Upper first molar rotation in normal occlusion and Angle’s class II division 1

Paulo Cesar Brandão NERY, Jurandir Antônio BARBOSA

The positioning of the upper 1st molar in the horizontal plane is important because its rotation can cause more or less space occupation in the arch. The research goals are: to determine the correct positioning of the upper 1st molar in Brazilian samples of untreated normal occlusion; to compare the results with values obtained through the literature revision, to determine the mean rotation of the upper 1st molar in Angle’s Class II division 1 malocclusions and to discover the incidence of the mesiolingual rotation in this malocclusion . The upper 1st molar rotation in cases of untreated normal occlusion and cases of Angle’s Class II division 1 malocclusion were evaluated through the mensuration, in models of plaster, of 2 different angles: the angle formed by the two lines passing through the tips of the buccal cusps of each molar, named angle 1; and the angle formed by the two lines passing through the tips of the mesiobuccal and mesiolingual cusps of each molar, named angle 2. In the sample of normal occlusion, the mean angle 1 was 24,5 degrees and the mean angle 2 was 126,4 degrees. In the sample of Angle Class II division 1 malocclusions, the mean angle 1 was 31,07 degrees and the mean angle 2 was 111,58 degrees. The sample of Angle Class II division 1 malocclusions shows the tendency of the upper 1st molars to be mesiolingually rotated by the analysis of the two proposed angles.

Keywords: Rotation. Upper 1st molar. Class II. Normal occlusion.

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