Tooth enamel is hard yet porous.
Plaque on the surface of your teeth can produce acids that seep into the pores (rods) of the enamel and break down its internal structure.
This process, called demineralization can create a weak spot on the surface of the tooth that may become a cavity if left untreated.
Decay often begins on biting surfaces, between the teeth, on exposed roots, and around existing fillings.
Untreated, decay spreads into the tooth and can destroy the tooth structure.
Decay enters and infects the pulp.