Local properties of a functionally graded interphase between cementum and dentin.

The study of natural interfaces may provide information necessary to engineer functionally graded biomaterials for bioengineering applications. In this study, the mechanical, structural, and chemical composition variations associated with a region between cementum and dentin were studied with the use of nanoindentation, microindentation, optical microscopy, and Raman microspectroscopy techniques. Three-millimeter-thick transverse sections (N = 5) were obtained from the apical one-third of the roots of sterilized human molars. The samples were ultrasectioned at room temperature with the use of a diamond knife and an ultramicrotome. Longitudinal ground sections of 100 microm thickness were prepared and stained with von Kossa stain to determine the mineralized regions within the molar roots. Raman microspectroscopy was used to determine the relative inorganic content, mainly apatite (PO4(3-)nu1 mode at 960 cm(-1)) and organic content, mainly collagen (C--H stretch at 2940 cm(-1)) between cementum and dentin bulk tissues. The microindentation and nanoindentation results indicated a gradual transition in hardness from cementum to dentin over a width ranging from 100 to 200 microm. However, the variation in hardness data for cementum and dentin by nanoindentation was larger (0.62 +/- 0.21, 0.77 +/- 0.14 GPa) than from microindentation (0.49 +/- 0.03, 0.69 +/- 0.07 GPa). Within the 100 to 200 microm region there was a 10 to 50 microm fibrillar hydrophilic cementum-dentin junction (CDJ) with mechanical properties significantly lower than either the cementum or the dentin side of CDJ. Light microscopy revealed a 100 to 200 microm translucent region between cementum and dentin. Raman microspectroscopy results showed a variation in organic and inorganic composition 80 to 140 microm wide. It was concluded that a morphologically and biomechanically different CDJ lies within a wider cementum-dentin interphase. Hence, cementum, dentin, and the interphase can be classified as a functionally graded dental tissue within the root of a tooth.

[1]  Mehmet Sarikaya,et al.  Nano-mechanical properties profiles across dentin–enamel junction of human incisor teeth , 1999 .

[2]  I A Mjör,et al.  The structure of dentine in the apical region of human teeth. , 2001, International endodontic journal.

[3]  S. Weiner,et al.  Human root dentin: structural anisotropy and Vickers microhardness isotropy. , 1998, Connective tissue research.

[4]  Stefan Hallström,et al.  Strength prediction of beams with bi-material butt-joints , 2003 .

[5]  A. Hopewell-Smith Concerning Human Cementum , 1920 .

[6]  George M. Pharr,et al.  On the generality of the relationship among contact stiffness, contact area, and elastic modulus during indentation , 1992 .

[7]  S. Weiner,et al.  Mapping of tooth deformation caused by moisture change using moiré interferometry. , 2003, Dental materials : official publication of the Academy of Dental Materials.

[8]  T. Cate,et al.  Oral histology: Development, structure, and function , 1980 .

[9]  M. J. Drews,et al.  Utilization of moiré interferometry to study the strain distribution within multi-layer thermoplastic elastomers , 2002, Journal of biomaterials science. Polymer edition.

[10]  Mehdi Balooch,et al.  The dentin-enamel junction: a natural, multilevel interface , 2003 .

[11]  T. Boland,et al.  Nanoindentation properties of compression-moulded ultra-high molecular weight polyethylene , 2003, Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine.

[12]  J. Aubin,et al.  Marrow Stromal Cell Culture: Osteoblast lineage in experimental animals , 1998 .

[13]  G. Marshall,et al.  Ultrastructure and nanomechanical properties of cementum dentin junction. , 2004, Journal of biomedical materials research. Part A.

[14]  W H Douglas,et al.  Structure-Property Relations and Crack Resistance at the Bovine Dentin-Enamel Junction , 1994, Journal of dental research.

[15]  R. Suzuki,et al.  The structure and function of the cemento-dentinal junction in human teeth. , 1999, Journal of periodontal research.

[16]  S. Rasmussen Fracture Properties of Human Teeth in Proximity to the Dentinoenamel Junction , 1984, Journal of dental research.

[17]  S. Weiner,et al.  Strain-structure relations in human teeth using Moiré fringes. , 1997, Journal of biomechanics.

[18]  The fibrous structure of the cemento-dentinal junction in human molars shown by scanning electron microscopy combined with NaOH-maceration. , 2000, Journal of periodontal research.

[19]  Mehmet Sarikaya,et al.  The Dentino‐enamel Junction is a Broad Transitional Zone Uniting Dissimilar Bioceramic Composites , 2000 .

[20]  A. Fischer-Cripps,et al.  Analysis of depth-sensing indentation tests with a Knoop indenter , 2001 .

[21]  S A Gansky,et al.  Mechanical properties of the dentinoenamel junction: AFM studies of nanohardness, elastic modulus, and fracture. , 2001, Journal of biomedical materials research.

[22]  G. Marshall,et al.  The functional width of the dentino-enamel junction determined by AFM-based nanoscratching. , 2001, Journal of structural biology.

[23]  D. Bosshardt,et al.  Cementogenesis reviewed: A comparison between human premolars and rodent molars , 1996, The Anatomical record.

[24]  G. Marshall,et al.  The effect of sample preparation technique on determination of structure and nanomechanical properties of human cementum hard tissue. , 2004, Biomaterials.