A prospective cohort study on emergence of permanent teeth and caries experience in Korean children.

OBJECTIVES: The objectives of this study were to investigate permanent tooth emergence during a 9-year longitudinal study and to assess the effect of dental caries in primary teeth on the emergence of permanent teeth. METHODS: Data on caries occurrence in primary teeth were obtained at the baseline by a trained dentist. Permanent tooth emergence data of 539 students from 16 elementary schools in Yeoncheon were examined annually from 1995 to 2003 using dental casts. The median age at emergence of the teeth was calculated using a linear logistic regression model. A multiple linear regression model was used to evaluate the effect of caries on the emergence of permanent teeth. RESULTS: The age of permanent tooth emergence was different between boys and girls, but the difference was not statistically significant at the 5% level. Having 'decayed teeth' hastened the emergence of most second premolars and second molars, whereas the regression coefficients ranged from -1.23 to -0.82. The number of 'filled teeth' showed a correlation with maxillary second premolars and mandibular first premolar, and the regression coefficients ranged from -1.92 to -3.25. CONCLUSIONS: Having dental caries in primary teeth can be a strong predictor of earlier emergence of permanent teeth.

Maximal Inspiratory Pressure and Maximal Expiratory Pressure in Healthy Korean Children.

OBJECTIVE: To evaluate respiratory muscle strength in healthy Korean children in order to establish the criteria for normal reference values for future applications. In contrast with the other parameters for testing pulmonary function, normal values for respiratory muscle strength in healthy Korean children have not been assessed to date. METHODS: We conducted a complete survey of 263 students at Sinmyung Elementary School in Yangsan, Gyeongsangnam-do, and measured their height and body weight, performed pulmonary function tests, and evaluated maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) as measures of respiratory muscle strength. We excluded the subjects with respiratory or cardiovascular diseases that could affect the results. The subjects were children aged 8-12 years, and they consisted of 124 boys and 139 girls. RESULTS: The MIP and MEP values (mean±standard deviation) for the entire subject group were 48.46±18.1 cmH2O and 47.95±16 cmH2O, respectively. Boys showed higher mean values for MIP and MEP in every age group. Korean children showed lower mean values for MIP and MEP compared to those in previous studies conducted in other countries (Brazil and USA). CONCLUSION: Our results showed that boys generally have greater respiratory muscle strength than girls. We found a significant difference between the results of our study and those of previous studies from other countries. We speculate that this may be attributed to differences in ethnicity, nutrition, or daily activities.