Identification of Yeast Species Isolated from Dental Plaque of Periodontitis Patients and Healthy Subjects Using TYI-S-33 Medium Yeast is a ubiquitous microorganism commonly found in various parts of the human body, including the oral cavity. In healthy individuals, they typically exist as commensals; however, under specific conditions, they can transition to a pathogenic state, contributing to the onset and progression of diseases such as periodontitis. This study aimed to compare the composition and density of yeast species in the subgingival dental plaque of periodontitis patients and healthy subjects. Subgingival dental plaque samples were collected from 15 periodontitis patients and 15 healthy subjects. The samples were cultured in TYI-S-33 medium, and 16 viable isolates were analysed. Species identification was conducted using MALDI-TOF mass spectrometry, and yeast density was estimated using the McFarland method. Six species of yeast were identified among the isolates. A comparative analysis revealed no statistically significant differences in yeast species composition and density between the two groups. These findings highlight the diversity, prevalence, and density of yeast species in the oral cavities of periodontitis patients compared to those of healthy subjects, although their specific role in the pathogenesis of periodontitis remains inconclusive. Future research should focus on exploring the interactions between yeasts and other components of the oral microbiome to better understand their role in oral health and disease progression.