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When implants are involved, impressioning can be a bit trickier than it typically is for standard crowns. Mentor explores the latest protocols for capturing traditional and digital implant impressions.

According to the ads on TV, when you have no teeth, or simply hate the look of them, you no longer have to settle for dentures. Now you can get yourself a life-changing smile in as little as an hour. Well, in reality, it takes a bit longer what with planning, healing, and all, but dental implant placement is becoming an increasingly popular choice for those of us who are outliving our teeth.

Despite a growing consensus that saving natural tooth structure when possible is the best course of action, sometimes teeth are just not salvageable. For reasons such as this plus trends in cosmetic dentistry, technological innovation, and an aging population of baby boomers, the dental implant market continues on an upward trajectory. According to a report1 starting in 2016, the compound annual growth rate of the global dental implant and prosthetics market is expected to grow by 5.35% into 2021. Much of this growth may also be driven by the increase in dental clinics offering implants.

In fact, anticipated growth can be seen in a 2015 study, in which 84% of general dentists rated prosthodontics as the number one specialty they provide, with 54% reporting they offered implantology among their services. Conversely, the study also reports that 72% foresee implantology as a growing specialty treatment offering, while just 47% anticipate growth in prosthodontics.2

Whatever the reason for the upswing in implant placement, general practices have much to gain by offering this treatment option. Of course, to do so requires some equipment investment and additional training in treatment planning and prep work, including how to take a great implant impression. This key link in all restorative procedures also lies at the heart of placing great implants. And, for this, today’s clinicians have a couple of options.


POINT OF SALE | REALITY BYTES

  • The latest statistics indicate strong growth in the implant category.
  • Traditional impressions continue to be used in numerous practices, making impression materials, trays and related adjuncts valuable commodities in daily practice.
  • Digital impressioning is gaining ground for its many benefits, which include increased patient comfort and case acceptance, accuracy and time and cost savings overall.
  • Digital scanners are the starring technology of dental implant preparation and placement, though the use of cone beam computed tomography is also seen as a boon to successful treatment planning.

TRADITIONAL METHODS

Traditional impressions use materials such as polyvinylsiloxane or polyether, which are applied in their plastic state into an impression tray. The material is used to capture the impression, which can then be shipped to the lab to be used in fabrication of prosthetic teeth such as crowns, and, in the case of implants, abutments — the hardware that connects teeth to implants.

According to Gregori Kurtzman, DDS, a general practitioner in Silver Spring, Maryland, and a well-known educator who specializes in implant placement, clinicians who rely on traditional impressions for implant cases have some options. Says Kurtzman, “If the practitioner is taking an impression of the implant to have the lab fabricate the abutment and the crown, there is a choice of open-tray versus closed-tray impressions.‘‘

In the open-tray technique, holes are drilled into trays to accommodate copings (posts) and pins (screws), which protrude through the tray to mark the placement and orientation of the final restoration. When the material sets, the copings are unscrewed and the impression is removed along with the embedded coping and pin. The trick to this technique is to locate the pin, so that the coping can be unscrewed to allow removal.

Alternatively, there are two types of closed-tray techniques that can be employed. In one, the coping is screwed into place, and the impression material applied. When the impression is removed from the patient’s mouth, it‘s without the coping, which is unscrewed from the implant and manually placed back into its original position in the impression.

A variation on this closed-tray method uses an abutment topped with a snap-type cap. “This cap is picked up in the impression, while the abutment is left in the mouth,‘‘ explains Kurtzman. An analog matching the abutment is snapped into the embedded cap, which helps ensure correct orientation.


INTRAORAL SCANNERS

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Intraoral scanning systems typically comprise a scanning wand, monitor and software program — often mounted on a cart for enhanced mobility. Frank Higginbottom, DDS, a Dallas-based practitioner, internationally recognized lecturer and associate clinical professor in the Departments of Oral Surgery and Graduate Prosthodontics at Texas A&M College of Dentistry in Dallas, says, “Over the past years a number of additional scanning options, hardware and workflow options have been introduced. Clinicians have the option of scanning an impression only; scanning, designing and milling restorations in the office; and working completely model-less. Today’s digital impression systems are more versatile than ever, and are, in many cases, open architecture, cordless, portable, faster and very accurate.‘‘

But there is even more to them when you look beneath the hardware. As pointed out by North Wales, Pennsylvania-based dentist Steven Present, DMD, an associate professor in the Department of Restorative Dentistry at Temple University Kornberg School of Dentistry, “All intraoral scanners require some form of light to capture an image. It can be white, red or blue structured light or laser.‘‘ Further, he notes that some systems require the use of scanning powder in order to prevent disruption from reflective surfaces. Though, he says that this can sometimes reduce accuracy, takes more time and can be uncomfortable for patients.

Scanners utilize a range of image acquisition methods to create digital impressions. For instance, one system uses parallel confocal imaging, which captures the anatomy of hard and soft tissues through laser and optical scanning; another uses triangulation sampling, which involves the projection of an angled cone of light, such as that of a blue laser, to capture dental structures; a third system utilizes active wave front sampling, which allows three-dimensional (3D) in-motion technology to capture continuous video via a blue light. Other technologies can be seen in systems that feature “intelligent scanning,‘‘ which color code any areas that remain unscanned and continuous color-imaging technology, which produces full color images in 3D.

Many of these high-tech instruments offer smaller wand sizes and features to counteract hand shake as they quickly capture all the hard and soft tissue information in 3D that’s needed for computer-assisted design/computer-assisted manufacturing (CAD/CAM) dentistry — without the goop.


Many clinicians feel, however, that closed-tray methods can be problematic due to the need to reinsert copings into the material extraorally. Says Kurtzman, “This can introduce errors related to rotation if the coping is inserted but turned slightly related to its position in the mouth, or vertically if the coping isn’t inserted fully into the impression.‘‘

Such errors, says Kurtzman, can lead to problems in the fit and position of the resulting restoration. “This,‘‘ he adds, “is compounded when multiple adjacent implants are being restored as the relation between the implants is lost. Open-tray impressions solve these issues as the impression coping is locked into the impression material and removed with the tray so orientation is accurate.‘‘

Other factors that can affect impression accuracy include whether the impression is taken at implant level or abutment level. Impressions taken at implant level, are said to provide more information than those at abutment level as the material covers more area vertically. In addition, Kurtzman says that impression material viscosity differs for the two techniques.

copy“When an open-tray impression is selected, a stiffer material, such as a heavy body or tray impression material, is used in the tray to lock the copings into the material,‘‘ he notes. “This avoids any potential for movement after the impression is removed. Unfortunately, if a stiff material is used in a closed-tray impression, it may tear as the impression is removed and may prevent accurate seating of the copings back into the impression extraorally. So a more elastic material is required, such as a medium body or monophase impression material.‘‘

But despite the various options available for traditional impressioning, Kurtzman notes that digital impressions are slowly gaining favor for both natural teeth and implants. Reasons for this surely include the multiple opportunities for things to go awry when employing traditional methods.

“The more steps involved, the more chance there is for error. And there are several steps involved in taking a traditional impression,‘‘ says North Wales, Pennsylvania-based dentist Steven Present, DMD, an associate professor in the Department of Restorative Dentistry at Temple University Kornberg School of Dentistry in Philidelphia, who lectures internationally on topics surrounding implants. “There’s the use of the impression material, which must be the right consistency, and can form bubbles, tear or distort; impression copings; X-rays to confirm seating; and the use of open or closed trays. Not to mention that posterior teeth can be difficult to access with such methods, which are also uncomfortable for patients.‘‘

In fact, this last point may be the number one driver for clinicians to adopt digital impressioning. Comfortable patients tend to be happier patients who can help boost a practice’s bottom line through word of mouth. Present says, “People are always surprised by how quick and comfortable the impression process is.‘‘

“The work flow for both digital and traditional impressioning is similar, but actually better with digital than with analog methods,‘‘ says Frank Higginbottom, DDS, a Dallas-based practitioner, internationally recognized lecturer and associate clinical professor in the Departments of Oral Surgery and Graduate Prosthodontics at Texas A&M College of Dentistry. “Digital technologies have allowed clinicians to plan cases digitally and effectively reduce treatment times. This allows more time for planning and brings to fruition treatments that are more efficient   and effective.‘‘


TERMS TO LEARN

Abutment: The interface between the implant and the prosthetic.
Copings: Also called posts or heads, mark the positioning of the implant in traditional impressioning.
Fiducial markers: Reference points used in digital impressioning.
Pins: Long screws that hold the coping in place.
Provisional: Temporary.
Scan body: Posts reflecting positioning of implants in digital impressioning.


DIGITAL METHODS

Digital impressions can be taken of the implant/abutment arrangement via an intraoral scanner, through which a series of point-and-click stills, or, in some cases, videos are captured and stitched together into a final seamless impression. In fact, if a spot is missed, digital methods allow that spot to simply be rescanned, unlike analog impressions, which, if a flaw is discovered, must be entirely redone. Says Present: “You can even stop at any time to give the patient a break. The program picks up where you left off and stitches files together.‘‘

According to Present, “The goal of intraoral scanning is to capture and record the exact three-dimensional position of the desired object, whether it is a tooth or an implant scan body.‘‘

Scan bodies, Higginbottom explains, are components for use with implants that replace impression copings. “These devices fit into the implant,‘‘ he notes, “and when scanned, record the implant position and orientation.”

Kurtzman adds, “Unlike digital impressions of natural teeth, the top of the implant, which is below the gingiva, does not need to be visualized as the digital software is able to interpret what part of the scan body is subgingival. This gives us a highly accurate impression of the implant’s depth and orientation. Whereas, when scanning natural teeth you must capture the restorative margin that may be subgingival, so bleeding, tissue oozing or tissue collapse need to be dealt with to get an accurate impression.‘‘

Indeed, as noted by Higginbottom, scan body placement requires care. “It is important with implants that the scan body is seated and not damaged or marred. Also, the scan field needs to be dry. Scans in a wet field do not work; surface irregularities need to be visible and clean. Generally the screen capture usually is a good determinant of a good scan.‘‘

Present reports that with digital methods, such as guided surgery, he can plan procedures long before taking a scalpel to a patient’s mouth. Guided surgery involves the use of digital scans to virtually map out a procedure before it happens. This includes the use of scan bodies, fiducial markers and the fabrication of stents, which serve as drill guides, or templates, for drilling and incisions. “Guided surgery is very much a part of it,‘‘ says Present.

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He says his digital impression workflow begins with cone beam computed tomography (CBCT) to map out the structure of the head, neck and jaw. He then takes a digital intraoral scan of the mouth. “These files are then merged together, and treatment is planned from that. The result is improved accuracy,‘‘ he says.

Present notes that even with analog impressions, labs can turn them into clinically acceptable digital files by scanning them. Although, he says, a purely digital workflow has been shown to be more accurate.

DIGITAL BENEFITS

Few would question that we are headed toward an all-digital future where impressioning is concerned. Higginbottom says that while both traditional and digital impressioning methods have proven to be clinically acceptable, he chooses to use digital impressions for both teeth and implants for a number of reasons, including tissue management. “You must consider that with conventional impressions the process is initiated by tissue management by placement of one or two retraction cords,‘‘ he says. “Digital impressions are faster, non-messy, are as accurate or more accurate, and are very transportable compared to traditional methods.‘‘

A proponent of model-less impressioning, Present predicts that in five to 10 years everything is going to be digital, and designed on a computer. “The new generation of students graduating from dental school have grown up with the digital concept,‘‘ he observes. “That’s the future, and the future is now.‘‘

Says Kurtzman, “Digital impressioning is having its most profound effect in implant dentistry, making it easier to achieve accurate impressions and eliminating potential errors inherent with physical impressions. It also allows the practice to send the data via email to the lab and shorten lab turnaround time, as the time required to ship an impression to the lab is eliminated.‘‘

Further, Present notes, “When a scan is projected on a large monitor, you can see every little imperfection — better than you can with loupes. So the quality of the preps improves exponentially, as does skill. Digital allows you to do better dentistry.‘‘

There is little disagreement that the benefits of digital impressioning are myriad: It offers enhanced comfort and accuracy; is a cost and time saver; is beneficial for patient case acceptance and education, treatment planning and file sharing; and is proving to be a practice builder. And if that’s not enough, digital impressioning saves storage space, and is also environmentally friendly. No more waste in the form of disposable trays and impression materials to end up in landfills. And when it comes to making copies, all of this is right in so many ways.


BONUS WEB CONTENT: Anatomy of an Implant

BONUS WEB CONTENT: Teeth in a Day

BONUS WEB CONTENT: Types of Implant Placements

BONUS WEB CONTENT: Implant Considerations

References

  1. Dental implant and prosthetics market—5.35% CAGR forecast to 2021. RNR Market Research. May 11, 2016. Available at: prnewswire.com/news-releases/dental-implant-and-prosthetics-market—535-cagr-forecast-to-2021-578922011.html. Accessed January 30, 2017.
  2. Akel M. Specialty care in the general practice. Decisions in Dentistry. 2015;1(2):64.

Featured Image by GLOBALSTOCK/E+/GETTY IMAGES PLUS

From MENTOR. April 2018;9(4): 24-28.

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