Abstract
Statement of problem
Novel 3-dimensionally printed resin and milled polymethyl methacrylate materials have
been marketed for computer-aided design and computer-aided manufacturing (CAD-CAM)
denture base fabrication. However, information on the flexural strength of digitally
fabricated denture base material is limited, and little is known about how they are
affected by a hard-reline procedure.
Purpose
The purpose of this in vitro study was to assess the flexural strength of 6 digitally
manufactured denture base materials and to assess the effect of a hard-reline procedure
on their flexural strength.
Material and methods
A total of 140 strips of denture base material were fabricated from a conventional
heat-polymerized polymethyl methacrylate (L199), 3 brands of milled polymethyl methacrylate
(IBC, DSL, and ADH), and 3 brands of 3D-printed resin (DFD, ADB, and DrFD) (n=20).
Ten specimens in each group did not receive any treatment, and 10 were relined with
a hard-reline material (ProBase Cold Trial Kit). Specimens were then subjected to
a 3-point flexural strength test using a universal testing machine at a crosshead
speed of 5.0 mm/min. A 1-way ANOVA test followed by the Tukey multiple comparison
test was used to detect the difference in flexural strength and the strain at fracture
of the different types of denture base materials (α=.05). The comparison of flexural
strength between with and without hard-reline was analyzed using an unpaired t test (α=.05).
Results
All materials, with or without the hard-reline, met the International Organization
for Standardization (ISO) 20 795-1:2013 standard for flexural strength (65 MPa). The
milled materials (DSL>IBC≈ADH) showed higher flexural strength than the 3D-printed
or conventional materials (DrFD>DFD≈ADB≈L199) without a hard-reline. No statistical
difference in flexural strength was found among the hard-relined denture base materials
(P=.164). All 3 milled materials showed reduced flexural strength after relining, while
the relined conventional (L199) and 3D-printed materials (DFD and ADB) showed notably
higher flexural strength; printed DrFD showed no significant difference (P=.066). In terms of strain at fracture, the milled materials displayed higher values
than those of the conventional or 3D-printed materials (P<.05).
Conclusions
All digitally fabricated denture base materials were within acceptable limits for
clinical use, even after hard relining. Flexural strength was highly dependent on
the type of material. Hard relining affected the flexural strength of most of the
digitally fabricated denture base materials.
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Article info
Footnotes
All authors declare no conflicts of interest.
Identification
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© 2023 by the Editorial Council for The Journal of Prosthetic Dentistry.
