There are many different ways of treating patients with prominent (or sticking out) lower front teeth. Orthodontic treatment for children and adolescents is one method used. This review, carried out by authors of the Cochrane Oral Health Group, sought to establish which is the most effective type of orthodontic treatment when carried out in childhood; whether these treatments reduce the need for treatment as an adult; and at what age these treatments are best carried out to ensure that changes made to the shape of the jaw and the positioning of the teeth last until the end of growth and can be maintained into adulthood.
In severe cases, people may need surgery as adults to correct this condition. If a successful approach to treatment in childhood were to be found, with long-lasting effects, this kind of surgery may not be necessary. Additionally, the risk of damage to teeth and joints, together with the negative psychological effects associated with the condition, could be lessened or avoided.
Prominent lower front teeth can be an important problem for some people and are usually due to the way the jaws meet together. This condition may be the source of teasing, problems eating, and occasionally problems with speech. The condition may also give rise to problems with the jaw joints in later life. Orthodontic treatment relies on the use of appliances of various kinds either inside or outside of the mouth that are fixed in some way to the teeth, and sometimes placed on parts of the head, to influence the growth of the jaws and position of teeth.
This review looked at the use of four different types of orthodontic treatment for correcting prominent lower front teeth in children.
-Facemask: an appliance rests on the forehead and chin, connected to the upper teeth with elastic bands that are placed by the wearer. Through this arrangement a balanced force is applied, which it is hoped will pull the upper teeth and jaw forwards and downward to correct the prominent lower teeth.
-Chin cup: an appliance rests on the chin with a strap around the back of the head. Forward growth of the lower jaw is resisted, correcting the prominence of the lower front teeth. Nothing is placed in the mouth.
-Mandibular headgear: a strap rests on the back of the head and is connected to the lower teeth. This resists forward growth of the lower teeth and jaw in order to correct the prominent lower front teeth.
-Tandem traction bow appliance: attachments are fixed to the top and bottom teeth. In the top attachment there is a hook on each side. A metal bar is placed in the lower attachment, which sits in front of the lower teeth. An elastic band can then be placed on each side to pull the top jaw forward and bottom jaw backwards, to correct the prominent lower teeth.
The evidence on which this review is based was found to be up to date as of 7 January 2013.
A total of seven suitable studies were identified and included in this review; they included 339 children aged from five to 11 years. There were roughly equal numbers of girls and boys in each study and participants were from different ethnic groups depending on where the study was carried out. Studies included were conducted in Turkey, Egypt, China, the United States of America and the United Kingdom.
This review found some evidence that the use of a facemask appliance can help to correct prominent lower front teeth on a short-term basis. There was no evidence available to show whether or not these short-term changes will still be maintained until the child is fully grown. There was not enough evidence to support any other types of treatment for prominent lower front teeth.
Quality of the evidence
The quality of the evidence for the use of a facemask was moderate to low, whilst the quality of the rest of the evidence was very low.
There is some evidence that the use of a facemask to correct prominent lower front teeth in children is effective when compared to no treatment on a short-term basis. However, in view of the general poor quality of the included studies, these results should be viewed with caution. Further randomised controlled trials with long follow-up are required.
Prominent lower front teeth (termed reverse bite; under bite; Class III malocclusion) may be due to a combination of the jaw or tooth positions 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. Various treatment approaches have been described to correct prominent lower front teeth in children and adolescents.
To assess the effects of orthodontic treatment for prominent lower front teeth in children and adolescents.
We searched the following databases: Cochrane Oral Health Group's Trials Register (to 7 January 2013), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 12), MEDLINE via OVID (1946 to 7 January 2013), and EMBASE via OVID (1980 to 7 January 2013).
Randomised controlled trials (RCTs) recruiting children or adolescents or both (aged 16 years or less) receiving any type of orthodontic treatment to correct prominent lower front teeth (Class III malocclusion). Orthodontic treatments were compared with control groups who received either no treatment, delayed treatment or a different active intervention.
Screening of references, identification of included and excluded studies, data extraction and assessment of the risk of bias of the included studies was performed independently and in duplicate by two review authors. The mean differences with 95% confidence intervals were calculated for continuous data. Meta-analysis was only undertaken when studies of similar comparisons reported comparable outcome measures. A fixed-effect model was used. The I2 statistic was used as a measure of statistical heterogeneity.
Seven RCTs with a total of 339 participants were included in this review. One study was assessed as at low risk of bias, three studies were at high risk of bias, and in the remaining three studies risk of bias was unclear. Four studies reported on the use of a facemask, two on the chin cup, one on the tandem traction bow appliance, and one on mandibular headgear. One study reported on both the chin cup and mandibular headgear appliances.
One study (n = 73, low quality evidence), comparing a facemask to no treatment, reported a mean difference (MD) in overjet of 4.10 mm (95% confidence interval (CI) 3.04 to 5.16; P value < 0.0001) favouring the facemask treatment. Two studies comparing facemasks to untreated control did not report the outcome of overjet. Three studies (n = 155, low quality evidence) reported ANB (an angular measurement relating the positions of the top and bottom jaws) differences immediately after treatment with a facemask when compared to an untreated control. The pooled data showed a statistically significant MD in ANB in favour of the facemask of 3.93 ° (95% CI 3.46 to 4.39; P value < 0.0001). There was significant heterogeneity between these studies (I2 = 82%). This is likely to have been caused by the different populations studied and the different ages at the time of treatment.
One study (n = 73, low quality evidence) reported outcomes of the use of the facemask compared to an untreated control at three years follow-up. This study showed that improvements in overjet and ANB were still present three years post-treatment. In this study, adverse effects were reported but due to the low prevalence of temporomandibular (TMJ) signs and symptoms no analysis was undertaken.
Two studies (n = 90, low quality evidence) compared the chin cup with an untreated control. Both studies found a statistically significant improvement in ANB, and one study also found an improvement in the Wits appraisal. Data from these two studies were not suitable for pooling.
A single study of the tandem traction bow appliance compared to untreated control (n = 30, very low quality evidence) showed a statistically significant difference in both overjet and ANB favouring the intervention group.
The remaining two studies did not report the primary outcome of this review.