Trueness vs. Precision—What’s the Difference?

Many manufacturers tout the trueness, or accuracy, of a digital intraoral scanner in the same breath as precision. While both are important features of any scanner, the two concepts are not interchangeable. According to a recent study1 published in PLOS ONE, an online scientific journal, “an intraoral scanner should possess high trueness…but also high precision.” Let’s take a look at the difference between the terms and why both are vital for the best digital impressions.

First, trueness is a scanner’s ability to scan an object and replicate it as closely as possible to the original item—in this case, teeth, gingiva, abutments, etc. The more accurate the scanner, the more likely the digital impression on the screen will mirror the patient’s actual teeth. Precision, on the other hand, is a scanner’s ability to produce the same results consistently. If you picture a target, an accurate shot would mean the arrow hit the bullseye; or at least came incredibly close. Precise shooting would result in a grouping of several arrows close together, though not necessarily near the bullseye.

Example of accuracy and precision on a bullseye

In the past, inaccurate traditional impressions were one of the main causes of ill-fitting final restorations or appliances. Today, intraoral scanners and digital impressions have drastically cut back on the risk of inaccuracies. However, that’s not to say that all scanners are flawless. As the aforementioned study states, there can be “statistically significant differences” between scanners when it comes to general trueness. Additionally, precision should also be valued in a scanner, as the ability to reproduce consistent results—especially if a scanner is shared among users—impacts workflow and efficiency in a practice.

1Mangano FG, Veronesi G Hauschild U, Mijiritsky E, Mangano C. 2016. Trueness and Precision of Four Intraoral Scanners in Oral Implantology: A Comparative in Vitro Study. PLoS One. 11(9): e0163107.doi:10.1371/journal.pone.016310.7

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