Final answer:
Two occurrences on a tooth's crown are tartar formation and tooth decay. Tartar is hardened plaque, while decay is enamel erosion by acids from bacterial metabolism. Regular dental care can prevent and identify these issues early.
Step-by-step explanation:
Regarding what two things can occur on the crown that is flat, we are likely discussing dental health. Two common occurrences on the flat surface of a tooth's crown are the buildup of tartar (dental calculus) and the presence of tooth decay or cavities. Tartar is a hard deposit that forms on teeth when plaque, a sticky film of bacteria, calcifies. Tooth decay is the result of bacterial plaque metabolizing sugars and producing acids that erode the enamel of the tooth.
In dental X-rays, tooth decay may present as a dark area indicating where the tooth structure has been undermined by decay. Consequently, dental procedures often involve removing the decayed area and filling it to restore the tooth's integrity. Preventative measures include maintaining good oral hygiene and regular dental check-ups to minimize plaque buildup and identify decay early on.