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Dentin samples of the incisor taken from Wistar rats of different ages are studied. A series of physical techniques are used to characterize the samples, with particular emphasis on 31 P solid-state nuclear magnetic resonance. The structure of incisor dentin in rats can be described as apatite crystallites embedded in an amorphous matrix. We find that 19% of the apatite crystallites contain hydroxyl groups, which are distributed near the surface of the crystallites. The internal region of the crystallites is deficient in hydroxyl groups. As rats mature with age, there are several changes in the chemical composition of the incisor dentin: (i) the water content and phosporous amount in the amorphous matrix decrease; (ii) the amount of the phosphorus species in the apatite crystallites remains the same; and (iii) the loss of phosphorus species is accompanied by approximately the same loss of the calcium content.

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We evaluated the feasibility of using the modified Brazilian disk test to measure the post-dentin interfacial bond strength. Advanced nondestructive examination and imaging techniques in the form of acoustic emission (AE) and digital image correlation (DIC) were used innovatively to capture the fracture process in real time. DIC showed strain concentration first appearing at one of the lateral sides of the post-dentin interface. The appearance of the interfacial strain concentration also coincided with the first AE signal detected. The new method has the advantages of simpler specimen preparation, no premature failure, more consistent failure mode and smaller variations in the calculated bond strength.

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