OBJECTIVETo evaluate the effect of the preadjusted appliance (Z1 appliance) based on Chinese normal occlusion.

METHODSThirty non-extraction patients were treated with Z1 appliance. No wire bending was made during treatment. The results of these 30 cases had been evaluated by five senior orthodontists. Models were analysed quantitatively to testify and evaluate the efficiency of the appliance.

RESULTSThe average score for post-treatment models was 91.2 (total score was 100). The model measurements indicated that average projective distance on occlusal plane between proximal contact points of adjacent teeth was less than 0.3 mm, which demonstrated good alignment. The prominence of crowns was almost coincident with the data of Chinese normal occlusion. For the average tip of most teeth, there was no statistical difference between the study group and the normal control group. The crown torque variation tendency from anterior to posterior was similar to that in the subjects with normal occlusion. However, the cases treated with Z1 appliance achieved more negative torque in the lower posterior segment.

CONCLUSIONSThe result of the non-extraction patients treated with Z1 appliance was quite satisfied. Wire bending could be reduced during treatment. It was necessary to adjust the crown torque values for lower posterior teeth.