Development of Novel High-aspect-ratio Nanofillers for Dental Composites

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DESCRIPTION (provided by applicant): The objective of this proposal is to develop novel fiber-like ceramic nanofillers that will significantly outperform the existing nanofillers used in dental composites. To date, nanofillers, such as silica or silicate nanoparticles, have provided only incremental improvements in mechanical properties and clinical behavior as compared to microfilled composites. We propose to synthesize fiber-like hydroxyapatite (HA) and silicon carbide (SiC) fillers for dental composites using biomimetic and engineering approaches. The rationale for using such materials are: 1) the mechanical strength of ceramic nanofibers and nanoplates is in inverse proportion to the square root of their diameter or thickness and will reach the maximum/theoretical value in nanoscale; and 2) the load transfer is roughly proportional to the aspect ratio up to a maximum value. Such fillers will be much stronger and can also carry more loads in composites. Low temperature plasmas, partially ionized gases, will be applied to functionalize or coat the above nanofillers to improve their dispersion property and interfacial bonding to resin matrix. While functionalization using silane is limited and dependent on the substrate materials, plasma functionalization can provide a variety of functional groups on different substrates. The plasma functionalized HA and SiC, as well as commercial ceramic fillers (control), will be incorporated into the resin matrix to make dental nanofilled composites. The mechanical properties and durability of the composite and the biocompatibility of both nanofillers and composites will be evaluated. It is hypothesized that the surface modified high aspect ratio ceramic nanofillers will be much stronger, will effectively improve the composite mechanical properties and durability, and have better biocompatibility as compared to the existing nanofillers. The proposed work will lay the pioneering foundation for development of novel fiber-like ceramic nanofillers for dental composites with improved mechanical properties, durability, and/or biocompatibility. Moreover, the knowledge gained in this project will benefit research in other fields, such as hard tissue engineering and development of replacement materials/constructs for these tissues. Caries continues to be a common problem in dentistry and the primary treatment to restore the tooth to function is repair with an inert material, such as dental composites. The large population with caries and the inferior mechanical properties of the existing microfilled and nanofilled dental composites underscore the significance of the proposed research.