Summary of findings
Description of the condition
Orthodontics is the branch of dentistry concerned with the growth of the jaws and face, the development of the teeth, and the way the teeth and jaws bite together. It also involves treatment of the teeth and jaws when they are irregular or bite in an abnormal way, or both. There are many reasons why the teeth may not bite together correctly. These include the position of the teeth, jaws, lips, tongue and/or cheeks, or may be due to a habit or the way people breathe. All of these factors can be influenced by genetics or by the environment. The need for treatment can be decided by looking at the effect of any particular tooth position on the life expectancy of the teeth or the effect that the appearance of the teeth has on how people feel about themselves, or both (Shaw 1991).
Prominent lower front teeth (termed reverse bite; under bite; Class III malocclusion) may be due to a combination of the jaw or tooth position, or both, resulting from genetic factors or environmental influence or both. The upper jaw (maxilla) can be too far back or the lower jaw (mandible) too far forward, or both. Prominent lower front teeth can also occur if the upper front teeth (incisors) are tipped back or the lower front teeth are tipped forwards or both. Prominent lower front teeth can give a person an aggressive appearance, which may be the source of teasing (Shaw 1980). Patients with prominent lower front teeth often report that they have problems eating, and occasionally problems with speech. Prominent lower front teeth can give rise to problems with the jaw joints in later life (Mohlin 1980). Prominent lower front teeth are most common in oriental (15%) and black races (10%) and are relatively uncommon in Caucasian (4%) populations (el-Mangoury 1990; Proffit 1993; Silva 2001). Prominent lower front teeth are usually due to the way the jaws meet together with either the upper jaw being too small, the lower jaw being too large, or a combination of both.
Description of the intervention
Several dental brace (orthodontic) treatments have been suggested to correct prominent lower front teeth. Some treatments aim to tip the upper front teeth forwards and the lower front teeth backwards whilst others aim to modify the growth of the upper or lower jaw or both to reduce or correct the prominence of the lower front teeth. Treatment can involve the use of one or more types of orthodontic brace. Some braces apply a force directly to the teeth and can either be removed from the mouth or fixed to the teeth with special glue during treatment. Other types of brace are attached, via the teeth, to devices (for example chin cup, reverse headgear, facemask) that allow a force to be applied to the teeth and jaws from the chin or forehead, or both. A further, more recently described technique has been the use of bone-anchors surgically placed to the jaw bones prior to activation with elastics (De Clerck 2010). Treatment is usually carried out either early, when the patients have a mixture of their baby and adult teeth present (around seven to 11 years of age), or later when all the adult teeth have come into the mouth (around 12 to 16 years of age). However, in some cases treatment is carried out early, before six years of age, when the patients only have their baby teeth present or later when the patient is an adult. In severe cases, and with some adult patients, orthodontic treatment may need to be combined with jaw surgery to correct the position of one or both jaws.
How the intervention might work
There are several ways in which the intervention may correct the prominence of the lower front teeth. It may move the top jaw forwards, the top teeth forwards, the bottom jaw backwards, the bottom teeth backwards, or often a combination of these factors. Some interventions may also have an influence on the vertical position of the jaws, which in turn influences the antero-posterior position of the jaws due to the rotation of the jaws during growth.
Why it is important to do this review
There is currently a multitude of different appliances available to try to correct the prominence of lower front teeth in children. There is, however, little consensus as to which of these approaches may be best. There is also little known about the long-term effects of these approaches. If a successful approach that has effects that last until the end of growth could be found this may prevent the need for surgical treatment when the patient is older.
To assess the effects of orthodontic treatment for prominent lower front teeth in children and adolescents.
Criteria for considering studies for this review
Types of studies
All randomised controlled trials of orthodontic treatments to correct prominent lower front teeth.
Types of participants
Studies were eligible for inclusion in the review if they had recruited children or adolescents or both (age 16 years or less) receiving orthodontic treatment to correct prominent lower front teeth. Studies including patients with a cleft lip or palate or both, or other craniofacial deformity or syndrome, were excluded as were studies that had recruited less than 80% children or adolescents as participants, or patients who had previously received surgical treatment for their prominent lower front teeth.
Types of interventions
Active interventions: orthodontic braces (removable, fixed, functional), chin cups, facemasks, reverse headgear, bone-anchored appliances, or any other intra or extra-oral appliance aimed at correcting prominent lower front teeth.
Control: may be no treatment, delayed treatment, or another active intervention.
Types of outcome measures
Prominence of the lower front teeth (measured in mm or by any index of malocclusion).
Relationship between upper and lower jaw:
- psychosocial measures;
- patient satisfaction;
- jaw joint problems.
Adverse effects: health of the gums (gingivae); damage to the teeth (e.g. tooth decay).
Outcomes were recorded at all the ages reported. The results were reported according to the most common endpoints. Adverse effects were recorded and the results reported in descriptive terms.
Search methods for identification of studies
For the identification of studies to be 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 randomised trials (RCTs) in MEDLINE: sensitivity maximising version (2008 revision) as referenced in Chapter 184.108.40.206 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 3. The search of EMBASE was linked to the Cochrane Oral Health Group filters for identifying RCTs (Appendix 4).
The following databases were searched.
- The Cochrane Oral Health Group's Trials Register (to 7 January 2013) (Appendix 1).
- The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 12) (Appendix 2).
- MEDLINE via OVID (1946 to 7 January 2013) (Appendix 3).
- EMBASE via OVID(1980 to 7 January 2013) (Appendix 4).
Only handsearching done as part of the Cochrane Worldwide Handsearching Programme and uploaded to CENTRAL was included (see the Cochrane Masterlist for details of journal issues searched to date).
The bibliographies of the clinical studies that were identified were checked for references to studies published outside the handsearched journals.
Personal references were checked.
Databases were searched to include all languages and non-English language papers were translated.
Data collection and analysis
Selection of studies
The titles and abstracts of the search results were examined to remove obviously irrelevant reports. This was done by two of the review authors (either Simon Watkinson (SW), Jayne Harrison (JH) or Sue Furness (SF)) independently and in duplicate. Disagreements were resolved by discussion between these review authors. If arbitration was required, it was provided by Annabel Teague (AT).
Full text reports of potentially eligible studies were examined for compliance with the eligibility criteria. This was performed by two review authors (SW, JH or SF) independently and in duplicate. We corresponded with investigators, where appropriate, to clarify study eligibility. Disagreements were resolved by discussion between these review authors. If arbitration was required, it was provided by AT. If additional information was required, the corresponding author of the study was contacted and the study categorised as awaiting assessment. The study eligibility process was performed with the aid of a piloted study eligibility form.
A list of excluded studies was recorded, giving the primary reason for exclusion, following the screening of the titles and abstracts stage.
Data extraction and management
Data extraction was performed independently and in duplicate by two review authors (SW, JH or SF). A piloted data extraction form was used independently to record the year of publication, interventions assessed, outcomes, adverse effects, sample size and age of the participants.
Outcome data were grouped into those measured immediately after treatment and those measured at any other times reported.
Assessment of risk of bias in included studies
The Cochrane risk of bias tool was used to assess the methodological quality of the studies. This was undertaken independently and in duplicate by two review authors (SW, JH or SF) as a part of the data extraction process. Six specific domains were investigated: sequence generation; allocation concealment; blinding of participants, personnel and outcome assessors; incomplete outcome data; selective outcome reporting; and 'other sources of bias'.
Each domain was given a judgement that could be high, low, or unclear. 'High' indicated a high risk of bias, 'Low' a low risk of bias, and 'Unclear' indicated an unclear or unknown level of bias. The risk of bias tool was applied as described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). Sequence generation was assessed for the study as a whole. Blinding, incomplete outcome data and selective outcome reporting were assessed at the level of the study and for each outcome as appropriate.
Measures of treatment effect
The Cochrane Collaboration statistical guidelines were followed and the data analysed using Review Manager (RevMan) 5 software (RevMan 2012) and reported according to Cochrane Collaboration criteria.
For dichotomous data, the estimates of the effect of an intervention would have been expressed as risk ratios together with 95% confidence intervals.
For continuous outcomes, mean differences and 95% confidence intervals were used to summarise the data for each group where the mean differences and standard deviations were calculable from the data presented.
Dealing with missing data
If there were any missing data, an attempt was made to contact the original study investigators. A study was not excluded from the review because of missing summary data, however the potential implications of their absence from any meta-analysis were discussed.
Assessment of heterogeneity
Clinical heterogeneity was assessed by examining the type of participants, interventions and outcomes in each study. Meta-analysis was only used when studies of similar comparisons reported comparable outcome measures. A random-effects model was planned for use for all analyses with more than three studies, otherwise a fixed-effect model was used. The I
Assessment of reporting biases
Only a proportion of research projects conducted are ultimately published in an indexed journal and so become easily identifiable for inclusion in systematic reviews. Reporting biases arise when the reporting of research findings is influenced by the nature and direction of the findings of the research (Easterbrook 1991). We investigated and attempted to minimise potential reporting biases including publication bias, multiple (duplicate) publication bias and language bias in this review.
If there were more than 10 studies for one outcome we planned to construct a funnel plot. If there was asymmetry in the funnel plot, indicating possible publication bias, we planned to undertake statistical analysis using the methods introduced by Egger 1997 (continuous outcome) and Rücker 2008 (dichotomous outcome). Insufficient studies were identified to investigate reporting biases.
A random-effects meta-analysis, using the inverse variance method, was planned for use with all primary and secondary outcomes, for all analyses with more than three studies. Studies of each intervention were analysed and presented separately.
A general framework for data synthesis was used to report the adverse effects. The following questions were considered when analysing these effects.
- What was the size of the effect?
- Was the effect consistent across studies?
- What was the strength of evidence for the effect?
Subgroup analysis and investigation of heterogeneity
We planned to investigate clinical heterogeneity by examining: the nature of the interventions; ages, background and number of participants; and reported outcomes. No subgroup analyses were planned.
Providing there were sufficient studies for each intervention and outcome, we planned to undertake sensitivity analysis based on risk of bias (including low risk of bias studies only).
Presentation of main results
A summary of findings table was developed for the primary outcomes of this review using GRADEPro software. The quality of the body of evidence was assessed with reference to the overall risk of bias of the included studies; the directness of the evidence; the consistency of the results; the precision of the estimates; the risk of publication bias; and the magnitude of the effect. The quality of the body of evidence for each of the primary outcomes was categorised as high, moderate, low or very low, and summary of findings tables have been produced for the main outcomes of this review.
Description of studies
Results of the search
The database search identified 440 articles. Of these 19 were duplicates. Of the remaining 421, 391 were discarded during the screening of the titles and abstracts. Of the remaining 30 articles, for which the full text was examined, 22 were excluded leaving eight included articles two of which were reporting the outcomes of the same study, at different time points, leaving seven randomised controlled trials (RCTs) to be included in this review (Figure 1).
|Figure 1. Study flow diagram.|
Seven studies were included in this review. All studies were parallel group randomised controlled trials. Three studies were conducted in Turkey (Arun 1994; Atalay 2010; Keles 2002), one in Egypt (Abdelnaby 2010), one in the United Kingdom (Mandall 2010), one in the United States of America (Vaughn 2005) and one in China (Xu 2001). Six studies reported outcome data solely immediately post-treatment. One study had outcomes reported at both 15 months and three years after the start of treatment (Mandall 2010) (Characteristics of included studies).
Characteristics of the study setting and investigators
All of the included studies were conducted in college or university orthodontic departments. Six of the studies were carried out in a single institution (Abdelnaby 2010; Arun 1994; Atalay 2010; Keles 2002; Vaughn 2005; Xu 2001) and one in eight centres in the same country (Mandall 2010).
Orthodontists provided the care for the children in all the studies. Only one paper (Vaughn 2005) stated they had two operators, the remainder did not disclose the number of operators.
Only one study (Mandall 2010) disclosed external funding.
Characteristics of the participants
All studies were conducted on children aged between five and 11 years. They were from different ethnic backgrounds, which were dependant on the study setting. There were between 20 (Keles 2002) and 73 (Mandall 2010) children included in the seven studies, with a median of 46. Approximately equal numbers of boys and girls were included in each study.
Characteristics of the interventions
Four different types of intervention were compared with an untreated control group in the seven included studies. Control groups had either no treatment or delayed treatment. As such, during the experimental period patients in the control groups received no active treatment and were solely monitored for natural growth and development. The comparisons were the following.
- Facemask with expansion versus facemask only (Vaughn 2005).
- Nanda facemask versus conventional facemask (Keles 2002).
- A 600 g chin cup versus 300 g chin cup versus untreated control (Abdelnaby 2010).
- Tandem traction bow appliance versus untreated control (Atalay 2010).
- Mandibular headgear versus chin cup versus untreated control (Arun 1994).
Characteristics of the outcomes
Five outcomes were presented in the results for the seven included studies.
- Piers Harris children's self concept scale (Mandall 2010).
- Oral Aesthetic Subjective Impact Score (OASIS) (Mandall 2010).
Of the 22 excluded studies:
- 13 were excluded as they were not RCTs;
- six used retrospective control groups;
- one was entirely retrospective;
- one did not report an outcome of interest to this review;
- one reported outcomes for patients over the age of 16 years.
Risk of bias in included studies
Sequence generation was adequate for four of the studies (Arun 1994; Atalay 2010; Mandall 2010; Vaughn 2005) and unclear for the remaining studies. Whilst the Arun 1994 and Atalay 2010 papers were unclear in the text, contact with the authors revealed the use of a random number generator for patient assignment on registration to the study. Mandall 2010 used randomisation blocks of 10 with stratification according to gender and a computer generated randomisation sequence. Vaughn 2005 also used a block randomisation table to assign participants to one of the three groups. The remaining papers did not mention how a sequence was generated and no response has been received from the authors for further clarification.
Allocation concealment was adequate in only one of the included studies, Mandall 2010, who used a sequence that was concealed centrally and each clinician telephoned the research assistant for allocation once the patient was registered. It was unclear for four of the studies (Abdelnaby 2010; Keles 2002; Vaughn 2005; Xu 2001) in which there was no mention of allocation concealment in the articles and there has been no response from the authors providing clarification. There was a high risk of bias from the remaining two articles (Arun 1994; Atalay 2010), with whom contact was made and they disclosed that no allocation concealment was used.
The blinding of participants would not have been possible in six of the seven studies due to the nature of the treatments in comparison with other treatments and the untreated controls. However, it may have been possible to blind patients in the Abdelnaby 2010 study, which compared the strength of force of the chin cups. No mention of an attempt to do this was mentioned in the paper and the author has not responded to clarify the situation.
The blinding of the personnel taking part in the studies would not have been possible due to the nature of the treatments being used.
The blinding of the outcome assessment would have been possible in all cases as cephalometric measures were used as outcomes in all studies. There was a low risk of bias in the Mandall 2010 study in which the researchers measuring the radiographs and study models, as well as the statistician, were all blinded. There was also low risk of bias in the Vaughn 2005 study as the principal investigator carrying out the analysis was blinded to the patient assignment. The blinding of outcome assessment was unclear in the Abdelnaby 2010; Keles 2002 and Xu 2001 studies in which no mention of blinding was made and no response from the authors has been received to clarify this. The authors of Arun 1994 and Atalay 2010 confirmed that there were no attempts at blinding at any stage in these studies and therefore the risk of bias was high.
Incomplete outcome data
There was a low risk of attrition bias for the Arun 1994; Atalay 2010; Mandall 2010 and Xu 2001 studies as the participants included in the analysis were exactly those randomised in the study. The number of drop-outs in the remaining three studies (Abdelnaby 2010; Keles 2002; Vaughn 2005) was unclear and the authors have not responded to clarify the question, so the risk of attrition bias in these studies was assessed as unclear.
There was a low risk of reporting bias for all studies. All studies reported on the outcomes that they set out to report and there were no obvious anomalies.
Other potential sources of bias
The Abdelnaby 2010 study stated that the groups were randomly allocated yet there were 20 patients in groups 1 and 2 and only 10 in group 3. Clarification on the exact method of randomisation has not been possible as the author has not responded to our contact, however this leads to an assumption of high risk of bias.
The Mandall 2010 paper disclosed that some patients included in this study had a centric relation to centric occlusion displacement. This may have influenced the perception of the skeletal discrepancy from the lateral cephalogram. The actual effects of this on the results were unclear. Therefore, this has resulted in a decision to classify this study as at unclear risk of bias.
Overall risk of bias
The study by Mandall 2010 showed overall low risk of bias. Three studies (Abdelnaby 2010; Arun 1994; Atalay 2010) were assessed at high risk of bias due to the absence of allocation concealment, blinding of outcome assessment (Arun 1994; Atalay 2010) and inadequate randomisation (Abdelnaby 2010). The remaining three studies (Keles 2002; Vaughn 2005; Xu 2001) were assessed as having unclear risk of bias (Figure 2; Figure 3).
|Figure 2. Risk of bias graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.|
|Figure 3. Risk of bias summary: review authors' judgements about each risk of bias item for each included study.|
Effects of interventions
See: Summary of findings for the main comparison Facemask compared to no treatment for prominent lower front teeth in children; Summary of findings 2 Chin cup compared to no treatment for prominent lower front teeth in children; Summary of findings 3 Tandem traction bow appliance compared to no treatment for prominent lower front teeth in children
There were eight comparisons in the seven included studies. The results for each comparison are summarised below. Any results for a comparison including a single study are given in Additional Table 1, with forest plots being shown for the only comparison with more than one study.
Facemask versus untreated control
Three studies (n = 179) investigated the use of a facemask versus an untreated control (Mandall 2010; Vaughn 2005; Xu 2001). We have combined the results from the study using the facemask with and with out rapid maxillary expansion as these groups showed no statistical difference (see later) (Vaughn 2005). The only outcome considered by all three studies was ANB. The Mandall 2010 study also assessed overjet and self esteem measures whilst Vaughn 2005 also assessed Wits appraisal (another measure of the relative positions of the maxilla and mandible). The Mandall 2010 study reported outcomes at the end of treatment and at three years follow-up.
One study reported overjet (Mandall 2010) and found a statistically significant difference of 4.10 mm (95% confidence interval (CI) 3.04 to 5.16; P value < 0.0001) in favour of the facemask post-treatment. The study also found a statistically significant difference of 2.50 mm (95% CI 1.21 to 3.79; P value = 0.0001) at three years follow-up.
Three studies included the outcome ANB (Mandall 2010; Vaughn 2005; Xu 2001) and it was possible to undertake a meta-analysis at the post-treatment stage. The pooled estimate was 3.93 ° (95% CI 3.46 to 4.39; P value < 0.0001) in favour of the facemask. There was substantial heterogeneity (P value = 0.004; I
One study assessed ANB at three years follow-up (Mandall 2010) and found that a statistically significant benefit persisted in favour of the facemask (mean difference (MD) 1.4 °, 95% CI 0.43 to 2.37; P value = 0.004).
One study looked at Wits appraisal (Vaughn 2005) and showed a benefit in favour of the facemask of -3.84 mm (95% CI -5.31 to -2.37; P value < 0.0001).
There was no difference between the facemask and untreated control groups in the Mandall 2010 study in the outcome of self esteem measured on the Piers-Harris self esteem index at either the post-treatment or three years follow-up time points (Additional Table 1).
The OASIS assessment of self esteem, however, did demonstrate a statistically significant benefit for the facemask at the post-treatment stage of -4.00 (95% CI -7.40 to -0.60; P value = 0.02). However, there was no significant difference at three years follow-up (MD -3.40, 95% CI -7.99 to 1.19; P value = 0.15).
One study (Mandall 2010) reported on temporomandibular joint (TMJ) signs and symptoms. These were assessed by looking at pain (lateral and intra-auricular), clicking, crepitus, locking, muscle tenderness (temporalis, masseter, and lateral pterygoid), and restriction of jaw movement (maximum opening and lateral movement). In addition, the presence of forward mandibular displacement on closure was recorded. It was noted that due to the low prevalence of TMJ signs and symptoms at all time points no statistical analysis was carried out.
Facemask with expansion versus facemask only
Only one study (n = 46) compared the facemask with and without expansion (Vaughn 2005). There was no evidence of a difference between treatment using a facemask with or without the use of rapid maxillary expansion for the outcomes of ANB (MD -0.13 °, 95% CI -1.40 to 1.14; P value = 0.84) and Wits appraisal (MD -0.16 mm, 95% CI -1.63 to 1.31; P value = 0.83) ( Analysis 2.1; Analysis 2.2; Additional Table 1).
Nanda facemask versus conventional facemask
Only one study (n = 20) compared the Nanda facemask versus a conventional facemask (Keles 2002). There was weak evidence of a difference in ANB between the groups using each design of facemask in favour of the Nanda facemask (MD 1.29 °, 95% CI 0.16 to 2.42; P value = 0.02) ( Analysis 3.1; Additional Table 1).
Chin cup versus control
Two studies (n = 90) compared the chin cup with an untreated control group in three-arm studies (Abdelnaby 2010; Arun 1994). Both studies showed that the chin cup improved ANB and Wits appraisal when compared to the untreated control ( Analysis 4.1; Analysis 4.2; Additional Table 1). However, the results were not meta-analysed as we were unable to use the data from one of the studies (Arun 1994).
Chin cup 600 g versus 300 g
Outcome data on use of 600 g versus 300 g were reported in one study (Abdelnaby 2010). There was no difference in ANB (MD 0.10 °, 95% CI -0.31 to 0.51; P value = 0.63) or Wits appraisal (MD -0.30 mm, 95% CI -1.12 to 0.52; P value = 0.47) ( Analysis 5.1; Analysis 5.2; Additional Table 1).
Mandibular headgear versus chin cup
One study (n = 60) provided outcome data for ANB. However, no standard deviations were given and P values from the Mann-Whitney test were presented (Arun 1994) so we were unable to use the data ( Analysis 7.1). There was no statistically significant difference between the two active interventions (P value > 0.05).
Mandibular headgear versus untreated control
One study (n = 60) comparing mandibular headgear with control provided data for ANB (Arun 1994). We were unable to use the data since standard deviations were not reported; however, P values for the Mann-Whitney test showed that mandibular headgear provided a statistically significant benefit for ANB compared to the control (P value < 0.001).
Tandem traction bow appliance versus untreated control
One study (n = 30) compared the Tandem traction bow appliance versus control (Atalay 2010). Two outcomes, overjet and ANB, were reported and both demonstrated a statistically significant benefit in favour of the Tandem traction bow appliance: overjet 3.30 mm (95% CI 2.46 to 4.14; P value < 0.0001); ANB 1.70 ° (95% CI 1.09 to 2.31; P value < 0.0001) ( Analysis 6.1).
Summary of main results
We found some evidence that facemask therapy was more effective at improving overjet, ANB and Wits appraisal immediately post-treatment when compared with an untreated control. The improvements in overjet and Wits appraisal were still statistically significant at three years follow-up, although reduced in comparison to the changes immediately post-treatment. These changes remained of clinical significance. Whilst immediately following treatment there was a statistically significant improvement in the OASIS score, there was no evidence that facemask treatment produced clinically important changes in patients' self esteem measures.
There was insufficient evidence to determine whether there was a difference between the outcomes reported in a comparison between facemask with and without the use of rapid maxillary expansion from the single small study which evaluated this comparison. Therefore, its use solely as an adjunct to improve the efficacy of facemask therapy can not be recommended.
One study (Keles 2002) compared the use of a Nanda facemask (force applied at parallel to the Frankfort plane at a level 20 mm above the occlusal plane) with a conventional facemask (force applied at 30 ° at the level of the occlusal plane). This very small study showed weak evidence of a difference in ANB between the two appliances in favour of the Nanda facemask, however, due to the size of the study and its risk of bias, no recommendation can be made to support one design over the other.
The ultimate aim of facemask treatment is to correct the jaw discrepancy at an early stage so reducing the need for any orthognathic surgical intervention at a later stage. It must be noted that only one published study has reported data beyond the end of orthodontic treatment (Mandall 2010) and this only at three years follow-up, so no evidence was found for a long-term benefit for facemask therapy beyond three years.
Only one study (Mandall 2010) reported on adverse effects and showed no changes in TMJ signs and symptoms as a result of facemask therapy.
Chin cup therapy
We found two studies (Abdelnaby 2010; Arun 1994) showing evidence that the use of a chin cup led to statistically significant benefit in ANB when compared to an untreated control. A meta-analysis was not possible due to missing data from one study (Arun 1994). Again, the studies were short-term and there was no evidence of any long-term benefit.
There was no statistically significant difference found between the use of 300 g and 600 g forces when used with the chin cup.
Tandem traction bow appliance (TTBA)
One study (Atalay 2010) reported results on the use of the TTBA when compared with an untreated control. It showed that there was a statistically significant benefit in favour of the TTBA. Again, the study was short-term and there was no evidence for long-term benefit.
One study (Arun 1994) reported results on the use of mandibular headgear compared to an untreated control and the chin cup. Statistical analysis was not possible due to missing data, however it was reported that there was significant benefit in favour of the mandibular headgear with respect to ANB when compared to the untreated control. There was no statistically significant difference between the mandibular headgear and the chin cup.
Overall completeness and applicability of evidence
Overall, seven studies were found investigating multiple comparisons to treat prominent lower front teeth in children; they reported multiple outcomes. Four of the studies investigated the facemask, two the chin cup, one the Tandem traction bow appliance and one mandibular headgear. Only one study investigated outcomes beyond the treatment phase and, to date, that was only at three years follow-up. This has major implications for the applicability of the evidence. An aim of early intervention for a Class III malocclusion is to prevent subsequent need for corrective orthognathic surgery. The current evidence does not allow us to assess if any of the interventions have succeeded in this aim due to their short-term nature.
The concern of many patients seeking treatment for a Class III malocclusion is that their lower front teeth meet in front of their upper front teeth and therefore they have a reverse overjet. However, only two of the studies (Atalay 2010; Mandall 2010) reported overjet as an outcome.
Only one study (Mandall 2010) carried out an a priori sample size calculation and it is likely that the Keles 2002 and Vaughn 2005 studies were underpowered to find a difference between their facemask groups.
The lack of accurate reporting, especially with respect to unclear methodology and, in one case, missing statistical data, means much of the evidence was of low or very low quality and the results must be interpreted with caution.
Quality of the evidence
The evidence regarding overjet and ANB changes when comparing the use of a facemask with an untreated control has been graded as moderate. This implies that further research is likely to have an important impact on our confidence in the estimate of effect. It may change the estimate but is unlikely to overturn the direction of the effect.
All other comparisons and outcomes have been graded as a low or very low level of evidence. The reasons for this are the low number of studies and participants, the unclear or high risk of bias in these studies, and in the meta-analysis the high level of heterogeneity.
Potential biases in the review process
Bias has been reduced in this systematic review by using a broad, sensitive search of multiple databases with no restrictions on language. We have also searched for unpublished studies and data, and have included studies reported in all languages.
Agreements and disagreements with other studies or reviews
de Toffol 2008; Jager 2001 and Kim 1999 all report the efficacy of the facemask with greater confidence than we have reported. The difference in confidence is due to the greater number of studies that the other systematic reviews have included. This discrepancy is due to the different inclusion criteria used in our systematic review when compared to the previous reviews. We have only included prospective randomised controlled trials, whilst the other reviews have included retrospective studies, which are more susceptible to bias.
The review by Kim 1999 supports the use of rapid maxillary expansion prior to facemask therapy, whilst we have found insufficient evidence to support this protocol. Again, the difference is due to the inclusion of retrospective studies in the previous review.
Liu 2011 reports on the efficacy of the chin cup appliance and agrees with our conclusion that there are insufficient data in the current studies to make clear recommendations regarding the efficacy of chin cup therapy.
Implications for practice
There is low quality evidence that the use of facemask therapy between the ages of six to 10 years leads to short-term improvements in overjet and ANB. There is insufficient high quality evidence to comment on the long-term benefits.
Due to the lack of evidence we remain uncertain as to the benefits of any other appliances in the early treatment of prominent lower front teeth in children.
Implications for research
In view of the quality of the studies identified in this systematic review, it has been difficult to draw definitive conclusions. This review suggests the need for more long-term, well designed and reported randomised controlled clinical studies to assess the efficacy of early orthodontic treatment of prominent lower front teeth.
When designing future studies, the following need to be considered.
We would like to acknowledge the contributions of Kevin O'Brien and Bill Shaw to the protocol and earlier versions of this review. The foundation of the current review was undertaken by Sylvia Bickley, Jayne Harrison and Kevin O'Brien. We would like to thank Zipporah Iheozor-Ejiozor (Cochrane Oral Health Group) for her help with the completion of the review and Anne Littlewood (Cochrane Oral Health Group) for developing the search strategy and undertaking the electronic searches.
Data and analyses
- Top of page
- Summary of findings [Explanations]
- Authors' conclusions
- Data and analyses
- Contributions of authors
- Declarations of interest
- Sources of support
- Index terms
Appendix 1. Cochrane Oral Health Group's Trials Register search strategy
A search was undertaken using the Cochrane Register of Studies and the search strategy below:
#1 ("prominent lower front teeth" or underbite* or under-bite* or "under bite*" or reverse-bite* or "reverse bite*" or prognath* or "Malocclusion Angle Class III" or "Angle* class III") AND (INREGISTER)
#2 (("Class III" AND (malocclusion or bite))) AND (INREGISTER)
#3 (#1 or #2) AND (INREGISTER)
#4 (("orthodontic appliance*" OR "orthodontic device*" OR "removable appliance*" OR "removable device*" OR "functional appliance*" OR "functional device*" OR "fixed appliance*" OR "growth modif*" or brace* OR ((extraoral OR "extra oral" or extra-oral) AND traction) OR "chin cap*" or chin-cap* or chincap* OR "chin cup*" or chin-cup* or chincup* or "face mask*" OR facemask* or face-mask* OR "reverse head gear" OR "reverse head-gear")) AND (INREGISTER)
#5 (((orthopedic* OR orthopaedic*) AND (dental OR orthodontic* OR facial))) AND (INREGISTER)
#6 (#4 or #5) AND (INREGISTER)
#7 (#3 AND #6) AND (INREGISTER)
A previous search of the Register was undertaken in July 2011 using the Procite software and the search strategy below:
(("prominent lower front teeth" or underbite* or under-bite* or "under bite*" or reverse-bite* or "reverse bite*" or prognath* or "Malocclusion Angle Class III" OR "Angle* class III" OR ("Class III" AND (malocclusion* OR bite))) AND ("orthodontic appliance*" OR "orthodontic device*" OR "removable appliance*" OR "removable device*" OR "functional appliance*" OR "functional device*" OR "fixed appliance*" OR "growth modif*" or brace* OR ((extraoral OR "extra oral" or extra-oral) AND traction) OR "chin cap*" or chin-cap* or chincap* OR "chin cup*" or chin-cup* or chincup* or "face mask*" OR facemask* or face-mask* OR "reverse head gear" OR "reverse head-gear" OR ((orthopedic* OR orthopaedic*) AND (dental OR orthodontic* OR facial))))
Appendix 2. Cochrane Central Register of Controlled Trials (CENTRAL) search strategy
#1 MeSH descriptor Malocclusion, Angle Class III
#2 ("Class III" in All Text and (Angle in All Text or Angle's in All Text or malocclusion* in All Text or bite* in All Text))
#3 (underbite* in All Text or under-bite* in All Text or "under bite*" in All Text or "reverse bite*" in All Text or reverse-bite* in All Text or prognath* in All Text)
#4 "prominent lower front teeth”
#5 (#1 or #2 or #3 or #4)
#6 MeSH descriptor Orthodontic Appliances, Functional explode all trees
#7 MeSH descriptor Orthodontic Appliances, Removable explode all trees
#8 ("growth modif*" in All Text and (jaw in All Text or maxilla* in All Text or mandible in All Text))
#9 (("fixed appliance*" in All Text or brace* in All Text) and orthodontic* in All Text)
#10 ((extraoral in All Text or extra-oral in All Text or "extra oral" in All Text) and traction in All Text)
#11 ("chin cap*" in All Text or chin-cap* in All Text or chincap* in All Text)
#12 (("face mask*" in All Text or face-mask* in All Text or facemask* in All Text or "reverse head-gear" in All Text or "reverse headgear" in All Text) and orthodontic* in All Text)
#13 ((orthopedic* in All Text or orthopaedic* in All Text) and (dental in All Text or orthodontic* in All Text or facial in All Text))
#14 (#6 or #7 or #8 or #9 or #10 or #11 or #12 or #13)
#15 (#5 and #14)
Appendix 3. MEDLINE (OVID) search strategy
1. Malocclusion, Angle Class III/
2. ("Class III" and (Angle or Angle's or malocclusion$ or bite$)).mp.
3. (underbite$ or under-bite$ or "under bite$" or "reverse bite$" or reverse-bite$ or prognath$).mp.
4. "prominent lower front teeth".mp.
6. exp Orthodontic Appliances, Functional/
7. exp Orthodontic Appliances, Removable/
8. ("growth modif$" and (jaw or maxilla$ or mandible)).mp.
9. (("fixed appliance$" or brace$) and orthodontic$).mp.
10. ((extraoral or extra-oral) and traction).mp.
11. "chin cap$".mp.
12. (("face mask$" or facemask$ or face-mask$ or "reverse head-gear" or "reverse headgear") and orthodontic$).mp.
13. ((orthopedic$ or orthopaedic$) and (dental or orthodontic$ or facial)).mp.
15. 5 and 14
The above subject search was linked to the Cochrane Highly Sensitive Search Strategy (CHSSS) for identifying randomised trials in MEDLINE: sensitivity maximising version (2008 revision) as referenced in Chapter 220.127.116.11 and detailed in box 6.4.c of theCochrane Handbook for Systematic Reviews of Interventions, Version 5.1.0 (updated March 2011).
1. randomized controlled trial.pt.
2. controlled clinical trial.pt.
5. drug therapy.fs.
10. exp animals/ not humans.sh.
11. 9 not 10
Appendix 4. EMBASE (OVID) search strategy
2. ("Class III" and (Angle or Angle's or malocclusion$ or bite$)).mp.
3. (underbite$ or under-bite$ or "under bite$" or "reverse bite$" or reverse-bite$ or prognath$).mp.
4. "prominent lower front teeth".mp.
6. Orthodontic device/
7. ("growth modif$" and (jaw or maxilla$ or mandible)).mp.
8. (("fixed appliance$" or brace$) and orthodontic$).mp.
9. ((extraoral or "extra oral" or extra-oral) and traction).mp.
10. ("chin cap$" or chin-cap$ or chincap$).mp.
11. ((facemask$ or face-mask$ or "face mask$" or "reverse headgear" or "reverse head-gear") and orthodontic$).mp.
12. ((orthopedic$ or orthopaedic$) and (dental or orthodontic$ or facial)).mp.
14. 5 and 13
The above subject search was linked to the Cochrane Oral Health Group filter for EMBASE via OVID:
3. (crossover$ or cross over$ or cross-over$).ti,ab.
5. (doubl$ adj blind$).ti,ab.
6. (singl$ adj blind$).ti,ab.
10. CROSSOVER PROCEDURE.sh.
11. DOUBLE-BLIND PROCEDURE.sh.
12. RANDOMIZED CONTROLLED TRIAL.sh.
13. SINGLE BLIND PROCEDURE.sh.
15. ANIMAL/ or NONHUMAN/ or ANIMAL EXPERIMENT/
17. 16 and 15
18. 15 not 17
19. 14 not 18
Protocol first published: Issue 1, 2002
Review first published: Issue 9, 2013
Contributions of authors
The review was co-ordinated by Jayne Harrison (JH) and Simon Watkinson (SW). SW undertook the handsearching. SW, JH and Sue Furness (SF) screened the search results and retrieved papers, appraised the quality of the papers and extracted data from them. SF checked the data extraction. SF and Helen Worthington (HW) analysed and interpreted the data. SW, SF, HW and JH wrote the review.
Declarations of interest
Simon Watkinson: no interests to declare.
Jayne E Harrison: no interests to declare.
Susan Furness: no interests to declare.
Helen V Worthington: no interests to declare.
Sources of support
- The Royal Liverpool and Broadgreen University Hospitals NHS Trust, UK.
- School of Dentistry, The University of Manchester, UK.
- The University of Liverpool, UK.
- Manchester Academic Health Sciences Centre (MAHSC), UK.The Cochrane Oral Health Group is supported by MAHSC and the NIHR Manchester Biomedical Research Centre
- NHS National Primary Dental Care R&D programme, UK.PDC 97-303
- Cochrane Oral Health Group Global Alliance, UK.All reviews in the Cochrane Oral Health Group are supported by Global Alliance member organisations (British Orthodontic Society, UK; British Society of Paediatric Dentistry, UK; British Society of Periodontology, UK; Canadian Dental Hygienists Association, Canada; National Center for Dental Hygiene Research & Practice, USA; New York University College of Dentistry, USA; and Royal College of Surgeons of Edinburgh, UK) providing funding for the editorial process (http://ohg.cochrane.org/)
- National Institute for Health Research (NIHR), UK.CRG funding acknowledgement:
The NIHR is the largest single funder of the Cochrane Oral Health Group
The views and opinions expressed therein are those of the authors and do not necessarily reflect those of the NIHR, NHS or the Department of Health
Medical Subject Headings (MeSH)
MeSH check words
Adolescent; Child; Humans
* Indicates the major publication for the study