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The UCSF Program
in Craniofacial and Mesenchymal Biology
FACULTY
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Biomaterials and Calcified Tissues
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My research interests center on understanding the relationship between structures, properties and mechanisms in materials. My major expertise is in x-ray scattering, particularly diffraction, by materials and atomic force microscopy for microstructural and mechanical properties characterization. The nanostructure and properties of the interface between materials and calcified tissues are of great clinical significance since failure occurs in the weakest area of this structure. My current research efforts are mainly focussed in 2 areas: dentin characterization and modification, including the dentino-enamel junction, and the development of new dental implant material systems .
Much of dental materials research involves attempts to improve bonding to dentin. Through collaborative efforts with scientists at Lawrence Livermore and Lawrence Berkeley National Laboratories, we are characterizing dentin, structurally and chemically, with the premise that developing materials to bond to this substrate will be greatly hampered until the substrate is understood. We began by studying normal coronal dentin and have progressed from normal dentin to altered forms of dentin, including transparent dentin related to disease, age and intratooth position. We are using atomic force microscopy to study morphological changes in dentin as a function of drying, storage and demineralization. Demineralization is related to the caries process as well as being a critical part of preparation for bonding. The AFM is used to measure the nanoscale mechanical properties of dentin and its interface with restorative materials. These measurements are being combined with a model of dentin to predict properties on the macroscale. We use x-ray tomographic microscopy, a 3-D non-invasive imaging technique developed by a colleague at LLNL, to study morphological and mineral density changes as well. We have begun a new project that uses the DEJ as a model interface between 2 materials with different mechanical properties. We are beginning by studying the structure and using fracture mechanics to determine the mechanical properties of the DEJ.
My second area of interest is in the area of ceramic coatings on implants. We are working with colleagues from LBNL to develop a new apatite based bioactive coating that will more permanently adhere to Ti and Ti alloys.
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Selected Publications
Curtis DA, Eggleston TA, Watanabe LG, Marshall SJ. (1989) Shear bond strength of visible-light cured resin relative to heat cured resin. Dent Mater 5:314-318.
Marshall SJ, Balooch M, Habelitz S, Balooch G, Marshall GW. (2003) Dentin-Enamel Junction (DEJ)-Biomimetic Model for Material Tissue Interfaces. Transactions Acad Dent Mater 17:21-32.
Staninec M, Nalla RK, Hilton JF, Ritchie RO, Nonomura G, Marshall GW, Marshall SJ. (2005) Dentin errosion simulation by cantilever beam fatique and pH change. J Dent Res 84:371-375.
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Osteoblast depositing
bone matrix |
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