Fixed functional appliances with multibracket appliances have no skeletal effect on the mandible: A systematic review and meta-analysis


Our aim was to assess the skeletal mandibular changes (anteroposterior and vertical) in circumpubertal patients with fixed functional appliances installed on multibracket appliances compared with untreated patients.


An open-ended electronic search of 4 databases (PubMed, Embase, Cochrane Library, and Web of Science) up to April 2014 was performed. Additional searches of relevant journals, reference lists of the retrieved articles, systematic reviews, and gray literature were performed. Specific inclusion and exclusion criteria were applied to identify relevant articles. Quality was evaluated using the Cochrane Collaboration risk of bias tool and the Newcastle-Ottawa scale for prospective controlled clinical trials. Meta-analyses were conducted with fixed and random effects models as appropriate. Statistical heterogeneity was also examined.


Seven articles were included in the qualitative synthesis and 5 in the meta-analysis. The included randomized controlled trials were at high risk of bias, and the methodologic quality of the prospective controlled clinical trials was high. Based on assessment of the fixed functional appliance phase in isolation, no difference in mandibular anteroposterior positional changes (SNB angle) (standard mean difference, 0.11°; 95% CI, −0.28, 0.50) was found between the treated and control groups. The vertical dimension was not influenced by the fixed functional appliance treatment.


There is little high-quality evidence concerning the relative influence of fixed functional appliances on skeletal and dentoalveolar changes. However, based on the limited evidence, it appears that they have little effect on the skeletal mandibular parameters.


  • Efficacy of fixed functional appliances in mandibular growth enhancement is debatable.

  • The evidence in hand is relatively weak.

  • Properly designed randomized clinical trials are required to establish treatment guidelines.

  • Mandibular growth cannot be enhanced by fixed functional appliances.

Skeletal Class II malocclusion is characterized by a sagittal discrepancy caused by mandibular retrusion or maxillary excess. The most common source is mandibular retrusion, which affects about one third of the population. Mandibular retrusion is managed in growing patients with functional appliances (removable and fixed) designed to alter the anteroposterior and vertical positions of the mandible and to induce supplementary mandibular growth and remodeling of the condyle.

Fixed functional appliances (FFA) are compliance-free, tooth-borne appliances. They do not require a second phase of treatment when used with multibracket appliances (MBA). They are classified into 4 groups: rigid, flexible, hybrid, and substitutes for elastics. They may be categorized into 2 major groups according to the timing of the MBA. The Herbst and the mandibular advancement repositioning appliance can be applied before the MBA. The Jasper jumper, Forsus Nitinol Flat Spring, Forsus FatigueResistant Device, Twin Force Bite Corrector, Sabbagh Universal Spring, and integrated Herbst require an alignment and leveling phase with the MBA in preparation for application on a rigid stainless steel archwire attached to the teeth through the MBA.

There is considerable debate as to whether FFAs can stimulate mandibular growth and potentially lead to lasting skeletal changes. Several systematic reviews have focused on the treatment effects of the removable functional appliance (RFA), FFA, or both. The results were either inconclusive or controversial, mostly indicating the lack of a significant skeletal effect. According to Perinetti et al, FFAs are effective in Class II treatment with skeletal effects in pubertal patients related to mandibular elongation with treatment. The authors acknowledged that this study was potentially confounded by variations in the duration of functional treatment (6-18 months). This limitation was caused by the inclusion of different treatment modalities. To evaluate the effectiveness of a therapy, inconsistencies between the appliances used should be eliminated, such as the differences in the mode of action of the appliance, the timing and duration of application, and the force delivered by the appliance, to allow for a fair comparison. To our knowledge, no previous systematic review has focused on the treatment of patients with skeletal Class II malocclusion with FFAs combined with MBAs.

The aim of this systematic review was to evaluate the skeletal mandibular changes (horizontal and vertical) in circumpubertal patients with FFA and MBA compared with untreated patients. The assessed outcomes included skeletal mandibular anteroposterior and vertical changes produced by the FFA with the MBA in growing subjects with Class II malocclusion assessed using cephalometric measurements. The following inclusion criteria were applied: (1) population of growing Class II subjects, (2) intervention of FFA with MBA, (3) comparator of untreated Class II subjects, and (4) outcomes of mandibular anteroposterior and vertical skeletal changes.

Material and methods

Protocol and registration

This systematic review was based on the PRISMA statement. The first step included the development of a protocol that was registered on the PROSPERO database, International Prospective Register of Systematic Reviews ( , CRD42014009741).

Information sources and search strategy

An open-ended survey of articles published up to April 2014 investigating the effects of functional appliances on mandibular changes was performed in the following electronic databases: PubMed, Cochrane Library, Embase, and Web of Science. The keywords used to identify the studies and the electronic search results are given in Table I . The search was complemented by (1) a manual search in the American Journal of Orthodontics and Dentofacial Orthopedics , Angle Orthodontist , European Journal of Orthodontics , and Journal of Orofacial Orthopedics ; and (2) a manual search of the reference lists from the retrieved articles and any available systematic reviews. Gray literature was also searched for relevant articles.

Table I
The search engines included, keywords, dates of searches, and data retrieved
Search engine Keywords Date Result Internal duplicates External duplicates Exclusion by title Exclusion by abstract Exclusion by full text Final
PubMed (functional appliances OR functional appliance) and Class II and (TMJ or mandib* or temporomandibular joint) 09/03/2014 550 2 0 412 77 57 2
Cochrane Library (functional appliances OR functional appliance) and Class II and (TMJ or mandib* or temporomandibular joint) 09/03/2014 90 0 79 11 0 0 0
Embase (functional appliances OR functional appliance) and Class II and (TMJ or mandib* or temporomandibular joint) 09/03/2014 153 1 127 21 3 0 1
Web of Science Class II and (functional appliance*) and (mandib* or TMJ or temporomandibular joint) 05/04/2014 570 6 489 62 8 4 1
Total 1363 9 695 506 88 60 4

The process of exclusion that led to the final list of included studies is presented.

Eligibility criteria

The retrieved articles were processed systematically and separately by 2 reviewers (R.A.R.I.) and (M.S.A.). Any disagreements were resolved by discussion between the reviewers and a third reviewer (M.M.S.F.) to reach a definitive decision. Inclusion and exclusion criteria are given in Table II .

Table II
Inclusion and exclusion criteria for selecting articles
Inclusion criteria
  • 1. Related human clinical trials (RCTs and nonrandomized prospective CCTs)

  • 2. Pertained to the treatment of skeletal Class II malocclusion

  • 3. Using FFA therapy with MBA

  • 4. Availability of a suitable untreated control group

  • 5. Treatment carried out so that FFA was fitted after alignment and leveling with MBA

  • 6. Applied to patients in the permanent dentition

  • 7. Set to evaluate the effect of the FFA immediately before and after placing it (not comprehensive treatment)

  • 8. Concerned with mandibular AP and vertical changes or TMJ changes by using lateral cephalometric radiographs or computed tomography scans or CBCT scans

  • 9. The outcome measure was evaluated by using linear or angular measurements

Exclusion criteria
  • 1. If it did not meet the inclusion criteria

  • 2. If it did not relate to this topic

  • 3. If it was related but had a different aim

  • 4. Abstracts, laboratory studies, descriptive studies, individual case reports, series of cases, reviews, studies of adult patients, retrospective studies, and meta-analyses were excluded

  • 5. Clinical studies including patients who had received previous treatment for their Class II malocclusion were also excluded

  • 6. Studies with patients who had concomitant treatment other than MBA

RCTs , Randomized controlled trials; CCTs , controlled clinical trials; FFA , fixed functional appliances; MBA , multibracket appliance; AP , anteroposterior; TMJ , temporomandibular joint.

Data items and collection

Two authors (R.A.R.I. and M.S.A.) independently extracted characteristics and outcomes from the included studies using predefined data extraction forms that were piloted on several articles and modified as required. The collected data included the study design and setting, sample description (size, age, sex distribution, and skeletal age assessment), selection criteria, and treatment details (appliance type, observation period, activation, or end of treatment).

Risk of bias and quality assessment in individual studies

The risk of bias of the included randomized controlled trials (RCTs) was assessed with the Cochrane Collaboration’s risk of bias tool. The following domains were considered: random sequence generation, allocation sequence concealment, blinding of outcome assessment, incomplete outcome data, selective outcome reporting, and other sources of bias. For all included trials, the risk of bias for each domain was judged as low risk, high risk, or unclear risk. Each RCT was assigned an overall score: low risk (low for all key domains), high risk (high for ≥1 key domain), and unclear risk (unclear for ≥1 key domain).

The Newcastle-Ottawa scale was applied to assess the quality of the nonrandomized controlled clinical trials. The Newcastle-Ottawa scale is based on 3 broad perspectives: selection of the study groups, comparability of the groups, and ascertainment of the outcome of interest. Further elaboration of the Newcastle-Ottawa scale and its application in this study are shown in Table III . The assessment of risk of bias and the methodologic scoring were performed independently by 2 investigators (R.A.R.I.) and (M.S.A.). Any disagreement was resolved by discussion with a third reviewer (M.M.S.F.)

Table III
Quality assessment for the nonrandomized prospective controlled clinical trials with the Newcastle-Ottawa scale
Item Authors and year
Nalbantgil et al, 2005 Küçükkeleş et al, 2007 Jena and Duggal, 2010 Oztoprak et al, 2012
Representativeness of the FFA group (true representation of the average in the community or somewhat representative of the average in the community) * * * *
Selection of the untreated control group (drawn from the same community of the FFA treated group) * *
Ascertainment of FFA treatment group (secured record by x-rays) * * * *
Demonstration that the outcome of interest was not present at the day of start (yes) * * * *
Comparability of the FFA group and control group (comparison of starting forms: baseline characteristics of age, sex, skeletal maturity, and skeletal characteristics) * *
Assessment of the outcome with independent blinding (independent blind assessment)
Was follow-up adequate enough for outcomes to occur? (Yes, an adequate follow up for short-term findings) * * * *
Loss to follow-up acceptable (complete follow-up, subjects lost to follow-up unlikely to introduce bias, description provided of those lost, small number of loss to follow up <10%) * * * *
Total quality (score) 6 (High) 5 (High) 6 (High) 7 (High)

This table presents each item on the Newcastle-Ottawa scale and explains when stars should be given in each step. The assessment consists of 3 sections. The selection included 4 items, with 1 star for each item. Comparability included 1 item with at most 2 stars for this item. Outcome included 3 items with 1 star at each item. The total quality score represents the quality of the study. If the total number of stars was less than 5, the study was low quality. Otherwise, it was a high-quality study. The quality assessment of each study is also presented. All included studies were of high quality according to this assessment.

Risk of bias across studies

If more than 10 studies were included in the meta-analysis, standard funnel plots and contoured enhanced funnel plots would be drawn to identify publication bias.

Summary measures and synthesis of results

Data were combined using Review Manager software, version 5.3 ( ). Statistical heterogeneity was explored using the chi-square–based Q statistic method and the I 2 index, with values of 25%, 50%, and 75% corresponding to low, moderate, and high heterogeneity, respectively. According to the I 2 test, the fixed-effects model and the random-effects model were applied to studies with less than 50% heterogeneity and greater than 50% heterogeneity, respectively. The Tau 2 test was also calculated for the heterogeneity in the random-effects model. The combined data were expressed as mean differences and 95% confidence interval (95% CI). Combined data with pooled measurements or measuring tools were expressed as standard mean deviations and 95% CI. Measurements for sagittal and vertical mandibular changes were combined according to similarity.

Additional analyses

Subgroup analyses were performed when possible to evaluate the effect of pubertal status. In studies including 2 or more treated groups compared with 1 control group, data from the treated groups were pooled according to the Cochrane Handbook indications. The significance level was set at P <0.05 (2-tailed z tests). Outcomes that were not included in the meta-analysis were presented separately.


Study selection

Details of the search and the study selection are shown in Figure 1 . Among the 1366 initially identified relevant articles, 662 unique citations remained after removal of duplicates. A total of 594 articles were excluded on the basis of title and abstract, and 61 articles were excluded on the basis of their full texts. Finally, 7 articles were selected for the qualitative evaluation, and only 5 were deemed appropriate for inclusion in the meta-analysis.

Fig 1
PRISMA flowchart for the steps of the systematic review.

Study characteristics and risk of bias in studies

The systematic review included 1 RCT, 2 quasi-RCTs, and 4 prospective controlled clinical trials. The RCTs were all judged to be at high risk of bias ( Table IV ). The prospective controlled clinical trials were judged to be of high quality according to the Newcastle-Ottawa scale ( Table III ).

Table IV
Assessment of risk of bias (ROB) for the included RCTs
Author and year Random sequence generation (selection bias) Allocation concealment (selection bias) Blinding of outcome assessment (detection bias) Incomplete outcome data (attrition bias) Selective reporting (reporting bias) Other bias Overall ROB
Karacay et al, 2006 Unclear Unclear Unclear Low Low High High
Bilgiç et al, 2012 High Unclear Unclear Low Low High High
Elkordy et al, 2015 Low Low High Low Low Low High
This table presents the assessment of ROB in the included studies. It was based on 6 domains. The domain “blinding of participants and personnel” was not assessed, since it was judged to be unfeasible. A study was judged as follows: low ROB (if low risk in all domains), high ROB (if high risk in at least 1 domain), or unclear ROB (if unclear in at least 1 domain). All included studies were judged to be at high ROB.

All included studies were conducted in a university setting ( Table V ). The ages of the study and control subjects ranged from 11.2 to 15.2 years and from 10.9 to 15.1 years, respectively. Two studies clearly described the ages of the male and female participants separately. The studies of Jena and Duggal and Elkordy et al had girls only. Sex distribution in the study group was mentioned in all studies, whereas in the control group it was mentioned in 3 studies and not mentioned in 2 studies.

Apr 4, 2017 | Posted by in Orthodontics | Comments Off on Fixed functional appliances with multibracket appliances have no skeletal effect on the mandible: A systematic review and meta-analysis
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