Taking Ear Impressions
Because 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 you make. Any deficiencies will greatly affect your patient's satisfaction with the finished product.
The procedures, techniques and processes discussed here are the culmination of years of experience in producing custom-fit products for the ear.
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 ensures the best impressions possible.
There are three primary families of impression material available: two-part vinylpolysiloxane, addition-cure silicone and ethyl methacrylate (powder and liquid)
Vinylpolysiloxane
The newest advancement in impression material is available in bulk containers, individual portion packs, or in specially formulated cartridges. Vinylpolysiloxane is now the most popular impression material in use today. Westone offers three different vinylpolysiloxane products to meet your needs:
Silicone Singles® (Silicast in single form) are available in premeasured units, making them extremely easy and convenient to use.
Silicast® comes in bulk containers with two different color scoops. It is important to accurately measure the two components to ensure proper curing.
SiliClone® and SiliClone FIRM are packaged in convenient cartridges for use with manual or electric impression guns. When propelled through the special mixing tip, they are automatically mixed and blended to the proper consistency. These are the easiest to use of all the vinylpolysiloxane products.
All vinylpolysiloxane impression materials provide accurate and dimensionally stable ear impressions. Once the impression has cured, simply place it in the mailing box along with the order form and ship.
Addition-Cure Silicone
Blue Silicast® can be mixed either by hand or using the "spleading" technique. As with powder and liquid impression material, it is very important not to deviate from the manufacturer's instructions. Blue Silicast is supplied in a tub with a tube of catalyst and a measuring scoop. Fill the scoop with the recommended amount of impression material. Flatten the impression material in the palm of your hand and add the appropriate amount of catalyst. Mix the material for 20 to 30 seconds or until the material is a consistent color. Remember to work as quickly as possible. 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.
As with the powder and liquid material, 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.
Powder and Liquid
Westone's BLEND® powder and liquid impression material has been available for several decades and produces a highly accurate impression. When using power and liquid impression materials, remember three things: First, 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 expansion of the ear canal. Second, 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 actually absorb liquid, thereby altering the critical ratio of powder to liquid. Finally, remember that 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.
