Abstract
Statement of problem
The lack of passive fit in implant-supported restorations can lead to mechanical and
biological complications and compromise the longevity of the prosthesis. The manufacturing
technique and evaluation site are factors that may affect the passive fit of multiunit
screw-retained implant frameworks. However, scientific information regarding this
issue is lacking.
Purpose
The purpose of this in vitro study was to investigate the effect of manufacturing
technique and evaluation site on the passive fit of multiunit screw-retained implant
frameworks.
Material and methods
Two multiunit implant analogs were placed into the right second premolar and second
molar sites of a mandibular typodont model. A total of 50 3-unit Co-Cr frameworks
were fabricated with 3 indirect (conventional technique, polymethyl methacrylate milling,
stereolithography) and 2 direct techniques (selective laser melting and soft alloy
milling). The patterns obtained by indirect techniques were subsequently cast. The
Sheffield test was used for the assessment. Digital images of the sites were obtained
by using a stereomicroscope at ×40 magnification, and the measurement points (n=10
for each site) were examined to record the vertical marginal discrepancy values (μm)
with the aid of a measuring software program. The collected data were subjected to
the 2-way ANOVA and Tukey honestly significant difference test (α=.05).
Results
The influence of the manufacturing technique (variable 1) on the vertical marginal
discrepancy values was statistically significant (P<.001). However, the evaluation site (variable 2) (P=.097) and the interaction of the variables (P=.960) were not statistically significant. The lowest misfit values were observed
for selective laser melting (74.2 ±20.5 μm) followed by stereolithography (92.8 ±23.9
μm), soft alloy milling (108.4 ±12.0 μm), polymethyl methacrylate milling (116.7 ±17.0
μm), and conventional technique (137.5 ±18.9 μm). The vertical marginal discrepancy
values of the selective laser melting group were significantly lower than those of
all other groups (P<.05).
Conclusions
The manufacturing technique significantly affected the passive fit. selective laser
melting–fabricated frameworks demonstrated superior fitting accuracy. Among the indirect
techniques, stereolithography-fabricated frameworks revealed the lowest misfit values.
The vertical marginal discrepancy values of all manufacturing groups were within the
range of clinical acceptability (<150 μm).
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Article info
Publication history
Published online: July 19, 2021
Publication stage
In Press Corrected ProofFootnotes
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
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© 2021 by the Editorial Council for the Journal of Prosthetic Dentistry.
