Evaluation of various monofunctional monomers for the development of fracture tough dental materials exhibiting a low crosslink density

• Published in: European polymer journal Vol. 219; p. 113332
• Main Authors: Fässler, Pascal, Grob, Benjamin, Lamparth, Iris, Omeragic, Sadini, Rist, Kai, Vidal, Loïc, Lalevée, Jacques, Catel, Yohann
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 16.10.2024
• Subjects: 3D printing; Block copolymers; Dental materials; Fracture toughness; Photopolymerization; Dental materials; Photopolymerization; 3D printing; Block copolymers; Fracture toughness
• ISSN: 0014-3057
• DOI: 10.1016/j.eurpolymj.2024.113332

[Display omitted] •Low crosslink density materials based on eight monofunctional monomers were prepared.•The addition of a triblock copolymer led to an increase of the fracture toughness.•The nature of the monofunctional monomer strongly influenced the mechanical properties.•Five monomers are promising for 3D printing applications. 3D printing of fracture tough dental materials that additionally exhibit excellent mechanical properties is challenging. Nowadays, most of the 3D printing dental materials contain a mixture of highly reactive dimethacrylates. The corresponding printed materials exhibit a high crosslink density and are particularly brittle. They are therefore not suitable for additive manufacturing of fracture tough denture bases. Recently, an efficient technology based on the combination of a urethane dimethacrylate macromonomer with a monofunctional monomer and a poly(ɛ-caprolactone)-polydimethylsiloxane-poly(ɛ-caprolactone) triblock copolymer was developed. Materials exhibiting a low crosslink density, excellent mechanical properties, and high fracture toughness were obtained. In this article, further developments of this highly efficient technology are described. A wide range of monofunctional monomers (both methacrylates and acrylates) was evaluated in this system. It was shown that the structure of the selected monofunctional monomer has a strong influence on the mechanical properties (flexural strength and modulus) as well as on the fracture toughness of the light cured materials. Thanks to the formation of nanostructures, a strong increase of fracture toughness was obtained upon addition of the toughening agent (poly(ɛ-caprolactone)-polydimethylsiloxane-poly(ɛ-caprolactone) triblock copolymer). The most promising materials were the ones based on the following monofunctional monomers: 2-phenoxyethyl methacrylate, (octahydro-4,7-methano-1H-indenyl)methyl acrylate, isobornyl acrylate, tetrahydrofurfuryl methacrylate and 4-tert-butylcyclohexyl acrylate. Indeed, these materials exhibited excellent mechanical properties (90.0 ± 3.8 MPa < flexural strength < 102.6 ± 4.7 MPa; 2402 ± 90 MPa < flexural modulus < 2714 ± 68 MPa) combined with high fracture toughness (1.89 ± 0.06 MPa m1/2 ≤ maximum stress intensity factor (Kmax) ≤ 2.18 ± 0.08 MPa m1/2; 418 ± 14 J m−2 ≤ work of fracture (Wf) ≤ 591 ± 25 J m−2). The measured Kmax and Wf were even significantly higher than the values reported for Probase Hot (Kmax = 1.44 ± 0.18 MPa m1/2; Wf = 270 ± 30 J m−2), a clinically proven and well-established PMMA based denture base material from Ivoclar. The successful DLP 3D printing of a monoblock denture using the most promising formulation confirmed the great potential of this technology for the development of 3D printing fracture tough denture bases.