Ask a Hygienist: Plaque vs. Calculus

Dental Dictionary – Plaque and Calculus

by Laurena Marques, BSDH, RDH

Through years of discussions with patients about oral hygiene, I have come to realize that most people use the words plaque and calculus (or tartar) interchangeably. But in fact, they’re totally different! So let’s chat about the stuff that builds up on our teeth, why it’s relevant to oral hygiene, and how to keep it off of our teeth. Plus, who doesn’t love to talk about germs? (Okay, maybe most people don’t… we’re just nerds).

Plaque is the sticky, soft, film that we brush off with a toothbrush. Although it is difficult to see, under our magnifying glass it is usually a white substance with the consistency of cottage cheese. Plaque is what makes our teeth feel like a “sweater” in the morning before we brush our teeth. Plaque is a harmful biofilm that causes inflammation, gum disease, and cavities. The makeup of plaque is around 1000 microorganisms, including streptococcus mutans, a large contributor to tooth decay.  Plaque builds up on our teeth naturally with our diet and saliva and is exactly why we brush our teeth at least twice a day.

As plaque absorbs minerals from food and saliva, it begins to harden within as little as 48 hours, turning into a substance called calculus (sometimes referred to as tartar). Calculus is made up primarily of calcium phosphate deposits and is formed in incremental layers. Calculus varies in color- white, green from stain, or even dark/black deposits from iron (bleeding) in inflamed gums. How and why calculus forms has many variables including oral hygiene, the type of bacteria in your mouth, drugs, medications, and tobacco use. Calculus can no longer be removed with a toothbrush and can only be removed by a professional dental cleaning using specific dental scalers and ultrasonic instruments.

Our mouths alone contain over 700 species of microbes (not including what’s under our gums and the bacteria that make up plaque and calculus – another 1200 species). Some of these microbes are good, and some are bad. Your mouth is basically its own ecosystem. Oral bacteria and inflammation (bleeding gums) is related to a variety of systemic issues in our body such as heart infections, cardiovascular disease, pregnancy complications, pneumonia, and Alzheimer’s disease. It is important to keep a good balance of the good bacteria in your mouth through low-sugar diet, brushing twice a day, flossing (or using a water flosser), avoiding tobacco use, and of course, visiting your dental hygienist!


Cate, J. (2006) Biofilms, a new approach to the microbiology of dental plaque.  Journal of Odontology. 94: 1.

Dr. Tungs (2017) [Image] Germs. Retrieved from

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