Module 6

Question 1

When are open-jaw impressions with a bite-block useful?

Answer 1

They’re useful when a tighter fit needs to be achieved because opening the jaw increases the height of the ear canal, allowing for more appropriate fittings when chewing, drinking, etc.

Question 2

What is viscosity and is lower or higher viscosity preferred?

Answer 2

-In reference to impression material, viscosity is the consistency of the material before it hardens in the process
·Low = soft/runny
·High = thick/dense/firmer
-Lower viscosity material is generally preferred. High viscosity material may be better for canals with hair or in open-jawed impressions

Question 3

What is shore value?

Answer 3

The hardness of the created earmold. Important for keeping shape and for shipping

Question 4

What is contraction ratio?

Answer 4

-How much does the impression shrink over time?
·Less than 3% is acceptable

Question 5

What is stress relaxation?

Answer 5

-Does the impression keep its shape after it is stretched or bent?
-Does it change when we physically pull the impression out of the ear?

Question 6

Describe condensation-cure silicone

Answer 6

-Consists of 2 parts: one part silicone base, and a tube of catalyst
-Material is mixed, and begins to harden within 20-30 seconds
-Medium to higher viscosity**
-Limited shelf life
-Not the most popular

Question 7

Describe addition-cure vinylpolysiloxane

Answer 7

-Impressions consists of 2 bases (2 different colours)
-Viscosity ranges: generally medium to high viscosity for hand mix and lower viscosity for cartridge mixes
-Material is mixed and hardens between 1-4 minutes (depending on hand mixed or cartridge material)

Question 8

Describe powder and liquid impression material

Answer 8

-Consists of 2 parts: powder and liquid
-Viscosity increases rapidly once the powder and liquid are mixed
-Not very popular today as these impressions have poor contraction ratio and stress relaxation

Question 9

Describe full shell earmolds

Answer 9

Full shell molds are most suitable for severe-profound losses & those who need added retention (*pediatrics)

Question 10

Describe skeleton earmolds

Answer 10

Skeleton earmolds are suitable for a wide range of losses/configurations, for those who need retention but have lesser degree of hearing loss, and for those who prefer a “less visible” mold

Question 11

Describe canal earmolds

Answer 11

Canal earmolds are suitable for mild to moderate losses (generally) & for those who want a discreet mold

Question 12

Describe acrylic/lucite earmold material

Answer 12

-Acrylic/lucite earmolds are hard material, durable, easily modified, easy to insert and remove, suitable for losses up to severe, hypoallergenic and ideal for soft-texture ears
-Not recommended for children due to hard material making an impact more harmful

Question 13

Describe silicone earmold material

Answer 13

-Silicone earmolds are soft material, more flexible, generally recommended for severe-profound losses, hypoallergenic, tubing must be attacked via a tubing lock, ideal for hard-texture ears, several options for pediatric patients (lots of colour/glitter variations)
-Not easily modified in clinic, colour changes over time

Question 14

Describe polyvinyl chloride/polyethylene earmold material

Answer 14

-PVC/polyethylene earmolds are in between in texture and softness
-Not recommended for those with vinyl allergies, not as easy to modify in clinic compared to acrylic

Question 15

What is tubing?

Answer 15

-It’s a tube that attaches to the earhook
-Tubing must be changed periodically as it is prone to harden over time, and shrink (which affects the frequency response)
-Tubing is fastened to the earmold by adhesive (lucite molds) or by tubing (soft/silicone, and PVC molds)

Question 16

What are dampers?

Answer 16

-Small material items that smooth the frequency response of the aid’s output by resisting acoustic energy
-The impedance of the damper is measured in ohms. The higher the number, the greater the impedance effect. The greatest impedance will occur with the damper nearer the ear hook outlet

Question 17

What do bores do?

Answer 17

The sound bore is the “tunnel” within the earmold which houses the tubing (different from vent)

Question 18

What do horns do?

Answer 18

-A “horned” tube or an “acoustic horn” is a physical way to boost high-frequency gain
-More popular before the development of digital programming that could achieve high-frequency gain

Question 19

Why is venting important?

Answer 19

-Venting allows air to flow through an earmold or custom earpiece, and serves a purpose:
·Bone-conducted, low-frequency sounds can escape (avoid occlusion effect)
·Allow for environmental, un-amplified sounds to reach the TM
·To relieve sensations of pressure
·To provide ventilation

Question 20

When do we not need to be concerned about occlusion?

Answer 20

-If someone has hearing thresholds higher than 50 dB HL in the low frequencies, then they should not experience the occlusion effect

Question 21

How do we choose an appropriate vent size?

Answer 21

Look at their hearing loss in the low frequency range. The more the loss, the smaller the vent size should be and vice versa

Question 22

T/F: custom earpieces attached to RIC devices also have venting and material consideration

Answer 22

TRUE