Importance of tubule density to the fracture toughness of dentin

• A reduction in density and diameter of tubules was identified in dentin with aging.
• In the outer dentin, nearly a 40% reduction in the lumen area occurred with aging.
• The fracture toughness of dentin was modeled in terms of the tubule characteristics.
• The model prediction for young dentin toughness agrees with experimental results.

ObjectiveThe fracture toughness of dentin is critical to the prevention of tooth fracture. Within the tooth crown, the mechanical properties of dentin are influenced by spatial variations in the density and diameter of the dentin tubules with distance from the pulp. There are also relevant changes to the microstructure of dentin with age. In this investigation the importance of tubule density to the fracture toughness of dentin was evaluated in “young” and “old” age groups.MethodsThe variations in microstructure (density and diameter of tubules) from young and old donor teeth were studied by means of optical microscopy.ResultsA reduction in the density and diameter of tubules was identified to occur with aging. An approach previously proposed to study the mechanical behavior of porous materials was used to model the fracture toughness of coronal dentin in terms of the tubule characteristics. Results were then compared with published results from previous studies.ConclusionsThe model predictions were consistent with experimental results for the fracture toughness of dentin from young donor teeth, but overestimated the values that have been reported for “old” dentin.