Methods: Small sections of enamel, dentin, and enamel and dentin combined were obtained from extracted teeth. The specimens were placed in a thermogravimetric analyzer (TGA 6, Perkin Elmer Instruments) which measured the weight loss of the specimen during heating and cooling. The specimens were placed in a TGA at room temperature, then heated to 1000° C at a rate of 50° C/min. After reaching the maximum temperature the specimen was cooled back to room temperature with the same rate of 50° C/min. In a second phase of the study specimens were subjected to the following temperature profile: 50° 150° 50° 350° 50° 600° 50° 1000° 50°, all at 50° C/min. Five enamel, four dentin, and eight enamel and dentin specimens were obtained from desiccated or moist permanent teeth. Two specimens containing both enamel and dentin were from deciduous teeth.
Results: The average weight loss for enamel specimens was 9.7% and 35.6% for dentin. The same was found for deciduous teeth. Weight loss of the specimens began at 100° C, with most of the weight loss occurring between 200° and 600° C. The specific odor of overheated teeth emanated from the specimens at a very specific temperature interval of 420° - 430° C. The specimens subjected to the incremental heat cycles (temp profile) had no weight loss until the temperature in a subsequent heat cycle exceeded the highest temperature of the previous cycle.
Conclusions: Enamel and dentin undergo irreversible physical changes when exposed to heat. For teeth that have been previously exposed to elevated temperatures, weight loss is not seen until the previous temperature is exceeded, making weight loss a thermal forensic marker for the temperature to which a tooth has previously been exposed.