Reliability of beta angle in determination of sagittal skeletal discrepancy in class II patients
Keywords:
ANB, lateral cephalogram, sagittal dysplasiaAbstract
Introduction: The debate over an ideal variable to judge the anteroposterior discrepancy has continued over years. The objective of this study was to view the correlation between Beta angle and ANB and to assess whether Beta angle can be used as a guide to assess the severity of skeletal sagittal dysplasia in Class II subjects.
Material and Methods: 97 subjects with mean age of 16.49± 4.63, who presented to Orthodontics Department at Armed Forces Institute of Dentistry with CVM 4, skeletal Class II, having variations in vertical facial patterns and condyles visible clearly on digital radiographs were selected. The Beta angle and ANB were hand traced by four different post graduate trainees on lateral cephalograms and rechecked. Mean, SD, were calculated for age, SNA, SNB, ANB and Beta angles. ANB and Beta angles were evaluated by Pearson correlation test and cross-tabulation was done for the two variables.
Results: Means calculated for the variables were as follows: age was calculated to be 16.49±4.628, SNA 82.73±4.17, SNB 76.31±4.32, ANB 6.54±1.45 and Beta angle 25.86±4.44. Pearson correlation test showed a negative correlation of ANB to Beta angle of 1 to -0.361 showing that as ANB increased Beta angle decreased. Cross- tabulation was done for the two angles. For an ANB of 5°, beta angle ranged between 19° to 21°, for ANB angle 6 beta ranged between 20° to 30° so on and so forth till ANB of 10° for which beta angle ranged between 18°to 27°.
Conclusions: The results of this study confirms that there is a strong correlation between beta and ANB angle, however using beta angle as a guiding variable to determine the severity of sagittal skeletal dysplasia does not seem to be possible due to variations in the range of beta angle for a given value of ANB.