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Dr. Jirun Sun
Jirun Sun, Ph.D.

Jirun Sun, Ph.D.

Research Interests

  • Dental Resin Composites
  • Self-Healing
  • Nanotechnology
  • Tissue Engineering
  • Vinyl Ester Resins

Jirun Sun, Ph.D. Curriculum Vitae (PDF)

In 2013, Dr. Sun was awarded a NIH/NIDCR U01 Grant for his project “Novel Dental Composite Restorative Systems with Improved Service Life.” The information below details several projects developed from Dr. Sun’s original research. 

Current research projects:

Hydrolytically and enzymatically stable ether-based dental resinsDr. Sun research ether based dental resins

The short average service life of traditional dental composite restorative materials and increasing occurrence of secondary caries adjacent to composite restorations and sealants are necessitating the development of new, longer lasting compositions. Novel monomers and their polymers, reinforcing fillers, and adhesive components are needed. The goal of this research is to develop resin systems for use in restorations, sealants, and other dental services that are superior in properties and endurance to currently used bisphenol A glycidyl dimethacrylate/triethylene glycol di-methacrylate (Bis-GMA/TEGDMA) and urethane-dimethacrylate products.
Ether-based monomers and their polymers that were not susceptible to enzymatic or hydrolytic degradation were prepared and characterized. They showed no degradation under hydrolytic and enzymatic challenges, whereas the hydrolysis of ester links weakened contemporary resins within 16 days under these challenges. The success of the ether-based materials is promising in making durable systems that are subjected to long term biochemical and hydrolytic challenges in oral environments.

 

Self-healing dental resin composites

The purpose of this project is to design and develop a clinically applicable self-healing dental composite (SHDC). The value of resin-based dental restorations could be improved by increasing their service lives. One way to improve longevity is to obturate micro-cracks that form during or after the composite hardens in the dental cavity. Toward this end, we introduce here a new type of SHDC made with contemporary dental components plus two additional ingredients: a healing powder (HP) and a healing liquid (HL) that is enclosed within silica microcapsules. The hypothesis is that as micro-cracks develop, they will break the microcapsules in their propagation path, thereby releasing HL. This liquid will then dissolve and react with particles of HP exposed by the crack formation, forming an insoluble reaction product that fills and seals the cracks. The key factors to achieve this self-healing of cracks are discussed. The elastic modulus of a SHDC appeared to be satisfactory. The healing process was confirmed by means of mechanical, morphological, and chemical methods. The SHDC restored micro-cracks without external intervention, thereby showing potential for increasing the service lives of dental restorations. Importantly, this SHDC contains only clinically-tested, biocompatible materials, making it readily applicable.

NanotechnologyDr. Sun research nanotechnology

Objectives: The unique photo-catalytic activities (PCAs) of titanium dioxide nanoparticles (TiO2 NPs) made them attractive in many potential applications in medical devices. The objective of this study is to optimize the benefits of PCAs of TiO2 NPs through varying chemical structures of dimethacrylate resins.
Methods: TiO2 NPs were functionalized to improve the PCAs and bonding to the resins. The PCAs of TiO2 NPs were evaluated using electron paramagnetic resonance (EPR) and UV-vis spectroscopy to determine the amount of the radicals generated and the energy required for their production, respectively. The beneficial effects of the radicals were assessed through: 1) the improvement of degree of vinyl conversion (DC) and 2) modification of resin hydrophilicity. One-way ANOVA with a 95% confidence interval was used to indicate a significant difference between the experimental groups.
Results: EPR and UV-vis results clearly showed that the functionalization of TiO2 NPs enhanced PCAs in terms of generating radicals under visible light irradiation. The presence of the hydroxyl and carboxylic acid functionality played an important role in DC enhancement and hydrophilicity modification. The DC could be increased up to 22 % by adding only 0.1 wt% TiO2 NPs. Viscosity of the resins had minimal or no role in DC improvement through TiO2 NPs. In resins with abundant hydroxyl groups, radicals were more effective in making the resin more hydrophilic.  
Significance: Knowledge learned from this study will help formulating nano-composites with optimized use of TiO2 PCAs as co-initiators for photo-polymerization, additives for making super-hydrophilic materials and/or antibacterial agents.

Tissue engineeringDr. Sun research tissue engineering

Nanoscale surface features that mimic extracellular matrix are critical environmental cues for cell contact guidance and are vital in advanced medical devices in order to manipulate cell behaviors. Among them, nanogratings (line-and-space grating) are common platforms to study geometric effects on cell contact guidance, especially, cell alignment, but generally are one pattern height per platform. In this study, we developed a strategy to fabricate controlled substrates with a wide range of pattern shapes and surface chemistries and to separate surface chemistry and topography effects. As a demonstration of this strategy, six nanograting platforms on three materials were fabricated and applied to examine and differentiate the effects of surface topography and surface chemistry on cell contact guidance of murine preosteoblasts. All of the six platforms contained the same gradient in pattern height (0 nm to ≈ 350 nm). They were prepared using nanoimprint lithography and annealing for thermoplastic materials (low molecular weight polystyrene (PS) and polymethylmethacrylate (PMMA)) and photo-imprint for a thermoset material (a cross-linked dimethacrylate (DMA)). Each material contains two platforms that are only different in line-and-space pitches (420 nm or 800 nm). The DMA nanogratings had a reverse line-and-space profiles to those of the PS and PMMS nanogratings. Using these platforms, a full range of cell alignment, from randomly orientated to completely parallel to the grating direction was achieved. Results from focal adhesion assay and scanning electronic microscopy (SEM) indicated a change in cell-substrate contact from a non-composite state (full contact) to a composite state (partial contact between cell and substrate) as pattern height increased. These gradient platforms allowed for the separation of surface chemistry and surface topography to provide insight into the mechanisms responsible for cell contact guidance on nanopatterned surfaces.

Rapid photo-polymerization with controlled compositionsDr. Sun research photo polymerization

An assembly that delivers well-defined functional materials, clinically practical procedures to make these materials in situ, and appropriate analytical tools for chemical structure and kinetic studies is desirable, though currently unavailable. Herein, we introduce a system that addresses this need through the development and characterization of a cross-linking resin network, which is achieved through rapid, visible-light induced polymerization in a solvent-free environment. This resin network is the result of co-polymerization of a distyrenyl-monomer with a dimethacryl-monomer. Ninety percent of vinyl conversion is achieved in seconds. The polymerization rate is controllable by varying the intensity and duration of light exposure. In addition, an azeotropic composition is identified and confirmed through static end-point evaluation, sol-gel experiment, kinetic study, and mathematical modeling of data acquired via FTIR, real-time Raman and 1H NMR spectroscopies. These results yield opportunities for the design and development of new functional materials to be used in various applications.

Selected Publications (See NIH Public Access Listing)

  • Sun, J., Watson, S., Allsopp, D., Stanley, D., Skrtic, D., Tuning photo-catalytic activities of TiO2 nanoparticles using dimethacrylate resins Dental Materials, 2016 363-372
  • Hollingsworth, J., Bhupathiraju, N. V. S., Sun, J., Lochner, E., Vicente, M. H., and Russo, P., Preparation of Metalloporphyrin-Bound Superparamagnetic Silica Particles via “Click” Reaction ACS Applied Materials & Interfaces Article, 2016, 792-801
  • Huyang, G., Debertin, A., and Sun, J., Design and development of self-healing dental composites Journal of Materials and Design 2016 295-302
  • Gonzalez-Bonet A., Kaufman G., Yang Y., Wong C., Jackson A., Huyang G., Bowen R., and Sun J. Preparation of dental resins resistant to enzymatic and hydrolytic degradation in oral environments. Biomacromolecules, 2015 3381-3388. This paper was highlighted in Chemical & Engineering News, Oct 12, 2015.
  • Wang, P., Liu, X., Zhao, L., Weir, M., Sun, J., Chen, W., Man, Y., Xu, H., Bone tissue engineering via human induced pluripotent, umbilical cord and bone marrow mesenchymal stem cells in rat cranium, Acta Biomaterialia, 2015 236-248
  • Whitbeck, E., Swenson, K., Tordik, P., Kondor, S., Webb, T., Sun, J., Effect of EDTA preparations on rotary root canal instrumentation, Journal of Endondontics, 2015 92-96
  • Hoffman, K., Skrtic, D., Sun, J., and Tutak, W., Airbrushing composite polymer Zr-ACP nanofiber scaffolds with improved cell penetration for bone tissue regeneration, Tissue Engineering Part C: Methods, 2015 284-291
  • Sun, J., Forster, A., Johnson, P., Eidelman, N., Quinn, G., Schumacher, G., Zhang, X., and Wu, W., Improving Performance of Dental Resins by Adding Titanium Dioxide Nanoparticles, Dental Materials, 2011, 10, 972-982
  • Ding, Y., Sun, J., Ro, H., Wang, Z., Zhou, J., Lin, N., Cicerone, M., Soles, C., and Lin-Gibson, S., Thermodynamic Underpinnings of Cell Alignment on Controlled Topographies Advanced Materials, 2011, 23, 421-425
  • Sun, J., Ding, Y., Lin, N., Zhou, J., Ro, H., Soles, C., Cicerone, M., and Lin-Gibson, S., Exploring Cellular Contact Guidance Using Gradient Nanogratings Biomacromolecules, 2010, 11, 3067-3072
  • Sun, J., Fang, R., Lin, N., Eidelman, N., and Lin-Gibson, S., Nondestructive quantification of leakage at the tooth – composite interface and its correlation with material performance parameters Biomaterials 2009, 30, 4457-4462
  • Sun, J., Eidelman, N., and Lin-Gibson, S., 3D mapping of polymerization shrinkage using X-ray micro-computed tomography to predict microleakage Dental Materials, 2009, 25, 314-320
  • Sun, J., Ramanathan, M., Dorman, D., Newkome, G., Moorefield, C., and Russo, P.S., Surface Properties of a series of amphiphilic dendrimers with short hydrophobic chains Langmuir, 2008, 24, 1858-1862
  • Sun, J., Lyles, B., Yu, K., Weddell, J., Pople, J., Hetzer, M., De Kee, D. and Russo, P.S., Diffusion of dextran probes in a self-assembled fibrous gel composed of two-dimensional arborols J. Phys. Chem. B, 2008, 112, 29-35
  • Sun, J., and Lin-Gibson, S., MicroCT for measuring volumetric polymerization shrinkage of dental materials. Dental Materials, 2008, 24, 228-234
  • Zeiger, D., Sun, J., Schumacher, G., and Lin-Gibson, S., Evaluation of Dental Composite Shrinkage and leakage in extracted teeth using X-Ray Microcomputed Tomography Dental Materials 2009, 25, 314-320
  • Zhang, Q.Z., Cui, L., and Sun, J., High-strength declination points in the smectic schlieren texture of o-hydroxy Schiff base-type liquid crystal. Chemical Journal of Chinese University, 1996, 17, 1804-1806
Mentored Students and Postdocs
  • Dr. Yin Yang, Dartmouth College, 2015 - present
  • Dr. Sheng Song, Georgetown University, 2015-2016, now at Amarex
  • Dr. Xiaohong Wang, Institute of Chemistry, Chinese Academy of Sciences, 2016-present
  • Dr. George Huyang, University of Sydney, 2014 - 2016
  • Dr. Andres Gonzalez Bonet, Purdue University, 2013- 2015, now at FDA
  • Dr. Andrews Xu, Dentist, DDS, MS West Virginia University, School of Dentistry, 2014
  • Dr. Javoris Hollingsworth, Louisiana State University, 2012, now Assistant Prof. at Univ. of St. Thomas
  • Dr. Evan Whitbeck, DDS, MS, Naval Postgraduate Dental School, 2012-2013
  • Dr. Kelli Swenson, DDS, Endodontic Resident, Naval Postgraduate Dental School, 2011-2012
  • Dr. David Liu, DDS, MS, Naval Postgraduate Dental School, 2009-2011
  • Graham Parkinson, PhD candidate, Georgia Tech, 2014