The Tau Angle, Beta Angle, ANB Angle and Wits Appraisal in Assessing Sagittal Skeletal Relationship- A Cephalometric Study

The assessment of the sagittal skeletal relationship is critically important in orthodontic diagnosis and treatment planning. The Tau angle is used to assess the sagittal skeletal relationship which relies on stable craniofacial landmarks: points T, G, and M. This present study aims to evaluate the reliability of the Tau angle, Beta angle, ANB angle and Wit’s appraisal in assessment of anteroposterior jaw dysplasia thus in future the Tau angle would stand along with other novel sagittal relationship indicators. This study included pretreatment lateral cephalograms of 279 patients, age group 13- 30 years visiting our Department of Orthodontics and Dentofacial Orthopedics of a dental institution. They were grouped into skeletal class I, II and III mal-occlusion depending on Tau angle, Beta angle, ANB angle and Wit’s appraisal. One sample t- test used to determine the differences among the three skeletal patterns. In assessing sagittal relationship, skeletal class I malocclusion would have Tau angle 28 ̊- 34 ̊, Beta angle 27 ̊- 35 ̊, ANB 2=/-2 ̊, Wit’s- AO and BO coinciding in females, BO 1mm ahead of AO in males; Skeletal class II malocclusion would have Tau angle >34 ̊, Beta less than 27 ̊, ANB >4̊ ̊, Wit’s -AO leading BO in females, AO similar to or leading ahead of BO in males; skeletal class III malocclusion would have Tau angle less than 28 ̊, Beta angle < 35 ̊, ANB less than 1, Wit’s BO ahead of AO in females, BO ahead of AO greater than 1mm. The statistical analysis revealed no significant difference in the mean Tau, Beta, ANB angle and Wit’s appraisal values among three groups with those of standard reference values (p ≤ 0.05).