What type of bacteria primarily causes green stains on teeth?

The primary bacteria responsible for the formation of green stains on teeth are chromogenic bacteria. These bacteria produce pigments, which can lead to discoloration of dental surfaces, particularly when they accumulate in areas where oral hygiene is inadequate. The green stains are often the result of specific types of chromogenic bacteria that thrive in the oral environment and are capable of producing colored compounds.

Understanding this, it becomes clear that while cocci bacteria, aerobic bacteria, and facultative bacteria play roles in oral health and dental conditions, they do not specifically relate to the green staining phenomenon as chromogenic bacteria do. The term "chromogenic" specifically refers to those capable of producing colorful pigments, which is central to the formation of these noticeable stains on teeth.