Urease Activity Levels and Dental Caries Status in Children

Urea is normally present in saliva at concentrations up to 10mM. A number of oral bacteria produce urease enzymes, which catalyze the hydrolysis of urea into ammonia and CO₂ causing significant increases in the plaque pH. It is, therefore, believed that urease activity in the oral cavity may inhibit the development of dental caries. OBJECTIVE: To determine if there is a difference in plaque and/or saliva urease levels among caries-free (CF) vs caries-experienced (CE) children. METHODS: Pooled supragingival plaque and whole un-stimulated saliva samples were obtained from 19 CF (d₃mfs+D₃MFS=0) and 16 CE (mean d₃mfs+D₃MFS=10.9±9.57) children 3-12 years of age. A second plaque and saliva sample were obtained in 20 of the children one week following the first sample collection. Dental caries were scored using the Fiber-Optic Trans-Illumination method (FOTI) with Ekstrand's criteria. Urease activity was defined as nmoles urea hydrolyzed/min/mg of protein. Generalized Linear Latent and Mixed Models (GLLAMM) were used to examine the association between urease levels and dental caries. RESULTS: Plaque urease levels in the CF group ranged from 1630 to 24626 nmoles urea hydrolyzed/min/mg (mean 6365. 97±4339.21) and in the CE group from 450 to 10164 (mean 4539.75±2795.05). Salivary urease levels in the CF group ranged from 0 to 1571 nmoles urea hydrolyzed/min/mg (mean 413.37±357.42) and in the CE group from 0 to 991 (mean 349.02±246.97). The GLLAMM results revealed a significant difference in log-transformed mean plaque urease levels between CF and CE groups (b=-0.404, 95%CI=-0.804, -0.004, p=0.048). No significant difference was found in saliva urease levels (b=0.407, 95%CI=-0.876, 1.69, p=0.534). CONCLUSIONS: The results of this study demonstrate that CF children have significantly higher levels of urease activity in their plaque compared to CE children.

Supported by RCRII Grant #1P20 RR 11126 from NCRR.