Correlation of Different Cephalometric Measurements

The aim of this study was to analyze a possible correlation of different cephalometric measurements to define facial type and to evaluate the best measurement for diagnosis. The sample consisted of 95 lateral cephalograms of caucasian patients with normal occlusion, aged between 15 years and two months and 2.1 years and four months, ofwhich 54 were male and 41 female. The faciaL types were divided into dolichofaciaL, mesofocial and brachyfacial, according to the standards stated by different authors, and a relationship among them was investigated using the Kappa and Total agreement methods. The highest agreement found was between FMA and SN GoGn; the Lowest was between SN Gn and VERT index. According to literature review and the interpretation of the results, SN GoGn appears to be the best measurement to define faciaL type. Key WOrth: Face; FaciaL bones; Cephalometry. ntroduction and literature Review Defining the facial cype of an individual is an essential key LO obtaining an accurate orthodontic diagnosis, and the lateral cephalometric x-ray is presented in literature as a relevant resource for this purpose. In orthodontics, professionals have several analyses tO assist in diagnosis, but sometimes more than one analysis becomes necessary to confirm an uncertain diagnosis, which can lead co misinterpretations. The studies of correlation among dilferenr cephalometric analyses that define facial cypes help orthodontic practitioners observe the many variations of these analyses, allowing them to decide the best measure tO more accurately define the diagnosis and treatment for their patients. In 1948, Downs, 1 in pursuit of determinant patterns between the teeth and alveolar process with the facial skeleton by means of a lateral radiograph, revealed the existence of a facial partern that represents an average of individuals with ideal occlusions. Riedel2 informed in studies about the importance of the angle between the cranium base (SN) at the base of the mandi~le (GoGo) to determine the aspects of current and future growth. For Tweed,3 the direction of facial growth is considered normal if the FMA (Frankfurt Mandibular Plane Angle) presents values between 20° and 30. 0 Later, Steine.-4 developed a cephalometric analysis adjusting the "Y"axis of Downs, thus defining the results of anterior and lower growth vector of the mandible by using the angle SN.Gn. An important method for qualifYing vertical facial pattern is Sassouni Archial analysis. lr dates from 1955, and the planes such author used were anterior cran ial base plane, occlusal plane and mand ibular base plane, which in a proportional face, would be located posteriorly, at a "0" point, defined by the author. The correlation between different measurements had already been studied,6 and it was found 66.67% of agreement berween the methods suggested by Rickercs and Siriwat-Jarabak, considered statistically significant, but only moderately so. In order to optimize working time, avoid errors in diagnosis and reduce the cost of the orthodon tic practitioner's work, this study aimed to investigate a possible correlation between different cephalometric measurements to define facial cypes, in addition ro researching the best variable to define facial cypes in a sample of Caucasian individuals with normal occlusion. Materials and Methods Sample The sample consisted of 95 lateral cephalomeu·ic x-rays of Caucasian subjectS with normal occlusion, aged from 15 years and 2 months to 2 1 years and 4 months, of which 54 (56.84%) were male and 4 1 (43.16%) female. All individuals had at lease four of the six keys of Andrews/ when analyzed in dental casts, and presented only permanem teeth, with the exception of third molars. The first key of Andrews7 was considered essential for the sample (Angle Molar Class I). Ethics approval was obtained after analysis from the Committee for Ethics in Research of che Methodist University of Sao Paulo (Brazil) . The protocol number is 245760-09 and dated March 30, 2009. Methods A lateral radiograph of each individual was taken using a Rotograph Plus""' (Rotograph Plus, Villa Sistemi Medicali S.p.A., Buccinasco, Italy) x-ray machine, operated by a single technician. The processing of radiographs was analyzed by a time/temperature method in an automatic processor, model130 Runzamatic (Eletro Medica Brasileira) maintaining the quality of chemicals used. The digitalization of the lateral radiographs was obtained with the use of an AMD""' (Advanced Micro Device, Sunnyvale, California, USA) computer with a 4C Hewlett Packard"' Scanjet 6100/CT (HewlettPackard Development Company, Palo Alco, CA, USA) scanner with 150 dpi resolution. The images were transferred ro the CeOC" computer program (Cefalometria Compuradorizada, COT Informatica LTDA, Sao Paulo, Brazil) which generated the requested cephalometric analysis. All linear and angular measures were automatically defined afrer the landmarks were made by a single investigator. Values were transferred to Microsoft Excel2000"' (Microsofr Corporation, USA) for statistical application. To determine the facial type of each subject, the classification suggested by Ricketts was used (VERT index), which separates the types into mesofacial, dolichofacial and brachyfacial. The measurements used are presented on Table 1. The sample was also separated in meso, dolicho and brachyfacial, following Tweed3, Steiner" and RiedeJ2 criteria. According co RiedeP, the standard is 32°, and rhe deviation is± 5°, what means that angles of27" to 37° determine mesofacial individuals. More than 3r indicates dolychofacial and less than 2r, brachyfacial. To Figure 1 -A-) Facial axis angle (Ricketts). B-) Mandibular plane angle (Ricketts) e C-) Lower face height (Ricketts). Figure 2 -A-) Facial angle or facial depth (Ricketts), B-) SN.GoGn (Riedel) and C-) Mandibular arch (Ricketts). Figure 3A-) FMA (Tweed) and B-)