Tau Angle: A New Approach for Assessment of True Sagittal Maxillomandibular Relationship

The orthodontic treatment planning relies on correct diagnosis of skeletal discrepancy, which demands accurate and precise cephalometric parameters. This study proposed an angle, which is based on unvarying cephalometric points and gives a true sagittal skeletal maxillomandibular relationship.

The present study was conducted on 279 individuals (13-30 years), which were divided into three groups (class I, II, and III skeletal malocclusion) depending on beta, wits, and ANB (A point, Nasion, B point) angles. Tau angle was measured, which lied at the junction of lines connecting the points T to G and G to M. ANOVA and the Dunnett T3 post hoc test were used to discern difference between three skeletal patterns. The gender difference in each skeletal pattern was found using the unpaired Student's t-test. Receiver-operating characteristic (ROC) curves determined the Tau angle's sensitivity and specificity to differentiate among skeletal patterns.

The Tau angle between 28° and 34° suggests a skeletal class I malocclusion; values below 28° show a class III skeletal pattern and above 34° suggest skeletal class II pattern.

Tau angle gives a true sagittal skeletal relationship, which depends on stable landmarks and is unaffected by rotation of jaws in vertical dimension due to growth or orthodontic therapy.

Tau angle provides a demarcation among three skeletal malocclusions, which can be an important tool for treatment planning in pediatric patients having both anteroposterior and vertical dentofacial discrepancies.

Gupta P, Singh N, Tripathi T, et al. Tau Angle: A New Approach for Assessment of True Sagittal Maxillomandibular Relationship. Int J Clin Pediatr Dent 2020;13(5):497-500.