[Relationship between cariogenic microbe, salivary buffer capacity and early childhood caries]

To investigate the relationship between Mutans streptococcus (MS), Lactobacilli (LB), pH value and buffer capacity of saliva and early childhood caries (ECC).

A total of 178 children aged from 42 to 54 months were recruited from 14 urban kindergartens in Beijing. The ECC group contained 87 children with more than 5 decayed teeth, and the control group was composed of 91 caries-free children. Unstimulated (UWS, 2 ml) and stimulated (SWS, 2 ml) whole saliva were collected in each subject. The pH value and buffer capacity of saliva were measured using an electro-acidimeter (+/- 0.01pH).

MS and LB were isolated from 96.6% and 79.3% of children with ECC, which were significantly higher than those (63.7%, 27.5%) of caries-free children (P < 0.05) respectively. The counts of MS and LB in children with ECC were approximately 10 times higher than that in caries-free children. Initial pH value and buffer capacity of SWS were significantly higher than that of UWS (P < 0.001) in both groups. The pH value and buffer capacity of both UWS and SWS in ECC children were significantly higher than caries-free children (P < 0.05). There were no significant correlations between MS, LB and pH value and buffer capacity of saliva in caries-free children. Significant correlation (r = 0.249, P < 0.05) was found between the numbers of MS and buffer capacity of stimulated saliva in ECC children.

MS and LB were important pathogens for ECC. Lower initial pH value and buffer capacity of saliva may be an important factor of ECC.