Fourteen studies (n=747) were included.
Anchorage of molars during space closure was evaluated in seven studies (n=346): two RCTs (n=97), one prospective split-mouth RCT (n=12), one prospective split-mouth comparative study (n=20) and three retrospective comparative studies (n=217).
Anchorage in the incisor and premolar region during distal movement of molars was evaluated in seven studies (n=401): one RCT (n=23), two prospective comparative studies (n=70), one retrospective controlled study (n=210) and three retrospective comparative studies (n=98).
Two studies were classified as high quality, three as medium and nine as low quality. However, most of the studies had methodological flaws: retrospective design, inadequate selection description, small sample size, lack of accounting for confounding variables, lack of method error analysis and lack of blinded outcome assessment.
Anchorage of molars during space closure after premolar extractions.
Two RCTs evaluated anchorage loss with and without laceback ligatures but reported different results: one reported a significantly larger anchorage loss with the ligatures, while the other reported no significant differences between treatments. The other five studies evaluated different anchorage systems, and the authors stated that this and the differences in study design made it impossible to compare systems.
Anchorage in the incisor and premolar region during distal movement of molars. The authors reported that anchorage loss of the incisors or premolars ranged from 0.2 to 2.2 mm, and the ratio of anchorage loss to distal movement ranged from 0.2 to 0.8 mm.