IHS Earmold and Impression Techniques 5 — Questions and Answers
Question 1: Which earmold material is most appropriate for a patient with a known sensitivity to acrylic resins?
- Hard polymethyl methacrylate (PMMA) acrylic
- Polyvinyl chloride (PVC) earmold material
- Medical-grade silicone (Correct answer)
- Lucite or similar acrylic copolymer
Correct answer: Medical-grade silicone
Medical-grade silicone is hypoallergenic and the preferred alternative for patients who experience allergic reactions to acrylic-based earmold materials.
Question 2: When measuring the depth of otoblock placement, a standard guideline for adults is to position the otoblock approximately:
- At the entrance of the ear canal (first bend)
- 2–5 mm past the second bend of the ear canal (Correct answer)
- Directly against the tympanic membrane
- At the level of the isthmus only
Correct answer: 2–5 mm past the second bend of the ear canal
Placing the otoblock 2–5 mm past the second bend ensures the impression captures enough canal length for a deep canal fit while maintaining a safe distance from the tympanic membrane.
Question 3: A patient's earmold feels loose after six months of use even though it fit well initially. The most likely cause is:
- The earmold material absorbed moisture and expanded
- Natural changes in ear canal shape due to aging or weight change (Correct answer)
- Over-polishing of the earmold surface by the patient
- The tubing has become too stiff, pulling the earmold out of position
Correct answer: Natural changes in ear canal shape due to aging or weight change
The shape of the ear canal changes gradually due to factors such as aging, significant weight loss or gain, and skin changes, which can cause a previously well-fitting earmold to feel loose over time.
Question 4: Which type of vent has the greatest effect on reducing the occlusion effect while minimizing feedback risk?
- Select-a-vent (SAV) with a large diameter insert
- A diagonal vent
- An external vent groove
- A pressure vent (pinhole vent) (Correct answer)
Correct answer: A pressure vent (pinhole vent)
A pressure vent (pinhole vent, ~0.8 mm) is small enough to reduce feedback risk but still allows canal pressure equalization, providing occlusion relief without compromising acoustic seal significantly.
Question 5: The 'canal' earmold style, compared to the 'half-shell,' provides which primary advantage?
- Better low-frequency retention
- Greater cosmetic appeal due to a smaller, less visible profile (Correct answer)
- Improved retention for patients with shallow concha bowls
- More surface area for volume control placement
Correct answer: Greater cosmetic appeal due to a smaller, less visible profile
The canal style sits entirely within the ear canal with minimal or no concha bowl portion, making it significantly less visible than larger styles like the half-shell.
Question 6: After removing an ear impression, the clinician notices the impression has a torn canal portion. This most likely occurred because:
- The material was over-mixed before injection
- The impression was removed before the material had fully set (Correct answer)
- The otoblock was positioned too shallowly
- Too much material was injected into the concha bowl
Correct answer: The impression was removed before the material had fully set
Removing an impression before complete polymerization results in the material tearing due to insufficient tensile strength, requiring the impression to be retaken.
Question 7: When ordering a replacement earmold for a patient, which information is essential to include to ensure acoustic continuity with the patient's current hearing aid programming?
- The patient's audiogram thresholds only
- Earmold style, material, vent size, tubing type, and acoustic bore specifications (Correct answer)
- The hearing aid serial number and manufacturer
- The date of the original earmold and the patient's age
Correct answer: Earmold style, material, vent size, tubing type, and acoustic bore specifications
The earmold's acoustic specifications (vent size, bore diameter, tubing type) directly affect the hearing aid's frequency response, so replicating these ensures the replacement performs consistently with the existing programming.
IHS Earmold and Impression Techniques 5
Which earmold material is most appropriate for a patient with a known sensitivity to acrylic resins?