Abstract: The orthodontic appliance includes a spread plate for spreading location of right and left molars of an upper dentition portion by spreading right and left plate portions, and the right and left plate portions include plate body portions arranged respectively on the sides of the molars of the upper dentition portion and the engagement portions extending from the plate body portions to the positions each facing the vicinity of the front teeth of the upper dentition portion, and the engagement portions are configured to be engaged with the lower front teeth when the upper dentition portion and a lower dentition portion are engaged with each other.

Abstract: The orthodontic appliance includes a spread plate for spreading location of right and left molars of an upper dentition portion by spreading right and left plate portions, and the right and left plate portions include plate body portions arranged respectively on the sides of the molars of the upper dentition portion and the engagement portions extending from the plate body portions to the positions each facing the vicinity of the front teeth of the upper dentition portion, and the engagement portions are configured to be engaged with the lower front teeth when the upper dentition portion and a lower dentition portion are engaged with each other.

Abstract: [Problem] To provide an orthodontic appliance capable of correcting a dentition while spreading the dentition in the lateral direction, and adjusting a muscle function around an oral cavity. [Solution] A inner peripheral wall of an orthodontic appliance includes an upper wall and a lower wall, the upper wall and the lower wall include upper side surface portions and lower side surface portions approaching a base portion, respectively, each of the upper side surface portions has an upper inclined surface capable of being in contact with an upper dentition, and each of the lower side surface portions has a lower inclined surface capable of being in contact with a lower dentition.