True oligodontia with microdontia in monozygous twins: implications for reappraisal of Butler's Field Theory.

Oligodontia, which may be defined as the congenital absence of six or more teeth apart from third molars, affects less than 0.5% of the population and may occur in isolation or as part of a syndrome. This paper aims to clarify the role of genetic factors in this condition by reporting a case of a pair of identical twins and their mother who display similar patterns of oligodontia without medical problems. Each twin has 13 missing permanent teeth and their mother 16 missing teeth, but the patterns of agenesis do not conform with Butler's Field Theory according to which the distal teeth in each class are most likely to be absent. Unerupted third molars are present in both twins and all three family members display maxillary lateral incisors. Dental crown size profile patterns were computed for all three individuals and highlight a marked reduction in mesiodistal and buccolingual dimensions of the remaining teeth in each. In addition, erupted teeth showed simplified crown morphology. Oligodontia should not be viewed in isolation, but rather considered as one manifestation of a variety of dental changes in genetically susceptible individuals.

Reviewing the role of educational domains and problem-based learning in dental curricula. Part I: The concept of educational domains and their integration.

This review of educational domains and problem-based learning in dental curricula examines the concept of educational domains under the following headings: the domains of skills and knowledge within which we expect students to demonstrate proficiency whether a course should be integrated, both vertically and horizontally between academic disciplines whether these domains are achievable by problem-based learning in whole or in part, and the type of learning domain or skill which is expected from students, such as cognitive, psychomotor and affective. Part I will deal with the first two aspects, while Part II (to be published in SADJ September 2000) will deal with problem-based learning (PBL) and the skills required of students.

Learning relational anatomy by correlating thin plastinated sections and magnetic resonance images: preparation of specimens.

Plastination is a process whereby the tissue water and part of the tissue fat of anatomical specimens is replaced with a curable polymer. Several variations of this technique are available, depending on both the type of specimen and polymer being used. In this study, the efficiency of BIODUR PEM 11-prepared cross sections as a teaching aid for radiographic anatomy is investigated. A human cadaveric head was scanned on a magnetic resonance (MR) imager, recording images in a coronal plane of approximately 6 mm in thickness. Corresponding slices were then taken of this head and plastinated by the BIODUR PEM 11 method. In general, a good correlation existed between the plastinated sections and the MR scans. The plastinated slices displayed superior differentiation between musculature compared to the scans. In conclusion, the plastinated sections, used in conjunction with the MR scans, are a valuable tool in learning radiographic anatomy. Additionally, BIODUR PEM 11 is a viable alternative to plastination by other methods.

The forensic implications of palaeopathology of the cranium and jaws. Part I. A technique for radiography of mummified and skeletal remains.

Radiography of dried skulls presents two major problems: the lack of soft tissue which usually leads to overexposure, and difficulty in maintaining the cranium, with or without mandible, in correct position. The first problem can be alleviated by suspending a one litre drip bag containing Hartman's solution across the X-ray tube head and angled to give a fluid thickness of 10 cm. Satisfactory positioning of the skulls and relating the mandible to cranium was achieved by construction of a spinal column substitute and acrylic hooks and rubber bands. Exposure of 50 KV and 10 mA at 15 seconds for orthopantomographic views and 70 KV at 1.5 seconds for lateral and 65 KV at 1.5 seconds for postero-anterior views gave an optimal, clinically acceptable image. The perfused fluids of living tissues exert a strong, modifying influence on the X-ray beam.

Microsurgical anatomy of the inferior alveolar neurovascular plexus.

Microdissection of the cadaveric human inferior neurovascular bundle showed that the inferior alveolar nerve after its origin from the mandibular division forms what can only be described as a plexus. The main trunk of the inferior alveolar nerve exhibits a branching structure reminiscent of the brachial plexus of the upper limb. This plexus-like nature is compounded by delicate interweaving of the inferior alveolar artery. Study of external carotid angiograms showed a general decrease in size of the inferior alveolar artery with increase in age.

Stem and stromal cell reconstitution of lethally irradiated mice following transplantation of hematopoietic tissue from donors of various ages.

If the limited life span of hematopoietic tissues in vitro is due to a finite proliferative capacity of individual stem cells, one might expect tissues of young donors to possess a greater proliferative capacity and to contain a larger population of primitive stem cells than those of older donors. To test this hypothesis, we used 12- and 8-day spleen colony formation (CFU-s) to assay more and less primitive stem cell subpopulations of three murine hematopoietic tissues: fetal liver (FL) and weanling (WBM) and adult (ABM) bone marrow. Subsequently, the same assays and a stromal cell assay were performed on the bone marrow from groups of lethally irradiated mice reconstituted with these tissues. Comparison of the CFU-s content of the donor tissues revealed that FL contained a significantly greater proportion of primitive stem cells as evidenced by a (Day 12):(Day 8) CFU-s ratio of 3.0 +/- 1.0 as compared to 0.9 +/- 0.1 for WBM and ABM. In addition, at 21 weeks post-transplantation the CFU-s/femur values of the FL reconstituted group were significantly greater than those of the ABM and WBM reconstituted groups. These results suggest that fetal hematopoietic tissue contains a greater proportion of primitive stem cells and has a greater proliferative potential than hematopoietic tissue from older donors. No differences were seen in stromal cell reconstitution of the three experimental groups. In all cases, assayable fibroblast colony forming cells (CFU-f) remained at 20-40% of control values, even at 21 weeks postreconstitution.

Aspects of the content versus process debate in medical education.

Traditional western medical education is often concerned with the absorption of an enormous number of facts, leaving the process of problem-solving to happen naturally. The current trend is to increase the process in medical education, sometimes at the expense of content knowledge. This paper analyses some of the literature pertinent to this dilemma. It concludes that a pluralistic approach to the presentation of the scientific process would enhance the student's motivation to obtain the content knowledge necessary to utilize that scientific process. It also suggests that such an approach to education might benefit all professions which rely on problem-solving as part of their activity.

Scientism vs humanism in medical education.

There is strong evidence to suggest that there is an ideological acceptance of science in the general community. This paper reviews some of the evidence to suggest that a form of scientism (i.e. the belief that only the current scientific method of the natural sciences can fruitfully be used in the pursuit of knowledge) has pervaded the practise of medicine and medical education. It argues for exposure of medical students to the humanistic growth-model of medicine and illness as well as the traditional disease-model. It is suggested also that the entrenchment of the disease model in medical education is a direct and inevitable result of the entrenchment of scientific method in medicine, to the point where such method is ideologically accepted in medical practice.

Oral condyloma acuminatum or venereal wart. Case report.

Oral condyloma acuminatum or venereal wart is an infectious disease of the oral mucosa caused by a virus similar or identical to that causing Verrucae vulgaris and plantaris. It consists of papillomatous projections with marked parakeratosis or keratosis and acanthotic epithelial downgrowths. Vacuolated cells are often a feature of the stratum spinosum. Criteria for the differential diagnosis and surgical management of this condition are presented.

Characteristics of the Papua New Guinean dentition. II. Normal occlusion in an adolescent population.

Data on dental arch form and size, tooth arrangement and occlusion are presented for 32 adolescents from Wewak, Papua New Guinea, and compared with measurements of similar adult populations. Each person examined had a Class I occlusal relationship.

Characteristics of the Papua New Guinean dentition. I Shovel-shaped incisors and canines associated with lingual tubercles.

The prevalence of shovel-shaped and lingual tubercles in maxillary incisors and canines in four groups of people in Papua New Guinea is reported. The shovel shape was not common among the people of Highland New Guinea but its presence in Papuans was comparable with that in Mongoloid races.

Palatal epithelium of a monotreme and a marsupial.

The palatal epithelium of a monotreme, Tachyglossus aculeatus and a marsupial, Tarsipes spenserae were examined histologically and with the scanning electron microscope. Each animal possess keratinized palatal spines which although histologically similar, show significant differences in their external morphology. It is suggested that the spines in each case are highly differentiated filiform papillae which have developed as a compensatory mechanism of mastication, since both animals are in effect, edentulous. In the light of these findings and observations on the tongue of both animals, it is suggested that a degree of parallel evolution of the palate (as part of the masticatory apparatus) has occurred.

Review of the evolution and phylogeny of the mammalian tongue.

Evolution of the mammalian tongue has been characterized by a number of extensive structural adaptations for the highly specialized functions which various tongues perform. Variations in shape, epithelium, muscle arrangement and mechanisms of lingual stiffening are described, and the possible way in which such changes have occurred is discussed. The review also shows that a study of the tongue's structure in conjunction with other anatomical features may serve as a useful indicator of an animal's habits and diet and provide important information for taxonomic purpose.