Microbial Analysis of Carious Root Lesions Compared to Healthy Controls in Geriatric Patients

Objectives: This study aims to identify bacteria associated with active root caries in geriatric patients compared to plaque samples from non-carious contralateral root surfaces in the same patient to determine whether levels of bacterial species identified are the same or vary significantly in each site. Previous studies have found that Streptococcus mutans, Lactobacillus species and Actinomyces species can be associated with root caries in geriatric patients. We will determine if these species, along with additional species, are present in higher concentrations on carious root surfaces.
Methods: This study focuses on supragingival plaque associated with root caries. Twenty patients, 65 years and older, with root caries will be selected as participants. Supragingival plaque was collected using a sterile curette from both a carious root and a healthy contralateral root surface to determine whether there are distinct bacteria in the two samples. Plaque samples were placed in a 2ml tube of sterile PBS (buffer) with 10% glycerol (a cryoprotective agent) for storage. Bacteria were lysed and DNA purified using a Qiagen Blood and Tissue DNA purification kit. Purified DNA was quantified and amplified using PCR primers specific for selected organisms of interest including S. mutans, Actinomyces species and Lactobacillus species. Levels of each species were quantified using Real-Time PCR. Results between carious and non-carious plaque samples were analyzed to determine differences in bacterial colonization between the two groups.
Results: Early results with 16 plaque samples suggest high levels of Actinomyces (greater than 10% of total colonization) can result in root caries and that a combination of more modestly increased levels of both Actinomyces and S.mutans at a single site relative to non-carious controls may lead to root caries.
Conclusions: Our analyses suggest a threshold may exist for certain bacterial species or combinations of species in establishing carious root lesions in geriatric patients.