The fine structure of the developing human periodontium

Neil Goldsworthy and his legacy: Sydney's Institute of Dental Research

Dr. Neil Goldsworthy had a profound effect on the development of dental research in the biological sciences in Australia, including measures for the prevention of dental caries. He played a major role in the establishment of the Institute of Dental Research in Sydney in 1946 and was Director until his sudden death in 1960. Reviewing the Institute's activities provides the opportunity for his achievements to receive due recognition and to show how they influenced its subsequent development. As one who has been associated with the Institute for most of the last 50 years, it is an honor for me to undertake this task.

Collagen fiber reunion in wound repair: transmission electron microscopic study of rat gingiva

The purpose of this study was to characterize connective tissue at the site of reunion following surgical injury of the transseptal fiber system in rat molars. Eight conventional albino rats aged 50 days were incised interdentally and the lesions allowed to heal for 14 days followed by specimen preparation for transmission electron microscopy. Four specimens with identifiable areas of fiber attachment at the light microscopic level of magnification were selected for a detailed ultrastructural examination. Transitional connective tissue consisted of thin (250-375 A) and thick (greater than or equal to 450 A) collagen fibrils at a ratio of 41/59 mainly arranged as aggregates of uniformly sized fibrils. Fibril thickness in the vicinity of fibroblasts (n = 40) varied at a ratio of 65 (thin)/35 (thick). Distribution and spatial arrangement of fibrillar components indicate that the site of reunion is characterized by separate aggregates of fibrils rather than alignment of individual collagen fibrils of varying thickness suggestive of covalent linkage.

Ultrastructural cytochemistry of oxytalan fibres in monkey periodontal ligaments with the high iron diamine method

Monkey periodontal ligaments have been examined at the ultrastructural level to demonstrate the nature of reactive sites in oxytalan fibres. The high iron diamine (HID) and HID-thiocarbohydrazide-silver proteinate methods specific for sulphate groups, with and without prior oxidation with monopersulphate, were used. Oxytalan fibres were composed of bundles of microfibrils with a diameter of 11.5 +/- 1.7 nm (mean +/- S.D., n = 50). In cross section the microfibrils were found to have a denser periphery, giving them a 'tubular' appearance. The oxytalan microfibrils of non-oxidized specimens showed little reactivity with either HID method, except that the extracellular matrix material in close association with collagen fibrils stained weakly; in oxidized specimens, both HID methods strongly stained oxytalan microfibrils and weakly stained the extracellular matrix material. Such reactivity of oxytalan microfibrils was not altered by digestion with testicular hyaluronidase or chondroitinase ABC, performed prior to or after persulphate oxidation. Further, the sequential thiosulphation and HID method for the demonstration of disulphide and sulphhydryl groups stained oxytalan fibres moderately. These results indicate that the oxidative generation of sulphate groups in oxytalan fibres may occur from either disulphide or sulphhydryl groups, or both, rather than the result of unmasking of sulphated glycosaminoglycans.

Ultrastructural evidence of nerve and oxytalan fibre associations in the endoneurium of human periodontal ligament

Human periodontal ligament from premolars contained numerous fibres of the oxytalan meshwork system affiliated with unmyelinated endoneurium and myelinated nerves in the endoneurium. These fibres consisted of bundles of microfibrils and were present within 0.5 mu of Schwann cells and their unmyelinated axons. This ultrastructural association has not been previously demonstrated.

Fibril diameters in the extracellular matrix of the periodontal connective tissues of the rat

The diameters of collagen fibrils were measured in three varieties of periodontal connective tissue in the rat mandible (incisor periodontal ligament, incisor enamel-related connective tissue and molar periodontal ligament). Despite structural and functional differences between the tissues, a similar range of collagen fibril diameters was seen in each (average 45 nm). Variation between animals and between adjacent fiber bundles in any given tissue was observed. Even within any single fiber bundle, the fibrils had a variety of diameters. Although it has been claimed that collagen fibrils have diameters which are multiples of 8 nm, such a relationship could not be discerned for periodontal collagen fibrils. It was estimated that about 65 per cent of a periodontal collagen fiber bundle or sheet is composed of ground substance. Despite reports of abundant oxytalan fibers in periodontal tissues at the light microscope level, only one fiber having characteristics of oxytalan was observed in this electron microscopic study. Some aspects of the functional significance of the findings are discussed.

Electron dense staining affinities of mouse oxytalan and elastic fibers

The staining affinity of electron dense stains to mouse palatal elastic fibers and periodontal oxytalan fibers was assessed and compared. Tissues were stained routinely with uranyl acetate and lead citrate or with elastic tissue stains including: (1) silver tetraphenylporphine sulfonate, (2) tannic acid technique, and (3) a high iron diamine sequence. Staining results were assessed with an electron microscope. Palatal elastic fibers demonstrated staining affinity to all elastic stain techniques. Oxytalan fibers did not demonstrate affinity to elastic fiber stains used. Based on electron dense stains, elastic and oxytalan fibers were dissimilar, in contrast to results reported utilizing light microscopic stains.

A comparative light microscopic evaluation of oxytalan fiber staining with a variety of dye substances

Staining of oxytalan fibers in marsupial, eutherian and human periodontal ligaments was surveyed with 65 different dyes. Using the criteria of response to preoxidation, distribution, and morphologic appearance, 27 dye preparations in addition to the Gomori aldehyde-fuchsin, Taenzer-Unna orcein, and Weigert resorcin-fuchsin techniques displayed oxytalan fibers. With two exceptions all dyes were cationic and reacted with varying degrees of excellence with different animals. Most dyes produced their best staining results as concentrated solutions in 3% acetic acid, suggesting involvement of oxidatively engendered polyanions predominantly associated with an acid mucopolysaccharide component of the oxytalan fiber. The significance of carboxyl and sulfur-containing groups should not be overlooked in further studies aiming to elucidate oxytalan fiber chemistry and microstructure. This study supported the view that oxytalan fibers belong to the family of elastic tissues and represent a biologically important system within the periodontal ligament.

Oxytalan fibre formation in the cornea: a light and electron microscopical study

Oxytalan is a fibrillar protein possessing some of the staining and ultrastructural properties of developing elastic tissue. In a study of human corneae we failed to find fibres of this type in five normal specimens but found them in each of 16 examples of keratoconus and 13 cases of post-traumatic or post-inflammatory scarring. In two cases the microfibrillar nature of the deposits was confirmed by electron microscopy, individual microfibrils measuring 10-12 nm in diameter and having profiles suggestive of a tubular structure. Oxytalan formation was intimately associated with the basal lamina of the covering epithelium with, in areas showing disruption of Bowman's layer and scarring, some extension into the superficial collagenous stroma.

Ultrastructural studies of human gingiva. V. Microfibrils of elastic nature and their direct penetration of the basal lamina in chronic periodontitis

In this study, microfibrils widely distributed in the connective tissue of the gingival wall of periodontal pockets were examined by electron microscopy, Theirdistribution, ultrastructural characteristics, close association with fibroblasts and direct communication with the basal lamina were shown. The microfibrils in our specimens were observed in three different groupings (Types A, B, and C). They were believedto represent different stages of maturation of elastic fibera. There was a striking ultrastructural resemblance between oxytalan microfibrils, and the immature or imcompletetype of elastic fiber shown in this report.