A variety of procedures occur in the dental chair for patients receiving preventive treatment, regardless of age. The dental exam itself is a form of prevention, as the purpose of the appointment is to detect the potential for dental decay, both during the oral exam and upon reading any dental images (x-rays) taken. Once the exam is done, the dentist can then recommend that the patient have his or her teeth cleaned, which is helpful in the prevention of cavities and gum disease. Teeth cleaning (also known as prophylaxis, literally a preventive treatment of a disease) is a procedure for the removal of tartar (mineralized plaque) that may develop even with careful brushing and flossing, especially in areas that are difficult to reach in routine toothbrushing. It is often done by a dental hygienist. Professional cleaning includes tooth scaling and tooth polishing and debridement if too much tartar has accumulated. This involves the use of various instruments or devices to loosen and remove deposits from the teeth. At least two professional dental cleanings are recommended a year for good preventative care.