Laurence C. Chow, Ph.D.
Calcium Phosphate Cement
- Carbonated Hydroxyapatite Bio-dosimeter
- Cavity Preventing Chewing Gum and Candies
- Carbonate Apatite Materials Based Biodosimetry
- Reference Materials for Human Tooth Enamel
Laurence C. Chow, Ph.D. Curriculum Vitae (PDF)
Well known in the field of calcium phosphates and biomineralization, with experiences spanning from basic science to clinical applications, Dr. Larry Chow is the co-inventor of the first widely-used calcium phosphate bone cements (CPC’s). Dr. Chow’s work on CPS’s ultimately obtained FDA approval for use as a calcium phosphate-based bone graft substitute (BoneSource) in 1996. Annual sales of BoneSource and Hydroset (also based on same patent portfolio) by Stryker exceeded $26 million in 2011. As Stryker prepared to opened facilities in Richardson, Texas, Rutherford, N.J., and Limerick, Ireland, Dr. Chow helped train engineers in testing and manufacturing.
An active member of the scientific community, Dr. Chow served as Chair (1992) and co-chair (1989) of Gordon Research Conference on Calcium Phosphates, presented invited lectures in numerous biomaterials meetings, and received the highest award from the International Association for Dental Research (IADR) for Outstanding Basic Research in Biological Mineralization (1998). His research was supported, without interruption, by NIH grants for three decades, and he was Principal Investigator of NIH R01 and R21 grants since 1985 with about $10 million in total funding. His aforementioned work with Stryker brought $1.3 million of annual royalties to the ADA Foundation for many years.
Current research projects:
Carbonate Apatite Materials Based Biodosimetry
Dose determination of human tooth enamel using electron paramagnetic resonance (EPR) spectroscopy is an established technique for dose reconstruction in radiation accidents. This technology is based on the fact that ionizing radiation generates unpaired electrons proportional to the dose. In the case of tooth enamel, the unpaired electron species are extremely stable, persisting for decades or longer.
We have discovered a novel synthetic carbonated hydroxyapatite cement (CHC) material that exhibits spectrally clean (Fig 1) and highly reproducible EPR signals in proportion to the dose of radiation received. Preparation of the CHC materials is based on the chemistry similar to that of our previously developed self-hardening calcium phosphate cement materials that are currently used for bone defect repairs. Further, the CHC samples are chemically stable and have adequate mechanical strengths and surface integrity to be used as dosimeters.
CHC dosimeters can be fabricated under ambient conditions with highly reproducible EPR and other physical and chemical characteristics. It is anticipated that by modifying the cement compositions, CHC materials may be adapted for a wide dose range, high range for industrial applications; low range for personal dosimetry, or for a specific type of ionizing radiation, e.g., neutron radiation.
Reference Materials for Human Tooth Enamel
In collaboration with researcher of NIST Biosynthesis and Biomaterials Division under the support of an NIST-NIH Interagency agreement, this work is a part of an effort to develop and produce a portfolio of biologically relevant calcium phosphate reference materials. A calcium phosphate cement system, previously developed in our laboratory for bone defect repair applications is used to prepare bulk carbonate apatite. The cement uses tetracalcium phosphate, Ca4(PO4)2O, and dicalcium phosphate, CaHPO4, as the starting materials and forms, under body temperatures, nano-sized (Fig. 2) hydroxyapatite crystals as the only product. When desired amounts of carbonate, sodium, fluoride, etc., are included in the cement ingredients, these components are incorporated into the apatite crystal structure in the product. Initial experiments demonstrated the feasibility of using this approach to prepare bulk carbonate apatite having carbonate, sodium, and fluoride contents closely match those of human enamel. Further efforts are focused on fabricate bulk carbonated apatite materials that have targeted porosity and mechanical properties that match those of the enamel.
Publications: See NIH Public Access Listing
Mentor to Ph.D. dissertations:
- Carey, Clifton E: Cyclic polyamine ionophore for use in a dibasic phosphate-selective electrode, 1992. (American University, Washington DC)
- Chain, Marcelo C: Mechanical behavior and the dissolution characteristics of a calcium phosphate cement for bone replacement, 1997. (University of Alabama, Birmingham, AL)
- Burguera, Elena: Development of a rapid setting tetracalcium phosphate-dicalcium phosphate dihydrate cement, 2004. (Universidad De Santiago De Compostela, De Compostela, Spain)
- Ogata, Hidehiro: In vitro properties of fluorapatite-forming calcium phosphate cements, 2011. (Nihon University Dental School, Tokyo, Japan)
Postdoctoral Associates in the last 10 years:
- Dr. Debra Vasquez (Naval Postgraduate Dental School)
- Dr. Hiromichi Iizuka (Japanese Navy Dental Corp)
- Dr. Yasushi Shimada (Tokyo Medical and Dental University)
- Dr. Go Inoue (Tokyo Medical and Dental University)
- Dr. Limin Sun (FDA, White Oak, MD)
External Collaborating Principle Investigators in the last 10 years:
- Dr. Marc Desrosiers, National Institute of Standards and Technology
- Dr. Joseph Antonucci, National Institute of Standards and Technology
- Dr. John E. Bonevich, National Institute of Standards and Technology
- Dr. Carl Simon, National Institute of Standards and Technology
- Dr. Martin Chiang, National Institute of Standards and Technology
- Dr. Hockin H Xu, University of Maryland Dental School
- Dr. John B Marino, University of Maryland Biotechnology Institute
- Dr. Livia Tenuta, University of Campinas Dental School, Piracicaba, SP, Brazil
- Dr. Akiyoshi Sugawara, Nihon University Dental School, Tokyo, Japan
- Dr. Amani Mostafa, National Research Center, Cairo, Egypt
- Dr. Takashi Komabayashi, Baylor College of Dentistry, Dallas, TX
- Dr. Tongxin Wang, Howard University Dental School
- Dr. Satoshi Hirayama, Nihon University Dental School, Matsudo, Japan