IDENTIFICATION OF THE TEMPOROMANDIBULAR-JOINT AND ADJACENT CEPHALOMETRIC LANDMARKS USING A DUAL SENSITIVITY SCREEN-CASSETTE SYSTEM

Objectives. Clinical evaluation of a cassette with dual speed screens for cephalometric radiography. Methods. Two lateral cephalometric radi ographs were taken on 20 consenting subjects using the TMJ Orthoceph S limline Cassette System (TOSCS), incorporating circular Trimax 12 scre ens in the area adjacent to the temporomandibular joint, and a control cassette (Trimax 8 screens). Ten pairs of radiographs with optimal im age quality were randomly presented to 10 observers trained in cephalo metric interpretation, Observers rated the overall diagnostic quality of each radiograph and of the TMJ region on an ordinal scale, They the n located specific landmarks and traced the TMJ anatomy using acetate overlays, Overlays were digitized by a single operator who repeated tr acing placements and digitizations to determine the error of recording method, Landmark variability was compared in the x- and y-axis by the Wilcoxon matched-pairs signed ranks test (p < 0.05). Six repeat traci ngs were performed and assessed by percentage of repeated observations above the maximum affordable error, Fossa space values were analyzed by the coefficient of variation (CV). The variability of the angular a nd linear values was also compared, Results. TOSCS image quality was p erceived as significantly better than the control, Method error was 0. 34 mm in the x-axis and 0.4 mm in the y-axis, Interobserver variabilit y was 2 to 3 times greater than intraobserver, There was less variabil ity with TOSCS for identification of basion (x-axis), center-of-rotati on (x-axis) and condyle (posterior) (x-axis), However, this was clinic ally insignificant, Accurate determination of the fossa space was not possible as CV varied from 23 to 84%. No differences in the variabilit y of angular or linear values variability were found. Conclusions. Whi le observers preferred TOSCS, no significant clinical differences coul d be demonstrated between the two systems. Copyright (C) 1996 Elsevier Science Ltd for IADMFR.