Modifying dental composites to formulate novel methacrylate-based bone cements with improved polymerisation kinetics, and mechanical properties

Performance of low shrinkage Bis-EFMA based bulk-fill dental resin composites

OBJECTIVES

The purpose of this study was evaluating the performance of new Bis-EFMA based bulk-fill composites with common methacrylate based composites and commercial dental composites.

METHODS

The Bis-EFMA monomer was synthesized and the novel Bis-EFMA based bulk-fill composites were prepared. The resin composite samples were co-cultured with human gingival epithelial cells and human dental pulp stem cells to test the biocompatibility. The edge adaptation was observed under a combination of stereoscope and scanning electron microscope. The internal hardness was measured using a Vickers microhardness tester after one-time filling of cavities prepared in extracted teeth. After friction and wear test on the surface of the resin composites, the surface morphology and volume wear of each group were measured by the optical profilometer. The color stability was measured by a colorimeter.

RESULTS

Direct contact with human gingival epithelial cells and human dental pulp stem cells did not cause significant changes in their growth density and morphology, indicating good biocompatibility of Bis-EFMA group (p > 0.05). The continuous margin proportion of the Bis-EFMA group was as good as commercial bulk-fill composites (p > 0.05). The sectional microhardness results showed that the Bis-EFMA group had the highest microhardness. After the friction and wear test, the volume wear of the Bis-EFMA group was minimal, indicating its good wear resistance and mechanical strength. Color changes in all resin groups after 28 days of immersion were within the clinically acceptable range.

SIGNIFICANCE

The addition of Bis-EFMA demonstrated excellent biocompatibility, edge adaptation and color stability comparable to commonly used clinical bulk-fill composites, along with preferable mechanical strength, friction and wear resistance. Bis-EFMA based bulk-fill composites have the potential to be employed as a bulk filling material in commercial dental composite applications.

Highly Reinforced Acrylic Resins for Hard Tissue Engineering and Their Suitability to Be Additively Manufactured through Nozzle-Based Photo-Printing

Mineralized connective tissues represent the hardest materials of human tissues, and polymer based composite materials are widely used to restore damaged tissues. In particular, light activated resins and composites are generally considered as the most popular choice in the restorative dental practice. The first purpose of this study is to investigate novel highly reinforced light activated particulate dental composites. An innovative additive manufacturing technique, based on the extrusion of particle reinforced photo-polymers, has been recently developed for processing composites with a filler fraction (w/w) only up to 10%. The second purpose of this study is to explore the feasibility of 3D printing highly reinforced composites. A variety of composites based on 2,2-bis(acryloyloxymethyl)butyl acrylate and trimethylolpropane triacrylate reinforced with silica, titanium dioxide, and zirconia nanoparticles were designed and investigated through compression tests. The composite showing the highest mechanical properties was processed through the 3D bioplotter AK12 equipped with the Enfis Uno Air LED Engine. The composite showing the highest stiffness and strength was successfully processed through 3D printing, and a four-layer composite scaffold was realized. Mechanical properties of particulate composites can be tailored by modifying the type and amount of the filler fraction. It is possible to process highly reinforced photopolymerizable composite materials using additive manufacturing technologies consisting of 3D fiber deposition through extrusion in conjunction with photo-polymerization.