Mechanism of Multi-loop Edgewise Archwire technique in correcting Class II anterior open bites with temporomandibular disorders – a retrospective cephalometric study in Chinese patients 

Abstract

Background: An anterior open bite is considered challenging to treat because of its multifactorial etiology. Condylar resorption, which is one of the temporomandibular disorders (TMD) symptoms, has been identified as an etiologic factor of anterior open bites. It is essential to find an effective and efficient method to correct open bites while reducing the risk of exacerbating TMD during orthodontic treatment.Objectives: To evaluate the effect of the multi-loop edgewise archwire (MEAW) technique in correcting anterior open bite in patients with TMD. Materials and Methods: In this retrospective study, 20 patients with anterior open bites and TMD were included. 19 cephalometric measurements and 2 open bite indices were evaluated. A paired t-test was used to assess changes between pre- and post-treatments. Results: There were statistically significant changes after the treatment using the MEAW technique. The cephalometric measurements, including vertical positions of the incisors and molars, changed significantly. The maxillary and mandibular regional superimpositions for a subgroup of non-extraction patients showed slight intrusion of the upper molars (-0.6±1.0mm, p=0.04) and slight extrusion of the lower molars (1.0±1.1mm, p<0.01). Open bite correction was achieved predominantly through retraction and extrusion of the upper and lower incisors. Conclusions: The MEAW technique can be an effective method in correcting anterior open bites in Class II patients with TMD. Anterior open bites were corrected mainly by extrusion and retraction of the anterior teeth. The vertical dimension was maintained for the upper molars, but the mandibular molars were extruded. During treatment, the patients who had TMD did not show evident recurrence or worsening of their TMD conditions, indicating that orthodontic treatment can be performed when required.