Abstract: During orthodontic treatment of over bite,the tip back bend on mandibular arch wires can make mandikular molars tipping distally while depressing mandibular incisors.The purpose of the present study was to handle the principle of occlusal force and occlusal curve to analyze the advantages and disadvantages resulted from this change in over bite treatment.The result showed that it was necessary to regulate the distal tipping force putting on mandibular molars during treatment for different types of over bite.

Key words: over bite, cephalometric radiograph, axis of tooth, occlusal curve