Abstract: Objective　To compare the forces on the upper and lower central incisors of bases made of different materials, self-curing resin materials and the thermoplastic materials, under the action of buccal multiple spring, hoping to choose proper materials to replace the bases made of self-curing resin and to solve the problem of anterior teeth inclination in patients treated with buccal multiloop appliance during the process of correcting Class Ⅲ malocclusion. Methods　According to voltage-force value relation, the voltage value could be converted into force value. The voltage on the incisors was measured by a thin film pressure sensor miniature force system when the buccal multiloop was opened for 2 mm, 4 mm, 6 mm, 8 mm, 10 mm respectively in the simulated closed position in vitro. Force values on the labial and lingual surfaces of the upper central incisors under the orthodontic force of different lengths of buccal multiloop springs were calculated and compared. Then the results were statistically analyzed. Results　With the increase of the length of buccal multiloop, the force values produced by the two kinds of bases on the labial surface of maxillary central incisors and the lingual surface of mandibular central incisors increased. When the buccal multiloop was opened to the same length, the labial force values of the thermoplastic material base on maxillary central incisors and the lingual force values of mandibular central incisors of that were less than those of the self-curing resin base(P<0.05). Conclusion　Compared with self-curing resin, the force value of the base made of the thermoplastic material on maxillary and mandibular central incisors is smaller, which can reduce the inclination of maxillary and mandibular central incisors and relieve the tooth effect.

Key words: Buccal Multiloop appliance, Self-curing resin, thermoplastic material, Thin Film Force Sensor