However, it is worse than that of adolescents in other countries, such as Japan,^[17] Jordan,^[18] and Latin American countries,^[19] but better than that of adolescents in Puerto Rico.^[20] Therefore, the periodontal health of adolescents in Southeast China is good but improvable. Further, the most common tooth positions for probe bleeding and calculus in this study are consistent with the general distribution trend in China (especially regarding the status of the lower jaw).^[10] This is also consistent with clinical findings indicating that the periodontal status of mandibular teeth is generally worse than that of teeth in the same position in the upper jaw.^[21]

Adolescents aged 12 to 14 years were less likely to have dental caries and dental calculus than those aged 15 years, consistent with the results of similar studies in China^[10,22] and Tanzania.^[23]

Female sex was an important risk factor for dental caries, which is consistent with the findings of other comparable studies in China.^[14,22,24] In contrast, probe bleeding was relatively less prevalent among female than male adolescents, in agreement with earlier findings from the national oral survey in China.^[10] As girls prefer to eat sweets more commonly than boys, their teeth are exposed to a cariogenic oral environment for a longer time, which may explain the higher prevalence of dental caries among girls in our study.^[14] Nevertheless, girls generally pay more attention to oral hygiene and health care,^[23] possibly explaining why the prevalence of probe bleeding was lower among girls, consistent with previous research.^[12,13]

Adolescents in rural households were significantly more likely to have dental calculus than those in urban households. This finding is somewhat different from that of the national survey, which indicated no difference in dental calculus between urban and rural groups.^[10] Although the development gap in the economy, education, and health care has gradually narrowed between urban and rural households; our findings support the differences that still exist in adolescents’ oral health in Southeast China.

We also found slight differences in the oral health status among people in the inner areas of Foshan City. Thus, even in the same city, regional characteristics of different areas seem to have a different impact on the oral status of adolescents, and this key factor should not be ignored in oral health management.

Further, consistent with 1 study in Mexico,^[25] our study showed that adolescents whose mothers have a low education level are more likely to have dental caries. Regardless of the child nutritional status, psychological development, physical well-being, or healthcare decisions, an empowered, educated mother is generally considered to play a definitive role.^[26] Moreover, better-educated parents are more aware of their children health education and willing to invest more in their oral health education.^[27]

Less frequent brushing of teeth was a significant risk factor for dental caries and probe bleeding. Consistent with this research, a systematic review and meta-analysis including 33 eligible studies provided sufficient evidence that infrequent brushers demonstrate higher incidence of carious lesions than frequent brushers.^[28] Moreover, a study from Sichuan (a province in Southwest China) including 4525 12-year-old Chinese adolescents showed that adolescents who brushed their teeth at least twice daily had a lower rate of probe bleeding.^[29]

We found that using dental floss less frequently or not at all is a significant risk factor for dental calculus. Evidence from Sichuan also showed that adolescents using dental floss have a lower rate of calculus detection,^[29] and a review of 12 studies also demonstrated that flossing is effective in preventing gum disease.^[30]

Consistent with previous findings,^[31] a high sugar consumption frequency was an important risk factor for dental caries in our study. Therefore, health education and diet intervention should be strengthened at home and school to reduce excessive sugar consumption, in agreement with the results of a study in Japan calling for reduced sugar intake.^[32]

Some factors, including “only child in family,” “father educational level,” and “smoking,” were not significant in the logistic regression models; “only child in family” and “father educational level” were significant in the non-parametric test. This may reflect that the latter 2 factors have no direct influence on the oral health of adolescents. In addition, only 11 of the 3840 adolescents in this study stated that they were frequent smokers; thus, it is difficult to determine the influence of smoking on the oral health of the adolescent population.

The following aspects of public oral health should be improved in the adolescent population.

First, based on our findings, as dental diseases accumulate with age, regular oral examinations should be a standard practice throughout one life, including adolescents, whose permanent teeth have recently erupted. This could help identify oral health problems early, enabling timeous treatment.

Second, as parents’ sociodemographic characteristics could affect adolescents’ oral health, the concept that “parents and other family caregivers are responsible for their children oral health” should be set up, and the parents’ sense of responsibility for their children oral health should be strengthened at a fitting time.

Third, brushing teeth twice daily and flossing should be promoted among adolescents. Although such practices have become a social norm, it is hard to ignore their low adoption among adolescents as shown in this and previous studies. Thus, the adolescents’ self-efficacy on keeping these habits should be strengthened through various ways, including encouragement from both parents and teachers and government intervention. Moreover, the methods and skills of flossing should be popularized.

Fourth, sugar consumption among adolescents should be controlled, including through programs to reduce sugar consumption at schools. Specifically, school supermarkets and canteens should restrict the sale of high-sugar drinks, snacks, and other foods. The government should regularly organize dentists’ visits to schools to educate adolescents about the dangers of a high-sugar diet, and offer interactive games to help adolescents distinguish among high-sugar, low-sugar, and sugar-free foods or drinks, as well as strengthen their self-efficacy for “sugar control.” Parents should create sugar-free- or low-sugar-supporting family environments for young children. Parents could be encouraged to supervise their children brushing of teeth after eating any meal or snack, which might improve their children oral hygiene, simultaneously accompanied by an effect of minimizing the urge for sweets. In addition, the public health department should work with multiple departments to improve the “high sugar” business environment and control the amount of sugar in relevant commodities and catering foods.

Finally, regional characteristics, such as urbanization level or administrative division, seem to affect adolescent oral health. Therefore, when formulating policies, the government may have to consider local characteristics, which involve diet culture, business environment, etc.

5. Limitation

The sample used in this research avoided the bias accompanying convenience samples selected from dental hospitals; however, this study still suffered some limitations. First, being a cross-sectional study, it was difficult to establish a causal relationship between health status and associated factors. Second, due to using a self-filled questionnaire, potential information, recall, and social desirability bias might have influenced the final results. Third, this study was based on a sample selected from Southeast China; thus, when comparing this study with other studies, differences in national, geographical, cultural, and economic conditions need to be considered. Fourth, due to resource constraints such as manpower and funds, Sanshui was chosen to represent the less developed region, and Gaoming district was excluded in the sampling process, which may have produced some bias in the results. Fifth, the oral hygiene habits and eating habits evaluated by survey presumably suffer from reporting bias (underreporting of sweet consumption or don’t remember how often sweets were eaten). Sixth, some of the reason for reporting bias might be that boys underreported sweet consumption or didn’t remember every. Despite these limitations, our findings provide a large picture of the oral health status of adolescents in medium-sized cities of Southeast China, and offer insight on factors closely associated with the oral health of this population, which may help in adopting a prospective study design in further research.

6. Conclusion

The overall oral health level of adolescents in Foshan City, Guangdong Province, China, can, to some extent, represent the oral health status of adolescents in medium-sized cities of Southeast China. The oral health of 12 to 15-year-old adolescents in Southeast China was better than the national average level, indicated by the lower prevalence of oral diseases/conditions, such as dental caries, probe bleeding, and dental calculus, and fewer teeth with these problems. The above-mentioned oral diseases/conditions were most common in tooth positions 46 and 36 (FDI 2-digit system), the first permanent molars of the mandible, suggesting the importance of protecting these teeth in adolescents. Adolescents in the community should be encouraged to undergo fissure sealing treatment to prevent oral diseases of permanent molars. Older age, female sex, regional diet culture, mother educational background lower than university, less frequent brushing of teeth, having no habit of using dental floss, and high frequency of sugar consumption were factors that significantly increased oral diseases/problems risks. The government, communities, schools, and families should pay attention to the above factors and jointly promote oral health improvement among Chinese adolescents through mutual cooperation and integration.

Author contributions

Conceptualization: Shuwen Su, Jianming Zhang, Xia Li.

Data curation: Ruibing Deng, Weiping Wang, Tianqiang Cui, Xia Li.

Formal analysis: Tianqiang Cui, Xia Li.

Funding acquisition: Shuwen Su.

Investigation: Jianming Zhang, Ruibing Deng, Weiping Wang, Tianqiang Cui, Yuwu Su, Xia Li.

Methodology: Shuwen Su, Xia Li.

Project administration: Ruibing Deng, Yuwu Su.

Resources: Jianming Zhang, Ruibing Deng, Weiping Wang, Tianqiang Cui, Yuwu Su, Xia Li.

Software: Shuwen Su.

Supervision: Jianming Zhang, Ruibing Deng, Xia Li.

Writing – original draft: Shuwen Su.

Writing – review & editing: Shuwen Su, Jianming Zhang, Xia Li.