Randomized clinical trial comparing control of maxillary anchorage with 2 retraction techniques.
BACKGROUND
The objective of this pilot randomized clinical trial was to investigate the relative effectiveness of anchorage conservation of en-masse and 2-step retraction techniques during maximum anchorage treatment in patients with Angle Class I and Class II malocclusions.


METHODS
Sixty-four growing subjects (25 boys, 39 girls; 10.2-15.9 years old) who required maximum anchorage were randomized to 2 treatment techniques: en-masse retraction (n = 32) and 2-step retraction (n = 32); the groups were stratified by sex and starting age. Each patient was treated by a full-time clinic instructor experienced in the use of both retraction techniques at the orthodontic clinic of Peking University School of Stomatology in China. All patients used headgear, and most had transpalatal appliances. Lateral cephalograms taken before treatment and at the end of treatment were used to evaluate treatment-associated changes. Differences in maxillary molar mesial displacement and maxillary incisor retraction were measured with the before and after treatment tracings superimposed on the anatomic best fit of the palatal structures. Differences in mesial displacement of the maxillary first molar were compared between the 2 treatment techniques, between sexes, and between different starting-age groups.


RESULTS
Average mesial displacement of the maxillary first molar was slightly less in the en-masse group than in the 2-step group (mean, -0.36 mm; 95% CI, -1.42 to 0.71 mm). The average mesial displacement of the maxillary first molar for both treatment groups pooled (n = 63, because 1 patient was lost to follow-up) was 4.3 ± 2.1 mm (mean ± standard deviation). Boys had significantly more mesial displacement than girls (mean difference, 1.3 mm; P <0.03). Younger adolescents had significantly more mesial displacement than older adolescents (mean difference, 1.3 mm; P <0.02).


CONCLUSIONS
Average mesial displacement of the maxillary first molar with 2-step retraction was slightly greater than that for en-masse retraction, but the difference did not reach statistical significance. This finding appears to contradict the belief of many clinicians that 2-step canine retraction is more effective than en-masse retraction in preventing clinically meaningful anchorage loss.
Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, China.
Tian-Min
TM
Xu
Xiaoyun
X
Zhang
Hee Soo
HS
Oh
Robert L
RL
Boyd
Edward L
EL
Korn
Sheldon
S
Baumrind
D000293:Adolescent; D000367:Age Factors; D002508:Cephalometry / Q000379:methods; D002648:Child; D003481:Cuspid / Q000473:pathology; D005115:Extraoral Traction Appliances; D005240:Feasibility Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007180:Incisor / Q000473:pathology; D008297:Male; D008311:Malocclusion, Angle Class I / Q000628:therapy*; D008312:Malocclusion, Angle Class II / Q000628:therapy*; D008437:Maxilla / Q000473:pathology; D008963:Molar / Q000473:pathology; D052280:Orthodontic Anchorage Procedures / Q000379:methods*; D016382:Orthodontic Appliance Design; D019516:Orthodontic Space Closure / Q000379:methods; D010865:Pilot Projects; D011627:Puberty; D012737:Sex Factors; D014087:Tooth Movement Techniques / Q000295:instrumentation / Q000379:methods*; D016896:Treatment Outcome