Nanoindentation hardness of intertubular dentin in sound, demineralized and natural caries-affected dentin

作者：Joves Gerardo Jose; Inoue Go^*; Sadr Alireza; Nikaido Toru; Tagami Junji

来源：Journal of the Mechanical Behavior of Biomedical Materials, 2014, 32: 39-45.

DOI：10.1016/j.jmbbm.2013.12.017

• Nanohardness
• Caries-affected dentin
• Sound dentin
• Artificial caries-affected dentin
• Remaining dentin thickness

The purpose of this study was to investigate the mechanical properties of intertubular dentin in sound, natural caries-affected (NCAD) and artificial caries-affected dentin (ACAD) using nanoindentation. %26lt;br%26gt;Materials and methods: Non-caries molars and caries molars with International Caries Detection and Assessment System (ICDAS II) score 5 at the occlusal site were used and caries was excavated using a spoon excavator, a round bur at low speed without water and a dye solution as guidance to detect the infected tissue. Specimens with remaining dentin thickness (RDT) %26gt;2 mm were selected. ACAD teeth were created from sound teeth over 7 days in a demineralizing solution. Specimens were embedded into plastic rings with acrylic resin and then sagittal mesial-distal sectioned from crown to the long axis of the root under cooling water using a low-speed diamond blade. The surface of interest was fine polished sequentially. Hardness measurement was performed within an axial depth of 1000 pm with at least of 320 indentations on each sample. Mann-Whitney U Test was used to compare the hardness as the variable among different dentin types (SOUND, NCAD and ACAD) at each dentin depth level. %26lt;br%26gt;Results: There was no significant difference in nanohardness between NCAD and ACAD up to a depth of 130 pm (p%26gt;0.05). NCAD consistently showed lower hardness. ACAD showed no significant difference in hardness with SOUND dentin beyond 190 mu m (p%26lt;0.05). The lesion front in ACAD was considered to be located around the depth of 180 mu m. %26lt;br%26gt;Conclusion: Natural and artificial caries-affected dentin tissues were superficially comparable in intertubular nanohardness. There is a certain layer within the natural caries-affected dentin with higher hardness; however the long-term effects of caries beneath the lesion extend deeply through intertubular dentin. Sound dentin at deep areas (close to the pulp chamber) is considered to be soft.

• 出版日期2014-4