Background/Objectives: Vitamin D helps the mineralization of bone, teeth, and other calcified tissues by regulating calcium–phosphate metabolism. The nuclear activation of the vitamin D receptor (VDR) gene is essential for the effectiveness of vitamin D. The main objective of this study is to determine the role of vitamin D levels and VDR gene variants in dental caries. Methods: This study included 128 3–6-year-old children who were divided into 64 caries-free and 64 carious children. Blood samples were taken, and serum 25-hydroxyvitamin D levels were measured. Intraoral examinations were performed to record dmft index values. Genetic testing was performed on 26 children to examine VDR gene variations. Relevant gene regions were amplified using PCR and sequenced via Sanger sequencing in a total of 13 caries-free and 13 carious children. Stats analyses included chi-square/trend tests to compare count data; Student’s T/Mann–Whitney U tests for two-group normally/non-normally distributed data; and the Kruskal–Wallis test for 3+ groups with non-normal data. Results: The results showed that vitamin D levels were relatively low in the caries group, but no statistically significant relationship was found between vitamin D levels and caries. No mutations were detected in the VDR gene in either group, and there was no significant difference observed in terms of the number of ApaI, TaqI, and FokI polymorphisms. Based on these findings, the use of prophylactic vitamin D supplements to prevent caries formation or development cannot be recommended. Conclusions: This study provides important insights into the relationship between vitamin D and dental caries and can contribute to the development of effective preventive strategies for oral and dental health.

This study evaluated whether commonly used household cleaning agents affect the surface microhardness of acrylic and copolyester materials used in pediatric removable appliances and sought to identify safe options for daily home cleaning. Standardized acrylic and copolyester specimens were exposed to a short-term, clinically relevant brushing regimen using tap water (control), children’s toothpaste, liquid soap, antibacterial liquid soap, 20% saline solution, or 20% sodium bicarbonate (“carbonated”) solution. Surface microhardness was assessed with Vickers testing, and surface features were examined by light microscopy. In the acrylic group, antibacterial liquid soap and the carbonated solution were associated with reduced microhardness (Spearman ρ = −0.622 and −0.532, respectively; both p < 0.001) and more pronounced surface alterations. In the copolyester group, antibacterial liquid soap showed a significant inverse association with microhardness in regression analysis (p = 0.032), while the other agents showed no statistically significant relationships (p > 0.05). Clinically, antibacterial liquid soap should be avoided for routine cleaning of both acrylic and copolyester appliances, and sodium bicarbonate–based carbonated solutions may be detrimental to acrylic. Children’s toothpaste and ordinary liquid soap appear to be practical, safer alternatives for daily use.