Are Tooth Prints a Hard Tissue Equivalence of Finger Print in Mass Disaster: A Rationalized Review.

Personal identification methods may not be efficient when bodies are decomposed, burned, in cases of mass disasters when soft tissue cannot provide reliable information or has been lost. Various methods currently employed in forensic odontology for personal identification include comparing with antemortem dental charts, rugoscopy, denture labeling, DNA analysis from dental pulp, bite mark analysis, etc., Recently, there is growing interest in the study of enamel rod end patterns. These enamel rod end patterns are termed as "Tooth prints" and the study of these prints is known as "Ameloglyphics" (amelo: Enamel, Glyphics: Carvings). This review encompasses about the basis of using enamel rod end patterns, methods of obtaining the patterns and further suggests these tooth prints as an analogy to finger print in personal identification in mass disasters.

INTRODUCTION

The term mass disaster means a chaotic event, initiated by a destructive force, which results in the multiple fatalities necessitating identification. The identification of large number of casualties in mass disaster is complex due to severe mutilation, charring and decomposition. The routine identification data fall short in such cases. Teeth are the hardest and chemically most stable tissues in the body. Moreover, teeth and jaws are usually well-protected from fire and mechanical trauma and are highly resistant to postmortem destruction and decomposition. Hence, dental identification is one of the most reliable methods of comparative identification in cases of mass disasters. Human dentition is considered hard tissue analog to fingerprints (reliable tools only in a body obtained before decomposition or mutilation).[1] Teeth are considered to be the most indestructible components of the human body, which have the highest resistance to most environmental effects such as fire, desiccation, and decomposition. Tooth is composed of enamel, dentin, pulp, and cementum of which enamel and dentin are highly calcified structures in the body that resist decomposition.[2] Tooth prints is the term used to describe the enamel rod end patterns. Ameloglyphics is the term used for the study of patterns of enamel rods. Enamel does not remodel nor does it remain in close contact with the cells which synthesize it; rather the ameloblasts retract away from the enamel surface once it has matured and the tooth has erupted. Enamel prisms morphology reflects the morphology of ameloblasts in a species-specific manner. Alterations to the matrix are reflected as defects in the structural organization of enamel. The enamel rod end patterns could be duplicated by various methods, such as using cellulose acetate paper and rubber base impression materials. Human identification either dead or alive is most important in forensic investigations. It is usually achieved by the use of passwords, physical tokens, photographs, iris, dental patterns, fingerprints, and more recently DNA analysis. These methods are not useful in cases where the bodies are totally decomposed or burnt, where only remnants of calcified tissues such as bone and teeth fragments are evident. In such situations, dental hard tissues gain importance for identification based on the condition of the deceased. The uniqueness of the tooth print could be used as a valuable tool in forensic science for personal identification.[2] The term “Ameloglyphics” means the study of enamel rod end patterns (amelo: Enamel, Glyphics: Carvings). Tooth print is the word used to describe these enamel rod end patterns.[3]

ENAMEL-TOOTH PRINTS

Enamel is the hardest substance in the body. Enamel is a product of ectoderm derived cells called ameloblasts.”[4] The basic structural unit of enamel is the enamel rods (enamel prisms). Enamel does not remodel or does it remain in close contact with the cells which synthesize it; rather the ameloblasts retract away from erupted.[1] The development of enamel is a complex organized process, where the ameloblasts lay down the enamel rods in an undulating and inter-twining path. Macroscopically, the incremental pattern of enamel rods is exhibited on tooth surface as perikymata, but microscopically, groups of enamel rods run in unique direction, which differ from adjacent group of enamel rods and results in forming different patterns of enamel rod endings on tooth surface. These series of lines running in various directions forming various subpatterns which were unique to the individual tooth.[5] These patterns on the enamel surface are called as tooth prints, and the study of enamel rod end patterns on tooth surface is termed as ameloglyphics.

ORIENTATION OF ENAMEL RODS

The general orientation of the enamel rods is perpendicular to the dentin surface. In deciduous teeth, the enamel rods lie in a horizontal plane in the cervical and middle third. They gradually become more oblique in the incisal and occlusal third and are almost vertical in the incisal edge or the cusp tip. In permanent teeth, the arrangement is similar to deciduous teeth in the occlusal and middle third; in the cervical third, the enamel rods show a root ward inclination or pass outward [Figure 1].[6]

Figure 1

Orientation of enamel rod end patterns

AN HOTCHPOTCH OF TYPES OF ENAMEL ROD END PATTERNS

Wavy un-branched

Linear branched

Linear un-branched

Whorl open

Whorl closed

Loop (L)

Stem Like [Figures 2-10].[7]

Figure 2

Wavy branched

Figure 10

Patterns of enamel prisms

Wavy un-branched

Linear branched

Linear un-branched

Whorl open

Whorl closed

Loop

Stem Like

METHODS USED IN RECORDING ENAMEL ROD END PATTERNS

In ameloglyphics, recording of enamel rod endings on tooth surface is proceeded using acid etchant, acetate peel technique, and automated biometrics as sequential steps for reproducing complete and accurate enamel rod end patterns for personal identification.[2]

Acid etching

Acetate peel technique

Automated biometrics.

Acid etching technique

Acid etching: [Figure 11]

The acid etching on the surface enamel results in the removal of the surface mineral component in the rod and rod sheath. As the rods and rod sheaths have a different mineral density, the etching results in an uneven dissolution of the surface enamel along with the removal of the smear layer.

The effect of acid etching on enamel depends on:

Kind of acid used

Acid concentration

Etching time

Form of etchant

Rinse time

Whether enamel is instrumented before etching

Chemical composition and condition of enamel.[8]

About 10% orthophosphoric acid in gel form is the most commonly used acid to condition the enamel for in vivo studies.

Three types of etch patterns can be obtained:

Predominant dissolution of prism cores

Predominant dissolution of prism peripheries

No prism structure is evident.[9]

Photomicrography of acetate peel technique using verifinger standard SDK version 5

Peel technique: [Figure 12]

Peel is a replica of an acid-etched mineral surface, made on acetate film. Peeling is a simple, inexpensive, and rapid way of making replicas of dental hard tissue surfaces. The peel-making technique was first developed by palaeobotanists to study the cellular structures of fossil plants and later taken up by palaeobotanists, carbonate petrologists, and paleontologists to study both the texture and structure of carbonate rocks and fossils.

Further modifications were done to study dental hard structures due to its unique mineralogical composition.[10] The peel can be examined under microscope with the incident or transmitted light or with combinations of both and can be stored for posterity.[2]

Photomicrography of biometric generation using verifinger standard SDK version 5

Biometric analysis: [Figure 13]

The term “biometrics” refers to identification techniques which are based on specific physical characteristics. It is a technology of identification or authentication of a person which transforms a biological, morphological or behavioral characteristic in a digital value. When the patterns studied are consistently recognized and provide greater confidence, they are referred to as positive identification.” Biometric-based identification and verification methodologies such as fingerprint verification, iris scanning, and facial recognition have been steadily improved and refined in automated systems and softwares, which have the capacity to distinguish individuals reliably. Unique identification of an individual based on biometric information should have certain desirable prerequisite characteristics: Highly unique to each individual, easily transmittable, able to be acquired as un-intrusively as possible and distinguishable by humans without much special training.[11]

Re-creation of human identity possible using tooth prints to aid in personal identification

Enamel rod end patterns are unique for each tooth in an individual and may be used as an adjunct with other methods for personal identification. This technique is simple, inexpensive, and rapid method which can be performed by even a dental auxiliary staff. Usually, this method of personal identification can be included as adjunct antemortem dental records of fire fighters, soldiers, jet pilots, divers, and people who live or travel to politically unstable areas. And this record must be updated periodically to overcome the enamel loss due to wear and tear.[12] In comparison of tooth prints with that of the finger prints, this is composed of a single distinct pattern such as whorl, loop or arch. Whereas a tooth print is composed of combination of basic subpatterns.[1]

CONCLUSION AND RECOMMENDATIONS

Ameloglyphics as yet a nascent field is gaining popularity as a tool in personal identification. Though a reliable technique has some limitations to it as there is a need for antemortem records for the matching and also the reliability and credibility of fingerprint analyzing software (Verifinger) in the analysis is unknown. Even though tooth prints are unique to an individual tooth, the value of it as a tool in forensic science for personal identification depends on its reproduction and permanency. Further studies are required to explore its significance in personal identification especially in mass disasters. Hence, the concept of tooth prints is not a myth but a reality which will come true in the near future if research is carried out in the right manner in the right direction.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.