Evaluation of internal fit of press ceramic and porous structured cobalt–chromium crown fabricated by additive manufacturing

Abstract

Background: The purpose of this in vitro study is to fabricate a novel metal–ceramic prosthesis
with a porous structure, to compensate for the disadvantages associated with the design of existing
prostheses, and to measure the internal fit of this prosthesis.
Materials and Methods: In this in vitro study, the mandibular first molar was scanned from the
dental computer‑aided‑design to design a 3 mm porous structure frame. The frame was produced
using the lamination method and fired in a pressed ceramic. For comparison, pore‑free specimens
were fabricated by selective laser sintering (SLS) as described above, and porous specimens were
fabricated by casting (total n = 30). The internal fit was then measured using a digital microscope (at
100× magnification), and the data were analyzed using one‑way ANOVA (α = 0.05).
Results: The total mean internal discrepancies for each group were 42.32 ± 22.50 μm for the
porous structure SLS group (PS‑group), 107.54 ± 38.75 μm for no‑porous casting group (group),
and 121.36 ± 50.19 μm for the no‑porous SLS group (group), with significant differences (P < 0.05)
among all groups.
Conclusion: The internal discrepancies of porous structure crown fabricated by SLS were smaller
than that of no‑porous crown fabricated by casting and SLS. Based on these laboratory findings,
further studies should be conducted to evaluate the feasibility of the newly designed porous
structure and press ceramic prosthesis to determine whether they can be applied in clinical practice.
Key words: Dental crown; internal fit, metal–ceramic restorations, porosity, prosthesis design