UCSF

Introduction: Anterior open bite (AOB) is a type of malocclusion that exhibit no anterior guidance resulting in a lack of occlusal equilibrium in static and dynamic aspects, which could induce more stress for the temporomandibular joint (TMJ) than a normal occlusion. However, the effect of orthodontic treatment to obtain anterior guidance for patients with AOB on TMJ condyle remained poorly studied. This study aims to analyze the condylar changes in AOB patients by comparing their CBCT data pre- and post-orthodontic treatment.

Methods: The 108 AOB patients underwent orthodontic treatment included had cone-beam computed tomography (CBCT) scans taken before orthodontic (T1) and after orthodontic treatment (T2). We divided them into 3 different severity groups (Mild, Moderate, and Severe) and 3 different treatment modalities groups (ALN, FFA, and Sx). Measurements were conducted using InVivo 6 for the condylar joint space, depth of fossa, condylar position, and condylar dimension. Pre-treatment and post-treatment three-dimensional (3D) volume of bilateral condylar head were calculated, and the representative 3D models were superimposed using voxel-based registration on the mandibular stable region.

Results: After orthodontic treatment for AOB, the condyles tend to seat more posteriorly and superiorly for about 0.17-0.21mm and 0.09-0.12mm respectively; the depth of fossa increased 0.22mm on the right side; the asymmetry of the condylar position improved; the condylar width increased for 0.44mm; the condylar height increased for 0.40mm; and the 3D condylar volume increased for 98.29 mm3. Teenage AOB patients have significant condylar changes (joint space, laterolateral condylar position, height, width, and 3D volume) after treatment while adult patients generally do not experience many changes except for the surgical patients. As patient ages, the dimensional and volumetric changes after treatment decreased. Surgical patients experienced the most volumetric increase after treatment of AOB. There is no difference in the amount of condylar changes between AOB treatment with ALN and FFA.

Conclusions: Our results shows that orthodontic treatment for AOB overall does not predispose patients to the risk of condylar resorption or dysfunction. The joint space changes are small, however, the direction of these changes in teenage patients may warrant closer examination and consideration in treatment planning. As AOB patients age, the amount of condylar changes decrease with no much significant changes in adult non-surgical patients. Surgical AOB patients may experience more condylar positive remodeling after treatment compared to the non-surgical patients.