Journal Article

RELIABILITY OF ORTHOPANTOMOGRAM IN DETERMINATION OF GONIAL ANGLE

Rasool, Ghulam, KHAN, M HASEEBULLAH, Bibi, Tayyaba

2017

Overview

Panoramic radiography was first introduced by Professor Yrjö Paatero in 1961.2 It provides invaluable information regarding teeth, their axial inclinations and stages of maturation and surrounding structures (e.g. TMJ).3-6 The introduction of radiographic cephalometrics in 1934 by Hofrath in Germany and Broadbent in the US provided both a research and clinical tool for the study of malocclusion and underlying skeletal discrepancy.1 The mandible is a key anatomical structure from both functional and aesthetic perspective.7 Implant studies on jaw rotations carried out in 1960 primarily by Bjork and coworkers revealed that mandibular rotation during growth results in individuals with various facial types including normal, short and long face.8 One of the most important cephalometric parameter giving an indication about the vertical growth pattern and symmetry of facial skeleton is gonial angle.9 Gonial angle on lateral cephalogram is measured by the intersection of tangent to the lower border of the mandible and posterior ramus.10,11 Due to double images of the lower border of mandible in lateral cephalogram, it is difficult to recognize and measure the gonial angle. Lateral cephalograms produce distorted image of the gonial angle and do not permit reliable measurement of the individual angle and is measured as an intermediate angle between right and left gonial angles.12 In orthopantomogram both borders of the mandible can be easily discerned without any superimposition and has been shown to be as accurate as lateral head films in measuring gonial angle.11 Several investigators compared the accuracy of OPG in determining the gonial angle and found that OPG is as reliable as lateral cephalogram in determining gonial angle.9,11,13,14 On the other hand, other studies proposed that OPG can provide information on the vertical aspect of craniofacial structure but they are not reliable enough to provide acceptably accurate additional information compared with lateral cephalograms.6,15 The aim of this study was to determine the reliability of orthopantomogram in evaluating gonial angle relative to lateral cephalogram. Gonial angle is measured as an intersection between two tangents i.e one tangent to the lower border of the mandible and another tangent to the posterior ramus.10,11 Lateral head films show superimposition of the image of the lower border of lower jaw which makes accurate measurement of the angle difficult.12 On the other hand, OPG provides a clearer image of the right and left sides of the mandible, hence providing convenient and accurate measurement of the GA.11 Gonial angle is an important radiographic parameter for vertical growth pattern and has been investigated for age and gender differences in studies.16 It has been reported to serve as an adjuvant forensic parameter and scientific growth scale.17 There are only a few studies on the use of panoramic radiographs for dentoskeletal features and focus mainly on intercondylar asymmetries and gonial angle measurements.14,20 Larheim and Svanaes14 found that horizontal measurements are not reliable with panoramic films; therefore only angular measurements were assessed in this study. CONCLUSION The conclusion of this study is: 1 Panoramic radiographs can be used to determine the vertical facial pattern with the same degree of accuracy as lateral head films. 2 There is a significant correlation between the values of gonial angle obtained from OPG and lateral cephalograms. 3 There is no difference between gonial angle of male and female subjects.

• Publisher: Knowledge Bylanes,Pakistan Oral & Dental Journal
• Subject: Age / Analysis / Asymmetry / Dentistry / Gender differences / Orthodontics / Orthopedic equipment and supplies / Radiography / Reliability / Statistical analysis / Values / Variance analysis