Comparison of measurements of cephaleometric roentgen films obtained by two different methods in skeletad class III patients

ABSTRACT The aim of this study was to compare the STCA (Soft Tissue Cephalometric Analysis) analysis -which evaluates the soft tissue besides dentoalveoiar structures- with measurements used in conventional cephalometric analyses on lateral cephalograms obtained by two different methods. This study also evaluates the similarity ratio of Wits measurement, which is a skeletal measurement, and Profile angle indicating the anteroposterior relationship of soft tissue structures on photgraphs in differential diagnosis of class III anomalies. The material consisted of radiographs obtained by STCA & conventional methods and profile photographs, obtained according to STCA method, of 28 patients. In the STCA method, the patients were positioned in natural head position, centric relation (upper most condyle position) and relaxed lip posture. Second method was the conventional method where the patients were positioned Frankfurt Horizontal Plane (FH) parallel to the floor, in centric occlusion and closed iip posture. Skeletal, dentoaiveolar and soft tissue measurements were done on each tracing by a software programme Por-Dios. Besides the conventional measurements, the parameters of STCA analysis and TVL (True Vertical Line) projections were used. Measurements done according to each method were compared statistically by student-f test. The Wits measurement used in anteroposterior evaluation of skeletal relations and the profile angle measured from profile photographs were compared and their similarity or difference in differential diagnosis of class III anomalies was evaluated. The overjet, overbite measurements, lower incisor NB line relationship, TVL projections and vertical measurements were found different when two groups were compared. The soft tissue measurements in the lower one third of the face showed significant differences between the two groups. The vertical soft tissue measurements were found greater in the STCA method. The Wits viimeasurement and the profile angle presented a simiarity ratio of %71.5 in diagnosis of class III cases. The findings of this study showed that the method in obtaining cephaiometric measurements greatly influenced soft tissue parameters. While evaluating the soft tissue, the cephaiometric method used in obtaining the radiographs should be considered. In Class III malocclusions both profile photographs and cephaiometric films must be used as diagnostic tools for diagnosis and treatment planning. Keywords: Centric relation, cephalometry, class III anomalies, lip posture, natural head position, soft tissue. viii