Bacteria Found in Root Caries: Common Culprits and New Associations

Park, Seon Gyeong, Michelle Szewczyk, Sumita Sam, Hina Qadir, Jamal Alhabeil, John Palanci, and Eric Krukonis

Objectives: This study identified bacteria associated with root caries in geriatric patients. Previous studies have found Streptococcus mutans, Lactobacillus species and Actinomyces species can be associated with root caries. We determined whether these species, along with four additional species, Streptococcus sanguinis, Veillonella parvula, Olsenella species and Selenomonas species, are present in higher concentrations on carious root surfaces compared to healthy control teeth.

Methods: Seven patients, 65 years and older, with root caries were recruited. Supragingival plaque was collected from both a carious root and a healthy contralateral root surface from the same patient. Plaque samples were placed in sterile buffered-saline with 10% glycerol for storage. Bacteria were lysed, DNA purified using a Qiagen DNA purification kit. DNA was then amplified using PCR primers specific for selected organisms. Levels of each species were quantified using Real-Time PCR. Results between paired carious and non-carious plaque samples were statistically analyzed to determine whether differences in bacterial colonization between the two groups were significant.

Results: Results with 14 pairs of plaque samples suggest high levels of S. mutans or Actinomyces can result in root caries or that a combination of more modestly increased levels of both S. mutans and Actinomyces at a single site may lead to root caries. A few carious teeth also had increased levels of Selemonomas and/or Olsenella. There was no consistent inverse correlation between S. sanguinis colonization and S. mutans colonization. Finally, elevated levels of V. parvula correlated with increased S. mutans and caries in several cases. V. parvula also had the most consistent association with root caries.

Conclusions: Our analyses indicate S. mutans and Actinomyces species are major contributors to root caries and Olsenella and Selenomonas species may play a minor role. We found two cases where increased colonization by Lactobacillus were associated with root caries, but in both cases the levels of Lactobacillus were low. Based on our findings, S. sanguinis does not appear to compete with S. mutans for colonization on root surfaces. Finally, Veillonella was the most informative of our species in predicting caries. In 8 of 9 cases where increased levels of V. parvula were detected, the teeth were carious.