Table 2 Summary of the data from the included studies

MBT 0.022 × 0.028″ 0.018 × 0.025″ SS mini-screws; elastomeric chain 140–200 g

Orlus screw (width 1.6 and length 6). Three separate MOPs, vertical direction 2 mm apart and 3 mm in depth. One-time application at the start of retraction

Clinical measurements using electric digital calipers. Self-administered questionnaire (5-point Likert scale and VAS)

Distance from the central point of the canine bracket to superior margin of the mini-implant (maxilla) and the inferior margin of the mini-implant (mandible); overall pain intensity and impact of any pain on daily function

MOPs were associated with significant increased overall canine retraction over a 16-week period of observation, however not clinically significant; moderate pain was associated with MOP at 4-week intervals; mild pain in 8 and 12 weeks.

MBT 0.022 × 0.028″

0.016 × 22″ SS

Mini-screws.

100 g NiTi closing coil springs

Propel. Three MOPs distal to the canines, each perforation was 1.5 mm wide and 2 to 3 mm deep. One-time application at the start of retraction

Cast measurements with digital caliper. Gingival crevicular (GCF) fluids analysis. Rating scale from 1 to 10 for the level of discomfort

The distance between the canine and the lateral incisor in 3 points: incisal, middle, and cervical of the crowns. GCF collected before and after each visit to access the level of inflammatory response. Pain and discomfort levels at 24 h, 7, 14, and 28 days after the beginning of canine retraction

MOPs increased the rate of canine retraction 2–3-fold compared with the control group, reducing treatment time by 62%. Patients reported only mild discomfort locally at the spot of the MOP. At days 14 and 28, little to no pain was experienced.

MBT 0.022 × 0.028″

0.019 × 0.025″ SS.

Trans-palatal arch

tie-backs (150 g)

Propel. Three MOPs in the extraction space, 1.5 mm wide and 2–3 mm deep. Repeated after every 28 days until space closure was completed

Digital images using a 3D scanning of the plaster models. A 10-mm VAS

The extraction space, a mid-palatine line drawn from distal surface of canine to the mesial surface of the 2nd premolar. Pain perception at 24 h, 7 days, and 28 days after MOP

Acceleration of tooth movement was seen with MOPs. Minimal discomfort was observed post-procedure for participants who had undergone MOPs.

MBT 0.022 × 0.028″

Rectangular wires

Banding 1st and 2nd Molars

Niti coil springs 100 g

Propel. Three separate MOPs’ distal in the canine, 1.5 mm diameter and 2.5 mm in depth. One-time application at the start of retraction

Digital images using a 3D scanner of the plaster models. Numerical rating scale (NRS)

The distance between the tip of the canine and the midpoint of incisor edge of lateral incisor, and the cervical midpoints on height of contours of respective cingulum x and y coordinates on 3D images. Pain intensity at 4 h after the procedure, and after every 24 h for the next 7 days

MOPs accelerated orthodontic tooth movement by 2–3-fold. A significant difference was found in the perception of pain among experimental and control group on the 1st and 2nd days. However, the difference was insignificant during the rest of the week.

SLB Roth 0.022″

019 × 25″ SS

Mini-screws

9 mm Niti closed coil spring (200 g)

Propel. Three vertical MOPs in the midway space between canine and 2nd premolar, 6–8 mm deep. Repeated after every activation session until space closure was completed

Digital measurements using Q3DC tool (plaster dental models digitally converted). Treatment time. OHIP-14 questionnaire

Distance from the most distal point in the canine and most mesial point in the 2nd premolar. Closing time between groups (mm/month). Quality of life assessment

Three MOPs were inefficient for accelerating tooth movement during anterior retraction. MOPs produced more impact on OHRQOL immediately following the MOP procedure and after 3 days.

Roth 0.022″

0.017 × 0.025 SS wire mini-screws

Niti closing coil springs (150 g)

Mini-screw (UNITEK), 1.8 × 8 mm. Three MOPs were performed midway in the extraction space, using a TAD 1.8 × 8mm.

One-time application before canine retraction

Dental models (T0–T4) scanned (images superimpositions). CBCT images before and after treatment. Pain Rating Scale (1–10)

The distance between the canine cuspid tip and frontal plane (FP) in each model (T0–T4). Rate of canine retraction, and the sagittal distance between the mesiobuccal cusp tip of the 1st molar and FP was used to measure anchorage loss. Pain intensity assessed immediately after MOPs, 1 day, 3 days, and 1 week after intervention. Root resorption

MOPs were not able to accelerate the rate of canine; however it seemed to facilitate root movement. Mild to moderate transient pain was experienced following the MOP procedures that almost disappeared 1 week later. No anchorage loss or root resorption was detected.

MBT .022 × .028 0.019″ × 0.025″ brass-posted wire mini-screws

NiTi closing coil spring 150 g

Mini-screw (MTN-2), 1.6 × 8 mm. Three MOPs were performed in the distal of the canine, depth: 5 mm. Repeated in the 4th week of distalization

Plaster models scanned

Canine distalization, canine rotation, and canine tipping and molar mesialization. Anchorage loss

MOPs significantly increased the canine distalization rate at the T1–T3 interval in the maxilla (0.4 mm). The new MOPs performed at T3 did not trigger the canine distalization rate. Tooth movement was faster in the maxilla than in the mandible.

Roth 0.022 × 0.028 0.019 × 0.025 SS wire

2nd molar.

Niti coil 200 g

Mini-screw (Jeil Medical), 1.6 × 3 mm. Two MOPs were performed in 5 mm and 8 mm of crestal bone. Bony screw 1.6 mm diameter and 3 mm length. One-time application at the start of retraction

Plaster models scanned

Distance between the canine and the 2nd premolar measured in three areas: center of the canine and premolar bracket, the canine cusp tip and premolar buccal cusp tip, and the shortest distance between canine and premolar cervico-gingival line

MOPs increased the rate of tooth movement by more than 2-fold when compared to the control side. No significant difference in the rate of tooth movement in the canine retraction, maxilla, and mandible, between interventional and control.

MBT 0.022 × .028 0.019 × 0.025 SS wire

Mini-screw

NiTi closed coil spring 150 g.

Mini-screw (Aarhus), 1.5 × 6 mm. Three MOPs of 1.5 mm width and 3 to 4 mm, 3 mm distal to canine and 6 mm from the free gingival margin. One-time application before retraction

3D models obtained every month; clinical measurements using a digital caliper; digital periapical radiographs; VAS; periodontal clinically evaluation

Amount of canine displacement, rate of canine retraction, anchorage loss, canine tipping, canine rotation, root resorption, plaque index, gingival index, pain level, patients’ satisfaction and degree of ease, willingness to repeat the procedure and recommendation to others

Three MOPs were not effective for accelerating tooth movement. No significant differences of anchorage loss, canine rotation, and tipping. Root resorption was similar for both groups. No adverse effect of periodontal health. The level of pain was minimal and faded after 24 h on both sides. MOPs had no effect on the patients’ daily life except for a feeling of swelling on the first day. Patients’ level of satisfaction regarding the MOP was high.

Edgewise 0.022 × 0.028

0.018 × 0.025 wire,

Mini-screws

CrNi coil spring 150 g or elastomeric 150 g

Propel. Three MOPs switch a depth of 5 mm distal and parallel to the canine root. One-time application at the start of retraction

Digital models obtained using a 3D scanner. Panoramic radiographs with radiopaque markers

Anteroposterior distances between canine cusp tips and PMs. Angle formed between the long vertical and mesiodistal axis of the canines. Discomfort questionnaire with four questions, three answered by VAS scale.

MOPs do not accelerate tooth movement significantly. The perception of MOP discomfort was considered mild to moderate.

MBT

N.A

Mini-screw

Niti Coil spring 150 g

Automated mini-implant instrumentation. Three perforations of 1.5–2 mm width and 5–7 mm depth in the middle of the extraction space. One-time application at the start of retraction

Digital images from 3D scanner; photographs and CBCT images; McGill Pain questionnaire

The distance between canine and second premolar; a point on the crown tip and the apex tip; the distance between cementoenamel junction and marginal bone crest from the buccal and lingual sides; numeric scale for pain intensity

MOPs do not significantly speed up tooth movement. Pain and discomfort appear to be exactly similar on both sides. No difference between groups regarding bone height and root resorption.

MBT 0.022-in

0.016 × 0.022″ SS wire mini-screw

NiTi closed coil spring 150 g

Mini-screws 1.2 mm diameter. Three perforations with to a depth of 1 mm, between the distal of the canine and the mesial of the 2nd premolar. The first MOP was located 5 mm away from the free gingival margin. One-time application at the start of retraction

Plaster models measured using a digital caliper; VAS

The distance between the canine and lateral incisor measured at three points (incisal, middle, and cervical). The amount of pain associated to MOP was evaluated in the day of canine retraction and 24 h later.

MOPs were effective in accelerating tooth movement over a period of 3 months, but not clinically significant. There was no increase in the level of pain and discomfort due to MOPs.