Commentary

This review addresses a clearly focused question: ‘In healthy patients with malocclusions, are lingual orthodontic appliances associated with more adverse effects than buccal appliances?’ Clinically important, patient-centred outcomes of pain, speech and eating difficulties were considered in this meta-analysis.

The authors performed a comprehensive literature search and appropriately restricted the included studies to randomised controlled trials (RCT) and controlled clinical trials (CCT) involving buccal and lingual orthodontic appliances. The authors also manually searched the leading orthodontic journals.

The authors used the Cochrane risk of bias assessment tool to assess bias in the included RCT studies, which is appropriate. However, the authors used the Newcastle-Ottawa Scale to assess the risk of bias in CCTs. The Newcastle-Ottawa Scale (NOS) is a tool recommended by the Cochrane Collaboration to assess risk of bias in observational studies (case control and cohort studies) and not necessarily controlled clinical trials.1 A more appropriate tool would have been ‘Risk Of Bias In Non-randomised Studies of Interventions (ROBINS-I). The types of non-randomised studies of interventions (NRSIs) that can be evaluated using this tool include controlled trials in which intervention groups are allocated using a method that falls short of full randomisation.2

The authors used three pre-specified criteria to arrive at eight studies (three RCTs and five CCTs) to be included in the SR. They excluded two studies because of inadequate follow-up duration (two to four weeks). Since follow-up period was not one of the pre-defined screening criteria for study selection, the decision to exclude two articles from the MA seems arbitrary. This is particularly relevant given the fact that one of the included studies3 reported that the adaptation time was 30 days for most patients on braces (100% for the labial appliance and 90% for the lingual appliance). One of the excluded studies4 had a four week follow-up and should not have been excluded based on follow-up duration alone.

As reported by the authors, there exists another MA of the same topic published in 2013 by Long et al.5 The current MA is nearly identical to the 2013 MA in terms of PICO, final studies included for MA and overall results. The study by Galvão et al. 2008, was in Portuguese and the authors took the effort to translate the article into English. Since the Galvão study was not a part of the 2013 MA, including this study in the current meta-analysis could have significantly improved the overall strength of evidence.

Practice point

  • Lingual orthodontics appliances, though aesthetically better compared to buccal appliances, are associated with higher levels of discomfort, speech difficulties and oral hygiene issues for longer duration. Informing patients about these disadvantages could help the patients make an informed decision.

  • It would be interesting to compare the treatment outcomes and adverse effects of traditional buccal appliances with other appliances that offer clear aesthetic benefits (like Invisalign® or ceramic braces).