Which stain has a definitive association with the use of marijuana?

The association of green stain with the use of marijuana is linked to the chromogenic bacteria that proliferate in the presence of certain substances found in marijuana. When marijuana is smoked, it can create an environment in the mouth conducive to the growth of these bacteria, which subsequently produce pigments resulting in the formation of green stains on the teeth. This type of stain is typically localized and can often be found along the gingival margin.

In contrast, other stains listed do not have direct associations with marijuana use. Yellow stains are commonly seen but are more related to dietary factors and personal hygiene rather than specific substances. Black line stains are typically associated with excellent oral hygiene and certain dietary habits, while chlorhexidine stains are a result of the use of chlorhexidine mouth rinses and are not related to marijuana consumption. Thus, the evidence and research indicate that the green stain bears a unique connection to marijuana use due to its specific etiology and the conditions it creates in the oral environment.