Distalization of maxillary molars using temporary skeletal anchorage devices: A systematic review and meta-analysis

The aim of this systematic review is to assess the treatment effects (amount of distalization, distal tipping and vertical movement) of buccally versus palatally placed temporary skeletal anchorage devices (TSADs) on maxillary first molars during distalization.

Medline and Scopus databases were searched up to September 2020 for randomized controlled trials (RCTs) and non-randomized prospective cohort studies on maxillary molar distalization using TSADs in patients with Class II malocclusion. After study selection, data extraction and risk of bias assessment, meta-analyses were performed for the amount of distalization, distal tipping and intrusion of first molars.

Nine studies (2 RCTs and 7 prospective studies) were included. The risk of bias of the RCTs was low to unclear. The non-randomized studies were of moderate quality. In five studies, the TSADs were placed in the infrazygomatic process while in two studies, they were placed in the buccal inter-radicular spaces, and in two studies, they were placed in the midpalatal region. The first molar distalization was 2.75 mm when buccal inter-radicular TSADs were used, but 4.07 and 4.17 mm with palatal and infrazgomatic TSADs. The palatal appliances were associated with 11.17° of distal tipping of the first molar while infrazygomatic and buccal inter-radicular TSADs resulted in 3.99° and 1.70° of tipping, respectively.

Inter-radicular TSADs resulted in less distal tipping but also in less distalization. Palatal TSAD-supported appliances showed the greatest amount of distal tipping. Further RCTs or prospective studies on the effect of various designs of TSAD-supported distalization are warranted.