Impression Techniques

Explain the procedure to your client.

The otoscope provides illumination and visual amplification of the ear.

1. Grasp the top of the ear with your thumb and index fingers ; press the remaining fingers against the head to control any sudden movements your client may make.
2. Carefully enter the ear canal with the specula portion of the otoscope whil pulling up on the ear (pull down for children) so that the ear canal and eardrum are clearly visible.

As you examine the client’s ear and canal the following information should be noted: the length and course of the canal, the overall volume of the concha and canal, the shape of the ear’s convolutions, and any problems that may exist.

Cerumen (Earwax)
If the earwax is impacted, the wax must be removed before taking an impression.

Discharge of fluid
This is usually caused by infection. Do not take an ear impression until the infection has cleared.

Prolapsed canal
A flap of skin will close the ear canal opening. Pulling the pinna up and out the flap of skin will usually open the canal.

Foreign objects
Pencil erasers or any other foreign objects must be removed before taking an impression.

Enlarged canal
This condition is usually due to surgery. Many times the eardrum will be completely missing or perforated. Have medical clearance before taking the impression.

Malformations
Some ears have moles, stenosis, warts, pimples, and various types of scar tissue or congenial deformities. If these are present, make sure your impression properly identifies them and alert the lab that this is a real anatomical variation and not an impression error.

Hair Growth
Hair growth at the opening of the canal should be trimmed away before taking an ear impression. Ear hair trimmers can be used to trim away excess hair.

1. Using your index finger and thumb grasp the auricle, bend forward, and then stretch slightly to check the ear’s elasticity. If the ear is difficult to move the texture is hard, if it moves and stretches easily the texture is soft.
2. Pull up on the ear to see how the ear canal opens. If there is little movement of the opening, the texture would be considered firm. If the the ear canal expands considerably from its relaxed position, the texture would be considered soft.

Note: This may be useful information particularly in narrow or prolapsed canals. Noting the ear,s texture is important when ordering an earmold.

A pre-tied foam or cotton block must be placed into the ear canal before injecting the impression material into the ear. The purpose of the block is to cushion the eardrum from the impression material, to make sure the impression material fills the ear canal completely, and as a safety device in the event of impression material dislodging into the ear canal after removal. There have been cases of prolapsed and surgical ear canals where this has happened. If the broken material does not extract by pulling the blockout of theearcanal by the block string, do not try to remove the material, refer your client to a medical professional to have it removed. Thus when choosing an impression material always follow the recommended mixing and setup directions, and make sure the impression material has a good tensile (tear) strength.

1. Start by placing the block at the opening of the ear canal using your fingers or tweezers. Hold the light probe as if you were holding a pen with your fingers near the illuminated probe tip. This will give you more control of the light while inserting the block.
2. Using your probe light in one hand and holding the patient’s head in the same manner discussed in the otoscopic examination, tap the block in small increments until the block is in place at or near the second bend of the ear canal. Do not drive the block into the canal. If you insert the block and itis hardly visible with the probe light you can be assure you are at the right depth.
3. If the block is hard to insert cut some of the block fibers or switch to a smaller block so it will move down the ear canal. If the block inserts too easily or if there are visible gaps around the block and the tissue of the canal use a larger block. You do not want the material to flow around the block.
4. If you are using a cotton block, lubricating the block with a substance such as Oto Slik™ or swett oil will allow the block to slide down the ear canal more easily. This will put the customer at ease and allow for easier removal of the impression. If you are using a foam block, it is important that the block is not compressed to tightly, as the block may slide or move from the foam expanding.

Once the impression material you have chosen is mixed, shape or scoop the material into the barrel of the syringe.

1. Before injecting the material into the ear, push the plunger forcing the material down the barrel until the material is 1/8” away from the tip of the nozzle of the syringe.
2. Place the nozzle of the syringe into the ear canal about ½” and slowly begin to inject into the canal. As the material begins to flow, slowly back the syringe out of the ear canal allowing the material to flow evenly with the tip of the syringe.
3. Work the material down to the anti-tragus notch, around the concha and up through the helix area. Fill the remaining portion of the ear making sure the tragus portion is completely filled. Always use a steady, constant flow of material into the ear. Removing the syringe too quickly or using stop and go motion can cause coiling or air gaps to the finished impressions. Use all of the material in the syringe.

NOTE: Do not try to stretch the material by attempting to shoot two ears with one barrel of material. Let the material set up the recommended time before removal. If you are not sure if the material is ready to remove, scratch the impression with your fingernail. If your nail leaves a line or mark, the impression is not ready to remove from the ear. When there is no mark, you then can proceed to remove the impression.

We want to remove the ear impression as quickly and painlessly as possible.

1. Press the outer edges of the pinna towards the patient’s head to break the material loose from the anti-tragus notch, concha, and helix area. With your index finger pull up on the helix area to dislodge the material from the helix fold. Work your way down in the same manner to the anti-tragus notch.
2. Grasp the anti-tragus notch area of the impression with your thumb and the helix portion with your index finger. In a single motion gently pull and slightly rotate the impression towards your patient’s nose until the impression is removed from the ear.

Due to characteristics of some ear canals, a vacuum may be created from the tip of the block to the eardrum making removal of the impression challenging. So as not to cause your patient any discomfort, have your patient open and close their jaw repeatedly while pulling the material from the ear canal. Once the seal is broken and air rushes in, the impression will easily be removed. You may use a vented ear dam to avoid this situation entirely.

A recent innovation in impression taking is the impression gun. There are two types of guns available:

Manual (caulking) type gun
Electronic device that dispenses the material effortlessly and evenly into the ear

The material that is used in the gun method is of low viscosity Vinyl Polysiloxane in a self-contained cartridge that is inserted into the dispensing gun. A mixing tip is locked into place over the cartridge that automatically mixes and dispenses the material when the trigger mechanism is depressed. Your hands never touch the material.

Insert the ear block as you would using the syringe method.

Place the mixing tip 1/2″ down the ear canal and depress the trigger of the gun. The material will flow and mix itself through the cartridge. Since the material used in the cartridge gun system is of low viscosity, the material will not flow as quickly as it would in the syringe method.

It is important to be patient and allow the material to flow from the mixing tip. Removing the mixing tip too quickly from the flow of the material will create gaps or under fills in the impression.

Removal is the same as discussed in the syringe method.