Further Studies in Caries and Fluorosis

  • Michael Mcgrady

Student thesis: Unknown


ABSTRACT of the thesis submitted by Michael Gerard McGrady for the Degree of Doctor of Philosophy entitled Further Studies in Caries and Fluorosis.The main drivers for this body of work were a systematic review on water fluoridation by the NHS Centre for Research Dissemination (known as the York Report) and a report by the Medical Research Council entitled "Water Fluoridation & Health". Both documents highlighted shortcomings in the evidence base on water fluoridation. Two major projects form the basis of this thesis in an attempt to address some of the issues raised. The first project in Chiang Mai, Thailand aimed to determine the ability of QLF to discriminate between populations with differing exposures to fluoride. Populations with differing exposures to fluoride were identified through the analysis of drinking water and cooking water. Subjects were examined for fluorosis with standardized photographs and QLF to evaluate software techniques for fluorescence image analysis. The results in Thailand demonstrated that QLF was able to discriminate between populations with differing exposures to fluoride in water to a similar degree to blinded, subjective clinical scoring. There was significant agreement between the two methods (ICC 0.65 Spearman's rho). However, confounding factors for QLF were found. The aim of the second project was to assess the use of blinded and objective methods for assessing caries and fluorosis in fluoridated Newcastle and non-fluoridated Manchester in northern England. This study involved clinical and intra-oral photographic caries examinations using ICDAS, together with standardized photography and QLF imaging for fluorosis examinations. The results in Newcastle and Manchester suggested that there were significantly lower levels of caries in the fluoridated population compared to the non-fluoridated population. For early caries (Newcastle mean DMFT 2.94[clinical]/2.51[photo], Manchester mean DMFT 4.48 [clinical]/3.44[photo]) and caries into dentine (Newcastle Mean DMFT 0.65[clinical]/0.58[photo], Manchester mean DMFT 1.07 [clinical]/0.98 [photo]). This was reflected as an increase in caries as the level of deprivation increased (confirmed through intra-oral photographic scoring). The reduction in caries levels was associated with increased levels of fluorosis in Newcastle. The prevalence of fluorosis from photographic scores in fluoridated Newcastle was 55%, in non-fluoridated Manchester it was 27%. In Newcastle, 48% of subjects had TF scores of 1 or 2 and 7.1% of subjects had TF scores of 3 or greater. QLF showed significant associations with the clinical scores for fluorosis (ICC 0.405 Kendall's tau) and suggested a fluorosis prevalence for TF 3 or greater of 19% in Newcastle and 10% in Manchester. The integration of technologies such as intra-oral photographs for blind caries scoring and QLF for the detection and objective quantification of fluorosis may still prove to be useful adjunctive tools when used alongside clinical indices. The data derived from the methodologies under investigation suggest a benefit in caries reduction from community water fluoridation and this may help to reduce inequalities in oral health by reducing the social gradient between deprivation and caries. August 2011
Date of Award31 Dec 2011
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorIain Pretty (Supervisor)


  • fluoride
  • QLF
  • water fluoridation
  • Caries
  • Fluorosis

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