Intraoral pH and temperature during sleep with and without mouth breathing

To measure and compare the intraoral pH and temperature of individuals during sleep with and without mouth breathing. Ten healthy participants [mean age = 25·8 (± 4·3)] wore a custom-made appliance fitted with a pH probe and thermocouple for two sets of 48 h. Continuous pH and temperature measurements were taken from the palatal aspect of the upper central incisors. To simulate mouth breathing during sleep, participants wore a nose clip for two nights of the four, with the first group (n = 5) wearing the nose clip during the first night and the rest (n = 5) wearing the nose clip during the second night of sleep to balance any potential bias from the wearing sequence. Both qualitative and quantitative analyses were conducted. The mean intraoral pH during daytime was 7·3 (± 0·4) and during sleep was 7·0 (± 0·5). The mean intraoral pH during sleep with mouth breathing was 6·6 (± 0·5), which was statistically significant compared with the normal sleep condition (P < 0·01). The intraoral pH decreased slowly over the hours of sleep in all participants. When sleeping with forced mouth breathing, intraoral pH showed a greater fall over a longer period of time. The mean intraoral temperature was 33·1 °C (± 5·2) during daytime and 33·3 °C (± 6·1) during sleep, with no statistical significance between sleep with and without mouth breathing (P > 0·05). The results suggest that mouth breathing during sleep is related to a decrease in intraoral pH compared with normal breathing during sleep, and this has been proposed as a causal factor for dental erosion and caries.

Simulating backspatter of blood from cranial gunshot wounds using pig models

Few studies have examined the biomechanical basis for backspatter from cranial gunshot wounds. Backspatter is material which travels against the direction of fire following ejection from a gunshot entrance wound. Our paper focuses on the use of animals for reconstructing this phenomenon. Five live pigs and several slaughtered pigs were shot using either 9 × 19 mm, 115 grain, full metal jacketed ammunition or .22 long rifle, 40 grain, lead, round-nose ammunition. A high-speed camera was used to record the entrance wound formation and backspatter. A small amount of backspattered material was produced with all targets, and blood backspatter was seen in a few cases. However, we conclude that our model provides an understanding of the phenomenon of backspatter and the physical mechanisms associated with it. The various components of the mechanism of backspatter formation are complex and overlap. The principle mechanism observed in pig cranial gunshots was the high-speed impact response of the skin overlying the skull bone. This study has also produced evidence supporting the view that backspatter can result from the splashing of superficial blood if it is already present on the skin. Subcutaneous gas effects have been demonstrated for backspatter from contact shots. There has been no clear evidence of the role of the collapse of a temporary cavity within the brain.

Factors associated with pain induced by orthodontic separators

Pain resulting from the application of orthodontic forces varies markedly across individuals. The reasons of this variability are still largely unknown. To investigate factors that may be associated with orthodontic pain following the application of orthodontic separators. One hundred and seven participants were screened for pain response over 48 h following placement of orthodontic elastomeric separators. The highest (n = 10) and lowest (n = 10) pain responders were identified, and data collected on tooth pain sensitivity to electrical stimulation in conjunction with using the Pain Catastrophising Scale (PCS), Dental Anxiety Scale (DAS) and cold pressor test (CPT). There were statistically significant differences between high- and low-pain responders in catastrophising score (P ≤ 0.023). For every PCS magnification score of 1 unit higher, the relative risk of being a high-pain responder was 1.6 (P = 0.002); those scoring higher on helplessness had a lower risk of being so. DAS scores of high-pain responders were twice as high as those of low-pain responder (P = 0.043). During the first 2 min of CPT, the high-pain responders experienced more pain than the low-pain responders (P ≤ 0.029). Tooth pain thresholds did not differ between the two different pain responder groups. Pain catastrophising, dental anxiety and cold sensitivity appear to modify the pain experienced following placement of orthodontic separators. Further research is needed to determine the validity of screening questions to identify at-risk patients prior to commencing orthodontic treatment.

Patterns and trends in facial fractures in New Zealand between 1999 and 2009

OBJECTIVES

To describe patterns and trends in facial fractures in New Zealand over a decade.

METHOD

A secondary analysis of Ministry of Health data on facial fractures occurring between 30 June 1999 and 1 July 2009. Patient demographic characteristics and the details of injury were analysed and described.

RESULTS

Over the study period, the incidence of injury was constant. A total of 26,637 facial fractures were recorded. Most (79%) occurred in males, giving a male-to-female ratio of 4:1. Peak injury rates for both males and females, coincide with the legal alcohol purchasing age. Interpersonal violence (IPV) was the leading cause of facial fractures, accounting for 38%; it increased steadily each year. The number of fractures attributed to sports/other, and road traffic accidents (RTA) had fallen. Māori still continue to experience a disproportionate rate of facial fractures, twice that of the NZ European population.

CONCLUSIONS

Interpersonal violence is an increasing problem in NZ and contributes to a greater number of facial fractures each year. More measures are required to reduce the number of IPV-related injuries. Perhaps the most effective would be to return the legal alcohol purchasing age to 20 years. More is also required to reduce facial fractures in the high-risk injury groups of young adults, males, and Māori.

The role of oral soft tissues in swallowing function: what can tongue pressure tell us?

Tongue pressure data taken from healthy subjects during normal oral activities such as mastication, speech and swallowing are providing us with new ways of understanding the role of the tongue in craniofacial growth and function. It has long been recognized that the sequential contact between the tongue and the palate plays a crucial role in the oropharyngeal phase of swallowing. However, because the focus of most research on intraoral pressure has been on the generation of positive pressure by the tongue on the hard palate and teeth, generation and coordination of absolute intraoral pressures and regional pressure gradients has remained unexplored. Ongoing research in our laboratory has uncovered highly variable individual pressure patterns during swallowing, which can nonetheless be divided into four stages: preparatory, primary propulsive, intermediate and terminal. These stages may further be sub-classified according to pressure patterns generated at the individual level as tipper or dipper patterns in the preparatory stage, roller or slapper in the primary propulsive and monophasic or biphasic during the intermediate stage. Interestingly, while an increase in bolus viscosity can result in significant changes to pressure patterns in some individuals, it has little effect in others. Highly individual responses to increased viscosity are also observed with swallowing duration. The above, together with other findings, have important implications for our understanding of the aetiology of widely differing conditions such as protrusive and retrusive malocclusions, dysphagia and sleep apnoea, as well as the development of novel food products.

Structure and compositional characteristics of caniniform dental enamel in the tuatara Sphenodon punctatus (Lepidosauria: Rhynchocephalia)

OBJECTIVE

The evolution of dental tissues in relation to tooth function is poorly understood in non-mammalian vertebrates. We studied the dentition of Sphenodon punctatus, the sole remaining member of the order Rhynchocephalia in this light.

METHODS

We examined 6 anterior maxillary caniniform teeth from adult Sphenodon by scanning electron microscopy, nano-indentation and Raman spectroscopy.

RESULTS

The elastic modulus (E) for tuatara enamel was 73.17 (sd, 3.25) GPa and 19.52 +/- 0.76 Gpa for dentine. Hardness (H) values for enamel and dentine were 4.00 (sd, 0.22) and 0.63 +/- 0.02 Gpa respectively. The enamel was thin (100 gm or less), prismless and consisted of grouped parallel crystallites. Incremental lines occurred at intervals of about 0.5 to 1 rm. There were tubular structures along the enamel dentine junction running from the dentine into the inner enamel, at different angles. These were widened at their base with a smooth, possibly inorganic lining. Enamel elastic modulus and hardness were lower than those for mammals.

CONCLUSIONS

The presence of enamel tubules in the basal part of the enamel along the EDJ remains speculative, with possible functions being added enamel/dentinal adhesion or a role in mechanosensation.

Biomechanical approach to human bitemark reconstruction

This paper investigates the changes in upper and lower dental bite records that occur when the anterior teeth occlude into a three-dimensional rather than a flat object.

METHODS

anterior bite registrations were obtained from 20 volunteers with full and unrestored dentitions. As a three- dimensional, life-like bite target we cast a silicone replica from the impression of an actual arm, fitted with a rigid bony interior. Each participant was asked to bite into a single layer of softened bite registration wax wrapped around the same location on the fake arm, as well as into a flat wafer of the same material. Upper and lower bite registrations were then scanned in the same location on a flat bed scanner. We analysed the sizes of the different bite marks by means of landmark- and semi-landmark analysis to calculate Procrustes distances between tooth outlines. In order to analyse shape variation between the two types of bite registration we carried out principal components analyses on the partial warp scores. These were derived from partial Procrustes coordinates aligned by means of thin-plate spline decomposition based on a bending energy matrix. Our results show that there are significant differences in the shape of the upper or lower teeth when they occlude into a flat or three- dimensional target. We conclude that the use of a traditional flat bite registration in human bitemark reconstruction and analysis has to be seriously questioned.

Restoration of non-carious cervical lesionsPart II. Restorative material selection to minimise fracture

OBJECTIVE

It is still largely unknown as to what material parameter requirements would be most suitable to minimise the fracture and maximising the retention rate of the restoration of cervical non-carious lesions (NCCL). The present paper, as a first of its kind, proposes a radical approach to address the problems of material improvement, namely: numerical-based, fracture and damage mechanics materials optimisation engineering. It investigates the influence of the elastic modulus (E) on the failure of cervical restorative materials and aims to identify an E value that will minimise mechanical failure under clinically realistic loading conditions.

METHOD

The present work relies on the principle that a more flexible restorative material would partially buffer the local stress concentration. We employ a "most favourable" parametric analysis of the restorative's elastic modulus using a fracture mechanics model embedded into finite element method. The advanced numerical modelling adopts a Rankine and rotating crack material fracture model coupled to a non-linear analysis in an explicit finite element framework.

RESULTS

The present study shows that the restorative materials currently used in non-carious cervical lesions are largely unsuitable in terms of resistance to fracture of the restoration and we suggest that the elastic modulus of such a material should be in the range of 1GPa. We anticipate that the presented methodology would provide more informative guidelines for the development of dental restorative materials, which could be tailored to specific clinical applications cognisant of the underlying mechanical environment.

Mandibular biomechanics and development of the human chin

The development of the chin, a feature unique to humans, suggests a close functional linkage between jaw biomechanics and symphyseal architecture. The present study tests the hypothesis that the presence of a chin changes strain patterns in the loaded mandible. Using an anatomically correct 3-D model of a dentate mandible derived from a CT scan image, we analyzed strain patterns during incisal and molar biting. We then constructed a second mandible, without a chin, by 'defeaturing' the first model. Strain patterns of the second model were then compared and contrasted to the first. Our main finding was that chinned and non-chinned mandibles follow closely concordant patterns of strain distribution. The results suggest that the development of the human chin is unrelated to the demands placed on the mandible during function.

Mechanical evaluation of cervical glass-ionomer restorations: 3D finite element study

OBJECTIVES

The aim of this paper was to investigate the influence of lesion shape and depth as well as the direction of occlusal loading on the mechanical response of cervical GIC restorations.

METHODS

A finite element model of a lower first premolar was created. Both wedged and rounded lesions were then modelled with incremental depth after which the tooth was loaded at different angles. First principal stress (tension) was employed as an indicator of material failure, by contrasting our calculated stresses with the ultimate tensile strength of the GIC and known values of bond strength between material and tooth substrate.

RESULTS

Obliquely loaded teeth exhibited significantly higher tensile stress in the cervical region of the restoration. For forces inclined at angles of 30 degrees and higher to the vertical tooth axis, the tensile stresses in the cervical margin of the restoration exceeded the ultimate material and bond strength. In contrast, lesion shape and depth have only a minor influence on tensile stress development.

CONCLUSIONS

Lesion depth and shape are not of primary concern from a mechanical perspective for a restorative treatment decision. By contrast, occlusal diagnosis and subsequent re-adjustments of tooth contacts do form a critical part of the treatment of non-carious cervical lesions (NCCLs).

Functional significance of strain distribution in the human mandible under masticatory load: numerical predictions

A common feature of studies of mandibular morphology is the assumption that there is some functional relation between the form of the lower jaw and masticatory stress. It was noted that the local variation in cortical bone thickness in the mandibular corpus appears to be stereotypical among anthropoids. This occurs at sections under the molars, where the lingual cortical plate is thinner than buccal one. In this study we investigate and contrast the strain pattern along buccal and lingual surfaces of the mandibular corpus during mastication using a numerical model of a human mandible. We show that strain distribution differs in alveolar and mid-corpus segments of the mandible and that the latter develops an alternate pattern between the buccal and lingual aspects of the working and balancing sides of the jaw. We then relate the magnitude of these strains to Frost's mechanostat. Our results suggest that the cortical asymmetry of the human mandible is in fact not related to strain patterns generated during mastication.

Genotypic comparison of bacteria recovered from human bite marks and teeth using arbitrarily primed PCR

AIMS

This study assessed, for forensic purposes, the feasibility of genotypically matching oral streptococci recovered from recent human bite marks with those from the teeth of the biter.

METHODS AND RESULTS

Streptococci were isolated from the incisors of eight volunteers. Arbitrarily primed PCR (AP-PCR) distinguished 106 streptococcal genotypes among the participants, each harbouring at least eight distinct strains. In a crime simulation, a sample from an experimental bite mark was analysed by an experimenter unaware of its origin. The bacteria were unambiguously matched to the biter by comparing the amplicon profiles with those from the eight participants. In contrast, bacteria from an additional bite mark (not generated by one of the original participants) could not be matched to any of the eight participants. Between 20 and 78% of catalogued bacterial genotypes were recovered 12 months later from each participant. Throughout the study period, none of the bacterial genotypes were shared between participants.

CONCLUSIONS

Streptococci isolated from recent bite marks can be catalogued by AP-PCR and matched to the teeth responsible for the bite.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study provides 'proof of concept' that genotypic analysis of streptococci from bite marks may provide valuable forensic evidence in situations where the perpetrator's DNA cannot be recovered.

Unusual fatal dog attack in Dunedin, New Zealand

A case of a fatal dog attack on a middle aged woman is presented. The offending dog was her own Bull-mastiff, which had previously shown signs of aggression towards her. Most of the injuries were found on the victim's face, neck and skull. A noteworthy feature of this attack was that the victim was known to suffer from Huntington disease. It is postulated that the involuntary movements, progressive dementia and increased moodiness characteristic of the disease may have had a significant role in triggering the attack.

Oral piercing and oral trauma in a New Zealand sample

This study investigated the periodontal and dental trauma resultant from tongue and lip piercings in a convenience sample of 43 adult dental patients. Patients underwent an intra-oral examination followed by the administration of a questionnaire. Each patient was examined for lingual or buccal recession of the upper and lower incisors as well as the extent of abnormal toothwear or trauma on these teeth. Following bivariate analyses, regression analyses were conducted to test the study hypotheses and derive adjusted estimates for the dependent variables. Of the 43 individuals who participated (93.0% females; mean age 21 years; age range 14-34 years) 76.7% had a tongue piercing, 34.9% had a lip piercing, and 11.6% had both. Only four had had their piercing procedure provided by a doctor or dentist. Postpiercing complications were reported by 34.9%. Most of those with a labial piercing (80.0%) had 1+ labial site with gingival recession (GR), and almost one-third of those with a tongue piercing had at least one lingual site with GR. Age was a significant predictor of the prevalence of lingual recession, with the odds of having lingual recession increasing by 1.17 (95% CI 1.01, 1.35) for every year older than 14. Age was the only significant predictor of the number of lingual sites with recession, but was not a predictor of the prevalence of labial recession or the number of affected sites. There were no significant associations between piercings and abnormal toothwear or trauma. These findings suggest that oral piercings are associated with localized gingival recession, and that the providers of such procedures should ensure that, as part of the informed consent process, prospective patients are informed of the likelihood that their periodontal health may be compromised.

Mandibular stiffness in humans: numerical predictions

The chin is a feature unique to humans. This study evaluates the effect of mandibular symphyseal design on biomechanical masticatory effectiveness as determined by structural stiffness and stress developed under flexural and torsional loading. A simple model of three symphyseal shapes (chin, flat symphysis and lingual buttress), was built to represent human, Neanderthal and higher primate symphyses and these were subjected to wishboning and torsional forces. Additionally, an anatomically detailed reconstruction was made of the CT scan of an actual human mandible, which was then also morphed into a chinless model. The results of a 3-D finite element analysis show firstly, that none of the three different symphyseal shapes is biomechanically more advantageous than the others for the given loading condition. Secondly, we show in a CT-derived model, that the presence of a chin does not confer significantly improved stiffness to torsional or flexural loading. These results indicate that the acquisition of a chin in modern humans is not related to the functional demands placed upon the mandible during mastication, but suggest that it may have developed in response to other biomechanical demands.

Intrabony course of the inferior alveolar nerve in the edentulous mandible

The purpose of this study was to investigate the vertical positioning and intrabony branching patterns of the inferior alveolar nerve (IAN) in 39 edentulous human cadaveric mandibles by buccal microdissection. Dissected mandibles were classified on the basis of the height of the IAN within the body of the mandible and the branching pattern of the IAN. The IAN was located in the superior part of the body of the mandible in 30.7% (12/39) of cases, all of which showed a small posterior molar plexus of branches. In 69.2% (27/39) of cases the IAN was half-way or closer to the inferior border of the mandible. Of these latter cases, 41% demonstrated a small, posterior molar plexus of branches, 37% showed posterior and anterior plexuses, and 22% showed either no branches or a single trunk with a small number of single branches directed at the superior border of the mandible. These findings were rendered in 3D computer format for instructional purposes.

Replication of cranial gunshot wounds

It is possible to differentiate between entrance and exit wounds in bone by examining the specimen concerned. Because of the evidential usefulness of providing jurists or members of a jury with such specimens, we describe an easy and reliable method for replicating gunshot wounds in the human skull utilizing dental materials and methods.

Post mortem cohabitation-shell growth as a measure of elapsed time: a case report

A partial calvaria, dredged from the sea-bed some years previously, was referred to us for examination. The presence of a well-established mollusc colony on the vault allowed us to establish a minimum elapsed time since death. Such a cross-disciplinary co-operative study is of great advantage in expediting a satisfactory conclusion.

Isolation and genotypic comparison of oral streptococci from experimental bitemarks

The feasibility of recovering and genotypically comparing oral bacteria from bitemarks for forensic purposes was assessed experimentally. Volunteers firmly bit their own upper arms and bitemarks were sampled at intervals to recover viable Streptococcus isolates. The recoverability of bacteria decreased over time but an average of more than one thousand viable organisms was recovered 24 hrs after biting, provided the site remained relatively undisturbed. Physical exertion, manual rubbing and application of moisturizing lotion all decreased bacterial recoverability compared to controls. Streptococci could also be recovered from bites inflicted on various fabrics. Genomic profiles (DNA "fingerprints") of bacteria recovered from bitemarks could be identified exclusively with those from the teeth of the individual responsible. These findings suggest that a bacterial genotyping approach to bitemark analysis could have forensic application in situations where the perpetrator's DNA cannot be recovered from an oral contact site.

Dental and maxillofacial injuries among older New Zealanders during the 1990s

Not only is the number of older people increasing in New Zealand, but a greater number of them are keeping their own teeth, with predictable consequences for the costs of treating (and rehabilitating) dental and maxillofacial trauma in that group. The aim of the study was to describe the occurrence of dental and maxillofacial trauma involving New Zealanders aged 65 and over during the 1990s. The investigation was a secondary analysis of routinely collected, national-level compensation and hospital treatment data. The analysis showed that: (1) there was an increase in the rate and absolute number of injuries among older people; (2) the dental trauma rate was highest among males in the youngest age group, while the facial fracture rate was highest among older females; and (3) there was a general increase in the contribution of falls to the occurrence of trauma. Measures which aim to reduce the occurrence of falls among older people will also reduce the oral and maxillofacial trauma rate in that age group.

Weighing evidence: quantitative measures of the importance of bitemark evidence

Quantitative measures of the importance of evidence such as the "likelihood ratio" have become increasingly popular in the courtroom. These measures have been used by expert witnesses formally to describe their certainty about a piece of evidence. These measures are commonly interpreted as the amount by which the evidence should revise the opinion of guilt, and thereby summarize the importance of a particular piece of evidence. Unlike DNA evidence, quantitative measures have not been widely used by forensic dentists to describe their certainty when testifying about bitemark evidence. There is, however, no inherent reason why they should not be used to evaluate bitemarks. The purpose of this paper is to describe the likelihood ratio as it might be applied to bitemark evidence. We use a simple bitemark example to define the likelihood ratio, its application, and interpretation. In particular we describe how the jury interprets the likelihood ratio from a Bayesian perspective when evaluating the impact of the evidence on the odds that the accused is guilty. We describe how the dentist would calculate the likelihood ratio based on frequentist interpretations. We also illustrate some of the limitations of the likelihood ratio, and show how those limitations apply to bitemark evidence. We conclude that the quality of bitemark evidence cannot be adequately summarized by the likelihood ratio, and argue that its application in this setting may be more misleading than helpful.

Risk indicators for tooth wear in New Zealand school children

AIM

To investigate the prevalence and severity of tooth wear in the primary dentition of a representative sample of New Zealand school children and relate these to possible risk factors.

DESIGN

A cross-sectional study.

SETTING

Primary schools in Dunedin, New Zealand.

PARTICIPANTS

104 children of both sexes, aged between 5 and 8 years, randomly selected.

METHODS

Clinical examinations of the buccal, occlusal/incisal and lingual surfaces of deciduous canines and molars.

MAIN OUTCOME MEASURE

Degree of wear and the presence of dentinal cupping of teeth. Information on weaning and consumption of fruit-based drinks at bed time, frequency of consumption of fruits, yoghurt, pickled foods, fizzy and fruit-based drinks.

RESULTS

The prevalence of tooth wear was similar in boys and girls and there were no significant differences between sides of the arches. A high percentage (82%) of children had at least one primary tooth with dentine exposed. While maxillary canines showed the greatest prevalence of dentine exposed, maxillary molars displayed the greatest prevalence of cupping. Severe tooth wear was less prevalent among children weaned after 12 months (14.3%) than those weaned earlier (27.9% P < 0.01). There were no statistically significant associations between wear and the consumption of fruit, yoghurt, pickled foods, fizzy drinks or fruit-based drinks.

CONCLUSIONS

Tooth wear associated with dentine exposure is common in 5-8 year old children. This is not significantly associated with dietary factors, but appears to be related to early weaning from the breast.

Dental misidentification on the basis of presumed unique features

Positive identification of skeletal remains by dental comparison depends on the demonstrable concordance between postmortem and antemortem records. However, there is no accepted norm for the number of points of concordance and there are circumstances when a single (or a few) unique features may allow positive identification. We present a recent case in which superficial similarity may have led to misidentification. We argue that misidentification is particularly likely with over-reliance on apparently unique features. The fact that a single inexplicable inconsistency will rule out a positive dental identification is highlighted.

Bite injuries: pathophysiology, forensic analysis, and management

Bites are serious injuries that constitute 1 percent of all emergency-department visits in the United States of America. Human bite injuries may lead to loss of function, infection, and gross disfigurement, and often are associated with interpersonal and sexual violence, and child abuse. Issues with infection from oral contaminants, tissue damage, and difficult surgical reconstruction make the management of human bite injuries a challenge. The unique nature of teeth and the bite marks they produce are invaluable in forensic pathology. A systematic and detailed evaluation of bite injuries should be performed by a forensic odontologist in order to provide the necessary information for forensic purposes. Management of human bite injuries includes wound debridement, surgery to repair or replace damaged tissue, and long-term antibiotic therapy.

Anatomical knowledge and clinical evaluation of the muscles of mastication

In this survey, we identify the positive role that an instructional anatomy course has prior to a workshop on temporomandibular dysfunction. Not only did it result in enhanced clinical evaluation of the muscles of mastication acquired by the participants, but it also approximated the skills of dental and medical practitioners.

Odontological identification in two high-impact, high-temperature accidents

Here we report on two high-impact accidents both of which were complicated by fire. The first accident involved a light aircraft which crashed in a gorge while performing a low, slow flight. Both victims were found to have experienced extensive dental fracturing. The second accident was a high speed motor vehicle crash followed by incineration which left the two victims without dental fracturing. In the absence of comparative data on the effect of burning on teeth the cause of the foregoing remains unanswered.

Root canal anatomy of anterior and premolar teeth in Down's syndrome

AIM

The aim of this study was to examine tooth length and root canal anatomy of 281 anterior and premolar teeth from 66 DS individuals using a standard protocol.

RESULTS

The results indicated that root canals in DS are relatively simple and that there is a significant reduction in root and crown length.

CONCLUSIONS

We propose that these observations are commensurate with the suggestion that trisomy 21 exerts its effect by slowing the mitotic cycle and rate of cell proliferation, resulting in generalized retardation of growth.

Relationship between juvenile bruxing and craniomandibular dysfunction

A longitudinal study was conducted over 5 years to investigate the relationship between juvenile bruxing and craniomandibular disorders. A total of 150 bruxers between the ages of 6 and 9 years were examined for oral parafunctions and TMJ symptoms. Of these, 126 were re-examined for the same signs and symptoms after 5 years. The results showed that only 17 individuals had retained their bruxing habit. In common with other studies, we found that symptoms reduced with age. It was concluded that juvenile bruxing was a self-limiting condition which does not progress to adult bruxism and which appeared to be unrelated to TMJ symptoms.

Basicranial flexion, facial reduction and temporomandibular joint dysfunction

Although dysfunction is the major condition affecting the bilateral temporomandibular joint (TMJ), it has defied previous attempts to explain, predict, or prevent its clinical manifestations. A hypothesis is developed that there is an anatomical predisposition to TMJ dysfunction which should be sought in the phylogenetic flexing of the hominid basicranium. It is argued that the glenoid fossa, caught between an ever-increasing brain size and more ventrally oriented facial apparatus, has become deepened and hence labile to dysfunction.

Dental asymmetry, maternal obesity, and smoking

This study examines the levels of fluctuating dental asymmetry in four samples of school children: those whose mothers were obese and had smoked during the pregnancy concerned (n = 111); those whose mothers were obese non-smokers (n = 114); those whose mothers were non-obese smokers (n = 104); and those whose mothers were lean non-smokers (n = 111). The degree of fluctuating asymmetry was assessed by means of a rescaled asymmetry measure. Obesity was defined as Quetelet's index in excess of 30, and smoking status as at least 20 cigarettes per day during the pregnancy concerned. When the magnitudes of fluctuating asymmetry in children of lean smokers were compared to the control group of lean non-smokers, no significant univariate differences were found. Children of obese mothers, whether these smoked or not, were found to have significantly raised levels of asymmetry. An analysis of variance confirmed that the combination of obesity and maternal smoking was a significant predictor of fluctuating dental asymmetry. The teeth involved tended to be the maxillary first incisor and molars. It is concluded that maternal obesity has a destabilizing effect on the developing fetus and that this effect appears to be enhanced in obese mothers who smoked. This effect was absent in lean mothers, irrespective of their smoking status.

Delayed tooth formation in children exposed to tobacco smoke

Panoramic radiographs of 203 Caucasoid children between the ages of seven and ten years were examined for an evaluation of dental development. Four groups were studied: a control group in which neither parent had smoked during the pregnancy concerned, a group exposed to tobacco smoke from the mother only, a group exposed to smoke from the father only, and finally a group exposed to tobacco smoke from both parents. In each case, the dental age (determined according to the method of Moorrees) was contrasted to the chronological age of the subject. Overall results showed that there were no differences in dental ages related to gender. Maximum differences between chronological and dental ages were found in children subjected to cigarette smoke from both parents. Here, a 35% reduction in dental maturation was noted. Most affected teeth were the maxillary second premolars, while the central incisors were the least affected.

Inequalities in the pattern of dental delivery in South Africa

The pattern of dental delivery of three groups of private general practitioners were evaluated. The first group consisted of dentists who charged fees based on the National Schedule of the Dental Association of South Africa, the second charged fees at the recommended Scale of Benefit and served an urban population, while the last group served township dwellers at the Scale of Benefits. In each case, sequential claims of 500 medical scheme members were evaluated for ten randomly selected dentists within each group. Uni- and multivariate analyses revealed significant differences between these groups which centred on the use of cast restorations, bleaching of vital teeth and treatment of diseases of the oral mucosa. Because these differences do not conform to documented differences in dental needs between the two groups, it is concluded that other non-clinical factors influence the delivery of private dentistry.

Effects of prenatal exposure to tobacco smoke on developmental stability in children

The effects of maternal and paternal smoking on fetal and neonatal dental development were investigated in a sample of 199 school children. Fluctuating asymmetry was evaluated in the maxillary arcades of four groups of children: those whose mothers had smoked, those whose fathers had smoked, those whose parents both had smoked, and finally, those whose parents had not smoked. When the magnitudes of fluctuating asymmetry in children exposed to parental tobacco smoke from one parent only were compared with the control group, no general univariate differences were found. Children exposed to smoke from both parents, however, showed significantly elevated levels of asymmetry in four out of six comparisons. In contrast, an analysis of variance failed to find significant differences on the basis of sex, parity, smoking status, or their interactions. It is concluded that parental smoking does not result in developmental destabilization of the fetus and neonate.

Heterodonty and patterns of tooth replacement in Crocodylus niloticus

Patterns of tooth replacement in the Nile crocodile Crocodylus niloticus were evaluated in the lateral radiographs of six dried skulls of 1-year-old individuals. Additionally, the ontogeny of the succession of teeth in this species was investigated in four embryos and a hatchling, which were serially sectioned. Three-dimensional, computer-generated reconstructions of these individuals suggested that there was a regular pattern of odontogenic progression. Three morphogenetic zones could be identified in each of the age classes: an incisor, a canine, and a molar region. It was thus concluded that the Nile crocodile is hetero- rather than homodont. Zahnreihen, or tooth rows, with a periodicity of one were easily identified. © 1993 Wiley-Liss, Inc.

Sex allocation of skeletal material by analysis of the proximal tibia

In this study we contrasted the confidence with which individuals may be grouped and then reallocated on the basis of a set of measurements from the proximal tibia. The data were derived from 100 Caucasoid (50 male) and 102 Negro (50 male) tibia housed in the R.A. Dart Collection. Multivariate discrimination was effected by means of canonical and stepwise discriminant analyses, whilst probabalistic models were used to allocate individuals. High levels of correct classification (84.62-92%) were matched by high levels of reallocation, suggesting that, in contrast to dental or craniobasal measurements, those of the proximal tibia may be usefully employed to allocate an individual on the basis of sex.

Fluctuating odontometric asymmetry and maternal alcohol consumption

Fluctuating asymmetry was evaluated in the dental arcades of 112 children (60 male, 52 female) of alcoholic mothers. Only individuals who showed no signs of the fetal alcohol syndrome were included. When these results were compared with those of a control group of 120 normal children, the former group was found to be significantly more asymmetric. The present study showed that canines were the least asymmetric whilst lateral incisors showed the greatest levels of asymmetry. It is suggested that the elevated levels of fluctuating odontometric asymmetry in children of alcoholic mothers may be ascribed to prenatal stress, especially during the soft tissue stage of odontogenesis.

High-dimensional plots in the evaluation of interpopulation differences in human tooth size

The use of high-dimensional plots is explored in the evaluation of interpopulation differences in tooth size. Buccolingual and mesiodistal diameters were determined on the teeth of 202 Paraguayan Lengua Indians, 100 skeletal Blacks, 206 living South African Blacks and 125 living South African caucasoids. Multivariate discrimination between the four populations was effected by means of canonical variate analyses and stepwise discriminant analyses. These results were then compared to Andrews plots generated for males and females in each of these populations. Our results show that Blacks and caucasoids have significantly differing curves and that Amerindians share characteristics of both these groups.

Mandibulodental allometry in the African wild dog, Lycaon pictus

Mandibulodental relations were evaluated in a sample of 34 adult Lycaon pictus crania (18 males, 16 females). Standard mesiodistal and buccolingual measurements, together with 8 mandibular measurements (intercondylar distance, intercarnassial breadth, mandibular length, arch length, condylar height, canine-condylar length, mandibular width, mandibular height) were allometrically scaled to total skull length. These results were then compared with those of domestic dogs and of 3 smaller southern African canids, Vulpes chama, Canis adustus and C. mesomelas. The results highlighted the differences in mandibulodental relations between males and females and provided support for the theory that females have relatively larger postcanine tooth sizes to match the higher masticatory demands of lactation and pregnancy. The African wild dog is shown to be more closely related dentally to the domestic dog than has previously been supposed.

Comparative morphology of the mandibulodental complex in wild and domestic canids

The relationships between mandibular and dental measurements were investigated in a sample of 60 adult domestic dogs, 17 black-backed jackals Canis mesomelas, 18 side-striped jackals C. adustus and 16 Cape foxes Vulpes chama. Standard mesiodistal and buccolingual tooth measurements, together with 8 mandibular measurements (intercondylar distance, intercarnassial breadth, mandibular length, arch length, condylar height, canine-condylar length, mandibular width, mandibular height) were scaled allometrically to total skull length. Despite wide differences in diet and sexual dimorphism between the 3 wild canid species, larger canids were found to be scaled up versions of smaller canids. While males showed a highly concordant patterning when compared with domestic dogs of equivalent size, females showed a remarkably mosaic pattern. Relative to skull size, the only teeth that appear to be larger than those of equivalently sized domestic dogs were the second molars. It is suggested that those theories of sexual dimorphism and functional integration which apply to skeletodental dimensions in primates may not be applicable to canids.

The reliability of human odontometric data

The present analysis addressed the reliability of human dental mensuration, with special reference to intra- and inter-observer error, the effect of time and of tooth type. Two observers were asked to measure the same 35 incisors, premolars and molars, using the same mensurational technique and the same instrumentation. Standard mesiodistal (MD) and buccolingual (BL) measurements were repeated on the next day and after six months. Measurement error was evaluated by means of Pearsonian correlation coefficients, mean absolute error, the Bland-Altman procedure, percentage error and an analysis of variance. It was concluded that human dental mensuration is subject to a large error component which is more marked in the MD than in the BL dimension, higher in the anterior than the postcanine teeth and greater between than within observers. These error components were shown to be random rather than systematic.

An allometric perspective on primate postcanine tooth size

The allometric relations of postcanine tooth size were evaluated in a sample of 66 adult Galago crassicaudatus (34 males, 32 females). Postcanine tooth area and length (estimated from mesiodistal and buccolingual measurements of upper and lower cheek teeth) were scaled to 4 cranial measures: bimaxillary width, maxillo-alveolar length, mandibular length and bigonial width. Postcanine tooth size was also scaled to body weight, body length and total skull length. It was found that postcanine surface and length were significantly correlated to the cranial measures employed in females, showing positive allometric scaling. These correlations were, however, lacking in males. In neither sex was postcanine size found to be significantly correlated to body length or weight.