This year’s HR Dispenser survey (June 2002 HR, pages 14-32) pointed out a significant trend: 80% of all dispensing professionals now say that they are online—up from 69% last year. This is great news. Why? Because the Internet is having an amazing impact on how business gets done—and its influence continues to increase. Today, because of the proliferation of the Internet, “business” and “e-business” are quickly becoming one and the same.

In recent years there has been an explosion of Internet-based technologies permeating almost every aspect of our daily lives, and there seems to be no end in sight. Internet technology has also become less expensive and more user friendly, making it easier to adapt and integrate these technologies into the hearing care business structure.

A Virtual Orientation in the Hearing Care Business
A significant percentage of hearing instrument sales worldwide are custom products. This is especially true for the US market, where approximately 80% of all hearing instruments dispensed are custom instruments. Therefore, issues that influence the delivery process can have a significant impact across a large segment of the hearing care business.

For the sake of this discussion, the “process” is defined as all aspects of delivering a hearing instrument to the user. This includes, but is not limited to:

• acquiring diagnostic information
• taking an impression
• filling out an order form
• shipping the order
• entering the order and data
• manufacturing the shell
• selecting the matrix
• selecting the components
• custom assembly of the final aid
• invoicing
• return shipment
• dispensing the instrument
• follow-up including fine-tuning
• possible remake or repair
• monthly statement reconciliation

High rates of return continue to be a significant issue affecting the manufacturer, hearing care professional, and end-user. Unsuccessful fittings result in a loss of time and money for both the dispensing professional and the manufacturer alike. They also have a damaging effect on customer satisfaction. Custom instruments have been manufactured essentially the same way for the last 30 years, and their manufacture relies heavily on the ear impression. The “impression process” can arguably be considered the weakest link in the custom production and delivery chain.

A new process for manufacturing hearing instrument shells, called LasR™ (Laser Accurate Scan Replication), has recently been developed by Siemens Hearing Solutions. LasR-made shells have been shown to provide higher levels of client satisfaction for factors such as wearer comfort, retention, and lack of feedback.¹ These findings have recently been corroborated using a sample of 125 hearing instrument users (T.M. Velde, unpublished data, 2001). The new process shows great promise to enhance the accuracy of the shell fit by more accurately reproducing the original impression while reducing manufacturing turn-around time.

This new process, as well as processes like it being developed industry-wide, are the cornerstone of virtually integrating the hearing instrument delivery process (see sidebar on page 50). It has also initiated a complete re-engineering of the custom hearing instrument manufacturing process at Siemens. The process is designed to take advantage of other significant developments, such as electronic form (e-form) ordering, on-line information access, electronic data transmission, and new manufacturing processes such as laser sintering.

Inefficiencies in the Impression-Taking Process
The ear impression is necessary to manufacture a custom hearing instrument shell. It is one of the most significant components influencing the ultimate success of the hearing instrument fitting, and arguably one of the most problematic components influencing success. Variables such as comfort of fit, retention, occlusion, feedback, and manufacturing turn-around time are all greatly influenced by the ear impression. As LasR has a direct impact on these factors, it warrants a closer examination of the impression and the factors that make it the least reliable link in the chain. Reasons why the hearing instrument delivery process can be negatively affected by the ear impression include:

1) The impression-taking process itself. Taking a physical impression of the client’s ear introduces many opportunities for error. It is greatly influenced by the material used, manner in which the material is injected into the ear canal, anatomy of the ear canal, movement of the jaw, and the experience level of the dispensing professional. Impressions received by manufacturers are often less than optimal for accurately producing a shell that will house the necessary electronic components and comfortably fit the anatomical structure of the client’s ear. As the ear impression is the “die” from which the shell is cast, a sub-par impression can only result in a shell that fits poorly.

2) Impression material. No impression material can be considered “perfect” for all impression processes. Many materials and methods are available for delivering the material into the ear. Furthermore, among the variety of current materials, there is no agreement in the hearing care industry regarding the best material to use.

3) Time needed to get the ear impression(s) to the manufacturing site. It takes time to ship the impression to the manufacturer. Even the use of overnight shipping services requires at least one day to get the impression to the manufacturer. Depending on the geographic location of the dispensing professional and the manufacturer, shipping time may be even longer. Additionally, there are many other factors that can cause delay in the shipping (eg, weather, missed pick-up, incorrect routing, etc).

4) Handling of the impression. The shipping process itself provides opportunities for the impression to sustain damage or be altered in some fashion. Factors such as heat, cold, and mishandling (eg, crushing) can yield a damaged impression. When the impression is received at the manufacturer, it requires physical handling before the shell is actually fabricated. The impression is removed from the shipping container, which requires pulling a glued impression off the bottom of the box. This can stretch the impression.

The impression also typically gets “prepped,” which means it is trimmed, waxed, etc. This process requires a technician to make several decisions based on the structure of the impression as he/she interprets it. Even the most experienced technician can make a mistake that can lead to an altered representation of the client’s ear. It is especially important to recognize that the technician has only the impression itself on which to base these judgements, and that impression may well have already been altered at an earlier point in the process.

5) The choice of hearing instrument style. Once the dispensing professional has taken the impression, they (along with the client) make a decision on the style of instrument that will be ordered. This choice is often influenced by the client’s desire to have a cosmetically pleasing, small hearing instrument—a decision that may not necessarily be consistent with the shape and size of his/her ear canal. An experienced dispensing professional can typically judge if the ear will accommodate a particular shell style (eg, CIC vs canal, etc). However, the final decision of what can be built from a given impression is made by the manufacturer. If the manufacturer determines the requested shell style cannot be built due to ear size, the hearing care professional typically needs to be contacted, which often delays manufacturing time. And this delay can be exacerbated by the fact that the dispensing professional also has to contact the client about the change.

What can be done to mitigate the issues described above? The most effective solution would be elimination of the physical impression of the ear. That could be accomplished as follows:

1. Scan the ear directly to create a data set that represents the ear.
2. Translate the data via mathematical algorithms into a virtual ear impression. This eliminates the physical ear impression and could allow the selection of shell style based on the ear size and shape.
3. Transmit this data to the manufacturing site by electronic means, eliminating the need for shipping.
4. Configure this virtual impression for manufacturing via software, eliminating the “prep” process.
5. Fabricate the shell, based on the virtual impression, using selective laser sintering. This could provide an exact duplication of the anatomical structure of the ear.

The technology needed for Step 1 and 2 is not yet refined to the point that it is commercially available. It is likely to become available within the next 2-4 years. However, there is a way to already take advantage of parts of this process.

The Virtual Impression Process
The concept behind the virtual impression process is total automation of shell-manufacturing, consequently eliminating many of the inefficiencies described above. At this time, the physical ear impression is still the first step in the LasR process. The recommended impression material for this process is silicone.

Figure 1. The 3-dimensional scanning system used to scan the impression and render a “point cloud.”

Figure 2. The point cloud, a 3-dimensional computerized representation of the impression.

Figure 3. The virtual model of the shell can be configured for venting, receiver openings and component placement.

Figure 4. The shell is built one layer at a time, and this produces a textured or stippled surface that is thought to help in retention in the ear canal.

Once the ear impression is received by the manufacturer, the process begins by scanning the impression with a laser optical scanner. Unlike a flatbed scanner/copier used to scan paper documents, the scanner used for virtual impression-taking is a three-dimensional system (Figure 1). The resulting data file, called a “point cloud,” is the virtual image of the impression (Figure 2). This image is an exact electronic duplicate of the impression, and its accuracy is designed to far exceed traditional physical methods for making the impression investment.

This digital image is then analyzed by customized software algorithms to form a “virtual” model of the shell. The virtual shell is then configured for venting, receiver opening, and component placement (Figure 3). Vents, receiver holes, and similar features can be positioned or repositioned as necessary for optimal component placement and performance to achieve the smallest possible instrument.

This virtual shell model is then used as the template to manufacture the actual shell though a process called selective laser sintering (SLS). SLS uses pigmented polyamide (nylon) polymer powder to construct the shell by sintering (ie, melting and fusing) the powder for exact replication of the impression.

The shell is built one layer at a time, and this process results in a shell with a textured or stippled surface (Figure 4). This surface texture has a slightly rough feel, which is believed to be one of the contributing factors to better retention of the shells in the ear. The polymer shell material has been shown to be more durable than current shells and is biocompatible.³

Because the data from the scanned impression is stored as a digital file, replacement is simple in the case of loss or damage. If a client loses a hearing instrument, it is possible to order a replacement quickly and easily using the existing stored data. However, depending on the length of time since the original impression was taken, a new impression may be appropriate if the dispensing professional suspects any change in the patient’s ear canal structure.

Assessing the Future of the Virtual Impression
This type of shell-making technology holds some fascinating possibilities for the not-too-distant future. As software algorithms are improved, additional refinements of the virtual shell will allow for an even more accurate fit of the hearing instrument. Software algorithms will allow for simulations of insertion and removal, as well as simulations of the dynamics of the ear canal during jaw movement when speaking or chewing.³

Will it be possible to eliminate the ear impression completely? Research efforts are underway on scanning the ear directly as a means to create a virtual impression. It may be possible in the future to eliminate the physical impression, transferring all the necessary patient data directly to the manufacturer via the Internet.

However, one possible interim step is a portable desktop LasR scanner that scans the impression in the dispensing office. The data file of the scan is attached to an electronic order form and transmitted to the manufacturer instantaneously, eliminating shipment requirements. Siemens and other manufacturers are now producing a significant percentage of custom hearing instruments using the virtual impression-taking process.

References
1. Lesiecki W, Velde T, Powers T, Burton P, Pietrafitta M. Hardware and software solutions for the new millennium. Paper presented at: Annual Meeting of the American Acad of Audiology; April 2002; Philadelphia.
2. Singh A. Business Impact of the Internet—Key Trends. Iselin, NJ: Siemens Medical Solutions Group; 2001.
3. Masters M, Mathey M. Direct manufacturing of custom made hearing instruments an implementation of digital mechanical processing. Rapid Prototyping. In press.