RESUMEN
OBJECTIVE: To explore a selected-media of Bifidobacterium from oral cavity, to detect the distribution of Bifidobacterium in different sites of children and primarily investigate the relationship between oral Bifidobacterium and early childhood caries. METHODS: 70 children aged from 3 to 5-year-old were selected, 30 children were caries-free and 40 were severe early childhood caries (S-ECC). Saliva was collected and plaque samples from the 30 healthy subjects were pooled. For S-ECC group, plaques were collected separately from four different sites as follows: Saliva, surfaces of intact enamel, surfaces of white spot-lesions, and deep dentin-lesions. Samples would be grown in the selected-media, and the whole DNA of bacteria was extracted. Polymerase chain reaction was performed with specific primers and the results were analyzed by the electrophoresis. RESULTS: Bifidobacterium were detected 0 in the caries-free children, while 47.5% in the S-ECC group. There was significant difference between two groups (P < 0.05) and there was no difference between different sites of teeth in S-ECC group (P > 0.05). 27.5% Bifidobacterium were detected in saliva, 27.5% on surfaces of intact enamel, 20.0% on surfaces of white spot-lesions and 22.5% in deep dentin-lesions. 10% Bifidobacterium dentium were detected in saliva, 7.5% on surfaces of intact enamel, 7.5% on surfaces of white spot-lesions and 10.0% in deep dentin-lesions. CONCLUSION: One type of modified selected media of Bifidobacterium in oral cavity was explored. Bifidobacterium may be related to the occurrence of the S-ECC and has nothing to do with different sites of teeth in children.