According to the passage, gum disease ………

Gum disease and bad breath are two common dental problems. Normally, gum cells are replaced every few days and cleared from the mouth by saliva. However, when gum disease is present. the rate of cell replacement is increased and many dead cells remain in the mouth. As they decompose, these cells cause bad breath. Bacteria under the gum causes it to become swollen. These inflamed gums can bleed on tooth brushing. and this is usually the only sign of disease. Left untreated, the bacteria can destroy the bone that secures the teeth, leading to their loosening and eventual loss.