The oral dentition is divided into 4 regions according to upper right, upper left, lower left and lower right. Upper right is divided into the first region, i.e. upper right central incisor is 11 teeth, and so on upper right second molar is 17 teeth, upper left central incisor is 21 teeth, upper left second molar is 27 teeth, lower left central incisor is 31 teeth, lower left second molar is 37 teeth, lower right central incisor is 41 teeth, lower right second molar is 47 teeth, etc. It is divided by 4 areas, which is helpful for the clinician to accurately locate the teeth during the treatment, and also to explain the patient’s condition to the patient, etc. The wisdom teeth are the third molars, also in order of analogy the upper right third molar is 18 teeth, the upper left third molar is 28 teeth. The lower left third molar is 38 teeth, the lower right third molar is 48 teeth, etc.