Finish line distinctness and accuracy in 7 intraoral scanners versus conventional impression: an in vitro descriptive comparison
BMC Oral HealthBMC series – open, inclusive and trusted201818:27
© The Author(s). 2018
Received: 12 September 2017
Accepted: 14 February 2018
Published: 23 February 2018
Abstract
Background
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. 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.
Methods
A 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.
Results
All 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.
Conclusions
There 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.
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