A Cochrane review [Abstract] 1 included 17 studies with a total of 721 subjects (age 16 years or less) receiving orthodontic treatment to correct prominent upper front teeth (Class II malocclusion). Three trials (n = 343) compared early (two-phase) treatment (7-11 years of age) with a functional appliance, with adolescent (one-phase) treatment. Statistically significant differences in overjet, ANB and PAR scores were found in favour of functional appliance when the first phase of early treatment was compared with observation in the children due to receive treatment in adolescence. However, at the end of treatment in both groups, there was no evidence of a difference in the overjet (MD 0.21, 95% CI -0.10 to 0.51), final ANB (MD -0.02, 95% CI -0.47 to 0.43), PAR score (MD 0.62, 95% CI -0.66 to 1.91) or self concept score (MD 0.83, CI -2.31 to 3.97). However, two-phase treatment with functional appliance showed a statistically significant reduction in the incidence of incisal trauma (OR 0.59, 95% CI 0.35 to 0.99). The incidence of incisal trauma was clinically significant with 29% (54/185) of patients reporting new trauma incidence in the adolescent (one-phase) treatment group compared to only 20% (34/172) of patients receiving early (two-phase) treatment.
Two trials (n = 285), compared early (two-phase) treatment using headgear, with adolescent (one-phase) treatment. Statistically significant differences in overjet and ANB were found in favour of headgear when the first phase of early treatment was compared with observation in the children due to receive treatment in adolescence. However, at the end of treatment in both groups, there was no evidence of a difference in the overjet (MD 0.22, 95% CI -0.56 to 0.12), final ANB (MD -0.27, 95% CI -0.80 to 0.26) or PAR score (MD -1.55, 95% CI -3.70 to 0.60). The incidence of incisal trauma was, however, statistically significantly reduced in the two-phase treatment group (OR 0.47, 95% CI 0.27 to 0.83). The adolescent treatment group showed twice the incidence of incisal trauma (47/120) compared to the young children group (27/117).
Two trials (n = 282) compared different types of appliances (headgear and functional appliance) for early (two-phase) treatment. At the end of the first phase of treatment statistically significant differences, in favour of functional appliances, were shown with respect to final overjet only. At the end of phase two, there was no evidence of a difference between appliances with regard to overjet (MD -0.21, 95% CI -0.57 to 0.15), final ANB (MD -0.17, 95% CI -0.67 to 0.34), PAR score (MD -0.81, 95% CI -2.21 to 0.58) or the incidence of incisal trauma (OR 0.79, 95% CI 0.43 to 1.44).
Late orthodontic treatment for adolescents with functional appliances showed a statistically significant reduction in overjet of -5.22 mm (95% CI -6.51 to -3.93, P < 0.00001) and ANB of -2.37° (95% CI -3.01 to -1.74, P < 0.00001) when compared to no treatment (very low quality evidence).
There was no evidence of a difference in overjet when Twin Block was compared to other appliances (MD 0.01, 95% CI -0.45 to 0.48). However, a statistically significant reduction in ANB (-0.63°, 95% CI -1.17 to -0.08) was shown in favour of Twin Block. There was no evidence of a difference in any reported outcome when Twin Block was compared with modifications of Twin Block. There was insufficient evidence to determine the effects of Activator, FORSUS FRD EZ appliances, R-appliance or AIBP.
Comment: The quality of evidence is downgraded by study limitations (unclear allocation concealment, lack of blinding and selective outcome reporting) and by imprecise results (few patients and wide confidence intervals).
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