RESUMEN
OBJECTIVE: To examine the rate and pattern of early childhood caries (ECC) development and to investigate the transitional changes of the carious lesions during a follow-up period of 3-9 months. METHODS: A longitudinal observational community-based survey of 599 children, 9-18 months old. The children's dental examinations were first carried out at the age of 9 months with re-examination at 12 and 18 months by five dentists using standardized methods. The affected rates of dental caries were determined for prevalence, incidence density for risk of caries per person (IDp) and risk by surface (IDs). Changes in dental status over time were explored from unerupted (U) to sound (S), including enamel caries (D1), dentine caries (D2) and caries involving pulp (D3) by computing transitional probabilities. RESULTS: The prevalence of caries was 2.0%, 22.8% and 68.1% among 9-, 12- and 18-month olds, respectively. The IDp observed for newly affected children 9-12 and 12-18 months old was 10.32 and 15.70 persons/100 person-months, respectively. The IDs for children 9-12 months old was 2.17 newly affected surfaces/100 surface-months whereas it was 2.22 surfaces/100 surface-months for children 12-18 months old. The buccal surface of maxillary incisors was the most affected (44.9%) followed by lingual, mesial and distal surfaces, respectively. The transitional probability of caries progression ranged between 1.79% and 15.38% during the follow-up period from 9 to 12 months old. It was 3.43-39.60% from 12 to 18 months old. CONCLUSIONS: 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.