To evaluate the cariogenic properties of almond milk beverages, 6 almond milks, along with soy and whole bovine milk, were analyzed for their abilities to support Streptococcus mutans biofilm formation and acid production, and their capacity to buffer changes in pH. Biofilm formation by S. mutans was analyzed using an in vitro 96-well plate model and measured by crystal violet staining. Acid production by S. mutans was evaluated by a colorimetric L-lactate assay and pH measurement of bacterial cultures. Buffering capacity was assessed by a pH titration assay. Soy milk supported the most biofilm growth, while the least was observed with unsweetened almond milk (both p < 0.001). Among almond milks, sucrose-sweetened milk led to the highest level of biofilm formation (p < 0.001), while the least was observed with unsweetened milk (p < 0.05). Sucrose-sweetened almond milk yielded the lowest pH (4.56 ± 0.66), followed by soy milk and bovine milk; the highest pH was with unsweetened almond milk (6.48 ± 0.5). When analyzed by pH titration, the unsweetened almond milk displayed the weakest buffering capacity while bovine milk showed the highest (p < 0.001). These results suggest that the almond milk beverages, except those that are sweetened with sucrose, possess limited cariogenic properties, while soy milk exhibits the most cariogenic potential. As milk alternatives become increasingly popular, dentists must counsel their patients that almond milks, especially sucrose-sweetened varieties, have cariogenic potential. For patients who are lactose-intolerant or suffer from milk allergy, almond milks may be a better alternative than soy-based products.

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Background The dentist has a responsibility to provide nutritional counseling and fluoride consumption recommendations. The purpose of this study was to measure and compare the concentrations of fluoride in a large number of alternative milk beverages and bovine milk. Methods Thirty-three milk alternatives, including 9 diverse types and 11 different brands, were analyzed using a fluoride ion-selective electrode (ISE) and an ISE meter. Fluoride concentrations were then compared among different types and between different brands. Results Fluoride concentration ranged from 0.0071 ppm (Malk® Pure Cashew Milk) to 0.8030 ppm (Almond Breeze® Original Unsweetened Almond Milk) with a mean concentration of 0.3156 ppm. When compared, bovine whole milk (0.0274±0.003 ppm) was found to be significantly lower in fluoride than all samples analyzed except Malk Pure Cashew Milk, Soy Milk Vanilla, Rice Milk, and Pecan Milk. Major differences also existed between the same milk alternative types of different brands. Conclusion The amount of fluoride varies among different types of milk alternatives and different brands. To ensure that the dental team can provide proper recommendations regarding fluoride use, manufacturers should consider placing fluoride concentrations on nutrition labels.

Our previous studies showed that brpA in S. mutans, which encodes a member of the LytR-CpsA-Psr family of proteins, can be cotranscribed with brpB upstream as a bicistronic operon, while the intergenic region also has strong promoter activity. To elucidate how brpA expression is regulated, the promoter regions were analyzed using PCR-based deletions and site-directed mutagenesis and a promoterless luciferase gene as a reporter. Allelic exchange mutagenesis was also used to examine genes encoding putative trans-acting factors, and the impact of such mutations on brpA expression was analyzed by reporter assays. Multiple elements in the short brpA promoter (nucleotide −1 to −344 relative to start cordon ATG) were shown to have a major impact on brpA expression, including an FNR-box, for putative binding site of an FNR-type of transcriptional regulator. When compared to the intact brpA promoter, mutations of the highly conserved nucleotides in FNR-box from TTGATgtttAcCtt to gcacagtttAcCtt resulted in 769-fold increases of luciferase activity (P<0.001), indicative of the FNR-box mediated repression as a major mechanism in regulation of brpA expression. When luciferase reporter was fused to the upstream brpBA promoter (nt −784 to −1144), luciferase activity was decreased by 4.5-fold (P<0.001) in the brpA mutant, TW14D, and by 67.7-fold (P<0.001) in the brpB mutant, JB409, as compared to the wild-type, UA159. However, no such effects were observed when the reporter gene was fused to the short brpA promoter and its derivatives. These results also suggest that brpA expression in S. mutans is auto-regulated through the upstream brpBA promoter.