Method: Patients treated with Herbst appliance (n=4, mean ages10.6 and 11.2 years, respectively before (T1) and at the end of active treatment (T2) were compared to a control group of untreated patients with Class II malocclusion (n=9, mean ages 9 and 10.6 years, respectively before (T1) and at the end of the observation period (T2). CBCT scans were acquired at T1 and T2, and 3D surface models that were constructed from the CBCTs were superimposed, using the cranial base of T1 as a reference. Treatment outcomes and growth changes were assessed using 3D surface distances, The ANCOVA statistical analysis considered the Expected Growth Unit (EGU) as a covariate, to test differences between treated and control group means were adjusted to take into account the expected effects of growth.
Result: Surface distance color maps revealed that downward and forward mandibular growth relative to the cranial base was observed for both groups in average. Quantification of the displacements of upper and lower incisors, anterior surface of the maxilla, inferior border of the mandible, chin, rami, condyles and articular fossa showed that only the anterior surface of the articular fossa presented significantly different (p<0.05) bone remodeling indicative of anterior relocation of the articular fossa in the treated compared to the control group.
Conclusion: This preliminary work indicates that bone displacements and remodeling that occur during treatment with Herbst appliance favor the correction of Class II malocclusion, and lead to an anterior relocation of the articular fossa.