Computed tomography scanning of impressions
will lead to more accurate lab results at quicker pace
Dimensional accuracy is essential in restorative dentistry, but dentists and laboratory technicians have spent decades grappling with restorations made from inexact plaster models. So when engineers from Glidewell Dental set out to drastically improve the dental industry standard for restorative accuracy, they drew inspiration from business sectors where precision is an imperative.
Specifically, they studied the best practices and technological might of the aerospace and medical imaging industries, where exacting precision can literally represent the difference between life and death. In both industries, achieving such rigorous, exacting precision requires a reliance on and a detailed understanding of computed tomography (CT), which harnesses the penetrating power of X-rays and the processing might of high-performing computers.
After years of study and development, Glidewell Dental thought leaders determined that CT scanning could have as momentous an impact on dentistry as it has on the evolution of aerospace and medical imaging. Armed with this knowledge and optimism, Glidewell Dental has developed a new laboratory workflow that leverages the micro-CT scanning of dental impressions to fabricate BruxZir solid zirconia restorations. The benefit to clinicians is clear: more accurate and consistent restorations returned to the dental practice in fewer days.
The landscape before CT scanning
Before now, dentists ordering restorations sent impressions to the dental lab of their choice, which were digitized so a CAD/CAM fabrication process could be initiated.
Such digitization is most commonly started with the creation of a model made of a gypsum—and this is where error is most frequently introduced into the process. Gypsum models are subject to material changes based on a litany of variables, ranging from temperature and humidity to the ratio of gypsum powder to water and the presence of air bubbles.1
Beyond this, human intervention in the trimming process can introduce additional error, and there is widespread potential for breakage given the relative fragility of stone models. These are precisely the potential pitfalls and frustrating inaccuracies that sent Glidewell Dental engineers in search of a more precise restoration workflow.
The current landscape
When doctor-submitted dental impressions are scanned directly using a micro-CT scanner, the potential impact of these environmental variables is avoided because the “model” created is an intangible digital file that reveals the internal and external structures of the impression.
After digitization by the CT scanner, the remaining workflow is virtually 100% digital; the captured file flows from virtual model preparation to a restoration design station, then to milling.
Abbreviating digitization: From about 30 minutes to 30 seconds
The list of the benefits of CT scanning for dentists and their patients is lengthy—primary among them are the extremely accurate dimensional measurements, sharp 3D imagery, and production accuracy vastly more precise than that produced from optical scanning methods.
Speed is another factor that benefits greatly from CT scanning, be it in digitization of impressions or in delivery turnaround times of finished restorations. Conventionally, dental laboratories employ a process that involved mixing gypsum powder with water, pouring it into an impression mold, waiting for it to settle and dry, then die-trimming it.
On average, this process takes 30–40 minutes, and given the frequency with which it’s repeated throughout a given day, cases must sometimes wait until a production team member becomes available. Compare that lengthy and cumbersome process with CT scanning, where single-unit impressions can be digitized in less than 30 seconds. (Long-span impressions take about 90 seconds.)
The accuracy for which doctors have long waited
Speed is certainly an important factor, but the ultimate beneficiaries of CT scanning will be the patients in whose mouths these CT-initiated restorations are seated. Restorations made through CT-initiated workflows exhibit excellent margins, fit, contacts, contours and occlusion—an example of Glidewell Dental’s focus on precision. For dentists, the excellent news is rather obvious: Satisfied patients are loyal patients.
French writer Victor Hugo once wrote, “Nothing is more powerful than an idea whose time has come.” Hugo was clearly not referring to restorative dentistry, but the point is no less relevant: The time has come to elevate the standard and expectation of what can be achieved with restorations. The implementation of CT-initiated impressions and their manufacturing out of BruxZir solid zirconia heralds the arrival of a better, stronger, faster restoration process.
1. Kerr M, Park N, Leeson D, Nikolskiy S. Dimensional accuracy of microcomputed tomography-scanned half-arch impressions. J of Prosthetic Dentistry. 2019 May; 121(5):797-802.