Factors affecting flexural strength of 3D‐printed resins: A systematic review

Abstract

The strength of 3D-printed resins is affected by different factors, but review articles clarifying these factors are limited. This review lists the factors affecting the strength of 3D-printed resins and the possible correlations between them to answer the study question: What are the factors affecting the flexural strength of 3D-printed resins? Methods: A database search (PubMed, Google Scholar, and Scopus) was performed, limited to English-language publications between 2010 and February 1, 2022. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used for study selection. The modified Consolidated Standards of Reporting Trials (CONSORT) checklist was used to determine the risk of bias of the included studies in this review. The data analysis was descriptive due to the presence of many variables in the included studies. Results: Out of 123 studies, 26 were reviewed for full-text analysis, and 19 met the inclusion criteria and were thus included in this systematic review. The included studies were divided according to the investigated resin: 5 studies tested provisional restorations, seven tested denture base resins, 2 tested occlusal devices, 3 tested orthodontic appliances, 1 tested denture teeth, and 1 tested surgical guide resins. These studies investigated the flexural strength of 3D-printed resins, with different factors, such as reinforcement with fillers or nanofillers; printing orientation, angulation, and directions; post-polymerization time and temperature; third-party printing (switching between printers and materials); printing layer thickness; and post-printing rinsing time. Most factors significantly affected the flexural strength of 3D-printed resin. Conclusions: The strength of 3D-printed resins could be improved with one or more of the following factors: filler or nanofiller addition; printing orientation, angulation, or directions; printing layer thickness; and post-polymerization time and temperature. However, further studies combining these factors are recommended. K E Y W O R D S3D printing, additive manufacturing, flexural strength, prosthodontics, provisional restorations 3D printers are now easy to use, consistent, inexpensive, and smaller and lighter than before. 1 They can produce complex or multiple structures at the same time. 2,3 Commonly used 3D printers in the dental field are based on stereolithography (SLA) or digital light processing (DLP) technology. In both methods, the object is built in layers from a photopolymer. In SLA, a laser light track is used to polymerize the resin, whereas, in DLP, a digital projector screen flashes light through the entire layer to build the 3D structures. 3,4 The photopolymer resin consists of 75% oligomers, 25% monomers, and photopolymerization initiators, which, when exposed to ultraviolet light, cleave primary radicals that react with the oligomers and monomers and lead to polymerization. 5 3D-printing technology can fabricate several objects simultaneously, with less wasted material. It can also prod...

Antibiofilm Activity of 3D-Printed Nanocomposite Resin: Impact of ZrO2 Nanoparticles

“…Additionally, dynamic loading was not present, and the heat cycling ageing only accurately represented six months of intraoral use. Different antifungal agents [ 54 ] and nanoparticles at different concentrations, with different printing orientations [ 55 ] should be investigated. This report also suggests the use of various additional 3D-printed materials assembled in a denture configuration and subjected to mechanical and thermal stresses that are similar to those found in the intraoral cavity.…”

Fracture Load of 3D-Printed Interim Three-Unit Fixed Dental Prostheses: Impact of Printing Orientation and Post-Curing Time

“…Thermocycling was performed on the materials tested to expose them to fatigue and simulate the oral conditions [ 28 ]. This process created stresses corresponding to the mechanical stresses in the mouth of IFPDs due to the abrupt change in temperature when they are submerged in the baths [ 39 ].…”

“…After printing, the specimens are in a green state and contain uncured monomer, which requires further polymerization in accordance with the manufacturer’s recommendations regarding the post-curing process [ 20 , 28 , 32 , 48 , 49 ]. Each company has its specific time required to ensure even polymerization of printed objects, which depends on the printing technology and curing device [ 20 , 28 , 50 ].…”

“…Simoneti et al [ 19 ] reported that conventional resins have high strength. Although the strength of 3D-printed resins varies with composition, improving strength through printing parameter modifications was suggested [ 28 ], and one ester-based and one PMMA-based polymer were chosen for this study. However, due to limited information on ASIGA composition, comparing both materials based on material compositions was difficult.…”

“…When using 3D printing, numerous factors in terms of printing parameters should be considered that might influence the printed objects’ properties [ 28 ]. Among these factors are printing orientations [ 31 ], post-curing time [ 32 ], and printing technology [ 8 , 33 , 34 ].…”