475 CLINICAL RESEARCH Volume 32, Number 6, 2019 Correspondence to: Prof Duygu Karakis Department of Prosthodontics Faculty of Dentistry, Gazi University Bis ¸kek Caddesi 1. Sokak No: 4 06510 Emek, Ankara, Turkey Fax: 90 312 2239226 Email: dtduygukc@hotmail.com; duygukoc@gazi.edu.tr Submitted November 27, 2018; accepted June 21, 2019. ©2019 by Quintessence Publishing Co Inc. I nternal derangement of the temporomandibular joint (TMJ) has been defned as an abnormal relationship between the articular disc and the mandibular condyle, fossa, and articular eminence. 1,2 Clinical signs vary from functional disc displacement to disc dislocation with/without reduction. 2 In the early phase of internal derangement of the TMJ, the articular disc becomes displaced from its original position, and the posterior border of the disc undergoes a movement to anterior of the condylar head. The disc remains in this position as long as the mouth is closed. While the mouth is opening, the disc is re-situated on the condylar head. The movement of the disc onto and off of the condylar head may result in a clicking (single or reciprocal) sound heard by the patient and/or by the clinician. 2 If this condition persists, another stage of derangement is noted; ie, the rubbing of the degenerated joint surfaces against each other makes a crepitation sound. 3 The etiology of internal derangements is mul- tifactorial, and common symptoms such as pain in the TMJ, restriction in mandibular functional motion, and joint noises motivate the patient to seek treatment. 4 Over the years, TMJ sounds have received increasing attention as an important physical sign of joint dysfunction and/or pathology. 5,6 The main drawback related to the pathology of sounds is the diffculty in making accurate comparisons between dif- ferent observers. 5,7,8 Routine recording and measuring of TMJ sounds are carried out Purpose: To determine the effectiveness of anterior repositioning splint (ARS) therapy on elimination of temporomandibular joint (TMJ) sounds in patients with internal derangement. Materials and Methods: A total of 26 patients with 44 TMJs with internal derangement according to the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) were selected. These patients used an ARS for 6 weeks. The sounds of both the right and left TMJs were recorded with a specifcally developed sound recording system before and after ARS therapy. The evaluation of sound was performed using evolutionary spectral analysis on the program MATLAB. Parameters such as sound type, amplitude, duration, and energy were evaluated in a time-frequency analysis. Changes in mean amplitude levels of opening/closing TMJ sounds before therapy and 6 weeks after insertion of splints were compared using paired-samples t test. The level of signifcance was set at 5%. Results: The patients showed a decrease in the mean amplitude and energy values of opening/ closing sounds after 6 weeks of ARS use (P < .05). According to evolutionary spectral analysis, the use of ARS was effcient for 7 of 19 right joints (37%) and 11 of 25 left joints (44%). Conclusion: The results suggest that the use of 6-week ARS reduced amplitude and energy parameters of TMJ sounds; however, it did not completely eliminate TMJ sounds. Int J Prosthodont 2019;32:475–481. doi: 10.11607/ijp.6269 Evolutionary Spectral Analysis of Temporomandibular Joint Sounds Before and After Anterior Repositioning Splint Therapy in Patients with Internal Derangement Dilek Kaymak, PhD Oral and Dental Health Hospital, Ankara, Turkey. Duygu Karakis, DDS, PhD Arife Dogan, DDS, PhD Department of Prosthodontics, Faculty of Dentistry, Gazi University, Ankara, Turkey. © 2019 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.