Dental plaque bacteria have been linked to cardiovascular disease and mothers giving birth to pre-term low weight infants, but there is no conclusive evidence yet that periodontitis is a significant risk factor for either of these two conditions. Prevention
Toothpaste with pyrophosphates or zinc citrate has been shown to produce a statistically significant reduction in plaque accumulation, but the effect of zinc citrate is so modest that its clinical importance is questionable. Some calculus may form even without plaque deposits, by direct mineralisation of the pellicle. Calculus in other animals
Calculus formation in other animals is less well studied than in humans, but it is known to form in a wide range of species. Domestic pets, such as dogs and cats, frequently accumulate large calculus deposits. Animals with highly abrasive diets, such as ruminants and equids, rarely form thick deposits and instead tend to form thin calculus deposits that often have a metallic or opalescent sheen. In animals, calculus should not be confused with crown cementum, a layer of calcified dental tissue that encases the tooth root underneath the gingival margin and is gradually lost through periodontal disease. Archaeological significance
Dental calculus has been shown to contain well preserved microparticles, DNA and protein in archaeological samples. The information these molecules contain can reveal information about the oral microbiome of the host and the presence of pathogens. It is also possible to identify dietary sources as well as study dietary shifts and occasionally evidence of craft activities.
Sub-gingival calculus formation and chemical dissolution
Sub-gingival calculus is composed almost entirely of two components: fossilized anaerobic bacteria whose biological composition has been replaced by calcium phosphate salts, and calcium phosphate salts that have joined the fossilized bacteria in calculus formations. The initial attachment mechanism and the development of mature calculus formations are based on electrical charge. Unlike calcium phosphate, the primary component of teeth, calcium phosphate salts exist as electrically unstable ions. The following minerals are detectable in calculus by X-ray diffraction: brushite (CaHPO4 · 2 H2O), octacalcium phosphate (Ca8H2(PO4)6 · 5 H2O), magnesium-containing whitlockite (Ca9(Mg,Fe)(PO4)6(PO3OH)), and carbonate-containing hydroxyapatite (approximately Ca5(PO4)3OH but containing some carbonate).The reason fossilized bacteria are initially attracted to one part of the subgingival tooth surface over another is not fully understood; once the first layer is attached, ionized calculus components are naturally attracted to the same places due to electrical charge. The fossilized bacteria pile on top of one another, in a rather haphazard manner. All the while, free-floating ionic components fill in the gaps left by the fossilized bacteria. The resultant hardened structure can be compared to concrete; with the fossilized bacteria playing the role of aggregate, and the smaller calcium phosphate salts being the cement. The once purely electrical association of fossilized bacteria then becomes mechanical, with the introduction of free-floating calcium phosphate salts. The "hardened" calculus formations are at the heart of periodontal disease and treatment.