Impression Techniques

Otoscopic Examination

Before making an impression, the patient's ear must be thoroughly examined and determined to be acceptable for the process. The exam not only allows you an overall view of the health of the ear, but also can reveal contraindications to impression making such as:

  • Impacted earwax
  • Fluid discharge
  • Bony growths (Exostosis)
  • Inflammatory conditions
  • Prolapsed canal
  • Perforated eardrum
  • Foreign objects
  • Enlarged canal
  • Thick hair growth
  • Cauliflower ear
  • Swimmer's ear
  • Surgical ear

Oto-Dam Placement

Proper oto-dam placement is critical to providing for the safety of your patient and ensuring a successful earpiece impression. The primary acoustic seal is established in the ear canal and is complicated by the fact that the ear canal actually changes dimension with jaw movement.

Use the otoscopic examination to gauge the size of the oto-dam you will use for your patient. An oto-dam with too small of a diameter allows the impression material to flow beyond the oto-dam and impinge on the eardrum. Too large of an oto-dam prevents proper placement in the ear canal at a depth required for a good impression. It can also cause discomfort for your patient. Apply Oto-Ease® lubricant to the oto-dam to make insertion easier and more comfortable. If the size you have chosen for the oto-dam does not seal the ear canal, remove it and try a different size.

Once you have selected the proper size, use the tip of the earlite to place the oto-dam into the ear canal and to make any slight adjustments. Use the otoscope to verify that the oto-dam is placed properly in the ear canal, checking to see that it is in full contact with the entire canal wall.

Earlite Use

The earlite serves as an aid in oto-dam placement. When using earlites and otoscopes, it is always important to hold the tool properly and to use proper bracing.

Caution:Proper bracing of the hand and tools being used is of paramount importance to the safety of the patient. During the impression process, some patients may experience a cough or gag reflex. This is a normal response due to stimulation of the vagus nerve. To avoid injury, always brace your hand to the patient's head by using your little finger. This will keep the tool in the same relative location to the ear in the event the patient coughs, jerks or moves suddenly.

Open Versus Closed Jaw Impressions

There has been much debate regarding open versus closed jaw impression techniques. Here at Westone, we believe that a jaw movement impression works well for vented hearing-amplification fittings. Bite-block/open jaw impressions should be taken for hearing protection products, musicians' products, and whenever acoustic feedback is the primary concern.

Impressing the Ear

Using the proper bracing technique, place the end of the mixing tip or syringe approximately 1/4 inch (6 mm) inside the ear canal opening. Gently begin to express the impression material into the ear canal, allowing the material to flow back over the syringe or mixing tip. Once the material starts to flow past the tip, start backing the tip out of the ear canal. It is critical that you fill all the landmarks in the ear. For instance, fill the concha bowl, move up into the antihelix crevice, then follow the contour of the ear, finishing at the center of the concha.

After about 4 to 5 minutes, check to see if the impression has cured. Press a fingernail or earlite tip gently into the material to see if an indentation remains. If there is no indentation and the material is not tacky, the impression is cured. It is then safe to remove.

Removing the Impression

The removal string or vent tube of the oto-dam should not be used as a handle to aid in removal of the impression. Instead, gently pull the patient's pinna up and back to break the seal. Remove the impression from the antihelix area and gently rotate forward and out. Should the oto-dam remain in the ear canal, the removal string or vent tube can be used to remove it.

Examine the ear for any material remaining from the impression process. Some slight redness may be evident and is normal. In the rare case that any impression material remains and cannot be easily removed, refer the patient to the appropriate medical authority for treatment.

Note:Prior to sending the patient home, inspect the impression to make sure that the necessary canal length and all anatomical landmarks are present.
How to SPLEAD

"Spleading" is a technique for mixing ear impression materials that reduces the chance of contamination. We've found that products containing sulphur−often found in latex gloves and hand lotions− can react with vinylpolysiloxane impression materials, preventing proper setup. Spleading is recommended for Silicone Singles and other silicone materials. All you need is our SPLEAD pad, metal spatula, silicone syringe …and our great impression material.

Easy Steps for Spleading:

Figure 1

Figure 2

Figure 3

Figure 4
Figure 5 Figure 6
Open the Silicone Singles packet. Use a metal spatula to remove the materials (Figure 1) and place them on the SPLEAD pad (Figure 2).

Mix the two materials together by blending them with the spatula, like artists mix paints (Figure 3). Don't touch the materials with your hands! Continue mixing until the material is a uniform color (Figure 4).

To load the silicone syringe, remove the plunger and place the chamber of the syringe on the SPLEAD pad at a slight angle (Figure 5). Using the syringe chamber like a cookie cutter, press down on the material, progressively scooping up the material until all of it is loaded in the syringe (Figure 6). Put the plunger back into the syringe to complete the loading process. Tear off and discard the top sheet of the SPLEAD pad before mixing the next packet.