What material can become impregnated with calculus and contaminating bacteria that root planning aims to remove?

Cementum is the correct answer because it is a specialized calcified tissue that covers the roots of teeth. During periodontal disease, the cementum can become rough and porous, providing a surface where calculus (tartar) and bacteria can easily adhere and accumulate. Root planing is a therapeutic procedure aimed at smoothing the root surfaces by removing this calculus along with any associated plaque and bacteria. This helps to facilitate healing and improve the gum tissue’s health.

Both dentin and enamel are also components of the tooth but do not typically serve as primary sites for calculus accumulation in the same way that cementum does. Dentin, which is under the enamel and cementum, is not exposed to the same external factors that promote bacterial attachment. Enamel, the outer layer of the tooth, is much more resistant to demineralization and bacterial adherence due to its smooth, hard surface. Gingiva, while it can be inflamed and influenced by periodontal disease, does not become impregnated with calculus itself, but rather reacts to the presence of calculus on the surfaces of the roots and other hard tissues.