What is accuracy in digital dentistry and what role does it play in your dental treatments?

Intraoral scanners (IOS) can be used to create impressions for dental indications within orthodontics, implantology, prosthodontics and as a tool for monitoring changes in the patient’s dentition. An important part of the treatment workflow is the trust that you, as a doctor, have that a scanner can be used reliably. It all starts with the scan, after all.

Scan quality is measured in terms of accuracy. In this article, I will give you a walkthrough of what accuracy is, how it is measured, how it affects your treatment and how you can interpret accuracy data in clinical studies. I’ll highlight a few clinical studies that have been conducted on intraoral scans over the past years and walk you through their conclusions.

What is accuracy of intraoral scans?

Accuracy is the major method in evidencebased research to assess the quality of intraoral scans for clinical use. The consensus on what Accuracy stands for is documented in the ISO 5725-1 standard¹, and comprises two elements:

Accuracy is regarded as one of the major differentiators for IOS capabilities². When assessing accuracy studies within the Clinical literature, it is important to be aware of the distinction between in vitro or in vivo. Both are important.

• In vitro studies enable the user to control environmental factors to control experimental parameters ensure minimal bias, however, do not reflect the complications of the clinical environment.
• In vivo studies reflect the use of the scanner in an actual patient treatment workflow. In these studies, there is greater difficulty of normalizing the test environment. For example, the presence of saliva and the difficulty of normalizing replicate scans pose challenges. Furthermore, in vivo studies cannot easily measure Trueness, as it requires a very accurate highgrade industrial scanner reference scan (not an IOS) to compare with. Trueness has been demonstrated in a few in vivo studies³.

How does accuracy impact treatment results?

Accurate intraoral 3D models facilitate patient diagnosis, optimal treatment workflows and treatment outcome evaluation. Conventional impressions, whilst widely used for the same treatment purposes, can cause errors when translated into a digital format. This can impact the accuracy of the patient model which treatments are based on.

Our clinical research department keeps a close eye on the research being done on digital technologies in dentistry. Our ebook "Intraoral scanning and treatment quality" gives you a deep dive - with practicioner`s experiences.

Digital impressions in dentistry: avoid potential errors

For example, impression taking using the conventional method can result in errors such as air bubbles, whereas this problem is eliminated using an IOS.

Furthermore, a digital scan can be stored more easily with no risk of changes because of environmental factors, which is a risk with gypsum models. Think for example of model breakage, or shrinking or expanding during lab transit.

The replicability of taking an IOS is also considerably easier, more comfortable for the patient and less time consuming⁴. Both conventional and digital impressions require training. This is an important factor in accuracy: poor digital impression taking can affect the treatment workflow by reducing accuracy of the scan. However, the learning curve for sufficient impression taking has been shown to be faster with IOS compared with conventional impression taking methods⁵.

Accuracy data in clinical studies with 3Shape TRIOS

During the past years, there’s been a lot of studies that compare accuracy of digital impression methods against each other or against conventional impression taking methods. Below, I will highlight a few of the studies where accuracy of intraoral scanners is thoroughly reviewed and compared.

References:

1. Https://www.iso.org/obp/ui/#iso:std:iso:5725:-1:en. ISO 5725-1:1994(en) Accuracy (trueness and precision) of measurement methods and results.

2. Kihara H, Hatakeyama W, Komine F, et al. Accuracy and practicality of intraoral scanner in dentistry: A literature review. J Prosthodont Res. 2020;64(2):109-113. doi:10.1016/j.jpor.2019.07.010

3. Nedelcu R, Olsson P, Nyström I, Rydén J, Thor A. Accuracy and precision of 3 intraoral scanners and accuracy of conventional impressions: A novel in vivo analysis method. J Dent. 2018;69(November 2017):110-118. doi:10.1016/j.jdent.2017.12.006

4. Glisic O, Hoejbjerre L, Sonnesen L. A comparison of patient experience, chair-side time, accuracy of dental arch measurements and costs of acquisition of dental models. Angle Orthod. 2019;89(6):868-875. doi:10.2319/020619-84.1

5. Kouveliotis G, Tasopoulos T, Karoussis I, Silva NR, Zoidis P. Complete denture digital workflow: Combining basic principles with a CAD-CAM approach. J Prosthet Dent. Published online February 2021. doi:10.1016/j.prosdent.2020.12.024

6. Amornvit P, Rokaya D, Sanohkan S. Comparison of Accuracy of Current Ten Intraoral Scanners. Grassia V, ed. Biomed Res Int. 2021;2021:2673040. doi:10.1155/2021/2673040

7. Nulty AB. A Comparison of Full Arch Trueness and Precision of Nine Intra-Oral Digital Scanners and Four Lab Digital Scanners. Dent J. 2021;9(7). doi:10.3390/dj9070075

8. Kim RJY, Benic GI, Park J-M. Trueness of ten intraoral scanners in determining the positions of simulated implant scan bodies. Sci Rep. 2021;11(1):2606. doi:10.1038/s41598-021-82218-z

9. Diker B, Tak Ö. Accuracy of Digital Impressions Obtained Using Six Intraoral Scanners in Partially Edentulous Dentitions and the Effect of Scanning Sequence. Int J Prosthodont. 2021;34(1):101-108. doi:10.11607/ijp.6834

10. Gutmacher Z, Kelly A, Renne W, et al. Evaluation of the accuracy of multiple digital impression systems on a fully edentulous maxilla. Quintessence Int. 2021;52(6):488-495. doi:10.3290/j.qi.b1244373