Table 3. Characteristics of the included studies (conventional non-accelerated traction studies).

RCT: randomized clinical trial; Q-RCT: quasi-randomized trial; M: males; F: females; PDC: palatally displaced canine; TPA: transpalatal arch; BOP: bleeding on probing; CEJ: cementoenamel junction; TADs: temporary anchorage devices.

Study/setting	Study design	Intervention (type of appliance, type of attachment, mechanism of traction, type of withdrawal technique)	Comparison (type of appliance, type of attachment, mechanism of traction, type of withdrawal technique)	Outcome measures	Conclusions
Smailiene et al. (2013) [7], Sweden	Q-RCT, unilateral PDC	Fixed appliances, open surgical approach, and free eruption	Fixed appliances, ballista loop, and closed flap surgery	Duration of orthodontic traction, duration of orthodontic treatment, probing pocket depth, the width of keratinized tissue, gingival recession, bone support	There were no significant differences in the post-treatment periodontal status of the canines and adjacent teeth either by open surgery with free eruption or by closed flap technique
Parkin et al. (2012) [17], UK	RCT, unilateral PDC	Fixed appliances, eyelet attachment with a golden chain, and open surgical exposure	Fixed appliances, eyelet attachment with a golden chain, and closed surgical exposure	Actual surgical time, patient-reported outcome	There was no difference in the operating time between the open and closed surgical techniques. There were no differences in any of the patient-reported outcomes between the two surgical procedures. Most participants reported pain, discomfort, impairment to everyday activities, and the need for regular analgesia after surgical exposure were of short duration and subsided after a few days
Heravi et al. (2016) [15], Iran	CCT, unilateral or bilateral PDC	Fixed appliances, two miniscrews, cantilever springs, and open surgical exposure	Fixed appliances, trans palatal arch (TPA), cantilever spring, and open surgical exposure	Canine and lateral incisor root resorption, BOP, gingival index, patient’s pain experience, duration of orthodontic traction	The mean duration of the forced eruption was 5.2 months in the control group and 5.1 months in the experimental group. The clinical success rate was 100%. TADs allow a more controlled movement of the impacted tooth
Gharaibeh and Al-Nimri(2008) [12], Jordan	Q-RCT, unilateral PDC	Fixed appliances, a golden chain, and closed surgical exposure	Fixed appliances, lingual button, a golden chain, and open surgical exposure	Duration of surgery and the patient’s perception of pain	The mean surgical duration for the open-eruption technique was 30.9 ± 10.1 minutes compared with 37.7 ± 8.4 minutes for the closed-eruption technique. This difference was statistically significant (p = 0.006). On the first postoperative day, six patients (33%) in the close-eruption group reported severe pain compared with four patients (22%) in the open-eruption group. This difference was not statistically significant (p = 0.123)
Björksved et al. (2018) [40], Sweden	RCT, unilateral or bilateral PDC	Fixed appliances, attachment with a chain, and closed surgical technique	Fixed appliances and open surgical technique	Surgery time, complications, and patients’ perceptions	No statistically significant differences in surgery time between the two 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
Parkin et al.(2013) [41], UK	RCT, unilateral PDC	Fixed appliances, twin-wire technique or elastic chain, and open surgical exposure	Fixed appliances, twin-wire technique or elastic chain, and closed surgical exposure	Clinical periodontal attachment level, crown height, gingival recession, radiographic alveolar bone levels, duration of orthodontic traction	Duration: open exposure - 10.2 months (SD: 4.2); closed exposure - 13.2 months (SD: 8.5). Exposure and alignment of the PDCs have a small impact on periodontal health
Smailiene et al. (2013) [42], Sweden	Q-RCT, unilateral PDC	Fixed appliances, open surgical approach, and free eruption	Fixed appliances, ballista loop, and closed flap surgery	Post-treatment status (radiological, periodontal, and intraoral examination), visual assessment of the color and shape of the crown, inclination, position in the dental arch, and function) of palatally impacted canines	The post-treatment status of the palatally impacted and the adjacent teeth after the surgical-orthodontic treatment did not significantly differ between the groups treated with the two different surgical methods (open and closed). Both treatment methods can be considered acceptable for the treatment of palatally impacted canines