Dental tartar is roughly 77% mineral by weight, with the rest made up of bacteria, proteins, and other organic material. It forms when the soft bacterial film on your teeth (plaque) absorbs mineral ions from your saliva and hardens into a crusty deposit that a toothbrush can no longer remove.
The Mineral Component
The bulk of tartar is inorganic mineral. Chemical analysis shows that calcium makes up about 34% and phosphorus about 19% of the mineral content, with smaller amounts of magnesium (0.9%), carbon dioxide (1.8%), and trace fluoride. These elements arrange themselves into three main crystal types, each accounting for roughly a third of the mineral phase: hydroxyapatite (the same crystal found in tooth enamel and bone), whitlockite, and octacalcium phosphate. All three appear in more than 80% of tartar samples. This dense mineral structure is what makes tartar feel like concrete on your teeth and why no amount of brushing will scrape it off once it has formed.
The Organic Matrix
The remaining 23% or so of tartar is organic material: dead and living bacteria, proteins from saliva, and remnants of food. Before tartar hardens, it starts as plaque, a biofilm containing an enormous diversity of microorganisms. Molecular analysis has identified over 600 bacterial species living in dental plaque, and roughly half of those species can’t even be grown in a lab. These microbes are embedded in a sticky scaffold of proteins and sugars produced partly by the bacteria themselves and partly by your own saliva.
When you eat sugary or starchy foods, acid-producing bacteria like mutans streptococci and lactobacilli thrive and lower the pH of the plaque. That acidic environment is what drives tooth decay. But the organic layer also plays a role in tartar formation: bacterial cell walls and salivary proteins serve as a scaffolding where minerals begin to crystallize. Once those minerals lock into place, the bacteria become entombed inside the hardened deposit, creating a rough surface that attracts even more plaque on top.
How Plaque Becomes Tartar
Mineralization can begin as early as one day after plaque forms on a tooth surface. Within about 12 days, a deposit typically reaches 60% to 90% of its final mineral content. The process works like this: saliva is supersaturated with calcium and phosphate ions. When plaque sits undisturbed on a tooth, those ions seep into the biofilm and begin forming tiny crystals. Over days, the crystals grow and merge until the once-soft plaque becomes rock-hard calculus.
Where tartar forms on the tooth matters, because the mineral source is different. Tartar above the gumline (supragingival calculus) draws its minerals from saliva. That’s why it tends to build up fastest on the inside surfaces of the lower front teeth and the outer surfaces of the upper molars, both of which sit right next to salivary gland openings. Tartar below the gumline (subgingival calculus) gets its minerals from crevicular fluid, the seepage that comes from the tissue surrounding the tooth root. Subgingival tartar is typically darker, harder, and more tightly bonded to the root surface.
Why Some People Build Tartar Faster
Not everyone accumulates tartar at the same rate, and the main reason comes down to saliva chemistry. Research measuring salivary calcium levels across groups with varying amounts of tartar found a strong positive correlation (0.639) between calcium concentration in saliva and the amount of calculus on teeth. People with the heaviest tartar deposits had salivary calcium levels nearly five times higher than those with little to no buildup (10.07 mg/dL versus 2.22 mg/dL). A protein called statherin, which normally keeps calcium dissolved in saliva and prevents premature crystallization, varies between individuals and may explain why some people’s saliva mineralizes plaque more aggressively than others.
Other factors play a role too. Alkaline saliva promotes crystal formation. Poor oral hygiene gives plaque more undisturbed time to mineralize. Smoking, dry mouth, and diet composition all shift the equation. But the calcium concentration in your saliva appears to be the single biggest variable.
What Tartar Does to Your Gums and Bone
Tartar itself isn’t just a cosmetic problem. Its rough, porous surface is an ideal habitat for bacteria, and when tartar extends below the gumline, those bacteria trigger an escalating immune response. The body sends inflammatory cells to the area, and those cells release signaling molecules that, over time, activate bone-resorbing cells called osteoclasts. In chronic periodontal disease, this cycle of bacterial irritation and immune overreaction slowly destroys the soft tissue and bone that hold teeth in place. The damage is irreversible: once alveolar bone is lost, it doesn’t grow back on its own.
Bacterial toxins from the plaque trapped within subgingival tartar are the primary trigger. They stimulate nearby bone cells to produce proteins that recruit and activate osteoclasts, tipping the normal balance between bone formation and bone breakdown. This is why tartar removal isn’t optional for long-term oral health. Leaving it in place keeps the inflammatory cycle running indefinitely.
Why You Can’t Remove Tartar at Home
Once plaque has mineralized, its crystal structure bonds tightly to the tooth surface. A toothbrush, floss, or even abrasive toothpaste can’t generate enough force to break those mineral bonds without damaging enamel. Professional removal uses one of two approaches: hand instruments (scalers and curettes) that physically chip the deposit away, or ultrasonic scalers that vibrate at high frequency. Ultrasonic tips work partly through direct contact and partly through cavitation, the formation and collapse of tiny bubbles in the water spray around the tip. Those collapsing bubbles generate enough localized force to disrupt both the calculus and the bacterial biofilm underneath, sometimes without the tip even touching the tooth surface directly.
The practical takeaway is straightforward. Brushing and flossing prevent plaque from mineralizing in the first place, but once tartar forms, only professional cleaning can remove it. Since mineralization can begin within 24 hours of plaque formation, consistent daily cleaning is the only reliable way to keep tartar from building up between dental visits.