Study of Root Transparency in Different Postmortem Intervals Using Scanning Electron Microscopy

Abstract

In the fields of forensics, the identification of human remains is a recurrent problem. The estimated age at death is one of the copious criteria to be evaluated. In adult teeth, the height of the root dentin transparency is used to estimate age. However, in archaeological material, this phenomenon appears inconstant. The aim of this work was to observe the structural modifications of the sclerotic dentin in the teeth for different postmortem intervals. The study included two parts (retrospective and prospective study) with 21 human monoradicular teeth, from bodies donated to medical science with postmortem intervals (PMIs) of 0, 1, 2 and 5 years and archeological excavation. After inclusion based on resin, section and polishing, the samples were analyzed with a scanning electron microscope (SEM) JSM-7800F^®, and the procedure was completed via a semiquantitative analysis of calcium and phosphorus using EDX microanalysis. The analysis showed the existence of tubular and chemical modifications of sclerotic dentin at different PMIs. Our SEM study allowed us to observe a difference in tubule aspects linked to an increased PMI: the loss of peritubular collar and the lumen obstruction of tubules with a hyperdense material. Microanalysis highlighted variations in phosphocalcic ratios among the different groups, especially in the pulp area and the canine. Our hypotheses that explain these differences are based on the postmortem modifications of the crystals of the mineral phase of sclerotic dentin under the influence of chemical and/or bacterial action.

Keywords: estimated age at death; forensic science; postmortem changes; root transparency; scanning electron microscopy; sclerotic dentin; taphonomy.

Figure 1

Photomicrograph obtained via SEM in backscattered electrons (magnification ×190 and ×350–370)—(a) human tooth with a PMI of 0 y, (b) human tooth with a PMI of 1 y and (c) human tooth with a PMI of 2 y. Tubules near pulp chamber rounded (black square), tubules near cemento–dentinal junction lengthened (white square).

Figure 1

Photomicrograph obtained via SEM in backscattered electrons (magnification ×190 and ×350–370)—(a) human tooth with a PMI of 0 y, (b) human tooth with a PMI of 1 y and (c) human tooth with a PMI of 2 y. Tubules near pulp chamber rounded (black square), tubules near cemento–dentinal junction lengthened (white square).

Figure 2

Photomicrograph obtained via SEM in secondary electrons (magnification ×15,000 and ×20,000)—(a) human tooth with a PMI of 5 y, (b) human tooth with an archeological PMI. Structure in mesh in lumen of tubule.

Figure 2

Photomicrograph obtained via SEM in secondary electrons (magnification ×15,000 and ×20,000)—(a) human tooth with a PMI of 5 y, (b) human tooth with an archeological PMI. Structure in mesh in lumen of tubule.

Figure 3

Photomicrographs obtained via SEM (magnification ×4000 and ×5000). Apical area: Tubules surrounded by a denser collar (black arrows). (a) Human tooth with a PMI of 0 y, (b) human tooth with a PMI of 1 y, (c) human tooth with a PMI of 2 y, (d) human tooth with a PMI of 5 y, (e) human tooth with an archeological PMI. Tubules obstructed by a hyperdense material (white arrow), covered by voluminous hyperdense structures.

Figure 3

Photomicrographs obtained via SEM (magnification ×4000 and ×5000). Apical area: Tubules surrounded by a denser collar (black arrows). (a) Human tooth with a PMI of 0 y, (b) human tooth with a PMI of 1 y, (c) human tooth with a PMI of 2 y, (d) human tooth with a PMI of 5 y, (e) human tooth with an archeological PMI. Tubules obstructed by a hyperdense material (white arrow), covered by voluminous hyperdense structures.

Figure 4

(a) Distribution of the 539 phosphocalcic ratio measurements in the samples of the retrospective part and (b) distribution of the 1620 phosphocalcic ratio measurements in the samples of the prospective part.