Abstract
Statement of problem
Intraoral scanners are promising options for removable prosthodontics. However, analog
aids, including occlusion rims, are still used, as a completely digital workflow is
challenging and scientific evidence on the topic is scarce.
Purpose
The purpose of this in vitro study was to assess and compare the trueness and precision
of scans obtained from a reference typodont of a completely edentulous maxilla by
using an intraoral scanner (TRIOS 3 Pod; 3Shape A/S) with scans obtained by using
a laboratory scanner (DScan 3; EGS S.R.L.) from both Type IV stone casts and polysulfide
impressions.
Material and methods
The polyurethane resin reference typodont was replicated from a clinical cast and
was scanned with a metrological machine to obtain a reference scan. Ten digital casts were
obtained by applying standardized scanning strategies to the reference typodont with
the intraoral scanner. A device was created to make 10 consistent polysulfide impressions,
and a scan of each impression was made with the laboratory scanner and then digitally
reversed to obtain 10 digital reversed casts. Ten Type IV stone casts were poured
and then scanned with the laboratory scanner to obtain 10 digital extraoral scanner
casts. The scans in standard tessellation language (STL) format were imported into
a dedicated software program, and the trueness and precision were calculated in μm.
In addition to descriptive statistics (confidence interval 95%), 1-way ANOVA followed
by the Bonferroni test or the Kruskal-Wallis and the Dunn tests were used to analyze
differences among groups (α=.05).
Results
The trueness values (95% confidence interval) were digital intraoral scanner cast=48.7
(37.8-59.5), digital reversed cast=249.9 (121.3-378.5), and digital extraoral scanner
cast=308.8 (186.6-430.9); significant differences were detected between digital intraoral
scanner cast and digital reversed cast (P<.001) and between digital IOS casts and digital extraoral scanner cast (P<.001). The precision values (95% confidence interval) were digital intraoral scanner
cast=46.7 (29.7-63.7), digital reversed cast=271.2 (94.6-447.8), and digital extraoral
scanner cast=341.4 (175.5-507.3); significant differences were detected between digital
intraoral scanner cast and digital reversed cast (P=.003) and between digital intraoral scanner cast and digital extraoral scanner cast
(P=.001).
Conclusions
Directly scanning a solid typodont of a completely edentulous maxilla with the intraoral
scanner produced better trueness and precision than scanning the polysulfide impressions
or the stone casts with a laboratory scanner.
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Article info
Publication history
Published online: October 23, 2020
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© 2020 by the Editorial Council for the Journal of Prosthetic Dentistry.
