Evaluation of the Jones jig appliance for distal molar movement

The purpose of this study was to determine the effects of the Jones jig appliance on distal movement of maxillary molars and reciprocal effects on premolars and maxillary incisors. Cephalometric radiographs before and after orthodontic treatment of 72 consecutively treated patients, 46 females and 26 males, were measured to define treatment changes attributed to the Jones jig. Comparative measurements were made on a matched sample of 35 patients (20 females and 15 males) treated with cervical headgear by the same clinician. Both series of patients were treated to correct an Angle Class II molar relationship. The molar correction in the Jones jig patients consisted primarily of molar distal movement. Dental, soft tissue, and skeletal changes were evaluated and compared for significant differences between techniques. The results from the Jones jig sample showed the mean maxillary first molar distal movement was 2.51 mm, with distal tipping of 7.53 degrees. The mean reciprocal mesial movement of the maxillary premolar was 2.0 mm, with mesial tipping of 4.76 degrees. The maxillary first molar extruded 0.14 mm; the maxillary premolar extruded 1.88 mm. The maxillary second molars were also moved distally 2.02 mm and tipped distally 7.89 degrees. The longitudinal assessment (initial to completion of orthodontic treatment) showed significant differences between the Jones jig sample and the cervical headgear sample for lower lip to E-line and SNA. The Jones jig sample showed a mean decrease in lower lip to E-line of 0.25 mm versus 1.20 mm (P < .0212) for the headgear sample. SNA decreased 0.40 degrees for the Jones jig sample versus 1.20 degrees (P < .0093) for the headgear sample. However, the Jones jig sample and cervical headgear sample did not show significant differences of the final position in either linear or angular measurements of the maxillary first molars and corresponding premolar-incisor anchor units. The Jones jig appliance demonstrated treatment results comparable with those of the sample treated with cervical headgear. The Jones jig sample demonstrated effective distal molar movement and maintenance of the Class I molar relationship. Advantages of the Jones jig include minimal dependence on patient compliance, ease of fabrication, and ease of buccal force application.