Institute of Digital Dentistry tests current IOs

Dr Ahmad Al-Hassiny

Mon. 12. August 2024

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2024 has been a busy and exciting time for the digital dentistry industry, so many new products having been released every three to four weeks this year. Two launches, in particular, have captured attention: iTero Lumina, the latest intra-oral scanner (IOS) from Align Technology since iTero Element 5D, and the Medit i900, which is Medit’s most premium scanner to date and said to be one of the lightest IOSs on the market.

At the Institute of Digital Dentistry, we are very lucky to be able to test all our IOSs on real cases and actual patients within a clinical environment. By doing so, we can provide an honest and unbiased review when comparing the performance of each IOS. We put these IOSs to the test to see how well they perform compared with some of the most popular IOSs in the market right now, and in this article, you can see the results of the individual scans—colour scans, exported STLs, tessellated meshes and close-up images of the preparation margins.

For the evaluation, I scanned the crown preparation of tooth #36 in the same patient with the following five scanners (Fig. 1) on the same day:

TRIOS 5 (3Shape);
Aoralscan 3 (SHINING 3D);
Medit i900;
iTero Lumina; and
CEREC Primescan (Dentsply Sirona).

Fig. 2: Example of colour scan capture.

Individual scans in their native software

Every IOS is equipped with its own scanning software. Most scanners can automatically remove scanning artefacts such as movable soft tissue, cheeks and tongue through artificial intelligence-driven algorithms, and some perform better at this than others.

We can preview how these scanners capture colour (called texture) using the scanner’s native software. Every scanner captures colour slightly differently, depending on how accurately the scanner can pick up the light bouncing back off the prepared tooth and adjacent teeth. It also depends on the software algorithms that convert this data into colour (Fig. 2).

Colour scans of the same tooth preparation were captured using the five scanners and previewed in their native software. The TRIOS 5 scan was less bright (lower value) than the others (Fig. 3). Both the TRIOS 5 and Medit i900 scans were less warm in colour (hue) than the richer, warmer scans of Aoralscan 3, iTero Lumina and CEREC Primescan. The Aoralscan 3 scan appeared to be the most photorealistic in comparison. This type of scan texture is characteristic of many IOSs manufactured in China—whether you prefer realistic-looking capture of the intra-oral structures or a more illustrative representation is purely personal preference.

Monochromatic scans can also be taken and previewed in scanners’ native software. Scans in monochrome provide a better view of the preparation quality and are even recommended to check for any scan issues that are not as obvious when viewed in colour. Monochromatic scans of the same tooth preparation were captured using the five scanners and previewed in their native software. Unlike the native colour rendering, only two notable differences were evident between the five scans (Fig. 4). The iTero Lumina monochromatic scan was bright, almost overexposed, and the edges looked much sharper, almost jagged. The CEREC Primescan scan had slightly more definition of the occlusal morphology and the mesial and distal margins.

Figs. 3a–e: Processed colour scans of the same tooth preparation, previewed in the scanners’ native software. TRIOS 5 (a). Aoralscan 3 (b). Medit i900 (c). ITero Lumina (d). CEREC Primescan (e).

Figs. 4a–e: Processed monochromatic scans of the same tooth preparation, previewed in the scanners’ native software. TRIOS 5 (a). Aoralscan 3 (b). Medit i900 (c). ITero Lumina (d). CEREC Primescan (e).

Exported scans in third-party software

All IOSs have an open architecture that allows scans to be exported and sent to laboratories. These scans are usually exported in three various formats: STL, PLY or OBJ. STL files are exported as monochromatic scans, whereas OBJ and PLY files store colour. Not all IOSs can export OBJ and PLY files, whereas STL files are widely used as a default in the entire industry. This particular set of scanners is capable of exporting scans in these formats:

Aoralscan 3 and Medit i900: STL, PLY and OBJ
TRIOS 5 and iTero Lumina: STL and PLY
CEREC Primescan: STL.

The files of the exported scans for all the scanners were of a similar size, except for CEREC Primescan (exported on its high-resolution option), which was three times larger (Table 1). The higher resolution or encoding of larger objects requires more facets (triangles within the tessellation) to cover the 2D surface of the scan.

Laboratories often use third-party CAD software like exocad. In this case, we used Medit Design to preview the STL, PLY or OBJ files received and to take a closer look at the detail captured within each scan and the amount of data (Fig. 5). By exporting the scans outside their native software, we can view the scans objectively without the customised colour and optimised surface rendering of the individual scanner’s built-in software.

Preparation margins can also be reviewed using this software (Figs. 6–10). In the close-up images of the preparation margins and the tessellated mesh (Fig. 11), CEREC Primescan seemed to have had the densest mesh, closely followed by Aoralscan 3 and then the Medit i900, TRIOS 5 and iTero Lumina. There are yet to be any studies investigating the clinical significance of mesh density, and it is important to note that a denser mesh does not necessarily indicate a better scan.

When comparing IOSs, we usually compare them to CEREC Primescan, which is commonly regarded as one of the best IOSs in terms of accuracy. It is also a scanner I use daily in the office to fabricate same-day crowns that fit perfectly. In that light, when we compared the preparation margins captured by each IOS (Fig. 12), the iTero Lumina scan also looked quite sharp. The buccal and lingual margins were very defined (Fig. 13). Overall, all the scanners did a very good job, especially on the lingual margin, which was supragingival and sharper. The buccal margin, which was closer to the retraction cord, seemed to look less sharp but still acceptable in the scans of the other scanners.

Figs. 5a–e: Scans in STL format previewed in the Medit Design app. TRIOS 5 (a). Aoralscan 3 (b). Medit i900 (c). ITero Lumina (d). CEREC Primescan (e).

Fig. 6: Preparation margins on the TRIOS 5 scan.

Fig. 7: Preparation margins on the Aoralscan 3 scan.

Fig. 8: Preparation margins on the Medit i900 scan.

Fig. 9: Preparation margins on the iTero Lumina scan.

Fig. 10: Preparation margins on the CEREC Primescan scan.

Figs. 11a–e: Close-up images of the tooth preparation scans and their tessellated meshes. TRIOS 5 (a). Aoralscan 3 (b). Medit i900 (c). ITero Lumina (d). CEREC Primescan (e).

Figs. 12a–e: Preparation margins captured by each intra-oral scanner. TRIOS 5 (a). Aoralscan 3 (b). Medit i900 (c). ITero Lumina (d). CEREC Primescan (e).

Figs. 13a–e: Buccal and lingual margins on the scans. TRIOS 5 (a). Aoralscan 3 (b). Medit i900 (c). ITero Lumina (d). CEREC Primescan (e).

Figs. 14a–c: Deviation map of the scans compared with CEREC Primescan’s scan (a; scale of 50 μm) and sectional view (b & c). Very little deviation around the preparation area.

Keep in mind that iTero Lumina is not currently approved for restorative use by the company—in fact you cannot even choose this in the laboratory form. This option will be released later this year.

Just for interest, iTero Lumina’s scanning technology has a maximum capture distance of 25 mm, whereas CEREC Primescan can measure depth of up to 20 mm. The Medit i900 is around 20 mm too.

We allocated CEREC Primescan as our reference point when looking for capture deviations to compare against the other scanners (Fig. 14). Based on the coloured deviation key, the meshes of the scans taken with the other scanners were within 50 μm compared with the scan taken with CEREC Primescan. Within the same display mode, we also viewed the aligned scans in a sectional view, which showed minimal differences between the scans.

Conclusion

It is important to remember that the precision in capturing the details of the restoration preparation may vary slightly based on the combination of the clinician’s scanning technique and the specific scanner used. This variation can influence the final outcome of the dental laboratory technician’s restoration margin.

Overall, iTero Lumina and the Medit i900 look promising and add to the long list of capable IOSs on the market right now. Did these perform as well as you thought they would? Let us know your thoughts at www.instituteofdigitaldentistry.com.

Editorial note:

This article was published in digital—international magazine of digital dentistry vol. 5, issue 2/2024.