Clinical application of QLF and DIAGNOdent : two new methods for quantification of dental caries

General aim: The general objective of this thesis was to evaluate the clinical performance of two new methods for quantification of dental caries - the Quantitative Light-induced Fluorescence method (QLF) and KaVo DIAGNOdent. Materials and methods: In Paper I, in vivo measurements with QLF on teeth scheduled for extraction, were compared with transverse microradiography (TMR), and tested for intra-operator reliability. In Paper II, the QLF method was applied to monitor active white spot lesions over a period of 6 months in a randomised, controlled study. In Paper IV, the QLF method was tested for intra- and inter-operator reliability in vivo for the capturing part as well as the image analysis part of the method. In Paper III, KaVo DIAGNOdent and QLF were validated with TMR and histology for mineral loss and lesion depth. In Paper V, DIAGNOdent readings of occlusal surfaces were compared with visual inspection, and bitewing radiography, before validation by assessment of lesion depth. In a second part of the study, DIAGNOdent was validated with QLF as reference standard for assessment of lesion depth on smooth OBS surfaces. Intra- and inter-operator reliability were tested in both parts of the study. Validation: In vitro, both QLF and DIAGNOdent showed good correlation with lesion depth on smooth surfaces, while the QLF method showed higher correlation with mineral loss. Sensitivity and specificity were excellent for QLF and good for DIAGNOdent. In vivo, DIAGNOdent showed low sensitivity for deep dentinal caries on occlusal surfaces when balanced to acceptable specificity. Validated with QLF as reference standard, DIAGNOdent readings of smooth surfaces showed a satisfactory correlation OBS on. Reliability tests on smooth surfaces showed excellent results for both the QLF method and DIAGNOdent in terms of inter- and intra-operator agreement. For occlusal surfaces, DIAGNOdent showed a very good intra-operator agreement, and a good inter-operator and inter-device agreement. Clinical application: In Paper M data obtained by the QLF method showed significant differences over time in the test group (PTR + fluoride varnish) as well as the control group (PTR) regarding lesion area and average change in fluorescence. There was also a significant intergroup difference regarding average change in fluorescence and a tendency towards intergroup difference for lesion area. Despite the fact that the QLF method consists of several steps, both the inter- and intra- operator reliability were excellent. Measurements with the DIAGNOdent (one-step system) are easier to perform, and for operator agreement the results for both methods were excellent. However, because of its closer correlation with mineral content, QLF is the preferred method for scientific purposes such as monitoring de- or remineralisation. Conclusions: 1) The Quantitative Light-induced Fluorescence method may be of value for longitudinal monitoring, e.g. for assessment of the effects of different caries preventive programmes and the method per se may further boost motivation and compliance by the subjects. 2) Under clinical conditions, the DIAGNOdent device showed excellent intra-operator agreement and good inter- operator agreement for measurements of carious lesions on smooth surfaces and good intra- and inter-operator agreement for lesions on occlusal surfaces. 3) With respect to clinical cut-off thresholds for dentinal caries on occlusal surfaces, no definite recommendations for DIAGNOdent could be made on the basis of data obtained in these studies