Corrilation study between true horizontal plan, common horizontal andvertical parameters

Using intra cranial reference lines is inherently unreliable for assessment of anterior-posterior jaw relationships. However, they are being widely used for cephalometric evaluation and diagnosis and treatment planning of orthodontic patient. The aim of this study was to evaluate the correlation of the TH/AB and TH-Wits to the common horizontal and vertical analyses.

This cross sectional descriptive study was conducted with 40 adults (20 male, 20 female) who were between 18-24 years-old and had no history of craniofacial disorders. Lateral cephalometries were taken for all patients, using Natural Head Position (NHP). All the cephalograms were taken by the same radiologist and were traced by same person. Two orthodontists approved the results and the kappa statistics was calculated to determin intra-examiner agreement level. Pearson correlation coefficient value was determined between TH-Wits, TH/AB and horizontal parameters (Wits, Harvold, Wylie, APP-BPP, and ANB angle) and vertical parameters (Sn-GoGn, S-Go/N-Gn, TH-GoGn and sum of posterior angles). The correlation analysis was used in order to determine the relationship between these parameters.

The results revealed that the highest correlation in horizontal direction was observed between TH-Wits, TH/AB; and ANB (0.73) and APP-BPP (0.68 & 0.61). In vertical direction, the highest correlation was demonstrated between TH-Wits, TH/AB; and sum of posterior angles (0.75 & 0.35).

In using TH-Wits and TH/AB, the effect of changes in vertical dimension and the lack of significant correlation between these parameters and linear horizontal analysis should be considered.