The effects of jaw motion on the ear canal
Abstract
Jaw-motion induces changes in the geometry of the external auditory meatus. These changes contribute to the problem of acoustic feedback in hearing aid use. They also can have an adverse effect on the accuracy of ear impressions from which earmolds are fabricated. It is possible to reveal these changes in geometry through careful measurement of ear impressions made while the jaw is held at different openings. Most hearing aid users are older and demonstrate decreased cellular and tissue structure surrounding the ear canal. The purpose of this study was to examine the effect of jaw position on the volume of the ear canal in the clinical population as a function of age. In addition, the use of dentures or braces, reports of TMJ symptoms and nonfunctional masticatory activities (parafunctional) such as teeth grinding, clenching, nail biting, pencil chewing, etc., as well as the number of teeth in an individual mouth were examined as predictors. Bilateral impressions were obtained with the jaw in the closed position and with the jaw in the open position from 102 individuals ranging in age from 22 to 81 years. The only significant predictor for ear canal changes with jaw position was parafunctional (p $<$.05). The number of teeth approached significance (p $<$ 10). No interaction effects were evidenced. Knowledge of potential change in ear canal geometry can predict the likelihood for acoustic feedback problems prior to the initial custom fitting. It also can assist the audiologist in the proper earmold or shell material selection to help prevent jaw-motion-induced acoustical feedback. In addition, knowledge of the dynamic ear canal characteristics will provide insight for the fitting of newly designed deep insertion and minimal contact hearing aids.
Degree
Ph.D.
Advisors
Goldstein, Purdue University.
Subject Area
Audiology|Dental care
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