Relationships between yeasts and primary root-caries lesions. David Beighton' and Edward Lynch^ 'Oral Microbiology. RCS Department of Dental Sciences, Faculty of Clinical Dentistry. KCSMD, London, UK; -Department of Conservative Dentistry, The London Hospital Medical College, London UK, A total of 447 primary root-caries lesions from 169 dental patients was studied to determine the relationships between their clinical severity and the number and frequency of isolation of yeasts. Yeasts were isolated more frequently from soft lesions, from lesions at the gingival margin and from lesions deemed to require restoration. These associations may be due to the aciduricity and acido- genicity of yeasts but the relatively low numbers found do not support a pathogenic role for yeasts in the aetiology of root caries: at best they may be marker organisms of the most severe disease. Key words: Primary root-caries lesions, yeasts, diagnosis, gerodontology Gerodontology 1993; 10(2): 105-108 Introduction Primary root caries is a growing clinical problem, especially amongst the population of elderly people whose numbers, in industrialised countries, are rapidly increasing. The dental health status of the elderly is improving due to the provision of special- ist dental care, the wider availability of dental health education, growing dental awareness and the wide- spread use of fluoride-containing toothpastes. There- fore the number of elderly retaining some or most of their natural teeth is significantly greater than only a few years ago and will continue to grow in tbe coming decades'. The consequence of these improve- ments is that the number of elderly people, and teeth, at nsk of root caries is increasing so that amongst dentate elderly in excess of 80 percent may exhibit a history of root caries^'^. In order to better understand the aetiology and progression of root caries it is necessary to under- stand the microbial changes that take place during lesion formation and progression. We have previ- ously reported that salivary levels of yeasts are significantly associated with the number of active primary root-caries lesions^ Such associations were stronger than for lactobacilli and mutans strepto- cocci. However we have little knowledge of the relationships between the isolation of yeasts and the severity or treatment needs of primary root-caries lesions. Therefore we have studied primary root- caries lesions with a range of clinical presentations to determine the relationships between the number and frequency of isolation of yeasts and tbe clinical appearance of primary root-caries lesions. Materials and methods Patients Patients with a history of root caries and attending the Department of Conservative Dentistry, The London Hospital Medical College for treatment were enrolled in this study. The total number of patients included in the study was 169 with a mean age (±SD) of 55.4 ± 14 years. Clinical characterisation of lesions The criteria for the clinical diagnosis of the lesions has been previously reported-. Briefly, lesion texture, perceived treatment need and the vertical and hori- zontal dimensions, depth of cavitation and distance of the lower border of the lesion from the gingival margin were measured to the nearest millimetre The Gerodontology Association 1993 Volume 10, No.2