Angles of facial convexity in different skeletal Classes

Abstract

The objective of this study was to investigate whether it is possible to use a lateral (profile) photograph to determine the underlying skeletal Class and which reference points of the angle of convexity are most suitable for this purpose. Profile photographs and lateral cephalographs included in the baseline data for 180 orthodontic patients were retrospectively evaluated. The subjects were assigned to skeletal Classes based on Wits values obtained by radiolographic analysis. The Class I subjects were 58 patients (22 males, 36 females) with an average age of 13.63 +/- 2.1 years, the Class II subjects 60 patients (37 males, 23 females) with an average age of 13.60 +/- 2.6 years, and the Class III subjects 62 patients (28 males, 34 females) with an average age of 11.65 +/- 3.3 years. The angles measured were A'OrB' (=POrA'-POrA'), A'N'B', and the angle of convexity with its variants (N'SnPog', N'A'Pog', TrSnPog', TrA'Pog', Gl'SnPog', and Gl'A'Pog'). These angles were statistically evaluated using a two-sided t-test and linear discriminant analysis. Class II and Class III subjects exhibited highly significant differences (P < 0.001) for all angles. Class I and Class III exhibited highly significant differences (P < 0.001) for almost all angles, and significant differences for A'N'B' (P < 0.05). Class I and Class II differed significantly (P < 0.05) only for some angles (N'SnPog', TrA'Pog', Gl'SnPog', and Gl'A'Pog'). The error within the linear discriminant analysis was smallest for N'SnPog', GlA'Pog', and TrA'Pog' angles. However, the method error according to Dahlberg yielded rather high values for all angles (1.07-1.17 degrees). Discrimination between skeletal Class I and Class III was easier than that between Class I and Class II. One of the reasons may be that the subclasses division I and division II were not distinguished within the Class II subjects.

Correlation between occlusal abnormalities and parameters investigated by three-dimensional facial photography

“…The same authors observed smaller angles for the total face angle (GL-SN-POG) in Class II than in Class I patients, which is in contrast to a reverse observation reported by Ferrario et al 16 Our results did not reveal any significant differences in total face angle for Class II children. In accordance with the findings of Godt et al, 7 however, we did notice higher values (to some extent significantly higher values) for this angle in the Class III patients than in the control group. The values those authors obtained with 95% confidence intervals (173.99u to 176.99u) were very similar to our mean values with standard deviations (168.7u to 175.2u).…”

“…These questions have not been resolved previously. 5 A number of authors [6][7][8][9][10] did find an association between soft tissue and underlying bone/tooth structures, concluding that information about skeletal and dental abnormalities can be derived from soft tissue architecture. The fact, however, that these studies primarily refer to adults illustrates that pertinent data about younger patients remain to be collected.…”

Augmentation of linear facial anthropometrics through modern morphometrics: a facial convexity example

“…Godt et al 7 determined that the convexity angle most suitable for determining skeletal class was the angle subtended by Nasion-Subnasale-Pogonion N'SnPog' landmarks, as defined by Zylinski et al 1 and illustrated in Fig 1. This angle lies in the mid-sagittal plane, excludes the nose and provides an anterior-posterior assessment of the maxilla and the mandible. Manual indication of the angle was originally performed on lateral photographs 7 that provide a silhouette of the apparent midline.…”

“…Manual indication of the angle was originally performed on lateral photographs 7 that provide a silhouette of the apparent midline. However, with the advent of 3-D imaging, the midline has to be determined from the 3-D manifold.…”

“…Furthermore, new and alternative measurements on 3-D facial imaging, facilitating an efficient means to extract facial anthropometrics, are an active topic of research. 6,7 The use of linear measurements to quantify form is commonly referred to as the conventional metrical ª 2011 Australian Dental Association 141…”