Abstract: Objective: This study was designed to evaluate the effect of temporomandibular joint (TMJ) bony ankylosis on Eustachian tube (ET) functions. Subjects and Methods: Twelve patients suffering from TMJ bony ankylosis were selected from those attending the out-patient Clinic of Oral and Maxillofacial Surgery Department, Faculty of Oral and Dental Medicine, Cairo University. Twelve subjects (control group) underwent Eustachian tube function test were selected also. Tympanometry was utilized to assess Eustachian tube function. Three pressure reading (P1, P2, and P3) of the middle ear and external ear canal volume were recorded by the use of tympanometry. Comparisons were performed between patient and control group to evaluate the change of pressure. Results: Throughout the results, four ears showed type (C) tympanogram representing Eustachian tube dysfunction, two ears showed type (B) tympanogram which represent otitis media with effusion. While other ears showed type (A) tympanogram. On comparing the pressure values between the patients and the control, significant decrease was recorded in (P2) value in the patients group and no significant difference existed in the external canal volume. Conclusions: The Eustachian tube function is affected in patients of temporomandibular joint bony ankylosis, it cannot adapt to changes in pressure effectively. Patients of TMJ ankylosis are more liable to develop otitis media. Inflation-deflation test is a reliable method for evaluating Eustachian tube function in patients of (TMJ) ankylosis. The external ear canal volume was not affected in this group of patients.Abstract: Objective: This study was designed to evaluate the effect of temporomandibular joint (TMJ) bony ankylosis on Eustachian tube (ET) functions. Subjects and Methods: Twelve patients suffering from TMJ bony ankylosis were selected from those attending the out-patient Clinic of Oral and Maxillofacial Surgery Department, Faculty of Oral and Dental Medici...Show More