Calculus on teeth is defined as:

Calculus on teeth, also known as tartar, is accurately defined as hard mineralized deposits that form on the surfaces of teeth. This mineralization occurs when plaque, which is a soft and sticky accumulation of bacteria, is not properly removed through regular brushing and flossing. Over time, the minerals from saliva crystallize within the plaque, transforming it into a hard substance that adheres closely to the tooth structure.

Understanding the nature of calculus is essential for dental professionals, as its presence can lead to various dental issues including gum disease. It is important to differentiate calculus from other forms of deposits or dental conditions, such as those listed in the other options. For example, soft deposits refer to plaque, tooth decay relates to the breakdown of enamel due to acid produced by bacteria, and stains left after polishing are often superficial and do not denote the hardened structure of calculus. Recognizing these distinctions helps in providing appropriate dental care and treatment.