Comparison of pharyngeal airway dimension, tongue and hyoid bone position based on ANB angle.

OBJECTIVE: This study was undertaken to cephalometrically evaluate the pharyngeal airway dimension, tongue and hyoid position in subjects with normal nasorespiratory functions having different dentofacial patterns (A-point-nasion-B-point [ANB] >40 and ANB <40) and to find if a correlation existed. MATERIALS AND METHODS: Class I and Class II Division I patients were selected randomly. Lateral head cephalograms were taken in normal head position within a lead foil attached to the tongue tip and a barium coating on the dorsal surface of tongue. The lateral cephalograms obtained were traced using lead acetate paper and measurements were taken. Different analyses were done for the pharyngeal airways, hyoid bone, and tongue. RESULTS: The ANB angle is a significant predictor for Class I and Class II Division I malocclusion, and the mean ANB angle of Class II Division I was different and higher. The overall mean pharynx and hyoid parameters were different and lower in Class II Division I patients than in Class I patients. The mean tongue parameter almost remained the same except for the tongue position (TT-LOP), which was higher in Class II Division I. CONCLUSION: In general, there was no difference either in the pharyngeal airway anterioposterior dimension or in the position and relationship of the hyoid bone and tongue, between Class I and Class II Division I patients. These findings are consistent with the findings in studies. Anterioposterior dimension of the upper airway is usually maintained by adaptation of both the tongue and the hyoid bone. The result should be viewed in the light of the fact that only anterioposterior dimensions were taken into consideration; the vertical and transverse dimensions of these complex anatomical structures need to have newer three-dimensional (3-D) imaging technique to find if a correlation existed between them, making future studies more comprehensive.

Estimation of nickel and chromium in saliva of patients with fixed orthodontic appliances.

AIM: To examine whether orthodontic treatment induces an increase in salivary nickel and chromium concentration. METHODS: Ten new patients (7 females and 3 males) beginning fixed orthodontic treatment were included in the study. The mean age of the sample was 17.5 years (range 14 to 24 years). Three samples of stimulated saliva were collected from each orthodontic patient, 1 at each of the following times: before insertion of the fixed appliance (which served as a baseline/reference level for salivary nickel and chromium content), 1 week after insertion of the appliance, and 3 weeks after insertion of the appliance. These samples were analyzed for nickel and chromium content using the atomic absorption spectrometer and their values recorded in ng/mL. The Friedman test was used to test the statistical significance of differences in concentrations of each metal before and after insertion of orthodontic appliances. Post-hoc comparisons were performed using the Wilcoxon signed rank test and Mann-Whitney U test. RESULTS: This study showed that there was a statistically significant difference in salivary nickel and chromium concentrations before and 1 week and 3 weeks after insertion of fixed orthodontic appliances. The highest concentrations of nickel and chromium were found after 1 week. The salivary nickel and chromium concentrations tapered off 3 weeks after insertion but were significantly higher than baseline levels. CONCLUSION: The salivary nickel and chromium concentrations significantly increased after insertion of fixed orthodontic appliances as compared to baseline levels, with the maximum concentration seen in the first week after placement of fixed orthodontic appliances.

Biometric study of tooth size in normal, crowded, and spaced permanent dentitions.

INTRODUCTION: At present, there is a void in the orthodontist's armamentarium with regard to the assessment of malocclusion due, in part, to tooth size. A biometric study of tooth size was carried out to examine the extent to which tooth size contributes to dental crowding or spacing. METHODS: A sample of 240 orthodontic study casts was selected from a larger sample. These casts met the selection criteria. The sample was divided into crowded, spaced, and normal dentition groups with 80 casts in each group. The criterion of grouping was based on the tooth size-arch length discrepancy in the arch. Each group comprised 40 maxillary and 40 mandibular casts that were further divided equally by sex. The data were statistically analyzed. RESULTS: Mesiodistal crown dimensions of individual teeth, the sum of the incisors, and the sum of the canines and the premolars were uniformly larger in crowded arches than in normal and spaced dentition groups. Mesiodistal crown dimensions of individual teeth were smaller in the spaced arches compared with normal dental arches, but the difference was significant only in the combined mesiodistal crown dimensions of the mandibular incisors. Correlations of the combined mesiodistal crown dimensions of the incisors with the combined mesiodistal crown dimensions of the canines and the premolars were positive in all 3 groups. CONCLUSIONS: Mesiodistal tooth size is an important factor in the assessment of crowding or spacing and in orthodontic treatment planning.