Because of the high incidence of early childhood caries (ECC), a longitudinal study to identify risk factors from the prenatal period to the child's first birthday among 9- to 18-month-old children was conducted with negative binomial modeling. Overall, 495 children had dental examinations at ages 9, 12, and 18 months. Mothers were interviewed during the 2nd trimester of pregnancy and when the children had dental examinations. The highest incidence of caries was found among children who were born to mothers with >or= 10 decayed teeth and who never received calcium supplements during pregnancy, and children who were not fed supplementary foods at age 3 months, had sweet-tasting foods at 5 months, started snacking at 5 months, had sugary snacks, had soft drinks, and did not have their teeth brushed daily at 9 months. Thus, prenatal care and child-rearing-practices during and after birth are important risk factors for the incidence and incremental rate of ECC.

An extremely high caries-affected rate was found among the study children even before the age of 18 months. The buccal surface of the maxillary incisors was the most affected. The teeth acquired caries at 3-6 months after initial eruption and carious lesions developed continuously over time.

Lactobacilli have been associated with the presence and progression of dental caries. Nevertheless, the relation between certain species or genotypes of Lactobacillus and caries is unclear and there are no data available for the Thai population. This study aimed to examine the distribution of species and genotypes of oral Lactobacillus among children with rather high caries prevalence, and to investigate whether certain species or genotypes were more related to caries activity than others. One hundred and sixty-five children were examined for caries status. Saliva samples were collected and the numbers of lactobacilli were counted. A total of 357 Lactobacillus isolates from 59 children were identified to species level by 16S ribosomal RNA genes polymerase chain reaction (PCR) -restriction fragment length polymorphism and 16S ribosomal RNA gene sequencing. Furthermore, 304 isolates from 56 children were genotyped using arbitrarily primed PCR. Significant correlation was found between levels of lactobacilli and dental caries (P < 0.001). Among the 10 identified species of Lactobacillus, L. salivarius was more prevalent in children with moderate to high caries prevalence compared with children with low caries prevalence, while L. fermentum was the most predominant species in all study groups. Moreover, a genetic heterogeneity of Lactobacillus species was found among the children and those with high caries prevalence tended to be colonized with more than one clonal type. In summary, L. salivarius may be a putative caries pathogen among preschool Thai children.

This longitudinal study shows early colonisation of the mouths of Thai children by MS/lactobacilli and where there are persistently high levels of the bacterias increased risk of development of dental caries.

There was variation in acid production and growth between the Lactobacillus species. The strongest acid producers were Lactobacillus salivarius, Lactobacillus rhamnosus, Lactobacillus plantarum, and Lactobacillus casei/paracasei, respectively. It seems possible that these species might play a more important role in caries development than the others.