How to prevent hand strain when extruding heavy body impression materials

October 29, 2019

How using Practicon’s BFC3 helps protect clinician health and adds efficiency to impressioning.

When it comes to common impression materials used daily by dental assistants in the practice, ergonomics can quickly transition from a convenience to a medical necessity. Extruding highly viscous materials under certain conditions with a repetitive motion can lead to pain and even greater issues like ganglion cysts.
The impact of hand strain on dental assistants from extruding impression materials can affect productivity. However, the Practicon BFC³ Powered Impression Gun enables assistants to save their hands which is critical because without full-hand mobility, impression techniques become far more challenging to deploy and dental procedures are ultimately less effective.


Taking successful impressions

Successful impressions with high accuracy are an essential aspect of durable restorations. They hold a fundamental position in restorative dentistry, which is why it is so integral to ensure they capture precise intraoral information and maintain dimensional stability.
There are a variety of impression materials on the market today, making it a challenge to select the right products and techniques for every situation. The overwhelming number of options can lead to confusion and inconsistency, which keeps practitioners from achieving successful outcomes.
Once dental professionals, especially assistants, understand the different material characteristics, indication requirements and techniques, practices will be able to make informed decisions on the right materials, tools, and approaches for each case. They can then keep the process of obtaining impressions as stress-free and comfortable for patients and the dental team as possible.


Accurate impressions provide clinicians with detailed records of the oral cavity. They capture the exact dimensions of a preparation and soft tissue, the margins of the preparation, and the prepared teeth and surrounding dentition relationship. As materials and technology continue to improve and dental teams better understand those materials and common techniques, dental professionals will be able to obtain more accurate impressions while improving the process for everyone involved.


The impact of viscosity

Impression materials continue to advance, but to know which material and tools are best for various clinical situations, it’s important to understand impression material characteristics. Primary features include hydrophilicity, elasticity, tear strength, viscosity, dimensional stability, and working and setting time.
The flow of an unset impression material is its viscosity, which comes in four classifications: low (a syringe or wash material), medium (one-step monophasic material or heavy body), high (tray material), and very high (putty). The amount of filler present determines a material’s viscosity.
Why is viscosity important? It influences the material’s ability to capture necessary intraoral details for an accurate impression. Lower viscosity materials typically record finer details and allow for the greatest shrinkage while the material sets. The challenge with low viscosity materials is that they are more difficult to work with than materials with a high viscosity.
Understanding viscosity is important when determining the best material for a particular case. The level of viscosity needed depends on the type of restoration being placed and how much detail is necessary. For those requiring heavy body materials, the challenge of extruding the material into an impression tray can lead to repetitive strain on joints in the wrist.

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Impression material differences

Polyethers are among the materials best suited for taking multiple impressions. This accurate, effective material allows for multiple pours, provides long-term dimensional stability and features a short set time. These materials provide the accurate surface detail, minimal distortion on removal and tear strength needed to create impressions that last. They also have a shelf-life of up to seven days.
Of course, these materials also come with their challenges, including rigidity, an unpleasant taste and odor, the tendency to absorb water from the atmosphere and swell over time, and difficult intraoral removal. Even so, polyethers have a successful clinical history and offer dental professionals an established, effective material.  
Vinyl polysiloxane (VPS) materials represent another effective option for final impressions. These popular materials help ensure assistants obtain accurate impressions. They address many of the challenges associated with polyether. For example, they provide less rigid impressions that do not absorb excess fluid and also offer a neutral taste and smell. Other advantages include the ability to pour multiple casts, high accuracy, optimal tear strength, excellent elasticity, enhanced dimensional stability, and a shelf life of up to seven days.
VPS materials are inherently hydrophobic, and also feature added surfactants to increase hydrophilicity. The disadvantages include reduced polymerization when latex contamination occurs.
There are also hybrid materials that provide the benefits of both polyether and VPS materials. Vinyl-polyether hybrids offer multiple pours, high tear strength, and dimensional stability. The polyether contributes to the material’s truly hydrophilic nature without added surfactants, while the silicone element increases dimensional stability and elasticity. The hybrid material also offers a pleasant flavor, eliminating the bitter taste and smells of polyethers. Vinyl-polyether hybrids present an ideal combination of characteristics for accurate impressions.
With any of these materials, dentists can send their labs more accurate impressions, whether the impression is for a crown, an implant, dentures, or any other restoration. The flow properties these materials exhibit help improve accuracy of fit and deliver more defined landmarks. This decreases the number of retakes, remakes, and adjustments, saving practices time and money. But hidden in all these benefits is the possibility of hand strain on the part of the assistant.


Extruding heavy body materials with an impression gun

Taking a poor impression can result from a variety of factors, but in those cases where it occurs because of operator error, an electric impression gun can significantly improve the consistency of quality impressions. Practicon’s BFC³ Powered Impression Gun provides the solution to a situation that normally requires manual operation.

This tool is capable of saving assistants from strain. It is a handheld, cordless, motorized impression gun that is also portable and rechargeable. Where before the assistant would need to carefully provide the correct pressure to extrude a material from a manually operated impression gun, they can now transition to allowing a machine to do the work for them. The BFC³ gun can dispense any 1:1 or 2:1 automix material upon the assistant pressing a button. They can then use the gun to fill a full-arch tray in its entirety in less than 10 seconds.
The primary benefit of this impression gun is assistants no longer have to deal with the repetitive trigger squeezing motion that wears out the hand and wrist while reducing the assistant’s ability to carefully fill an arch. This can lead to inaccuracy and the need for remakes. The Practicon BFC³ Powered Impression Gun is compatible with 25 mL, 50 mL, and 75 mL cartridges and contains a rechargeable battery.
The design is similar enough to manual guns that dental assistants will not feel uncomfortable adding the ergonomic design to their normal workflow. With the powered gun, heavy body material is that much easier to extrude.

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Ergonomics for dental assistants

Ergonomics combined with the proper tools and materials will prevent hand strain from getting the best of diligent dental assistants. But what happens when an automatic gun is never utilized and a detrimental movement is used over and over again? The result could be a ganglion cyst, something I’ve experienced personally as a dental assistant.
The wrist is far more complex than it may first appear. It is the physical bridge between the many muscles, bones, and ligaments contained in the hand with those in the lower arm. Wrist pain is not uncommon and is often due to overuse. Common injuries include carpal tunnel syndrome and tendinitis. Long-term repetitive stress can spur pain that only worsens with time.
The problem is likely serious if the pain escalates, numbness occurs, or there is any swelling apparent. Additionally, if stiffness sets in that prevents straightening the wrist or carrying out specific movements without pain, then treatment or intervention is likely necessary. When this kind of pain comes from extruding heavy body materials, it’s best to stop the repetitive movement at once and consult a medical professional. Sometimes, the problem isn’t obvious until something visible like a ganglion cyst appears.
I had to deal with a ganglion cyst and it was not a pleasant experience. These fluid-filled cysts are non-cancerous, resembling a bump protruding from the wrist joint. These cysts may come from long-term overuse and I believe mine was certainly an effect of poor ergonomics during dental assistant duties including impressions.
Achiness, pain, and reduced mobility are general symptoms of ganglion cysts. Visibly, they are also undesirable. For these reasons, I had mine removed. This reduced my pain significantly and taught me the value of proper ergonomics.  
Before it comes to the point of consistent pain and even the need for surgery, dental assistants would do best to transition to a powered option such as the Practicon BFC³ Powered Impression Gun. It’s best to start as early as possible to reduce the strain on the wrist. Plus, impressions will be more accurate and consistent. By using this impression gun to save time and strain, dental assistants can focus their energy on other areas as productivity improves.

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