RESUMO
Objetivo: Determinar la exactitud del Índice de Tanaka-Johnston e Índice de Moyers mediante el análisis de modelos de estudio iniciales con dentición definitiva de pacientes chilenos del Postgrado de Ortodoncia de la Universidad Andrés Bello sede Santiago. Materiales y métodos: Se seleccionaron por conveniencia 100 pares de modelos según los criterios de inclusión y exclusión establecidos, correspondientes 50 al género femenino y 50 al masculino, y se realizó medición directa con un pie de metro manual, de la suma incisiva inferior y suma de segmentos canino-premolar. La medición fue realizada por dos examinadores previamente calibrados. Se determinó la exactitud de cada uno de los métodos y presencia de diferencias estadísticas significativas. Resultados: Para mujeres, Moyers 65% en maxilar superior y Moyers 50% en maxilar inferior presentan mayor exactitud en predicción de tamaño mesiodistal de caninos y premolares permanentes no erupcionados; en cambio, para hombres, Moyers 75% en maxilar superior y Moyers 65% en maxilar inferior son más exactos. El método de Tanaka-Johnston a pesar que solo presenta diferencias estadísticamente significativas en maxilar inferior en el género femenino (p<0,05), es menos exacto tendiendo a sobrestimar valores reales en mujeres, y a subestimar en hombres. Conclusión: Método de Moyers es más exacto en la predicción del espacio necesario en pacientes chilenos, su nivel de confianza varía según género y maxilar. Diferencias son explicadas por dimorfismo sexual y variaciones étnicas con respecto a la población de origen de métodos de predicción.
Objetive: Determine the accuracy of Tanaka-Johnston and Moyers indexes through the initial analysis of study models with permanent teeth of Chilean patients of the Graduate School Orthodontics of University Andres Bello in Santiago. Materials and Methods: 100 pairs of models were selected by convenience as the inclusion and exclusion criteria established, corresponding to 50 female and 50 male. Direct measurement was performed with a manual caliper gauge by two examiners previously calibrated. The sum of permanent mandibular incisors and sum of segments canine-premolar were measured. The accuracy of each of the present methods and statistical differences were determined. Results: In females, the prediction of width of unerupted canines and premolars is more accurate on maxilla with Moyers 65% and mandible with Moyers 50%. For males, Moyers 75% on maxilla and Moyers 65% in mandible are more accurate. Tanaka-Johnston method although only presented statistically significant differences in mandible of female gender (p <0.05), is less accurate tending to overestimate actual values in women as in men underestimated. Conclusion: Moyers method is more accurate in predicting space required in Chilean patients, the confidence level varies according to gender and jaw. Differences are explained by sexual dimorphism and ethnic variations from the source population of prediction methods.
RESUMO
Background and Aim: One of the important aspects of diagnosis and treatment planning in the mixed dentition is estimation of the size of unerupted permanent canines and premolars. One of the most commonly used the prediction methods are Tanaka and Johnston, which are based on data from a sample of Northern European descent children. The accuracy of this method when applied to a different ethnic population is questionable. The aim of this study was to determine the modified equations from Tanaka and Johnston for Iranian population. Materials and Methods: This study was an analytic and cross-sectional investigation with the randomized cluster sampling in Ahwaz. Fifty four students of 14-18 years age (32 girls, 22 boys) were selected between 320 students and plaster models of their maxillary and mandibular arches were prepared. Subjects had fully erupted teeth, class I canine and molar relationship and presented no proximal caries or fillings, morphological anomalies, missing teeth or occlusal abrasion, and bruxism. The mesiodistal crown diameters of the permanent teeth were measured with using the sharpened boley gauge (accuracy 0.01 mm). The data were analyzed by using the regression correlation analyses and t-test. Results: The size of permanent canines and premolars were larger in maxilla than mandible and males than females. These values in Iran were different from other countries. Conclusion: In this study to predict the space (in mm) required for alignment of unerupted canine and premolars in Iranian children, halve the sum of mesiodistal dimension of the four mandibular incisors and add the respective constants 10.5 for upper jaw and 10 for lower jaw.