Jaw Movement

Doggett Sheryl sdoggett at f1n06.kent.edu
Fri Oct 29 11:59:38 EST 1999


Jeff,

In the past I have minimized this problem by taking an impression with jaw
open.  First, however, check for earmold movement/displacement with jaw
displacement.  Next, with the earmold out, check to see if there is a
narrowing or collapse of the ear canal with jaw closed.  If that is the
case, a simple extension of the earmold tubing beyond the second bend will
alleviate this.  OTOH, if the earmold is being displaced with jaw
movement, then a style that decouples the upper conchal bowl from the
lower bowl should alleviate earmold displacement upon jaw movement.  

Hope this helps,

Sheryl



Jeffrey Sirianni (audioman at hctc.net) wrote:
: Case for Discussion:

: Patient is a 70+ year old male with steeply sloping HF SNHL (near normal at
: 500 Hz, moderate loss at 1000 Hz, severe by 2000 Hz).  He wears binaural
: BTE's (two channel WRDC) successfully.  He is a fairly sharp individual and
: so is his perception of sounds in his environment, and he seems to report
: such observations to me.

: He has experienced concha and EAC changes over the last three years which
: has caused unacceptable amounts of feedback, which were not present when
: initially fitted.  He also reported that when he opens his mouth, he seems
: to hear better with his aids.  Opening his mouth without the aids does not
: seem to create this phenomena, although with this amount of HF SNHL, I
: doubt he can detect any change, if present.  Examination of the EAC shows
: some movement when he opens and closes his mouth.  New earmolds were
: ordered with longer canals to try to minimize EAC changes with jaw
: movements and to reduce feedback.   Earmold impressions were taken while
: chewing gum.

: He says he still notices a change when he opens his mouth, and reports that
: the high frequency response (perception of HF) improves when his mouth is
: slightly open.  I really don't want to shorten these earmolds as I suspect
: that feedback will come back and I can't make the canal length long again
: once shortened.  I also predict that any changes in the EAC with jaw
: movement will still be present with a shortened canal.

: I think this is a case of explaining to the patient that by shortening the
: canal length of the earmold may or may not reduce this open jaw effect, but
: will definitely increase the chance of feedback, and that feedback control
: is more important than the slight high frequency drop when his mouth is
: closed.

: I would like to hear other opinions or recommendations from the group.  Am
: I missing something?

: Jeff




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--

sdoggett at .kent.edu





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