The purpose of this study was to find the characteristics of the frontal natural head position (NHP) of patients with facial asymmetry, and to contribute to the diagnosis of facial asymmetry in the clinical examination of %thodontic patients.
Twenty adult patients who had apparent facial asymmetry and no severe sagittal skeletal discrepancy were sdected as the asymmetry group, and 21 young adults who had symmetric faces were selected as the symmetry group.,Frontal cephalograms were obtained in the state of NHP using a pivot-mounted fluid level device. The 4 degree of the menton deviation was defined as the angle between the line drawn through crista galli and anterior nasal spine and the line drawn through crista galli and menton. The following angles were measured and each of them was compared with the degree of the menton deviation : one is the angle between the true vertical line and the supra-orbital line which is a tangent line to the extreme cranial point on the supra-orbital margin, and the other is the angle be=tween the true vertical he and the cervical line drawn through the midpoint of atlas and 4th cervical vertebra. Through the statistical analysis, following results were obtained.
1. The angle between the supra-orbital line and the true vertical line was much more deviated from the right angle in the asymmetry group than in the symmetry group.
2. The angle between the cervical line and the true vertical !me in the asymmetry group showed greater tendency than in the symmetry group, but the difference was not statistically significant.
3. In the asymmetry group, the degree of the menton deviation was positively correlated with the angle between the supra-orbital line and the true vertical line.
The above results suggest that facial asymmetry patients show the tendency to have the tilted NHP to eanpensate the deviation of menton position.
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