Bite marks--the criminal's calling cards.

Carnivorous animals, like dogs or tigers, use their teeth in two distinct ways. They kill their prey primarily using their canines and they tear and slice the flesh to produce digestible fragments. Human teeth are designed principally to cut and grind food which is usually previously prepared. Some people appear to revert to more primitive instincts and use their canines and incisors to inflict bites on unsuspecting victims.

Difficulties in estimating age using root dentine translucency in human teeth of varying antiquity.

Estimation of age at death is an essential part of reconstructing information from skeletal material. This becomes more difficult after development has ceased and following taphonomic alteration in archaeological material. Most biological markers of age do not record the chronological age (calendar age), but the biological or physiological age of the individual. Of the age-related changes in the mature dentition of modern samples, the extent of root dentine translucency (RDT) has been shown to correlate closely with chronological age. A protocol for measurement of RDT was established and applied to modern and archaeological teeth of known age (Spitalfields sample). Percentage length of RDT in sectioned teeth was found to correlate well with chronological age in the modern sample but not in the archaeological sample. The majority of the archaeological sample was affected by a morphological change creating a "chalky" appearance to the dentine. Removal of the obviously affected teeth did not improve the correlation coefficients to any useful degree. "Chalky" dentine appeared, under the light microscope, to be composed of large fenestrations, islands of mineralized tissue and masses of filiform structures that appeared to be following the path of the dentinal tubules in their invasion of the peripheral dentine. The filiform structures are consistent in their appearance with a previously reported tunnelling mycelium and impart such an effect on RDT that it cannot readily be used for age estimation in affected teeth.

The effects of dental wear on third molar eruption and on the curve of Spee in human archaeological dentitions.

The abrasiveness of food is a key determinant in the rate of physiological attrition (dental wear) in humans. With increasing food processing through time, the rate of physiological dental wear in human teeth has decreased markedly. Many consider such wear to be beneficial to oral health and that insufficient wear may result in impaction of the third molars. If enhanced extraoral food processing provides an evolutionary advantage, then it is possible that agenesis of the redundant third molar may follow. One of the aims here was to examine impaction and agenesis of the third molars in four populations of varying antiquity and hence varying dental-wear rates. Paradoxically, whilst there is a decrease in the rate of dental wear with modernity, there is also an increasing prevalence of advanced dental wear due to prolongation of the lifespan of the human dentition. As the effect of dental wear on the curve of Spee was unknown, a second aim was to examine it in an archaeological population with a high rate of dental wear. The results showed an increase in non-eruption and impaction of the third molars with modernity, but did not demonstrate a significant increase in the rate of agenesis. The time period over which impaction and agenesis could be discerned was of the order of 600 years and this may not be sufficient to observe adaptive changes at the genetic level in humans. In molar teeth there was no clear indication of maintenance of the curve of Spee with dental wear. This has potential implications on the design of prostheses for the worn dentition.

A comparison of the ability of experts and non-experts to differentiate between adult and child human bite marks using receiver operating characteristic (ROC) analysis.

Fifty colour prints of human bite marks were sent to 109 observers who were asked to decide using a six point rating scale, whether the marks had been produced by the teeth of an adult or a child. The observers consisted of accredited senior forensic dentists, accredited junior forensic dentists, general dental practitioners, final year dental students, police officers and social workers. The results were compared against a "gold standard" which was the actual verdict from the case. Comparison of the results between the groups of observers and the standard was made using Receiver Operating Characteristics (ROC) methodology. The best decisions were made by senior/junior experts or final year dental students. General dental practitioners and police officers were least able to differentiate correctly between adult and child bite marks. The effect of training is important and its effects need to be assessed in more detail in future studies.

Orthodontic reconstruction in a victim of murder.

Accurate comparison of ante-mortem photographs and the skull of a deceased person is dependent upon suitable superimposition techniques and a post-mortem dentition which is comparable to the situation obtaining in the individual at the time of death. The skull featuring in this case presented with a missing upper lateral incisor, lost after death, and the occlusion was studied enabling a replacement tooth to be provided and positioned as in life. Although no dental records were available, good quality photographs of a putative identity were compared by electronic superimposition and the restored occlusal characteristics of the skull were shown to accurately match the photographs of one possible victim. This evidence resulted in positive identification by a Coroner. This case illustrates the importance of seeking specialist clinical advice in forensic dental cases.

Calculus deposits and bone loss on the teeth of Romano-British and eighteenth-century Londoners.

The relation between dental calculus and periodontal disease is not clear but it is generally recognized that calculus is a significant pathogenetic factor. Skeletal material has previously been used to study some aspects of chronic adult periodontitis but few studies have quantified the extent of calculus in ancient populations and its relation to changes in alveolar bone height. This study records the presence and extent of calculus and its relation to alveolar bone loss in a Romano-British and eighteenth-century London population. There were significant differences in calculus deposition in the two populations but this appeared to have little effect on changes in alveolar bone contour. It is suggested that the amount of calculus may be related to diet but that changes in alveolar bone height seem to be independently controlled.

Racial variations in the extent of tooth root translucency in ageing individuals.

One hundred and ninety-eight single-rooted teeth from individuals aged 21-90 yr of Caucasian, Malay, Chinese Malay and Indian Malay origin were studied. Single or serial longitudinal sections of extracted teeth were cut following dye imbibition of patent dentinal tubules. The extent of sclerosis of apical dentinal tubules was assessed and correlated with the age of the individual. Correlation with age was higher in the Caucasian than the Malay races and within the Malaysian racial groups correlation with age was highest in the Malays and lowest in the Chinese. It is concluded that factors other than age may be important in the formation of sclerotic apical dentine in teeth of different racial origin. The effect of racial origin should be considered when using sclerosis as a means of age determination in forensic cases.

Caries prevalence in the dentition of a late eighteenth century population.

Remains of 92 individuals of known age and a further 71 of unknown age were selected from nearly 1000 skulls exhumed from the crypt of Christ Church, Spitalfields. Ante- and post-mortem tooth loss was assessed and caries prevalence and distribution were studied. Post-mortem loss of teeth was highest in the oldest age group, suggesting that greater care is needed during exhumation to minimize this loss. Juvenile caries levels were high, especially on occlusal surfaces of deciduous molars. Approximal caries was less frequently seen and buccal and lingual sites were only slightly less frequently involved than approximal sites. Root caries was rare, even in the oldest age group. There were differences in prevalence and distribution between males and females but not between those of English and French origins. Caries levels were generally higher in those born after 1750. It is suggested that factors other than diet and oral hygiene may have influenced caries prevalence in this population.

Forensic dentistry in the identification of victims and assailants.

The teeth are the least destructible part of the body and may remain more or less intact for many years beyond death. In addition, because of their stability in a biological sense, and because during their formation disease may affect the hard tissues of the teeth themselves, they contain information about the physiological and pathological events in the life of the individual which remain as markers within the hard tissues of the teeth. Therapeutic activity by a dentist in the form of restorations and prostheses may modify an individual's dentition in a more or less unique manner. It is the role of the forensic dentist to assess this biological and chemical information, and use it in the identification of an unknown body. The teeth may also be used to inflict injury on a victim in the form of a bite. The resulting bite mark may not only indicate the degree of aggression during the assault but if sufficient details are available within it, may enable the forensic dentist to determine the identity of the assailant. This important aspect of forensic dentistry is commonly required in non-accidental injuries to children and in instances of grievous bodily harm, rape and murder of child or adult.

3-D reconstruction of an ancient Egyptian mummy using X-ray computer tomography.

Computer tomography has been used to image and reconstruct in 3-D an Egyptian mummy from the collection of the British Museum. This study of Tjentmutengebtiu, a priestess from the 22nd dynasty (945-715 BC) revealed invaluable information of a scientific, Egyptological and palaeopathological nature without mutilation and destruction of the painted cartonnage case or linen wrappings. Precise details on the removal of the brain through the nasal cavity and the viscera from the abdominal cavity were obtained. The nature and composition of the false eyes were investigated. The detailed analysis of the teeth provided a much closer approximation of age at death. The identification of materials used for the various amulets including that of the figures placed in the viscera was graphically demonstrated using this technique.

An introduction to forensic dentistry.

Dental science has much to offer law enforcement agencies in the detection and solution of crime. The permanent teeth develop throughout the first two decades of life, and physiologic variations, pathoses, and the effects of dental therapy may be recorded in the hard tissues of the remaining dentition throughout life and beyond. It is the role of the forensic dentist to extract this information and use it in the identification of the unknown body. The teeth may also be used as weapons and, under certain circumstances, may leave information as to the identity of the biter. Analysis of bite marks is the second major responsibility of the forensic dentist. The general practitioner has a major role to play in providing the accurate dental records on which much of forensic activity is based.

The effects of putrefaction on haptoglobin phenotyping from tooth fragments.

Tooth fragments freshly extracted from humans were stored for various times and temperatures under both dry and moist conditions. The fragments were reduced to powder and proteins eluted. Purified haptoglobin fractions were separated, detected and phenotyped using the Phast Gel electrophoresis system using gradient gels. Haptoglobin phenotypes were demonstrable but became less detectable as time increased.

A comparative study of translucent apical dentine in vital and non-vital human teeth.

Previous studies have shown that dentinal apical translucency increases with age. Although the mechanism by which apical translucency is produced is still uncertain, it has been suggested that it develops at a slower rate in non-vital teeth. In this investigation the amount and distribution of apical translucent dentine in a group of age-matched vital and non-vital teeth were compared. Fifty-five non-vital (root-filled) teeth and 49 vital teeth were used. Freshly extracted teeth were fixed in 2% glutaraldehyde solution, sectioned longitudinally in the buccolingual plane and ground to a thickness of 150 microns. Each section was photographed in polarized light at a standard magnification against a ruled scale background. Black-and-white prints of standard magnification were produced and translucent apical dentine was plotted using an Apple II digitizer. Variables measured were length, length as a percentage of root length, area and area as a percentage of root area. Data were related to age and tooth type and analysed by Mann-Whitney and regression analysis. Significant differences (p < 0.05) were present when tooth types were pooled. There was more apical translucency present in all types of non-vital teeth when compared with vital teeth at any given age.

Dental restorations and artificial teeth in a Georgian population.

In the recent exhumation of a predominantly Georgian population at Christ Church, Spitalfields, 12 skulls showed evidence of dental restorations or artificial teeth. These have been described in some detail and the findings discussed in the light of current knowledge about practical dentistry in England up to the year 1852.

Principles of forensic dentistry: 2. Non-accidental injury, bite marks and archaeology.

From time to time the general dental practitioner may become involved in forensic cases, when he or she will need to be aware of the general principles involved and the increasing variety of modern techniques available. This two-part article reviews those principles and techniques. In Part 1 the principal procedures used in identifying bodies were discussed. Part 2 now reviews the role of the forensic dentist with respect to non-accidental injury to children, analysis of bite marks, and archaeological investigations.

Principles of forensic dentistry: 1. Identification procedures.

From time to time the general dental practitioner may become involved in forensic cases, when he or she will need to be aware of the general principles involved and the increasing variety of modern techniques available. This two-part article reviews those principles and techniques. In Part 1 procedures used in identifying bodies are discussed. Part 2 will concentrate on non-accidental injury to children and analysis of bite marks, and discuss archaeological investigations.

Use of benzidine for histological demonstration of haemoglobin in human bite marks.

Macroscopic evidence of bruising from human bite marks may be inconclusive and routine histochemical methods of showing extravasated erythrocytes can be unreliable. Leuco patent blue staining, for the presence of peroxidase, Amido black B, a tinctorial staining method for haemoglobin, Perls's reaction for ferric iron (haemosiderin), Masson-Fontana for melanin, Masson's trichrome, a connective tissue strain, and the benzidine reaction for haemoglobin peroxidase were carried out in three forensic cases and one experimental case. A modified benzidine method was the most reliable indicator of haemoglobin activity, especially where dispersion into extra-cellular tissues had occurred. The resilience of the erythrocyte peroxidase enzyme to temperature changes and fixation supports the concept of a "pseudo-peroxidase" in those cells. It is concluded that free haemoglobin from bite marks, or indeed other forms of blunt trauma, may best be shown by the benzidine reaction and that exemption certificates for use of this prohibited substance may be worth pursuing.