Prediction of transverse maxillary dimension using orthodontic models

The main objective of this study was to quantify the transverse maxillary dimensions using orthodontic cast models of individuals with natural normal occlusion. Sixty-eight pairs of orthodontic models were evaluated with the respective posteroanterior radiographies of white adults (38 women and 30 men; mean age, 17 years and 5 months). The models were placed in Class I molar occlusion, and on each pair, 4 points were marked on the alveolar buccal ridge (2 on the premolar region and 2 on the molar), determining the upper and lower transverse interpremolar and intermolar dimensions. The variables analyzed in the 3 measurements, obtained from the cephalometric radiographies and the cast models, showed no statistical differences. The upper intermolar distance was 57.20 +/- 2.60 mm; the lower intermolar, 55.16 +/- 2.40 mm; the upper interpremolar, 42.17 +/- 2.19 mm, and the lower interpremolar; 39.67 +/- 1.77 mm. On the posteroanterior cephalograms, the maxillary width was 65.97 +/- 3.42 mm and the mandibular width was 87.92 +/- 4.60 mm. There was intraresearcher and interresearcher correlation. There was no sexual dimorphism. The method proposed in this study can predict the transverse maxillary dimension, applying the formula ym = 8.62 + 0.88xm (ym = expected upper intermolar distance, xm = lower intermolar distance) for the molar region, and ypm = 4.87 + 0.94xpm (ypm = expected upper interpremolar distance, xpm = lower interpremolar distance) for the premolar region.