Magister Scientiae Dentium - MSc(Dent) / The investigation was designed to evaluate the scoring systems of pitts (1984), and that of Murray and Majid(1978), when used to monitor caries progression in deciduous teeth. The evaluation.was based on the reproducibility and discrlininatory ability of the two systems. The Reproducibility Study was designed to compare the reproducibility of the two systems, and in addition, to illustrate, firstly the use of the subject as the sampling unit in measuring reproducibility, and secondly, a more sensitive method of measuring reproducibility when analysing caries progression data. The Progression Study was designed to discriminatory ability. In addition the compare use of the the effect on subject as the sampling unit in monitoring caries progression was illustrated in the analysis of this part of the investigation. A sub-sample of the posterior bitewing radiographs of 301, 5 year old children from a Duraphat clinical trial (Murray et al. 1977, Murray and Majid 1978) were re-examined. For the Reproducibility Study 150 sets of radiographs were examined a total of 4 times, (repeated examinations for each method). For the Progression Study three serial bitewing radiographs of 50 children were examined using the two methods. For the Reproducibility Study, Kendall's Tau-B was used as an approxlination of the weighted Kappa as a measure of reproducibility. While the pitts method appeared to be more reliable, the difference .between the tYK>methods was not significant( p~ 05). The surface cannot be used as an independent unit in measuring reproducibility. A method using the subject as the sampling unit was illustrated. Attention was drawn to the need to develop a measure of reproducibility for progression studies which would take into account the magnitude of the disagreement (instead of just disagreement) into the overall index of reproducibility. The use of weighted Kappa is suggested as a more appropriate measure of reproducibility. In the Progression Study Method 1 is more sensitive to the various stages of the disease process and provides a more complete overall picture of the carious process. The proportion of enamel lesions recorded for Method 1 were consistantly higher than that for Method 2. The behaviour of outer and inner enamel lesions differed considerably and Method 1 allowed the behaviour of these lesions to be considered separately. The progression rates were found to be faster with Method 2. With Method 1 30% of enamel lesions per subject had progressed to dentine or been filled 12 months later, the corresponding figure for Method 2 was 50%. Method 2 by excluding outer enamel lesions introduces two biases. The combination of these biases favour overestimating the proportion of lesions deemed to have progressed. The use of Method 2 may lead to the unnecessary loss of valuable data; more surfaces were excluded as being unreadable because of overlap. The average proportion of surfaces per subject recorded as unreadible due to overlap was 7% at baseline, 8% at 12 months and 8% at 24 months, the corresponding figures for Method 2 were 13%, 13% and 22% for Method 2. Method 1 thus appears to offer some advantages. The use of the subject as the sampling unit in analysing caries progression data offers a mnnber of advantages when canpared to the use of the surface as the sampling unit. The findings of the study indicate the proportions of high risk subjects (subjects in whom a large proportion of lesions progressed in a given time period) was low. With Method 1 in only 11% of the subjects did 80-100% of the enamel lesions progress after 12 months. The findings indicate that the Pitts system is the more useful scoring system in studies monitoring caries progression in deciduous teeth. / British Council