Dentistry usually encompasses very important practices related to the oral cavity. The most common treatments involve the dental surgery on the teeth as a treatment for dental caries. Decayed teeth can be filled with dental amalgam, dental composite, dental porcelain and precious or non-precious metals. Oral and maxillofacial surgery is a more specialized form of dental surgery. Dentists can prescribe medication, x-rays, and devices for home or in-office use. Many oral diseases (such as bilateral odontogenic keratocysts) and abnormalities (such as several unerupted teeth) can indicate systemic, neural, or other diseases. Most general practitioners of dentistry perform restorative, prosthetic, endodontic therapy, periodontal therapy, and exodontia, as well as performing examinations. Many general practitioners are comfortable treating complex cases, as well as placing implants and surgically extracting third molars (wisdom teeth). All dentists must achieve a certain degree of skill in various disciplines in order to graduate from dental school and become an accredited dentist.