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Micromechanical Property Recovery of Human Carious Dentin Achieved with Colloidal Nano-β-tricalcium Phosphate

¹ Department of Oral Biomaterials and Technology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan; and
² Biomaterials Science Research Unit, Faculty of Dentistry, University of Sydney, Sydney Dental Hospital, Surry Hills, NSW 2010, Australia

View larger version (61K): [in this window] [in a new window]   Figure 1. The sample was sectioned perpendicular to the occlusal surface through the caries lesion.

View larger version (11K): [in this window] [in a new window]   Figure 2. The force-displacement curves. (A) A schematic representation of load vs. indenter displacement data for an indentation experiment. Hardness H is calculated from H = P/A, where P is loading force and A is the contact area at maximum load. Elastic modulus can be calculated from E = (dP/dh) A, where dP/dh is the slope of the unloading curve at maximum force. (B) A representative comparison of the force-displacement curves of carious dentin treated with or without β-TCP (n = 9). The initial loading component of carious dentin after immersion in colloidal β-TCP appears substantially improved and is much closer to that of sound dentin. However, as can be observed, more creep occurs with this sample at maximum load than for untreated carious dentin.

View larger version (11K): [in this window] [in a new window]   Figure 3. The elastic modulus and hardness of sound dentin and carious dentin. Indentations (n = 9) performed in both sound and carious dentin within the individual teeth, before and after immersion in colloidal calcium phosphates, are compared. The results are expressed as the mean ± SD, and analyzed statistically by analysis of variance (ANOVA), with follow-up by a modified Tukey t test. Significant differences are considered to exist when p < 0.01. The elastic modulus and hardness of carious dentin are significantly lower (p < 0.01) than those of sound dentin before immersion. After immersion in colloidal HA, the mechanical properties of carious dentin are not improved. The elastic modulus is significantly increased (p < 0.01) in the case of colloidal β-TCP, whereas the hardness of the carious region is not increased.

View larger version (10K): [in this window] [in a new window]   Figure 4. Representative EDX spectra of elements present in the indented region of each sample. The elemental compositions adjacent to each indentation (n = 9) within individual teeth were calculated. The results were analyzed statistically by analysis of variance (ANOVA), with follow-up Tukey t test. Significant differences were considered to exist when p < 0.01. Carious dentin, after being soaked in colloidal β-TCP, showed significantly higher (p < 0.01) mineral content than did carious dentin immersed in colloidal HA.

Journal of Dental Research, Vol. 87, No. 3, 233-237 (2008)
DOI: 10.1177/154405910808700315


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