Co-infection with Cbp⁺ Streptococcus mutans and Candida albicans is associated with root caries in older adults

Background: Gingival recession increases with age, exposing root surfaces and raising susceptibility to root caries. As the global population ages, root caries prevalence is expected to rise, underscoring the need to better understand its risk factors. Objective: To investigate the association between co-infection with Cbp⁺ Streptococcus mutans and Candida albicans and root caries in older adults with gingival recession, while characterizing the root plaque microbiome and evaluating multifactorial risk factors. Design: This cross-sectional study included 117 adults ≥65 years; 56 with root caries and 61 without. Saliva and site-specific supragingival plaque samples were collected to assess Mutans streptococci and Candida spp., along with microbiome composition. Demographic, behavioral, biological, dental, and medical factors were also evaluated. Results: Participants with root caries had higher salivary levels of Mutans streptococci and Candida spp. (p = 0.0122 and p = 0.0013). Co-infection with Cbp⁺ S. mutans and C. albicans was significantly associated with root caries (p = 0.0003). Microbiome analysis showed enrichment of Capnocytophaga leadbetteri in diseased root surfaces. Individuals with root caries were more likely to report xerostomia and less likely to use an electric toothbrush or floss daily. Conclusions: These findings highlight microbial and behavioral factors associated with root caries, offering insights into potential prevention and management strategies.