Abstract
Abstract Background A Class II malocclusion is the most frequent sagittal skeletal disharmony presenting for orthodontic treatment. A transverse interarch discrepancy (TID) may be considered as a possible functional cause of a Class II relationship. Objective The purpose of the present study was to determine transverse interarch width dimensions before and after orthodontic therapy and their possible relationship with increased mandibular projection following treatment. Methods The sample included 40 adolescent patients who were divided into two groups, one possessing and one without a transverse discrepancy. Interarch width differences (including ICWD, IPWD, IMWD, IAWD) were measured before and after treatment, and Pogonion (Pog) to Nasion (N) perpendicular was similarly measured in each group. Results The differences in arch and alveolar width dimensions between the two groups (including ICWD, IPWDI, IPWDII, IMWD, IAWD) before treatment were statistically significant (p < 0.05). A comparison of Pog to N perpendicular between the two groups showed that mandibular protrusion after treatment in the transverse discrepancy group was 2.6 ± 1.3 mm, while mandibular protrusion after treatment in the group without a transverse discrepancy was 0.6 ± 0.3 mm. The statistical comparison showed that the differences were significant (p < 0.01). Conclusion A transverse interarch discrepancy may have a functional relationship with mandible retrusion. If a transverse discrepancy is corrected via orthodontic treatment, the mandible may spontaneously protrude.
Highlights
A Class II malocclusion is the most frequently encountered sagittal skeletal disharmony.[1]
As a treatment goal is to obtain the maximum number of functional occlusal contacts, the presence of an initial transverse discrepancy between the dental arches induces a retruded position of the mandible and, clinically, a Class II malocclusion is established
Assessment methods advocated by Tollaro et al.[2] allowed for a quick and easy evaluation of a transverse discrepancy during the clinical examination, at least at the occlusal level, by having the Class II division 1 patient posture his or her mandible forward into a Class I relationship to identify a discrepancy
Summary
A Class II malocclusion is the most frequently encountered sagittal skeletal disharmony.[1]. A Class II relationship may be due to a micrognathic mandible in the absence of a primary transverse discrepancy. In these cases, a slight exaggeration of maxillary posterior buccal overjet caused by an anteroposterior jaw discrepancy is often clinically evident.[2]. A transverse interarch discrepancy (TID) may be considered as a possible functional cause of a Class II relationship. Objective: The purpose of the present study was to determine transverse interarch width dimensions before and after orthodontic therapy and their possible relationship with increased mandibular projection following treatment. Results: The differences in arch and alveolar width dimensions between the two groups (including ICWD, IPWDI, IPWDII, IMWD, IAWD) before treatment were statistically significant (p < 0.05). If a transverse discrepancy is corrected via orthodontic treatment, the mandible may spontaneously protrude. (Aust Orthod J 2016; 32: 148-154)
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