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Alkali production by oral bacteria via the arginine deiminase system ( ADS) increases the pH of oral biofilms and reduces the risk for development of carious lesions. This study tested the hypothesis that increased availability of arginine in the oral environment through an exogenous source enhances the ADS activity levels in saliva and dental plaque. Saliva and supra-gingival plaque samples were collected from 19 caries-free ( CF) individuals ( DMFT = 0) and 19 caries-active ( CA) individuals ( DMFT ≥ 2) before and after treatment, which comprised the use of a fluoride-free toothpaste containing 1.5% arginine, or a regular fluoride-containing toothpaste twice daily for 4 weeks. ADS activity was measured by quantification of ammonia produced from arginine by oral samples at baseline, after washout period, 4 weeks of treatment, and 2 weeks post-treatment. Higher ADS activity levels were observed in plaque samples from CF compared to those of CA individuals ( P = 0.048) at baseline. The use of the arginine toothpaste significantly increased ADS activity in plaque of CA individuals ( P = 0.026). The plaque microbial profiles of CA treated with the arginine toothpaste showed a shift in bacterial composition to a healthier community, more similar to that of CF individuals. Thus, an anti-caries effect may be expected from arginine-containing formulations due in large part to the enhancement of ADS activity levels and potential favorable modification to the composition of the oral microbiome. [ABSTRACT FROM AUTHOR]

Abstract: Objective: Dietary sugar exposures induce an immediate drop of the plaque pH. Based on in vitro observations, it was hypothesized that oral bacteria may rapidly respond to this environmental change by increasing the activity or expression of alkali-generating pathways, such as the urease pathway. The objective of this exploratory in vivo study was to determine the short-term effect of a brief sucrose exposure on plaque and saliva urease activity and expression, and to relate this effect to caries experience. Methods: Urease activity levels were measured in plaque and saliva samples collected from 20 children during fasting conditions and 30min after rinsing with a sucrose solution. Streptococcus salivarius ureC-specific mRNA in saliva was quantified using real-time RT-PCR. The impact of host-related factors, such as age, gender, sugar consumption, salivary mutans streptococci levels and caries status on urease activity was evaluated. Results: Plaque urease activity under fasting conditions was higher in subjects with low caries and mutans streptococci levels. This difference was not observed after the sucrose exposure. The response of urease to sucrose in vivo did not depend on caries experience or salivary mutans levels. Significant increase in urease activity of plaque and saliva after exposure to sucrose was observed only in the subjects who had low urease levels at baseline. Conclusions: The findings of this exploratory study suggest that plaque urease activity may have an important long-term influence in caries development but not during a cariogenic challenge. [Copyright &y& Elsevier]