Fatigue and Fracture Observations of Radicular Dentin

This study was aimed to observe the fracture surfaces of dentin specimen after the fatigue test to be taken into account for teeth fracture. Radicular dentin from bovine lower central incisors was used. Dentin slabs of 1 mm thickness were trimmed into dumbbell-shaped specimens along the tooth axis, then, fatigue tests were performed. The staircase method was employed to determine fatigue strength and its standard deviation. Thereafter, the fractured surfaces of the specimens were coated using an ion sputtering machine and examined by scanning electron microscopy. Observations of the dentin fatigue specimens using the scanning electron microscopy showed that the fatigue striations were almost aligned perpendicularly to dentinal tubules. Moreover, fatigue striations spaced approximately 3 to 10 μm apart from fracture surfaces of intertubular dentin. Additionally, a porous fibrous reticulate texture can be seen in the intertubular dentin. On the other hand, a thin peritubular collar can be seen lining the tubules in dentin. However, some of the peritubuler cuffs in the dentin appeared debonded from the surrounding intertubular dentin and partially fractured. In addition, it was also confirmed that there was no distinction between the peritubular dentin and the intertubular dentin in fracture surfaces. The peritubular and intertubular dentin differ in fracture and fatigue crack propagations