Arginine metabolism may confer caries resistance in children

Alkali production by oral bacteria influences the ecological and chemical balances between tooth minerals and microbial biofilms by counteracting the effects of acidification from sugar metabolism.  The arginine deiminase system (ADS) is a significant pH homeostasis mechanism in dental plaque, and appears to contribute in major ways to caries resistance in adults.  Objectives: To examine the relationship between the arginolytic potential of plaque bacteria and caries experience in children.  Methods: A total of 100 children aged 2 to 14 years were recruited and grouped by caries status: caries-free (CF), caries-active (CA), or caries experienced (CE); and by type of dentition: primary, mixed or permanent.  Supragingival plaque was collected from caries-free tooth surfaces (PF), and from dentinal (PD) and enamel caries lesions (PE).  Plaque ADS activity was measured by monitoring citrulline production from arginine.  Results: Plaque ADS activity ranged from 0.08 to 968.5 units (mg protein)^-1.  The mean ADS activity of all plaque collected from CF (375.2) was higher, but not significantly, than that of CE (298.2) and CA (290.2) children.  Regardless of children caries status or type of dentition, PF (378.6) had significantly higher ADS activity compared to PD (208.4; p<0.001) and PE (194.8; p=0.005).  There was no significant difference in the PF arginolytic activity among children with different caries status.  Mixed model analysis showed that plaque caries status is significantly correlated with ADS activity despite children’s age, dentition and caries status (p<0.001), with healthy plaque predicting higher ADS activity compared to diseased plaque.  Conclusions:  Plaque arginine metabolism varies greatly among children, which may affect their resistance or susceptibility to dental caries.  This study revealed a positive relationship between alkali-generating potential of dental plaque via ADS with dental health in children.