Dental Calculus has been associated with periodontal disease for a long time but its exact role in relation to the aetiology has always been debated amongst researchers. One of the reasons for this is the inability to differentiate whether it is calculus or the overlying unmineralised plaque layer that is having an effect on the periodontal tissues. Calculus is regarded as a plaque retentive factor and contains porosities through which bacteria and noxious products can provoke inflammation. This thesis will explore what calculus is, its composition as well as how it attaches to the tooth surface and its role in periodontal diseases. Based on the studies and experiments that have been referenced in this thesis, calculus is considered to be a secondary factor which helps to propagate the periodontal disease cycle and worsen a pre-existing inflammatory state. Subgingival calculus production requires an increase in gingival crevicular fluid production to provide the source of minerals for calcification but this increased production can only happen when there is already a diseased state.