Effect of protractor therapy on patients with Class III malocclusion

抄録

The protractor appliance is effective as an orthopedic device for early treatment during mixed dentition. We investigated the use of this appliance in 31 subjects, 12 males and 19 females between 9 and 17 years of age with Class III malocclusion. All subjects obtained relatively stable dental occlusion and a favorable soft tissue profile, resulting in no further need for orthognathic surgery. Pre‐ and post‐treatment lateral cephalograms were analyzed using the paired sample t‐test. The results showed both dentoalveolar and skeletal improvement. Both the forward bodily movement of the maxillary incisors and the retroclination of the mandibular incisors contributed to correction of the anterior crossbite. A significant increase in ANB contributed to the forward movement of point A, while the change in SNB was neglectable. Elongation of maxillary molars resulted in an apparent counterclockwise rotation of the occlusal plane, which is a mechanism for improving the molar relationship from Class III to Class I. Counterclockwise rotation of the occlusal plane and the forward movement of point A both increased Wits appraisal. Not only was the vertical dimension maintained, but also the facial profile was improved. This study demonstrates that protractor therapy, as a non‐invasive method, can have comprehensively favorable effects on the craniofacial complex and is applicable for treatment in adolescence. (J Osaka Dent Univ 2021; 55: 231‐238)