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Dental erosion is an increasing problem in many countries around the world, and research in this field has increased dramatically in recent years. Dental erosion is the dissolution of tooth tissues by acids that are not of bacterial origin; most commonly these originate from the diet. Methods to reduce erosion are of great import; the application of milk-derived proteins such as casein and casein-derived proteins are of current interest as anti-erosion agents and are the subject of the work presented here in this thesis. The efficacy of casein and casein-derived proteins as agents to inhibit dissolution of hydroxyapatite in simple citric acid solutions are investigated in chapters 3 and 4 with two different in vitro models. It was found that these proteins inhibit hydroxyapatite dissolution over a range of erosion timescales, concentrations and exposure times. The effect of an in vitro formed salivary pellicle is also examined and the proteins were shown to retain their efficacy. The efficacy of these proteins to inhibit the earliest stages of erosion (surface softening) and more progressed stages of erosion (bulk tissue loss) are investigated in chapter 5 using atomic force microscopy nanoindentation and non-contact optical profilometry respectively. It was found that again these proteins inhibit both surface softening and bulk tissue loss of bovine enamel. The nature of the protective mechanism due to casein is investigated in chapter 6 using a range of complementary, inter-disciplinary techniques such as atomic force microscopy, x-ray reflectometry and sodium dodecyl sulphate polyacrylamide gel electrophoresis. The protective effect is ascribed to a thin protein film, of 6.6 nm in thickness, forming on the mineral surface. In conclusion, casein and casein-derived proteins are shown to have anti-erosion properties and potential as oral healthcare products.

Copies of author's previously published articles inserted. / Bibliography: leaves 121-137. / ix, 138 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Investigates the pattern of reflexes evoked by stretch in a human jaw-closing muscle (masseter) at the level of the whole muscle and individual motor units. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physiology, 1994

Typescript (Photocopy) / Copy of published paper co-authored by author, in back / Bibliography: leaves 209-228 / xiv, 232 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, 1989

There is a general assumption that permanent teeth in children are emerging into the oral cavity earlier than the dates given in published scientific studies conducted many years ago. In the course of this research a rigorous experimental protocol was devised to provide reliable data collection and analysis methods and give contemporary emergence rate estimations with a strong scientific basis. In addition equations are presented to predict the chronological age of children using only the sex of the child and the number of permanent teeth present. Data was collected between April 1998 and July 2001 from 12,395 children between 4 and 15 years of age, in the Colchester area of the UK. The results show that the ages of emergence of the permanent teeth are later than previously assumed. This research also confirms previous research showing that girl's teeth emerge before boy's teeth, that there is no statistical difference in the age of emergence contra-lateral teeth in the same arch and that there is a statistical difference in the age of emergence of ipsi-lateral teeth in opposing arches.

Il a été récemment montré que la vasorine (Vasn), d’abord décrite comme une protéine membranaire de type I qui neutralise TGFb, était exprimée par les ostéocytes et les ostéoblastes et impliquée dans le métabolisme du phosphate et du calcium. L’analyse MicroCT a montré que des souris Vasn -/- présentaient des signes de rachitisme avec des volumes osseux trabéculaires et corticaux fortement réduits. Ici, nous explorons pour la première fois l’expression et les fonctions de Vasn dans le territoire craniofacial. Nous démontrons que 1) Vasn est exprimée au sein de la dent en formation par les odontoblastes et les cémentoblastes et dans l’os alvéolaire par les ostéoblastes et les ostéocytes, 2) des souris Vasn -/- présentent un phénotype dentaire mixte associant des signes de rachitisme tels qu’une croissance réduite du squelette, une dentine minéralisée moins épaisse, des chambres pulpaires élargies et des signes supplémentaires évoquant une hypophosphatasie , principalement une formation perturbée de la racine avec des canaux dentaires élargis. Toutes ces données suggèrent un rôle important de Vasn dans la minéralisation de l’os et de la dent, probablement en régulant le dépôt de matrice et son organisation, plutôt que le processus de minéralisation lui-même. / Vasorin (Vasn), first described as a type I membrane protein which neutralizes TGFβ, has been recently shown to be expressed by osteocytes and osteoblasts and involved in the phosphate and calcium metabolism. MicroCT analysis have indicated that Vasn -/- mice displayed signs of rickets with dramatically reduced trabecular and cortical bone volumes. Here, we explored for the first time Vasn expression and function in the craniofacial area. We demonstrated that 1) Vasn is expressed in the forming tooth by odontoblasts and cementoblasts and in the alveolar bone by osteoblasts and osteocytes, 2) Vasn-/- mice present a mix cranial and dental phenotype associating signs of rickets such as, reduced skull growth, reduced thickness of mineralized dentin, and enlarged pulp chambers, and additional signs evokating hypophosphatasia, namely disturbed root formation with enlarged root canals. All these data suggest an important role of Vasn in bone and tooth mineralization, probably by regulating matrix deposition and organization rather than the mineralisation process itself.