Abstract: PURPOSE: To investigated the relationship between the capacity of oral samples to produce ammonia from urea and caries experience by measuring urease activity in saliva and dental plaque samples from children. METHODS: Samples of the saliva and dental plaque were collected from 98 subjects between 3 to 6 years old, the oral condition were recorded. The samples were divided into three groups: caries free group, medium caries group and high caries group according to caries statues. Urease activity was determined by testing the ammonia nitrogen concentration of samples of subjects. With SPSS 19.0 software package, variance analysis and correlation analysis were used to determine the relationship of urease activity with dental caries in primary teeth. RESULTS: The amount of ammonia generated from the test substrates by plaque samples between caries free group, medium caries group and high caries group had statistical significance. By correlation analysis, there was positive correlation between caries statue and urease activity. CONCLUSIONS: This study supported the theory that increased caries risk was associated with reduced alkali-generating capacity of the bacteria colonizing the oral cavity; providing compelling evidence to further our understanding of oral alkali-generation in health and disease.

Key words: Urease, Urea catabolism, Caries, Primary teeth