| Summary: | 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.
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