ABSTRACT
Objective: To investigate whether the application of thyroid collars (TCs) affects the results of cephalometric study. Study Design: The Steiner cephalometric analysis of the patients was performed using lateral cephalometric radiographs, which were taken twice for each patient: Once using TCs (TC group; n0 = 50) and once without using TCs (NTC group; n = 50). A randomized and observer-blinded diagnostic study with head films taken from the two aforementioned groups was performed and results were evaluated with the t-test and Z-test, using GraphPad® Prism 4 software. Results : Statistical analysis using t-test was performed. The values of the line angles used in Steiner cephalometric analysis were compared for which values of each angle remained unchanged when done using TCs and without TC to the same samples. Conclusions : Lead shielding of the thyroid gland does not affect landmark identification or the specific measurements of the angulations traced during cephalometric analysis. TCs should be routinely applied during cephalometric radiography if cephalometric analyses are limited to the structures above the second cervical vertebra.