Functional Mandibular Advancer Research Articles

Effectiveness of Functional Mandibular Advancer in Patients with Class II Malocclusion: A Systematic Review and Meta-analysis.

We aimed to evaluate the effectiveness of functional mandibular advancer (FMA) in treating growing patients with Class II malocclusion. Electronic searches were conducted in MEDLINE (via PubMed), Cochrane Library, Web of Science, Scopus, Embase, and Lilacs from 1945 to 30th November 2021. Studies were selected based on the following inclusion criteria: human studies, Class II growing patient treated with FMA, untreated control group or a comparable group treated with another fixed functional appliance, pre- and post-treatment lateral cephalograms/magnetic resonance imaging/cone-beam computed tomography, randomized clinical trials, prospective studies, and retrospective studies. Data extraction of the included articles was independently performed independently by two authors. The risk of bias was assessed using the ROBINS-I tool. Meta-analysis was performed using the inverse generic model. Seven articles met the criteria and were included in the systematic review and three articles were included in the meta-analysis. Three studies had at low risk of bias and four studies had a moderate risk of bias. All articles reported anterior positioning of the mandible along with an increase in mandibular length. The meta-analysis results indicated a negligible difference between FMA and other functional appliances for the parameters SNA [0.11, 95% confidence interval (CI) of -1.07 and 1.29] and ANB (-1.00, 95% CI of -1.34 and -0.65). The evidence was limited for soft tissue changes. Class II correction with FMA involved a combination of skeletal and dentoalveolar changes and was similar to other fixed functional appliances.

Changes of epiglottis and hyoid bone position after orthodontic treatment with cast splint fixed functional appliances.

Angle Class II malocclusions including a retrognathic mandible are the most frequent orthodontic problems. Both removable and fixed functional appliances can be used for mandibular advancement. Mandibular advancement after treatment with any fixed functional appliance has numerous therapeutic effects, such as stretching of masticatory muscles, ligaments, membranes and surrounding soft tissues, thus causing positional changes of the hyoid bone and epiglottis. This retrospective study investigates and compares treatment effects upon epiglottis- and hyoid bone position and posterior airway space in class II patients who received mandibular advancement through two different cast splint fixed functional appliances. Two groups of 21 patients each ('Functional Mandibular Advancer' (FMA) and Herbst appliance) were investigated. The same experienced orthodontist performed the treatment in all patients, employing a single-step advancement protocol. The mandible always received initial protrusion into an edge-to-edge position. Conventional lateral cephalograms were available pre-treatment (T1) and immediately after appliance removal (T2) for all patients. The measurements comprised (I) hyoid bone, (II) epiglottis or (III) posterior airway space. Treatment-related changes were analysed with one-sample Student's t tests for intragroup comparisons and independent Student's t tests for intergroup comparisons. Statistical significance was set at p < 0.05. Measurements of the hyoid bone showed mostly increases for both appliances after treatment. Intergroup comparisons were not significant for FMA patients but significant for selected measurements in Herbst appliance patients. Intergroup comparisons showed insignificant changes. The posterior airway space was always insignificantly increased after treatment. The greatest increase was found caudally. Intergroup comparisons showed insignificant changes. Both fixed functional appliances cause an anterior and caudal displacement of epiglottis and hyoid bone and enlarge the posterior airway space. The therapeutic effects of the Herbst appliance are slightly larger, although not significantly. Treatment with either Herbst appliance of FMA alters the hyoid bone position and enlarges the posterior airway space. Still, long-term data are as yet unavailable; it remains unknown if the effects upon posterior airway space remain stable, and if a resulting posterior airway space enlargement may have clinical influence upon obstructive sleep apnoea syndrome.

Comparison of 2 treatment protocols using fixed functional appliances in Class II malocclusion: Treatment results and stability

The objective of this research was to compare the 2 treatment protocols including a functional mandibular advancer (FMA; Forestadent, Pforzheim, Germany) followed by multibracket appliances (MBAs) vs a Forsus device (3M Unitek, Monrovia, Calif) in combination with MBA concerning treatment outcomes and posttreatment stability. This study was conducted using lateral cephalograms of patients who were treated with MBA, which was used either after an FMA or concurrently with a Forsus device, and of patients who had untreated Class II malocclusion (control group). Each group consisted of 19 subjects in cervical stage 2 or cervical stage 3 stages according to the cervical vertebral maturation index. Cephalograms were taken for the treated groups at T1 (pretreatment), T2 (completion of the MBA treatment), and T3 (at least 2years after T2). Significant intergroup differences at the T1-T2 period were observed in favor of the FMA concerning mandibular advancement, intermaxillary relationship, and mandibular elongation. With Forsus treatment, restrained maxillary growth and a slightly improved intermaxillary relationship rebounded after treatment (P<0.05). At the end of treatment, mandibular incisor protrusion and occlusal plane rotation were greater in the Forsus group than in the FMA group (P<0.05), and maxillary incisor retroclination was significant in the Forsus group. During the posttreatment period, although no significant changes were present in the incisors' inclination, relapses of the T1-T2 improvements in overjet and overbite and the recidive of the occlusal plane rotation were significantly higher in the Forsus group. Treatment protocol including an FMA was found to be more effective with mandibular skeletal effects and was more stable with a lesser degree of relapse in overjet and overbite than the Forsus protocol.

Are morphologic and topographic alterations of the mandibular fossa after fixed functional treatment detectable on tomograms? Visual classification and morphometric analysis.

The goal was to evaluate if changes in morphology and topography of the mandibular fossa after Functional Mandibular Advancer (FMA) treatment are detectable on tomograms. Furthermore, the suitability of digital tomograms (DT) over magnetic resonance imaging (MRI) for this particular question was investigated. In all, 25patients (14female, 11male) with askeletal classII malocclusion received treatment with aFMA. DTs were available prior to (T1) and after (T2) FMA treatment. Atotal of 50 temporomandibular joints were investigated. The mandibular fossae were evaluated metrically and visually regarding treatment-induced alterations. Ap < 0.05 was set as the level for statistical significance for all tests. Results were compared to the results of arecent MRI study. Visual inspection of all 50joints in the DT at T1 and T2 revealed no alterations of the fossa shape in the sagittal plane; 24patients showed identical morphology of right and left joints. The metrical analysis revealed no significant changes regarding width, depth and ratio thereof between T1 and T2. There also were no bilateral differences. Another 18 different distance measurements between porion, mandibular fossa, articular eminence and pterygoid fossa showed no significant changes. There was no detectable proof of afossa shift. No changes in the sagittal plane, mandibular fossa, the articular tubercle, or apossible fossa shift were found in the DT of classII patients after FMA treatment. DT and MRI measurements and the visual inspection revealed identical findings; thus, DT appears to be avaluable research tool for sagittal analysis of mandibular fossa changes.

Soft tissue profile changes after Functional Mandibular Advancer or Herbst appliance treatment in class II patients.

The objective of the present study is to compare the effects on soft tissue profile in class II patients after treatment with either "Functional Mandibular Advancer" (FMA) or Herbst appliance. The study included n=42 patients treated with either FMA (n=21) or Herbst appliance (n=21) by the same experienced orthodontist. The treatment followed a single-step advancement protocol. Lateral cephalograms were analyzed through a set of customized measurements. The actual therapeutic effect was calculated using data from a growth survey. After testing for normal distribution and homogeneity of variance, data were analyzed by one-sample Student's t tests and independent Student's t tests. Statistical significance was set at p<0.05. For both FFAs, significant upper lip retrusion, increase in lower lip's thickness, and length of the lower face occurred. Additionally, significant lower lip retrusion and straightening of the profile were found in FMA and Herbst appliance patients. All remaining variables revealed no significant differences. Treatment-related changes on the facial soft tissue profile could be regarded similar in class II patients treated with FMA or Herbst appliance. No treatment-related changes that were specific for FMA or Herbst appliance could be identified. Only moderate changes were noted comparing pre- and posttreatment soft tissue profiles. Despite proven differences in skeletal and dental treatment effects, the facial profile has not to be taken into consideration when choosing between FMA and Herbst appliance for class II treatment.

Patients' and Parents' Perception of Functional Appliances: A Survey Study.

To evaluate patients' and parents' perception of removable, fixed rigid, and fixed hybrid functional appliances and to compare their impacts on anxiety and discomfort during treatment in different age groups and genders. Data were gathered by means of a questionnaire that included items presumed to be associated with orthodontic compliance. A self-administered questionnaire was used to quantify patients' and parents' perceptions. Three groups were formed regarding the type of functional appliance used: fixed rigid (Functional Mandibular Advancer, FMA), fixed hybrid (Forsus Fatigue Resistant Device, FRD), and removable (Twin Block, TB). Two separate questionnaires were used for the patients and their parents comprising the necessary context. Chi-square, Mann-Whitney U, and Kruskal-Wallis tests were used for data analysis. Patients needed less time to adapt to the FRD appliance. Eating difficulties were encountered by patients in the FMA group. Adolescents who had completed functional orthodontic treatment with a removable appliance had difficulties in controlling their saliva. Patients' and parents' perceptions were found to be in accordance with each other. Adolescents who had completed functional orthodontic treatment with fixed appliances had more difficulty in their daily life. Orthodontists should be aware of this impact caused by functional orthodontic treatment and should regularly encourage patients by reminding them of the improvements to be had by fixing the malocclusion.

Upper airway changes following single-step or stepwise advancement using the Functional Mandibular Advancer.

Purpose of the present study was to determine and compare possible changes in the dimensions of the pharyngeal airway, morphology of the soft palate, and position of the tongue and hyoid bone after single-step or stepwise mandibular advancement using the Functional Mandibular Advancer (FMA). The sample included 51 peak-pubertal Class II subjects. In all, 34patients were allocated to two groups using matched randomization: a single-step mandibular advancement group (SSG) and a stepwise mandibular advancement group (SWG). Both groups were treated with FMA followed by fixed appliance therapy; the remaining 17 subjects who underwent only fixed appliance therapy constituted the control group (CG). The study was conducted using pre- and posttreatment lateral cephalometric radiographs. Data were analyzed by paired t test, one-way analysis of variance, and Pearson's correlation coefficient. In the SWG and SSG, although increases in nasopharyngeal airway dimensions were not significant compared with those in the CG, enlargements in the oropharyngeal airway dimensions at the level of the soft palate tip and behind the tongue, and decreases in soft palate angulation, were significant. Tongue height increased significantly only in the SWG. Compared with the CG, while forward movement of the hyoid was more prominent in SSG and SWG, the change in the vertical movement of the hyoid was not significant. No significant difference between SWG and SSG was observed in pharyngeal airway, soft palate, tongue or hyoid measurements. The mode of mandibular advancement in FMA treatment did not significantly affect changes in the pharyngeal airway, soft palate, tongue, and hyoid bone.

Comparison of stepwise vs single-step advancement with the Functional Mandibular Advancer in Class II division 1 treatment

To compare two groups of subjects at the peak of the pubertal growth period treated with the Functional Mandibular Advancer (FMA; Forestadent, Pforzheim, Germany) appliance using either single-step or stepwise mandibular advancement. This study was conducted on 34 Class II division 1 malocclusion subjects at or just before the peak phase of pubertal growth as assessed by hand-wrist radiographs. Subjects were assigned to two groups of mandibular advancement, using matched randomization. Both groups were treated with the FMA. While the mandible was advanced to a super Class I molar relation in the single-step advancement group (SSG), patients in the stepwise mandibular advancement group (SWG) had a 4-mm initial bite advancement and subsequent 2-mm advancements at bimonthly intervals. The material consisted of lateral cephalograms taken before treatment and after 10 months of FMA treatment. Data were analyzed by means paired t-tests and an independent t-test. There were statistically significant changes in SNB, Pg horizontal, ANB, Co-Gn, and Co-Go measurements in both groups (P < .001); these changes were greater in the SWG with the exception of Co-Go (P < .05). While significant differences were found in U1-SN, IMPA, L6 horizontal, overjet, and overbite appraisals in each group (P < .001), these changes were comparable (P > .05). Because of the higher rates of sagittal mandibular skeletal changes, FMA using stepwise advancement of the mandible might be the appliance of choice for treating Class II division 1 malocclusions.

Effects of fixed appliances in correcting Angle Class II on the depth of the posterior airway space

The objective of this retrospective study based on the metric evaluation of lateral cephalograms was to investigate the extent to which treatment with two different fixed appliances for the correction of Angle ClassII influenced the morphology of the extrathoracic airway space (the posterior airway space, PAS). A total of 43patients with Angle ClassII malocclusion were classified into two groups according to the appliance used for treatment: the functional mandibular advancer (FMA; n = 18) or the Herbst appliance (n = 25). Lateral cephalograms were taken of each patient at the start of functional jaw orthopedic treatment (time point T1) and at its completion (time point T2). Specific distances and angles were measured and analyzed in a cephalometric analysis. We observed major differences among the 43patients in the depth of the posterior airway space during treatment with fixed appliances for Angle ClassII correction. Regression analysis revealed that changes in sagittal and vertical positions had different effects on the depth of specific PAS sections: increases in anterior facial height are associated proportionately with increases in PAS width, particularly in the upper region. On the other hand, increases in posterior facial height and in the mandible's forward displacement correlated inversely to the decreases in depth, particularly in the central and lower PAS regions. The two treatment appliances (FMA, Herbst appliance) had the same effects on extrathoracic airway depth. Analyses of lateral cephalograms indicate that Angle ClassII treatment with fixed appliances does not prevent sleep apnea in patients at risk. Nevertheless, this study does not permit absolutely reliable conclusions about the dimensions of the pharyngeal airway space. As the lateral cephalogram provides good images of structures in the midsagittal plane but is incapable of imaging the transverse dimension, there is an automatic lack of information concerning the precise width and volume of the extrathoracic airway space.

Class II Treatment with Fixed Functional Orthodontic Appliances before and after the Pubertal Growth Peak – A Cephalometric Study to Evaluate Differential Therapeutic Effects

The aim of this clinical trial was to investigate and compare outcomes after treating a skeletal Class II malocclusion with two fixed functional orthodontic appliances, the Herbst appliance and the Functional Mandibular Advancer, by evaluating their skeletal and dentoalveolar effects and the repercussion on the profile in relation to patient age. The sample population comprised 42 subjects with skeletal Class II malocclusion. They were divided into two groups depending on age. Group A (n = 21) included nine female subjects aged up to 12 years and twelve male subjects aged up to 14 years. Group B (n = 21) comprised twelve females older than 12 years and nine males older than 14 years. Treatment course was documented cephalometricly. The net therapeutic effects were calculated with reference to the control group. A significant reduction of the overjet was achieved in both treatment groups. Within the two groups there were no significant sagittal effects in terms of mandibular advancement. However, there was an inhibiting effect on the maxilla, which counteracted the natural growth process. Significant changes in vertical direction were detected mainly in the younger patients in the sense of lengthening of the lower face. Significant dental changes were predominantly found in the group of older patients. For instance, treatment with fixed functional orthodontic appliances led to retrusion of the upper incisors by a mean of 2.21 mm +/- 2.66 mm (p = 0.0015), protrusion of the lower incisors by a mean of 2.28 mm +/- 2.39 mm (p = <or= 0.0001) and distalization of the six-year molars by a mean of 1.12 mm +/- 2.15 mm (p = 0.0315). The skeletal and dental effects achieved by treatment did not correlate directly with the soft tissue adaptations. Generally speaking, far more significant effects on the soft tissue profile were identified in the younger patients. Significant reduction in convexity of the bony profile was similarly more pronounced than in the older age group (N-A-Pog: group A: -4.46 +/- 3.00 (p <or= 0.0001), group B: 3.93 +/- 3.25 (p <or= 0.0001). Only slight skeletal sagittal effects, which were independent of age, were observed as a result of treatment with fixed functional orthodontic appliances. The younger the patients, the greater any growth-inhibiting effect on the maxilla will be. There is a greater increase in facial height during treatment than would have been expected from growth without any such influence. The compensatory dental effects increase with patient age.

Disc-condyle Relationships during Class II Treatment with the Functional Mandibular Advancer (FMA)

The objective of this study was to verify the effects of treatment to correct Class II malocclusion with the Functional Mandibular Advancer (FMA) on the relative positions of the articular disc and mandibular condyle. In particular, we aimed to find out whether the disc-condyle relationship changed between baseline and post-treatment, in temporomandibular joints initially exhibiting a physiological relationship and alternatively, in temporomandibular joints initially presenting anterior displacement of the articular disc. Treatment progress in 15 patients was monitored at defined points in time by manual structural analysis (MSA) and magnetic resonance (MR) imaging. The disc-condyle relationship was assessed by examining the parasagittal MR images made up of three slices each (lateral, central, medial) taken in habitual intercuspation and maximum-open mouth position. The MR images were metrically analyzed to determine the sagittal positional relationship of the articular disc and mandibular condyle using two methods on the central slices of the images taken in closed-mouth position. MSA was used in particular to determine the disc-condyle relationships and to metrically record the extent of active movement of the mandible during mouth opening, protrusion, laterotrusion, and retrusion. Comparison of baseline and post-treatment findings revealed that none of the joints exhibited a treatment-induced deterioration in the disc-condyle relationship, while the relationship improved in five joints. After categorization of the joints according to groups according to disc position, metric analysis of the MR images showed significantly-improved post-treatment disc positions in the joints that had initially exhibited anterior disc displacement. Post-treatment findings for maximum-open mouth position, protrusion, and laterotrusion corresponded to the baseline values recorded before bite-jumping, and the extent of maximum active retrusion increased significantly. Functional jaw orthopedics for correction of skeletal Class II with the rigid fixed FMA leads to side-effects reflected in the disc-condyle relationship in the temporomandibular joints: no adverse effects were observed in joints presenting an initial physiological disc-condyle relationship, whereas the disc position may improve in joints with initial partial or total anterior disc displacement. In comparison with the baseline findings, we observed no post-treatment restriction in the extent of maximum mouth opening, protrusion, and left and right laterotrusion. Maximum active retrusion increased due to the treatment. MR imaging and MSA only partly cover the same aspects of temporomandibular joint diagnostics.

Skeletal Effects in Class II Treatment with the Functional Mandibular Advancer (FMA)?

The aim of this clinical study was to reveal skeletal effects during the treatment of Class II malocclusions in adolescents and young adults using a protrusive-acting fixed, rigid functional orthodontic appliance, and to quantify them in comparison with an untreated control group. We aimed to determine whether, and if so, to what extent skeletal effects diminish with increasing age, and whether inter-individual differences can be observed. To correct their intermaxillary jaw relationship, the functional mandibular advancer (FMA) was inserted in 16 adolescents and young adults (eight males, eight females, aged from 12 years, 3 months to 18 years, 7 months) presenting with a skeletal Class II malocclusion. The course of treatment was documented cephalometrically. In all patients, the FMA treatment led to neutroclusion or overcorrected neutroclusion and a marked reduction in overjet. The occlusion's improvement in the sagittal dimension (overjet reduction by 4.43 +/- 2.10 mm, molar relationship improvement by 3.88 +/- 1.12 mm) was achieved by a combination of dental effects (distalization of upper teeth, mesialization of lower teeth) and skeletal effects (mandibular growth stimulation). Excepting the position and morphology of the maxillary base and the condyle's dorsal position in the fossa, all sagittal skeletal and dental changes induced by the FMA treatment were statistically significant. There was a mean increase of 1.71 +/- 1.11 mm in sagittal length of the mandible, in the sagittal-diagonal dimension of 1.42 +/- 1.51 mm and 1.53 +/- 2.15 mm, as well as a slight, significant increase in the gonial angle area. Whereas the condylar position remained stable, a forward positioning of the chin and thus significant increase in distance length was recorded from the posterior condylar margin to the anterior mandibular margin. Treatment with a fixed functional appliance in Class II patients effected significant changes in mandibular growth and correction of the distal intermaxillary relationship even after the pubertal growth spurt in adolescents and young adults. While the proportion of the orthopedically-induced skeletal share is subject to substantial inter-individual variability in adolescents, the overall conclusion can be drawn that skeletal effects (= stimulation of mandibular growth) in general clearly lessen with increasing patient age. In young adult patients, the correction of a distal intermaxillary jaw relationship is manifested primarily as a dento-alveolar compensation for the skeletal malocclusion.

Development of a new fixed functional appliance for treatment of skeletal class II malocclusion first report.

Developed under interdisciplinary cooperation, the Functional Mandibular Advancer (FMA) is a new, rigid and fixed appliance for sagittal correction of the intermaxillary jaw relationship in adolescents and young adults. The appliance is non-dependent on patient compliance and is aimed at providing an alternative to the Herbst and MARA appliances. A number of designs, all based on the mechanical principle of the inclined plane combined with guide pins and allowing reactivation, were developed. The version of the appliance providing the best technical advantages was developed to the stage of practical application in patients.

Longitudinal study of facial growth in relation to skeletal maturation during adolescence

The objective of this research was to compare the 2 treatment protocols including a functional mandibular advancer (FMA; Forestadent, Pforzheim, Germany) followed by multibracket appliances (MBAs) vs a Forsus device (3M Unitek, Monrovia, Calif) in combination with MBA concerning treatment outcomes and posttreatment stability.This study was conducted using lateral cephalograms of patients who were treated with MBA, which was used either after an FMA or concurrently with a Forsus device, and of patients who had untreated Class II malocclusion (control group). Each group consisted of 19 subjects in cervical stage 2 or cervical stage 3 stages according to the cervical vertebral maturation index. Cephalograms were taken for the treated groups at T1 (pretreatment), T2 (completion of the MBA treatment), and T3 (at least 2 years after T2).Significant intergroup differences at the T1-T2 period were observed in favor of the FMA concerning mandibular advancement, intermaxillary relationship, and mandibular elongation. With Forsus treatment, restrained maxillary growth and a slightly improved intermaxillary relationship rebounded after treatment (P <0.05). At the end of treatment, mandibular incisor protrusion and occlusal plane rotation were greater in the Forsus group than in the FMA group (P <0.05), and maxillary incisor retroclination was significant in the Forsus group. During the posttreatment period, although no significant changes were present in the incisors' inclination, relapses of the T1-T2 improvements in overjet and overbite and the recidive of the occlusal plane rotation were significantly higher in the Forsus group.Treatment protocol including an FMA was found to be more effective with mandibular skeletal effects and was more stable with a lesser degree of relapse in overjet and overbite than the Forsus protocol.