Tooth cavities extend through the tooth’s surface enamel and will increase in size unless they are closed off with fillings.
The dentist carefully numbs the your mouth before gently drilling around the tooth cavity in order to clean it out before applying a white composite filling which is a combination of quality materials or white mix into the cleaned out cavity. The composite (filling) begins as soft and then quickly hardens inside the cavity to now close off the exposed cavity.
Once the filling has set in the tooth, it can last for a very long time but will need replacing if they break or wear down.