Effects of distal jet appliance for the first molar distalization on the second molar eruption

Dong Li, DDS, and Yu-Ming Bai, MS

Department of Orthodontics, College of Stomatology, The Fourth Military Medical University, Xi’an,
P. R. China

Purpose: The purpose of this study was to assess the effects of distal jet for the first molar distalization on the eruption of maxillary second molar.
Materials and Methods: The dental casts and cephalograms of 33 patients with class II malocclusion were analyzed. The group of distal jet appliance consisted of 18 patients with the second molars absent or partly erupted. And 15 patients with conventional orthodontics treatment (non-extraction) were adopted as the control. Nine linear and proportional, angular measurements were made. Statistical evaluation was conducted by Student’s t-test for paired data.
Results: There were significant changes in nine linear and proportional angular measurements of two groups (p<0.01). The mean mesiobuccal rotations of the second molars were 4.2°. The changes of m2-SN (before treatment 54.3°, after treatment 48.0°) and m2-Ptv (before treatment 12.8 mm, after treatment 9.7 mm) in the second molar region proved that both expansion and tipping occurred in the second molars.
Conclusion: The study proved that both mesiobuccal rotation and vestibular drift happened in the second molars when distal jet was used for first molar distalization. (Int Chin J Dent 2006; 6: 111-114.)

Key Words: distal jet, eruption, second molar.