This systematic review was structured and conducted according to the preferred reporting items of the PRISMA statement [34].

The focused question serving for literature search was structured according to the PICO (Patients, Intervention, Control, Outcome) format: “In patients with a need for en masse retraction of the upper front teeth, what is the efficacy of orthodontic mini implants for anchorage control compared with conventional devices?” According to the PICO convention, this question has been formulated as follows:

Patients: for which subgroups of patients with a need for en masse retraction of the upper incisors/canines

Intervention: do orthodontic mini implants have a benefit over conventional devices?

Control: compared to forgoing orthodontic mini implants (compared to conventional treatment)

Outcome: with regard to treatment efficacy (anchorage control), treatment duration, potential harms (inflammation, implant loss)

The PubMed database of the US National Library of Medicine, EMBASE, and the Web of Knowledge of Thomson Reuters were used as electronic databases to perform a systematic search for relevant articles published in the dental literature between 1992 and Dec 31, 2017. Furthermore, the Cochrane Central Register of Controlled Trials (CENTRAL) was searched manually.

A commercially available software program (Endnote X7, Thomson, London, UK) was used for electronic title management. Screening was performed independently by two authors (K.B. and M.W.). Disagreement regarding inclusion during the first and second stage of study selection was resolved by discussion.

The combination of key words (i.e., Medical Subject Headings MeSH) and free text terms included:

Search terms PubMed/MEDLINE (including MeSH terms)

(“en-masse retraction” OR “incisor retraction” OR “front retraction” OR “orthodontic gap closure” OR or “orthodontic space closure” OR “extraction therapy” [mh])AND (“mini implants” OR “micro screws” OR “micro implants” OR “skeletal anchorage” OR “palatal implant” OR “skeletal” OR “skeletal anchorage” OR “implant” OR “bone screw” OR “temporary anchorage device” OR “TAD” OR “Bone screws”[mh] OR “intraosseous screw” OR “dental implants”[mh])