title: Mineral density volume gradients in normal and diseased human tissues.
abstract: Clinical computed tomography provides a single mineral density (MD) value for heterogeneous calcified tissues containing early and late stage pathologic formations. The novel aspect of this study is that, it extends current quantitative methods of mapping mineral density gradients to three dimensions, discretizes early and late mineralized stages, identifies elemental distribution in discretized volumes, and correlates measured MD with respective calcium (Ca) to phosphorus (P) and Ca to zinc (Zn) elemental ratios. To accomplish this, MD variations identified using polychromatic radiation from a high resolution micro-computed tomography (micro-CT) benchtop unit were correlated with elemental mapping obtained from a microprobe X-ray fluorescence (XRF) using synchrotron monochromatic radiation. Digital segmentation of tomograms from normal and diseased tissues (N=5 per group; 40-60 year old males) contained significant mineral density variations (enamel: 2820-3095 mg/cc, bone: 570-1415 mg/cc, cementum: 1240-1340 mg/cc, dentin: 1480-1590 mg/cc, cementum affected by periodontitis: 1100-1220 mg/cc, hypomineralized carious dentin: 345-1450 mg/cc, hypermineralized carious dentin: 1815-2740 mg/cc, and dental calculus: 1290-1770 mg/cc). A plausible linear correlation between segmented MD volumes and elemental ratios within these volumes was established, and Ca/P ratios for dentin (1.49), hypomineralized dentin (0.32-0.46), cementum (1.51), and bone (1.68) were observed. Furthermore, varying Ca/Zn ratios were distinguished in adapted compared to normal tissues, such as in bone (855-2765) and in cementum (595-990), highlighting Zn as an influential element in prompting observed adaptive properties. Hence, results provide insights on mineral density gradients with elemental concentrations and elemental footprints that in turn could aid in elucidating mechanistic processes for pathologic formations.
authors: Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, University of San Francisco, San Francisco, California, United States of America.
authors: Sabra I
authors: SI
authors: Djomehri
authors: Xradia Inc., Pleasanton, California, United States of America.
authors: Susan
authors: S
authors: Candell
authors: Xradia Inc., Pleasanton, California, United States of America.
authors: Thomas
authors: T
authors: Case
authors: Xradia Inc., Pleasanton, California, United States of America.
authors: Alyssa
authors: A
authors: Browning
authors: Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, University of San Francisco, San Francisco, California, United States of America.
authors: Grayson W
authors: GW
authors: Marshall
authors: Xradia Inc., Pleasanton, California, United States of America.
authors: Wenbing
authors: W
authors: Yun
authors: Xradia Inc., Pleasanton, California, United States of America.
authors: S H
authors: SH
authors: Lau
authors: Stanford Synchrotron Radiation Lightsource, Stanford Linear Accelerator Center, Menlo Park, California, United States of America.
authors: Samuel
authors: S
authors: Webb
authors: Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, University of San Francisco, San Francisco, California, United States of America.
authors: Sunita P
authors: SP
authors: Ho
mesh_terms: D015519:Bone Density / Q000502:physiology*; D002114:Calcinosis / Q000473:pathology*; D002118:Calcium / Q000032:analysis; D003728:Dental Calculus / Q000737:chemistry*; D003739:Dental Cementum / Q000737:chemistry*; D003743:Dental Enamel / Q000737:chemistry*; D003804:Dentin / Q000737:chemistry*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010758:Phosphorus / Q000032:analysis; D013052:Spectrometry, X-Ray Emission; D055114:X-Ray Microtomography / Q000379:methods*; D015032:Zinc / Q000032:analysis
chemical_list: D010758:Phosphorus; D015032:Zinc; D002118:Calcium