PHOTOINITIATOR TYPES AMONG A VARIETY OF 3D PRINTING MONOMERS

Abstract

A variety of manufacturing techniques have been used throughout the history of dentistry, in order to fabricate indirect restorations. Formative processes (pouring or pressing items into molds) are used when making conventional dentures, or when pressing ceramics. Recently, subtractive fabrication methods have enabled clinicians to mill a wide variety of ceramic and resin-based blanks directly into final forms, fitting the oral structures with high degrees of precision. Examples of older additive techniques include wax buildups to establish missing tooth structure for fabrication of subsequent cast restorations and the manual layering of powdered porcelains for development of ceramic facings on metallic substrates, or for ceramic veneers themselves. Tremendous advancements have been made in the field of 3D digital printing for many industrially based applications. Advances in research and development have resulted in tabletop 3D printers that produce rapid prototype specimens having very high accuracy and surface feature details. Recently, these advances have resulted in the manufacture and availability of a wide variety of 3D digital printers that dental offices now use to directly fabricate a wide range of restorative appliances (denture bases and teeth, temporary restorations, splints) as well as ancillary devices (impression trays, surgical implant guides, casts, try-in set-ups, and stents). Contemporary dental 3D printing typically involves use of near or true ultraviolet radiation (405 nm & 385 nm, respectively) in order to fabricate the basic desired form from a vat of photo-polymerizable monomers. Subsequent to initial form fabrication, the specimen is alcohol-washed of excess surface monomer, and is then subjected to an additional exposure of strong near/UV light, in order to maximize the polymerization process and provide optimal physical properties, as well as to minimize cytotoxicity resulting from leaching of unreacted, residual monomer within the bulk of the as-printed item.