Biomedical applications of polymer-composite materials: a review

Photopolymerization kinetics of multifunctional monomers

Three-dimensional (3D) printing enables the production of anatomically matched and patient-specific devices and constructs with high tunability and complexity. It also allows on-demand fabrication with high productivity in a cost-effective manner. As a result, 3D printing has become a leading manufacturing technique in healthcare and medicine for a wide range of applications including dentistry, tissue engineering and regenerative medicine, engineered tissue models, medical devices, anatomical models and drug formulation. Today, 3D printing is widely adopted by the healthcare industry and academia. It provides commercially available medical products and a platform for emerging research areas including tissue and organ printing. In this review, our goal is to discuss the current and emerging applications of 3D printing in medicine. A brief summary on additive manufacturing technologies and available printable materials is also given. The technological and regulatory barriers that are slowing down the full implementation of 3D printing in the medical field are also discussed.

https://iopscience.iop.org/article/10.1088/1758-5090/aa7279/pdf

Current and emerging applications of 3D printing in medicine.

Statement of problem. Fracture strength of denture base resins is of great concern, and many approaches have been used to strengthen acrylic resin dentures. Purpose. This study measured the effect of 5 fiber strengtheners on the fracture resistance of denture base acrylic resin material. Impact strength, transverse strength, deflection, and elasticity modulus values of a heat-polymerized denture base resin (Trevalon), reinforced with glass, carbon, thin Kevlar, thick Kevlar, and polyethylene fibers in woven form were studied. Material and methods. One hundred acrylic resin test specimens reinforced with woven fibers were fabricated. The control group consisted of 20 specimens with no fiber reinforcement. For the impact strength test, a Charpy-type impact tester was used. Transverse strength was assessed with a 3-point bending test by using a screw-driven mechanical testing machine. Ten specimens were used for each test. Results. The highest impact test values were produced by polyethylene-reinforced group, and the lowest values were obtained from specimens containing no fibers. There were significant differences among the test groups, but no significant differences in transverse strength were found. The lowest transverse strength values were obtained for specimens strengthened with polyethylene fibers, which also insignificantly decreased transverse strength of the acrylic resin. Conclusion. The impact strength of denture base acrylic resins was increased with fibers in woven form. Tested fibers did not have a significant effect on the transverse strengths. (J Prosthet Dent 1999;81:616-20.)

Effect of five woven fiber reinforcements on the impact and transverse strength of a denture base resin.

The currently used commercial self-etching enamel-dentin adhesives and restoratives composites are mainly based on a mixture of various monofunctional and cross-linking dimethacrylates. New developments of enamel-dentin adhesives concern the improvement of technique insensitivity and storage stability. Improvements of restorative composites are focused on the reduction of the polymerisation shrinkage, as well as the improvement of wear resistance, biocompatibility, and processing properties. In the past five years, many research efforts have been carried out to develop new monomers and tailor-made components for filling materials, such as fillers or initiators. New phosphonic acid ether acrylates and cross-linking bis(acrylamide)s enable the preparation of self-etching enamel-dentin adhesives with improved storage stability. With free-radically polymerisable cyclic monomers, such as bicyclic cyclopropyl acrylates or cyclic allyl sulfides, low-shrinkage storage-stable restorative composites could be prepared. In case of the cationic polymerisable cyclic monomers, like siloxane-based cycloaliphatic epoxides, the lower curing rate, stronger exothermic effect and lower curing depth compared to dimethacrylate-based composites presently prevent their dental application. Designed methacrylates with tailor-made properties and sol-gel polycon-densates can also contribute to the improvement of the currently used restorative composites. Radical polymerisable dental materials are initiated by light curing and by redox initiator systems. Under acidic conditions amine containing initiator systems are deactivated by acid-base reaction. Non amine-based initiators have to be developed for acidic monomer containing dental materials. The use of discrete nano-filler particles mainly concerns the reinforcement and, in some cases, the increase of X-ray opacity of composite filling materials.

Recent Developments of New Components for Dental Adhesives and Composites

The relationship between Shore hardness of elastomeric dental materials and Young's modulus.

Soft linings are compliant, viscoelastic materials used to form all or part of the fit surface of a denture. Their complete function is debatable, but they serve to distribute the forces of mastication more evenly and to absorb energy. Other uses include obturators and maxillo-facial prostheses. This review will cover both the so-called 'permanent' soft-lining materials and temporary soft reline materials, often referred to as tissue conditioners.

S. Parker

Papers

The relationship between Shore hardness of elastomeric dental materials and Young's modulus.

Soft lining materials--a review.

Water absorption of methacrylate soft lining materials.

Polymeric Dental Materials

An experimental and theoretical study of the effect of sample thickness on the Shore hardness of elastomers