Background: Closed and open surgical techniques are two different main approaches to surgical exposure of palatally displaced canines (PDCs). Because there is insufficient evidence to support one technique over the other, there is a need for randomized controlled trials.

Objectives: To compare surgery time, complications and patients' perceptions between closed and open surgical techniques in PDCs.

Trial design: The trial was a multicentre, randomized, controlled trial with two parallel groups randomly allocated in a 1:1 ratio.

Material and methods: Study participants were 119 consecutive patients from 3 orthodontic centres, with PDCs planned for surgical exposure, randomly allocated according to a computer-generated randomization list, using concealed allocation. Full-thickness mucoperiosteal flap was raised, and bone covering the canine was removed in both interventions. In closed exposure, an attachment with a chain was bonded to the canine and the flap was sutured back with the chain penetrating the mucosa. In open exposure, a window of tissue around the tooth was removed and glass ionomer cement placed on the canine crown, to prevent gingival overgrowth during spontaneous eruption. Patient perceptions were assessed with two questionnaires, for the evening on the day of operation and 7 days post-surgery.

Blinding: It was not possible to blind either patients or care providers to the interventions. The outcome assessors were blinded and were unaware of patients' intervention group.

Results: Seventy-five girls and 44 boys, mean age 13.4 years (SD 1.46) participated in the study and got either of the interventions (closed exposure, n = 60; open exposure, n = 59). Surgery time did not differ significantly between the interventions. Complications though were more severe in bilateral cases and the patients experienced more pain and impairment in the open group.

Conclusion: There were no statistically significant differences regarding surgery time between the groups. Postoperative complications were similar between the groups in unilateral PDCs, but more common in the open group in bilateral cases. More patients in the open group experienced pain and impairment compared to the closed group.

Trial registration: Trial registration: ClinicalTrials.gov, ID: NCT02186548 and Researchweb.org, ID: 127201.