Mechanical properties of 3D-printed prosthetic materials compared with milled and conventional processing: A systematic review and meta-analysis of in vitro studies
Journal of Prosthetic Dentistry
Published:August 05, 2022DOI:https://doi.org/10.1016/j.prosdent.2022.06.008
Abstract
Statement of problem
Three-dimensional (3D) additive manufacturing (AM) is an evolving technology in dentistry,
proposed as an alternative to subtractive milling manufacture (MM) or conventional
processing. However, a systematic review of the use of AM technology instead of milling
or conventional processing is lacking.
Purpose
The purpose of this systematic review and meta-analysis was to evaluate the mechanical
properties of 3D-printed prosthetic materials compared with MM and conventional techniques.
Material and methods
An electronic search of the literature was conducted on the MEDLINE (via PubMed),
Scopus, and Web of Science databases. The inclusion criteria were in vitro studies
published in the last 5 years, in English or Italian, and with 3D AM printed dental
prosthetic materials. Data extraction was focused on dental prosthetic materials (ceramics,
polymers, and metals) and their mechanical properties: flexural strength, fracture
load, hardness, roughness, removable partial denture (RPD) fit accuracy, trueness,
marginal discrepancy, and internal fit. Data considered homogenous were subjected
to meta-analysis using the Stata17 statistical software program (95% confidence interval
[CI]; α=.05). Since all variables were continuous, the Hedge g measure was calculated.
A fixed-effects model was used for I2=0%, while the statistical analysis was conducted using a random-effects model with
I2>0%.
Results
From a total of 3624 articles, 2855 studies were selected, and 76 studies included
after full-text reading. The roughness of AM-printed ceramics generally increased
compared with that of conventional processing while the marginal discrepancy was comparable
both for ceramics and polymers. The flexural strength, hardness, and fracture load
of AM-printed polymers were statistically lower than those of the conventional group
(P<.05). No significant difference was detected in terms of hardness, roughness, marginal
discrepancy, fracture load, trueness, or internal fit between the AM and MM techniques
(P>.05). Milling techniques showed significantly higher values of flexural strength
(Hedge g=-3.88; 95% CI, -7.20 to -0.58; P=.02), also after aging (Hedge g=-3.29; 95% CI, -6.41 to -0.17; P=.04), compared with AM printing.
Conclusions
AM is comparable with MM in terms of mechanical properties, in particular with polymeric
materials. The flexural strength of AM-printed prostheses is lower than with conventional
and MM techniques, as are the parameters of hardness and fracture load, while the
marginal discrepancy is similar to that of MM and conventional techniques. AM prostheses
are commonly used for interim crowns and fixed partial dentures, as their rigidity
and fracture resistance cannot support mastication forces for extended periods. More
comparative studies are needed.
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