Tooth decay is a progressive disease resulting from the interaction of bacteria that naturally occur on the teeth and sugars in the everyday diet. Sugars are consumed by bacteria, causing production of acids that break down the minerals in the teeth, forming a cavity. Dentists remove the decay and fill the tooth using a variety of fillings, restoring the tooth to a healthy state. Nerve damage can result from severe decay and may require root canal treatment and a porcelain crown. Avoiding unnecessary decay simply requires strict adherence to a dental hygiene regimen: brushing and flossing twice a day, regular dental check-ups, diet control and fluoride treatment. Practicing good hygiene avoids unhealthy teeth and costly treatment.