The bicentenary of the birth of Sir John Tomes

John Tomes was initially destined for a career in medicine but after being introduced to dental histology, changed careers and gave the first series of lectures on dentistry in Middlesex Hospital. His early academic career resulted in four major papers on the structure of teeth and bone that were read before the Royal Society, establishing his reputation as a leading histologist. He was awarded an FRS at the age of 35. The last 40 years of his life were devoted to establishing dentistry as a regulated profession with the founding of a dental hospital, examinations undertaken by the Royal College of Surgeons, a dental register and regulation by the British Dental Association. He was knighted in 1886. The bicentenary of his birth was recognised with the restoration of his grave.

An immunohistochemical analysis of human Merkel cell density in gingival epithelium from dentate and edentulous subjects

OBJECTIVE

To investigate whether there is a difference in the density of Merkel cells between the gingiva of dentate and edentate subjects.

METHODS

One hundred and two blocks of human mandibular (n=55) and maxillary (n=47) gingiva from 69 white skinned individuals (44 males, 25 females, mean age 70.1 years, range 42--92 years) were analysed. Twenty-six individuals had teeth remaining in at least one jaw (mean age of dentate 64.5 years, edentate 72.1 years), of which 15 were dentate in both jaws. Overall, 24/55 mandibles and 17/47 maxillae were dentate. Five micrometer sections were stained with a monoclonal antibody to cytokeratin 20 (CK 20) using standard immunoperoxidase or immunoalkaline phosphatase methods. Positive cells were counted in 20 consecutive high power fields using the x 40 objective in three sections from each biopsy, and the results analysed for differences related to age, sex, site and presence of teeth.

RESULTS

CK 20-positive Merkel cells were present either singly or in clusters in the basal epithelial layers, particularly at the tips of rete ridges. Numbers of gingival Merkel cells were significantly higher (p<0.005, Mann-Whitney) in edentate (cells per field mean, median, standard deviation, respectively: 1.39, 0.64, and 1.85) when compared to dentate (0.67, 0.20, and 1.21) specimens. The differences were not statistically significant for any other variable.

CONCLUSION

The data raise the possibility that reduced perception following loss of teeth may be compensated for by an increase in the local Merkel cell population.

The differentiation profile of the epithelium of the human lip

The aim of this study was to analyse the immunohistochemical differentiation profile of the stratified squamous epithelium of the adult human lip. Full-thickness lower lips taken from 31 cadavers were analysed. Sections were stained with haematoxylin and eosin, periodic acid-Schiff (PAS), cytokeratins (CK), loricrin, involucrin, profilaggrin and filaggrin. The stratified squamous epithelium covering the lip could be divided into: (i) appendage-bearing, orthokeratinised epidermis; (ii) orthokeratinised vermilion which had a more prominent rete pattern than the epidermis; (iii) parakeratinised, PAS-positive intermediate zone; and (iv) non- or parakeratinised labial mucosal epithelium. Epithelial thickness increased gradually from the skin to the mucosal aspect. The CK pattern changed across the intermediate zone, with gradual loss of CK 1 and 10 from the skin, and CK 4, 13 and 19 from the mucosal, aspect. CK 5 and 14 were consistently expressed basally, and variably expressed suprabasally. Apart from labelling Merkel cells, CK 8, 18 and 20 were negative. Involucrin, which was present at all sites, was restricted to the stratum granulosum in skin, but extended into the stratum spinosum, and gradually into parabasal keratinocytes, across the vermilion and mucosa. Loricrin, profilaggrin and filaggrin were present in the stratum granulosum of orthokeratinised sites, but expression was abruptly lost at the junction between the vermilion and the intermediate zone. In conclusion, the phenotype of the stratified squamous epithelium covering the lip changes at, or across, the intermediate zone of the adult vermilion. It is possible that changes in the composition of the stratified squamous epithelium affect the colour of the vermilion.

Detailed morphology and distribution of gap junction protein associated with cells from the intra-articular disc of the rat temporomandibular joint

The present study details structural aspects of the cells of the rat intra-articular disc (IAD) of the temporomandibular joint. At the light and electron microscope level, the outline of the cells varied, although a number appeared oval/rounded. Ultrastructurally, the cells contained moderate amounts of the intracellular organelles associated with protein synthesis. Cell processes were not a prominent feature seen using these techniques. However, using confocal microscopy, phalloidin staining revealed the presence of numerous, actin-rich, long, thin, branching processes emanating from the cell membranes. Double staining for connexin 43 revealed that the cell processes showed dense, punctate positive staining for this gap junction protein along their whole length. These observations provide the basis for a transport mechanism for nutritive molecules from the periphery of the IAD (where blood vessels are present) to the central portions of the disc (where blood vessels are absent).

Morphometric appraisal of the skull of Caroline Crachami, the Sicilian "dwarf" 1815?-1824: a contribution to the study of primordial microcephalic dwarfism

The skeleton of Caroline Crachami is a rare historical example of primordial microcephalic dwarfism (PMD). Studies show the condition to be heterogeneous, with at least three types, for which the assessment criteria rely on descriptive evaluations and/or simple measures with regard to cranial features. Advances in noninvasive imaging allow for a more complete morphometric examination of the skull of Caroline Crachami with the aim of clarifying aspects of the condition. In the present study, the skull of Caroline Crachami was three-dimensionally imaged with computed tomography (CT) and reconstructed in virtual space. Coordinates for a number of measurements were taken to represent interesting anatomies with an emphasis on those measures not easily replicated on the skull itself. Volumes of the endocranial cavity and sella turcica were also computed. These data were compared with normative values taken from the literature and measured from CT images of the Bosma collection. Findings indicate that the general size of the skull is equivalent to that of a 6- to 8-month-old, that the endocranial volume and cranial base angle are commensurate with that of a newborn, and that the sella volume is the same as that for an 8- to 15-month-old. Apart from these traits, the skull was well proportioned and within the range of normal variation for a skull aged between 2-9 years. We conclude that further quantitative analysis on related skulls is warranted in the study of PMD using the methods and techniques described.

Ultrastructure of the human intra-articular disc of the temporomandibular joint

The ultrastructural appearance of the human intra-articular disc (IAD) was investigated in three discs that had been surgically removed due to disease from three female patients aged 47, 50, and 54 years of age. Regions of the IAD were selected from central areas that appeared to be least affected by disease. Sections were fixed in 2.5 per cent glutaraldehyde in 0.1 M phosphate buffer, pH 7.3 immediately after surgery. The regions examined showed no obvious signs of inflammation. The cells showed moderate amounts of the intracellular organelles associated with protein synthesis and secretion, and possessed considerable amounts of microfilamentous material, thus resembling those described in other mammals. Despite the large number of cells examined, only one cell showed evidence of a chondrocyte-like morphology in that it possessed an incomplete pericellular zone of microfilamentous material separating the cell membrane from the adjacent collagen bundles of the extracellular matrix (ECM). Thus, on morphological grounds, fibrocartilage was virtually non-existent in the specimens examined. The mean collagen fibril diameter was 43.9 nm and the fibril diameter distribution was not unimodal. Although the majority of fibrils had a relatively small diameter, two of the three specimens possessed many fibrils with diameters of over 100 nm, this being consistent with tissue subjected to tension. The mean area of a fibre bundle occupied by collagen (as opposed to the ground substance) was approximately 56 per cent.

Tooth onoteny in Didelphis virginiana (Marsupialia : Didelphidae)

The ontogenetic development of the teeth was studied in a series of seven specimens of Didelphis virginiana whose crown-rump length varied from 11 to 49 mm. Though all developing teeth showed undifferentiated lingual downgrowths of dental lamina, there was no evidence of any non-functional teeth. No more than five upper incisors were present at any one time. The metacone was the first cusp to calcify in the upper deciduous and fist permanent molar teeth. The protoconid was the first cusp to calcify in the lower molar teeth. The results were compared with findings from a recent study of tooth ontogeny in Antechinus flavipes.