The Multiloop Edgewise Archwire Technique: Treatment Effects and Stability in Correction of Anterior Openbite

Abstract

Introduction: Anterior openbite (AOB) correction is a challenge to even the most skilled clinicians. Multiloop edgewise archwire (MEAW) therapy, developed in 1967 by Dr. YH Kim, is a fixed appliance technique proposed to treat moderate to severe AOBs without orthognathic surgery. Dr. Kim has reported that correction is accomplished by distal uprighting of the crowns of posterior teeth, along with extrusion and retraction of the incisors. However, his and other published studies on the technique are retrospective case series with inconsistent findings regarding the mechanisms of correction. This study incorporates a retrospective cohort design to investigate the dental and skeletal changes that occur with MEAW compared to conventional fixed appliances (FA), as well as to MEAW in conjunction with temporary anchorage devices (MEAW-TADS or TADs).Methods: Clinicians proficient in the MEAW technique contributed records for consecutively treated non-growing AOB patients. One group of subjects was treated by a clinician with the traditional MEAW technique, and another group of subjects, treated by another provider, consisted of patients treated with MEAW in conjunction with maxillary TADs. A matched control group consisted of AOB subjects treated by multiple providers using FA. Lateral cephalogram landmarks were identified and analyzed in order to compare initial characteristics and treatment changes in the three groups. The Photographic Openbite Severity Index was used to assess stability of treatment using intraoral frontal photographs. Linear regression was used to compare pre- and post-treatment values and changes between groups, and Fisher’s exact test and logistic regression were used to compare stability. Results: The MEAW and FA groups consisted of 33 subjects, while the MEAW-TADs group comprised 15 subjects. The mean pre-treatment (T1) ages were 29.5 years for MEAW, 32.4 years for FA, and 25.6 years for the MEAW-TADs group. The majority of the patients were female. The mean T1 openbite was 2.6 mm, 2.2 mm, and 5.4 mm for the MEAW, FA, and MEAW-TADs groups, respectively. Treatment success, as defined by positive overbite on the post-treatment (T2) lateral cephalogram, was achieved in 100% of MEAW, 97% of FA, and 93% of the MEAW-TADs sample. During treatment, upper and lower incisors extruded and retroclined in all groups, although lower incisor retroclination did not reach statistical significance in the FA group. Maxillary molar vertical position and anterior facial height were significantly decreased only in the MEAW-TADs group. In the MEAW and FA subjects only, mandibular first molars extruded significantly. Upper first molar angulation (U6-SN) showed significant distal crown tipping in the MEAW and MEAW-TADs groups. Lower first molar crowns exhibited distal tipping in all 3 groups. Follow-up photos were only available for a subset of the subjects, limiting the assessment of stability. Conclusions: The following conclusions can be made from this study: 1. Treatment success rates were high in all three treatment groups. 2. Incisors exhibited a pattern of extrusion and retroclination in all groups. 3. The dental and skeletal effects seen in the MEAW and FA groups were similar, except MEAW patients exhibited greater distal crown tipping of the first molars and more lower incisor extrusion. Molar vertical positions were minimally changed in the MEAW and FA groups. 4. Only the MEAW-TADs group demonstrated significant maxillary molar intrusion and reduction of AFH. This group also had significantly more upper incisor retraction than MEAW alone.