IADR Abstract Archives
Evaluating Craniofacial Asymmetry in Class III Subjects Using Different Methodologies
Objectives: Accurate assessment of craniofacial asymmetry is the key to aesthetic surgical outcomes, yet no study has reported a conclusive method that quantifies the craniofacial asymmetry precisely. This study intends to evaluate the outcomes of corrective surgical treatment for craniofacial asymmetry using four different methods with an aim to arise with a best technique for craniofacial asymmetry assessment.
Methods: CBCT images of twenty-one Class III subjects with surgically corrected craniofacial asymmetry and twenty-one matched controls were analysed. 27 hard tissue landmarks were identified on 3-dimensional (3D) reconstructed models using 3D Slicer software. Craniofacial asymmetry was quantified using following methodologies: asymmetry index (AI), asymmetry scores based on clinically derived midline (CM), Procrustes alignment, and modified Procrustes (MP). AIs were calculated based on Cartesian distances of the landmarks from the mid-sagittal plane (MSP), while Euclidean distances between the landmark pairs yielded asymmetry scores.
Results: Pre-surgery asymmetry was detected comprehensively by AI when compared with controls. Similar results were observed with CM and MP methods that revealed severe asymmetry at the mandibular regions. Conversely, Procrustes was unable to identify asymmetry as effectively as other three methods. On comparing post-surgical results, Procrustes showed increased mean scores specifically at mandibular bilateral (2.02 ± 0.87mm to 2.12 ± 0.45mm) and ramus regions (1.96 ± 0.86mm to 2.23 ± 0.48mm) as compared to other methods, which was inexplicable. Besides, significant residual asymmetry was observed in the mandible using AI, CM and MP methods (chin, p = 0.02), while Procrustes failed to detect any residual asymmetry.
Conclusions: Procrustes was not a valid method for craniofacial asymmetry measurement, while AI and CM methods were more reliable given the MSP is stable. Our MP was MSP independent and showed some promising results which were comparable to AI and CM, therefore a more viable option for craniofacial asymmetry assessment.
Methods: CBCT images of twenty-one Class III subjects with surgically corrected craniofacial asymmetry and twenty-one matched controls were analysed. 27 hard tissue landmarks were identified on 3-dimensional (3D) reconstructed models using 3D Slicer software. Craniofacial asymmetry was quantified using following methodologies: asymmetry index (AI), asymmetry scores based on clinically derived midline (CM), Procrustes alignment, and modified Procrustes (MP). AIs were calculated based on Cartesian distances of the landmarks from the mid-sagittal plane (MSP), while Euclidean distances between the landmark pairs yielded asymmetry scores.
Results: Pre-surgery asymmetry was detected comprehensively by AI when compared with controls. Similar results were observed with CM and MP methods that revealed severe asymmetry at the mandibular regions. Conversely, Procrustes was unable to identify asymmetry as effectively as other three methods. On comparing post-surgical results, Procrustes showed increased mean scores specifically at mandibular bilateral (2.02 ± 0.87mm to 2.12 ± 0.45mm) and ramus regions (1.96 ± 0.86mm to 2.23 ± 0.48mm) as compared to other methods, which was inexplicable. Besides, significant residual asymmetry was observed in the mandible using AI, CM and MP methods (chin, p = 0.02), while Procrustes failed to detect any residual asymmetry.
Conclusions: Procrustes was not a valid method for craniofacial asymmetry measurement, while AI and CM methods were more reliable given the MSP is stable. Our MP was MSP independent and showed some promising results which were comparable to AI and CM, therefore a more viable option for craniofacial asymmetry assessment.