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Biomedical subjects

J Kieser

Publications and source records attributed to J Kieser.

At least 19 recordsLinked to original sources
PubMed2006

Modelling of fracture behaviour in biomaterials.

One of the most frequent causes of degradation and failure of quasi-brittle biomaterials is fracture. Mechanical breakdown, even when not catastrophic, is of particular importance in the area of biomaterials, as there are many clinical situations where it opens the path for biologically mediated failures. Over the past few decades the materials/biomaterials community has developed a number of numerical models, but only with limited incorporation of brittle failure phenomena. This article investigates the ability of a non-linear elastic fracture mechanics (NLEFM) model to reliably predict failure of biomaterials with a specific focus on the clinical settings of restorative dentistry. The approach enables one to predict fracture initiation and propagation in a complex biomechanical status based on the intrinsic material properties of the components. In this paper, we consider five examples illustrating the versatility of the present approach, which range from the failure of natural biomaterials, namely dentine and enamel, to a restored tooth, a three unit all ceramic bridge structure and contact-induced damage in the restorative layered materials systems. It is anticipated that this approach will have ramifications not only to model fracture events but also for the design and optimisation of the mechanical properties of biomaterials for specific clinically determined requirements.

Biocompatible Materials↗
PubMed2005

The influence of context on students' approaches to learning: a case study.

This paper gives an account of a small-scale longitudinal study that examined changes in conceptions and approaches to learning as 14 students experience a problem-based learning (PBL) curriculum for the first time. The course in oral biology aimed to encourage conceptual understanding of the topic and improve student learning through its PBL curriculum and assessment method. Those who entered the course with a surface approach and fragmented conception of learning left with a deep-learning approach, cohesive conception and quality learning outcomes. There were no observable changes in the students who started the course with a deep-learning approach and cohesive conception, except for two who reported surface approaches and fragmented conceptions at the end. These two students also achieved the lowest examination scores. To help explain these findings we examine the wider context for student learning including student motivation.

Attitude↗
PubMed2002

Serious facial fractures in New Zealand from 1979 to 1998.

We present data on the incidence, aetiology, age, sex and ethnic distribution of facial fractures in New Zealand for the 20-year period from 1979-1998. Most facial fractures (78.9%) occurred in males with a rate of 65.5/100,000, person-years compared with 21% in females with an incidence of 17/100,000. While the injury rate peaked in males between the ages of 20-24 years (200/100,000), it peaked between 15-19 years (34.7/100,000) in females. The most common causes of facial fracture in both genders were assault (14/100,000) and being unintentionally struck by an object or person (9.5/100,000) which is consistent with similar data from South Africa and the USA. The rates of fracture in Maori (68.1/100,000) were approximately twice those of Pacific Islanders (37/100,000) or other ethnic groups (34.2/100,000).

Accidents, Traffic↗
PubMed2001

Student learning and the teaching-research nexus in oral biology.

Although frequently coexistent, we know little about the interactions among research, teaching and learning in higher education. This study examines the preferences of second and third year dental students for questions that require a research-based deep approach or questions that require a straightforward didactic approach. A questionnaire was designed to evaluate the opinion of 114 students who took part in the Oral Biology course. 56 second year students (75%) responded while 58 (84%) of third year students responded. Questions that required an interpretive approach were found to be most appealing by 70.2% of all students. Questions which required a regurgitative approach were favoured by 11.6% of students. No significant differences were found when the sample was broken down by country of origin, year of study or gender, suggesting that dental students preferred research-based learning rather than superficial didactic learning.

Attitude↗
PubMed2000

Clinical anxieties among dental students.

We analysed the perceived stresses associated with the transition from preclinical to clinical teaching among dental students at the Faculty of Dentistry, University of Otago. An anxiety questionnaire was completed by 120 students in their Second and Third Years of study. Because of the institution of a new curriculum, these students were uniquely in the same class. The highest levels of anxiety associated with general clinical situations were felt for getting diagnoses wrong, hurting patients, dealing with medical emergencies, and getting infected. In general, there were no significant gender or academic year differences. When faced with specific situations, students were most stressed by the prospect of surgical procedures, temporomandibular joint problems, and failed local analgesia. Significant differences between the two years centred on giving an inferior alveolar nerve block and in dealing with poor oral hygiene, the Second-year students showing the greater anxiety.

Anxiety↗
PubMed1999

Glenomandibular muscle band in the human TMJ: a muscular antagonist to Bennett movement?

The medial aspects of ten adult TMJs were dissected using an inferior, rather than the more traditional lateral approach. Additionally, five 25 mm3 cubes of cadaver tissue with the mandibular condyle at their center were serially cryosected and photographed. Axial MRI scans were also taken of the TMJs of two living subjects. A band of fibromuscular tissue was found to run horizontally from the medial pole of the mandibular condyle to insert in an area of the sphenoid in front of the squamotympanic fissure. It is postulated that this glenomandibular band acts as a muscular antagonist to lateral Bennett movement.

Adult↗
PubMed1999

Dental treatment of patients with neurodegenerative disease.

Neurodegenerative disorders are among the most challenging and devastating illnesses in medicine. A heterogeneous group of chronic and progressive diseases, they include Alzheimer's, Parkinson's, and Huntington's diseases. Dentists faced with patients affected by one of these disorders are confronted with the major problems of cognition, mobility, and behaviour, as well as of dental maintenance. While treatment of patients with progressive neurodegeneration remains daunting, increased knowledge of the aetiology and pathogenesis of these diseases has provided new opportunities and a new understanding of their treatment needs. In this article, we briefly describe the effects of ageing on the brain, and introduce two of the major neurodegenerative disorders, Alzheimer's and Parkinson's diseases. The dental problems associated with these conditions include a decrease in oral hygiene, difficulty in controlling and retaining dentures, and purposeless chewing. Medications can result in xerostomia and consequent root caries and recurrent decay. Where possible, individuals with neurodegenerative disorders should always be treated by the same dentist.

Aging↗
PubMed1997

A clinical evaluation of a novel toothbrush design.

A new toothbrush design, the Snakebrush, was clinically evaluated along with the Flexible and Precision brushes. In this parallel, random-allocation investigation, the plaque removing qualities of the 3 brushes were evaluated over a period of 30 days. 60 patients of good dental health between the ages of 20 and 30 years formed the basis of the clinical trial. Mean plaque area scores were evaluated and recorded after a 1-min brush at baseline, day 15 and day 30. Gingivitis indices and bleeding on probing indices were also recorded at the same time intervals. Both uni- and multivariate analyses of our data suggested that the Snakebrush removed significantly more plaque than the 2 controls. For both lingual and buccal surfaces, subjects who had used the Snakebrush showed a significant decline in bleeding on probing and qinqivitis indices.

Adult↗
PubMed1997

The prevention and management of oral barotrauma.

The recent increase in the popularity of scuba diving has emphasised the role of the dentist in the prevention and treatment of oral barotrauma. Pain and injury to oral structures can result from rapid changes in pressure gradients, and involve enclosed spaces such as the sinuses, exposed dentinal tubules, or root canals. Three patients provide clinical examples of dental barotrauma and highlight the need for an awareness that some patients are divers who need meticulous restorative dentistry.

Adult↗
PubMed1996

Three-dimensional computed tomography reconstruction in treatment planning for large ameloblastoma.

A case of an unusually large mandibular ameloblastoma is reported in which standard radiologic examination failed to provide adequate visualization of the tumor's limits because of overlapping structures and the presence of compound shadows. Computed tomography imaging and three-dimensional reconstruction proved invaluable in the treatment planning of this large lesion, because it allowed the surgeon to visualize and comprehend the geography of the tumor and its relationship to surrounding structures and soft tissues and to formulate a surgical plan. Use of this technique helped ensure complete excision of the tumor without excessive removal of uninvolved tissue.

Ameloblastoma↗
PubMed1996

A mathematical model for hypothetical force distribution between opposing jaws.

In the present study we tested the hypothesis that the lower jaw was not simply a Class III lever in which bite force was simply related to jaw length. Dimensions considered relevant were measured on 58 (29 male) dry skulls housed in the Dart Collection. These values were then applied to a mathematical model in which were combined analyses of presumed forces in both sagittal and frontal planes. Our results show that calculated forces increase linearly along the model of a dental arch until a point Fmax is reached where calculated forces are maximized. Distal to Fmax there is a gradual drop off of force up to the posterior limit of the schematic dental arch. Point Fmax in models generated for males is at 56.54 mm and females at 53.31 mm from a baseline passing through the centroids of the glenoid fossae.

Biomechanical Phenomena↗
PubMed1996

Familial florid cemento-osseous dysplasia--a case report and review of the literature.

Cemento-osseous dysplasia is a fairly common lesion of the jaws originating from the elements of the periodontal ligament. Most lesions do not have a hereditary basis, however a few familial cases have been documented. This is the first report of the florid form of cemento-osseous dysplasia in an African family. The mother, son and one daughter exhibited multiple sclerotic cemental masses of the jaws with large tumour-like swellings in the symphyseal area of the mandible. In the case of the mother the lesions had become infected. The familial form of cemento-osseous dysplasia differs from the non-hereditary type in that the lesions present in children, all cases are florid in nature, there is no predilection for black females, the rate of growth appears to be more rapid and the symphyseal area of the mandible is most severely affected. The mode of transmission appears to be autosomal dominant with variable phenotypic expression.

Adolescent↗
PubMed1977

The effect of a proteolytic enzyem mixture (Orenzyme-Forte) on experimentally induced pulpitis.

A proteolytic enzyme mixture, Orenzyme-Forte, containing trypsin, chymotrypsin, and ribonuclease was used to treat experimentally induced pulpitis in the teeth of three monkeys. Assessment by means of the criteria of Stanley showed that the enzyme mixture induced better healing than a zinc oxide--eugenol dressing. When the two were used simultaneously, a synergistic effect was seen. We suggest that this enzyme mixture may be useful in clinical practice in the treatment of pulpitis.

Animals↗