Anchorage loss during canine retraction using intermittent versus continuous force distractions; a split mouth randomized clinical trial.

OBJECTIVES: The aim of this study was to evaluate the anchorage loss, amount and time of canine retraction, and canine tipping concomitant with periodontal ligament distraction (PLD) using intermittent and continuous forces.

MATERIALS AND METHODS: This was a split mouth randomized clinical trial involving 30 patients in need of first premolar extraction. For each patient, one side was randomly allocated to receive a screw-based dental distractor, and the other side a continuous force coil spring distractor. Molar and canine movements were recorded on study casts using the rugae as reference. Changes in the long axis of the canines were evaluated from pre- and post distraction panoramic radiographs.

RESULTS: On the screw side, molars moved mesially 2.5±0.9 mm. The canine tipped distally a mean of 10.5°±3.1°. The average time needed for canine retraction was 5.3±1.3 weeks. In the coil side, the molar mesial movement was not statistically different from the screw group (2.8±1.5 mm). The canine moved bodily with a mean distal tip of 0.27°±1.75° in a period of 27.8±6.6 weeks.

CONCLUSIONS: Anchorage loss occurs with dental distraction using either intermittent or continuous force. No significant difference in anchorage loss was found with either type of force. The surgical intervention did not shorten the time needed for canine retraction using the continuous force. Continuous force leads to slow bodily retraction of the canine unlike the intermittent force which leads to rapid tipping of the canine.