Primary bacteria found at the crown of the tooth are primarily what type?

• A. Anaerobic
• B. Spirochetes
• C. Micrococci
• D. Aerobic

Answer: (D)

The crown surface is exposed to ambient oxygen, so the bacteria that first colonize this area are those that tolerate or require oxygen. Early plaque organisms are primarily aerobic or facultative anaerobes, such as certain streptococci, which can grow in the presence of air. As plaque matures and depths increase, anaerobic bacteria become more prevalent in deeper, protected niches, but on the crown itself the dominant type is aerobic. Spirochetes and other strict anaerobes are more associated with subgingival areas and advanced disease, and micrococci are not the main early colonizers of the crown.