Hertzian contact response of dentin with loading rate and orientation.
OBJECTIVE
To test the hypothesis that dentin Hertzian contact response varies with loading rate and tubule orientation.


METHODS
Sound teeth (n=12) were cut either parallel or perpendicular to the axial direction to expose dentin (n=6 each). The cut specimens were embedded (poly-methyl-methacrylate (PMMA) and divided into two groups: (GL) load applied parallel to dentin tubule direction and (GP) load applied perpendicular to tubule direction. A 1.5mm diameter tungsten-carbide ball was used for Hertzian contact testing with a maximum load of 150 N load and loading rates of 0.1, 1, 100, and 1000 N/s on each specimen. Indented specimens were observed microscopically and photomicrographs acquired. Hertzian contact diameter and modulus were analysed (p<0.05) by one-way ANOVA and Tukey test.


RESULTS
There were significant differences (p<0.05) in Hertzian response with respect to loading rate for GL (0.1N/s versus 1000 N/s, 0.1N/s versus 100 N/s, 1N/s versus 1000 N/s, and 1N/s versus 100 N/s), and GP (0.1N/s versus 1000 N/s, 0.1N/s versus 100 N/s, and 1N/s versus 1000 N/s). Contact modulus was higher for GL compared to GP at all loading rates (p<0.05).


CONCLUSIONS
The results suggest that dentin contact modulus is loading rate dependent. Tubule orientation of dentin did not influence contact modulus values (p>0.05).
da Silva
Nelson Renato Franca Alves
NR
Department of Prosthodontics, New York University College of Dentistry, NY, USA. nrd1@nyu.edu
Lalani
F
F
Coelho
Paulo G
PG
Clark
Elizabeth A
EA
Fernandes
Carlos Augusto de Oliveira
CA
Thompson
Van P
VP
D003799:Dental Stress Analysis / Q000379:methods; D003804:Dentin / Q000648:ultrastructure*; D006801:Humans; D021621:Imaging, Three-Dimensional; D009949:Orientation; D013314:Stress, Mechanical