I have a black line between my front two lower teeth. is this black a build up of plaque or could it be something else?

Calculus: Most likely stained calculus (tartar) formed behind and in between the teeth. Could be decay on each tooth surface facing the line, but less likely. Get in for the cleaning and get it checked out. Good Luck.

Something Else: Plaque isn't black. Have your dentist take a look.

See dentist: See your dentist, this may be a buildup of calculus, that needs to be removed by your dentist or hygienist. See your dentist for a definitive diagnosis and keep recall visits as prescribed by your dentist.

Stains/Tartar/Decay: 1) See your dentist. 2) Xray, clinical exam to rule out decay or tartar/calculus buildup. If it is decay or calculus buildup, then it should be taken care of ASAP as it could lead to eventual tooth/bone loss. If it is staining, get it cleaned off and try rinsing with water immediately after you eat/drink anything colored. Flossing helps too.

Needs photo to eval: Black line in-between teeth can be because of multiple reasons like smoking or tobacco use, arrested decay, irregular flossing habits, soy sauce or overuse of vinegar and other products. Needs intraoral photo to evaluate in depth.

Need examination: Black line may be discolored tarter, stained enamel, decay, or other problem. Please call your Dentist now. Sounds like you are overdue for an examination. Please call now before your manageable problem becomes unmanageable.

Dental visit: Sounds like either staining or old calculus. See a dentist to evaluate and treat