Tartar above the gum line is referred to as supragingival tartar; tartar below the gum line is referred to as subgingival tartar.
Dental Tartar is comprised almost entirely of Calcium Phosphate Salt, or the ionic derivative of Calcium Phosphate; the basic component of tooth material. Unlike Calcium Phosphate, Calcium Phosphate “Salt” has lost two electrons; thus making it a positive ion, which is electrically unstable. This transformation is not uncommon in the natural world, and can easily be compared to Insoluble Calcium Carbonate, which is the primary component in lime deposits which stick to water pipes, faucets and kitchen appliances.
As mentioned above, the smaller components of dental tartar are actually fossilized bacterium.
As bacteria multiply in the mouth, which happens constantly, they form plaque communities that feed off of nutrients left behind after eating. This is primarily the case in supragingival, or above the gum line plaque.
Subgingival, or below the gum line plaque, is similar except the deeper the plaque formations are in a given periodontal pocket, the more they contain complex biofilms. These biofilms contain anaerobic bacteria which elicit an inflammatory response via inflammatory mediators - which contains harmful enzymes which cause bone and tissue destruction.
In both cases, the inner-most bacteria in plaque formations are starved of their food source and die. Because of a preponderance of Calcium Phosphate Salt in saliva, these dead bacteria fossilize; and their biologic composition is replaced by Calcium Phosphate Salt. What remains of deceased bacilli is a solid piece of electrically unstable Calcium Phosphate Salt of the original shape and size of the dead bacilli.
Fossilized ionic bacteria floating in dental plaque are electrically unstable and are attracted to oppositely charged material, such as tooth surfaces. This electrostatic attraction causes them to “land” on the tooth surface and “stick.” Their electrical charge remains unsatisfied, as no electron transfer is possible due to their ionic structure. To simplify this, one may compare this to “static cling” as is common in everyday life with clothing, toy balloons and the like.
So the initial attachment of tartar to tooth surfaces in tenuous at best. This is soon replaced, however, by a much more mechanical attachment in some tooth regions.
Where ever tartar initially adheres, it is grown by an endless supply of new fossilized bacteria, which pile on due to the same electrostatic attractions. These are the “bricks” of tartar formations. The “mortar” is provided by and endless supply of free-floating Calcium Phosphate Salt, which fill in some micro-spaces in the tartar accumulations and provide extra strength and “hardness.”
Depending on how porous a particular tooth surface is, tartar attachment varies in its ability to adhere to a surface. Well above the gum line at the enamel region, tartar has a difficult time seriously attaching to the tooth surface. Any dental hygienist can attest to the ease of tartar removal in this region. As tartar forms below the enamel, where tooth surfaces are microscopically porous and rough, tartar gets a foothold just underneath the tooth surface on the cementum and dentin. These formations are frequently described as “tenacious” and are much more difficult to remove by conventional means.
The dissolution of calculus is a painless and more effective approach to tartar removal both above as well as below the gum line.