Abstract
BackgroundA functional appliance is commonly used to optimize the development of the facial skeleton in the treatment of Class II malocclusion. Recent three-dimensional(3D) image-based analysis offers numerous advantages in quantitative measurement and visualization in orthodontics. The aim of this study was to localize in 3D the skeletal effect produced by the Herbst appliance on the mandible using the geometric morphometric technique.MethodsTwenty patients treated with a Herbst appliance and subsequent fixed appliances were included. Cone-beam computed tomography (CBCT) images were taken before treatment (T1), 8 weeks after Herbst appliance removal (T2), and after subsequent fixed appliance treatment (T3). Spatially dense morphometric techniques were used to establish the corresponding points of the mandible. The mandibular morphological changes from T1-T2, T2-T3, and T1-T3 were calculated for each patient by superimposing two mandibular models at two time points with robust Procrustes superimposition. These changes were then compared to the morphological changes estimated from normative mandibular growth curves over the same period. The proportion of cases exceeding the growth expression for controls was compared to a normal population using a one tailed binomial test.ResultsApproximately 1.5–2 mm greater condylar changes and 0.5 mm greater changes in the chin occurred from Tl to T2. This effect lasted until the completion of treatment (T1-T3), but there was no obvious skeletal effect during the orthodontic phase (T2-T3). Approximately 40–50% of the patient sample exceeded condylar growth by > 1.5 mm compared to untreated controls (p < .05). However, changes at the chin were not statistically significant.ConclusionsThe principal skeletal effect of Herbst appliance treatment was additional increase in condylar length for about half of the sample. This inconsistency may relate to the degree of mandibular growth suppression associated with a specific malocclusion.
Highlights
A functional appliance is commonly used to optimize the development of the facial skeleton in the treatment of Class II malocclusion
The purpose of this study is to assess the orthopedic effect of the Herbst appliance on the mandible in three dimensional (3D) using geometric morphometrics
[4] Phase 1 Herbst appliance treatment started near peak pubertal growth, which was defined as cervical vertebral maturation assessment (CVM) stage 3–4 [14]
Summary
A functional appliance is commonly used to optimize the development of the facial skeleton in the treatment of Class II malocclusion. The aim of this study was to localize in 3D the skeletal effect produced by the Herbst appliance on the mandible using the geometric morphometric technique. In the treatment of Class II malocclusion, an early phase functional appliance is commonly used for the correction of sagittal jaw discrepancies and to optimize the development of the facial skeleton [1, 2]. The classic removable orthodontic appliances require patient compliance so many practitioners prefer fixed functional options, such as the Herbst appliance. Mandibular jaw and muscle function may result in growth enhancement to correct the skeletal malocclusion [4]
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