Our study found high prevalences of ECC and S-ECC (78.2% and 41.2%, respectively) among preschool children aged 3–5 years who were living in Xinjiang. The prevalence of ECC in this survey was significantly higher than that in children in mainland China overall (53.6%) in 2010–2013 . The prevalence of ECC in 5-year-old children (84.5%) is not only higher than that in other surveys from adjacent provinces (71.4% in Qinghai, 73.8% in Nei Mongol, 55.8% in Gansu) , but also higher than that in surveys from neighboring developing countries, including Pakistan (43.7%) , India (58.6%) , and Nepal (52%) . Among those studies, an S-ECC prevalence of only 13% was reported in Pakistan . Our prevalence of ECC is three times higher than that in Pakistan and is similar to the high prevalence of severe caries (44.1%) reported in Northern Thailand . Moreover, we found a high mean dmft of 5.61 for ECC and 8.17 for S-ECC, as well as a very low filling rate (1.7%) among local preschool children.
The current prevalence and treatment status of ECC highlight the fact that caries remains a serious and urgent problem among children in Xinjiang. In accordance with several known orcontroversial factors related to ECC and S-ECC identified in previous studies [1, 11, 12, 20], the prevalence of ECC is determined by a complex interaction between sociodemographic and behavioral factors. Lower sociodemographic status (region, less well-educated mother, low-income family, caregiver with cavities), risky dietary behavior (high-frequency sweets consumption, often eating before sleep), risky oral hygiene behavior (starting tooth brushing at an older age), and use of a dental service (dental visit in the past, parents had received oral health care instruction) were associated with ECC and S-ECC in the present study. Our study found that Ining (81.9%) and Kashgar (74.8%) children had a high prevalence of ECC and the prevalence was significantly different between the two regions. The higher caries rates of children in the two regions may reflect inequalities in socioeconomic conditions, an inadequate governmental oral health care system, limited human resources, poor behaviors, and limited awareness of oral health care measures. According to data from the Xinjiang Statistics Bureau in 2013 , local governmental health expenditure of 160.91 billion RMB accounted for 4.6% of the total health care budget, but the spending on oral health care was very low. Although there are no accurate statistics, it is likely that over 90% of total oral health expenditure in Xinjiang is not covered by basic medical insurance. Oral care services are paid for mainly by patients themselves. During the same year, the average annual income in Xinjiang was 13,585 RMB, and only 7296 RMB for a rural family, so most low-income families could not afford dental treatment, which may be one reason for the high caries and low filling rates in the region. People with a lower income and poor educational level usually have a relatively lower life expectancy, and children from low-income families are more likely to suffer from childhood illnesses . Moreover, maternal education influences beliefs and attitudes towards the oral health care of children . Mothers and caregivers play a role in cultivating children’s dental health behavior, including tooth brushing, dental care, and dietary habits, which are acknowledged to be protective factors for the primary teeth [15, 20]. Like in other studies [13, 15, 27], the present study found negative associations of a more highly educated mother and a higher average annual income with ECC, and in contrast, there was a positive correlation between caregivers with cavities and caries rates.
Furthermore, the number of registered dentists in Xinjiang was 2573 in 2013 and the dentist to population ratio was only 1:8800, which is far below the average of approximately 1:2000 in most developing countries . The shortage of dentists, particularly specialists in pediatric dentistry, is another important reason for the lack of treatment available for ECC in the less developed frontier provinces of China . Further, risky dietary [6, 14] and poor oral hygiene [11, 15] behaviors have been found to be strongly associated with the prevalence of ECC. As reported in previous studies, we found that a low frequency of sweets consumption, no eating before sleep, and starting tooth brushing at a younger age had a significant negative relationship with the risk for caries. Fewer public oral health education initiatives have been undertaken by government medical organizations or individuals in the two study regions. Most parents and caretakers were unaware of their children’s oral health status. Among the poorly educated Uygur parents, the language barrier added to their difficulty of accessing oral health information, which may be another reason for the severe caries status in their children. It would be helpful to provide information not only in Chinese but also in the native languages of minority groups when implementing dental health education strategies. Most parents did not focus on oral health care information until their children visited a dentist for severe toothache. Hence, we found that many children with ECC and S-ECC had made a dental visit in the past, because their parents had received oral health care instruction. Therefore, it seems that dentists do not play an effective role in caries prevention practices , probably because the demand for dental care is highly symptom-driven. This, together with the scarcity of dental health care services, may leave the dentist with little time and opportunity to provide preventive advice. These observations highlight the need for development of local oral health care policy to protect primary dentition, insurance reform to cover the field of oral preventive services, an improved oral health care system and health education for the public, more dentists in the rural regions, and promotion of the preventive role of dentists.
This study has some limitations, particularly its cross-sectional design, which did not allow for investigation of a cause-effect relationship. Further, only a small number of subjects were selected from more than 10,000 eligible children. We tried to minimize this potential source of selection bias by enrolling children from as many kindergartens as possible in the two study regions. Further, we cannot exclude the possibility of a degree of response bias because the data from caregivers were retrospective and caregivers may have responded with the intention of pleasing the interviewer or been guided by them during the interview. Future research on this topic should include a longitudinal study design and a larger study population.