About Impressions

The ear impression is the blueprint from which any custom-fit product will be produced; the finished product can only be as good as the impression. Any deficiencies in the impression will greatly affect the patient’s satisfaction and use of the finished earpiece. The impression materials listed below are formulated by Westone to be the finest available to our industry and when used according to proper practices and procedures will help you provide the best impression possible for your patient.

For years, we’ve made what our customers regard as the finest silicone ear impression material on the market. Today our material is formulated to reveal every detail and feature of the ear, and provide the best possible blueprint for any of our custom-fit products. They’re still pink, and as always, the best impression material money can buy.

Impression Materials

Numerous tools and techniques have been used throughout the years to make impressions of the human ear. Recent advances in materials and procedures have led to the most consistent, dimensionally stable, and easy-to-use impression materials and delivery systems to date. Even so, only strict attention to the manufacturer’s instructions will ensure the best impressions possible.

There are three primary families of impression material available: two-part vinylpolysiloxane, addition-cure silicone, and methyl methacrylate polymer and monomer (powder and liquid).

Vinylpolysiloxane

The latest advancement in impression material is available as individual portion packs, in specially formulated cartridges, or in bulk containers. Vinylpolysiloxane is the most popular impression material in use today. Westone offers three dierent vinylpolysiloxane products to meet your needs:

Silicone Singles® are available as pre-measured units, making them extremely easy and convenient to use.

SiliClone® and SiliClone FIRM Cartridges are conveniently packaged for use with manual or electric impression guns. When propelled through the special mixing tip, the two-part material is automatically mixed to the proper consistency.

Silicast® is a two-part material packaged in bulk containers. Accurate measurement of the material is ensured by using the two different color-specic scoops provided.

Silicone Singles and Silicast can be mixed either by "Spleading" or by hand.

To mix using the "Spleading" technique, use a metal spatula or similar tool and a SPLEAD pad. Mix the materials as quickly as possible until the material is a uniform color then load the syringe and make the impression. It is very important not to deviate from the manufacturer’s instructions.

To mix by hand, thoroughly wash your hands, and then combine the material for 20 to 30 seconds or until the material is a uniform color. Work as quickly as possible to mix the material, load the syringe, and make the impression.

All vinylpolysiloxane impression materials provide accurate and dimensionally stable ear impressions.

Addition-Cure Silicone

Blue Silicast® is a base and catalyst material that consists of a base putty and a tube of hardener. A scoop is provided for ease of measuring. Blue Silicast can be mixed either by “Spleading” or by hand. As with any impression material, it is very important not to deviate from the manufacturer’s instructions.

To use the "Spleading" technique, fill the scoop with impression material. Flatten the impression material onto the SPLEAD pad and add the catalyst. Thoroughly mix the material until it’s uniform in color. Once the two components come into contact with one another, the curing process has begun. Work as quickly as possible to mix the material, load the syringe, and make the impression.

To mix by hand, thoroughly wash your hands and then fill the scoop with the recommended amount of impression material. Flatten the impression material in the palm of your hand and add catalyst. Mix the material for 20 to 30 seconds or until the material is a uniform color. While it may be tempting to speed up the cure of the impression material by using a little extra catalyst, the minute that may be saved in cure time is not worth the risk of a possible ill-fitting earpiece. Remember that once the two components have come into contact with one another, the curing process has begun. Work as quickly as possible to mix the material, load the syringe, and make the impression.

Once the impression has cured, it is dimensionally stable. Place the impression in the mailing box along with the order form and ship.

Powder and Liquid

Westone's BLEND® impression material has been available for several decades and can produce an accurate impression.

When using powder and liquid impression material, remember:

Always use pre-measured material. A slight change in the ratio of liquid to powder can produce an impression that is either too wet, which can lead to drooping, or too dry, which can cause, overexpansion of the ear canal.

Always put the liquid into the mixing-bowl first, followed by the powder. A glass mixing bowl and metal spatula are a must. Paper cups and tongue depressors absorb liquid, thereby altering the critical ratio of powder to liquid.

The curing process starts as soon as the powder and liquid come into contact. It is imperative that you work quickly while mixing the material and loading the impression syringe.

Powder and liquid impressions are susceptible to damage during shipping. As such, they need to be carefully packaged to avoid distortion. Secure the impression to the bottom of the shipping box with an adhesive, such as Duco® Household cement, and keep the order form from contacting the cured impression.

Impression Tools

Oto-Dams

All oto-dams work on the same basic principle. An oto-dam is manufactured to a specifyc diameter from a material that has an inherent resistance to reduction in diameter. As the oto-dam is placed in an ear, it is compressed by the canal walls. The resistance of the oto-dam to this compression, or what is called “radial pressure”, holds the oto-dam in place against the force of the impression material. The two types of oto-dams in common use today are vented and non-vented.

Vented Oto-Dams

With any conventional oto-dam (foam or cotton), once the impression material has made full contact with the ear canal wall, any air trapped behind the dam is forced to compress against the eardrum. This sensation of ear “fullness” can range from minimal to signifycant discomfort. A vented foam oto-dam allows for the equalization of air pressure within the ear during the impression making, curing, and removal process, which can significantly reduce discomfort.

Non-Vented Foam Oto-Dams

Non-vented foam oto-dams are available in a wide variety of sizes and are soft, comfortable, and easy to use. Size selection is the most common challenge in using a foam oto-dam. Be sure to choose the appropriate size for your patient, using visual inspection to ensure that it fits snugly in the ear canal.

Non-Vented Cotton Oto-Dams

Non-vented cotton oto-dams are soft, comfortable, and function well. However, because of the manufacturing process, many cotton oto-dams are supplied as hard, compressed wads, so be sure to fluff the cotton oto-dam before use. The softer, more pliable the oto-dam, the more effectively and comfortably it will seal off the ear canal.

Impression Syringes

Historically, the syringe method has been used to take impressions of the human ear, offering clean, quick, and precise control of the impression material as it enters the patient's ear. Syringes are available in several designs to work with specific impression materials.

Impression Guns

Manual or electric impression guns effectively eliminate the guesswork associated with the mixing of materials by using use of dual-chamber cartridges and special mixing tips. The precise amounts of “A” and “B” components, propelled through the tip, insure proper mixing prior to delivery into the ear.

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 also reveal concerns or contraindications to impression making such as:

  • Impacted cerumen (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

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.

Oto-Dam Placement

Proper oto-dam placement is critical to providing for the safety of your patient and ensuring a successful ear 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 a diameter allows the impression material to flow beyond the oto-dam and impinge on the eardrum. An oto-dam with too large a diameter prevents proper placement in the ear canal at the depth required for a good impression. It can also cause discomfort for your patient. 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.

Open Versus Closed Jaw Impressions

There has been much debate regarding open versus closed jaw impression techniques. 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 ll all the landmarks in the ear. For instance, fill the concha bowl, move up into the antihelix crevice, and then follow the contour of the ear, finishing at the center of the concha.

After about 3 to 5 minutes, check to see if the impression has cured. Press an 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.