The invention concerns an orthodontic appliance made of elastic material and comprising arch- shaped upper and lower concaves (10, 20) for teeth of upper and lower jaw, the concaves (10, 20) being separated by an occlusally extending arch- shaped isthmus (30) and comprising inner (11, 21) and outer walls (12, 22) extending vertically from the edges of the isthmus (30). The appliance includes a volume (40) within the frontal section of the arch-shaped isthmus (30) of material harder than said elastic material and extending vertically in the isthmus (30) so as to form at least one section of a surface of the isthmus (30), so as to make up a biting surface (41, 42) on the upper side and the lower side of the isthmus (30).
