Color change in teeth due to burning: Spectrophotometric analysis

Abstract

Teeth are one of the most common skeletal elements for forensic identification purposes and also the strongest human tissue, making them resistant to high temperatures. Over the course of burning as temperature increases, teeth go through a process of structural change characterized by a carbonization phase (at approx. 400 °C) and calcination phase (at approx. 700 °C) that might result in complete enamel loss. The aim of the study was to quantify color change of enamel and dentin and to determine whether both tissues can be used for estimating burn temperature as well as to evaluate the whether these changes are visually perceptible. 58 human, permanent maxillary molars without restorations were burned for 60 min at either 400 °C or 700 °C in a Cole-Parmer StableTemp Box Furnace. The change in color was measured for the crown and root using a SpectroShade Micro II spectrophotometer to determine lightness (L*), green-red color (a*), and blue-yellow color (b*). Statistical analysis was performed using SPSS version 22. There is a significant difference between the L*, a*, and b* values of pre-burned enamel and dentin at 400 °C (p < 0.001). In addition, differences in dentin measures between 400 °C and 700 °C (p < 0.001), as well as pre-burned teeth and 700 °C (p < 0.001). The mean L*a*b* values were used to calculate a measure of the perceptible difference between colors (ΔE) revealing a highly perceptible color difference between the pre- and post-burn teeth for both enamel and dentin. There is a low perceptible difference between burned enamel and dentin was found. During the carbonization phase the tooth gets darker and redder and as temperature increases, teeth become bluer. Overall, as calcination occurs the tooth root color gets closer to a neutral gray palette. The results showed a highly perceptible difference indicating that for forensic purposes simple visual color evaluation can provide reliable information, and dentin color evaluation can be used in cases when enamel is missing. However, the spectrophotometer allows an accurate replicable measure of tooth color across various stages of the burning process. This has practical applications in forensic anthropology as a portable and nondestructive technique that can be used in the field regardless of the practitioner’s level of experience.