title: Structure, chemical composition and mechanical properties of coronal cementum in human deciduous molars.
abstract: OBJECTIVE
  It was hypothesized that the coronal cementum containing collagen forms a weak junction with enamel unlike the well integrated DEJ and CDJ.
  
  
  METHODS
  The hypothesis was investigated in two parts: (1) evaluate the structure, chemical composition and mechanical properties of coronal cementum and its junction with enamel using scanning electron microscopy, micro-X-ray computed tomography, and atomic force microscopy. The chemical composition and mechanical properties were determined by evaluating the spatial variations of inorganic (PO(4)(3-)nu(1) mode at 960 cm(-1)) and organic (C-H deformation at 1452 cm(-1); C-H stretch at 2940 cm(-1)) contents using Raman microspectroscopy and elastic modulus and hardness values using nanoindentation. (2) Estimate the strength and evaluate the microstructure of coronal cementum interface with enamel using SEM and MicroXCT.
  
  
  CONCLUSIONS
  Coronal cementum is heterogeneous because it is a combination of laminar acellular afibrillar cementum and acellular extrinsic fiber cementum with relatively higher organic content. It integrates micromechanically via a scallop-like weak interface with enamel unlike the biomechanically efficient DEJ and CDJ and is continuous with primary root cementum. A single tooth could exhibit all three types of cementum enamel junctions; an overlap, butt and a gap depending on the sectioning plane. The elastic modulus of coronal cementum (11.0+/-5.8 GPa) is significantly lower (p<0.05; Student's t-test with 95% confidence interval) than primary cementum (15.8+/-5.3 GPa).
authors.affiliation: Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, UCSF, San Francisco, CA 94143-0758, USA. sunita.ho@ucsf.edu
authors.forename: Sunita P
authors.initials: SP
authors.lastname: Ho
authors.forename: Pavla
authors.initials: P
authors.lastname: Senkyrikova
authors.forename: Grayson W
authors.initials: GW
authors.lastname: Marshall
authors.forename: Wenbing
authors.initials: W
authors.lastname: Yun
authors.forename: Yong
authors.initials: Y
authors.lastname: Wang
authors.forename: Kunal
authors.initials: K
authors.lastname: Karan
authors.forename: Cheng
authors.initials: C
authors.lastname: Li
authors.forename: Sally J
authors.initials: SJ
authors.lastname: Marshall
mesh_terms: D001696:Biomechanical Phenomena; D002244:Carbon / Q000737:chemistry; D003094:Collagen / Q000648:ultrastructure; D003739:Dental Cementum / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure; D003743:Dental Enamel / Q000648:ultrastructure; D055119:Elastic Modulus; D006244:Hardness; D006801:Humans; D006859:Hydrogen / Q000737:chemistry; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D015591:Microspectrophotometry; D008963:Molar / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure*; D010710:Phosphates / Q000032:analysis; D013059:Spectrum Analysis, Raman; D013314:Stress, Mechanical; D019237:Tooth Cervix / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure*; D014092:Tooth Root / Q000648:ultrastructure; D014094:Tooth, Deciduous / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure*; D055114:X-Ray Microtomography
chemical_list: D010710:Phosphates; D002244:Carbon; D006859:Hydrogen; D003094:Collagen