Teeth are formed from the epithelium of the oral surface and the underlying tissues. The development of teeth begins with the basal layer of the epithelium and the condensed mesenchyme beneath it. The epithelium forms the tooth germ, which continues to grow and undergo morphogenesis, determining the shape of the future tooth crown. The formation of dentin and enamel begins at the interface between the epithelium and mesenchyme, and after the crown is completed, root development commences[11]. The development of teeth is inextricably linked to vitamins; for instance, vitamin C can induce the differentiation of periodontal ligament and osteoblasts[12]. Concurrently, vitamins play a significant role in the disease process of caries. Vitamin C maintains dental health by forming collagen, and a deficiency in vitamin C can lead to the destruction of tooth structure[13]. Eydou pointed out that vitamin C can inhibit the growth and biofilm formation of Streptococcus mutans, a pathogen in caries, making it an effective anticaries agent[14]. However, on the other hand, after consumption, vitamin C dissolves and releases hydrogen ions (H+) in the oral cavity, causing the oral environment to become acidic, leading to the dissolution of hydroxyapatite on the tooth surface and subsequently causing tooth decay and the onset of caries[15]. This is consistent with the multiple linear regression results of this study, which show that excessive intake of vitamin C leads to an increase in the number of decayed teeth (D) (Table 2, Model 2).
We have confirmed that vitamins influence the number of decayed teeth (D) to a certain extent. Vitamin D is an essential substance for the intestinal absorption of calcium, magnesium, and phosphorus, which are indispensable for the mineralization of bones and teeth[16]. During the development of dentin, the levels of calcium and phosphate in the plasma are regulated by vitamin D and promote mineralization by binding to tooth cells. The tooth surface may demineralize due to acid-producing bacteria, but vitamin D can maintain sufficient levels of calcium and phosphate in saliva for remineralization after demineralization[17], thereby serving as an anticaries purpose. Numerous studies have found a significant association between vitamin D levels and the occurrence of caries[18–21], which is similar to the results of our study. Our findings also indicate that an appropriate intake of vitamin D can reduce the number of decayed teeth (D). Vitamin D has an impact on the reduction of the total number of decayed teeth in caries, and its intake can effectively decrease the number of decayed teeth (D). Moreover, a deficiency in vitamin D can lead to incomplete calcification of dentin in primary and permanent teeth, delayed eruption, and the occurrence of wear and cracked tooth[22].
The demographic findings of this study revealed that older individuals are more susceptible to caries. This is attributed to the deterioration of overall health and the presence of comorbidities with increasing age in the elderly, which elevates the risk of caries[23]. The subgroup analysis in this study identified that individuals aged 60–80 are particularly influenced by vitamins B6 and C, and a survey indicated that the prevalence of caries in individuals over 60 years old is 76.4%[24].
The study's results indicated that BMI affects the total number of decayed teeth, with lower BMI populations exhibiting a higher number of decayed teeth (D). Research has shown that malnourished children may suffer from more caries, as high sugar intake can be detrimental to dental health and nutrition, leading to controlled intake of high-sugar foods that result in a low BMI[25]. Non-Hispanic blacks have relatively fewer decayed teeth (D) compared to non-Hispanic whites. The study's findings also suggest that women have a higher number of decayed teeth (D) than men, consistent with previous research[26], possibly due to earlier tooth eruption in females, preference for sweets, and hormonal changes[27]. Subgroup analysis indicated that males are influenced by B vitamins (B1, B2, B6, and B12) and vitamin C, while females are affected by vitamin B2 and vitamin K. Due to the unique physiological structure of women, their caries incidence is influenced by fluctuations in estrogen levels, saliva composition and flow rate, and food cravings and aversions during pregnancy[28], hence the impact of vitamin nutrients also differs between males and females.
Among the B vitamins (B1, B2, B6, B9, and B12), only vitamin B6 was found to influence the number of decayed teeth (D), with reduced intake of vitamin B6 leading to a lower prevalence of caries. Studies have observed that an increase in caries prevalence may be related to a significant increase in the requirement for vitamin B6[29]. Vitamin B6 has immunomodulatory functions, but excessive doses of vitamin B6 beyond the required amount can impair immune responses[30], leading to sensory neuropathy and insufficient blood supply to pulp tissue[31], which in turn can result in the occurrence of caries.