No description available.

In recent years, bleaching has become very popular as an effective method of whitening teeth. Although bleaching is considered a conservative technique for improving aesthetics, it has the potential to cause adverse changes to dental tissues and biomaterials. The aim of this research was to assess the effect of varying concentrations of bleaching agents on (i) tooth demineralisation and microhardness, and (ii) metal ion release from dental amalgams and casting alloys. Freshly extracted bovine incisor teeth were investigated before and after bleaching with hydrogen peroxide (10% - 30% w/v). The results showed a significant decrease in mineral content of both enamel and dentine following bleaching. The enamel also exhibited an associated reduction in microhardness when bleached. Tests were carried out on amalgam discs bleached with hydrogen peroxide (0-30% w/v). Data showed a significant increase in Hg, Cu, Ag and Sn ion release with increasing hydrogen peroxide concentrations. Similar tests were carried out on two typical dental casting alloys, Ni-Cr and Pd-Cu-Ga. The data again indicated an increase in ion release with increasing hydrogen peroxide concentrations. The elevated ion release from dental amalgams, casting alloys and mineralised tooth tissues suggested that caution should be exercised when applying bleaching agents. Moreover, there is a case for not applying hydrogen peroxide at relatively high concentrations. The data reported here reinforces the view that bleaching agents may have deleterious effects, especially if bleaching agents are applied at high concentrations and/or long periods.

No description available.

No description available.

No description available.

No description available.

Dentine sensitivity is a common dental complaint. It is caused by the exposure of root dentine to the oral environment. A popular method of overcoming dentine sensitivity is the occlusion of the dentinal tubules. In this thesis the use of nanoparticulate silica sols, of sizes 7, 14 and 21 nm diameter for the treatment of dentine sensitivity, as occluding agents was explored. Previous work at the University of Liverpool has identified a simple two step method for coating surfaces in silica nanoparticles. This process required the use of a poly cationic polymer (Zetag 7689). TEM and QCM-D were used to observe the creation of nanoparticulate coatings, in the absence and following manipulation of the polymer binding layer. It was demonstrated that on gold, carbon and hydroxyapatite surfaces a polymer binding layer was required. However, using the QCM-D and XPS it was identified that on dentine surfaces a polymer binding layer was unnecessary.

Dental erosion has increased in prevalence over the last decades. The wider availability and frequent consumption of acidic soft drinks and other acidic substances is thought to be one of the main aetiological factors. It is also well established that this frequent exposure of dental hard tissue surfaces to such acidic attacks renders the outermost enamel layer softened and readily susceptible to be rubbed away by mechanical forces. While most of the studies emphasised on the role of toothbrushing, the effect of oral musculature, especially the tongue, is considered to play a major part in abrading pre - eroded enamel surfaces. Despite the attempts to in vitro simulate tongue abrasion; there is a lack in the literature regarding its role as a causative factor in tooth surface loss. The work presented in this thesis is divided into six chapters. The first chapter includes a general review on tooth wear, enamel erosion and abrasion in particular, referring to the various techniques commonly used to quantify enamel mineral and surface loss. Chapter 2 investigates the erosive effect of some commercially available alcoholic beverages (alcopops) on enamel surfaces. The results from that study showed that alcopops have a significant potential to cause erosion similar to that of orange juice. Further, in the same chapter, a group of dental materials commonly used to mount tooth specimens in erosion studies were examined for their fluorescence properties. It was found that some of those materials exhibited fluorescence activity that affected the quality of images using equipments such as quantitative light - induced fluorescence. Chapter 3 demonstrates that the application of tooth whitening products is not without risking enamel surfaces to undergo erosion and that chlorine dioxide bleaching products, although to a lesser extent, can cause surface demineralisation similar to that caused by hydrogen peroxide. In chapter 4, the effect of simulated tongue abrasion on pre - eroded enamel surfaces is investigated over different periods of erosion and abrasion cycles. Results from that study revealed a significant amount of mineral and surface loss after the application of tongue simulated movements particularly when erosion times were prolonged. Chapter 5 describes an in vitro study where the super saturation of artificial saliva with calcium ions has greater remineralisation properties than the specially formulated Pronamel® mouth wash, deionised water and modified artificial saliva without calcium. The mouthwash has superior remineralisation effect while the two latter solutions, particularly the modified artificial saliva without calcium, caused the greatest mineral loss and lesion depth. Chapter 6 embraces two studies; an in situ part investigating the effect of tongue abrasion on pre - eroded enamel surfaces in addition to an in vitro pilot study investigating the period required for those eroded surfaces to be physically lost to form craters. The findings from the in situ study shows that short and cyclic exposure of enamel specimens to acidic drinks followed by mechanical abrasion by the tongue results in an increased mineral and surface loss. This effect was more recognised on specimens localised opposite to the upper anterior teeth. Also, labial and palatal enamel surfaces have similar mineral and surface loss. Enamel craters formed after as early as 1 week and showed a significant depth after 4 weeks of exposure to orange juice. In conclusion, it has been shown that the tongue could exert an amount of pressure sufficient to remove pre - eroded enamel surfaces.

La dent est un tissu vivant, confronté tout au long de la vie à de multiples agressions (caries, traumatismes...) qui peuvent entraîner la nécrose de la pulpe. La mise au point d’une «pulpe équivalente» pourrait constituer une approche thérapeutique innovante comme alternative aux traitements actuels d’endodontie. La pulpe des dents temporaires constitue un réservoir de cellules souches mésenchymateuses (SHED Stem cells from Human Exfoliated Deciduous teeth) aux potentiels de prolifération et de différenciation élevés. L’objectif global de ce travail est de reconstituer un tissu pulpaire fonctionnel en développant une pulpe équivalente (cellules pulpaires mésenchymateuses ensemencées dans une matrice 3D de collagène) pour être greffée à l’intérieur de la chambre pulpaire préalablement évidée afin de conserver la vitalité de la dent. Les objectifs spécifiques ont été : In vitro : 1) d'étudier le potentiel angiogénique des SHED comparés à des fibroblastes dermiques en conditions normoxiques et hypoxiques, 2) de déterminer la durée de pré-conditionnement hypoxique optimale pour stimuler le potentiel angiogénique des SHED, 3) de sélectionner une potentielle cytokine activant la formation de capillaires, 4) d’analyser l’effet de l’hypoxie sur l’expression des marqueurs de surfaces des SHED, et 5) de vérifier que l’hypoxie n’altérait pas le potentiel de minéralisation de ces cellules. In vivo : 1) d’évaluer, dans un modèle pré-clinique d’implantation de pulpes équivalentes en site ectopique chez la souris, l’effet du pré-conditionnement hypoxique sur le potentiel angiogénique des SHED. Ces expériences ont d’abord été conduites avec des cellules pulpaires de souris puis confirmées avec des SHED implantées dans des souris immunodéficientes, et 2) de développer des techniques d’imagerie dynamique pour suivre la néoangiogenèse dans les pulpes équivalentes implantées. Enfin, dans un objectif de transfert vers la clinique dentaire humaine, nous avons étudié l’effet d’un nouveau biomatériau à base de calcium tricalcique sur la réparation tissulaire dans un modèle de blessure pulpaire chez le rat, en comparaison aux matériaux de référence. / The tooth is a living organ, faced throughout life to multiple attacks (caries, trauma ...) which can cause necrosis of the pulp. The development of a" pulp equivalent " could be an innovative therapeutic approach as an alternative to current endodontic treatments. The pulp of deciduous teeth is a reservoir of mesenchymal stem cells (Stem cells SHED from Human Exfoliated Deciduous teeth) with a high potential of proliferation and differentiation. The overall objective of this work was to reconstitute a functional pulp tissue by developing a pulp equivalent (pulp mesenchymal cells seeded in a 3D collagen matrix) to be grafted within the previously hollowed pulp chamber to maintain tooth vitality. The specific objectives were: In vitro: 1) to study the angiogenic potential of SHED compared with dermal fibroblasts in normoxic and hypoxic conditions. 2) to determine the optimal hypoxic preconditioning period to stimulate the angiogenic potential of SHED, 3) to identify a potential cytokine activating the capillary formation, 4) to analyze the effect of hypoxia on the expression of markers surfaces SHED, and 5) to check that hypoxia did not alter the mineralization potential of these cells. In vivo: 1) to evaluate, in a pre-clinical model of pulp equivalent implantation in ectopic site in mice, the effect of either hypoxic or FGF preconditioning on the angiogenic potential of SHED. These experiments were first conducted with mouse pulp cells and further confirmed with SHED implanted in immunodeficient mice, and 2) to develop dynamic imaging techniques to monitor neoangiogenesis within pulp equivalent. Finally, in an objective of transfer to the human dental clinic, we studied the effect of a new biomaterial based on tricalcium on tissue repair in a pulp injury model in rats, compared to gold standard materials.

La dent est un tissu vivant, confronté tout au long de la vie à de multiples agressions (caries, traumatismes...) qui peuvent entraîner la nécrose de la pulpe. La mise au point d’une «pulpe équivalente» pourrait constituer une approche thérapeutique innovante comme alternative aux traitements actuels d’endodontie. La pulpe des dents temporaires constitue un réservoir de cellules souches mésenchymateuses (SHED Stem cells from Human Exfoliated Deciduous teeth) aux potentiels de prolifération et de différenciation élevés. L’objectif global de ce travail est de reconstituer un tissu pulpaire fonctionnel en développant une pulpe équivalente (cellules pulpaires mésenchymateuses ensemencées dans une matrice 3D de collagène) pour être greffée à l’intérieur de la chambre pulpaire préalablement évidée afin de conserver la vitalité de la dent. Les objectifs spécifiques ont été : In vitro : 1) d'étudier le potentiel angiogénique des SHED comparés à des fibroblastes dermiques en conditions normoxiques et hypoxiques, 2) de déterminer la durée de pré-conditionnement hypoxique optimale pour stimuler le potentiel angiogénique des SHED, 3) de sélectionner une potentielle cytokine activant la formation de capillaires, 4) d’analyser l’effet de l’hypoxie sur l’expression des marqueurs de surfaces des SHED, et 5) de vérifier que l’hypoxie n’altérait pas le potentiel de minéralisation de ces cellules. In vivo : 1) d’évaluer, dans un modèle pré-clinique d’implantation de pulpes équivalentes en site ectopique chez la souris, l’effet du pré-conditionnement hypoxique sur le potentiel angiogénique des SHED. Ces expériences ont d’abord été conduites avec des cellules pulpaires de souris puis confirmées avec des SHED implantées dans des souris immunodéficientes, et 2) de développer des techniques d’imagerie dynamique pour suivre la néoangiogenèse dans les pulpes équivalentes implantées. Enfin, dans un objectif de transfert vers la clinique dentaire humaine, nous avons étudié l’effet d’un nouveau biomatériau à base de calcium tricalcique sur la réparation tissulaire dans un modèle de blessure pulpaire chez le rat, en comparaison aux matériaux de référence. / The tooth is a living organ, faced throughout life to multiple attacks (caries, trauma ...) which can cause necrosis of the pulp. The development of a" pulp equivalent " could be an innovative therapeutic approach as an alternative to current endodontic treatments. The pulp of deciduous teeth is a reservoir of mesenchymal stem cells (Stem cells SHED from Human Exfoliated Deciduous teeth) with a high potential of proliferation and differentiation. The overall objective of this work was to reconstitute a functional pulp tissue by developing a pulp equivalent (pulp mesenchymal cells seeded in a 3D collagen matrix) to be grafted within the previously hollowed pulp chamber to maintain tooth vitality. The specific objectives were: In vitro: 1) to study the angiogenic potential of SHED compared with dermal fibroblasts in normoxic and hypoxic conditions. 2) to determine the optimal hypoxic preconditioning period to stimulate the angiogenic potential of SHED, 3) to identify a potential cytokine activating the capillary formation, 4) to analyze the effect of hypoxia on the expression of markers surfaces SHED, and 5) to check that hypoxia did not alter the mineralization potential of these cells. In vivo: 1) to evaluate, in a pre-clinical model of pulp equivalent implantation in ectopic site in mice, the effect of either hypoxic or FGF preconditioning on the angiogenic potential of SHED. These experiments were first conducted with mouse pulp cells and further confirmed with SHED implanted in immunodeficient mice, and 2) to develop dynamic imaging techniques to monitor neoangiogenesis within pulp equivalent. Finally, in an objective of transfer to the human dental clinic, we studied the effect of a new biomaterial based on tricalcium on tissue repair in a pulp injury model in rats, compared to gold standard materials.