Posterior crossbite is when the top back teeth bite down inside the bottom back teeth. It occurs when the top teeth or jaw are narrower than the bottom teeth and can happen on one or both sides of the mouth. The condition affects between 1% and 16% of children who only have their baby teeth. Most posterior crossbites (50% to 90%) remain even when the permanent teeth erupt. In a minority of children, the problem self-corrects.
In order to obtain a more comfortable bite, the lower jaw shifts to one side into a position that allows more teeth to come into contact. However, this shifting of the lower jaw may lead to tooth grinding, and this may lead to other dental problems including the tooth surface being worn away, abnormal growth and development of the teeth and jaws, and jaw joint problems.
Therefore, we need to find safe and effective treatments to correct posterior crossbites or expand the top back teeth, or both. One way of doing this is using orthodontic treatments. This can be more effective in children because the two halves of the roof of the mouth have not fully joined yet, so the top back teeth can be expanded more easily. Orthodontic treatments can also be used to treat posterior crossbites in adults, but they are more likely to need surgical treatments, which are not the focus of this review.
What was the research?
A systematic review of the evidence to assess the effects of different orthodontic treatments for correcting posterior crossbites
Who conducted the research?
The research was conducted by a team led by Alessandro Ugolini, on behalf of the Cochrane Oral Health Group. Paola Agostino, Alessio Signori, Armando Silvestrini-Biavati, Jayne E Harrison and Philip Riley were also on the team.
What evidence was included in the review?
Data was extracted from 15 randomised controlled trials. Nine of these studies compared fixed (always in the mouth) appliances either against different fixed appliances, or against the same fixed appliance but comparing different rates of expansion. Two studies compared a fixed appliance with a removable appliance. The remaining four studies evaluated other comparisons that were more difficult to classify.
What did the evidence say?
There is some evidence to suggest that the quad-helix (fixed) appliance may be more successful than removable expansion plates at correcting posterior crossbites and expanding the top back teeth for children with a mixture of baby and adult teeth (aged eight to 10 years). The remaining evidence we found did not allow the conclusion that any one treatment is better than another.
How good was the evidence?
The evidence presented is mostly of low to very low quality due to the small amount of available studies and issues with the way in which they were conducted.
What are the implications for dentists and the general public?
There is a very small body of low- to moderate-quality evidence to suggest that fixed quad-helix appliances may be more successful than removable expansion plates at correcting posterior crossbites and expanding the inter-molar width in children with early mixed dentition (aged eight to 10 years). The remaining evidence that we found was of very low quality and was insufficient to allow the conclusion that any one intervention is better than another for any of the outcomes in this review.
What should researchers look at in the future?
More randomised controlled trials are required to address the question of what is the best treatment for posterior crossbites in children, adolescents and adults. The studies should be large enough to detect a difference, if one exists, and should assess appropriate outcomes. We believe that ‘correction of crossbite’ is the most important outcome for all studies addressing this research question. In studies where all the crossbites were corrected (as with most studies in this review), ‘time to correction’ and ‘pain’ would be of increased importance as outcomes. Future randomised controlled trials must be well designed, well conducted and adequately delivered with subsequent reporting, including high-quality descriptions of all aspects of methodology. Reporting should conform to the Consolidated Standards of Reporting Trials (CONSORT) statement (www.consort-statement.org), which will enable accurate judgements to be made about the risk of bias and the overall quality of the evidence.
Agostino P, Ugolini A, Signori A, Silvestrini-Biavati A, Harrison JE, Riley P. Orthodontic treatment for posterior crossbites. Cochrane Database of Systematic Reviews 2014 , Issue 8 . Art. No.: CD000979. DOI: 10.1002/14651858.CD000979.pub2 .