Arginine Metabolism and Radiotherapy for Head and Neck Cancer

Objectives: Radiation caries, one of the most common and severe sequelae of radiotherapy (RT) for head and neck cancer, is a rapid and highly destructive form of tooth decay. Arginine metabolism via ADS (ADS activity) has been shown to inversely correlate with dental caries. The pilot study was aimed to investigate the influence of radiotherapy on the ADS activity of oral biofilms.
Methods: A total of seven patients with head and neck cancer were assessed before, during, immediate after, and one month after RT. At each study-visit, visual exam of the mouth, survey of oral health behavior, measurement of salivary pH, and collection of supra-gingival dental plaque and stimulated whole saliva were done. Plaque ADS activity was measured by monitoring citrulline production from arginine. QPCR was performed to determine the proportions of major arginolytic bacteria in dental plaque.
Results: One month after RT, four of seven subjects developed incipient caries. Dramatically reduced flow rate and salivary pH were detected in most subjects. ADS activity decreased significantly and composition of arginolytic bacteria in dental plaque shifted with RT.
Conclusions: Our data suggest that ADS activity may be an important risk assessment criterion for radiation caries and enhancement of ammonia production via arginine may be an effective caries intervention strategy for radiation caries.