Special Issue "Dental Materials"

Guest Editor
Prof. Dr. Jorge Perdigão
University of Minnesota, Department of Restorative Sciences, Division of Operative Dentistry, 515 SE Delaware St, 8-450 Moos Tower, Minneapolis, MN 55455, USA
Website: http://www.dentistry.umn.edu/facultystaff/faculty_bios/m-p/Perdigao,_Jorge/home.html
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Dear Colleagues,

Dental research has been transitioning gradually from the classical Restorative Dentistry to Regenerative Dentistry. Regeneration of a functional tooth is a promising strategy for replacing an irreversibly diseased tooth. Pulp-like tissue can now be regenerated in root canal space by stem cells and give rise to odontoblast-like cells producing dentin-like tissue. Three-dimensional porous scaffolds made of mineralized type I collagen mimic the composition of extracellular matrix ofbone and can therefore have the potential of being used as a biomimetic graft material. Additionally, the role of RNA interference (RNAi) and RNA activation (RNAa) may prove to be crucial to treat or prevent dental anomalies and periodontal disease.

The role of metalloproteinases (or MMP’s) inhibitors in preventing the degradation of dentinal collagen fibers has been recently highlighted in dentin adhesion. Other promising areas of research in dental adhesion are the application of colloidal platinum nanoparticles, and guided tissue mineralization to re-mineralize areas etched by phosphoric acid but not infiltrated by the adhesive.

Some of the dental materials recently introduced - low-shrinkage resin composites and Y-TZP-based fixed prostheses - have changed some of the classical concepts of clinical dentistry.

For the first time in 40 years, dentists are using a non-BisGMA resin composite. Shrinkage stresses are reduced with the new silorane-based resin composites. The relevance of using low- or no-shrinking composite materials is that internal stresses occur during the polymerization of all dental composites due to a volumetric contraction. These shrinkage stresses may cause interfacial failures between the restoration and the tooth structure.

Yttria-stabilized tetragonal zirconia (Y-TZP) and titanium implants have been increasingly used in Dentistry. Y-TZP is used as the infrastructure for crowns, bridges and implant abutments. Research in Clinical Orthopedics has shown that Y-TZP used in hip arthroplasties may undergo transformation under mechanical and/or hydrothermal stress, with degradation of mechanical and tribologic properties. It is not known if these alterations also occur in Y-TZP dental restorations.

Jorge Perdigão, Ph.D.
Guest Editor

Related Special Issue

Dental Materials in Materials

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• nanotechnology in Dentistry
• biocompatibility
• dental pulp & regeneration
• scaffold materials
• stem cells in dentistry
• dental tissue bioengineering
• RNA interference
• dentin ultrastructure & adhesion
• dentin MMP's & collagen
• non-shrinking composite materials
• biodegradation of Y-TZP
• optimization of dental implant surfaces

Type of Paper: Review
Title: Biological Interaction of Bulk and Nano Zirconia for Biomedical Devices
Authors: Giulio Maccauro¹, Pierfrancesco R. Iommetti², Paolo F. Manicone², Luca Raffaelli² and Gabriella Calviello³
Affiliations: ¹ Institute of Orthopaedics and Traumatology, Catholic University, L.go F. Vito, 1 00168 Rome, Italy
² Institute of Clinical Dentistry, Catholic University, L.go F. Vito, 1 00168 Rome, Italy; E-Mail: pierfrancesco.rossi1@tin.it (P.R.I.)
³ Institute of General Pathology, Catholic University, L.go F. Vito, 1 00168 Rome, Italy
Abstract: Zirconium oxide and zirconia toughened alumina have been proposed as materials for medical device. These materials were proposed firstly for orthopaedic prostheses and successively for other purposes such as dental restorations. Zirconia biocompatibility was studied in vivo and in vitro. Bone and muscle reaction after insertion of a zirconia sample was evaluated showing no adverse response. Tissue reaction was influenced by the specimen, but in general bulk samples didn’t result to be citotoxic. Zirconia was not found able to generate mutation or degeneration in cultured cells and fibroblasts showed great ability to grow on zirconia surface. Moreover zirconia showed less proinflammatory properties if compared with other biocompatible specimens such as titanium and high density polyethylene. Nowadays zirconia is proposed as a material for Fixed Partial Dentures with 5 years of clinical follow up. In the last years also zirconia osteointegrated implants were proposed in order to achieve better aesthetical results in dental rehabilitations. ZrO₂ dental implants seem to achieve osteointegration comparable with titanium, both in vitro and in vivo. Some pilot studies showed that this material is suitable for this kind of devices. More studies are necessary to evaluate possible unfavourable aspects in using ZrO₂ as a dental restorative and implantological material. New classes of ceramics Zirconia Toughened Alumina (ZTA), and more recently Zirconia Plateled Toughened Alumina (ZPTA) combining the mechanical properties of alumina and zirconia have improved the use of these ceramics in biomedical applications (especially in orthopaedic surgery). In vitro tests demonstrated the absence of citotoxicity and mutagenic and carcinogenic effects of these materials when co-cultured with cells. In vivo tests of bulk materials showed the absence of local and systemic toxicity after implantation into bone. There were no statistically significant differences in direct bone contact when ZPTA was compared to alumina and zirconia ceramics. The advent of ZPTA ceramics with the hardness, inertia and stability of alumina and the durability and strength of zirconia ceramics will drive the development of innovative ceramic devices.