PROBLEM TO BE SOLVED: To provide a guide instrument for using a dental cutting apparatus, capable of preparing for orthodontics at home as well as at a dental clinic by easily expanding gaps between teeth at equal intervals.SOLUTION: A guide instrument includes a mouth piece 200 formed as an instrument body, for covering a dental arch A of a patient desiring to have the orthodontics. Teeth parts 201 having shapes corresponding to respective teeth constituting the dental arch A are formed on the mouth piece 200. The mouth piece 200 includes a notch part 202 for guiding a dental cutting apparatus, so as to be functioned as the guide instrument. When the mouth piece 200 is used, the notch part 202 for guiding the dental cutting apparatus is formed so as to infallibly specify an interdentium S1 to be cut, when the interdentium is cut by the dental cutting apparatus.SELECTED DRAWING: Figure 3
