RCT comparing maxillary molar anchorage loss using two retraction techniques

Objective: This pilot RCT investigated the relative effectiveness in anchorage conservation of the "en masse" and "two-step" retraction techniques during the treatment of maximum anchorage Angle Class I and Angle Class II malocclusions.

 Materials and Methods: 64 maximum anchorage growing patients (25 males and 39 females) age range 10.2 to 15.9 years were identified and randomized to two treatment groups: en masse retraction (n=32) and two-step retraction (n=32), stratified by sex and starting age.  Each patient was treated by a full-time clinic instructor experienced in the use of both retraction methods. All patients used headgear and most wore trans-palatal appliances. Pre-treatment and end-of-treatment lateral cephalograms were compared superimposed on anatomical best fit of palatal structures. Differences in maxillary anchorage loss were measured between the two treatment methods, between males and females, and between patients who differed in starting age.

Results: Average anchorage loss in the en masse group was slightly lower than in the two-step group (mean=-0.36 mm, 95% CI = -1.42, 0.71), demonstrating with high probability that the two-step procedure was not substantially better at anchorage conservation. Average anchorage loss for both treatment groups pooled (meanąsd) was 4.3ą2.1 mm n=63. Boys had significantly more anchorage loss than girls (mean difference = 1.3 mm, P<.05). Younger adolescents had significantly more anchorage loss than older adolescents (mean difference = 1.3 mm, P<.05).

Conclusion: In this RCT, average anchorage loss using en masse retraction was slightly lower than that for two-step retraction. Although the difference did not itself reach statistical significance, the closeness of the means for the two methods strongly contradicts the belief that two-step canine retraction is more effective in preventing clinically meaningful anchorage loss than en mass retraction. Male adolescents had significantly greater anchorage loss than female adolescents; younger adolescents had significantly greater anchorage loss than older adolescents.