Orthodontic treatment for posterior crossbites
Abstract
Background
A posterior crossbite occurs when the top back teeth bite inside the bottom back teeth. When it affects one side of the mouth, the lower jaw may have to move to one side to allow the back teeth to meet together. Several treatments have been recommended to correct this problem. Some treatments widen the upper teeth while others are directed at treating the cause of the posterior crossbite (e.g. breathing problems or sucking habits). Most treatments have been used at each stage of dental development. This is an update of a Cochrane review first published in 2001.
Objectives
To assess the effects of orthodontic treatment for posterior crossbites.
Search methods
We searched the following electronic databases: the Cochrane Oral Health Group's Trials Register (to 21 January 2014), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2014, Issue 1), MEDLINE via OVID (1946 to 21 January 2014), and EMBASE via OVID (1980 to 21 January 2014). We searched the US National Institutes of Health Trials Register and the World Health Organization (WHO) Clinical Trials Registry Platform for ongoing trials. We placed no restrictions on the language or date of publication when searching the electronic databases.
Selection criteria
Randomised controlled trials (RCTs) of orthodontic treatment for posterior crossbites in children and adults.
Data collection and analysis
Two review authors, independently and in duplicate, screened the results of the electronic searches, and extracted data and assessed the risk of bias of the included studies. We attempted to contact the first named authors of the included studies for missing data and for clarification. We used risk ratios (RR) and 95% confidence intervals (CIs) to summarise dichotomous (event) data, and mean differences (MD) with 95% CIs to summarise continuous data. We performed meta‐analyses using fixed‐effect models (we would have used random‐effects models if we had included four or more studies in a meta‐analysis) when comparisons and outcomes were sufficiently similar.
Main results
We included 15 studies, of which two were at low risk of bias, seven were at high risk of bias and six were unclear.
Fixed appliances with mid‐palatal expansion
Nine studies tested fixed appliances with mid‐palatal expansion against each other. No study reported a difference between any type of appliance.
Fixed versus removable appliances
Fixed quad‐helix appliances may be 20% more likely to correct crossbites than removable expansion plates (RR 1.20; 95% CI 1.04 to 1.37; two studies; 96 participants; low‐quality evidence).
Quad‐helix appliances may achieve 1.15 mm more molar expansion than expansion plates (MD 1.15 mm; 95% CI 0.40 to 1.90; two studies; 96 participants; moderate‐quality evidence).
There was insufficient evidence of a difference in canine expansion or the stability of crossbite correction.
Very limited evidence showed that both fixed quad‐helix appliances and removable expansion plates were superior to composite onlays in terms of crossbite correction, molar and canine expansion.
Other comparisons
Very limited evidence showed that treatments were superior to no treatment, but there was insufficient evidence of a difference between any active treatments.
Authors' conclusions
There is a very small body of low‐ to moderate‐quality evidence to suggest that the quad‐helix appliance may be more successful than removable expansion plates at correcting posterior crossbites and expanding the inter‐molar width for children in the early mixed dentition (aged eight to 10 years). The remaining evidence 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.
PICOs
Plain language summary
Orthodontic treatment for posterior crossbites
Review question
We conducted this review to assess the effects of different orthodontic treatments for correcting posterior crossbites.
Background
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.
Study characteristics
Authors from the Cochrane Oral Health Group carried out this review update of existing studies and the evidence is current up to 21 January 2014. It includes 15 studies published from 1984 to 2013. 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.
Key results
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.
Quality of 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.
Authors' conclusions
Summary of findings
| Fixed appliances compared with other fixed appliances for treating posterior crossbites | ||||||
| Patient or population: Children with posterior crossbites (adults would be included in the review but no studies with adults were found) Settings: Typically university orthodontic/dental clinics Intervention: Fixed appliance Comparison: The same fixed appliance attached differently or expanded at different speeds or a different fixed appliance | ||||||
| Outcomes | Illustrative comparative risks (95% CI) | Relative effect | No of participants | Quality of the evidence | Comments | |
| Assumed risk | Corresponding risk | |||||
| Group A | Group B | |||||
| Molar expansion (mm) (rapid expansion) banded Hyrax (tooth borne) versus bonded Hyrax (tooth/tissue borne) | N/A | N/A | N/A | 53 | ⊕⊝⊝⊝ | 2 studies (1 high risk of bias; 1 unclear), which were not possible to pool in a meta‐analysis due to no reporting of variance in 1 study. Imprecision due to low sample sizes. Different timings of follow‐up after completion of expansion. Both studies reported no difference in molar expansion |
| Molar expansion (mm) (3 months after completion of expansion phase) (rapid expansion) tooth‐tissue borne (Haas) versus tooth borne (Hyrax) | The mean expansion ranged across the Haas groups from | The mean expansion in the Hyrax groups was | N/A | 27 | ⊕⊝⊝⊝ | 2 studies at unclear risk of bias with serious inconsistency (I2 = 94%) and imprecision due to low sample size |
| N/A | N/A | N/A | N/A | N/A | N/A | The remaining comparisons were all single studies (Additional Table 1). The quality of the evidence (GRADE) for all comparisons and outcomes in Additional Table 1 is ⊕⊝⊝⊝ very low (all at unclear or high risk of bias with imprecision due to low sample sizes). None of these studies showed a statistically significant difference for any outcome |
| CI: confidence interval; N/A: not applicable. | ||||||
| GRADE Working Group grades of evidence | ||||||
| Fixed appliances compared with removable appliances for treating posterior crossbites | ||||||
| Patient or population: Children with posterior crossbites (adults would be included in the review but no studies with adults were found) Settings: Public Dental Health Service and university orthodontic/dental clinics Intervention: Fixed appliance Comparison: Removable appliance | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect | No of participants | Quality of the evidence | Comments | |
| Assumed risk | Corresponding risk | |||||
| Removable ‐ slow expansion (expansion plate) | Fixed ‐ slow expansion (quad‐helix) | |||||
| Crossbite correction (Follow‐up after retention period, therefore, it was variable) | 833 per 1000 | 1000 per 1000 | RR 1.2 (1.04 to 1.37) | 96 | ⊕⊕⊝⊝ | 2 studies at low risk of bias, but with serious inconsistency (I2 = 68%) and imprecision due to low sample size |
| Molar expansion (mm) (Follow‐up after retention period, therefore, it was variable) | The mean expansion ranged across the removable appliance groups from 3.09 to 3.5 mm | The mean expansion in the fixed appliance group was | N/A | 96 | ⊕⊕⊕⊝ | 2 studies at low risk of bias, but with imprecision due to low sample size |
| Canine expansion (mm) (Follow‐up after retention period, therefore it was variable) | The mean expansion ranged across the removable appliance groups from 1.43 to 2.7 mm | The mean expansion in the fixed appliance group was | N/A | 96 | ⊕⊕⊝⊝ | 2 studies at low risk of bias, but with serious inconsistency (I2 = 91%) and imprecision due to low sample size |
| N/A | N/A | N/A | N/A | N/A | N/A | 1 of the 2 studies in this comparison also measured stability of crossbite correction (relapse 12 months after correction). No statistically significant difference was found (Additional Table 2) The other study also compared the fixed and removable appliances to composite onlays for crossbite correction, molar expansion and canine expansion. All results were statistically significant in favour of fixed and removable appliances (Additional Table 2) The quality of the evidence (GRADE) for all comparisons and outcomes in Additional Table 2 is ⊕⊝⊝⊝ very low |
| *The basis for the assumed risk is the removable group event rate. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). | ||||||
| GRADE Working Group grades of evidence | ||||||
| Other comparisons for treating posterior crossbites | ||||||
| Patient or population: Children with posterior crossbites (adults would be included in the review but no studies with adults were found) Settings: Public Dental Health Service and university/hospital orthodontic/dental clinics | ||||||
| Outcomes | Illustrative comparative risks (95% CI) | Relative effect | No of participants | Quality of the evidence | Comments | |
| Assumed risk | Corresponding risk | |||||
| Group A | Group B | |||||
| N/A | N/A | N/A | N/A | N/A | N/A | The comparisons were all single studies (Additional Table 3). The quality of the evidence (GRADE) for all comparisons and outcomes in Additional Table 3 is ⊕⊝⊝⊝ very low (all at high risk of bias with imprecision due to low sample sizes)
|
| GRADE Working Group grades of evidence CI: confidence interval; N/A: not applicable. | ||||||
Background
Description of the condition
Posterior crossbite is the term used to describe the situation when the top back teeth bite inside the bottom back teeth. A posterior crossbite occurs when the top teeth or jaw are narrower than the bottom teeth and can happen on one (unilateral) or both (bilateral) sides of the mouth. The prevalence of posterior crossbites is between 1% and 16% of children who only have their baby teeth, and is likely to be higher in white populations compared with children of African or Asian ethnicity (Malandris 2004). Most posterior crossbites (50% to 90%) persist when the permanent teeth erupt, though, in a minority of children, the malocclusion self corrects.
A functional posterior crossbite occurs when there is an interference between two or more teeth when an individual closes their jaws together. In order to obtain a more comfortable bite, the mandible (lower jaw) shifts to one side into a position that allows more teeth to come into contact. However, this displacement may increase the likelihood of the individual developing bruxism (tooth grinding), which may lead to other dental problems including the tooth surface being worn away (Malandris 2004), abnormal growth and development of the teeth and jaws, and jaw joint problems.
While it is unlikely that young children with a posterior crossbite will experience any pain or have problems with chewing, there has been concern that the abnormal movement of the lower jaw associated with a crossbite could potentially have long‐term effects on the growth and development of the teeth and jaws. The strain on the jaw muscles and joints due to the abnormal movement and position of the lower jaw may lead to skeletal facial asymmetries that can be corrected during adulthood only by means of a combination of orthodontics and maxillofacial surgery.
Some studies have reported a correlation between posterior crossbite with a shift on closure and temporomandibular joint problems in later life, for example pain, clicking or locking of the jaw joints. Such problems have many causes but studies of teenagers and adults have shown that some people with a crossbite may have an increased risk of developing jaw joint problems and show more signs and symptoms of these problems (Egermark 1990; McNamara 1997; Ninou 1994; O'Bryn 1995; Pullinger 1993). However, some more recent studies have been less conclusive regarding an association between posterior crossbites and jaw problems (Gesch 2004; Iodice 2013; Thilander 2002; Thilander 2012).
A posterior crossbite may develop or improve at any time from when the deciduous (baby) teeth come into the mouth to when the permanent (adult) teeth come through (Heikinheimo 1987; Kurol 1992; Leighton 1966; Thilander 1984). It is unclear what causes posterior crossbites but they may be due to skeletal, soft tissue, dental or respiratory factors, or develop as the result of a habit (e.g. thumb sucking) or some pathology (Bresolin 1983; Cheng 1988; Modeer 1982; Ogaard 1994; Subtelny 1980).
Description of the intervention
As described above, a posterior crossbite may self correct but, as self correction occurs in only a very small minority of cases, treatment of this malocclusion can be recommended. Treatment of a posterior crossbite usually involves expansion of the maxillary (upper jaw) arch, removal of any occlusal interferences and elimination of the functional displacement of the mandible.
Maxillary expansion treatment initiated during the early mixed dentition stage (children younger than eight years of age) may require the use of lower forces to achieve expansion of the upper arch because the mid‐line bony suture has not yet fused. However, obtaining co‐operation with treatment may be more difficult in younger children and treatment may be complicated by the loss of deciduous teeth. In older children (aged 12 years and above) who are in the early permanent dentition, greater forces may be required to achieve maxillary expansion. Maxillary expansion can be achieved using either fixed or removable appliances and expansion can be either rapid or slow. Expansion of the top jaw is termed 'rapid' when expansion takes place at a rate of 0.5 mm per day, and 'slow' when expansion takes place at a rate of 0.5 mm per week. Braces that can bring about this expansion are fixed to the back teeth by either metal bands around the individual teeth (banded rapid/slow maxillary expansion) or acrylic splints over several teeth (bonded rapid/slow maxillary expansion) joined by a wire framework attached to a screw in the mid‐line that can be opened to expand the top jaw.
Removal of occlusal interferences involves grinding of teeth (usually deciduous teeth) to enable the jaws to bite together in a more normal position. The reported success rate of this approach varied widely between 27% and 64% (Kennedy 2005; Lindner 1989). Alternatively, composite onlays can be placed to prevent the jaw from shifting when interferences exist.
Where functional displacement of the mandible is associated with reversible causes such as non‐nutritive sucking habits (sucking on a dummy, thumb, finger(s), etc.), eliminating the causal behaviour is a desirable adjunct to orthodontic treatment.
How the intervention might work
Expansion of the maxillary arch can be achieved through use of either fixed or removable appliances (seeAppendix 1 for a description of appliances). These have expansion screws that are adjusted during treatment to increase the width of the maxillary arch. Expansion may be either rapid (one‐quarter turn of the expansion screw one or two times per day, giving 0.5 mm expansion per day) over two to six weeks or slow (one‐quarter turn twice per week, giving 0.5 mm expansion per week) over six to 12 weeks. Overexpansion may be appropriate to allow for some relapse after the appliance is removed. The use of maxillary expansion at the stage of the early mixed dentition may also have the benefit of reducing crowding of the permanent dentition.
Orthodontic appliances may also be used to correct the sideways displacement of the mandible, which may reduce the pressure on the temporomandibular joint.
Why it is important to do this review
A crossbite is a common transverse feature seen in malocclusions in the posterior region of the dental arch. There is still debate about the optimum timing of orthodontic treatment, the use of either fixed or removable appliances, and the type of appliance that leads to the best outcomes for the person. This updated systematic review will summarise the evidence available from randomised controlled trials to inform treatment decision making. The Cochrane Oral Health Group recently carried out a prioritisation exercise for their portfolio of orthodontic reviews, and this review was ranked in the top 10 most important orthodontic reviews by an international panel of oral health professionals, the majority of whom were extremely experienced and internationally renowned orthodontists.
This is an update of a Cochrane review first published in 2001.
Objectives
To assess the effects of orthodontic treatment for posterior crossbites.
Methods
Criteria for considering studies for this review
Types of studies
We included randomised controlled trials (RCTs) of parallel design that assessed orthodontic treatments to correct a posterior crossbite or expand the top back teeth, or both. We included studies irrespective of language or publication status.
Types of participants
We included RCTs of children and adults with a posterior crossbite, without a Class III skeletal relationship, cleft lip or palate (or both) or other syndrome associated with craniofacial anomalies.
Types of interventions
We included studies of any orthodontic or dentofacial orthopaedic (not surgical) treatment used to correct posterior crossbites or expand the top back teeth, or both, when compared against another such treatment or no treatment.
Types of outcome measures
Primary
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Correction of the posterior crossbite.
Secondary
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Expansion of the upper jaw/teeth measured as changes in the width between the molars or canines, or both.
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Stability of crossbite correction.
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Signs and symptoms of temporomandibular joint dysfunction (e.g. pain, clicking, locking of the jaw joints, problems eating).
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Signs and symptoms of respiratory disease (e.g. mouth breathing, nasal airway resistance).
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Quality of life (using any validated measurement tool).
Search methods for identification of studies
For the identification of studies included or considered for this review, we developed detailed search strategies for each database searched. These were based on the search strategy developed for MEDLINE (OVID) but revised appropriately for each database. The search strategy used a combination of controlled vocabulary and free‐text terms and was linked with the Cochrane Highly Sensitive Search Strategy (CHSSS) for identifying RCTs in MEDLINE: sensitivity maximising version (2008 revision) as referenced in Chapter 6.4.11.1 and detailed in box 6.4.c of the Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 (updated March 2011) (Higgins 2011). Details of the MEDLINE search are provided in Appendix 2. The search of EMBASE was linked to the Cochrane Oral Health Group filter for identifying RCTs.
Electronic searches
We searched the following electronic databases:
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the Cochrane Oral Health Group's Trials Register (to 21 January 2014) (Appendix 3);
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the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, 2014, Issue 1) (Appendix 4);
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MEDLINE via OVID (1946 to 21 January 2014) (Appendix 2)
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EMBASE via OVID (1980 to 21 January 2014) (Appendix 5).
We manually checked all the references lists of the included studies to identify any additional studies.
We placed no restrictions on the language or date of publication when searching the electronic databases.
Searching other resources
We searched the following databases for ongoing trials (seeAppendix 6 for the search strategy):
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US National Institutes of Health Trials Register (clinicaltrials.gov) (to 21 January 2014);
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The WHO Clinical Trials Registry Platform (apps.who.int/trialsearch/default.aspx) (to 21 January 2014).
We handsearched the following journals from 1970 to 2012:
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European Journal of Orthodontics;
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American Journal of Orthodontics and Dentofacial Orthopedics;
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Orthodontics and Craniofacial Research;
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The Angle Orthodontist.
In the previous version of this review we also handsearched:
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British Journal of Orthodontics;
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Journal of Orthodontics.
We also searched personal references. We contacted the investigators of the included studies by email to ask for additional details of their trials and for any information they may have about any further published and unpublished trials.
Data collection and analysis
Selection of studies
Two review authors screened the titles and abstracts of the results of the searches, independently and in duplicate. We obtained full‐text copies of all studies that appeared to meet the inclusion criteria, and of all those that were unclear due to insufficient information in the title or abstract, or both. Two review authors assessed the full‐text papers independently and in duplicate in order to ensure that they met the inclusion criteria. We contacted study authors for clarification or missing information where necessary and possible. We resolved any disagreements by discussion. A member of The Cochrane Collaboration translated any non‐English language studies. We recorded any studies that did not meet the inclusion criteria at this stage, along with the reasons, in the Characteristics of excluded studies table.
Data extraction and management
Two review authors extracted data from the included studies, independently and in duplicate, using a piloted data extraction form. We resolved any disagreements through discussion. We contacted study authors for clarification or missing information where necessary and possible.
We entered the following extracted data into the Characteristics of included studies table.
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Study design, location, number of centres, recruitment period, funding, experience level of clinician.
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Inclusion and exclusion criteria, age, gender, number of participants randomised to each group, number of participants evaluated.
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Details of the type of intervention/comparator, timing, duration.
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Details of the outcomes reported, including method of assessment, and time(s) assessed.
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Sample size calculations, any other notable details.
Assessment of risk of bias in included studies
Two review authors assessed the risk of bias of each included study, independently and in duplicate, following the domain‐based two‐part tool described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). We contacted study authors for clarification or missing information where necessary and possible. We compared our assessments and discussed and resolved any inconsistencies between the review authors.
We assessed the following six domains of risk of bias for each included study.
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Random sequence generation (selection bias).
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Allocation concealment (selection bias).
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Blinding of outcome assessment (detection bias).
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Incomplete outcome data (attrition bias).
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Selective reporting (reporting bias).
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Other bias.
We did not consider the blinding of participants and personnel (performance bias) as the interventions being compared in all studies were different and it would not have been possible to blind them as to which group they were allocated. Therefore, a risk of performance bias is possible in all of the included studies. However, it should be possible for outcome assessors to be blinded if measuring casts/models or radiographs or both, if the appliances had been removed. Therefore, we focused on assessing the risk of detection bias.
We completed a 'Risk of bias' table for each included study. For each of the above domains, we described what was reported to have happened in the study and this formed the rationale for our corresponding judgement of 'low risk' of bias, 'high risk' of bias or 'unclear risk' of bias for each domain.
We categorised overall risk of bias in any included study according to the following.
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Low risk of bias (plausible bias unlikely to seriously alter the results) if all key domains were assessed as at low risk of bias.
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Unclear risk of bias (plausible bias that raises some doubt about the results) if one or more key domains were assessed as at unclear risk of bias.
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High risk of bias (plausible bias that seriously weakens confidence in the results) if one or more key domains were assessed as at high risk of bias.
We have presented the results of our risk of bias assessments graphically.
Measures of treatment effect
For dichotomous outcomes (e.g. posterior crossbite corrected or not), we expressed the estimate of treatment effect as risk ratios (RR) with 95% confidence intervals (CI). For continuous outcomes (e.g. width between the molars), we used the means and standard deviations (SD) reported in the studies to calculate mean differences (MD) with 95% CIs.
Dealing with missing data
Where possible, we attempted to contact the author(s) of studies to obtain missing data or for clarification. We performed the analyses using only the available data (ignoring missing data); however, we intended to use methods for estimating missing SDs as described in Section 7.7.3 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011), if appropriate. We did not use any further statistical methods or carry out any further imputation to account for missing data.
Assessment of heterogeneity
Where meta‐analyses were performed, we assessed heterogeneity by visual inspection of the forest plots. If there was a lack of overlap of the CIs, we considered heterogeneity to be present. We assessed heterogeneity statistically by means of a Chi2 test, where a P value < 0.1 indicated statistically significant heterogeneity. We quantified heterogeneity using the I2 statistic. An approximate guide to the interpretation of the I2 statistic given in the Cochrane Handbook for Systematic Reviews of Interventions is: 0% to 40% might not be important; 30% to 60% may represent moderate heterogeneity; 50% to 90% may represent substantial heterogeneity and 75% to 100% may represent considerable heterogeneity (Higgins 2011).
Assessment of reporting biases
We have already described the assessment of within‐study reporting bias in the section Assessment of risk of bias in included studies.
In order to assess reporting biases that can occur when the publishing (or not publishing) of research findings is related to the results (e.g. a study with a non‐significant result may not be published), we would have created a funnel plot to check for asymmetry (Egger 1997; Higgins 2011), provided there were more than 10 studies in a meta‐analysis.
Data synthesis
We only carried out a meta‐analysis when studies of similar comparisons reported the same outcomes. We combined MDs for continuous outcomes, and RRs for dichotomous outcomes, using a fixed‐effect model when there were fewer than four studies, or a random‐effects model when there were four or more studies. We summarised single‐study comparisons in additional tables.
Subgroup analysis and investigation of heterogeneity
In future updates, if sufficient data are available for each comparison and outcome, we will conduct subgroup analyses according to age, gender and the degree of severity of maxillary transversal deficiency.
Sensitivity analysis
In future updates, if sufficient data are available for each comparison and outcome, we will assess the robustness of the results by excluding studies at high and unclear risk of bias from the meta‐analyses.
Presentation of main results
We produced 'Summary of findings' tables following GRADE methods (GRADE 2004), and using GRADEPro software. We assessed the quality of the body of evidence by considering the overall risk of bias of the included studies, the directness of the evidence, the inconsistency of the results, the precision of the estimates and the risk of publication bias. We categorised the quality of the body of evidence of each of the main outcomes for each comparison as high, moderate, low or very low.
Results
Description of studies
Results of the search
The electronic searches retrieved 779 references to studies. After removing duplicates, this was reduced to 515. We obtained two additional reports through other sources. After examination of the titles and abstracts of these references, we discarded all but 33 with no further assessment. We obtained full‐text copies of these potentially relevant studies and we excluded 16 of them at this stage (17 references). However, we did not record 14 (15 references) of these in the table of excluded studies, as they were clearly not eligible upon examining the full text. We linked two of the remaining 16 articles together under a single study reference. Therefore, 15 studies met the inclusion criteria for this review. This process is presented as a flow chart in Figure 1.
Study flow diagram.
Included studies
Characteristics of the trial design and setting
Fifteen studies met the inclusion criteria and were included in this review (seeCharacteristics of included studies tables).
All studies, by necessity, were of parallel design. Nine studies (Asanza 1997, USA; Garib 2005, Brazil; Kilic 2008, Turkey; Lagravere 2010, Canada; Lippold 2013, Germany; Martina 2012, Italy; Mossaz‐Joelson 1989, Switzerland; Oshagh 2012, Iran; Ramoglu 2010, Turkey) were carried out in university orthodontics departments. One of these studies stated that the clinicians were two specialist orthodontists (Lippold 2013), but in the remaining eight studies it was unclear who the clinicians undertaking the treatment were and what experience or qualifications they had. There were three multicentre studies: one was carried out in a general hospital and a university dental hospital in the UK by experienced orthodontists (McNally 2005); one was carried out in two public dental health service clinics and one university orthodontic department in Sweden by experienced general practitioners under the supervision of specialist orthodontists (Petrén 2008); and one study was carried out in three university orthodontic clinics and one private practice in Brazil, but it was unclear who the clinicians undertaking the treatment were and what experience or qualifications they had (Oliveira 2004). One study took place in a basic dental unit in Brazil, conducted by the local university, with treatment carried out by one specialist orthodontist with over 10 years of experience (Godoy 2011). Participants in another study were treated in a private orthodontic practice in the USA by a board‐certified orthodontist with 27 years of experience (Lamparski 2003). The remaining study was carried out in Sweden by the public dental health service, but the experience of the orthodontist was not reported (Thilander 1984).
Characteristics of the participants
Seven studies enrolled participants with either a unilateral or bilateral crossbite malocclusion (Garib 2005; Martina 2012; McNally 2005; Mossaz‐Joelson 1989; Oliveira 2004; Petrén 2008; Ramoglu 2010), two studies included only participants with a unilateral crossbite (Godoy 2011; Lippold 2013), two studies included only participants with a bilateral crossbite (Kilic 2008; Oshagh 2012), while the remaining four studies did not specify the type of crossbite that participants presented with at study entry (Asanza 1997; Lagravere 2010; Lamparski 2003; Thilander 1984).
One study enrolled only children in the permanent dentition (Garib 2005), two studies enrolled only children in the mixed dentition (Godoy 2011; Petrén 2008), four studies enrolled children in either the mixed or permanent dentition (Lamparski 2003; Martina 2012; Oliveira 2004; Ramoglu 2010), one study enrolled children in either the late deciduous or early mixed dentition (Lippold 2013), and seven studies did not state the stage of dental development of the children at study entry (Asanza 1997; Kilic 2008; Lagravere 2010; McNally 2005; Mossaz‐Joelson 1989; Oshagh 2012; Thilander 1984).
The age range of participants was from five to 16 years old with variations between studies, but almost homogeneous within individual studies.
Characteristics of the interventions and comparisons
Six of the included studies evaluated two different types of fixed appliances for rapid palatal expansion (Asanza 1997; Garib 2005; Kilic 2008; Lagravere 2010; Lamparski 2003; Oliveira 2004), one study compared two different fixed appliances for slow palatal expansion (Mossaz‐Joelson 1989), and two studies compared the effects of fixed appliances used for differing rates of expansion (Martina 2012; Ramoglu 2010).
Two studies compared a fixed appliance with a removable appliance for slow expansion (Godoy 2011; Petrén 2008), and the remaining studies evaluated other comparisons that were more difficult to classify (see below) (Lippold 2013; McNally 2005; Oshagh 2012; Thilander 1984).
SeeAppendix 1 for a description of appliances.
1. Fixed appliance with mid‐palatal expansion
Rapid expansion
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Banded Hyrax (tooth borne) versus bonded Hyrax (tooth/tissue borne) (Asanza 1997; Kilic 2008).
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Tooth‐tissue borne Haas versus tooth borne Hyrax (Garib 2005; Oliveira 2004).
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Hyrax tooth‐borne expander versus bone‐anchored expander (Lagravere 2010).
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Four‐point banded (Hyrax) versus two‐point banded (Hyrax) (Lamparski 2003).
Slow expansion
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Bonded Minne versus banded Minne appliances (Mossaz‐Joelson 1989).
Different rates of expansion
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Slow versus rapid expansion (two‐band palatal expanders) (Martina 2012).
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Semi‐rapid versus rapid expansion (splint type tooth‐ and tissue‐borne modified bonded appliances) (Ramoglu 2010).
2. Fixed versus removable
Slow expansion
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Quad‐helix versus expansion plate (Godoy 2011; Petrén 2008).
3. Other comparisons
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Early treatment with fixed bonded Hyrax appliance followed by U‐bow activator therapy versus no treatment (Lippold 2013).
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Grinding ‐ occlusal grinding in the primary dentition (aged five years old) with/without an upper removable expansion appliance in the mixed dentition versus no treatment (Thilander 1984).
Slow expansion
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Quad‐helix plus multi‐bracket versus expansion arch plus multi‐bracket (McNally 2005).
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Conventional mid‐line expansion screw versus spring‐loaded expansion screw (Oshagh 2012).
Characteristics of the outcomes
The primary outcome of this review, correction of the posterior crossbite, was reported by three studies (Godoy 2011; Petrén 2008; Thilander 1984). In 11 studies, the correction of crossbite is taken for granted because it was the end point of the treatment and the point at which activation of the appliances ceased (Asanza 1997; Garib 2005; Kilic 2008; Lagravere 2010; Lamparski 2003; Lippold 2013; Martina 2012; McNally 2005; Oliveira 2004; Oshagh 2012; Ramoglu 2010). In the remaining study, no data were provided on whether the expansion obtained by these appliances did correct the participants' crossbite (Mossaz‐Joelson 1989).
All included studies, with the exception of Thilander 1984, reported expansion of the upper jaw/teeth measured as changes in the width between the molars or canines (or both). Two studies assessed stability of crossbite correction (Godoy 2011; Mossaz‐Joelson 1989).
None of the included studies reported any of the other outcomes of this review.
Excluded studies
We excluded two studies from this review. One of these studies was excluded because it included a subset of participants from one of the included studies (Petrén 2008), plus other participants and matched controls (Petrén 2011). The other study was excluded after attempting to contact the authors because the participants were only described as having maxillary deficiency, rather than crossbite (Weissheimer 2011).
Risk of bias in included studies
We have based our assessment of risk of bias on the reports of the included studies because we could not access copies of the study protocols. Where the reports were unclear on aspects of the methodology, we attempted to contact the study authors to obtain clarification or missing information. We present the results of our risk of bias assessment graphically in Figure 2.
Risk of bias summary: review authors' judgements about each risk of bias item for each included study.
Allocation
Sequence generation
Seven studies described adequate methods of sequence generation and we judged them to be at low risk of bias for this domain: three used a table of random numbers (Lagravere 2010; Oliveira 2004; Oshagh 2012); two used block randomisation (Lippold 2013; Martina 2012); one used a method of drawing lots (Godoy 2011); and the remaining study used a similar method involving opaque sealed envelopes (Petrén 2008).
One study used random number tables to allocate the first half of the participants and then allocated the remaining half to receive the alternative treatment to those in the initial allocation (McNally 2005). Therefore, only half the participants were truly randomly allocated and we judged this study to be at high risk of bias for this domain.
The remaining seven studies stated only that participants were randomly allocated and we were unable to obtain further details from the authors, so we judged these studies to be at unclear risk of bias for this domain (Asanza 1997; Garib 2005; Kilic 2008; Lamparski 2003; Mossaz‐Joelson 1989; Ramoglu 2010; Thilander 1984).
Allocation concealment
Four studies described adequate methods of allocation concealment and we judged them to be at low risk of bias for this domain (Godoy 2011; Martina 2012; Oliveira 2004; Petrén 2008).
The method of sequence generation carried out in one study, as described above, would allow for the prediction of the allocation of half of the participants, and therefore we judged this study to be at high risk of bias for this domain (McNally 2005).
The remaining 10 studies did not mention any method of allocation concealment, so we judged these studies to be at unclear risk of bias for this domain (Asanza 1997; Garib 2005; Kilic 2008; Lagravere 2010; Lamparski 2003; Lippold 2013; Mossaz‐Joelson 1989; Oshagh 2012; Ramoglu 2010; Thilander 1984).
Blinding of outcome assessment (detection bias)
We did not consider the blinding of participants and personnel (performance bias) as the interventions being compared in all studies were different and it would not have been possible to blind them as to which group they were allocated. Therefore, a risk of performance bias is possible in all of the included studies.
However, it would have been possible for an independent blinded person to perform the clinical, model and radiographic assessments. Therefore, we have focused on whether the included studies minimised the possible effects of detection bias.
Three studies clearly stated that the measurement of outcomes was blinded, so we judged these studies to be at low risk of detection bias (Godoy 2011; Martina 2012; Petrén 2008).
The remaining 12 studies did not mention blinding, even though it was feasible that it could have occurred, and, therefore, we judged these studies to be at unclear risk of bias for this domain.
Incomplete outcome data
We judged eight studies to be at low risk of attrition bias as they either clearly described drop‐outs (which were for similar reasons and in similar numbers per group), or the numbers of participants stated in the analyses were the same as those randomised, or an intention‐to‐treat analysis included all randomised participants (Asanza 1997; Godoy 2011; Kilic 2008; Lippold 2013; McNally 2005; Oliveira 2004; Petrén 2008; Ramoglu 2010).
One study clearly described the numbers and reasons for drop‐out but the high attrition rate (48% per group) meant that, if the missing participants had higher mean scores in one group than the other, as the attrition rate increased, so would over/understatement of the mean difference (Martina 2012). In another study, the attrition rate was very different between the treated group (3%) and the untreated group (18%) (Thilander 1984). Therefore, we judged these two studies to be at high risk of attrition bias.
The remaining five studies did not report whether or not there were any drop‐outs and it was unclear how many participants were included in the outcome assessment. Therefore, we judged these studies to be at unclear risk of attrition bias (Garib 2005; Lagravere 2010; Lamparski 2003; Mossaz‐Joelson 1989; Oshagh 2012).
Selective reporting
Eleven studies reported all outcome measures described in the corresponding methods sections in full and we assessed them as being at low risk of reporting bias (Garib 2005; Godoy 2011; Kilic 2008; Lagravere 2010; Martina 2012; McNally 2005; Mossaz‐Joelson 1989; Oliveira 2004; Petrén 2008; Ramoglu 2010; Thilander 1984).
We judged the remaining four studies to be at high risk of reporting bias for the following reasons: no measure of variance reported (Asanza 1997; Lippold 2013); one outcome was not reported by group and the other was reported without a measure of variance (Lamparski 2003); and the results were so inadequately reported that we were unable to use any data (Oshagh 2012).
Other potential sources of bias
In one study, there were imbalances between the treatment groups in terms of numbers of participants and gender, possibly indicating a problem with the randomisation (Oshagh 2012). We assessed this study as being at high risk of bias for this domain. We did not identify any other potential sources of bias in any of the remaining 14 studies and, therefore, we judged them to be at low risk of bias for this domain.
Overall risk of bias
-
Two studies were at low risk of bias (Godoy 2011; Petrén 2008).
-
Seven studies were at high risk of bias (Asanza 1997; Lamparski 2003; Lippold 2013; Martina 2012; McNally 2005; Oshagh 2012; Thilander 1984).
-
Six studies were at unclear risk of bias (Garib 2005; Kilic 2008; Lagravere 2010; Mossaz‐Joelson 1989; Oliveira 2004; Ramoglu 2010).
Effects of interventions
See: Summary of findings for the main comparison Fixed appliances compared with other fixed appliances for treating posterior crossbites; Summary of findings 2 Fixed appliances compared with removable appliances for treating posterior crossbites; Summary of findings 3 Other comparisons for treating posterior crossbites
SeeAppendix 1 for a description of appliances.
1. Fixed appliance with mid‐palatal expansion
Rapid expansion
Banded Hyrax (tooth borne) versus bonded Hyrax (tooth/tissue borne)
We included two studies, one at unclear and one at high risk of bias, analysing 53 participants, in this comparison (Asanza 1997; Kilic 2008). Due to problems with reporting of the data in one study (Asanza 1997), we were unable to combine the results in a meta‐analysis. Both studies assessed molar expansion and reported no statistically significant difference (Table 1). One study measured the outcomes three months after completion of the expansion phase (Asanza 1997), while the other study measured it one week after completion of the expansion phase (Kilic 2008).
| Study | Outcome | Group A | Group B | Results |
| Molar expansion (3 months after completion of expansion phase) | Hyrax banded: Mean 6 mm (min 4.3 mm ‐ max 7.2 mm) | Hyrax bonded: Mean 5.9 mm (min 3.2 mm ‐ max 7.7 mm) | P value = NS (as reported in the study ‐ no SD reported) | |
| Molar expansion (1 week after completion of expansion phase) | Hyrax banded: Mean 7.67 mm (SD 1.99) | Hyrax bonded: Mean 7.31 mm (SD 1.45) | MD 0.36 (95% CI ‐0.72 to 1.44) P value = 0.51 | |
| Molar expansion (6 months after completion of expansion phase) | Hyrax tooth‐borne expander: Mean 5.83 mm (SD 1.54) | Bone‐anchored expander: Mean 5.75 mm (SD 1.98) | MD 0.08 (95% CI ‐1.00 to 1.16) P value = 0.88 | |
| Molar expansion (12 months after completion of expansion phase) | Hyrax tooth‐borne expander: Mean 4.24 mm (SD 1.69) | Bone‐anchored expander: Mean 4.03 mm (SD 1.49) | MD 0.21 (95% CI ‐0.77 to 1.19) P value = 0.67 | |
| Molar expansion (3 months after completion of expansion phase) | 4‐point expansion appliance (Hyrax): Not reported by group | 2‐point expansion appliance: Not reported by group | P value = "No significant differences were found" | |
| Canine expansion (3 months after completion of expansion phase) | 4‐point expansion appliance (Hyrax): Mean 3.034 mm | 2‐point expansion appliance: Mean 1.7 mm | P value = 0.331 (as reported in the study ‐ no SD reported) | |
| Molar expansion (7 months after start of treatment) | Slow maxillary expansion: Mean 6.3 mm (SD 2.1) | Rapid maxillary expansion: Mean 5.7 mm (SD 1.6) | MD 0.60 (95% CI ‐0.85 to 2.05) P value = 0.42 | |
| Molar expansion (7‐15 weeks after start of treatment) | Bonded Minne: Mean 7.9 mm (SD 1.5) | Banded Minne: Mean 8.3* mm (SD 1.1) | P value = NS (as reported in the study ‐ number of participants included in analysis not reported) | |
| Canine expansion (7‐15 weeks after start of treatment) | Bonded Minne: Mean 6.4 mm (SD 1.1) | Banded Minne: Mean 5.3 mm (SD 1.9) | P value = NS (as reported in the study ‐ number of participants included in analysis not reported) | |
| Stability: relapse of molar expansion (24 weeks after completion of expansion phase) | Bonded Minne: Mean 2.3 mm (SD 0.8) | Banded Minne: Mean 2.5 mm (SD 0.6) | P value = NS (as reported in the study ‐ number of participants included in analysis not reported) | |
| Stability: relapse of canine expansion (24 weeks after completion of expansion phase) | Bonded Minne: Mean 1.6 mm (SD 0.5) | Banded Minne: Mean 1.2 mm (SD 0.3) | P value = NS (as reported in the study ‐ number of participants included in analysis not reported) | |
| Molar expansion | Semi‐rapid maxillary expansion: Mean 5.71 mm (SD 1.66) | Rapid maxillary expansion: Mean 5.11 mm (SD 1.81) | MD 0.60 (95% CI ‐0.55 to 1.75) P value = 0.31 | |
| Canine expansion | Semi‐rapid maxillary expansion: Mean 5.13 mm (SD 1.47) | Rapid maxillary expansion: Mean 4.77 mm (SD 1.53) | MD 0.36 (95% CI ‐0.64 to 1.36) P value = 0.48 |
CI: confidence interval; MD: mean difference; min: minimum; max: maximum; NS: not significant; RR: risk ratio; SD: standard deviation.
* There is a discrepancy between the mean reported in Table 1 (5.3) and the text (8.3). The latter must be the actual mean as the text reports that there is no significant difference, whereas if the mean were 5.3, the P value is < 0.05 (based on assumption of no drop‐outs).
No other outcomes of the review were assessed in this comparison.
Tooth‐tissue borne Haas versus tooth borne Hyrax
Two studies, both at unclear risk of bias, analysing 27 participants, assessed molar expansion (Garib 2005; Oliveira 2004). The pooled mean difference (MD) was 0.7 mm (95% confidence interval (CI) ‐0.25 to 1.66) in favour of Haas appliances at three months after completion of the expansion phase, but the difference was not statistically significant (Analysis 1.1). As the sample size was so small, and there was considerable heterogeneity (I2 = 94%), this result should be interpreted with caution.
No other outcomes of the review were assessed in this comparison.
Hyrax tooth‐borne expander versus bone‐anchored expander
One study at unclear risk of bias, analysing no more than 41 participants (unclear attrition), assessed molar expansion at six and 12 months after completion of the expansion phase (Lagravere 2010). There were no statistically significant differences at either time point (Additional Table 1).
No other outcomes of the review were assessed in this comparison.
Four‐point banded (Hyrax) versus two‐point banded (Hyrax)
One study at high risk of bias, analysing no more than 30 participants (unclear attrition), assessed molar and canine expansion at three months after completion of the expansion phase (Lamparski 2003). There were no statistically significant differences for either outcome (Additional Table 1).
No other outcomes of the review were assessed in this comparison.
Slow expansion
Bonded Minne versus banded Minne appliances
One study at unclear risk of bias, analysing no more than 10 participants (unclear attrition), assessed molar and canine expansion seven to 15 weeks after the start of treatment, and stability (relapse of molar and canine expansion) 24 weeks after completion of the expansion phase (Mossaz‐Joelson 1989). There were no statistically significant differences for any outcome (Additional Table 1).
No other outcomes of the review were assessed in this comparison.
Different rates of expansion
Slow versus rapid expansion (two‐band palatal expanders)
One study at high risk of bias, analysing 26 participants, assessed molar expansion seven months after the start of treatment (Martina 2012). There was no statistically significant difference (Additional Table 1).
No other outcomes of the review were assessed in this comparison.
Semi‐rapid versus rapid expansion (splint type tooth‐ and tissue‐borne modified bonded appliances)
One study at unclear risk of bias, analysing 35 participants, assessed molar and canine expansion (Ramoglu 2010). There were no statistically significant differences for either outcome (Additional Table 1).
No other outcomes of the review were assessed in this comparison.
2. Fixed versus removable
Slow expansion
Quad‐helix versus expansion plate
We included two studies, both at low risk of bias, analysing 96 participants, in this comparison (Godoy 2011; Petrén 2008). The two studies included children in the early mixed dentition (aged eight to 10 years). For the outcome crossbite correction, the pooled risk ratio (RR) suggests that fixed quad‐helix appliances may be 20% more likely to correct crossbites than removable expansion plates (RR 1.20; 95% CI 1.04 to 1.37) (Analysis 2.1). The 95% CI indicates that the true effect estimate lies somewhere between a 4% and 37% better correction rate for quad‐helix appliances. However, the sample size was small and there was substantial heterogeneity (I2 = 68%), so this result should be interpreted with caution, and the results may not be the same in the permanent dentition.
For the outcome molar expansion, the pooled MD suggests that quad‐helix appliances can achieve 1.15 mm more expansion than expansion plates (MD 1.15 mm; 95% CI 0.40 to 1.90) (Analysis 2.2). The 95% CI indicates that the true effect estimate lies somewhere between 0.4 mm and 1.9 mm in favour of quad‐helix appliances. While there was no heterogeneity (I2 = 0%), the result should be interpreted with caution as the sample size was small and the follow‐up times differed between the studies.
For the outcome canine expansion, the pooled MD was 0.19 mm (95% CI ‐0.47 to 0.85) in favour of quad‐helix appliances, but the difference was not statistically significant (Analysis 2.3). Due to considerable heterogeneity (I2 = 91%), small sample size and different follow‐up times, the result should be interpreted with caution.
One study also assessed the stability of crossbite correction (relapse 12 months after correction) (Godoy 2011). There was no statistically significant difference (Additional Table 2).
| Study | Outcome | Group A | Group B | Results |
| Stability of crossbite correction (relapse 12 months after correction) | Quad‐helix: 3/33 | Removable expansion plate: 3/33 | RR 1 (95% CI 0.43 to 2.32) P value = 1 | |
| Crossbite correction | Quad‐helix: 15/15 | Composite onlays: 2/15 | RR 6.20 (95% CI 1.98 to 19.43) P value = 0.002 | |
| Molar expansion | Quad‐helix: Mean 4.6 mm (SD 1.19) | Composite onlays: Mean 0.5 mm (SD 0.46) | MD 4.10 (95% CI 3.45 to 4.75) P value < 0.00001 | |
| Canine expansion | Quad‐helix: Mean 2 mm (SD 1.18) | Composite onlays: Mean 0.63 mm (SD 0.7) | MD 1.37 (95% CI 0.68 to 2.06) P value = 0.0001 | |
| Crossbite correction | Removable expansion plate: 10/15 | Composite onlays: 2/15 | RR 5 (95% CI 1.31 to 19.07) P value = 0.02 | |
| Molar expansion | Removable expansion plate: Mean 3.5 mm (SD 1.54) | Composite onlays: Mean 0.5 mm (SD 0.46) | MD 3.00 (95% CI 2.19 to 3.81) P value < 0.00001 | |
| Canine expansion | Removable expansion plate: Mean 2.7 mm (SD 1.2) | Composite onlays: Mean 0.63 mm (SD 0.7) | MD 2.07 (95% CI 1.37 to 2.77) P value < 0.00001 |
CI: confidence interval; MD: mean difference; NS: not significant; RR: risk ratio; SD: standard deviation
No other outcomes of the review were assessed in this comparison.
One study also compared both appliances in this comparison against composite onlays (Petrén 2008). There were statistically significant differences for the outcomes crossbite correction, molar expansion and canine expansion in favour of the fixed and removable appliances (Additional Table 2).
3. Other comparisons
Early treatment with fixed bonded Hyrax appliance followed by U‐bow activator therapy versus no treatment
One study at high risk of bias, analysing 66 participants, assessed molar and canine expansion 12 months after the start of treatment (Lippold 2013). Statistically significant differences were reported for both outcomes in favour of treatment (Additional Table 3).
| Study | Outcome | Group A | Group B | Results |
| Molar expansion (12 months after start of treatment) | Fixed bonded Hyrax appliance followed by U‐bow activator: Mean 5.1 mm | No treatment: Mean 0.8 mm | P value < 0.001 (as reported in the study ‐ no SD for mean change from baseline reported) | |
| Canine expansion (12 months after start of treatment) | Fixed bonded Hyrax appliance followed by U‐bow activator: Mean 3.6 mm | No treatment: Mean 1 mm | P value < 0.001 (as reported in the study ‐ no SD for mean change from baseline reported) | |
| Molar expansion (12 weeks after start of treatment) | Quad‐helix + multi‐bracket: Mean 4.54 mm (SD 1.27) | Expansion arch + multi‐bracket: Mean 5.09 mm (SD 1.67) | MD ‐0.55 (95% CI ‐1.34 to 0.24) P value = 0.17 | |
| Canine expansion (12 weeks after start of treatment) | Quad‐helix + multi‐bracket: Mean 1.4 mm (SD 1.75) | Expansion arch + multi‐bracket: Mean 2.12 mm (SD 1.11) | MD ‐0.72 (95% CI ‐1.52 to 0.08) P value = 0.08 | |
| Molar and canine expansion | Removable with conventional screw | Removable with spring‐loaded screw | Results inadequately reported | |
| Crossbite correction | Grinding or grinding + expansion plate: 26/33 | No treatment: 6/28 | RR 3.68 (95% CI 1.77 to 7.64) P value = 0.0005 |
CI: confidence interval; MD: mean difference; NS: not significant; RR: risk ratio; SD: standard deviation.
No other outcomes of the review were assessed in this comparison.
Grinding ‐ occlusal grinding in the primary dentition (at age five years) with/without subsequent upper removable expansion appliance in the mixed dentition versus no treatment
One study at high risk of bias, analysing 61 participants, assessed crossbite correction after one, two, five and eight years (Thilander 1984). A statistically significant difference was reported in favour of treatment (Additional Table 3).
Slow expansion
Quad‐helix plus multi‐bracket versus expansion arch plus multi‐bracket
One study at high risk of bias assessed molar (analysing 55 participants) and canine (analysing 52 participants ‐ lower number due to unerupted canines) expansion 12 weeks after the start of treatment (McNally 2005). There were no statistically significant differences for either outcome (Additional Table 3).
Conventional mid‐line expansion screw versus spring‐loaded expansion screw
One study at high risk of bias assessed molar and canine expansion but we were unable to extract any data from the study report (Oshagh 2012).
Discussion
Summary of main results
The objective of this review was to evaluate the effects of different orthodontic treatments for correcting posterior crossbites. We included 15 randomised controlled trials (RCTs) that met the inclusion criteria for this review. We assessed the body of evidence for each comparison and outcome using GRADE, which takes into account the risk of bias of the included studies, the directness of the evidence, the inconsistency of the results, the precision of the estimates and the risk of publication bias (GRADE 2004). The body of evidence for all comparisons and outcomes in this review was very small.
Fixed appliance with mid‐palatal expansion
The body of evidence for all comparisons and outcomes in this group was rated as very low quality (summary of findings Table for the main comparison). In all cases, the evidence was insufficient to determine a difference between any one type of appliance and another for any outcome.
Fixed versus removable appliance
We found low‐quality evidence to suggest that crossbite correction is more successful when using a fixed quad‐helix appliance than when using a removable expansion plate for slow maxillary expansion (summary of findings Table 2). For the same comparison, moderate‐quality evidence suggested that molar expansion is greater for fixed quad‐helix appliances, and further low‐quality evidence was insufficient to determine a difference in canine expansion. It should be noted that the two studies included children in the early mixed dentition (aged eight to 10 years) and the results may not be the same for people in the permanent dentition. There was also very low quality evidence that was insufficient to determine a difference in stability of crossbite correction between fixed quad‐helix appliances and removable expansion plates. Further very low quality evidence suggested that fixed quad‐helix appliances and removable expansion plates are superior to composite onlays for crossbite correction, molar expansion and canine expansion.
Others interventions
We found very low quality evidence to suggest that both tooth grinding, with or without an expansion plate and fixed bonded Hyrax followed by U‐bow activator are superior to no treatment for the outcomes crossbite correction and molar/canine correction respectively (summary of findings Table 3). We also found very low quality evidence that was insufficient to determine a difference in molar or canine expansion between quad‐helix plus multi‐bracket and expansion arch plus multi‐bracket. Finally, there was no evidence regarding the comparison of removable appliances with either spring‐loaded or conventional screws.
Overall completeness and applicability of evidence
The studies identified in this review are insufficient to address the question of what is the best treatment for posterior crossbites. Although we were able to include 15 studies, there were many different comparisons of appliances or other treatments and, therefore, there was minimal pooling of data. This is unfortunate as one of the advantages of a systematic review is the ability to pool multiple studies in order to increase the power to detect a difference confidently, and thus to inform clinical practice better. Furthermore, there were very limited data available for the outcome stability of crossbite correction, and no studies assessed signs and symptoms of temporomandibular joint dysfunction/respiratory disease or quality of life. However, this was perhaps because all the studies included only children. This highlights another shortcoming in the overall completeness of the evidence, which is that there is no evidence on orthodontic treatments for adults with posterior crossbites. The lack of evidence regarding adults in this review is probably because the majority of studies on adults with a posterior crossbite compare orthodontic treatments with orthodontic‐surgical interventions, but we excluded surgical treatments from this review.
Quality of the evidence
The body of evidence identified does not allow for any robust conclusions to be made regarding the objective of this review. The sample sizes were consistently small (as low as eight participants), and this fact, combined with the lack of pooling of data in meta‐analyses, meant that the power to detect statistically and clinically significant differences, with confidence, was limited. Another problem was inconsistency as three of the four meta‐analyses displayed statistically significant heterogeneity. While there were two low risk of bias studies that we were able to pool, the results cannot be relied upon due to the problems already mentioned. The remaining studies were either at high risk of bias (seven studies) or the risk of bias was unclear (six studies). Most of the comparisons included in the review were assessed by very small single studies, which do not allow any conclusions to be drawn as to the effects of the interventions studied.
Potential biases in the review process
We made every attempt to limit bias in the review process by ensuring a comprehensive search for potentially eligible studies. The authors' independent assessments of study eligibility and subsequent data extraction and risk of bias assessment minimised the potential for additional bias beyond that detailed in the 'Risk of bias' tables in the Characteristics of included studies section. The incompleteness of some of the reports and our inability to obtain clarification of certain trial details or to resolve ambiguities in the reports may have contributed to some bias in their assessment, but where these conditions applied this was explicitly stated in the text of our review. Finally, we attempted to minimise bias further by changing our inclusion criteria to only include RCTs which, when performed to a high standard, should be less biased than other study designs.
Agreements and disagreements with other studies or reviews
Another systematic review of maxillary expansion arches for treating crossbites included studies published from 1999 to 2011 (Zuccati 2013). The authors of the review assessed the studies using the Consolidated Standards of Reporting Trials (CONSORT) statement. In similarity with our review, they argued that there was substantial evidence of bias, which reduced the quality of the evidence; the randomisation process was poorly described and loss to follow‐up was unclear in many of the included studies. Their review also called for future trials to be carefully planned and reported using universal guidelines.
Risk of bias summary: review authors' judgements about each risk of bias item for each included study.
Comparison 1 Fixed rapid (Haas) versus fixed rapid (Hyrax), Outcome 1 Molar expansion (3 months after completion of expansion phase).
Comparison 2 Fixed slow (quad‐helix) versus removable slow (expansion plate), Outcome 1 Crossbite correction.
Comparison 2 Fixed slow (quad‐helix) versus removable slow (expansion plate), Outcome 2 Molar expansion.
Comparison 2 Fixed slow (quad‐helix) versus removable slow (expansion plate), Outcome 3 Canine expansion.
| Fixed appliances compared with other fixed appliances for treating posterior crossbites | ||||||
| Patient or population: Children with posterior crossbites (adults would be included in the review but no studies with adults were found) Settings: Typically university orthodontic/dental clinics Intervention: Fixed appliance Comparison: The same fixed appliance attached differently or expanded at different speeds or a different fixed appliance | ||||||
| Outcomes | Illustrative comparative risks (95% CI) | Relative effect | No of participants | Quality of the evidence | Comments | |
| Assumed risk | Corresponding risk | |||||
| Group A | Group B | |||||
| Molar expansion (mm) (rapid expansion) banded Hyrax (tooth borne) versus bonded Hyrax (tooth/tissue borne) | N/A | N/A | N/A | 53 | ⊕⊝⊝⊝ | 2 studies (1 high risk of bias; 1 unclear), which were not possible to pool in a meta‐analysis due to no reporting of variance in 1 study. Imprecision due to low sample sizes. Different timings of follow‐up after completion of expansion. Both studies reported no difference in molar expansion |
| Molar expansion (mm) (3 months after completion of expansion phase) (rapid expansion) tooth‐tissue borne (Haas) versus tooth borne (Hyrax) | The mean expansion ranged across the Haas groups from | The mean expansion in the Hyrax groups was | N/A | 27 | ⊕⊝⊝⊝ | 2 studies at unclear risk of bias with serious inconsistency (I2 = 94%) and imprecision due to low sample size |
| N/A | N/A | N/A | N/A | N/A | N/A | The remaining comparisons were all single studies (Additional Table 1). The quality of the evidence (GRADE) for all comparisons and outcomes in Additional Table 1 is ⊕⊝⊝⊝ very low (all at unclear or high risk of bias with imprecision due to low sample sizes). None of these studies showed a statistically significant difference for any outcome |
| CI: confidence interval; N/A: not applicable. | ||||||
| GRADE Working Group grades of evidence | ||||||
| Fixed appliances compared with removable appliances for treating posterior crossbites | ||||||
| Patient or population: Children with posterior crossbites (adults would be included in the review but no studies with adults were found) Settings: Public Dental Health Service and university orthodontic/dental clinics Intervention: Fixed appliance Comparison: Removable appliance | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect | No of participants | Quality of the evidence | Comments | |
| Assumed risk | Corresponding risk | |||||
| Removable ‐ slow expansion (expansion plate) | Fixed ‐ slow expansion (quad‐helix) | |||||
| Crossbite correction (Follow‐up after retention period, therefore, it was variable) | 833 per 1000 | 1000 per 1000 | RR 1.2 (1.04 to 1.37) | 96 | ⊕⊕⊝⊝ | 2 studies at low risk of bias, but with serious inconsistency (I2 = 68%) and imprecision due to low sample size |
| Molar expansion (mm) (Follow‐up after retention period, therefore, it was variable) | The mean expansion ranged across the removable appliance groups from 3.09 to 3.5 mm | The mean expansion in the fixed appliance group was | N/A | 96 | ⊕⊕⊕⊝ | 2 studies at low risk of bias, but with imprecision due to low sample size |
| Canine expansion (mm) (Follow‐up after retention period, therefore it was variable) | The mean expansion ranged across the removable appliance groups from 1.43 to 2.7 mm | The mean expansion in the fixed appliance group was | N/A | 96 | ⊕⊕⊝⊝ | 2 studies at low risk of bias, but with serious inconsistency (I2 = 91%) and imprecision due to low sample size |
| N/A | N/A | N/A | N/A | N/A | N/A | 1 of the 2 studies in this comparison also measured stability of crossbite correction (relapse 12 months after correction). No statistically significant difference was found (Additional Table 2) The other study also compared the fixed and removable appliances to composite onlays for crossbite correction, molar expansion and canine expansion. All results were statistically significant in favour of fixed and removable appliances (Additional Table 2) The quality of the evidence (GRADE) for all comparisons and outcomes in Additional Table 2 is ⊕⊝⊝⊝ very low |
| *The basis for the assumed risk is the removable group event rate. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). | ||||||
| GRADE Working Group grades of evidence | ||||||
| Other comparisons for treating posterior crossbites | ||||||
| Patient or population: Children with posterior crossbites (adults would be included in the review but no studies with adults were found) Settings: Public Dental Health Service and university/hospital orthodontic/dental clinics | ||||||
| Outcomes | Illustrative comparative risks (95% CI) | Relative effect | No of participants | Quality of the evidence | Comments | |
| Assumed risk | Corresponding risk | |||||
| Group A | Group B | |||||
| N/A | N/A | N/A | N/A | N/A | N/A | The comparisons were all single studies (Additional Table 3). The quality of the evidence (GRADE) for all comparisons and outcomes in Additional Table 3 is ⊕⊝⊝⊝ very low (all at high risk of bias with imprecision due to low sample sizes)
|
| GRADE Working Group grades of evidence CI: confidence interval; N/A: not applicable. | ||||||
| Study | Outcome | Group A | Group B | Results |
| Molar expansion (3 months after completion of expansion phase) | Hyrax banded: Mean 6 mm (min 4.3 mm ‐ max 7.2 mm) | Hyrax bonded: Mean 5.9 mm (min 3.2 mm ‐ max 7.7 mm) | P value = NS (as reported in the study ‐ no SD reported) | |
| Molar expansion (1 week after completion of expansion phase) | Hyrax banded: Mean 7.67 mm (SD 1.99) | Hyrax bonded: Mean 7.31 mm (SD 1.45) | MD 0.36 (95% CI ‐0.72 to 1.44) P value = 0.51 | |
| Molar expansion (6 months after completion of expansion phase) | Hyrax tooth‐borne expander: Mean 5.83 mm (SD 1.54) | Bone‐anchored expander: Mean 5.75 mm (SD 1.98) | MD 0.08 (95% CI ‐1.00 to 1.16) P value = 0.88 | |
| Molar expansion (12 months after completion of expansion phase) | Hyrax tooth‐borne expander: Mean 4.24 mm (SD 1.69) | Bone‐anchored expander: Mean 4.03 mm (SD 1.49) | MD 0.21 (95% CI ‐0.77 to 1.19) P value = 0.67 | |
| Molar expansion (3 months after completion of expansion phase) | 4‐point expansion appliance (Hyrax): Not reported by group | 2‐point expansion appliance: Not reported by group | P value = "No significant differences were found" | |
| Canine expansion (3 months after completion of expansion phase) | 4‐point expansion appliance (Hyrax): Mean 3.034 mm | 2‐point expansion appliance: Mean 1.7 mm | P value = 0.331 (as reported in the study ‐ no SD reported) | |
| Molar expansion (7 months after start of treatment) | Slow maxillary expansion: Mean 6.3 mm (SD 2.1) | Rapid maxillary expansion: Mean 5.7 mm (SD 1.6) | MD 0.60 (95% CI ‐0.85 to 2.05) P value = 0.42 | |
| Molar expansion (7‐15 weeks after start of treatment) | Bonded Minne: Mean 7.9 mm (SD 1.5) | Banded Minne: Mean 8.3* mm (SD 1.1) | P value = NS (as reported in the study ‐ number of participants included in analysis not reported) | |
| Canine expansion (7‐15 weeks after start of treatment) | Bonded Minne: Mean 6.4 mm (SD 1.1) | Banded Minne: Mean 5.3 mm (SD 1.9) | P value = NS (as reported in the study ‐ number of participants included in analysis not reported) | |
| Stability: relapse of molar expansion (24 weeks after completion of expansion phase) | Bonded Minne: Mean 2.3 mm (SD 0.8) | Banded Minne: Mean 2.5 mm (SD 0.6) | P value = NS (as reported in the study ‐ number of participants included in analysis not reported) | |
| Stability: relapse of canine expansion (24 weeks after completion of expansion phase) | Bonded Minne: Mean 1.6 mm (SD 0.5) | Banded Minne: Mean 1.2 mm (SD 0.3) | P value = NS (as reported in the study ‐ number of participants included in analysis not reported) | |
| Molar expansion | Semi‐rapid maxillary expansion: Mean 5.71 mm (SD 1.66) | Rapid maxillary expansion: Mean 5.11 mm (SD 1.81) | MD 0.60 (95% CI ‐0.55 to 1.75) P value = 0.31 | |
| Canine expansion | Semi‐rapid maxillary expansion: Mean 5.13 mm (SD 1.47) | Rapid maxillary expansion: Mean 4.77 mm (SD 1.53) | MD 0.36 (95% CI ‐0.64 to 1.36) P value = 0.48 | |
| CI: confidence interval; MD: mean difference; min: minimum; max: maximum; NS: not significant; RR: risk ratio; SD: standard deviation. * There is a discrepancy between the mean reported in Table 1 (5.3) and the text (8.3). The latter must be the actual mean as the text reports that there is no significant difference, whereas if the mean were 5.3, the P value is < 0.05 (based on assumption of no drop‐outs). | ||||
| Study | Outcome | Group A | Group B | Results |
| Stability of crossbite correction (relapse 12 months after correction) | Quad‐helix: 3/33 | Removable expansion plate: 3/33 | RR 1 (95% CI 0.43 to 2.32) P value = 1 | |
| Crossbite correction | Quad‐helix: 15/15 | Composite onlays: 2/15 | RR 6.20 (95% CI 1.98 to 19.43) P value = 0.002 | |
| Molar expansion | Quad‐helix: Mean 4.6 mm (SD 1.19) | Composite onlays: Mean 0.5 mm (SD 0.46) | MD 4.10 (95% CI 3.45 to 4.75) P value < 0.00001 | |
| Canine expansion | Quad‐helix: Mean 2 mm (SD 1.18) | Composite onlays: Mean 0.63 mm (SD 0.7) | MD 1.37 (95% CI 0.68 to 2.06) P value = 0.0001 | |
| Crossbite correction | Removable expansion plate: 10/15 | Composite onlays: 2/15 | RR 5 (95% CI 1.31 to 19.07) P value = 0.02 | |
| Molar expansion | Removable expansion plate: Mean 3.5 mm (SD 1.54) | Composite onlays: Mean 0.5 mm (SD 0.46) | MD 3.00 (95% CI 2.19 to 3.81) P value < 0.00001 | |
| Canine expansion | Removable expansion plate: Mean 2.7 mm (SD 1.2) | Composite onlays: Mean 0.63 mm (SD 0.7) | MD 2.07 (95% CI 1.37 to 2.77) P value < 0.00001 | |
| CI: confidence interval; MD: mean difference; NS: not significant; RR: risk ratio; SD: standard deviation | ||||
| Study | Outcome | Group A | Group B | Results |
| Molar expansion (12 months after start of treatment) | Fixed bonded Hyrax appliance followed by U‐bow activator: Mean 5.1 mm | No treatment: Mean 0.8 mm | P value < 0.001 (as reported in the study ‐ no SD for mean change from baseline reported) | |
| Canine expansion (12 months after start of treatment) | Fixed bonded Hyrax appliance followed by U‐bow activator: Mean 3.6 mm | No treatment: Mean 1 mm | P value < 0.001 (as reported in the study ‐ no SD for mean change from baseline reported) | |
| Molar expansion (12 weeks after start of treatment) | Quad‐helix + multi‐bracket: Mean 4.54 mm (SD 1.27) | Expansion arch + multi‐bracket: Mean 5.09 mm (SD 1.67) | MD ‐0.55 (95% CI ‐1.34 to 0.24) P value = 0.17 | |
| Canine expansion (12 weeks after start of treatment) | Quad‐helix + multi‐bracket: Mean 1.4 mm (SD 1.75) | Expansion arch + multi‐bracket: Mean 2.12 mm (SD 1.11) | MD ‐0.72 (95% CI ‐1.52 to 0.08) P value = 0.08 | |
| Molar and canine expansion | Removable with conventional screw | Removable with spring‐loaded screw | Results inadequately reported | |
| Crossbite correction | Grinding or grinding + expansion plate: 26/33 | No treatment: 6/28 | RR 3.68 (95% CI 1.77 to 7.64) P value = 0.0005 | |
| CI: confidence interval; MD: mean difference; NS: not significant; RR: risk ratio; SD: standard deviation. | ||||
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
| 1 Molar expansion (3 months after completion of expansion phase) Show forest plot | 2 | 27 | Mean Difference (IV, Fixed, 95% CI) | 0.70 [‐0.25, 1.66] |
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
| 1 Crossbite correction Show forest plot | 2 | 96 | Risk Ratio (M‐H, Fixed, 95% CI) | 1.20 [1.04, 1.37] |
| 2 Molar expansion Show forest plot | 2 | 96 | Mean Difference (IV, Fixed, 95% CI) | 1.15 [0.40, 1.90] |
| 3 Canine expansion Show forest plot | 2 | 96 | Mean Difference (IV, Fixed, 95% CI) | 0.19 [‐0.47, 0.85] |
