Overall dental maturity was studied semilongitudinally in a group of 248 healthy children born in Helsinki in 1968-73. In all, 738 orthopantomograms were taken of these children at ages of 2.5-16.5 years. Overall dental maturity was estimated by the method of Demirjian and Goldstein, which is based on the development of seven left mandibular permanent teeth. The aim of the study was to construct dental maturity curves for Finnish children and to compare their dental maturity with that of French-Canadian children studied by the same method. The Finnish children were more advanced in dental maturation than French-Canadian children (p less than 0.01). In boys the advancement was seen at the age of 5-10 years and in girls at the age of 4-12 years. These findings suggest differences in overall dental maturity among white population groups.
The aim of the study was to evaluate the capability of caries-related salivary tests and a test based on past caries experience (baseline DFS) to select persons at high risk for caries. The subjects (n = 122) were 12-17 years old at the beginning of the study. Caries was registered and salivary samples were taken annually during the 3-study period. The 3-year caries increment was positively correlated to the baseline DFS (r = 0.46, p less than 0.001), salivary level of mutans streptococci (r = 0.30, p less than 0.001) and lactobacilli (r = 0.30, p less than 0.001), and combined level of mutans streptococci and lactobacilli (r = 0.39, p less than 0.001) and negatively correlated to the buffering capacity of saliva (r = -0.22, p less than 0.05). Tests based on either past caries experience or mutans streptococci or lactobacilli levels alone were not efficient in selecting persons at high risk for caries. Among the tests, DFS was the most sensitive and specific. A combination of either microbial test and DFS was more efficient to select persons at risk than various alternatives alone. The sensitivity was 84% and the specificity 62% for the combination of lactobacilli test and DFS and 71% and 79% respectively for the combination of mutans streptococci and DFS. In the former combination the positive prediction value was 43% and in the latter 56%.
An unfavourable root-crown (R/C) ratio caused by short dental roots may result from a developmental deficiency, root resorption after orthodontic treatment, or dental trauma. In the assessment of root shortening, subjective grading has often been used. For objective tooth measurements, varying materials and methods may make the results impossible to compare. This study used a simple, objective method to assess the R/C ratio (relative root length) of mature permanent teeth from panoramic radiographs (PRGs), tested its reproducibility and calculated the mean values of R/C ratios and their variations in a healthy Caucasian (Finnish) population. Two thousand seven hundred and seventy-nine teeth were measured on 108 PRGs. The intra- and inter-examiner reproducibility of the assessment method was good (Pearson correlation coefficients 0.87 and 0.83, respectively; P < 0.001) and the mean R/C ratios did not differ between the repeated measurements (P > 0.05). The biological variance in all cases exceeded the error variance for each tooth. These facts suggest that the method reported in this study can be used in the assessment of the relative root length of 'normal' teeth and its alterations in teeth with developmental or acquired aberrations of dental roots. Males, overall, tended to have higher R/C ratios than females; P-values varied from non-significant to less than 0.01. With the exception of the permanent lateral incisors in males and the permanent second molars in both genders, the ratios of the antagonist teeth were significantly greater in the mandible than in the maxilla (P < 0.05 for the lateral incisors of females; P < 0.001 for all other teeth). Consequently, in quantifying root shortening in developmentally short-rooted teeth, tooth- and gender-specific reference values should be employed. The Finnish R/C data reported here for all teeth except third molars could be used for comparison with other populations, patient groups or individuals where crown-root aberrations are suspected.
Sizes of horizontal wear facets of maxillary anterior teeth were studied longitudinally from the primary dentition at age five to the young adult dentition at the age of 18 years. By a planimetric method, we calculated the wear areas on dental casts taken at the ages of five, ten, 14, and 18 years from the dentition of 39 healthy, orthodontically untreated subjects with good morphological occlusion. For young adults, we also studied the association between the amount of wear and reported parafunctions, maximal bite force, salivary buffer capacity, salivary flow rate, and some cephalometric variables. Size of wear facets on all anterior teeth increased with age. Significant correlations were found between the total wear areas of the six anterior primary teeth at five years of age and those of their permanent successors at age 14 (r = 0.44) and 18 (r = 0.39). For an individual, tooth wear at five years of age was, however, of low predictive value for tooth wear in young adulthood, whereas tooth wear at 14 years of age predicted it well (r = 0.89). Highest correlations between tooth wear and background factors at 18 years of age were found for maximal anterior bite force (r = 0.44) and for the size of the gonial angle (r = -0.31). Wear of anterior teeth was not associated with reported parafunctions in young adulthood.
Variations in landmark location lead to differences in numeric evaluation of the anatomic relationships in the skull base area. These differences were, however, shown to have little clinical significance. Hence, the documented methods are applicable for screening of basilar pathology.
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