Abstract
Abstract Objectives The purpose of this study was to evaluate the effects of short-term expansion treatment using the quad-helix appliance on dentofacial morphology in orthodontic patients presenting with a hyperdivergent facial pattern. Methods The treatment group consisted of 40 patients with a hyperdivergent facial pattern, who were treated for maxillary incisor crowding with a quad-helix appliance during the mixed dentition period. Lateral cephalograms taken at the start (T0) and end (T1) of the treatment were obtained as a course of care. A similar number of patients, who possessed the same type of facial pattern and who remained untreated, were assigned to a control group. Two consecutive lateral cephalograms of each untreated patient were taken at the same time points as T0 and T1. All cephalograms were traced, analysed and compared between the two groups. Results The treatment changes as a result of the quad-helix appliance were expressed in an upward rotation of the mandible (2.34°) and distal tipping and impeded mesial movement of the maxillary first molars. Significant differences were evident between the treatment and control groups. Conclusion Quad-helix appliance treatment can be appropriate for significantly decreasing the mandibular plane angle in hyperdivergent patients presenting with moderate maxillary incisor crowding and a positive overjet and overbite.
Highlights
A quad-helix appliance may be used for correcting posterior crossbites[1,2,3] and reducing a tooth size-arch length discrepancy[4,5] during the mixed dentition
The cephalometric changes in dentofacial morphology that occurred during the T0 – T1 period were compared with those that occurred during a corresponding period in a control group of patients
The mandible rotated upward in the treatment group (2.01°) and downward in the control group (0.33°) with a statistically significant difference. This finding was previously reported by Cozza et al.,[11,12] Shundo et al.[4] and Mucedero et al.,[15] who showed the upward rotation of the mandible following the use of the quad-helix appliance
Summary
A quad-helix appliance may be used for correcting posterior crossbites[1,2,3] and reducing a tooth size-arch length discrepancy[4,5] during the mixed dentition. It has been reported that quad-helix treatment causes the maxillary first molars to tip and move buccally,[1,2,3] lingually[4] or distally,[4,5] and rotate mesiobuccally.[4,6] The distal tipping and mesiobuccal rotation of the molars can alter the occlusal relationships from Class II to a Class I.4. Several studies have shown that quad-helix treatment induces a downward movement of the maxilla, which secondarily produces a downward and backward rotation of the mandible and a subsequent increase in lower facial height.[7,8] Additional studies have determined that these results can be achieved by short-term rapid maxillary expansion treatment.[9,10] Significantly increased vertical dimension is often accompanied by sagittal and transverse discrepancies.[11] growing hyperdivergent patients with a maxillary transverse deficiency may be affected adversely in the vertical dimension by quad-helix treatment
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