Ear Molds

Earmolds Manufacturing Processor:

Learning to make Earmolds:

  1. How to take Earmold impression quality
  2. What Earmold materials to take Earmold impression
  3. Explain how to select a perfect Earmold Style



To Knowing Earmolds:

An earmold is a custom fabricated device that channels the sound reproduced by a hearing aid through the ear canal. Since this is custom – made, we need to assess certain qualities by achieving specific objectives. There are four key factors to achieve a custom earmold’s objectives of delivering sound through the ear canal impression: quality earmold material selection, style selection, and earmold acoustics. We will cover the first three factors of this course, as earmold acoustics is perhaps an intermediate level course which would require a class of its own. What are these objectives and how do they compare to universal domes? The first objective would be to provide a satisfactory and proper acoustic seal.

Secondly, we need to have good retention on the pinna. Another goal is to acoustically modify the signal produced by the hearing aid. The comfort factor is critical because most users will wear their devices all day long. Finally, it has to have an acceptable appearance, many patients do not like to expose their hearing impairment, so aesthetics is vital. These objectives : seal, retention, acoustic comfort, and aesthetics are advantages of custom earmolds over universal ear domes.

Ear Impression For Earmold: Step-I

We start the process with an ear impression which involves specific requirements. In my experience, 50% of the success of a custom earmold is dependent on the quality of the impression. If we do not have a tough time producing a precise custom earmold. Most fit issues with earmolds can be eliminated by taking an accurate ear impression. Those issues, most commonly are seal, comfort, and retention.

Process To Take Ear Impression:

When we make an Ear impression, never rush the process. Investing an extra minute may yield a reliable and perfect result. Always keep the nozzle tip in the material throughout the process and never remove the nozzle from the material. As a quick review, the order of impressions begins with inserting the nozzle out of the ear, making sure that you cover the entire canal, and then going over the tragus. Capturing what tragus area is critical. Once the tragus is filled, you can move the nozzle towards the concha. Once the concha is filled, finish with helix dip. It is important on how clinicians fill this section with impression material. The first area of concern is canal length. The canal length has to be up to the second bent of the ear canal. The concha bowel crus of helix, and cymbals need to be adequately defined and filled. The tip of the helix is also an important area because this  provides excellent retention, we do not use the entire tragus, but for some production, but for some production concerns, we would like to have at least minimum, of ¾ of the tragal cartilage.



Earmold Material: Step-II

  Now we will discuss details for selecting the perfect earmold material for each patient. Let’s first consider the retention of an earmold. Our ears grow during the entire lifetime, and they never stop growing. As they grow, the pinna becomes softer, and retention issues may arise. Soft materials are recommended for a hard pinna and harder materials are recommended for a soft pinna. We recommended the softest materials for infants. For adults, a variety of earmold materials are appropriate for this age group. Seniors generally do well with harder material. When fitting custom earmolds on a pediatric patient, we need to consider certain factors: hygiene activities, insertion, and growth. Consider selection a material which is easy to clean .

Two types of Earmold Material is available in the market;-

  1. i) Consumable Earmold Material
  2. ii) Non-Consumable Earmold Material

 

Consumable Earmold Material: Consumable earmold material regular westage to make impression or manufacturing uses, and Non- consumable earmold material does not waste to make earmolds.

  1. i) Alginate powder (impression material)
  2. ii) Plaster of Paris (shaping powder)

iii) Melting wax       (layer material)

  1. iv) Acrylic powder and liquid (hard custom made material)
  2. v) Thread and cotton ( for eardrum safety )
  3. vi) Soft acrylic        (for soft earmold)

vii) silicone     (for soft earmold)

viii) vinyl soft and hard (for quality earmold)

  1. ix) Polyethylene Material

 

Non-Consumable Earmold Material: Non-consumable earmold material is available in the marketing as below:

  1. i) Grinding machine 
  2. ii) Drilling machine

iii) Burs 0.25mm to 5.00mm (for venting)

  1. iv) Stone and Rubber burs (for finishing of earmold)
  2. v) Rubber bowels (for material mixing)
  3. vi) Spatula  (to material mixing)

vii) Knife (for impression cutting)

viii) Syringe (to filling material into the concha)

  1. ix) Burnishers ( to  push the cotton ball into the ear canal)
  2. x) Pressure gaze Machine
  3. xi) Buffs

xii) Heating oven

 

We recommended polyethylene material, which is a very hard material when none of the soft materials can be used because of an allergic reaction. Typically polyethylene is chosen as a lost resort for its superior hypoallergenic properties. Keep in mind the child’s activities and comfort during extended use. Except for the summertime when schools are not in session, children tend to wear their hearing aids all day long. Insertion may be an issue for pediatricians especially if they have sharp bends to the ears canals. In that case perhaps you can use a harder material and not the softest. Other factors to improve ease of insertion is selecting a matter or silky surface. Harder materials are not ad pliable and will not be comfortable in the child’s ears as they grow. This is why we recommend softer materials for pediatrics. Children are very active and if their earmold is damaged a soft material will be safer in preventing further injury.

 

Soft vinyl: Soft vinyl is recommended for infants because it is soft and comfortable to insert into the ear canal. This material can be modified in your office if you have the right tools. More importantly, this material can be commented on, and you do not need to use a tubing anchor which may require a larger space. There are some disadvantages of  soft vinyl materials, as they are notorious for shrinkage. We do not recommend an earmold made of soft vinyl for more than 12 months.

 

Silicones: Silicone is the most popular material because of its versatility and desirable qualities. Custom earmolds made of silicone are comfortable, durable and do not shrink. During the production process the material sets and is cured. Silicones are known as hypoallergenic materials. Unfortunately, we have to use a tubing anchor or tube lock.

 

Platinum cure:This is the most popular silicone type. The hardness can vary anywhere from shore 25 to shore 60. In our industry, there are approximately ten different available  in this category and  multiple color options. The surface can be either glossy or matte and are known for their longevity.

 

Heat cure: Heat cure silicone is a better choice than platinum cure  when high precision is needed for intricate details. This is very important when it comes to power BTE hearing aids. Keep in mind that platinum cure silicones are not modifiable with simple office tools. Thus, Heat cure silicones may be a better choice. Heat cure silicones are typically semi-soft materials. Because of its high definition surface properties, it provides a superior seal over other silicone materials.

 

Hard Vinyl: This material is quite hard but becomes pliable when in contact with body heat. It takes approximately five minutes to become flexible onc in contact with heat, otherwise it’s a hard material. Hard vinyl is known for its hypoallergenic properties and can be cemented; custom earmolds made of hard vinyl are somewhat of a discrete solution. In our experience, this is a prevalent choice for senior citizens, especially when they want a smallest earmold that is less visible.

 

Acrylic: Custom earmolds made of acrylic materials are hard and hypoallergenic. The tube can be commented or glued. Typically they’re discrete because of their high transparency or translucency . The standard acrylic is a default custom earmold material ordered  through hearing aid manufacture, usually for RIC devices. There are two types of acrylic materials. One is a standard acrylic, and the other is a heat cure acrylic. You cannot tell the difference by just looking at it. The main difference is in regard to patients with allergic reactions you would specify heat cure acrylic when ordering. 

 

Polyethylene (PE): I briefly mentioned this material in the pediatric section. PE is also a hard material and is the most hypoallergenic material in the industry. Tubing needs to be commented with polyethylene custom earmolds. One issue with this material is that it is only available in opaque beige. Thus, making it an undesirable look and is typically used as a last resort for most of your allergic cases.

 

Combo Materials: Occasionally, two materials are combined to form the earmold to achieve the best custom earpiece for the patient. Typically, we would start with a hard material for concha and would use either soft, semi-soft, or sometimes pliable vinyl materials for the canal to provide a stronger. For some surgical ears, a hardened concha is used for secular retention and a soft canal for a stronger seal. An example for when a combo material is beneficial is with a patient who has a profound loss and a straight canal. With a straight canal, it is challenging to retain the earmold. The hard concha material would resolve our retention problem, whereas the soft canal portion will address the seal.

 

Combo Material:

  • Acrylic concha with soft vinyl canal,
  • Acrylic concha with hard vinyl canal,
  • Acrylic concha with semi-hard (hear cure) silicone,
  • Semi (soft heat cure) silicone concha with soft heat cure silicone


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Earmold Style: Step-III

Earmolds are available with a wide range of styles to address difficult physical challenges and acoustic requirements. There are two main types of earmold styles : Occluding and non-occluding.

 

Earmold Styles for BTEs: Occluding earmolds are designed to seal the ear canal completely This style of earmold is recommended for pediatrics and patients with a severe to profound Hearing Loss. Generally, all power behind the hearing aids will be coupled with an occluding earmold to obtain a good seal.

 

Canal size Earmold : Earmold styles, a canal size earmold is the most common style because it addresses the very characteristic of an occluding earmold which is sealing the ear canal. It is the least visible style. However, it lacks retention if you have a straight canal. A canal earmold retains well if your patient has sharp first and second bends. This style option is available in all materials. 

 

Shell Mold: An alternative to a canal style, if you have retention issues, is a shell mold. It provides the same seal as a canal and pushes the earmold into the patient’s ear. A full shell earmold may not be preferred for cosmetic reasons as it does take up the entire concha bowl. So what do we do  if we want to seal the ear canal but retention is an issue.

 

Canal-lok and canal-long lok Mold: A canal – lock mold may be a good choice in that case  because it fits similarly to a canal mold, but it also provides enough retention to stay in the ear. There are two types of canal-locks. Whenever, you are given only one choice for canal-lok, ask for an extended long-lok for improved retention. Typically that lock portion is not visible from outside the patient’s ear. This is the reason that it is chosen for aesthetic reasons. However, canal-lock may be tricky for first time users because it doesn’t have the full feature of the concha and helix.

 

¾ and ¼ Skeleton Earmold: If appearance is still a concern, consider fitting your patient with a  skeleton mold. The concha area is often in the center so it is going to be less visible than the full shell style. The regular skeleton style may be problematic for first time users who may have concerns about the appearance as they do not want to expose  their hearing loss. Thus a skeleton mold may be a beneficial option. If the mold is difficult to insert especially in the helix tip area, to address tip issues, you can ask for a reduced helix. The manufacturer will create  ¾ or ½  of a skeleton so that the helix area is completely removed.

 

Semi – Skeleton and canal lok w/ Helix mold: You will have a patient with a flat concha rim. This is more common than most providers would think, once you take the impression, inspect the concha portion to see if the rim is flat or “razor sharp.” when ordering the earmold, you can either especially a semi skeleton style or canal-lock with a helix. Both styles look quite similar to one other. Select the most appropriate style based on the location of the flat region on the concha rim. If you cannot decide, your earmold lap will select the proper style for you.

 

Canal-Shell (½shell  and ¾ shell) Mold: Another common issue is dexterity, typically due to insertion of the helix area. It may be easier to insert the canal portion, but positioning the helix. A canal-shell would be our recommended style. Alternatively, you can order a 3/4 shell.

Some patients may have TMJ or excessive mandibular action. The solution for this ordering a softer material and requesting the manufacturer to hollow out the canal portion.  H doing so, this will allow the TMJ movement and ensure the seal is never broken. Please keep in mind that this style is available in soft materials only.  We can hollow out the canal portion of a shell, half shell, or even skeleton earmold styles.

Excluding earmold styles are not just for regular BTE Hearing aids. They can be fit on RIC and slim tube hearing aids also. Custom earmolds are recommended for their secure fit because they offer significantly better retention over universal domes. Custom earmolds are more comfortable because they are made custom to each patient. You can fit any basic style and the only difference is the bore size is going to be specified for the manufacturer’s receiver or slim tube. 

 

Non-occluding earmold styles: Non-occluding ear molds feature a small outside diameter canal potion to allow amplified sound to  pass around the earmold as well as go through the tubing. This open  style offers the patient a more pleasing sound by providing an overlay of amplification on the natural hearing. They are also recommended for patients who have a chronic drainage problem since aeration of the canal is allowed. 

 

Cros Styles Earmold: These molds are designed for CROS and many IROS fittings. Typically, you would see a significant reduction in frequencies below 1000Hz. CROS ‘A’  is a canal style that is slightly longer in the lok portion for retention. CROS ‘A’ is made of hard materials only and has a minimum out diameter canal. CROS ‘B’ is similar to CROS ‘A’ but can be ordered in both hard and soft material. Instead of a canal-lock, we use a skeleton style. Typically the canal is shorter on CROS B mold. CROS C is similar to CROS B except that the canal comes with extended tubing. 

 

Advanced Design  For Free Field Molds: This is a very common style and comes in different canal length or volumes. These styles are available in all materials. They seal the canal entrance while leaving the canal itself unoccluded. They are assembled with a selective vent or SAV. such an approach would eliminate feedback.

Open – Fit IROS Styles provides the largest vent possible for use with slim tubes or RIC style hearing aids you can select SAV plugs when ordering open fit earmolds. These molds are available in all materials.

Aesthetical Considerations

Some individuals may prefer to hide their hearing impairment in their social life, and you should be a direct option when counseling your patient. What makes an earmold discret? The style,material, and tubing. The material of the earmold should match the skin tons of your patient. The industry is for a wide range of color options. When you place your order with the earmold lap be as specific as you can. Another feature that can contribute to desertion is style, keeping the patient’s preference and hearing loss severity in mind, you can select test visible style. (i.e., canallok, skeleton, concha).

In contrast with patients who prefer discretion, there are others who choose to showcase their personal style with these hearing instruments. You can order earmolds in multiple colors, various color patterns, glitter, custom engraving of icons or shapes, the addition of stone or gems and even glow in the dark material. Such options are available in silicons, vinyl and acrylic earmolds.




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