|SECTION IX||THE INFLUENCE OF TOOTH ANATOMY ON PERIODONTAL INSTRUMENTATION, ORAL HYGIENE INSTRUCTION, AND PERIODONTAL MAINTENANCE|
Bacterial plaque that has just formed can easily be removed from accessible crown and root surfaces with a toothbrush and dental floss. However, if it is not removed frequently, it can calcify to form a hard, complex mineral layer called dental calculus (also called tartar) that firmly attaches to the tooth. In the supragingival environment (coronal to the gingival margin), saliva is the calcium source forming a yellow-white mineralized deposit on the teeth (Fig. 7-40).
In the subgingival environment, products from blood and tissue fluids contribute to the calcification process and the deposits are dark brown (Fig. 7-41). It is the job of the dental professional to remove these calcified deposits, both supragingivally and subgingivally, and to teach patients how to prevent formation of these deposits by using excellent oral hygiene techniques.
CALCULUS ON THE ANATOMIC CROWN: The objective of instrumentation of the anatomical crown (called a dental prophylaxis) is to use specifically designed dental instruments (such as scalers [SKAY lerz] and curettes [kyoo RETS]) to remove dental calculus, bacterial plaque, and stain that form on tooth surfaces. Supragingival calculus that forms on the anatomic crown of the tooth is easier to remove than subgingival deposits on roots for several reasons. First, hard deposits on crown surfaces are more visible and are readily accessible when using dental instruments. Crown surfaces where calculus forms near the gingiva are mostly convex, which are easier to clean than the complex contours of roots, especially those on posterior teeth that are multirooted. Finally, crowns are covered with enamel that is the hardest substance in the body (95% calcified). Enamel is nonporous, so damage or removal of this tissue during instrumentation is not as likely as removal of cementum that is much less hard (less than about 65% calcified) and more porous.
SUBGINGIVAL CALCULUS: When periodontal disease progresses to a point where there is attachment loss, the normal insertion of connective tissue fibers into cementum is lost. In this subgingival environment, bacteria and their products, including plaque, dental calculus, and bacterial products, absorb into irregularities on the root surface and hold onto the biofilm, increasing the chance for plaque retention and periodontal disease activity. Loss of periodontal support of the bone and ligament exposes complex root surfaces, creating a challenge for dental professionals to clean (instrument) and for patients to maintain. Areas of deep