Advanced Dental Admission Test (ADAT)

Which microbe is associated with root surface caries?

1. A streptococcus mutans

2. A israelii

3. A staphylococcus aureus

4. A candida albicans

The correct answer is: A israelii

Root surface caries is primarily associated with specific types of microbes that thrive in the anaerobic and acidic environments characteristic of the root surface, particularly when the root surface is exposed due to periodontal disease. Among the microbes listed, Actinomyces israelii is known for its presence in dental plaque and its role in the initiation and progression of root surface caries. Actinomyces israelii is a gram-positive bacterium that commonly colonizes the oral cavity. It is particularly adept at adhering to tooth surfaces and is often implicated in the breakdown of the tooth structure, which leads to carious lesions. In the context of root surface caries, it is significant because it can invade the cementum layer of the tooth roots, where it produces acids that demineralize the tooth tissue, ultimately resulting in caries formation. While other microorganisms listed can be involved in various oral infections or conditions, their association with root surface caries is not as direct or notable as that of Actinomyces israelii. For example, Streptococcus mutans is more typically associated with caries on coronal surfaces, while Staphylococcus aureus and Candida albicans generally are not considered primary pathogens in the context of root surface caries.