Abstract:

Objective To observe the distribution of gonion (Go) on the frontal photograph of the normal young adult,and to hypothesize a new facial reference line for locating gonion,and to provide the basis for studing the effect of orthodontic treatment on the frontal view of facial soft tissue.Methods 108 normal young adults were selected. Each subject was taken two frontal photographs under natural head position,such as a standardized one (A) and the other one with marked Go by facebow (B). The Zy-Me segment was used as a new reference line and the distribution of Go towards the Zy-Me segment was observed. The true value and calculated value of Zy-Zy/Go-Go were compared to prove the validity of the new method. The differences of Zy-Me and Zy-Zy/Go-Go between different genders were also analyzed.Results By making a perpendicular towards the Zy-Me segment via Go,it showed that the feet were located near the midpoint of the segment (50.31±2.21). The distribution of the frequency of Zy-H/Zy-Me followed the normal distribution (Normality=0.990). There were no significant differences between the true values and the calculated values of Zy-Zy/Go-Go (P>0.05, Cronbach's α coefficient > 0.9). There were no significant differences of Zy-H/Zy-Me and Zy-Zy/Go-Go of the objects between different genders(P>0.05).Conclusion On the frontal photograph of the normal young adults,the projected point of Go locates near the midpoint of the Zy-Me segment. The intersection of the facial contour and the perpendicular towards the midpoint of Zy-Me segment can be seen as Go in clinical trials.

Key words: frontal photograph, gonion, mandibular width, orthodontic treatment