POST-MORTEM CHANGES IN TEETH- FORENSIC ISSUES

Headnote

Abstract

Teeth have an increased resistance to environmental factors and decomposition processes, which makes them highly valuable in forensic investigations. The either physical (wind, water, sun, soil type) or biological (plant roots, insects, animals) environmental factors and the decomposition processes induce post-mortem changes in teeth, which are relevant to forensic investigation in terms of estimating the post-mortem interval or of elucidating the conditions in which the body stood after death. In this paper, based on the data provided in the literature, the authors present the main changes induced by environmental factors and decomposition processes in teeth and refer to their relevance in forensic activity.

Keywords: teeth, death, environment, decomposition, changes, forensics.

1. INTRODUCTION

Teeth are the hardest structure in the human body, showing a remarkable resistance to post-mortem external and internal destructive processes. This feature makes them valuable for forensic investigations. Knowledge of post-mortem changes that occur in the teeth under the influence of environmental factors or cadaveric decomposition is of particular importance for elucidating aspects regarding the environment in which the corpse stood and the estimation of post-mortem interval.

The present study reviews some of the post-mortem changes that occur in teeth under the action of physical and biological environmental factors and of those arising from cadaveric decomposition.

2. POST-MORTEM CHANGES CAUSED BY BIOLOGICAL FACTORS

Plant roots can etch over dental remains that were either buried or left on the surface of the soil. This process results in a branched or crosslinked aspect which gives teeth a mottled or colored appearance [1]. After a fairly long post-mortem interval, plant roots can fully-fragment a dentition, while mosses and lichens can discolor the exposed roots of human teeth.

Animals and insects can also damage the human hard tissues [2,3]. Rodents can destroy any bone by biting the edges, leaving a distinctive shell appearance [3]. Carnivorous animals, such as coyotes, can eat the face of the corpse, including the teeth. They can also drag the head over a long distance, which may determine detachment and loss of the anterior teeth along the way [4,5]. The teeth swallowed by animals and subsequently eliminated through their faeces are corroded by the mechanical and chemical processes of digestion [6,7]. The corrosion areas are usually small, focal, and not discolored, with the dentin being more affected by this process than the enamel.

3. POST-MORTEM CHANGES CAUSED BY PHYSICAL FACTORS

There are many physical factors that can damage human teeth, such as the wind, water, sun, and the soil itself.

Wind can damage the surface of the teeth by grinding them with grains of sand, silt and clay. The erosion caused by sand particles is more evident in arid environments, where the wind-driven sand can even bury the exposed teeth.

Water may change the color of the dental tissue by penetrating the enamel and dentin and by depositing various minerals, which results in a darker coloration and a smoother appearance of teeth [8].

Larger scale events, such as geological and hydrological phenomena, can displace and fracture teeth. Colluvium and alluvium can cover the human remains, the exposed dentin becoming brown or orange, due to the surrounding sediment, while the color of the enamel will not be changed. Moving water can easily displace fragments [9], usually the frontal teeth being more frequently displaced by the hitting objects in water. If the teeth fall before the body is moved away by water, the initial place of deposition of the corpse may be identified [10].

Sun may discolor and crack dental tissues. The bleach of the teeth determined by sunlight can be forensically relevant, suggesting the change of their initial place after death.

Post-mortem pink teeth staining

The post-mortem pink teeth phenomenon was first described [11] by Thomas Bell in 1829, but it was not in the focus of forensic investigations for a long time [12].The pink coloration of dentin is caused by the increased intracranial blood pressure, leading to hemorrhage in the pulp chamber, while the enamel is not affected [13]. The red-pink color of tooth root is very evident near the enamel-cement junction, fading off, yet still visible under the enamel [14,15]. The phenomenon results from imbibition of hemoglobin and its degradation in the dentinal tubules. Hemoglobin could originate from either intravascular or extravascular erythrocytes [16].

The pink coloration of teeth may occur either during life (due to endodontic treatments, dental trauma and systemic diseases), or post-mortem. This phenomenon is not pathognomonic for a certain cause of death, being more frequently associated with asphyxia, maybe because of the blood extravasation due to a rapid growth of venous pressure [12,17,18]. Post-mortem pink coloration of teeth may suggest that the body stayed in a specific environment for a long time after death, as this phenomenon occurs mainly in conditions of environmental humidity, being frequently associated with water immersion, especially in bodies which lie in a head-down position [12,19,20].

Some authors associate post-mortem pink coloration with lividity, showing that it appears mainly in those regions of the jaws where blood is accumulated due to gravity [12, 21].

The type of soil may induce changes in the buried teeth.

The color of soil determines a fading area that penetrates dentin less than 1 mm. Dentin may break at the time of burial, or long after this event. The differentiation between these two circumstances is given by the coloration pattern of dentin. Thus, the dentin which cracks long after the burial shows a stained external surface with a white area beneath, while the dentin broken at the time of burial has the same colored aspect on the surface and at the fractured edges.

Acids, such as those produced by certain organic constituents of soil (peat), or by bacteria from the mouth can break teeth very fast [22,23]. Because of decalcification and enamel loss, teeth consistency is reduced up to even cutting them with a knife. This phenomenon occurs in all hard tissues of the body, so that soil acidity can completely destroy both the skeleton and teeth. An illustrative example are the bodies found in acidic peat soils in northern Europe, which are famous for preserving their soft tissue, in contrast with the poor preservation of their hard tissues [24-26].

The acids which leach into the ground by several sources, including agricultural, industrial wastes, etc., may erode both dentin and enamel. The damaged dentinal area may be outlined in black, and the exposed area may be gray and flaky. The erosion areas on the enamel are often brown and tend to occur on the labial surface of the crown near the neck line, where the enamel is thinner.

In a neutral or alkaline soil, teeth can last almost indefinitely, because they are mainly composed of hydroxyapatite [23], a calcium compound rich in inorganic material that maintains its integrity under neutral or basic environment. For example, due to the alkaline environment conditions created by a leak limestone in Indiana, animal bones and teeth dating around five million years ago were perfectly preserved [27].

Sandy soil preserves the teeth, due to a deposit of calcite, while clay soil creates channels and cavities at the bottom of the crown and root, the significance of which is currently unknown. The channels may be empty or may contain actinomycetes [27].

4. TEETH CHANGES CAUSED BY CADAVERIC DECOMPOSITION

Cadaveric decomposition (putrefaction) is a delayed bacterial process, whereby organic substances in the body are converted into inorganic substances, soft tissues and organs are destroyed and the body is transformed into a skeleton [28].

The tooth is predominantly composed of minerals, which gives it high resistance against putrefaction processes; dental pulp can be recognized up to 4-5 years post-mortem in young people. As time goes by, under the influence of environmental factors, the organic component of the tooth is destroyed, the minerals are dissolved and the tooth becomes dull white.

Putrefaction has a strong impact upon teeth and periodontal tissues, causing tooth loss, the process being faster in temporary teeth and in elders, whose teeth have different degrees of detrition. In forensic practice, for a proper consideration of the mechanism of death, it is essential to differentiate between ante-mortem and post-mortem fallen teeth. Teeth that have fallen during life leave the dental socket smooth, covered by new bone. Teeth lost after death creates a socket with sharp edges, completely empty.

In advanced putrefaction, dentin changes occur, visible by optical microscopy examination. In dentin there appear long filamentous channels, with a diameter of 2-10 μm, which penetrate the hard tissue like a corkscrew, and more numerous, branched canals with a diameter of 15-20 μm. Also, putrefaction causes cavities in cementum and dentin with smooth, regular and well-marked edges, containing actinomycetes and, possibly, modified dentin. By dentin degradation due to putrefaction, the limit between the dental pulp and dentin is no longer observed [29,30].

5. CONCLUSIONS

Teeth are the most resistant structure in the human body, which makes them valuable in forensic investigation. However, teeth may suffer important changes in their aspect and consistency after death, due to the action of environmental conditions and decomposition process. Although the changes in teeth may provide valuable information about the post-mortem interval and the environment in which the body stood after death, their significance must be cautiously interpreted, and many variables should be taken into consideration, as the environmental factors and the decomposition processes do not act in a separate manner.

References

References

1. Hall DW. Forensic Botany. In: Haglund WD, Sorg MH, editors. Forensic Taphonomy. Boca Raton. CRC Press; 1997.

2. Catts, EP, Haskell NH. Entomology and Death:A Procedural guide. Clemson, South Carolina: Joyce Print Shop;1990.

3. Haglund WD. Rodents and human remains. In: Haglund WD, Sorg MH, editors. Forensic Taphonomy. Boca Raton. CRC Press; 1997.

4. Haglund WD. Dogs and coyotes: postmortem involvement with human remains. In: Haglund WD, Sorg MH, editors. Forensic Taphonomy. Boca Raton. CRC Press; 1997.

5. Schmidt CW, Greene TR. Excavation of Human Remains. Report submitted to the Morgan County Coroner's Office and the Morgan County Sheriff's Department, Mooresville, 1998.

6. Butler VL, Schroeder RA. Do digestive processes leave diagnostic traces on fish bones? J Archaeol Sci. 1998;25:957-71

7. Rensberger JM, Krentz HB. (1988). Microscopic effects of predator digestion on the surfaces of bones and teeth. Scanning Microsc. 1988;2(3):1541-51.

8. Schmidt CW, Greene TR, Megyesi M. Analysis of an Isolated Human Mandible Recovered on the Lake Michigan National Lakeshore. Report submitted to the National Park Service, Indiana Dunes National Lakeshore, Porter, 1998.

9. Nawrocki SP, Pless JE, Hawley DE, Wagner SA. Fluvial transport of human crania. In: Haglund WD, Sorg MH, editors. Forensic Taphonomy. Boca Raton. CRC Press;1997.

10. Nawrocki SP, Schmidt CW, Williamson MA, Reinhardt GA. Excavation and analysis of human remains from the Fox Hollow serial homicide site in Hamilton County, Indiana. Annual Meeting of the American Academy of Forensic Sciences, San Francisco, CA, 1998.

11. Ortmann C, DuChesne A. A partially mummified corpse with pink teeth and pink nails. Int J Legal Med. 1998;111(1):35-7

12. Borrman H, Du Chesne A, Brinkmann B. Medico-legal aspects of postmortem pink teeth. Int J Legal Med. 1994;106(5):225-31.

13. Campobasso CP, Di Vella G, De Donno A, Santoro V, Favia G, Introna F. Pink teeth in a series of bodies recovered from a single shipwreck. Am J Forensic Med Pathol. 2006;27(4):313-6.

14. Whitaker DK, Thomas VC, Thomas RI. Post-mortem pigmentation of teeth. Br Dent J. 1976;140(3):100-2.

15. Van Wyk CW. Pink teeth of the dead: II. Minor variations. J Forensic Odontostomatol. 1988;6(2):35-42.

16. Van Wyk CW. Pink teeth of the dead: 1. A clinical and histological description. J Forensic Odontostomatol. 1987;5(2):41-50.

17. Clark DH, Law M. Post-mortem pink teeth. Med Sci Law. 1984;24(2):130-4

18. Thapar R, Choudhry S, Sinha A, Bali R, Shukla D. Pink tooth phenomenon: an enigma? J Forensic Leg Med. 2013; 20(7):912-4.

19. Matthews, JD Jr. Pink teeth resulting from Russian endodontic therapy. J Am Dent Assoc. 2000;131(11):1598-9

20. Labajo González ME, Sánchez Sánchez, JA, Buera Cienfuegos-Jovelianos BB. Post-mortem pink teeth: un curioso fenómeno. Rev Esc Med Legal, 2006;(1):35-46.

21. Sainio P, Syrjänen S, Keijälä JP, Parviainen AP.Postmortem pink teeth phenomenon: an experimental study and a survey of the literature. Proc Finn Dent Soc. 1990;86(1):29-35.

22. Pindborg JJ. Pathology of the Dental Hard Tissues. Copenhagen: Munksgaard;1970.

23. Ten Cate AR. Oral Histology, Development, Structure and Function, 4th edn. St. Louis: Mosby;1994.

24. Coles B, Coles J. People of the Wetlands: Bogs, Bodies, and Lake Dwellers. New York: Thames and Hudson;1989.

25. Glob PV. The Bog People: Iron Age Man Preserved. Ithaca. NY: Cornell University Press; 1988.

26. Painter TJ. Chemical and microbiological aspects of the preservation process in Sphagnum peat. In Turner RC, Scaife RG, editors. Bog Bodies, New Discoveries and New Perspectives. London: British Museum Press;1995.

27. Farlow JO, Sunderman JA, Havens, J. J. et al. The Pipe Creek sinkhole biota, a diverse late Tertiary continental fossil assemblage from Grant County, Indiana. Am Midl Nat. 2001;145: 367-78.

28. Ioan B. Tanatologie medico-legala- note de curs. Iasi: Junimea Publishing House;2007.

29. Dragomirescu VT. Tratat de medicina legala odonto-stomatologica. Bucuresti: ALL Publishing House;1996.

30. Plahteanu M. Odonto-stomatologie medico-legala. Iasi: Apollonia Publishing House;2000.