An interventional study of Combined buccal and palatal distalizing force and Buccal distalizing force in Malocclusion and Tooth Movement, sponsored by Atlas University. Completed at 1 site in Turkey (Türkiye). Open to participants aged 12 Years to 18 Years. Per ClinicalTrials.gov, last updated 2026-10-07.
Sponsored by Atlas University · Not applicable, Interventional, and Treatment
In orthodontic treatment involving extraction of the maxillary first premolars, the canine is distalized into the extraction space using sliding mechanics. Because the retraction force is applied at bracket level and therefore at a distance from the centre of resistance of the tooth, the canine tends to rotate distopalatally and to tip in the sagittal plane instead of translating bodily. These side effects lengthen treatment and increase the load on the posterior anchorage teeth.
Power arms are used to bring the line of action of the force closer to the centre of resistance. In addition, because the centre of resistance of the maxillary canine lies palatal to the mid-buccolingual axis of the crown, a force applied from the palatal surface generates a rotational moment opposite in direction to that produced by a buccal force.
This trial tested whether dividing a constant total distalizing force between the buccal and the palatal surfaces of the canine, so that the two rotational moments oppose one another, produces a more bodily canine movement than applying the whole force from the buccal side alone.
The trial used a split-mouth design: in each participant one maxillary quadrant received the whole force from the buccal side and the contralateral quadrant received half the force buccally and half palatally, with the total force identical on both sides. Canine displacement, rotation, tipping and first molar anchorage loss were measured on superimposed digital models over 12 weeks.
Background. Distalization of the maxillary canine is the first stage of two-step space closure in first premolar extraction cases. In sliding mechanics the retraction force acts at bracket level, occlusal and buccal to the centre of resistance of the canine, producing a couple that tips the crown distally in the sagittal plane and rotates it distopalatally in the occlusal plane. These movements increase bracket-archwire binding, convert the canine segment into a site of resistance, transfer load to the anchorage unit and require additional appointments for correction. Power arms reduce these effects by displacing the line of action apically toward the centre of resistance, but published trials indicate that this is achieved at the cost of a slower rate of retraction. Lingual mechanics have separately been credited with less canine rotation, because the centre of resistance lies palatal to the mid-buccolingual axis of the crown. In previous comparisons, however, buccal and lingual forces were always applied alternately and never simultaneously to the same tooth.
Objective. To compare canine distalization, canine distopalatal rotation, canine mesiodistal tipping and first molar anchorage loss between a quadrant in which the distalizing force was applied only from the buccal surface and a contralateral quadrant in which the same total force was divided equally between the buccal and palatal surfaces, in both cases delivered through canine and first molar power arms.
Design. Single-centre, split-mouth (within-person) randomized controlled trial with 1:1 allocation of the two maxillary quadrants of each participant. Both interventions were applied simultaneously in every participant, so each participant contributed one quadrant to each intervention. The unit of randomization and of analysis was the maxillary quadrant, and the two observations from each participant are paired.
Interventions. After levelling and alignment on a 0.019 x 0.025 inch stainless steel archwire left passive for four weeks, distalizing force was delivered by 9 mm nickel-titanium closed-coil springs acting between a 7 mm canine power arm placed in the vertical slot of the canine bracket and a power arm incorporated into the first molar tube. On the control quadrant a single spring delivered 200 g from the buccal side. On the experimental quadrant two springs delivered 100 g from the buccal side and 100 g from the palatal side, giving the same 200 g total; an additional vertical-slotted bracket was bonded to the palatal surface of the canine and a power-arm tube to the palatal surface of the first molar, and the bite was raised with glass ionomer on the mandibular first molars to prevent occlusal interference. Forces were re-measured with a dynamometer and reset to baseline at every four-week visit.
Assessment. Alginate impressions were taken at the start of distalization and at 4, 8 and 12 weeks. Casts were scanned and the digital models of each participant were superimposed on three palatal rugae landmarks. Linear measurements (canine distalization, first molar anchorage loss) were made on a plane parallel to the occlusal plane, and angular measurements (canine rotation, canine tipping) on the occlusal and sagittal planes respectively. Intra-examiner error was assessed by repeating 80 measurements after two weeks and calculating the Dahlberg error.
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Exclusion Criteria:
Previous extraction of any permanent tooth other than third molars
The maxillary quadrant randomly allocated to receive the distalizing force from both the buccal and the palatal surfaces. A nickel-titanium closed-coil spring delivered 100 g between the buccal canine power arm and the buccal first molar power arm, and a second spring delivered 100 g between a palatal canine power arm and a palatal first molar power arm, giving 200 g in total. Sixteen quadrants, one in each participant.
Device: Combined buccal and palatal distalizing force
The contralateral maxillary quadrant, in which the distalizing force was applied only from the buccal surface. A single nickel-titanium closed-coil spring delivered 200 g between the buccal canine power arm and the buccal first molar power arm. Sixteen quadrants, one in each participant.
Device: Buccal distalizing force
Canine distalization on a 0.019 x 0.025 inch stainless steel archwire using two 9 mm nickel-titanium closed-coil springs. One spring delivers 100 g between a 7 mm buccal canine power arm in the bracket vertical slot and the power arm of the first molar tube; the second delivers 100 g between a palatal canine power arm, placed in the vertical slot of a bracket bonded to the palatal surface of the canine, and a power-arm tube bonded to the palatal surface of the first molar. Total force 200 g. Forces re-measured and reset every four weeks.
Canine distalization on a 0.019 x 0.025 inch stainless steel archwire using a single 9 mm nickel-titanium closed-coil spring delivering 200 g between a 7 mm buccal canine power arm in the bracket vertical slot and the power arm of the first molar tube. Force re-measured and reset every four weeks.
Cumulative maxillary canine distalization
Linear distance, in millimetres, travelled by the maxillary canine cusp tip in the sagittal direction, measured as the distance between the projections of the cusp tip onto a reference line parallel to the midpalatal suture on digital models superimposed on three palatal rugae landmarks.
Time frame: From the start of distalization to 3 months
Maxillary canine distopalatal rotation
Angle, in degrees, between the line running from the canine cusp tip along the palatal ridge and a reference line parallel to the midpalatal suture, measured on the occlusal plane. Positive values denote distopalatal rotation.
Time frame: From the start of distalization to 3 months
Maxillary canine mesiodistal tipping
Distoocclusal angle, in degrees, between the line joining the distoincisal corner of the canine bracket to the cusp tip and the horizontal reference grid of the sagittal plane. Positive values denote mesial crown tipping, that is distal movement of the root; negative values denote distal crown tipping.
Time frame: From the start of distalization to 3 months
Maxillary first molar anchorage loss
Linear mesial displacement, in millimetres, of the most buccal point of the contact between the maxillary first molar and the mesial surface of the second premolar, projected onto a reference line parallel to the midpalatal suture.
Time frame: From the start of distalization to 3 months
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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