Analysis of bacterial viability and motility in dental calculus: a clinico-microbiological study.

Periodontitis is a chronic inflammatory process initiated by the plaque biofilm. This is mainly associated with development of destructive periodontal disease, leading to pocket formation, bone loss, and eventually tooth loss. Current understanding of initiation and progression of periodontal disease describes dental plaque to be the primary etiological factor. This biofilm is accompanied by the presence of calculus, which is virtually always covered with unmineralized plaque. Calculus is plaque that mineralizes to form calcified deposits. Although gingivitis can develop in the absence of supragingival calculus, it is not clear to what extent the presence of mineralized deposit enhances gingival inflammation. In the past 40 years, calculus has been deposed by plaque, and the hardened criminal has come to be viewed as a fossilized remnant of minor significance.

Regarding the significance of dental deposits, Schroeder summed up “Initial damage to the gingival margin is presumably due to enzymatic effects caused by the microorganisms of the plaque. This process is enhanced by the formation of supragingival dental calculus, which provides further retention and thus promotes new plaque accumulations”. Plaque induced chronic inflammation eventually results in formation of periodontal pockets in which sub gingival calculus is deposited. The latter is a secondary phenomenon; it is not a cause of pocket formation but a concomitant manifestation.

This subgingival dental calculus in turn favors and promotes the chronicity of the inflammation, and thus, contributes toward making it progressively worse. It has also been thought that calculus is plaque retentive and may impede natural and mechanical oral hygiene activities. It also may act as a reservoir for irritating substances such as endotoxins and bacterial antibodies.

About 20 percent of dental calculus is made of organic matrix, non-mineralized cavities containing micro-organisms, and extra cellular substance resembling that of the covering soft plaque that are found within the body of supragingival calculus. It is known that the environment within a biofilm is able to support viable bacterial communities through molecular diffusion of nutrients through channels and calculus can be permeated by substances such as endotoxins within 24 hours. The possibility therefore exists that a sustainable environment for oral bacteria may be found within the dental calculus and that such organisms may remain viable for some time.

The present study will be undertaken with the aim to investigate the viability of bacteria in dental calculus and to identify the same. The objectives will be to identify the bacterial morphotypes using gram staining and observe the motility of bacteria under dark field microscope.