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Hot Summers, or Thoughts on Ear Impression Technique

Hot Summers, or Thoughts on Ear Impression Technique
Chester Pirzanski, BSc, Pete Russell
July 11, 2000

Hi guys! Summer's here, the beer is cold. Better still, the weekend is just ahead. Well then, why is it all so boring?

Aliens haven't invaded Earth (yet). Not even one flying saucer has been spotted! There are no new scandals in Hollywood to chat about! Even worse, there is no fun in hearing aid fittings any more...most of the aids fit right away; snugly, comfortably, and without feedback. It is so boring! Where is the challenge in that?

The new modification station you bought just sits there, eagerly waiting for you to grind and buff. Where are the good times when stock earmolds had to be modified for each patient fitting? Do you think you will ever get the chance to use the station and the shiny burrs? Remember how patients just loved your triumphant appearance from the lab with sweat beads on your forehead and the freshly polished earmold in your hand? And oh, the adrenaline rush you used to get when the hearing aid finally stopped screaming with feedback. When was the last time that happened? Can you remember?

Good news! You can still have tons of fun with earmold fittings if you follow our guidelines on how to mess-up impression taking and earmold ordering. We guarantee it! Just do this....

How to mess-up ear impressions (and hearing aids, and patients):

  • Never conduct an otoscopic examination of the patient's ear. Assume that all ears are very much the same. If the ear has abnormalities, don't worry. Remember, you have the new modification station and you can do magic.

  • While taking an ear impression always select the largest otoblock you have. The larger the better. It will certainly stop the syringed silicone from going too far. Impressions that show only the first ear anatomical bend are just fine with most earmold labs. They love to guess where the eardrum is. Believe that! If you do not have a block large enough, use the smallest. The impression looks so comical when the silicone escapes past the block! Of course, patients just adore that happy, tickling feeling of that little protrusion of silicone rubbing against their eardrums. Even better -- don't use an otoblock at all and jam the silicone into the ear with your thumb. Have fun!

  • It's best not to bother with the yucky hand-mixed silicones that stick to your hands. Make the impression with a gun injected silicone, there's no mess and the silicone cures so fast! The best thing is the material is so light it will hardly stretch the tissue in the ear canal at all! Do not tell the lab you used a light silicone, let them guess! If they don't guess correctly the aid will be loose, will feedback and it may even fall out of the patient's ear. Doesn't the patient look hilarious pushing the aid in constantly? You know, if the aid is truly loose, you always can use your modification station to coat it with the sticky stuff for a better fit. Cosmetics? No problem. Just paint the earmold to make it more attractive looking. All earmold labs will be more than happy to send you tons of bottles and tubes with their best selection of lacquers!

  • Oh! How could we forget? One more secret; while the impression material cures in the ear the patient must chew! Never heard of feedback while chewing?
  • Anything else forgotten? Hmm? Think of using the liquid and powder impression material, but try this little hint ... Pour more liquid than recommended. Much more! The impression will sag and look very much as though it was taken from an armpit instead of an ear! But hey, nobody's perfect.
  • If you are not satisfied with the impression you just took, go ahead and build it up with some extra impression material. Make the canal long and stout. Don't worry about the earmold being too big; human ears are more pliable than you think.

So, the impression is finally taken and may go the lab. Is the fun over? Not necessarily. Here are some additional thoughts. We'll call these...

How to mess-up packaging and written instructions.

  • Never send one impression (or two) in one box. It is such a waste of space. Cram them in, jam them in, the more the better! If you ship enough liquid & powder impressions on a hot day like this, they will melt down and arrive at the earmold lab looking like one huge dinosaur's ear impression. Isn't this laughable? Please, do not mark the impressions with the patients' names. Can you imagine the fun the earmold lab technician will have trying to guess which one is which on a crowded workbench? And remember, if the earmold lab requests a new impression always tell them you already did your best or that the patient lives 200 miles away. If they insist on a new impression tell them if they don't rush, it will be a post mortem fitting. This will bring them to their knees!

  • The order form? Think of something creative. For small ears and a mild loss ask for 65 dB of gain -- just in case! The patient may actually need this much gain in twenty years. Why not make them happy now? Do not limit yourself regarding vents. Ask for a vent with a diameter larger than the canal itself. Nothing is too good for the patient. Remember, for best fittings, request all potentiometer controls and
all earmold options listed on the order form: a long canal, a soft coat, a seal ring, a full helix and a canal lock. The more the better! Remember, you have the station! Now, back to reality.

If you believe that nobody would take ear impressions and prescribe hearing aids like that, you'd be surprised!

To avoid most problems in hearing instrument fittings, as it pertains to the earmold or earshell fitting, we recommend the following:

Always start with a careful history, a thorough audiometric evaluation and a thorough otoscopic evaluation. If the patient has any of the signs or symptoms of ear disease (including aural pain, aural drainage, recent vertigo, tinnitus, previous ear surgery, recent changes in hearing, etc.) refer to a physician. Once we have established the patient is indeed an amplification candidate....

  • Place a correctly sized otoblock in the patient's ear canal just past the second canal bend. The impression material must fully imprint the shape of the patient's ear, including the ear canal medial bend. This will give the hearing instrument the correct sound direction.
  • Take all impressions employing a standard viscosity silicone impression material (as opposed to a soft/light viscosity silicone). This will give the earmold or earshell a more secure and comfortable fit and will enhance the instrument's acoustic seal. Follow the manufacturer's directions exactly regarding mixing and set-up times.

  • Always take open-jaw impressions with a mouth prop inserted at the corner of the patient's jaw. This will prevent acoustic feedback with mandibular movements and the likelihood of retention problems.

  • Inspect the impression to ensure that the size and shape of the concha and canal can accommodate the options that you prescribe.

  • And one more small thing: Send your impressions to an earmold lab with reliable otoplastic work! Regardless of the type of hearing aid technology you prescribe, proper fit of the earshell or earmold is critical to the optimum performance of the aid, and maximizes hearing aid benefit for the patient.
Have a great summer!

You can find more information on ear impressions in publications listed below:
  1. Anatomically accurate ear impressions. Pirzanski, C. Audecibel, 1999, 1-2

  2. An alternative impression-taking technique: the open-jaw impression. Pirzanski, C. The Hearing Journal, 1996;11

  3. Critical factors in taking an anatomically accurate impression. Pirzanski, C. The Hearing Journal, 1997;10

  4. In taking ear impressions, longer is better. Pirzanski, C. The Hearing Journal, 1997;7

  5. The anatomy of perfect ear impression. Pirzanski, C. The Hearing Review, 1998;12

  6. Tips for hearing aid fittings and remakes. Pirzanski, C. The Hearing Review, 1998;1

  7. Electroacoustic modification strategies for feedback management. Russell, P. & Coutinho, J. Communique, 2000 14(1) 18
Sennheiser Hearing - June 2024

Chester Pirzanski, BSc

Pete Russell

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