Effective temporomandibular joint growth changes after stepwise and maximum advancement with Twin Block appliance

BackgroundThis study was designed to evaluate the “effective” temporomandibular joint changes (the sum of condylar modeling, glenoid fossa modeling, and condylar position changes within the fossa) and their influence on mandibular rotation in Class II Division 1 malocclusion cases treated with Twin Block appliance using a maximum and stepwise advancement approach.MethodsSixty Class II Division 1 cases with normal growth patterns in the age group of 12 to 14 years were treated with the Twin Block appliance and randomly assigned to one of two groups: 1) maximum advancement (n = 30); and 2) stepwise advancement (n = 30). The Bolton Standards served as a control group. Lateral head films were obtained before treatment and after successful treatment (mean 1 year).ResultsCompared with the control groups, both treatment groups showed significant vertical growth changes. Sagittal growth direction was posterior with maximum advancement and anterior with stepwise advancement. Resultant mandibular rotation was in the anterior direction and was greater with stepwise advancement.ConclusionsMyofunctional therapy after maximum and stepwise advancement with the Twin Block appliance showed a favorable effect in the temporomandibular joint region. Stepwise advancement showed greater vertical growth and more favorable anteriorly directed horizontal growth in the temporomandibular joint region on a short-term basis.