"There must be academic proof that digital dental tools are reliable"
Dr János Vág DMD, PhD, is an Associate Professor and the Head of Department for Conservative Dentistry at the Semmelweis University in Hungary. In the past few years, his research has focused on digital dentistry and evaluating the accuracy of CAD/CAM systems. In addition to having published 49 articles in peer-reviewed journals, Dr Vág has vast experience from clinical work at a dental clinic as well. Therefore, he can tell a thing or two about the importance of dental research for clinical work as well as the benefits of going digital.
Dr Janos Vág became a dentist of necessity, although he would have wanted to become an engineer in computer sciences. However, at the time he was supposed to choose his educational path in 1989, just before the end of socialist rule in Hungary, there were scarce opportunities for engineers. His father, a dentist, suggested he could make use of his scientific and technical interests in dentistry as well, so Dr Vág decided to follow his father’s footsteps.
Indeed, for the past decade, Dr Vág has also been able to combine his interest in computer sciences to his profession and study the technical part of dentistry – following the evolution of digital dentistry. Working as an Associate Professor and the Head of Department for Conservative Dentistry at the Semmelweis University in Hungary, Dr Vág has made an impressive academic career, having published 49 articles in peer-reviewed journals with 370 citations.
However, in addition to academic research, Dr Vág also has a lot of clinical experience. For five years, he worked at a dental clinic only doing clinical work. Today, he is doing both as a conservative dentist mainly focusing on restorative dentistry and endodontics. He also performs oral surgery and prosthetic treatments, as it is common in Hungary for dental specialists to also cover bigger areas and do general dentistry.
Digital dentistry brings in more patients – and makes the daily work fun
Although digital dentistry has been an industry buzzword for several years already, going digital is not on the agenda for the majority of dentists yet, says Dr Vág.
“Using digital workflows will completely change the work at the dental practice. However, most dentists are still not taking any steps to becoming digital dentists. This is not only the case in Hungary, but in the US and on a global scale as well.”
Dr Vág recommends all dental professionals to make the transition to digital dentistry. He thinks it is controversial how dentists are often ready to invest in a car double the price of an intraoral scanner, although the car does not offer any return of investment for a dental clinic – it is bought merely for fun. At the same time, they are not willing to invest in high-quality CAD/CAM technology which would benefit their clinic – and make their daily work fun.
“Believe me, digital dentistry and intraoral scanners are big fun as well. In dentistry, we should be ready for new things that might not be beneficial in the first few months but are good fun and make our work much better. Through these investments, dentists can also gain more patients, who might never go back to their previous dentists if they lack the technology.”
Starting from September, the undergraduate students at the Semmelweis University must already learn to make inlays, onlays and single crowns using CAD/CAM solutions: an intraoral scanner, design software and a milling machine. The goal is to teach students how to prepare a tooth for scanning and digital restoration design.
“Fortunately, digital dentistry is not the future, it is the presence.”
Comparable academic proof needed to convince the majority
While some dentists do not even consider going digital, others are more advanced in digital dentistry than the existing academic research. They immediately try out new technology and find out by themselves how to make the best use of it.
“Some dentists already manufacture for example complex bridges using only digital impressions as the basis. At the same time, they wonder why we are even studying the scanners, because they have no issues with their treatments whatsoever,” Dr Vág tells.
“But if you want to get the majority of dentists to go digital, there must be academic proof that intraoral scanners and other digital dental tools are really reliable instruments,” he emphasises.
Dr Vág believes it is important to conduct research on intraoral scanners, as a general dentist cannot otherwise really judge their trueness and accuracy, although they could compare other characteristics easily, such as the weight of the scanner or usability of the scanning software.
Currently, however, it is difficult for dental professionals to make conclusions based on research. For a couple of years now, Dr Vág has studied the differences between intraoral scanners in their precision and trueness. He has noticed it is almost impossible to make any comparisons and meta-analyses between the scanner studies, as the data and results in different studies are often incomparable.
“The main problem is that everybody uses different methods. From the scanning set-up to the super-imposition analyses and statistics. All studies are so different that they cannot be compared.”
“For a study I prepared for the Digital Dentistry Society conference last October, I compared studies from the past 10 years, including trueness data figures. There were no correlations between improvement in trueness and the year, because different techniques were used in every study. Meta-analyses fail, because they studies are just not comparable.”
According to Dr Vág, it is obvious that a 10-year-old scanner cannot be compared to a recently introduced scanner, as the technological development has been rapid in the past few years. However, this conclusion cannot be made based on the research, due to the varying methodology.
“Today’s scanner might be even ten times better, but it can hardly be detected in research, and that’s a big problem.”
In the recently published study for full arch trueness of intraoral scanners, no statistical differences were found between the top three performers, which included Planmeca Emerald™ S.
Industry standards could help make intraoral scanner studies more helpful – and reliable
To tackle the problem of incomparable studies, all future studies, journals and companies should start using standardised tables for each new scanner study and data used in the study, including the cast app methodology, Dr Vág suggests.
“For example, there are standardised ISO sheets for testing dental filling materials, which everyone must follow for every measurement such as strength and flowability. Our industry needs standardised methods for testing intraoral scanners as well – especially now when differences between the devices are subtle but nonetheless significant for the treatment outcome.”
Currently, it is also difficult to interpret the results of the intraoral scanner studies for practical clinical work due to the lack of common methodology. Often there are also only statistical differences in the studies, which do not affect the end result of a treatment.
“Studies are good for comparing the scanners but do not often tell anything for the dentists. For example, if the trueness of one scanner is fifty micrometres, the dentist wonders if it could mean there will be fifty micrometre gaps in a bridge manufactured using those intraoral scans. The answer is no, even if the milling error is assumed zero, because the measurement method does not give a clinically meaningful value. We cannot actually say for sure. Additionally, the fabrication process includes so many different steps that can affect the outcome.”
Similarly, in implant scanning, it is hard for dentists to find information on what the tolerance level for a screw-retained implant is, although they require high accuracy. Failing to meet the tolerance level could mean that the screw does not fit into the position, which can fracture the screw. Therefore, more research in precision and trueness is still needed.
“In academic research, it must be considered which values are meaningful for the dentist. For example, how much error the dentist can expect by using a particular intraoral scanner. Dr Francesco Mangano, for example, conducted a great study last year (Imburgia, Kois et al. 2020)*, in which meaningful values were delivered for the dentists.”
Recent research reveals the effect of materials and software updates on intraoral scans
Dr Vág recently published a paper in which a group of researchers studied the effect of software updates and materials for intraoral scanners. The original idea for the study came from Dr Walter Renne, DMD, Professor at the Medical University of South Carolina. According to Dr Vág, it was surprising how little these matters had been studied before, although the study showed they have a huge effect on study results.
“It was surprising, because many researchers use different in-vitro models to test intraoral scanners, and they never even think the materials of the models would make a difference. At the same time, everybody knows from experience that software updates can make a huge difference. It can make a scanner into a completely new device, but its effect had still not been studied.”
The recent study used a special model, in which every tooth contained diverse optical materials, such as different types of composites, zirconium, ceramics, enamel, dentine, amalgam etc. In the analysis, every tooth was segmented from the full arch and the surface compression was made only on specific teeth, which the researchers knew worked for that material.
“With the model, we managed to measure the deviation at the level of different substrates. That was one novelty of our study.”
Another novelty was the effect of software version upgrades. The study included two scanners in which the hardware had been updated as well. However, although updated hardware made a notable difference in results, software upgrades made an even bigger one.
“Right now, software upgrades are still affecting trueness and precision, and thus the overall result of the scan. Our study shows that it is still very important to always update the software in order to reach the acceptable level for the scans. Probably in the future, software upgrades will no longer make such a big difference in results but rather introduce new functions. Then, users can well decide whether they update or not.”
Although the impact of materials and software updates was proven notable, the results do not mean the intraoral scanner accuracy would not yet be sufficient for all indications or full arch scans. On the contrary, the general problem with scientific studies is the duration it takes before they are published. During that time, software might have been updated several times already.
“A study usually takes one or two years from the idea to be published. The process from creating the experiment to analysing the results and writing the paper takes a long time. At the time when a study is published, the data might already be out-of-date due to software updates. This way, a scanner tested in a study might already be much better than what we see in the literature.”
Still, academic research is needed to convince the masses on the reliability of digital dental solutions.
“Once there is no more feedback from clinicians, meaning every restauration fits, there is no more need for intraoral scanner accuracy research.”
*Imburgia, M., Kois J., Marino E., Lerner H. and Mangano F. G. (2020). “Continuous Scan Strategy (CSS): A Novel Technique to Improve the Accuracy of Intraoral Digital Impressions.” The European journal of prosthodontics and restorative dentistry, 28(3), 128–141.
Copy: Mari Koivunen
Images: Semmelweis University
Planmeca Oy and Planmeca Group
Planmeca Oy is one of the world's leading dental equipment manufacturers with a product range covering digital dental units, CAD/CAM solutions, world-class 2D and 3D imaging devices and comprehensive software solutions. Headquartered in Helsinki, Finland, Planmeca’s products are distributed in over 120 countries worldwide. With a strong commitment to pioneering innovations and design, it is the largest privately held company in its field. Planmeca Oy is part of the Finnish Planmeca Group, which operates in the field of healthcare technology. The Group's turnover in 2020 was MEUR 764, and it employs nearly 2,900 people worldwide.
www.planmeca.com
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