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Table 3 The quad-helix versus the expansion plates (pre and post-expansion differences in the evaluated outcomes) and the RME versus an untreated CG (pre and post-treatment measurements of the evaluated outcomes)

From: The effectiveness of the early orthodontic correction of functional unilateral posterior crossbite in the mixed dentition period: a systematic review and meta-analysis

References Comparison between QH and EP
Outcomes changes (T2-T1)
Maxillary intermolar width [mm] Maxillary intercanine width [mm] Mandibular intermolar width [mm] Mandibular intercanine width [mm] Success rate [ratio] Relapse rate at different time points [ratio] Treatment duration [months] Correction of the mandible midline [ratio]
Boysen et al. [39] QH: 5.61 ± 1.78
EP: 4.65 ± 1.52
QH: 5.17 ± 1.86
EP: 3.50 ± 1.25
QH: − 0.20 ± 2.32
EP: 0.02 ± 0.36
QH: 0.01 ± 0.74
EP: − 0.16 ± 0.64
Not-studied Not-studied Not-studied Not-studied
Bjerklin et al. [41] QH: 1.2 ± 0.67
EP: 1.5 ± 1.04
QH: 1.6 ± 1.04
EP: 2.3 ± 1.22
QH: 0.0 ± 0.21
EP: 0.0 ± 0.57
QH: 0.1 ± 0.23
EP: − 0.1 ± 0.91
QH: 19/19
EP: 19/19
Not-studied QH: 7.7 ± 2.79
EP: 12.5 ± 4.22
Not-studied
Petren et al. [42] QH: 4.4 ± 1.19
EP: 3 ± 1.57
QH: 2 ± 1.18
EP: 2.7 ± 1.2
QH: − 0.1 ± 0.62
EP: 0.5 ± 0.67
QH: 0.1 ± 0.26
EP: 0.2 ± 0.28
QH: 15/15
EP: 10/15
Not-studied QH: 4.8 ± 3.52
EP: 9.6 ± 3.04
QH: 14/15
EP: 12/15
Petren et al. [43] QH: 3.7 ± 1.58
EP: 3.2 ± 1.24
QH: 2.7 ± 1.57
EP: 2.6 ± 1.58
QH: − 0.4 ± 0.82
EP: 0.4 ± 0.67
QH: − 0.5 ± 1.21
EP: 0.5 ± 1.42
Not-studied Relapse after 3 Y
QH: ½0
EP: 0/15
Not-studied Not-studied
Godoy et al. [6] QH: 5.7 ± 2.31
EP: 4.46 ± 2.22
QH: 3.48 ± 2.24
EP: 1.8 ± 2.96
QH: 0.46 ± 1.20
EP: − 0.12 ± 1.36
QH: − 0.21 ± 0.92
EP: 0.28 ± 1.51
QH: 33/33
EP: 30/33
Relapse after 1 Y
QH: 3/33
EP: 3/33
QH: 4.24 ± 2.05
EP: 6.12 ± 3.25
Not-studied
Sollenius et al. [45] QH: 4.11 ± 1.86 A
EP: 2.49 ± 1.67 A
QH: 3.36 ± 1.87 A
EP: 2.53 ± 2.81 A
Not-studied Not-studied QH: 51/55 A
EP: 36/55 A
Not-studied QH: 4.84 ± 1.88 A
EP: 8.7 ± 3.49 A
Not-studied
Sollenius et al. [46] Not-studied Not-studied Not-studied Not-studied Not-studied Not-studied Not-studied QH:34/48 A
EP: 26/44 A
References Comparison between RME and untreated CG
Measurement time Maxillary intermolar width [mm] Maxillary intercanine width [mm] Mandibular intermolar width [mm] Mandibular intercanine width [mm] Correction of the mandible midline [mm]   
Lippold et al. [44] T1 RME (n = 31): 42.2 ± 2.6
CG (–35): 42.6 ± 3.1
RME (n = 31): 29 ± 2.6
CG (–35): 27.9 ± 2.2
RME (n = 31): 48.1 ± 2
CG (n = 35): 47.2 ± 02.5
RME (n = 31): 25.8 ± 1.9
CG (n = 35): 25.2 ± 1.7
RME (n = 31): 2.1 ± 1.3
CG (n = 35): 1.9 ± 1.2
  
  T2 RME (n = 31): 47.3 ± 2.5
CG (–35): 43.4 ± 2.3
RME (n = 31): 32.6 ± 2.7 A
CG (–35): 28.9 ± 2.2
RME (n = 31): 48.6 ± 1.7
CG (n = 35): 47.7 ± 2.6
RME (n = 31): 25.9 ± 1.7
CG (n = 35): 25.4 ± 1.6
RME (n = 31): 0.5 ± 0.5
CG (n = 35): 2.1 ± 1.3
  
  1. QH: quad-helix, EP: expansion plate, T1: before expansion, T2: after expansion, A: the mean and SD for the combined subgroups were calculated mathematically depending on certain formulas. CO: centric occlusion, MO: maximum occlusion, XB: crossbite, N-XB: non-crossbite, RME: rapid maxillary expansion, CG: control group