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Heat Treatment Strengthens Human Dentin

¹ Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan;
² Department of Mechanical System Engineering, Graduate School of Engineering, Hiroshima University, Hiroshima, Japan; and
³ Department of Macromolecular Science, Graduate School of Science, Osaka University, Osaka, Japan

View larger version (24K): [in this window] [in a new window]   Figure 1. Specimen preparation and flexural and tensile testing. (a) Beam-shaped specimens were obtained from coronal central portions of human third molars. (b) Dentinal tubule orientations of the specimens were arranged to run parallel or perpendicular to loading surfaces. (c) Specimens subjected to flexural fracture testing were secured in a custom-made metallic holder with cantilever beam geometry. (d) Beam-shaped specimens were trimmed to a cross-section area of 1.0 mm2 for microtensile testing.

View larger version (156K): [in this window] [in a new window]   Figure 2. Fractographic observations with parallel and perpendicular specimens after flexural testing. In the wet condition, the peritubular regions were smooth and the intertubular dentin was rough in both the parallel and perpendicular specimens (a,c). In contrast, in the heated dentin, the entire surfaces were rough (b,d). In the perpendicular specimens, many dentinal tubules were visible in the dentin in the wet condition (c), compared with those in the heated condition (d).

View larger version (75K): [in this window] [in a new window]   Figure 3. Lateral packing of dentin collagen before and after the specimen was heated, examined by x-ray diffraction patterns. A specimen without demineralization showed Bragg diffraction rings originating from hydroxyapatite crystals and collagen (a). The distance between the axes of the collagen triple-helices, which is acknowledged to be 14 Å in the wet condition (b,d), shrunk to 11 Å after the specimen was heated at 110°C for 1 hr (c).

Journal of Dental Research, Vol. 87, No. 8, 762-766 (2008)
DOI: 10.1177/154405910808700807


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