As life expectancy rise, the older adults is a rapidly growing proportion of the world’s population [25]. With aging, the exposure to risk factors may increase the progression of dental caries. In the present study, we reported the caries status using both the DMFT and DF-root indices, which was consistent with the latest National Oral Health survey and most of the previous studies [4, 15]. In this way, the results could be easily compared. However, in many cases, we were unsure if teeth were missing due to caries or periodontal diseases, so dental caries experiences could be overestimated.
In this study, the majority of the participants had experienced dental caries (87%), although this percentage was lower than the national survey (98%) [15]. However, it was significantly higher than the percentage in Sichuan (77%) and the northeastern provinces of China (64%) [26, 27]. Previous studies showed differences in the prevalence of root caries among elderly worldwide, ranging from 25%-100% [28]. The prevalence of root caries in our study (55%) was found lower than that in the national survey (64%). In general, the dental caries burden in both crowns and roots was still heavy among the elderly in the rural areas of Yunnan province.
Note that the prevalence of the edentulousness in this study was twice the percentages reported in Sichuan and Hong Kong [26, 29]. Tooth loss is a robust measurement of the combined burden of untreated dental caries or unsuccessfully treated periodontal disease [30]. Our results show that this high prevalence of edentulism could mainly cause by the lack of prevention and treatment for both dental caries and periodontal disease. As mentioned before, the financial barriers and limited access to oral health care could have contributed to their poor oral health status. Therefore, oral health strategies should be implemented to provide accessible and affordable dental care services throughout rural areas to further improve tooth retention.
Although many previous studies have reported a negative correlation between education level and caries, a statistically significant correlation was not detected in this study [31]. This may be due to the generally low education level among the participants. Meanwhile, we found that the most of the participants had inadequate dental knowledge, even though the national oral health education programs, such as “Love Teeth Day” campaign [32], were carried out every year to pass on the oral health care knowledge. This study showed that changes should be considered when providing oral health promotion programs, focusing on oral health knowledge and awareness, and the importance of regular visits to the dentist, especially for these with a low education level.
In the final model, gender was significantly associated with the caries experience. Women were more likely to experience dental caries than men. This was consistent with many previous studies [15, 27]. One explanation is the earlier tooth eruption among women than men. This prolonged tooth exposure in the oral environment could have increased the susceptibility to dental caries. Nevertheless, the traditional belief in China that women should not brush their teeth in the first month after childbirth could also be considered a factor that led to their higher caries rate. Additionally, marital status is also an essential factor that influenced the caries prevalence among the elderly, which is consistent with previous studies [27]. Divorced or widowed elderly had the highest mean DMFT scores. However, the reason for this phenomenon remain unclear.
Some socio-demographic factors, such as ethnicity and annual household income, are usually defined as risk factors for dental caries [31, 33]. In this study, these influence on dental caries experience was less than geographic variable. Therefore, they were not included in the finally model. People living in the less developed district (Jianchuan district) had higher mean DMFT scores than the participants living in Ninger district. Considerable inequalities in dental caries due to the place of residence were also observed among the older population in other parts of China [15].
This study had a high response rate, due to the support of the local health department. A multistage stratified sampling method was used because it was a convenient method that could provide a high statistical precision by choosing participants from all of the strata. Besides, a face-to-face interview method was employed, which significantly improved the reliability of the data. However, it should be noted that the massive internal urbanization occurred in 1980s [34]. Elderly with immigration experiences could access better oral health services in urban cities. This might had played a positive effect on their oral health status. However, this confounding factor was not investigated in the present study. Meanwhile, according to the available data in Yunnan, there were 2% of the elderly staying in the elderly homes, but they were not included in this study [12]. Therefore, the results of this study should still be interpreted with caution.