Cephalometric study to test the reliability of anteroposterior skeletal discrepancy indicators using the twin block appliance.

Background: The objectives of this study were to check the reliability of the five angular and two linear parameters for sagittal maxillo-mandibular discrepancy and to compare and correlate angular parameters with the ANB angle, and the linear parameter with Wits analysis.

Methods: The pre-treatment and post-functional lateral cephalograms of 25 subjects (17 males, 8 females) with class II division 1 malocclusion treated with twin block functional appliance were selected. Five angular (ANB, β angle, APDI, YEN angle, W angle) and two linear (Wits analysis, App-Bpp) parameters were traced on both sets of cephalograms. Paired Student's t-test, one-way ANOVA, post hoc test, and Karl Pearson correlation statistical analysis were performed.

Results: All the parameters considered in our study showed highly significant difference in pre-treatment and post-functional values, suggesting their reliability (p < 0.0001). When ANB angle was compared with the other angular parameters, a highly significant change in the mean value of the difference in pre-treatment (T1) and post-functional (T2) values was noted (p < 0.001). No significant change was seen when comparing the mean value of the difference in T1 and T2 between linear parameters (p = 0.949).

Conclusions: All the parameters used in the study can be reliably used to assess anteroposterior skeletal discrepancy. Whenever limitations of the ANB angle and Wits analysis are foreseen, the W angle and App-Bpp, respectively, can be reliably used. The YEN angle may reliably predict the post-functional change with the use of twin block appliance.