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Lasers have been available for use in dentistry for several years but they are still not widely used in general practice due to expensive technology. The purpose of this research was to study the structure and properties of laser cut tooth surface and the way in which they react with materials to form an effectively bonded and sealed interface. The investigation of laser irradiated dentine showed that the reduction of microhardness by 30-50% compared to baseline dentine. Dentine debris was seen on the surface under SEM microscopy. The interface between the tooth surface prepared by the laser and glass ionomer cement was investigated using confocal microscopy. In addition, the microleakage of cavity prepared by bur and laser was compared. The adhesion of glass ionomer cement to Er, Cr:YSGG laser cut dentine was measured by means of both microtensile and shear bond strength tests. The mode of failure was assessed by microscopy. The optimal laser parameters were determined. It was found that the bond strength of glass ionomer cement to laser prepared dentine was generally not different from that to conventional cavity preparation. The use of a dentine conditioner had a significant effect on bond strength. This work suggests that the optimal parameters for use of the Er,Cr:YSGG laser to prepare cavities in dentine are a 4W power setting and a working distance of lmm.

Epidemiological studies that conform to the highest possible standards of research design are required to provide good quality caries data necessary for disease surveillance, health needs assessments and the evaluation of oral health intervention strategies. Caries detection methods used in such studies should be suitable for “blinding” examiners collecting research data, to exposure or group allocation of participants in order to minimise the introduction of bias. The purpose of the studies in this thesis was therefore to assess the diagnostic performance and the pragmatic applicability of the use of intra-oral photographs as a caries detection method in epidemiological studies.Phase I compared the caries detection performance of intra-oral photographic assessments with visual examination and histology as the reference standard. Extracted teeth were assessed for caries using visual examination and assessments of photographs. The diagnostic decisions made were compared to histology. The visual examination and photographic assessments method had median sensitivity values of 65.6% and 81.3%; and median specificity values of 82.4% and 82.4% respectively. The two methods both had good intra- and inter-examiner reliability.The study in phase II compared the assessment of intra-oral photographs as means of detecting dental caries with visual dental examination in 5-year-olds and 10/11-year-olds in an epidemiological survey setting. 5-year-olds and 10-/11-year-olds were visually examined. Intra-oral photographs taken of the children’s teeth were also assessed by the same examiners. There was good intra-examiner reliability for both the visual and the photographic methods for all the examiners. However the photographic method was found to be lengthier than visual examination.Phase III compare caries data obtained from a full mouth visual examination with that obtained from eight, six and four intra-oral photographs of index teeth in two groups of children aged 5 years and 10/11 years. The views of users of the methods (examiners) as well as those on whom the methods were used (children) were also sought using focus group discussions. The examiners found it easier to make caries detection decisions on intra-oral photographs of primary teeth and they suggested that the use of other drying methods are required to improve the utility of photographic method. Generally, the intra-oral camera was well received by the children as a means of caries detection. Caries information obtained from the assessment of eight intra-oral photographs of the primary dentition was comparable to that from full mouth visual examination and may be used as an alternative caries detection method in situations where the visual examination method may not be applicable.