Hu Long1, Fan Jian1, Wenli Lai1. 1. Department of Orthodontics, State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Chengdu, China.
Abstract
DATA SOURCES: Data sources The Cochrane Oral Health Group's Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), Medline and Embase. STUDY SELECTION: Randomised controlled trials (RCTs) of orthodontic treatment to correct prominent lower front teeth were included. DATA EXTRACTION AND SYNTHESIS: Study screening, risk of bias assessment and data extraction were carried out independently by two reviewers. The mean differences with 95% confidence intervals were calculated for continuous data. Meta-analysis was undertaken when studies of similar comparisons reported comparable outcome measures. A fixed-effect model was used. The l(2) statistic was used as a measure of statistical heterogeneity. RESULTS: Seven RCTs (339 patients) were included in this review. One study was assessed as at low risk of bias, three at high risk of bias and three at unclear risk. 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.Three studies (n = 155, low quality evidence) reported ANB 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. 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.
DATA SOURCES: Data sources The Cochrane Oral Health Group's Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), Medline and Embase. STUDY SELECTION: Randomised controlled trials (RCTs) of orthodontic treatment to correct prominent lower front teeth were included. DATA EXTRACTION AND SYNTHESIS: Study screening, risk of bias assessment and data extraction were carried out independently by two reviewers. The mean differences with 95% confidence intervals were calculated for continuous data. Meta-analysis was undertaken when studies of similar comparisons reported comparable outcome measures. A fixed-effect model was used. The l(2) statistic was used as a measure of statistical heterogeneity. RESULTS: Seven RCTs (339 patients) were included in this review. One study was assessed as at low risk of bias, three at high risk of bias and three at unclear risk. 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.Three studies (n = 155, low quality evidence) reported ANB 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. 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.