Abstract
BackgroundSeveral studies have evaluated accuracy of intraoral scanners (IOS), but data is lacking regarding variations between IOS systems in the depiction of the critical finish line and the finish line accuracy. The aim of this study was to analyze the level of finish line distinctness (FLD), and finish line accuracy (FLA), in 7 intraoral scanners (IOS) and one conventional impression (IMPR). Furthermore, to assess parameters of resolution, tessellation, topography, and color.MethodsA dental model with a crown preparation including supra and subgingival finish line was reference-scanned with an industrial scanner (ATOS), and scanned with seven IOS: 3M, CS3500 and CS3600, DWIO, Omnicam, Planscan and Trios. An IMPR was taken and poured, and the model was scanned with a laboratory scanner. The ATOS scan was cropped at finish line and best-fit aligned for 3D Compare Analysis (Geomagic). Accuracy was visualized, and descriptive analysis was performed.ResultsAll IOS, except Planscan, had comparable overall accuracy, however, FLD and FLA varied substantially. Trios presented the highest FLD, and with CS3600, the highest FLA. 3M, and DWIO had low overall FLD and low FLA in subgingival areas, whilst Planscan had overall low FLD and FLA, as well as lower general accuracy. IMPR presented high FLD, except in subgingival areas, and high FLA.Trios had the highest resolution by factor 1.6 to 3.1 among IOS, followed by IMPR, DWIO, Omnicam, CS3500, 3M, CS3600 and Planscan. Tessellation was found to be non-uniform except in 3M and DWIO. Topographic variation was found for 3M and Trios, with deviations below +/− 25 μm for Trios. Inclusion of color enhanced the identification of the finish line in Trios, Omnicam and CS3600, but not in Planscan.ConclusionsThere were sizeable variations between IOS with both higher and lower FLD and FLA than IMPR. High FLD was more related to high localized finish line resolution and non-uniform tessellation, than to high overall resolution. Topography variations were low. Color improved finish line identification in some IOS.It is imperative that clinicians critically evaluate the digital impression, being aware of varying technical limitations among IOS, in particular when challenging subgingival conditions apply.
Highlights
Several studies have evaluated accuracy of intraoral scanners (IOS), but data is lacking regarding variations between IOS systems in the depiction of the critical finish line and the finish line accuracy
There are variations attributed to specific scanners where there is room for a clear separation based on image analysis
The ATOS reference-scanner presented a resolution of 50.000 triangles, followed by rounding to nearest five-hundred: TRIOS (23.5000), IMPR (18.000), Dentalwings Intraoral Scanner (DWIO) (14.500), OMNI (12.000), CS3500 (11.000), 3M (9000), CS3600 (8.500) and PLAN (7.500)
Summary
Several studies have evaluated accuracy of intraoral scanners (IOS), but data is lacking regarding variations between IOS systems in the depiction of the critical finish line and the finish line accuracy. Surfaces of a physical model are commonly scanned with a reference scanner to which digital and analogue scans can be compared [6,7,8,9,10,11,12,13,14]. Most of those studies compare the full surface of a preparation or teeth, and do not evaluate specific areas. Another review has shown similar results for single unit and short fixed dental prosthesis [23] These findings serve as a numerical value to which IOS and IMPR, as an integrated part of the workflow, can be compared. The results are well within the commonly accepted 120 μm for good clinical fit postulated nearly five decades ago [24]
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