Treatment effects of the light-force chincup.
BACKGROUND
The objective of this study was to evaluate the effectiveness of the light-force chincup appliance in correcting the skeletal and dentoalveolar components of Class III malocclusion compared with an untreated Class III control group.


METHODS
The treatment sample consisted of 26 patients (11 boys, 15 girls) treated with the light-force chincup (125-250 g). The mean age at the start of treatment in the chincup group was 8.5 years, with posttreatment cephalograms taken on average 2.6 years later. The control group consisted of 20 subjects. The mean age at the start of observation for the control group (6 boys, 14 girls) was 7.3 years, and the mean time of observation was 2.4 years. Lateral cephalograms were analyzed with a specific tracing regimen at the 2 time points for both groups. Treatment outcome were determined. The treatment group subsequently was subdivided into those treated simultaneously with a quad-helix appliance and those with the chincup only. Mann-Whitney U tests for independent samples were performed to evaluate the differences between the treated and untreated groups at both time points, the changes between the 2 time points, and the differences between the groups treated with the quad-helix and chincup, and the chincup only.


RESULTS
The chincup sample showed no significant skeletal changes in the mandible in either the vertical or horizontal direction, except for a slight decrease in SNB angle and an increase in ANB angle. There were significant dentoalveolar changes, particularly uprighting of the mandibular incisors. Significant positive Class III treatment outcomes were recorded in the quad-helix group, including a decrease in mandibular length of 1.9 mm compared with the chincup group.


CONCLUSIONS
Fewer than 50% of the subjects treated with the chincup had favorable clinical outcomes. Correction of the initial Class III malocclusion occurred through significant dentoalveolar changes. The light-force chincup did not produce orthopedic changes in the mandible. Maxillary expansion with a quad-helix might aid in the correction of the Class III malocclusion in conjunction with the chincup.
Barrett
Aubrey A F
AAF
Postgraduate student, Graduate Orthodontic Program, University of Michigan, Ann Arbor, Michigan; private practice, San José, Calif.
Baccetti
Tiziano
T
Assistant professor, Department of Orthodontics, University of Florence, Florence, Italy; Thomas M. Graber Visiting Scholar, Department of Orthodontics and Pediatric Dentistry, School of Dentistry, University of Michigan, Ann Arbor. Electronic address: tbaccetti@unifi.it.
McNamara
James A
JA
Thomas M. and Doris Graber Endowed Professor of Dentistry, Department of Orthodontics and Pediatric Dentistry, School of Dentistry; professor, Cell and Developmental Biology, School of Medicine; research professor, Center for Human Growth and Development, University of Michigan, Ann Arbor; private practice, Ann Arbor, Mich.
D002508:Cephalometry / Q000706:statistics & numerical data; D002648:Child; D002680:Chin; D005115:Extraoral Traction Appliances; D005260:Female; D006801:Humans; D007180:Incisor / Q000503:physiopathology; D008297:Male; D008313:Malocclusion, Angle Class III / Q000628:therapy*; D008334:Mandible / Q000473:pathology; D009971:Orthodontics, Corrective / Q000295:instrumentation*; D018709:Statistics, Nonparametric