Table 2 Characteristics of the included trials

Boysen et al. [39]

CCT

34 children UFPXB:

G1 (8.3 Y): 17 QH

G2 (8.6 Y): 17 EP

G1 (QH): treatment duration 101.2 D

G2 (EP): treatment duration 115.4 D

Retention: 3 M

Observation: 2 Y

IC: QH 5.1 mm

EP 3.5 mm**

IM: QH 5.6 mm

EP 4.6 mm*

Mandibular IM: decreased in QH (− 0.02 mm)

Increased in EP (0.02 mm)*

Mandibular IC: increased in QH (0.01 mm)

Decreased in EP (− 0.16 mm)*

Brin et al. [40]

CCT

34 children:

TG (9.5 Y): 24 (UFPXB) EP

CG (9.8 Y): 10 normal

TG (EP): duration 10 M

Retention 6 M

IM increased in

EP (3 mm) and became similar to the CG

Success rate:

EP 50%

No relapse after 6 M

Midline deviation correction:95%

The mandibular arch width in TG: decreased (25% of the cases); increased (50%); remained the same (25%)

Bjerklin et al. [41]

CCT

38( FPXB):

G1 (9.3 Y): 19 QH

G2 (9.2 Y):19 EP

CG (8.8 Y): 19 normal

G1 (QH): 7.7 M

G2 (EP): 12.5 M

Retention 3–5 M

Observation 5.5 Y

IC: (QH): 1.6 mm

(EP): 2.3 mm*

IM: (QH): 3.6 mm

(EP): 2.9 mm*

Success rate in both groups was 100%

Relapse (after 5.5 Y):

(QH) 3/19

(EP) 1/19

No differences in the mandibular arch

Petren et al. [42]

RCT

60( FPXB):

A (9.1 Y): 15 QH

B (8.7 Y): 15 EP

C (8.3 Y): 15 composite onlay

D (8.8 Y): 15 CG

Group A: 4.8 M

Group B: 9.6 M

Group C: 1 Y

Retention:

Groups A and B:6 M

Observation: 1 Y

IC: A: 1.4 mm

B: 2.4 mm**

C: 0.5 mm

D: 0.2 mm*

IM: A: 4.6 mm

B: 3.5 mm**

C: 0.5 mm

D: 0.4 mm*

Success rate

A: 15/15 (100%)

B: 10/15 (66.6%)**

C: 2/15 (13.3%)

D: 0/15 (0%)*

Midline deviation correction:

A:14/15

B:12/15

C:6/15

D:3/15

Mandibular arch changes:

IC (*)

IM ( increased in B & D groups)

Godoy et al. [6]

RCT

99 (FPXB):

G1 (8 Y): 33 QH

G2 (7.8 Y): 33 EP

G3 (8.09 Y): CG

QH: 4.24 M

EP: 6.12 M

Retention: 6 M

Observation: 12 M (after cross bite correction)

IC: (QH): 4.5 mm

(EP): 1.8 mm*

IM: (QH): 5.7 mm

(EP): 4.46 mm*

Success rate (QH):100%

(EP):90.9%

(CG): 0%

Relapse: (QH): 9.1%

(EP): 9.1%

Mandibular arch changes:

IM: QH > EP & CG

Side effects occurred in:

(QH):39.4%

(EP): 27.3%

Petren et al. [43]

RCT

40 (PXB) with midline deviation:

A(9 Y): 20 QH

B (8.5 Y): 20 EP (withdrawal of 5 patients later)

CG (8.8 Y): 20 normal

Treatment duration: 1Y

Retention: 6 M

Observation: 3 Y

IC: A: 2.7 mm

B: 2.6 mm*IM: A: 4.1 mm

B: 3.8 mm*

Relapse after 3 Y: (QH): ½0

(EP): 0/15*

Midline deviation:

correction occurred in > 50% in both groups with no significant differences

Mandibular arch changes: IC:*

IM: B > A

Lippold et al. [44]

RCT

77 (FPXB):

A (8.3 Y): 37 bonded Hyrax followed by a U-bow activator ( withdrawal of 6 patients later)

B (8.2 Y): 40 CG ( withdrawal of 5 patients later)

Bonded Hyrax: 3.2 W

Retention: 12.6 W

U-bow activator: 36.8 W

IC: A: 2.6 mm

B: 1 mm**

IM:A: 5.1 mm

B: 0.8 mm**

midline correction:

A > B

Mandibular arch changes:*

Sollenius et al. [45]

RCT

135 UFPXB:

1.QHS (9.3Y): 28 QH in SOC

2. QHG (9.5Y): 27 QH in GDC

3.EPS(8.7Y): 27 EP in SOC

4. EPG (9.2Y): 28 EP in GDC

5.Untreated group (8.5Y): 25

CG (9.3Y): 25 normal

Treatment duration:

QHS: 7.5 M

QHG: 8.2 M

EPS: 11.4 M

EPG: 12 M

Including 3 M for retention

IC: QHS > QHG & EPS & EPG**

IM: QHS > QHG & EPS & EPG**

Success rate:

QHS: 100%

QHG: 85.1%

EPS: 66.6%

EPG: 64.2%

Treatment by QHS was significantly more successful compared to other groups

Sollenius et al. [46]

RCT

110 (FPXB):

1. QHS (9.3Y): 28 QH in SOC

2. QHG (9.6Y): 27 QH in GDC

3. EPS (8.8Y): 27 EP in SOC

4. EPG (9.0Y): 28 EP in GDC

Number of appoint

QHS: 7.1

QHG: 8.4

EPS: 8.2

EPG: 9.2

Including 3 M of retention

Success rate:

QHS: 100%

QHG: 85.18%

EPS: 66.6%

EPG: 64.28%

midline correction: QHS: 85.71%

QHG: 50%

EPS: 59.25%

EPG: 50%