Commentary

Orthodontic space closure is often required after extraction to close interdental spaces and improve occlusal relationships. Space closure is commonly achieved by either two-step retraction, where the canine is moved distally as a single unit, followed by the four incisors, or en masse; where the anterior six teeth are moved as one segment.1

This systematic review is the first to compare en masse against two-step retraction techniques. The PICO question was well designed with a primary outcome to assess anchorage loss and incisor retraction reported. Secondary outcome measures, treatment duration and amount of apical root resorption were provided. Inclusion/exclusion criteria were clearly reported. Six studies were excluded for language reasons and by excluding these studies it may have potentially led to some relevant papers being excluded, which is recognised as a limitation by the authors.

In total, 2092 records were identified, 1293 duplicates were removed and 1227 were excluded on initial screening. Sixty-six full-text articles were reviewed with eight studies being included in the review. Reasons for exclusion were given. Assessment of bias was carried out appropriately for each study; however, an overall quality of the findings using an approach such as GRADE does not appear to have been conducted.

Data extraction was performed independently by two reviewers, with disagreements being resolved by a third reviewer, overseen by another author. It would have been interesting to see how often the third reviewer was required.

Key characteristics of the included studies are provided in a table, which allows the reader to compare and contrast studies at ease. In the body of text, comparison between studies are made on the type of anchorage reinforcement used for space closure, as these very much differed between studies. This approach is clear and makes it easier for the reader to understand and consider each of the options. Meta-analysis was undertaken on four studies, using a random-effects model, as it was anticipated there to be a degree of heterogeneity. I2 were provided and the results of the meta-analyses were displayed in a forest-plot.

The authors report that many of the studies did not report significant differences in retraction; however, pooled data did find a significant difference, although a difference of −0.38 mm is unlikely to be considered clinically important. The authors briefly discuss how the differences in outcome measures across the studies were addressed in their review but do not expand how it may have affected the overall significance of the pooled result. En masse appears to be superior in anchorage preservation and incisor retraction, if used in conjunction with miniscrews, when compared to two-step retraction combined with conventional anchorage methods. This led the authors to recommending that en masse retraction aided with the use of miniscrews as anchorage reinforcement should be used in maximum anchorage cases. This recommendation appears to be supported by the findings of this review, however, it is based on a small number of studies. Despite these recommendations and findings, the authors report overall that en masse and two-step retraction are equally effective in orthodontic space closure.