Studies Related to the Prevention of Root Surface Caries

Root surface caries has been regarded as one of the problems of the future and recently has been given more attention. However, in the absence of an ideal and durable conservative treatment, the ideal solution for the problem would be prevention of the disease. Identifying the organisms associated with the initial lesion and enhancing the salivary remineralising effect upon the subsurface lesion via fluoride administration might be effective methods of arresting the disease and reducing its prevalence. In the experimental work reported in this thesis, an artificial caries system, capable of producing repeatedly root subsurface lesions with a hypermineralised surface overlying a lesion body, was developed. The remineralisation effect of a placebo and three different monofluorophosphate dentifrices on these lesions was investigated in situ using the single section technique and an intra-oral appliance. This system allowed the investigations to be carried out in the oral environment and eliminated the disadvantage of the control sample used by other techniques. Also the remineralisation effect of a placebo and three different monofluorophosphate solutions were investigated in vitro. A third study was concerned with identifying microorganisms associated with demineralisation of sound root surfaces and formation of the initial lesion. Microradiographic / microdensitometric methods were used to assess the mineral changes in the lesions and demineralisation of the sound root surfaces. The results of the in situ study indicated that significant remineralisation was attained when fluoridated compared to placebo dentifrices were used. In 66% of the subjects, maximum remineralisation was achieved when using 5000 ppm F- dentifrice and in 33% of the subjects, maximum remineralisation occurred when 2500 ppm F- was used. In addition, the results of the in vitro study were consistent with the results of the in situ study in that lesion remineralisation was significantly higher when treated with fluoridated than with placebo solutions. Actinomyces spp. were significantly associated with root surface demineralisation after three weeks' exposure to natural plaque. To the contrary of some published results Strep, mutans and Lactobacillus spp. were not significantly associated with demineralisation. Applying sugar to the plaque seemed to have little effect on the plaque composition or on sound root surface demineralisation. These results supported the theory that root surface and coronal caries are of different origins. In conclusion, tooth pastes with 1000 - 5000 ppm F-used twice daily could contribute remarkably to the prevention of root caries. Of further interest in this field of research, will be to assess remineralisation when the subsurface lesion is exposed more frequently to fluoridated dentifrices or solutions. Also, large scale microbiological experiments should be carried out to establish the microbial aetiology of the disease