Table 1.

Summary of the characteristics of included studies.

Authors	Study Design	Study Sample: Patients (M/F); Mean Age (Years) at T0; No. of ICI; Groups	Intervention: Type of Surgery, Type of Traction	Methods and Timing of Evaluation and Mean Follow-Up Period	Eligible Outcome
Becker et al. [11]	RS	21 (6/15); 17.5; The treatment group—No. of ICI: 21 The control group—21 normally erupted CCI.	CET Ortho-T—light traction, maintained on the ligature wire	-Periodontal clinical examination (T2) -Periapical X-rays (T2) Follow-up—4.5 years	Probing depth (PD) Width of the attached gingiva Gingival contour Bone support
Chaushu et al. [14]	RS	12 (4/8); 22 (from 15 to 38); The treatment group—No. of ICI: 12 The control group—12 normally erupted CCI.	OET Ortho-T—light traction, maintained on the ligature wire, initiated shortly after surgery.	-Periodontal clinical examination (T2) -Periapical X-rays (T2) Follow-up—10.5 months (range 3–25 months)	Average forced eruption duration Probing depth (PD) Width of the attached gingiva Gingival contour Bone support
Ho and Liao, [16]	RS	80 (32/48); 9.2 ± 2.3 (from 6.4 to 20.6); No. of ICI: 80 ICI, no mechanical obstacle to eruption. No dilaceration group (n = 64). Root dilaceration group (n = 16). The control group—80 normally erupted CCI.	CET—for deeply ICI (n = 29) OET—for labially and not far apically ICI (n = 51) Ortho-T—initiated 1–2 weeks after surgery with a bonded orthodontic traction device (force approximately 100 g.)	Cephalometric (T0), Periapical radiographs (T1). Follow-up—21.8 ± 28.6 months (range 6.0–146.1 months)	Average forced eruption duration Root length (T1)
Shi et al. [18]	RS	30 (20/10); 8.44 ± 1.20 (from 6.5 to 11.2); The treatment group—No. of ICI: 30 immature ICI. Root dilacerations n = 24. The control group—30 naturally erupted immature CCI.	CET Ortho-T—elastomeric chain, force 100 g. 19 patients had an orthodontic reopening of incisor space before surgical treatment.	CBCT (T0 and T2). Follow-up—1.76 ± 3.41 (range 0–15 months)	Average forced eruption duration Root length Alveolar bone loss on labial/lingual sides The alveolar bone thickness of labial/lingual alveolar crest Lingual/labial alveolar bone thickness at the root apex
Sun et al. [19]	PCT	28 (13/15); 8.2; No. of ICI: 28 labial inversely ICI in the mixed dentition. Early-treated group (ET, n = 14; root formation stages 7 and 8) Later-treated group (LT, n = 14; root formation stages 9 and 10) The control group—28 CCI with normal root formation and orientation.	SE (modification not described) and Ortho-T	CBCT (T1) Follow-up—not defined	Root length Alveolar bone loss in lingual/labial sides Alveolar bone thickness in lingual/labial sides
Hu et al. [12]	RS	12 (5/7); 7.80 ± 0.91 (from 6.25 to 9.42); The treatment group—No. of ICI: 12 labial inversely ICI, immature root at the beginning of treatment The control group—12 normally erupted CCI.	CET Ortho-T—using the Guide rod appliance	CBCT (T1, T2) Follow-up—24.57 ± 4.33 months (range 18.40–34.53 months).	Average forced eruption duration Root length: dilacerated root length (DRL) and directed root length (DIRL) Labial/lingual alveolar bone vertical loss Labial/lingual alveolar bone thickness of the crest Labial/lingual alveolar bone thickness at the apex
Sfeir et al. [20]	RCT	28 (21/7); Age ranged from 8 to 10 years; No. of ICI: 28 ICI, due to an obstacle, insufficient space, or insufficient eruption potential. Discontinuous traction group (DT, n = 13) Continuous traction group (CT, n = 15) The control group—28 completely erupted CCI	CET DT—traction interruption for a month after crown emergence CT—continuous traction. (elastomeric chain, the force of 1 ounce (30 gm))	-Periapical digital X-rays -anterosuperior CBCT scans -periodontal probing (T2) Follow-up—not defined	Mesial and distal alveolar ridges of the ICI and CCI (MBL, DBL) Labial and palatal alveolar ridge levels of ICI and CCI (LBL, PBL) Periodontal probing of ICI and CCI on all four sides of each tooth (MP, LP, DP, PP)

RS, Retrospective study; RCT, Randomized clinical trial; PCT, Prospective controlled clinical trial; M, males; F, females; ICI, maxillary impacted central incisors; CCI, contralateral central incisors; SE, surgical exposure; CET, closed-eruption surgical technique; APFT, apically positioned flap technique; OET, open-eruption surgical technique; DT, discontinuous traction; CT, continuous traction; Ortho-T, orthodontic traction; T0, Before treatment; T1, Immediately after treatment; T2, At the follow-up.