Denaturation temperatures of dentin matrices. I. Effect of demineralization and dehydration.

The denaturation temperature (T(d)) of dentin collagen in mineralized versus demineralized teeth was examined as a function of dentin age and the extent of dehydration. Using differential scanning calorimetry, T(d) of mineralized dentin was shown to be between 160 degrees C to 186 degrees C, depending on whether it was from young or old dentin that was hydrated or dehydrated, respectively. Demineralized dentin exhibited a T(d) of 65.6 degrees C that increased with dehydration to 176 degrees C. The presence of apatite crystallites or interpeptide bonding increased the T(d) of demineralized matrices. Interpeptide hydrogen bonding seems to stabilize collagen to thermal challenge. Water breaks interpeptide hydrogen bonds making collagen more susceptible to thermal denaturation. Rises in intracanal temperature are unlikely to cause extensive denaturation of mineralized root dentin walls. However, hydrated or partially dehydrated root canal walls that have been partially demineralized with chelating agents or mild acids may be susceptible to thermal denaturation.