The top 3 mistakes dental professionals make when taking traditional impressions

December 3, 2018

Impressions are an indispensable yet tricky aspect of every dental practice. Find out how to simplify the process.

Conventional impressions are vital for multitudes of dental procedures, ranging from crowns and bridges to orthodontics and cosmetic dentistry. However, they’re also challenging to perfect because dental professionals are human and make mistakes. In other words, making a great impression is both indispensable and infuriating.

Most clinicians have tips and tricks for taking top-notch traditional impressions. We spoke to clinicians across the country to discover the top three mistakes dental professionals make when taking traditional impressions and how to fix them.

What makes a great dental impression?

An outstanding dental impression will result in a perfect negative impression of the patient’s teeth, the soft tissue and the sulcus between them. When this negative is captured, the restoration or dental procedure can be made to fit like a glove.

Read more: The 10 golden rules for taking impressions

However, when it isn’t an excellent dental impression, the restoration will not fit like a glove - or anything else for that matter.

Tissue retraction and isolation is essential to preparations for conventional impressions. Most experts recommend the dual-cord or double-cord technique to allow for adequate access into the space between the tooth and the surrounding gingiva.

Tissue management is also a foundational element in taking accurate impressions. The area must be free of anything that could interfere with the capture of the negative, like blood or saliva. Nothing should move the impression material away from the area it’s attempting to capture.

What makes a dental impression not so great?

Not-so-great conventional dental impressions have numerous reasons for their shortcomings. Some reasons are in the dental team’s control, while others aren’t. Setting aside for the moment the things the dental professional can’t change, let’s take a look at the things they can.

Here are the top three mistakes dental professionals make when taking conventional impressions.

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Mistake #1: Taking the impression before examining the prep and adequately managing the tissue

All our experts agree that neglecting to deal with isolation and control the tissue is the top mistake made in taking conventional dental impressions. The results are less-than-ideal impressions, which can lead to restorations that don’t fit.

Dr. Tim Bizga, a private practice general dentist in Cleveland, Ohio, has a unique experience with dental impressions. He was once a chairside assistant and also worked as a dental lab-technician, making his perspective unique among others in the field of dentistry. Dr. Bizga says the primary reason the dental team doesn’t achieve adequate tissue retraction and management in its prep is that the team usually feels hurried.

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Dr. Mark Hyman was a private practice dentist in Greensboro, North Carolina, for 32 years. Now an adjunct full professor at the University of North Carolina School of Dentistry (his alma mater), he no longer practices, but he remembers the pressure of getting impressions done efficiently.

“I recognize that the meter is running, and most doctors and teams are running on 10-minute time schedules. When you’ve got a bleeder and the margin isn’t crystal clear, it can be tough,” Dr. Hyman says. “But if you don’t have adequate tissue management, you shouldn’t even be taking the impression.”

Dr. Richmond Chung is a private practice general and cosmetic dentist in Orange, California. He says he sees mistakes resulting from inadequate isolation.

Moisture control is vital around the preparation. Dr. Chung’s practice uses the double-cord technique to isolate. Dr. Chung says selecting the wrong size for the first cord can lead to mistakes.  He adds that hemostatic agents can help manage bleeding in the prep area, whether present in the cord itself or applied directly to the site.

“But that first cord is critical,” Dr. Chung says. “You want to make sure that this cord is placed below the margin of the preparation.”

For hemostasis, Dr. Hyman advises doctors to invest in an affordable, quality laser, like DenMat’s NV® PRO3 soft tissue laser. He also says to reinject the prep with lidocaine with epi, and then double pack the cord, first with the triple zero, the smallest cord size, followed by a double-zero-sized cord.

“Put a cotton roll there and let the patient bite down for five or 10 minutes while you do a hygiene check, instead of running around, rushing and compromising,” Dr. Hyman says. “Give it time, so the hemostatic has time to work.”

Dr. Bizga recommends that the team employs specific impression systems and mental checklists. Taking the time to run through a list helps the team slow down, remain present in the moment and view their work with a critical eye.

“Sometimes just a slight adjustment to your prep design coupled with a few more minutes of compression or retraction can make all the difference to the final results,” Dr. Bizga says.

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Dr. Hyman also favors a mental checklist. In addition, he recommends enhancing visual ability with loupes or an intraoral camera, like the Digital Doc. Dr. Hyman advises dental professionals to take a scan and look at it critically, asking the following questions:

•    Is your clearance optimal?
•    Does your prep draw?
•    Do you have undercuts?
•    Are all the caries gone?
•    Did you do a build up?

“This isn’t magic,” Dr. Hyman says. “It’s common sense, and everybody knows it, but you get busy. There is an old saying in dentistry, ‘If you don’t have time to do it right the first time, when do you have time to re-do it?’”

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Mistake #2: Using the wrong sized tray

Dr. Hyman says another big mistake that occurs with traditional impressions is using a poor-fitting or low-quality tray. He says dental professionals make this mistake because they take for granted that the tray will fit. However, if one doesn’t pay attention, then the fit could interfere with the impression’s outcome.

“Is the tray touching a tooth? Is it hitting a tori? Is it too small or too narrow? All of these things add variability,” Dr. Hyman explains.

The good news, Dr. Hyman says, is that tray size problems aren’t difficult to determine; it’s a matter of paying attention. Dr. Hyman says that if you sub your impressions out to a teammate, ensure he or she is trained properly on how to choose the right sized tray.

Related reading: Tips and tricks for creating long-lasting restorations

Dr. Chung agrees that selecting the right tray size for the arch is crucial. He emphasizes that it’s critical to capture not just the area of the preparation but also the surrounding teeth and the contralateral side for cosmetics, form and anatomy. These areas contribute to the arch form and maintain symmetry for cosmetic purposes as well as the patient’s feel for the final restoration.

“If one side is completely different from the other, patients notice,” Dr. Chung says, “They notice the variance in anatomy and detail, or the lack thereof.”

In addition to having the proper tray size, Dr. Chung and his team use a combination of light-body and heavy-body impression material to capture the detail. They place light-body material around the preparation and seat the tray with the heavy-body material. 

“It’s not that sexy, but it’s so important to make sure that you have the right tray,” Dr. Hyman says.

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Mistake #3: Being short-sighted about the damage caused by cutting corners

When an impression is in a tricky spot or the tissue isn’t cooperating or starts bleeding, Dr. Bizga says it can throw everything off track. The practice feels pressure to keep moving and stay on schedule. So the team pushes ahead, even though it knows that the impression produced will be less than ideal.

Dr. Bizga says this approach is short-sighted. There are significant costs for the practice associated with remakes, to both overhead expenses and productivity, but many dental practices are unaware of them.

“Remakes eat profits and drag production down,” Dr. Bizga explains. “One of the best ways to avoid mistakes is to prevent them.”

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Dr. Bizga estimates that the cost of an average conventional impression is around $20. While most dental professionals wouldn’t willingly throw away $20 bills, rushing the prep and tissue management to get to the next step faster is doing just that.

“Keep in mind this mantra:  There are two ways to do things - the right way and again,” Dr. Bizga says.

“One of the cardinal sins of dentistry for me is to look at an inferior impression and then call your lab and say, ‘Just make it work,’” Dr. Hyman says. “We are willing to buy a $100,000 CAD/CAM machine and a $100,000 cone beam, and a $5,000 Digital Doc intraoral camera, but we won’t spend another $20 on an impression? That’s a false savings.”

In addition to treating patients, dentists are responsible for leading the team. Dr. Hyman compares it to being on stage the whole time. He says that when the dentist settles on a less-than-ideal impression, it sends the wrong message to the team about the standard of care for the practice.

Dr. Hyman is a full-time speaker on how to grow dental practices with his new venture Dr. Mark Speaks. His philosophy is for dental practices to see abundance - not scarcity.

“The team should be empowered to throw the impression away and pack the cord again. So part of that is having a trusting, loving relationship with the team to say, ‘Here’s our standard of care. If I didn’t match it, don’t even bother showing me. Just set up for a re-take,’” Dr. Hyman says. “That’s a spirit of abundance and quality instead of cutting corners."

Related reading: 5 ways that traditional impressions can go wrong

Dr. Hyman advises dental professionals who are taking conventional impressions to consider the bigger picture, which is to recognize the privilege dental professionals have for caring for another human being. He says dental professionals owe patients their best effort. When taking impressions, don’t cut corners. Instead, refine the prep, add some local, pack another cord and let it sit long enough. Also, don’t rule out additional training.

“If you are having a constant problem with your impressions, it could be a problem with your prep technique. You keep lacerating the tissue, so maybe you need some more continuing education,” Dr. Hyman says.

Dr. Hyman had several fourth-generation families that he treated in his private practice days. He felt honored to have generation after generation put its faith in him, and he couldn’t imagine seeing those patients every year with a crown that didn’t fit that he put in their mouth anyway. He says that if the impression isn’t your best, then do it again and don’t worry about it.

“Do it right the first time, and if it’s not A+, take a deep breath and be proud of yourself that you are willing to redo it,” Dr. Hyman says. “Don’t look at it that you lost some money on it. Look at it that you gained your self-esteem.”