Morphospatial analysis of soft‐tissue profile in patients with Class II division 1 malocclusion treated using twin block appliances: geometric morphometrics[Note 1. To cite this article: Orthod. Craniofacial Res. 5, 2002; ...]

Author – Singh GD Objectives – To study soft‐tissue profile changes in patients treated with twin block appliances (TBA) for the correction of Class II division 1 malocclusion. The null hypothesis is that soft‐tissue profiles do not show any significant improvements associated with TBA treatment. Design – Longitudinal, retrospective. Setting and Sample Population – Scotland, UK, using lateral cephalographs of 46 consecutive, prepubertal children (aged 9–11 years) and 55 adolescents (aged 12–14 years) obtained from an orthodontic practice. Experimental Variable – The prepubertal children underwent ≈13 months of TBA treatment, while the adolescents underwent ≈22 months of treatment. Outcome Measures – Configurations of 13 digitized homologous landmarks of pre‐ and post‐treatment soft‐tissue facial profiles were compared using cephalometry, Euclidean distance matrix analysis (EDMA) and thin plate spline (TPS) analysis. Results – Cephalometry showed that height increases associated with the TBA were in the labiomental areas, and the most significant height decreases were seen in the lip regions. The results of EDMA also indicated significant changes ( P  < 0.05). The distance between the lips decreased by >5%, with increases in length in the labiomental region. The TPS analysis showed the soft‐tissues of the mandibular complex being displaced antero‐inferiorly, with anterior displacement of the landmarks of the lip region. These changes showed that the lips were brought into closer proximity with each other, permitting a functional oral seal. Moreover, the labiomental groove became less pronounced, reflecting the underlying dento‐alveolar correction. Conclusion – Demonstrable improvements in soft‐tissue facial profile may be associated with TBA treatment.