Nikolaos Pandis DDS, MS, dr. med. dent
The effects of treatment on mandibular growth with functional appliances versus untreated controls in mixed dentition showed clinically insignificant skeletal changes.
Heterogeneity in baseline characteristics, interventions and outcome assessment weakened the strength of the evidence.
In mixed-dentition patients, what is the short-term effectiveness of functional appliances (FAs) compared to untreated controls on mandibular dimensions?
The authors searched six databases for articles published in any language up to September 2009. They also hand searched the reference lists of retrieved articles. They did only consider literature published in regular journals. For inclusion, the studies had to meet the following criteria: be randomized controlled trials (RCTs); use functional appliances for treatment of Class II malocclusion; and compare with an untreated control group, among others. The authors considered only one time articles that reported interim outcomes or updates. Two independent reviewers attained consensus during study selection, data abstraction and quality assessment. The studied outcome was the increase in total mandibular length as measured from the condylion. Both annualized standardized mean differences (SMD) and data synthesis were calculated using the random-effects model in the meta-analyses. Statistical heterogeneity was assessed (I2) and sensitivity analyses were undertaken.
Four RCTs met the inclusion criteria (338 participants, of which 168 were in the treatment group and 170 in the control group). Heterogeneity in age, interventions, and outcomes were observed, and follow-up times ranged from 15 to 18 months. Two RCTs had a low risk of bias, and one trial had a high risk of bias. The risk of bias for another trial was unclear. Independent quality as assessed by two reviewers showed very good agreement (k statistic = 0.75). Meta-analysis showed that the average effect was a increase of 1.79 mm (a statistically significant finding) in the annual mandibular growth in comparison to the control group (SMD = 0.61, 95 percent confidence interval, 0.30 to 0.93).
The analysis of mandibular skeletal effect in mixed dentition cases with FAs versus an untreated control revealed that the increases in skeletal changes are statistically significant, but clinically insignificant .
Source of Funding:
Importance and Context:
Mandibular retrusion is a major contributing factor of Class II malocclusion, occurring in one-third of the population1. Functional appliances are intended to treat Class II malocclusion by stimulating mandibular growth at the condylar cartilage.2 However, their effectiveness remains controversial2-3. Previous systematic reviews3-4 explored this controversy but this review does approach the issue differently.
Strengths and Weaknesses of the Systematic Review:
The authors conducted a thorough systematic review with defined inclusion and exclusion criteria. They provided a list of search terms as well as reasons for study exclusions. Two independent reviewers selected studies, abstracted data, and duplicated quality assessments using separate printed forms. They performed meta-analysis by standardizing the different values of mandibular growth in the selected studies. The authors did not report if reviewers were blinded, nor did they discuss risks of publication biases. Reporting could have been improved.
Strengths and Weaknesses of the Evidence:
Of the included studies, two were at low risk of bias, one was at high risk of bias, and one had an unclear risk of bias. The quality of the evidence was weakened by the small sample sizes of the studies, heterogeneity among their baseline characteristics, the different types of study interventions and their corresponding outcomes. Additionally recording of outcomes using two dimensional images introduces errors which may affect interpretation That the studies comprised many different cephalometric analyses, different variables and reference points also weakens the strength of the evidence.
Implications for Dental Practice:
Successful treatment of Class II malocclusion using FAs is related to increases in mandibular length and to restrictions in maxillary growth restriction5,6, to profile changes6 and to dentoalveolar compensations4,5. The authors' research question was too narrow for the purposes of this systematic review. There is limited evidence that, in the short-term, FAs enhance mandibular growth during mixed dentition. However, these results, when considered independently of other simultaneous changes, have little clinical significance.
1.McNamara JA Jr. Components of Class II malocclusions in children 8-10 years of age. Angle Orthod 1981; 51:177-202. 2. Croft RS, Buschang PH, English JD, Meyer R. A cephalometric and tomographic evaluation of Herbst treatment in the mixed dentition. Am J OrthodDentofacialOrthop 1999;116:435-43. 3. Cozza P, Baccetti T, Franchi L, De Toffol L, McNamara JA Jr. Mandibular changes produced by functional appliances in Class II malocclusion: a systematic review. Am J Orthod Dentofacial Orthop. 2006 May;129(5):599.e1-12; discussion e1-6. Review. 4. Barnett GA, Higgins DW, Major PW, Flores-Mir C. Immediate skeletal and dentoalveolar effects of the crown- or banded type Herbst appliance on Class II division 1 malocclusion. Angle Orthod. 2008;78:361-9. 5. Harrison JE, O'Brien KD, Worthington HV. Orthodontic treatment for prominent upper front teeth in children. Cochrane Database Syst Rev. 2007 Jul 18;(3):CD003452. 6. Flores-Mir C, Major PW. A systematic review of cephalometric facial soft tissue changes with the Activator and Bionator appliances in Class II division 1 subjects.Eur J Orthod. 2006;28:586-93.