Ma 2008.

Methods	Trial design: single‐centre RCT (parallel group) Location: Orthodontic Department at the School of Stomatology, Nanjing Medical University, China Recruitment period: not stated Funding source: The Science and Technology Department, Education Department of Jiangsu Province; and the National Natural Science Foundation of China Source of participants: patients attending clinic Study duration: not stated Time points at which follow‐up are reported: from start of treatment until the end of treatment
Participants	30 participants in total: age range between 18‐22 years (14 males and 16 females) 15 in the mini‐screw implant group 15 in the headgear group Inclusion criteria: bimaxillary anterior protrusion require maximum anchorage extraction of all first premolars
Interventions	Comparison 1: Mini‐screw implants (AbsoAnchor, Dentos Inc., Daugu, Korea) 1.2 mm diameter; maxilla 6 mm length, mandible 5 mm length Placed between the maxillary second premolars and first molars, and between the mandibular first molars and second molars Loaded immediately with 100 g of force using activated nickel titanium coil springs (Grikin Co., Beijing, China) to retract the anterior teeth 1‐step retraction of the anterior arch segment was carried out Comparison 2: Headgear (Shinye Odontological Materials Co. Ltd, Hangzhou, China) Applied during the same period as for the micro‐implant group Outer face bows were bent upwards at an angle of 20 degrees A force of 350 g applied until all premolar spaces were closed 1‐step retraction of the anterior arch segment was carried out
Outcomes	No outcomes concerned with this review were reported
Notes	Pre‐adjusted straight wire appliances were used with an MBT prescription
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "The subjects were randomly divided (RandA1.0 Software, Planta Medical Technology and Development Co. Ltd, Beijing, China) into two equal groups"
Allocation concealment (selection bias)	Unclear risk	Not addressed
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "Tracing, superimposition, and measurement were undertaken manually by two examiners who did not participate in the study design" Comment: blinding of outcome assessment probably achieved because the radiographs were taken before and immediately after treatment; at these points of treatment, the appliances are not fixed inside the mouth, and hence do not show on the radiographs
Incomplete outcome data (attrition bias) mesial movement of upper first maxillary molar	Low risk	All randomised patients accounted for
Selective reporting (reporting bias)	High risk	Selective reporting of outcomes: movement of molars was not reported Selective reporting of data: not relevant because no outcomes concerned with this review were reported
Other bias	Low risk	Study appears to be free of other sources of bias