Biomedical subjects

J A Kieser

Publications and source records attributed to J A Kieser.

At least 19 recordsLinked to original sources

PubMed2006

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.

Adult↗

PubMed2006

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).

Dental Materials↗

PubMed2006

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.

Adaptation, Biological↗

PubMed2005

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.

Animals↗

PubMed2005

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.

Bites, Human↗

PubMed2005

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.

Adolescent↗

PubMed2005

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.

Adult↗

PubMed2004

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.

Animals↗

PubMed2004

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.

Aged↗

PubMed2004

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.

Forensic Ballistics↗

PubMed2003

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.

Accidental Falls↗

PubMed2003

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.

Bacterial Typing Techniques↗

PubMed2002

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.

Beverages↗

PubMed2002

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.

Bayes Theorem↗

PubMed2001

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.

Age Distribution↗

PubMed2001

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.

Adult↗

PubMed2000

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.

Anatomy↗

PubMed1999

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.

Adolescent↗