A correlation between a new angle (S-Gn-Go angle) with the facial height

Abstract

ABSTRACT
Background: Y-axis has been used by many authors as a growth parameter while horizontal growth of mandible is
outlined by moving forward along the Go-Gn line. The purposes of this study were to introduce a new angle that
determine the vertical growth direction and establish its relation with the facial heights in different skeletal classes.
Materials and methods: The sample consisted of 146 digital true lateral cephalometric radiographs collected from
the files of the patients attending the Orthodontic clinic in the College of Dentistry, University of Baghdad. According
to the ANB angle, the sample was classified into: CL I (17 males and 21 females), CL II (30 males and 40 females) and
CL III (20 males and 18 females). 2 linear and 3 angular skeletal variables were measured using AutoCAD computer
program 2007. Descriptive statistics applied for all the measurements for both genders and total sample in each
class. Independent samples t-test was used to compare the measurements between both genders, while ANOVA
test was used to compare the measurements among the skeletal classes, and Pearson correlation coefficient was
applied to find the relation between the new angle and other variables.
Results: The mean values of S-Gn-Go angle were established and found to be higher in Class I then Class II and III;
also they were higher in males than females. This angle showed direct significant correlation with posterior facial
height in all of the skeletal classes.
Conclusions: Y-axis and S-Gn-Go angle is very important angles in determination the direction of mandibular growth.
Key words: Y-axis, S-Gn-Go angle, vertical growth. (J Bagh Coll Dentistry 2010;22(3):96-100).