Abstract
Statement of problem
A digital workflow in fixed prosthodontics may use a 3D printer to obtain a cast for
porcelain application. Standards exist that define the accuracy of traditional casts,
but the accuracy requirements of 3D-printed casts have not been defined.
Purpose
The purpose of this retrospective study was to investigate how the accuracy of 3D-printed
casts affected prosthesis fit and whether they correctly reproduced interproximal
contacts.
Material and methods
Copings with different die spacings were used to test different 3D-printed casts of
the same dental arch. The accuracy of the 3D casts was assessed by imaging and comparing
the resulting standard tessellation language (STL) files with the original through
a matching software program. Accuracy scores were then correlated with a score measuring
how well the copings fit the casts. The first data set was obtained from a patient
receiving restoration of the 4 maxillary incisors. The teeth were prepared, the dental
arch was imaged intraorally, and 10 resin casts were printed with four 3D printers.
Two sets of 4 zirconia test copings were prepared, and 3 clinicians assessed their
fit on each cast. A further set of casts was created from a second patient requiring
prosthetic restoration for 5 adjacent teeth to assess whether undersizing affected
the best fit of the copings on their dies.
Results
The clinical scores and accuracy scores did not correlate. The results suggested that
printed dies showing a certain degree of undersizing might provide a better fit than
those showing better correspondence to the actual anatomic structure. The oversized
dies were the worst. Only 7 of 17 casts being assessed were deemed suitable for veneering
of the copings. The undersized casts tested clinically better than casts printed by
using the same printer under standard settings.
Conclusions
This retrospective study indicated that 3D-printed casts that do not allow copings
to fit appropriately usually show mean excess oversizing. Axially undersizing the
printed dies on casts might allow a better fit of copings to be veneered.
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Article info
Publication history
Published online: January 14, 2021
Footnotes
Conflict of interest: Eng. D.P. is an employee of IDI Evolution s.r.l. which owns one of the 3D printers used in this study. Dr D.A.D.S. and Dr G.B.G. are consultants for IDI Evolution s.r.l.
Identification
Copyright
© 2020 by the Editorial Council for the Journal of Prosthetic Dentistry.
