Lecture 6 Flashcards
What is the occlusion effect?
- The increase the level of sounds in the low frequencies (greatest at 500 Hz and below) when the canal is occluded
- This increase can be between 20-30 dB in an occluded canal vs. “open” canal
- Sound is trapped in the canal and redirected to the TM
What does the occlusion effect result in?
Own voice sounds “loud”, “hollow”, “boomy”, chewing becomes aggravating
____ is the way to balance feedback and occlusion
Venting
What is one of the most important things with a HA?
- A Good Ear Impression
- The quality of the ear impression dictates the quality of the product created!
- An ear impression is a casting of the ear
What 4 materials are needed for ear impressions?
- A block to protect the TM (otoblock)
- Impression material (fills the ear canal)
- Syringe to put the material in the ear
- Or an all in one tool that loads the impression material into the ear for us
What are the 8 steps of taking ear impressions?
- Step 1: Hand washing/Infection Control, gathering of materials. Gloves are advised
- Step 2: Otoscopic examination, familiarizing yourself with individual characteristics of shape— be cautious of irregularities, seek medical clearance accordingly
- Step 3: Select a dam or “otoblock” that fills periphery of the canal — you are protecting the tympanic membrane!
- Step 4: Place the otoblock past the second bend using a lighted device such as a “penlight”. Have your patient seated comfortably. Recheck the placement of the otoblock (redo otoscopy)
- Step 5: Prepare the syringes. Prepare the impression material (mix by hand or with spatula). Fill the ear with material— the canal, the concha— the more “information” provided by the impression, the better
- Step 6: Once the material has hardened (indentation check), break the seal of the material to ear by moving the pinna “up” and “out”. Rotate the impression forward to remove from the ear
- Step 7: Examine the impression. Are there gaps? Is the otoblock attached to the material? Do you see the landmarks of the ear canal bends and concha?
- Step 8: Examine the ear. Ensure there is no impression material left behind, or significant irritation. Slight redness is normal.
What are some examples of what you may need medical clearance prior to taking impressions?
–active fluid discharge
–inflammation
–bony growths in ear canal/exostosis
–perforated eardrum
–previous surgery (e.g., mastoidectomy)
What do you need to get out of the ear before taking an impression?
Need wax out of the ear (can deform the impression and can be painful)
What is the most invasive/dangerous things we do?
Ear impressions are the most invasive and dangerous things we do (and cerumen management)
____ will stop bleeding in the ear canal
Nasal decongestant spray
Why do we want to place the otoblock past the second bend?
- Provide information on the length of the canal
- Where the sound port of the HA should be cosest to the TM
How do we know when the ear impression is set?
We know the ear impression is set when we can’t make a fingernail indent in it
When are deep impressions needed?
- Phonak Easy-View Otoblocks
- Ideal for IICs— when deeper impressions are required
- Placed into the ear with an otoscope
Why would you need to use an open-jaw impression marking?
- Open-jaw impressions with a bite-block can be useful when a tighter fit needs to be achieved.
- When you open your mouth, the ear canal opens and lengthens a little bit (this gives a tigther seal for when talking or chewing)
Why would you mark a horizontal impression on the earmold?
- Marking the impression of the horizontal place during the cure process can determine the position of the directional microphones in the manufacturing process
- Gives the manufacturer information on the specific angle of the patient
What are 4 components of impression material?
- Viscosity
- Shore value
- Contraction ratio
- Stress relaxation
What is viscosity?
- Viscosity (before its cured)
- 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
What do type of viscosity material should you use if an ear canal has a lot of hair?
When a canal has a lot of hair, low viscosity material can grab onto the hair, which can be difficult and painful (high viscosity material pushes the hair over instead of running over it)
What is shore value?
- Shore value (after its cured)
- Once the impression material parts have been mixed, an impression has been taken, and impressions form, its “hardness” has a particular shore value.
- Furthermore, shore value refers to the hardness of the created earmold
- This is important for keeping shape, and for shipping
Shore hardness scale picture
What level is impression material generally between?
Impression material is generally between 20-70 shore value
Hardness changes as the _____ value increases
Shore
What is contraction ratio?
- How much does the impression shrink over time?
- Less than 3% is acceptable
- How do you ensure an acceptable ratio? Mix material according to directions of the package
How long should impressions be kept in clinic?
Impressions should not be kept in clinic for more than a year
What is stress relaxation?
- 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?
What are 3 types of impression material?
- Condensation-cure silicone
- Addition-cure vinylpolysiloxane
- Powder and liquid
Explain condensation-cure silicone
- Impression material consisting of 2 parts: one part silicone base, and a tube of catalyst (to harden the material)
- Material is mixed, and begins to harden (usually within 20-30 seconds)
- Impressions are taken with all the aforementioned steps
- Generally, they are a medium to higher viscosity (putty like)
- Limited shelf life (has to be used up within a few months)
- Not the most popular
Explain addition-cure vinylpolysiloxane
- Impression material consisting of 2 parts: 2 bases (2 different colours); will know if it is mixed well
- Viscosity ranges: generally medium to high viscosity for hand mix material, lower viscosity for cartridge mixes
- Material is mixed, and begins to harden between 1-4 minutes
- Hand mixed material: 2-4 minutes generally
- Cartridge material: 1-2 minutes generally
- Impressions are taken with all the aforementioned steps
- Most popular
Explain powder and liquid
- Impression material consisting of 2 parts: powder and liquid
- Viscosity rapidly increases once the powder and liquid are mixed
- Not very popular today as these impression have generally poor contraction ratio and stress relaxation, effected by temperature, and they are considered easily damaged when shipping
- These are for skilled clinicians that can make a mold on site
What are 3 earmold styles?
- Full shell
- Skeleton
- Canal