This study has a large sample size, covering all elementary schools in Shijingshan District of Beijing. Though there were some children absent from the study, the studied sample can approximate the eruption and caries status of FPMs of the entire district. In addition, monitoring data from the past few years (2017, 2019 and 2021), the prevalence of dental caries in Shijingshan District has been similar to the average level in the city of Beijing[10–12]. Therefore, results based on children in the district may provide a glimpse into the conditions of the city of Beijing.
The time of eruption for FPMs of children is approximately six years of age[16] and erupted teeth are more susceptible to caries during the first one to three years after the eruption[17]. This study found that the prevalence of dental caries of FPMs was 5.5% among 6-7-year-old children. Therefore, the effective intervention should be applied closer to the very onset of tooth emergence.
This study showed that sex and father’s educational level corelated with the caries experience of the studied children. A higher prevalence of caries was found in girls and children from families with a father of lower educational background. The 2005 and 2015 National Oral Health Survey of China also showed that girls exhibited more caries than boys in permanent dentitions[2, 3]. This may be greatly attributed to the earlier eruption of FPMs in girls than in boys[14]. It has been frequently reported that mother’s educational level associated with child’s caries status both in primary and permanent dentition[18, 19]. In our study, father’s education level showed a statistically significant correlation with caries experience among the studied children. Fathers may play more significant roles in their children's dental hygiene practice in Beijing. Another study conducted in Wuhan, China, also found father’s education level plays an important role in their children’s oral health, mainly reflected due to on their responsibility on in managing financial issues for oral health care[20]. Studies have also suggested that low-education families are less diligent about dental care measures and regular preventive visits to dental professionals, resulting in the development of dental caries[20, 21]. Therefore, it is important to include fathers in oral hygiene promotion and education. It is also critical to do the promotion in low-income or families with lower parental education levels.
The contribution of pit and fissure sealants could effectively protect FPMs from caries[22, 23]. From a clinical perspective, it is noteworthy that the best indication for sealants is when FPMs have fully erupted. From our findings, the eruption rate of FPMs was 65.8% and only 24.9% of FPMs were fully erupted with no caries at the age of 6–7 years old. The main target population for the intervention of pit and fissure sealants in the on-going NOHCIP was set at 7–9 years old. Although this may be beneficial in terms of saving time, manpower and resources, this may result in missed opportunity for the most optimal application of sealant and preventing potential tooth decay in some children. Our findings suggest that the sealant procedure should be performed at an earlier age among children in Beijing, which is consistent with findings from studies conducted in other cities in China[14, 24–27]. Furthermore, our results demonstrated that caries often occurred on the occlusal surface of maxillary and mandibular FPMs, the buccal surface of mandibular FPMs, and the lingual surface of maxillary FPMs, which is in agreement with the observations from a Chinese national survey in 2015[14]. Therefore, when applying sealants, special attention should be paid to these high-caries risk tooth surfaces.
The stage of eruption and tooth-specific anatomy are two intra-oral factors for the occurrence and distribution of plaque accumulation[28]. The erupting FPMs are the most caries-prone teeth due to favorable conditions for plaque accumulation[28]. The complex fissures of FPMs are partially covered by gingiva for a considerable period of time[29]. The vulnerability is also attributed to incomplete post eruptive maturation of the enamel[30] and lack of awareness of the tooth emergence[31]. The time between eruption and full functional occlusion is the most important period for maintenance of tooth integrity. The preservation of these non-decayed partially and fully erupted FPMs is of prime importance for the control of dental caries in permanent dentition. Our study found a considerable number of partially erupted FPMs with no caries at this age. In terms of the difficulty in controlling humidity for erupting teeth, the topical application of fluoride on erupting FPMs is desirable to reduce the caries attack to FPMs both clinically and economically favorable[32–36]. In addition, it is necessary to strengthen oral health education and oral hygiene instruction for both children (both girls and boys) and their parents, including both fathers and mothers. This is also an important supplementary measure for oral health promotion. The vast majority of children in China go to elementary school at 6–7 years of age. From then on, children will receive more systematic education in school, which is also a critical period for the formation of oral health behavior.