What Causes Tartar on teeth?

tartar on teeth

Tartar on teeth is the plaque that has undergone mineralization. It is a yellow calcified mass tightly bound to the surface of the teeth and prostheses such as dentures, bridges or implants. It is also known as dental calculus or calculus.

It is not necessary that every plaque deposit mineralizes but, all tartar on teeth is covered by bacterial plaque (dental plaque).

Tartar has a rough surface and is porous. For this reason, it is easily stained by smoking tobacco or dietary components. It also retains bacterial plaque and acts as a reservoir of toxins produced by bacteria.

Types of tartar on teeth

It is classified based on its location into two types. 

  • Supra-gingival tartar or calculus – forms on the teeth next to the gum-line. Due to its location, it is associated with tooth decay. Moreover, its extension under the gums leads to sub-gingival calculus formation.  
  • Sub-gingival tartar or calculus – forms below the gums, in a small space between gums and tooth. This space (gingival sulcus) is 2-3mm deep in a healthy tooth. This calculus is often brown or black in comparison to whitish-yellow supra-gingival calculus. The sub-gingival tartar is linked to gum recession and later tooth loss (periodontitis). 

Composition of tartar on teeth

Its organic or soft matrix is similar to plaque. The mineral content in tartar is somewhat similar to bone and other hard structures of the teeth. Supragingival and subgingival calculus are composed of 37% and 58% of minerals, respectively. Calcium and phosphate salts predominate in calculus.

How is tartar formed?

Calcification of plaque occurs by precipitation of mineral salts from saliva. Mineral deposition of bacterial plaque starts as early as 4-8 hours of plaque formation.

A dental plaque that is calcifying may become 50% mineralised by day 2. The plaque can concentrate enormous calcium (2 –20 times) than its level in saliva.

factors that causes tartar on teeth

Urea has a dual effect, it inhibits the metabolism and multiplication of bacteria in the saliva on the one hand, and on the other hand it indirectly affects neutralizing the acid.

Urea present in the saliva is similar to its level in the blood. Research suggests that patients with renal failure have a higher level of urea in saliva and this protects them from demineralization of teeth. 

  • The thickness velocity of salivary film: Research suggests that when salivary flow was unstimulated (at rest), the velocity of the salivary film at the level of the teeth fluctuates between about 0.8 mm/min (outer surface of upper front teeth) and 8.0 mm/min (inner surface of lower front teeth).

When salivary flow was stimulated (during eating), this is estimated to increase the velocity of the salivary film from 2 to 40 times, depending on the location in the mouth.

It is thus postulated that the slow movement of the salivary film when flow is unstimulated, allows time for the diffusion of acids from dental plaque and raises the pH of the plaque.

A 0.5 to 1 unit higher pH level in plaque than surrounding saliva leads to precipitation of calcium phosphate crystals.

These two phenomena explain why tartar frequently develops on the inner side of the lower front teeth and outer side of upper second molar, even in people with good oral hygiene, because the ducts of two major salivary pour calcium phosphate rich saliva in close proximity to these two sites. 

It also answers the frequently asked question why do i get tartar on my bottom teeth.

The earliest crystals form on the matrix (organic matrix of plaque) lying between the bacteria. These crystals act as seeds that grow and expand and later join with other growing crystals. 

As plaque thickens, the crystals then form on bacterial surfaces and at last within the bacteria in the deeper layers. This rapid crystallization is due to the supersaturation of ions within the plaque and slow diffusion of inhibitors (of calculus) into the biofilm.

Rate of tartar formation

The rate of formation and accumulation of tartar vary from person to person, in different teeth, and at different times in the same individual.

Based on differences in the rate of tartar formation, individuals may be classified as:

  • Heavy calculus formers (>1.5mm/tooth).
  • Moderate calculus formers (0.6-1.5mm/tooth).
  • Mild or non-calculus formers – (<0.5mm/ tooth).

The average daily deposition of tartar on teeth varies from 0.10% to 0.15% of dry weight.

Tartar formation continues till it attains its maximal levels in thickness by 10 weeks to 6 months. It may then be reduced by mechanical wear on food, cheeks, lips and tongue. This drop in the amount of calculus after the maximum accumulation is called the reversal phenomenon.

Who gets tartar frequently?

  • Higher levels of supra-gingival and sub-gingival calculus are observed in smokers. This can be due to the stimulatory effect on inflammation and variations in gum fluid production that leads to an increase in mineralization.
  • The presence of tartar can be a risk marker for mortality. High dental calculus deposits can be associated with premature death from cardiac arrest (infarction).

Role of saliva in calculus formation  

The contents and physical nature of saliva influence plaque and calculus formation. The formation of calculus is related to the mineralization of plaque by inorganic salts derived from saliva. These salts are readily incorporated into the plaque at higher (alkaline) pH.

The level of enzymes such as salivary proteases, lactate dehydrogenase, alkaline phosphatase or acid phosphatase elevate in saliva as a consequence of certain metabolic or systemic diseases.

These enzymes can lead to increased calculus formation. If a level of any enzyme or ion elevates or depresses in the blood it similarly affects the levels of the corresponding enzyme in the saliva as well. These enzymes can alter the pH of saliva and plaque and influence mineralization.

Saliva also contains crystal growth inhibitors like statherine and proline-rich peptides. Their absorption into the plaque can inhibit crystal growth within the calculus.


Tartar on teeth or dental calculus is a a yellow, calcified plaque tightly adherent to the surface of the teeth and other areas of the mouth. 

Mineralization of plaque occurs by precipitation of mineral salts from saliva predominantly calcium phosphate. The presence of urea in saliva and plaque and saliva thickness velocity enhance the formation of tartar on teeth. 

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