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.     

Photography in bite mark and patterned injury documentation--Part 1

A case involving multiple bite marks is presented. The bite marks were photographed over a 31-day period to document the injuries and preserve their evidentiary value. The evidence recovered at each photography session is discussed and photographs are presented for review. Suggestions concerning the need for more research are presented.     

The effects of dental condition on hand strength and maximum bite force

Piezoelectric force transducer and hand dynamometer were used for measuring the maximum bite force and hand grasp force on 2034 primary, middle, and high school students. Dental condition and body weight and height were also observed to relate to the force measurements. It was discovered that both forces increased relative to the increase of age, body weight, and body height. Boys had stronger bite force than girls at all age groups, while the grasp force of boys became significantly stronger only after the age of 13. Students who had dentition with decay and missing teeth tended to have weaker bite force, while hand force was not influenced. Bite force does not seem parallel to hand strength and is, instead, related to dental condition.     

Shortening versus isometric contractions in isolated human failing and non-failing left ventricular myocardium: dependency of external work and force on muscle length, heart rate and inotropic stimulation

Dental literature supports the concept that vertical dimension of occlusion is normally not lost in severely worn dentition, and the bite should generally not be opened to facilitate dental reconstruction. However, restoration of a periodontally sound but severely worn dentition, at existing vertical dimension, frequently presents unique challenges in patient management, diagnosis, treatment planning, and restorative methodology. This report reviews and demonstrates an integrated and planned approach to this complex treatment situation that can lead to a favorable and predictable prognosis. The approach also allows a practitioner free use of various techniques if certain goals of occlusion are followed.     

Phenomenological Description of the Surface Morphology and Crack Formation of Continuously Cast Peritectic Steel Slabs

The surface quality of continuously cast material is strongly depending on the initial solidification of the steel. Oscillation marks are formed at the very early stages of the strand shell growing process, thus influencing the microstructure and cracking behaviour of the surface and subsurface region. An industrial study of the oscillation mark morphology and the surface structure of peritectic medium carbon steel slabs was performed. The formation of oscillation marks and their effect on the surface quality was examined by metallographic investigations of slab samples. Although constant casting and oscillation conditions were applied, a variation of oscillation mark geometry along the narrow faces of the slabs was measured. A relation between the depth of the oscillation marks and the thickness of a layer of segregated melt situated inside the bottom of the marks was found. Measuring the distribution and length of surface and subsurface segregated cracks in the vicinity of the marks, existing theories of oscillation mark formation could be confirmed. The austenite grain size was found to increase with increasing oscillation mark depth. There was no clear correlation between the austenite and the δ‐ferrite grain size.     

Fourth ventricular entrapment caused by rostrocaudal herniation following shunt malfunction

The aim of this study was to assess differences in dental health between socioeconomic and ethnic groups in a cohort of 5-yr-old children born in 1982 and in a cohort of 11-yr-old children born in 1976. A further aim was to evaluate the putative role of dental behaviors as intervening factors between ethnicity and maternal education on the one hand and caries experience on the other. A secondary analysis was performed on data collected in a study monitoring the oral health of youths covered by public health insurance (Ziekenfonds) in the Netherlands. The results showed both ethnicity and maternal education to be indicators of caries risk in the primary dentition. For caries in the permanent dentition, only maternal education could be identified as a risk indicator. Dental behaviors were related to caries experience as well as to ethnicity and maternal education, though the evidence for the role of these dental behaviors as intervening factors was weak. It is concluded that the validity and reliability of the behavioral measurements might be questionable and that the mechanism underlying the differences in caries experience between the various groups is still little understood.     

Computer-based production of bite mark comparison overlays

Bite mark comparison protocols include measurement and analysis of the pattern, size, and shape of teeth against similar characteristics observed in an injury on skin or a mark on an object. The physical comparison of tooth position often depends upon transparent acetate overlays to detect similarities or differences between the teeth and the bite mark. Several methods are used to produce life-sized comparison overlays. The perimeter of the biting edges of the anterior teeth are usually recorded to produce facsimile images called hollow volume overlays. Some investigators hand-trace these outlines from dental study casts, or from bite exemplars produced in wax, styrofoam, or similar materials. Some use hand-traced outlines from xerographic images produced with office photocopiers that are calibrated to produce life-sized final images. Others use radiographic images and toneline photography of wax exemplars filled with radio-opaque materials, such as metal filings or barium sulfate. Dependence upon subjective input by the odontologist to trace these images manually is considered problematic. This is because the errors incorporated at any production stage are increased in the final product. The authors have developed a method to generate accurate hollow volume overlays using computer-based techniques. A PowerPC Macintosh computer, flatbed scanner, and Adobe Photoshop (a popular graphical interface application) are used to acquire, select, arrange and export detailed data from class and individual characteristics of a suspect's teeth to acetate film loaded in a high-resolution laser printer. This paper describes this technique to enable the odontologist to produce high-quality, accurate comparison overlays without subjective input.     

Evoked potentials as predictors of outcome in neonatal intensive care unit survivors: review of the literature

The twin blocks technique was developed by Dr. William Clark of Scotland during the early 1980s. Twin Blocks are an uncomplicated system that incorporates the use of upper and lower bite blocks. These bite blocks reposition the mandible and redirect occlusal forces to achieve rapid correction of malocclusions. They are also comfortable and the patients wear them full-time--including eating time. Occlusal forces transmitted through the dentition provide a constant proprioceptive stimulus to influence the rate of growth and the trabecular structure of the supporting bone. This feature of Twin Blocks means easier and quicker treatment. The occlusal inclined plane is the fundamental functional mechanism of the natural dentition. Twin Blocks are bite blocks that effectively modify the occlusal inclined plane to induce favorably directed occlusal forces by causing a functional mandibular displacement. Upper and lower bite blocks interlock at a 45 degree angle and are designed for full-time wear to take advantage of all functional forces applied to the dentition including the forces of mastication. The patients who were treated with Modified Twin Blocks received the following benefits: 1) large overjets and deep overbites were corrected. 2) Class II molar relationships were changed into Class I, and 3) the profiles of the patients were improved by anterior displacement of mandible.     

Experimental study of oscillation mark depth in continuous casting of steel

Abstract

Mould oscillation is needed to reduce friction and thus prevent sticking and breakout of the liquid metal during casting. However, this oscillation is known to cause surface defects in the solidified steel slabs, so called oscillation marks. In this paper, the depth and the depth variation of these oscillation marks were studied using a two-level full factorial experiment (2) with four additional centre point runs. Four factors were studied: stroke length of the mould, oscillation frequency, motion pattern (strip factor) and casting speed. The stroke length affected the depth of the marks the most, where larger strokes created deeper marks. The interaction between the oscillation frequency and the strip factor of the mould also affected the oscillation mark depth. The oscillation mark depth variation was also increased by increased stroke lengths and at higher oscillation frequencies. The largest effect on the oscillation depth variation was found for the interaction between the stroke length and the oscillation frequency.     

Traumatic dental injuries in a cohort of 16-year-olds in northern Sweden

The prevalence and yearly incidence of traumatic tooth injury between 1 and 16 years of age were studied in a cohort of 16-year-olds, born in 1975, and residing in the County of V?sterbotten, northern Sweden. The study comprised 3007 dental records from the public dental health service. The general distribution was 50.3% girls and 49.7% boys. The records showed that 35% of the children on one or more occasions had sustained injury to their primary or permanent dentition. The frequency was nearly twice as high for boys (64%) as for girls (36%). Twenty-five percent of the 16-year-olds had met with tooth injury more than once and this group consisted predominantly of boys. The incidence of injury episodes to primary and permanent teeth was 28 per 1000 per year. The boys had sustained trauma to their teeth most frequently when they were 4 years of age and between the ages of 8 and 11. This was also true for girls at 4 and at 9 years of age, although less evidently so. In the primary dentition, the majority of dental injuries had affected the supporting tissue of the maxillary incisors. In the permanent dentition, 75% of the traumatised teeth were upper incisors. Fractures of varying severity constituted 60% of all registered diagnoses in this dentition, followed by subluxation (19%) and concussion (11%).     

Oral and systemic effects of prolonged minocycline therapy

The following case report shows the unfortunate side effects of minocycline therapy used in the management of facial acne. All three features of discoloration affecting the skin, bone and dentition were found. A 46-year-old patient presented with adult onset discoloration of the dentition following prolonged minocycline therapy. In addition, oral and cutaneous pigmentation were noted. Unfortunately, the undesirable cosmetic appearance of facial acne was exchanged for permanent discoloration of the dentition. When considering prolonged minocycline therapy, patients would benefit from dialogue between the medical and dental practitioners, so that the risk of this potential side effect can be assessed in a more informed way.     

Experimental determinations of carcass processing by Plio-Pleistocene hominids and carnivores at FLK 22 (Zinjanthropus). Olduvai Gorge, Tanzania

Published and unpublished skeletal and surface mark data from the large, well-preserved, bovid dominated FLK 22 (Zinjanthropus) archaeofauna are analyzed using data derived from four different experimental control samples. The control samples are realistic because they are based on natural history and paleoecological data collected from FLK 22, and other Olduvai Gorge assemblages; they are precise because independent experimental studies following the same methods have generated the same results; and they restore generality to the study of site formation because each one models a different hominid and/or carnivore scenario of site formation. Comparability between FLK 22 and the control samples is established by excluding specimens from the former which do not meet identification and reporting standards derived from the latter. As in two previous studies, a comprehensive analysis of tooth marks and tool marks on long bone specimens from FLK 22 indicates that they were processed in three stages. In stage one, carnivores defleshed long bones, as inferred from the high percentage of tooth marks on midshaft fragments. In stage two, hominids processed intact long bones for marrow, as inferred from percussion mark percentages. Cut marks suggest that long bones retained flesh, but the amount, as yet, cannot be determined using cut mark percentages. In stage three, carnivores processed long bone epiphyses for grease, as inferred from the under-representation of long bone epiphyses and the high percentage of tooth marks on near-epiphyses and surviving epiphyses. The lack of comprehensive skeletal and surface mark data on cranial, axial, compact, and other specimens currently limits the application of experimental results. However, the available data suggest that the condition and representation of these items in the FLK 22 assemblage are also consistent with a carnivore to hominid to carnivore sequence of site formation. The variety of elements present, and their extensive processing by hominids, indicates that FLK 22 functioned as a central place/refuge where hominids could transport a variety of carcass parts and process them in an unhurried fashion. The presence of numerous small and medium sized individuals also indicates that hominids could have passively scavenged carcasses from a number of different sources including lions, leopards, sabertooth cats, and mass drownings.     

Clinical study on the cell kinetics of gastric cancer using bromodeoxyuridine labeling index--its relations with DNA ploidy pattern and epidermal growth factor

The prime objective of dental care is maintaining a natural functional dentition for life. It is expected that a growing group of adults will keep their dentition into old age. Although routine prosthodontic care will still be important in the future the treatment strategy for older adults and elderly people with a reduced dentition does require a different approach. The traditional approach in prosthetic therapy was guided primarily by morphological criteria aimed at preservation of complete dental arches, which resulted in emphasis on quantity in dental care. Nowadays requirements such as aesthetics and functional comfort are considered more important and more easily achieved. In the presented principles for treatment planning the importance of a thorough preliminary treatment is stressed. Furthermore, needs for tooth replacement are discussed and guidelines are given for a preventive prosthodontic treatment approach in severely broken-down dentitions and edentulous patients.     

Turbulent flow field over fluvial obstacle marks generated in a laboratory flume

The study is aimed at investigating the mean flow and turbulence characteristics in scour geometry developed near a circular cylinder of length 10cm placed over the sand bed transverse to the flow. The obstacle placed on a sand bed, on the way of a unidirectional flow, develops a crescent-shaped scour mark on the bed. The scour is caused by generation of vortex developed on the upstream side of the obstacle. Sand grains eroded by this vortex, are deposited on the downstream side of the obstacle as wakes. The turbulent flow field within the scour mark was measured in a laboratory flume using an Acoustic Doppler Velocimeter (ADV). The scour marks named as current crescents preserved in geological record are traditionally used as indicators of palaeocurrent direction. The distribution of mean velocity components, turbulent intensities and Reynolds stresses at different positions of the mark are presented. The experimental evidence also shows that the geometric characteristics of the scour mark (width) depend primarily on the cylinder aspect ratio, cylinder Reynolds number and sediment Froude number.     

The role of forensic dentistry in South Africa

Forensic dentistry has become an integral part of forensic medicine over the past 100 years. This has been due to the dedication of people like Amoedo, Gustafson, Sognaes, Keiser-Nielsen and Suzuki, to name but a few. They established the essential role which forensic dentistry plays mainly in the identification of human remains. Dental hard tissues are extremely resistant to fire and are usually the only remains after an extended period of burial. If antemortem dental records are available for an individual then dental identification is as certain as those of fingerprints. In South Africa forensic dentistry had its beginning in 1969 during the Windhoek air disaster. Since then there have been several cases of interest throughout the country, one of which was the crash of the Helderberg off the coast of Mauritius. Other aspects of forensic dentistry are the examination of bite marks and the recognition of facial trauma especially in cases of child abuse; the determination of age, sex and race of skeletal remains; dental ethics and jurisprudence as well as malpractice also form part of the duties of the forensic dentist. The five dental schools in South Africa each have a forensic team which is consulted on a regular basis by forensic pathologists and district surgeons. Forensic dentists are active members of the medicolegal team and should be consulted on a regular basis especially in cases where identification is concerned.     

连铸坯表面振痕的形成及影响因素

综述了连铸过程中铸坯表面振痕形成机理的研究状况,论述了振痕形成机理的主要模型,讨论了振痕间距和振痕深度互相的影响关系,分析了振痕深度和振痕间距各自的影响因素。研究结果表明：可以通过改变连铸过程中的工艺参数以及采用电磁软接触连铸技术来减轻振痕,从而控制铸坯表面质量。     

Relationship between morphologic malocclusion and temporomandibular disorders in orthodontic patients prior to treatment

The purpose of this study was to investigate the role of malocclusion in temporomandibular disorders (TMD) in an orthodontic patient population prior to treatment. The subjects were 508 Chinese patients (214 males, 294 females), 6 to 56 years of age. The type of malocclusion was diagnosed using dental casts, and TMD signs were recorded by clinical examination. The overall prevalence of TMD signs in the whole group was 26.6%. The frequencies of TMD signs were 44.0% for edge-to-edge bite, 31.2% for posterior crossbite, 27.6% for deep bite, 26.5% for excessive overjet, 26.5% for crowding, 23.7% for anterior crossbite and 23.6% for open bite. Although patients with edge-to-edge bite or posterior crossbite had TMD signs more often than the others in the whole group, the differences did not reach statistical significance. We did not find a significant relationship between morphologic malocclusion and TMD.     

Effect of reference marks on the detection of signals on a clock face.

42 female Ss were employed in each of 3 studies undertaken to determine the effect of white marks on a black clock face on the detection of signals, consisting of brief pauses of the clock hand. The signals were presented at intervals ranging from 5-14 sec.; 0-30 marks were used. The addition of 1 mark reduced the percentage of missed signals to half that of the blank face (p     

A mold simulator for continuous casting of steel: Part II. The formation of oscillation marks during the continuous casting of low carbon steel

The restrictions on quality for low carbon continuously cast slab products require that surface defects be kept to a minimum. Currently, the steel industry has developed a wealth of experience on how to apply slabs with oscillation marks to very demanding applications. However, these practices circumvent the problem, rather than solving it. By understanding the formation mechanism of oscillation marks, one can then develop casting practices that can minimize their effect on slab surface quality. The techniques developed in this study allowed a more detailed examination of the mold heat-transfer interactions during continuous casting, such that the variations of heat flux due to irregular solidification near the meniscus could be measured. It is shown that the mechanisms proposed in the literature are not individually sufficient for the formation of an oscillation mark, but that several are necessary and must occur in sequence for an oscillation mark to form. A mechanism is proposed for the formation of oscillation marks that is shown to be in agreement with the trends observed and reported in the literature. Additionally, it is shown that the success of practices used in industry to reduce the severity of oscillation marks can be explained using this proposed hypothesis.     

Changes in the dental arches and dentition between 25 and 45 years of age

The purpose of this longitudinal investigation was to study changes in the dental arches and dentition that occur in midadulthood in an untreated, normal sample. The subjects had Class I molar and canine relationships with less than 4.0 mm of overjet and less than 50% overbite. None had undergone previous orthodontic treatment. Evaluations and measurements were made from dental casts and periapical radiographic surveys of 15 females and 15 males from approximately 25 years to 46 years. The findings indicate that over the span of the study, significant changes occur in the maxillary and mandibular dental arches and dentition in both males and females, including a clinically significant increase in tooth size-arch length (circumference) discrepancy. These changes should be considered part of the normal maturational process and should be taken into consideration when planning treatment and retention options for adolescent and adult patients.