3D assessment of mandibular skeletal effects produced by the Herbst appliance

Abstract

Background: A 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. Methods: Twenty patients treated with a Herbst appliance and subsequent fixed appliances were included. Conebeam 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. Results: Approximately 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. Conclusions: The 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.

Three-Dimensional Evaluation of Condyle-Glenoid Fossa Complex Following Treatment with Herbst Appliance

“…CBCT has not been frequently used in the evaluation of condylar response to functional orthopaedic therapy in patients with skeletal Class II malocclusion [ 23 , 24 ]. However, only recently, CBCT was used for the 3D assessment of mandibular and glenoid fossa changes [ 13 , 14 , 25 , 26 ]. It has been demonstrated that CBCT provides accurate and reliable linear measurement of the TMJ dimensions of dry human skulls.…”

“…It was found that Herbst appliance treatment stimulated the condylar growth in the vertical direction [ 32 ]. The three-dimensional evaluation of skeletal mandibular changes following Herbst appliance have also shown greater 3D superior and posterior condylar growth than in their control group, resulting in significant mandibular forward displacement without pitch [ 14 , 26 , 33 ]. In the evaluation of changes in condylar volume, an average increase of 297 mm 3 was reported in both the right and left condylar volumes in response to functional therapy with the twin block appliance [ 34 ].…”

Automated localization of mandibular landmarks in the construction of mandibular median sagittal plane

“…Using the robust Procrustes alignment algorithm, the pointwise surface-to-surface distance between the original and mirror models in 3D space was calculated, which was expressed as the overall asymmetry index (AI). The position and severity of mandibular asymmetry are shown by a color map in millimeters [ 4 , 13 ].…”

Three-dimensional spatial analysis of temporomandibular joint in adolescent Class II division 1 malocclusion patients: comparison of Twin-Block and clear functional aligner

“…The fibrocartilage covering its surface has strong remodeling and repair capacity, which provides a physiological basis for using functional orthodontic appliances to promote condylar growth and change the position of the mandible [38]. Fan et al analyzed the morphology of the condyle before and after treatment with functional orthodontic appliances in 20 adolescent patients with Class II malocclusion and found that the sagittal length of the condyle increased by 1.5-3.0 mm after treatment [39]. Wei et al also found that the use of functional orthodontic appliances in adolescent patients with Class II malocclusion resulted in the adaptive growth in the upper and posterior parts of the condyle [40].…”