Orthodontic treatment for prominent lower front teeth (Class III malocclusion) in children

Abstract

Background: 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. Objectives: To assess the effects of orthodontic treatment for prominent lower front teeth in children and adolescents. Search methods: 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). Selection criteria: 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. Data collection and analysis: 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. Main results: 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. Authors' conclusions: 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.