Oral hygiene status, oral health-related behaviors, sleep, body mass index and dental caries prevalence of a sample aged five from Southwest China: a cross-sectional survey

Abstract

Background

This study aimed to revisit the early childhood caries (ECC) prevalence among children aged 5 in Xiangyun to assess the impact of caries intervention implemented in the past several years and explore the association between sleep status, body mass index, and ECC among young children in Xiangyun for the first time.

Methods

A total of 954 children aged five in Xiangyun were selected between September and November 2023. This cross-sectional survey comprised a dental examination and an oral health-related questionnaire. The caries presence was recorded according to the dental examination standard of the WHO 2013 criteria. The oral hygiene status was evaluated using the Simplified Debris Index (DI-S). Parents completed questionnaires that included demographic variables, family socioeconomic status, oral health-related habits, children’s sleep status, children’s birth weight, current height and weight. The statistical analysis was conducted using SPSS software. The chi-square test and logistic regression analysis identified significant variables associated with the prevalence of ECC. Statistical significance was set at a P-value of 0.05.

Results

Data from 45 incomplete questionnaires were removed from the analysis due to missing information. The ECC prevalence of 909 children consisting of 460 males and 449 females was 75.03%, with a mean dmft of 4.7 ± 4.6. Neither the sleep status nor the body mass index showed an association with the caries prevalence (P > 0.05). Logistic regression analysis showed that the most significantly associated factors were: the family income less than 6,000 Yuan, consuming desserts/cookies at least once a day, eating snacks without toothbrushing before bed, brushing teeth independently, having poor oral hygiene status and the use of fluoride toothpaste.

Conclusions

The prevalence of caries among 5-year-old children in Xiangyun remains higher than the national average in China. This higher prevalence is primarily associated with family income, several oral-health-related habits, and poor oral hygiene status, but not with sleep status or body mass index. In response, the local government should prioritize enhancing access to preventive oral care for children from impoverished families. Additionally, efforts should be made to encourage parents to supervise their children’s toothbrushing, improve their children’s oral hygiene, and correct harmful habits, such as eating snacks without brushing their teeth before bed in the future.

Background

Early childhood caries (ECC) in children under age six, a preventable condition, continues to be a significant problem in both developed and developing countries, affecting nearly half of the global preschoolers [1]. A recent study showed that a greater proportion of children with ECC developed from 2017 to 2018 versus 2013 to 2014 in the United States [2]. In China, the Fourth National Oral Health Epidemiological Survey Program reported a rise in the overall caries prevalence among 5-year-old children from 66% in the third survey to 71.9% [3].

The etiology of ECC is multifactorial. The interaction of environmental, behavioral, biological, and genetic factors, such as oral microbiome, feeding type, dietary and oral hygiene habits, tooth structure, salivary composition, family income, and parental education level, plays a pivotal role in ECC initiation and progression [4]. Dietary habits impact oral health and are, in turn, influenced by oral health status. Children with severe decay can also have altered eating habits and preferences [5], subsequently influencing nutritional health. Thus, dental caries status can be linked to both underweight and overweight conditions [6]. On the contrary, recent systematic reviews provided little evidence to support a consensus on the relationship between body mass index (BMI) and dental caries in children [7, 8], calling for more research to shed light on this complex relationship.

Furthermore, the sleep status of children can influence their oral health. Irregularities in sleep status could contribute to reduced salivary flow and impaired immune function, hence increasing the risk of ECC development [9]. On the other hand, ECC might lead to increased pain episodes, resulting in frequent night-time waking episodes or sleep disturbances. A 2022 systematic review by Sardana et al. concluded that irregular or late bedtime and insufficient sleep could be independent risk factors for ECC, and the risk of ECC might be related inversely in a dose-response manner to the number of sleep hours [10]. Contrarily, other research did not confirm the association between the sleep and ECC [11], indicating that more related studies are in need.

In 2020, we first investigated the ECC prevalence among children aged 3–5 from Xiangyun of Yunnan, a remote region located in Southwest China, and revealed a higher ECC prevalence than the national average [12]. Since 2019, the local government has implemented fluoride varnish for preschool children twice a year in the kindergartens as part of the National Oral Health Comprehensive Intervention Program in China. In light of this development, our team aims to revisit the ECC prevalence among children aged 5 in Xiangyun to assess the impact of caries intervention. Moreover, our data analysis in 2020 unearthed a surprising finding- no association between different dietary and oral hygiene habits and caries prevalence. This prompts us to delve deeper into the factors associated with ECC based on more information about oral hygiene status and oral health-related behaviors. Lastly, we aimed to explore the association between sleep status, BMI, and ECC among young children in Xiangyun for the first time.

Methods

Study design and sample selection

This cross-sectional study was approved by the Ethics Committee of the People’s Hospital of Xiangyun (No.KY-PJ-2022-001). Written informed consents were obtained from all the children’s legal guardians/parents before the enrolment.

The survey was carried out between September and November 2023 in Xiangyun County, China. Before the study initiated, the sample size was calculated using the Power Analysis & Sample Size (PASS) software 16.0, based on a 95% confidence interval, 5% standard error, 71.9% prevalence (the caries prevalence of Chinese children aged five years nationwide in 2015), and a 20% non-response rate. The minimum sample size needed was 410.

Children aged five from kindergartens located in four geographical regions (eastern, southern, western, and northern) who could attend the class on the survey and cooperate with the examiner were enrolled using a stratified cluster sampling method [12]. Children’s parents/guardians should be able to understand the study and be willing to sign the informed consent. Once the legal guardians failed to understand this survey or systemic diseases or mental disorders in the children were present, children would be excluded. In total, 954 children participated in the dental examination.

Date collection

Clinical examination

Dentists from the Department of Stomatology at the People’s Hospital of Xiangyun, with working experience of more than three years, examined all the included children using a disposable mouth mirror and a probe under artificial light in the classrooms according to the WHO recommendations for oral epidemiological surveys [13]. Dental caries was determined as decayed-missing-filled teeth (dmft) > 0.

The oral hygiene status was evaluated using the debris component of the Simplified Oral Hygiene Index, the Simplified Debris Index (DI-S). Due to the young age of this sample, four facial and two lingual surfaces of six index teeth (51, 55, 65, 71, 75, and 85) were examined to assess the extent of the debris [14]. Each tooth was scored from zero to three, and the mean scores of the six teeth were recorded to determine the child’s DI-S. These scores were categorized as very good (0-0.2), good (0.3–0.6), fair (0.7–1.8) and poor (1.9-3.0) [14]. No radiographs were taken for this study.

Before the survey, we tested the intra-examiner and inter-examiner using the same method in our previous study [12]. The mean Kappa values of both the intra-examiner and inter-examiner for dental caries and oral hygiene status were over 0.80, representing a satisfactory level of consistency.

Questionnaire survey

The Chinese questionnaire used for this study was modified based on the questionnaire used in our previous publication [12]. After receiving unified training prior to the field investigation in each kindergarten, teachers distributed and collected the questionnaires. Parents or guardians completed the questionnaire with the consent form the day before the clinical examination of their children. The questionnaire contained the following information:

1. Sociodemographic background: sex, the number of children, primary caregiver, parental education level, family income and residence. Regarding family income, all impoverished individuals in Xiangyun County were successfully lifted out of poverty in 2019, with an average per capita disposable income of 37,689 Yuan [15, 16]. This amount translates to an average monthly household income of approximately 6,000 Yuan, based on a typical scenario with two full-time working parents.

2. Oral-health-related dietary and hygiene habits: frequency of consuming desserts/cookies, frequency of consuming sweet drinks, frequency of consuming candies/chocolates, eating snacks (cookies, desserts, candies, chocolates, and fried chips, etc.) without toothbrushing before bed, age at which the child began toothbrushing, toothbrushing frequency, toothbrushing duration, parental supervision for toothbrushing, the use of fluoride toothpaste, the use of dental floss, the application of pit and fissure sealant, the application of fluoride varnish.

3. Parental caries experience.

4. Sleep status: bedtime, sleep duration and afternoon napping.

5. Birthweight and current weight and height: Children with a birth weight below 2,500 g are classified as having low birth weight. In contrast, those born weighing 4,000 g or more are defined as having high birth weight [17]. The Body Mass Index (BMI) is a widely used measure in healthcare that helps determine whether a person’s weight is healthy in relation to height. It is calculated by dividing a person’s weight in kilograms by the square of their height in meters. The classification of BMI in this study referred to the updated growth standard for children under 7 years of age, implemented by China’s National Health Commission in 2023 [18, 19]. According to this standard, the nutritional statuses of children are categorized into six groups based on BMI scores, using age and gender-specific criteria:

• Normal weight: −2 SD≤ • <+1 SD.

• Overweight: +1SD≤ • <+2SD.

• Obesity: +2 SD≤ • <+3 SD.

• Severe obesity: ≥+3SD.

• Wasting: −3 SD≤ • <−2SD.

• Severe wasting: <−3SD.

Data analysis

Statistical analysis was performed using SPSS Statistics 25.0 (IBM, Chicago, IL, USA). The frequencies of the variables were calculated using descriptive analysis. Univariate associations between the categorical variables and the ECC prevalence were evaluated using the chi-square test [20]. In the present study, variables with a P-value < 0.20 proceeded to undergo logistic regression analysis [20]. A P-value of less than 0.05 indicated statistical significance.

Results

All the parents of the included children completed the questionnaire. No child was excluded from our study for health reasons. Due to missing information, data from 45 incomplete questionnaires were removed from the analysis. Finally, there were 909 children aged five consisting of 460 males and 449 females included in the analysis.

This study revealed a significant caries prevalence of 75.03% in the sample, with a mean dmft of 4.7 ± 4.6. As shown in Table 1, males had a slightly higher caries prevalence than females without significant differences (P = 0.368). Similarly, single children showed no significant difference in caries prevalence compared with non-single children (P = 0.189). Children whose parents held an undergraduate degree or higher exhibited a relatively lower caries prevalence of 71.50% compared to other children, but the difference was not statistically significant (P = 0.085). The caries prevalence of children from families with a monthly income of 12,000 Yuan and above was significantly lower (P = 0.011).

Table 1.

Prevalence of ECC and socioeconomic factors (N=909)

Variables	N	%	Groups		P-value
			Caries-Free(N/%)	ECC (N/%)
Sex
Male	460	50.61%	109 (23.70%)	351 (76.30%)	0.368
Female	449	49.39%	118 (26.28%)	331 (73.71%)
Single child
Yes	304	33.44%	84 (27.63%)	220 (72.37%)	0.189
No	605	66.56%	143 (23.64%)	462 (76.36%)
Primary caregiver
Parents	743	81.74%	190 (25.57%)	553 (74.43%)	0.377
others	166	18.26%	37 (22.29%)	129 (77.71%)
Parental education level
High school or below	315	34.65%	72 (22.86%)	243 (77.14%)
College	194	21.34%	41 (21.13%)	153 (78.87%)	0.085
Undergraduate or above	400	44.00%	114 (28.50%)	286 (71.50%)
Family income (Yuan, per month)
<6,000 Yuan	372	40.92%	74 (19.89%)	298 (80.11%)	0.011
≧6,000 and <12,000	355	39.05%	98 (27.61%)	257 (72.39%)
≧12,000	182	20.02%	55 (30.22%)	127 (69.78%)
Residency
Urban	438	48.18%	118 (26.94%)	320 (73.06%)	0.186
Rural	471	51.82%	109 (23.14%)	362 (76.86%)
Total	909	100%	227 (24.97%)	682 (75.03%)

Table 2 showed that children with very good/good mouth cleanliness showed significantly lower caries prevalence than those having fair and poor oral hygiene (55.23% vs. 82.09%, P < 0.0001). Besides, there was an association between children’s caries prevalence and the frequency of consuming desserts/cookies, sweet drinks, and candies/chocolates (P < 0.05). Among the sample, 654 (71.95%) children experienced eating snacks without toothbrushing before bed, showing a significant higher caries prevalence than others (P = 0.002).

Table 2.

Prevalence of ECC and oral hygiene status, oral hygiene behaviors, dietary habit and parental caries experience (N=909)

Variables	N	%	Groups		P-value
			Caries-Free (N/%)	ECC (N/%)
Oral hygiene status
Very good/good	239	26.29%	107 (44.77%)	132 (55.23%)	<0.0001
Fair/poor	670	73.71%	120 (17.91%)	550 (82.09%)
Frequency of consuming desserts/cookies
At least once a day	338	37.18%	62 (18.34%)	276 (81.66%)	<0.0001
Occasionally or never	571	62.82%	165 (28.90%)	406 (71.10%)
Frequency of consuming sweet drinks
At least once a day	113	12.43%	16 (14.16%)	97 (85.84%)	0.005
Occasionally or never	796	87.57%	211 (26.51%)	585 (73.49%)
Frequency of consuming candies/chocolates
At least once a day	226	24.86%	42 (18.58%)	184 (81.42%)	0.010
Occasionally or never	683	75.14%	185 (27.09%)	498 (72.91%)
Eating snacks without toothbrushing before bed
Yes	654	71.95%	145 (22.17%)	509 (77.83%)	0.002
No	255	28.05%	82 (32.16%)	173 (67.84%)
Begin toothrushing
1-year-old and below	87	9.57%	28 (32.18%)	59 (67.82%)	0.080
2-year-old	333	36.63%	90 (27.03%)	243 (72.97%)
3-year-old and above	489	53.80%	109 (22.29%)	380 (77.71%)
Toothbrushing frequency
Twice per day or above	528	58.09%	141 (26.70%)	387 (73.30%)	0.113
Once a day	341	37.51%	73 (21.41%)	268 (78.59%)
Occasionally or never	40	4.40%	13 (32.50%)	27 (67.50%)
Toothbrushing duration
Less than 1min	145	15.95%	35 (24.14%)	110 (75.86%)
1-2min	494	54.35%	123 (24.90%)	371 (75.10%)	0.949
2min and longer	270	29.70%	69 (25.56%)	201 (74.44%)
Parental supervision for toothbrushing
Every time	159	17.49%	50 (31.45%)	109 (68.55%)	0.026
Occasionally	653	71.84%	161 (24.66%)	492 (75.34%)
Never	97	10.67%	16 (16.49%)	81 (83.51%)
Fluoride toothpaste
Yes	504	55.45%	115 (22.82%)	389 (77.18%)	0.094
No	405	44.55%	112 (27.65%)	293 (72.35%)
Dental floss
Yes	169	18.59%	46 (27.22%)	123 (72.78%)	0.455
No	740	81.41%	181(24.46%)	559 (75.54%)
Pit and fissure sealant
Yes	143	15.73%	44 (30.77%)	99 (69.23%)	0.081
No	766	84.27%	183 (23.89%)	583 (76.11%)
Fluoride varnish
Yes	712	78.33%	183 (25.70%)	529 (74.30%)	0.334
No	197	21.67%	44 (22.34%)	153 (77.66%)
Parental caries experience
Yes	351	38.61%	79 (22.51%)	272 (77.49%)
No	558	61.39%	148 (26.52%)	410 (73.48%)	0.173

Only 9.6% of children started toothbrushing at the age of 1 or younger. Over half of the children had twice-daily toothbrushing, but this did not result in a lower caries prevalence. While 55.45% of the children used fluoride toothpaste, only 18.59% used dental floss. The data analysis uncovered that 17.49% of children brushed their teeth under parental supervision every time and showed significantly lower caries prevalence (68.55%, P = 0.026). There were 712 (78.33%) children who received fluoride varnish, showing a similar caries prevalence to those who did not (74.30% vs. 77.66%). Around 40% of children’s parents had a history of caries. No association existed between the parental caries experience and the caries prevalence in children (P = 0.173).

Table 3 shows the sleep statuses and BMI index of the children. Nearly half of the sample went to bed before 9 am, and nearly three-third of the children had a sleep duration of less than ten hours. The majority of the children (94.39%) had a normal birth weight, and 73.16% showed normal BIM index at the examination time. Neither the sleep status nor the BMI showed an association with the caries prevalence (P > 0.05).

Table 3.

Prevalence of ECC and BMI and sleep duration (N = 909)

Variables	N	%	Groups		P-value
			Caries-Free (N/%)	ECC (N/%)
Bedtime
Before 9 pm	424	46.64%	98 (23.11%)	326 (76.89%)	0.473
9–10 pm	176	19.36%	46 (26.14%)	130 (73.86%)
After 10 pm	309	33.99%	83 (26.86%)	226 (73.14%)
Sleep duration
< 10 h	677	74.48%	167 (24.67%)	510 (75.33%)	0.717
≥ 10 h	232	25.52%	60 (25.86%)	172 (74.14%)
Afternoon napping
Yes	859	94.50%	218 (25.38%)	641 (74.62%)	0.241
No	50	5.50%	9 (18.00%)	41 (82.00%)
Level of birth weight
Normal	858	94.39%	213 (24.83%)	645 (75.17%)	0.079
Low weight	27	2.97%	4 (14.81%)	23 (85.19%)
High weight	24	2.64%	10 (41.67%)	14 (58.33%)
Level of BMI
Normal	665	73.16%	171 (25.71%)	494 (74.29%)	0.462
Wasting/severe wasting	64	7.04%	12 (18.75%)	52 (81.25%)
Overweight/obesity/severe obesity	180	19.80%	44 (24.44%)	136 (75.56%)

The logistic regression analysis (Table 4) indicated that the caries prevalence was significantly higher in children consuming desserts/cookies at least once a day (P = 0.001, POR 1.81; 95% CI: 1.28–2.57), those eating snacks without toothbrushing before bed (P = 0.003; POR 1.68; 95% CI: 1.19–2.37), those brushing teeth independently (P = 0.012, POR 2.38; 95% CI: 1.21–4.68), those with poor oral hygiene status (P < 0.0001, POR 3.69; 95% CI: 2.65–5.15), those whose family income lower than 6,000 Yuan (P = 0.025, POR 1.65; 95% CI: 1.06–2.55) and the use of fluoride toothpaste (P = 0.025, POR 1.45; 95% CI: 1.05–2.01).

Table 4.

Logistic regression analysis of factors associated with the ECC prevalence

Variables		B	SE	Wald χ2	P	POR
Family income (Yuan, per month)	≧ 12,000 (reference)
	< 6,000	0.50	0.22	4.99	0.025	1.65 (1.06–2.55)
Frequency of consuming desserts/cookies	Occasionally or never (reference)
	At least once a day	0.59	0.18	11.15	0.001	1.81 (1.28–2.57)
Eating snacks without toothbrushing before bed	No (reference)
	Yes	0.52	0.18	8.67	0.003	1.68 (1.19–2.37)
Parental supervision for brushing teeth	Every time (reference)
	Never	0.87	0.34	6.37	0.012	2.38 (1.21–4.68)
Fluoride toothpaste	No (reference)
	Yes	0.37	0.17	5.04	0.025	1.45 (1.05–2.01)
Oral hygiene status	Very good/good (reference)
	Fair/poor	1.31	0.17	59.38	< 0.0001	3.69 (2.65–5.15)

B regression coefficient, SE standard error, Wald χ2: a chi-square value, P: significant level, POR prevalence odds ratios

Discussion

Compared with the epidemiological survey in 2020 [12], the caries prevalence of 5-year-old children in Xiangyun slightly decreased from 80.00 to 75.03%, and the average dmft index score also decreased from 5.7 to 4.7, which may partly be attributed to the implementation of caries prevention program in the past several years. Nevertheless, the caries prevalence is still higher than the national average level, implying that the local government still needs to make efforts to prevent ECC in Xiangyun, China.

Socioeconomic status is an important risk indicator for ECC [4]. The data in this study showed a link existed between lower family income and higher ECC prevalence. Therefore, strategies to prevent ECC should focus on improving access to preventive oral care for children living in poverty. Besides, a lower parental education level resulted in higher caries prevalence in previous studies [21, 22]. The present study found no significant association between parental education and ECC prevalence, which may be because parents with higher education levels would have more opportunities to access health information, but failed to contribute to caries prevention for children in action [12].

ECC, like other forms of caries, is considered to be a biofilm-mediated, sugar-driven, multifactorial, dynamic disease [23]. The World Health Organization (WHO) recommends a reduced intake of free sugars less than 10% of the total energy intake and preferably below 5% of the total energy intake in both adults and children [24]. Meanwhile, the International Association of Pediatric Dentistry (IAPD) Bangkok Declaration recommends limiting sugar intake in foods and drinks and avoiding free sugars for children under two years of age to reduce the prevalence and burden of ECC worldwide [23]. In a prospective study, Boustedt et al. found a relationship between consumption of free sugars early in life and caries prevalence at five years [25]. In this study, we found that similar to prior studies, children taking more sweet food and drinks tended to have a significantly higher caries prevalence. Moreover, both the chi-square test and logistic regression analysis showed a significant association between the ECC prevalence and desserts/cookies consumption. This may be because processed food, especially many forms of cookies, is very sticky and difficult for oral hygiene. If left in contact with the enamel, the sticky food serves as a carbohydrate source for cariogenic bacteria, which in turn process the sugars into lactic acid, leading to the breakdown of the teeth and cavities [26].

It is well acknowledged that daily tooth brushing with fluoride toothpaste is effective in preventing ECC and maintaining oral health. A systematic review concluded that individuals who reported brushing their teeth infrequently had a higher incidence and increment of carious lesions than those brushing more frequently, and this effect of brushing was more pronounced in primary than in permanent dentition [27]. The present study did not find statistically significant associations between ECC prevalence, age of start tooth brushing, and tooth brushing frequency. As we speculated previously, one reason may be that half of the sample started brushing their teeth at the age of 3 or above when caries had already existed. Secondly, the brushing effect, in other words, the oral hygiene status or cleanliness, might be more important when the effect of tooth brushing in preventing caries is evaluated. To facilitate the examination of young children, we used the DI-S to represent oral hygiene status. We found that oral hygiene, reflecting the effectiveness of tooth brushing, was strongly associated with ECC prevalence. This implies that children should not only start brushing their teeth regularly at an early age every day but also brush their teeth as cleanly as possible.

In young children, unsupervised toothbrushing is not effective due to the motor of development [28]. Chua et al. found that children entering elementary school (≥ six years old) brushed more effectively than preschool children [29]. Ozgul reported that children under the age of nine usually lack the developmental skills needed to brush their teeth [30]. In the present study, only 17.5% of parents helped children brush their teeth every time, which may contribute to the fact that 73.7% of children had fair/poor oral hygiene status. This finding suggests that parents should pay attention to supervised toothbrushing for their children.

Fluorides play a central role in the prevention of dental caries [31]. Due to the vast territory, it is inappropriate to apply fluoridated drinking water in China, as has been done in other countries [32]. Fluoride toothpaste and varnish are the two main products used by young Chinese children. The results indicate an increase in the use of fluoride toothpaste and the application of fluoride varnish among children compared to three years ago [12], suggesting that local caries prevention programs have been somewhat successful. Unexpectedly, in this sample, children using fluoride toothpaste had a higher prevalence of ECC, which was statistically significant according to logistic analysis. This unexpected finding may be due to two factors. First, more than half of the children began brushing their teeth at age three or older, by which time dental caries may have already developed. Second, parents may have only started using fluoride toothpaste after noticing their child’s decayed teeth. However, we did not investigate whether parents initiated fluoride toothpaste use specifically in response to detecting decayed teeth, a question that warrants further research.

A caregiver having current decay or a recent history of decay is included in several common caries risk assessment methods [33]. Birungi et al. demonstrated that the caregiver’s caries experience is positively associated with the ECC of their offspring [34]. In this study, parental caries experience was not significantly associated with ECC prevalence, though children whose parents had no caries experience had a relatively lower caries prevalence. We supposed that other factors associated with the high ECC prevalence might overshadow the influence of the parental caries experience in this sample.

The National Sleep Foundation of the United States in 2015 recommended that for healthy individuals with normal sleep, the appropriate sleep duration for preschoolers is between 10 and 13 h [35]. Thus, we divided the sample into two groups according to the sleep duration of 10 h and explored the association between the sleep duration and caries prevalence. Generally, saliva, with the capacity to flush microorganisms and substrates and maintain oral cleanliness, plays an essential role in protecting teeth from caries [36]. A decrease in the amount or quality of saliva can significantly increase the caries risk [36]. Saliva displays a circadian rhythmicity [37], and mistimed and disrupted sleep can lead to disruption of the circadian rhythms [9], providing a possible link between insufficient sleep and increased caries risk [38]. Unlike an association between late bedtime and short sleep duration and increased ECC risk [9, 38], which was well-established in previous studies, neither sleep duration nor bedtime showed any relationship with ECC prevalence in the present study. This controversy may be attributed to the bad habit of eating snacks without brushing their teeth before bed, which existed in 71.9% of the children. During the night, the flow and amount of saliva decrease; if children go to bed without brushing, the food debris left on the tooth surface is favorable for cariogenic bacteria to produce acid and destroy the tooth structure. Therefore, the long sleep duration will not show benefits for caries prevention if children have bad oral health-related behaviors.

Low birth weight (LBW) may be associated with enamel defects, which favor dental plaque formation and make teeth more vulnerable to caries [39]. Additionally, children with LBW may exhibit a weakened immune system, potentially leading to earlier colonization by cariogenic bacteria and thereby increasing the susceptibility to caries [40]. In fact, systematic reviews in the past two decades did not suggest a significant association between LBW and dental caries in children for primary teeth [41, 42], which was also demonstrated in this study, despite children with LBW showing a higher ECC prevalence of 85.2%. In a way, the unequal sample size between the LBW and normal weight groups may influence the statistical analysis, resulting in no significant differences. Further well-designed cohort studies are still necessary to clarify the relationship between LBW and ECC.

A child’s nutritional status can be assessed by calculating their body mass index (BMI) for age, which takes into account their height and weight [6]. The data showed that nearly three-fourths of children were within the normal nutritional status. Childhood obesity and dental caries share a common risk factor-a high-sugar diet [8]. However, the results from previous studies on the association between obesity and ECC were inconclusive. Some studies suggested a positive association [43, 44], a few indicated a negative association [45, 46], and some found no relationship at all [47]. In our study, we found that children with obesity had a similar ECC prevalence to children with a normal BMI, suggesting no direct association between obesity and ECC. These findings highlight the need for further research to fully understand the relationship between the two health issues.

This study had some limitations. First, the dental examinations undertaken in the classroom are not as precise as the examinations in a dental office where various instruments and equipment are available, which may have compromised the ability to detect early lesions accurately. Second, the oral health-related behaviors of parents were not investigated, which limits the exploration of the parental impact on children’s behaviors and ECC prevalence. Third, due to the cross-sectional study design, it is improper to determine causal relationships between associated factors and ECC prevalence.

Despite all the limitations, the present study provides the updated ECC prevalence and associated factors among five-year-old children in Xiangyun, China, which could be used to develop oral health prevention and promotion strategies for this age group. According to the results, the local government should focus on improving oral health care for children from poor family and motivate parents to supervise children’s tooth brushing, improve children’s oral hygiene status, and correct bad habits such as eating snacks without brushing their teeth before bed in the future.

Abbreviations

ECC

Early childhood caries

BMI

Body mass index

PASS

Power Analysis and Sample Size

DI-S

Simplified Debris Index

WHO

World Health Organization

IAPD

International Association of Pediatric Dentistry

Authors’ contributions

XQ Xu and HM Zhang collected the data and wrote the manuscript. MS Liu revised the manuscript. GY Lai analyzed the data and revised the manuscript. All authors approved the final version of the manuscript prior to submission.

Funding

Not applicable.

Data availability

The raw data that support the findings of this study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

All procedures in this study were performed in accordance with the ethical standards of the People’s Hospital of Xiangyun (No.KY-PJ-2022-001) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Written informed consent was obtained from parents before the survey.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.