Efficacy of orthodontic mini implants for en masse retraction in the maxilla: a systematic review and meta-analysis

Abstract

Background/aim: Retraction of the upper incisors/canines requires maximum anchorage. The aim of the present study was to analyze the efficacy of mini implants in comparison to conventional devices in patients with need for en masse retraction of the front teeth in the upper jaw.

Material and methods: An electronic search of PubMed, Web of Science, and EMBASE and hand searching were performed. Relevant articles were assessed, and data were extracted for statistical analysis. A random effects model, weighted mean differences (WMD), and 95% confidence intervals (CI) were computed for horizontal and vertical anchorage loss at the first molars in the analyzed patient treatments.

Results: A total of seven RCTs employing direct anchorage through implants in the alveolar ridge were finally considered for qualitative and quantitative analysis, and further five publications were considered for the qualitative analysis only (three studies: indirect anchorage through implant in the mid-palate, two studies: direct/indirect anchorage in the alveolar ridge). In the control groups, anchorage was achieved through transpalatal arches, headgear, Nance buttons, intrusion arches, and differential moments. WMD [95% CI, p] in anchorage loss between test and control groups amounted to - 2.79 mm [- 3.56 to - 2.03 mm, p < 0.001] in the horizontal and - 1.76 mm [- 2.56 to - 0.97, p < 0.001] favoring skeletal anchorage over control measures. The qualitative analysis revealed that minor anchorage loss can be associated with indirect anchorage, whereas anchorage gain was commonly associated with direct anchorage. Implant failures were comparable for both anchorage modalities (direct 9.9%, indirect 8.6%).

Conclusion: Within its limitations, the meta-analysis revealed that maximum anchorage en masse retraction can be achieved by orthodontic mini implants and direct anchorage; however, the ideal implant location (palate versus alveolar ridge) and the beneficial effect of direct over indirect anchorage needs to be further evaluated.

Keywords: Bone screws; En masse retraction; Meta-analysis; Micro implants; Mini implants; Orthodontic anchorage procedures; Systematic review; TAD.

Fig. 1

PRISMA study flow diagram

Fig. 2

Graphic visualization of the risk of bias judgements

Fig. 3

Forest plot for anchorage loss in the horizontal dimension

Fig. 4

Forest plot for anchorage loss in the vertical dimension

Fig. 5

Funnel plot for anchorage loss in the horizontal dimension (MD mean difference, SE standard error)

Fig. 6

Funnel plot for anchorage loss in the vertical dimension (MD mean difference, SE standard error)