Table 2 Characteristics of the included studies

Ghajar et al. [43] 2013 – Iran

48 Wistar rats [24 pregnant - 1^stw; 24 control]

3 m; 250 ± 25 g; parity nm

Sample size calculation: nm

SS spring between Mx CIs [30 g]

Force application: 2w

Clinical measurements

Distance between the mesial corners of MxCIs^a

Method error assessment: No

Hellsing and Hammarström [44] 1991 – Sweden

10 Sprague-Dawley rats [5 pregnant - beginning; 5 control]

3-5 m; 260 g on average; parity nm

Sample size calculation: nm

0.011″ Australian wire between Mx FMs [15 g at 1 mm]

Force application: 3w

Measurements on occlusal radiographs

Transverse distance between the ends of the outer arms of the wire^b

Method error assessment: Yes

Kim and Lee [45] 2000 - Korea

40 Sprague-Dawley rats [20 pregnant; 20 control]

10 w; 200-280 g; parity nm

Sample size calculation: nm

NiTi spring to between Mx CI and FM [40 g]

Force application: 2w

Measurements on lateral ceph. Radiographs

Mesial movement of the Mx FM^c

Method error assessment: No

Macari et al. [46] 2018 – New Zealand & Brazil

12 C57BL/6 mice [6 lactating – d 9 postpartum; 6 control nulliparous]

15-17w

Sample size calculation: nm

NiTi spring between Mx CI and FM [35 g]

Force application: 12d

Measurements on micro-CT

Difference of the cemento-enamel junction distance of FM and SM between the control and experimental side^d

Method error assessment: No