Introduction
The mysterical phenomenon of pink tooth was first of all brought into light by Thomas Bell in 1829 who described this phenomenon in teeth of victims of drowning and strangulation cases.[1] This phenomenon involves discoloration of dentin with enamel remaining unaffected. The pink discoloration observed is mainly confined to the cemento-enamel junction of the involved tooth and this discoloration fades off as the distance from cemento-enamel junction increases.[1] The role of pink tooth phenomenon has also been implicated in mass disaster situations. In tsunami incident of Indonesia in 2004, pink tooth was observed in many unknown victims (Fig. 1 & Fig. 2) (Stravrianos 2009)[1] and several dead bodies of the victims were decomposed and were present in extremely humid environment (Petju et al., 2007)[2]

Fig 1 : Skull Of The Victim Revealing Presence Of Post-mortem Pink Teeth Phenomenon In Open Mouth Condition.

Fig 2 :Skull Of The Victim Revealing Presence Of Post-mortem Pink Teeth Phenomenon In Occlusion

Mysterical Post-mortem Pink tooth Phenomenon
Pink tooth is seen in subjects who met a sudden and unnatural death with subsequent exposure to the humid environmental conditions. Discoloration primarily affects dentin sparing enamel (because of hardness). Discoloration occurs at CEJ and slightly fades off beneath enamel (Van Wyk., 1988, 1989; Whittaker et al 1976).[3],[4] The appropriate reason of the staining due to pink tooth phenomenon is not known but it is said that in incidents involving unnatural death there is increased intracranial pressure that results in pulpal hemorrhage with breakdown of haemoglobin. There occurs seepage of the breakdown products in the dentinal tubules causing pink discoloration.[3] Presence of time lag is cited as important cause in event of pink tooth phenomenon. This time lag is thought to arise as result of diametrical difference among dentinal tubules and erythrocytes.[3] The element of time lag along with humid environment is responsible for pink tooth phenomenon. It is seen that along with humid environment the physical factors at the time of death are responsible for this pink tooth phenomenon.[3]

Etiology of pink tooth
Various studies have been done to identify the exact cause of event of pink tooth. Ikeda et al (1988) by his electron probe X-ray micro-analysis hypothesized that haemoglobin derived iron is responsible for pink tooth.[6] Van Wyk., 1989; Stravrianos , 2009 found that in cases of unnatural death like strangulation , murder there is increased intracranial pressure that causes haemolysis resulting in the formation of derivative products with subsequent seepage of the derivative products into the dentinal tubules.[1],[3] This haemoglobin which was thought to undergo haemolysis, originates from intravasated erythrocytes or from extravasated erythrocytes in congestion bleeding (Van Wyk., 1989; Matthews., 2006; Stravrianos., 2009).[3],[5],[1]
Borrman et al (1994) and Ortmann & Duchesne (1998) reported the event of pink discoloration in teeth with less compact dentin and more dentinal tubules.[8],[7] Van Wyk (1989) after is cadaveric study tried to correlate the time sequence of the coloration with the pattern of blood hemolysis and said that pink staining can only occur after pulpal hemolysis & this pink discoloration becomes evident macroscopically at about 6 days.[3] He explained that because of this time lag pink discoloration can occur after RBC hemolysis allowing seepage of haemoglobin and its breakdown products into the dentinal tubules.[1] Van Wyk concluded that pink discoloration was not attributable to the hemosiderin, bile & bile related pigments as porphyrins but was actually due to the time lag observed between death and ingress of blood products into the dentin due to the difference in diameter of dentinal tubules (3μm) and ingressing erythrocytes (7.5μm).[1] Kirkham et al in 1977 stated that apart from haemoglobin and its breakdown products factors such as age, vascularity of the pulp chamber, and post-mortem conditions are also contributory to the post-mortem development of pink teeth.[9]
Matthews (2000) and Campabasso et al. 2005 found that pink discoloration seen in case of pink tooth phenomenon after dead ,can also be seen in living individuals as in case of endodontic therapy, traumatic assaults, internal resorption and in normal physiological process of resorption and exfoliation.[5],[10] Dye et al 1995 reported a similar kind of pink discoloration in teeth obtained archaeological samples and they concluded that the pink discoloration was probably related to post-mortem change brought about by tunnelling of hyphae of saprophytic fungi.[11]

Discussion
Pink discoloration apart from being evident in victims of drowning and asphyxia is also seen in subjects who died suddenly and unnaturally as in murder cases but still there is general consensus that no definite connection is there between occurrence of pink tooth and cause of death. Bormann et al., 1994 and Campabasso et al., 2006 concluded that pink tooth is not pathognomic for a specific cause of death therefore being an unspecific phenomenon.[8],[10] Whittaker et al (1976) based on his study on golden hamsters in which grouped golden hamsters into two groups. Golden hamsters in one group were strangled and in other group were barbiturate poisoned.[4] From each group half of the hamsters were buried in soil and half were buried in sea water. Whittaker observed that pink discoloration took 2-3 months to be evident and was more intense and faster in animals that were strangled.[4] Ortmann and DuChesne in 1998 reported that in cases of pink tooth discoloration there is concurrent presence of combination of intoxication, hypothermia & pneumonia all of these three can be established as the cause of death.[7] Van Wyk in 1989, based on his cadaveric study tried to correlate time sequence of pink coloration and pattern of hemolysis and he came up with the conclusion that pink staining can occur only after hemolysis and discoloration when evident occurs after 6 days.[3] Campabassoet al in 2006 studied the relationship of frequency and distribution of post-mortem discoloration of teeth among the sample of 52 cadavers of shipwreck incidence and concluded that pink discoloration was more pronounced in younger age group (13-16 yrs.).[10] In 2009 Soriano et al suggested that pink discoloration is seen in victims who have been strangulated with more prominence at the neck of the tooth.[12]

Conclusion
Although being known from 1828, applications of pink tooth phenomenon in forensic dentistry are limited.[6] The formation of pink tooth is recurring and unpredictable phenomenon as the ante-mortem prerequisites are nonspecific and may be replaced by certain post mortem conditions.[1] Pathologists have to be aware of that no final conclusions are drawn for any case or mechanism of death just on the basis of finding of pink tooth .[1]

References
1.    C. Stavrianos, L. Vasiliadis , C.Papadopoulos, O. Pantelidou, K. Tolidis, P. Dagkalis. The Post-Mortem Pink Teeth Phenomenon. Res. J. Biol. Sci. 2011; 6(3):124-127
2.    Petju M., Suteerayongprasert A., Thongpud R., Hassiri K.Importance of dental records for victim identification following the Indian Ocean tsunami disaster in Thailand. J of Public Health. 2007: 121:251–257
3.    Van Wyk CW. Post-mortem pink teeth: in vitro production. J. Oral Pathol. 1988; 17:568 – 572.
4    Whittaker DK, Thomas VC, Thomas RIM. Post-mortem pigmentation of the teeth. Br Dent J. 1976; 140:100 –102.
5.    Matthews JD Jr. Pink teeth resulting from Russian endodontic therapy. J Am Dent Assoc. 2000; 131:1598-9
6.    Ikeda N. Watanabe, A., Harada and T. Suzuki, 1988. A scanning electron microscopy and electron probe x-ray microanalysis (SEM-EPMA) of pink teeth. J. Forensic Sci., 51:109-112
7.    Ortmann C, DuChesne A. A partially mummified corpse with pink teeth and pink nails. Int.J Legal Med. 1998; 111:35-7.
8.    Borrman H, Du Chesne A, Brinkmann B. Medico-legal aspects of post-mortem pink teeth. Int. J Legal Med. 1994; 106:225-31.
9.    Kirkham WR, Andrews EE, Snow CC, et al. Post-mortem and traumatic pink teeth. J Forensic Sci. 1977; 22:119 –131.
10.    Campabasso 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; 27:313-6
11.    Dye.T.J. D.Lucy and A.M. Pollard. The occurrence and implications of post-mortem pink tooth in forensic and archaeological cases. Int. J. Osteoarchaeol.1995; 5: 339-348
12.    Soriano E.P, M.V.D Carvalho, F.B Santos, C.C. Medoza , M.S.D. Araujo, R.I.C Campello ,2009. The post-mortem pink teeth phenomenon: A case report. Med. Oral Pathol .Oral Cir Bucal, 14: E337-E339