Analysis of fracture surface of dentin using 2D FFT

Objective: The investigation of fracture surface is useful for analysis of fracture mechanism. The outcomes of various image observation depend on the rather subjective interpretation. The purpose of this study was to evaluate objective fracture surface analysis using numerical data with two-dimension fast Fourier transforms (2DFFT). Method: The sixteen fracture surfaces of bovine root dentin after the direct tensile test, 1 x 1 mm, were used (Tonami et al, #197 IADR, Vancouver, 1999). The fracture surfaces were classified into two groups according the dentinal tubule orientation (DTO) and fracture ridge lines running (FRL); Group 1 shows that DTO were parallel to FRL, while Group 2 did not. The specimen numbers of Group 1 and 2 were six and ten, respectively. The fracture surface image of each specimen was digitalized and processed using 2DFFT filter of Image J version 1.32 (National Institute of Health, USA). Obtained frequency components and power specter were plotted on an x-y logarithmic coordinate. The graduation of regression line of the plot (GR) was calculated. The difference of GR between two groups was statistically analyzed by the student t-test. Results: The GRs (SD) of Group 1 and Group 2 were –0.82 (0.17) and –1.08 (0.13), respectively and the difference between two groups was significant (p<0.05). Conclusion: Our results suggest that the 2DFFT could be useful process for evaluating image characteristics into numerical data which could objectively specify the different surface images.