When decay rots away enamel, the resulting space is called a cavity. Left untreated, the decay will eventually cause extensive damage to the tooth, and potentially cause the root to be infected. However, if the cavity is caught early, your dentist can treat it with a simple filling, typically in one appointment.  Your dentist will first apply a local anesthetic, then use a drill or laser to remove the decay. Then they will apply a filling to prevent further decay, and to prevent the sensitive inner layers of the tooth from cold, heat or pressure. The filling is applied in layers and hardened with a special light. The final layers are shaped and polished to restore the tooth’s appearance and function.