RESUMO
INTRODUCTION: The Frankfort horizontal (FH) is a plane that intersects both porions and the left orbitale. However, other combinations of points have also been used to define this plane in 3-dimensional cephalometry. These variations are based on the hypothesis that they do not affect the cephalometric analysis. We investigated the validity of this hypothesis. METHODS: The material included cone-beam computed tomography data sets of 82 adult subjects with Class I molar relationship. A third-party method of cone-beam computed tomography-based 3-dimensional cephalometry was performed using 7 setups of the FH plane. Six lateral cephalometric hard tissue measurements relative to the FH plane were carried out for each setup. Measurement differences were calculated for each pair of setups of the FH plane. The number of occurrences of differences greater than the limits of agreement was counted for each of the 6 measurements. RESULTS: Only 3 of 21 pairs of setups had no occurrences for the 6 measurements. No measurement had no occurrences for the 21 pairs of setups. Setups based on left or right porion and both orbitales had the greatest number of occurrences for the 6 measurements. CONCLUSIONS: This investigation showed that significant and undesirable measurement differences can be produced by varying the definition of the FH plane.
Assuntos
Cefalometria/métodos , Tomografia Computadorizada de Feixe Cônico/métodos , Imageamento Tridimensional/métodos , Adolescente , Adulto , Pontos de Referência Anatômicos/diagnóstico por imagem , Pontos de Referência Anatômicos/patologia , Ossos Faciais/diagnóstico por imagem , Ossos Faciais/patologia , Feminino , Humanos , Masculino , Má Oclusão Classe I de Angle/diagnóstico por imagem , Má Oclusão Classe I de Angle/patologia , Mandíbula/diagnóstico por imagem , Mandíbula/patologia , Radiografia Dentária/métodos , Crânio/diagnóstico por imagem , Crânio/patologia , Adulto JovemRESUMO
PURPOSE: To develop a computer-based method for automating the repositioning of jaw segments in the skull during three-dimensional virtual treatment planning of orthognathic surgery. The method speeds up the planning phase of the orthognathic procedure, releasing surgeons from laborious and time-consuming tasks. MATERIALS AND METHODS: The method finds the optimal positions for the maxilla, mandibular body, and bony chin in the skull. Minimization of cephalometric differences between measured and standard values is considered. Cone-beam computed tomographic images acquired from four preoperative patients with skeletal malocclusion were used for evaluating the method. RESULTS: Dentofacial problems of the four patients were rectified, including skeletal malocclusion, facial asymmetry, and jaw discrepancies. CONCLUSIONS: The results show that the method is potentially able to be used in routine clinical practice as support for treatment-planning decisions in orthognathic surgery.