An Observational Study on Morphological Changes in the Ear Canal According to Jaw Movement

Abstract

Background/Objectives: Useful technical details for manufacturing in-the-ear (ITE) hearing aids were obtained by analyzing morphological changes in the ear canal according to jaw movement.

Methods/Statistical analysis: The deviation between the cross-sectional area and the shape surface of the ear canal was analyzed by matching and aligning 3D scanned ear impressions for each condition, and the geometric accuracy was compared by the average mean (Avg error) and root mean square deviation (RMS error).

Findings: The cross-sectional area in the longitudinal direction of the ear canal was 1^st bend 2.7%, mid 4.2%, 2^nd bend 4.5%, and end 6.2%, indicating more change toward the eardrum. The degree of change could not be specified because it varied by measurement point and individual, but the maximum difference between closed and open conditions was 1.75mm in surface coordinates and 12.5mm² in cross-sectional area.

Improvements/Applications: Acquiring ear impressions is significant because morphological changes in the ear canal increase when manufacturing invisible-in-canal (IIC) and completely-in-canal (CIC) hearing aid shells sitting deep inside the ear.