Objective       To evaluate the changes of inter-canine width in consecutively treated extraction and non-extraction patients.       Methods      All the randomized controlled trials (RCTs)

controlled clinical trial (CCTs) and controlled before-and-after study (CBAs) about inter-canine width in consecutively treated extraction and non-extraction patients were collected by searching PubMed database

Embase

Cochrane library

VIP database

CBM database

CNKI database and Wanfang database. All the widths were measured by models

and the retrieval time was from 1990-01-01 to 2012-04-10. The assessment of methodological quality and data extraction of the included studies were performed independently by two reviewers

and meta-analysis was conducted with RevMan 5.1.4 software.       Results       A total of 12 studies involving 846 patients met the inclusion criteria. Significantly differences were found in maxillary inter-canine width (WMD=0.61 mm

95%CI=0.41 to 0.81) in the meta-analysis of CBAs

but not found in the analysis of RCTs (WMD=－0.32 mm

95%CI=－1.41 to 0.77). The mandibular inter-canine width was increased significantly for the extraction group compared with non-extraction group in the analysis of CBAs and RCTs（CBAs: WMD=0.61 mm

95%CI=0.41 to 0.81; RCTs: WMD=0.81 mm

95%CI=0.23 to 1.39).       Conclusion       Extraction treatment will not lead to narrowing of the maxillary inter-canine width

and the mandibular inter-canine width is increased more for the extraction group.