Abstract
Objectives
To
test if the partially digital workflow by digitalisation of the
impression reveals a comparable accuracy as the indirect digitalisation
of the gypsum cast for 4-unit fixed dental prostheses (FDPs).
Materials and methods
A
titanium model with a tapered full veneer preparation of a molar and
premolar was used as analysis model. To receive a virtual
three-dimensional reference dataset (REF), it was digitised by
industrial computed tomography. Three impression materials were used
with individual impression trays (N = 36, n/material = 12):
(1) PE (Impregum Penta), (2) PVS-I (Imprint 4 Penta: Super Quick Heavy
plus Super Quick Light), and (3) PVS-D (Dimension Penta: H Quick plus
L). For partially digital workflow (group IMP), two desktop scanners
were used: (1) D810 (3Shape D810) and (2) ZZ (Zirkonzahn S600ARTI). For
indirect digitalisation (group CAST), gypsum master casts were
manufactured and digitalised using the same desktop scanners. Virtual
datasets were superimposed by best fit algorithm, and accuracy was
analysed by calculating the Euclidean distances (ED) to the REF
(Geomagic Qualify). Statistic was determined (Kruskal-Wallis H test, Mann-Whitney U post hoc analysis, two-sample Kolmogorov-Smirnov test, p < 0.05).
Results
ZZ
showed for positive deviations superior accuracy for IMP than for CAST.
PE and PVS-I showed superior accuracy than PVS-D. D810 showed partially
significant better performance with PVS-I and PVS-D than ZZ.
Conclusions
The
partially digital workflow by digitalisation of the impression can be
used for clinical indications of small-span fixed dental prostheses.
However, for this indication, the impression material and the desktop
scanner are more decisive for the accuracy of virtual model datasets.
Clinical relevance
Despite
the rapid advancement of the computer-aided technology for dental
therapy purposes, the implementation of this technique is not as fast as
the technical development. In order to combine the well-established
procedure to use elastomeric materials for a conventional impression and
to avoid the drawbacks of casting it by gypsum, the digitalisation of
the impression itself by a desktop scanner may be a logical procedure as
an access point to the digital workflow. However, there is only limited
information about the accuracy of this partially digital workflow by
the digitalisation of modern impression materials in comparison to the
well-known process of indirect digitalisation of gypsum casts.
Comments