Cavities occur due to a large amount of dental plaque and tartar on the teeth, which erodes the teeth over time, causing damage to the enamel and dentin. This results in the appearance of black spots, black patches, and cavities. However, cavities are not contagious because there are always a large number of bacteria in the mouth due to eating and other reasons, so it is important to develop good brushing habits and the correct technique. Although brushing can remove some dental plaque, its effect is limited. It is best to undergo dental and gum cleaning treatments to significantly improve the removal of dental plaque and eliminate the harm of cavities to the human body.