Final answer:
Tooth substance wearing away on the crowns of teeth is indicative of dental caries, also known as cavities.
Step-by-step explanation:
Tooth substance wearing away due to a mechanical process on the crown of teeth is indicative of dental caries, also known as cavities. Dental caries is caused by colonies of bacteria that release acids, which degrade the calcium crystals of the enamel. If untreated, the infection can spread to deeper tissues or the bloodstream. Good oral hygiene is crucial to prevent dental caries.