Novel Surface Modification of Dental Prosthetic Replacements by Gaseous Plasma

Within the project important challenges regarding biomechanical properties of dental materials in clinical dentistry will be addressed. An exceptionally multidisciplinary project team will focus on i.) the development of rapid and innovative surface modification routes that will allow a reliable and durable bond between dental cement and tooth replacements, without the need to use chemicals that are toxic to the environment and humans. Surface characteristics of tooth replacements, such as morphology, wettability, and surface chemistry, significantly influence the adhesion of dental cements. In order to alter physiochemical properties of tooth replacement surfaces, such as prosthetic posts and cores, crowns, and bridges, made by precision casting, CAD-CAM, or 3D printed, various surface modification techniques can be applied, most commonly sandblasting with Al2O3 and hydrofluoric (HF) acid etching. However, these treatments have adverse negative effects on human health, and they also negatively affect the mechanical properties of tooth replacements. In addition, such pre-treated surfaces still require the use of silane coupling agents as adhesion promoters. Within the project, ceramic and composite, i.e., metal-ceramic tooth replacements, will be treated with atmospheric plasma in order to improve the direct adhesion of dental cements. Such treatment will present a clean, user-friendly, and cost-effective approach for modifying tooth replacement surfaces before cementation. For this purpose, collaboration with dental experts from the Department of dental prosthetics, Medical Faculty, University of Ljubljana is foreseen. Project partners, coordinated by prof. dr. Ksenija Rener Sitar, dr. dent. med., who is a specialist in prosthodontics and board-certified by the American Board of Orofacial Pain, will perform highly valuable and necessary clinical studies with as-prepared plasma-treated surfaces of tooth replacements. Due to the beneficial effects of plasma treatment procedures for various dental materials, the second part of the research will also be focused on ii.) improvement of biocompatibility, in terms of ion leakage and antibacterial properties of widely used titanium alloy (Ti-6Al-4V) as a dental implant material by optimized low-pressure plasma surface treatment, which will alter surface characteristics of Ti-6Al-4V, in particular morphology and wettability that are crucial for effective antibacterial activity. In addition, plasma treatment will cause the formation of a dense oxide layer on the surface of Ti6Al4V, which will prevent the release of allergenic and toxic metal ions into the human body. This will represent a huge breakthrough in the design of other types of implants because commonly used methods (sandblasting, acid etching, etc.) for modification of Ti alloys before implantation often results in destroying of naturally occurring TiO2 layer on these surfaces, which acts as a protective barrier between implant and biological environment. This can lead to surface exposure of vanadium (V) and aluminum (Al); especially V may lead to implant failure by hindering the normal bone deposition process and eliciting an inflammatory response or even osteolysis. Challenging optimization of low-pressure plasma treatment and development of dense nanostructured oxide layer on the surface of Ti-based materials will be addressed in a particularly multidisciplinary approach; the research will combine material science, physics and biomedical engineering. The success of the project is highly expected, since PI and project partners (Institute Jožef Stefan and Faculty of electrotechnics, University of Ljubljana) are well experienced in the synthesis of nanostructured surfaces by wet chemistry methods and plasma treatment of biomaterials.