Stepwise Mandibular Advancement Research Articles

Stepwise versus single-step mandibular advancement with functional appliance in treating classII patients : Ameta-analysis.

Difference in the functional orthopedic effect between stepwise mandibular advancement (SWA) and single-step mandibular advancement (SSA) in Angle classII patients remains unclarified. To compare the treatment effects of SWA and SSA on skeletal and dentoalveolar changes in classII patients. Randomized controlled trials (RCTs) and nonrandomized studies that compared differences in skeletal and dentoalveolar effects on classII patients between SWA and SSA were identified in PubMed, Embase, CENTRAL, and Web of Science. The grey literature was also searched. The primary outcomes were the mandibular length, L1-MP, and (ANB). Secondary outcomes included Pog sagittal, SNB, overjet, and mandibular plane angle. Seven studies, including three RCTs and four cohort studies, were retrieved. Meta-analyses revealed pooled mean differences (95% confidence interval) of 0.79 mm (0.45 to 1.12 mm) for Pog sagittal, 0.53° (0.19 to 0.87°) for SNB, -0.51° (-0.83 to -0.20°) for ANB, -0.17° (-0.72 to 0.39°) for the mandibular plane angle, -0.41 mm (-0.90 to 0.09 mm) for overjet, -1.87° (-3.23 to -0.52°) for L1-MP, and 1.03 mm (0.63 to 1.42 mm) for the mandibular length. Publication bias was not observed, except for Pog sagittal. The quality of evidence for each outcome was judged as low (mandibular length, SNB and overjet) and very low (Pog sagittal, ANB, L1-MP and mandibular plane angle). Although the magnitude of differences in clinical practice was limited, SWA might be more appropriate because it produces agreater skeletal change and less dental compensation than SSA. As the level of current evidence is low, more high-quality RCTs are needed.

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.

Management of severe Class II malocclusion with sequential modified twin block and fixed orthodontic appliances

Functional appliance is an effective way of treating skeletal Class II malocclusion in children and adolescents. A 12 months stepwise mandibular advancement protocol with Herbst appliance has been proved to enhance condylar growth and improve mandibular prognathism. The present case report documents a 12-year-old boy presenting with Angle’s Class II, division 1 malocclusion associated with excessive overjet (11 mm), 100% deep bite, and retrognathic mandible. He was treated by a phase I growth modification therapy using twin block appliance with lip pads in a stepwise mandibular advancement protocol followed by a phase II preadjusted Edgewise appliance therapy.

Impact of stepwise mandibular advancement on upper airway mechanics in obstructive sleep apnea using phrenic nerve magnetic stimulation

Mandibular advancement devices (MAD) represent a potential treatment for obstructive sleep apnea (OSA). However, their mechanisms of actions are not completely understood. This study was aimed to explore the effects of MAD-induced mandibular protrusion on upper airway mechanics. 25 men commencing treatment for OSA with MAD were recruited. Phrenic nerve magnetic stimulation (PNMS) was used to measure flow/pressure relationship during progressive protrusion in three conditions (without MAD, MAD at minimum protrusion, and MAD at maximum tolerable protrusion). Pressures were recorded simultaneously at three different upper airway segments (naso-, velo-, and oro-pharynx). Without MAD, PNMS twitches induced flow-limitation at the velopharyngeal level in 19 subjects and six of them experienced a shift in the flow-limitation site to the lower segment with MAD at maximum protrusion. An association was found between having a velopharyngeal limitation site without MAD and the increase in maximum flow with the advanced MAD. These data suggest that mandibular advancement devices are acting predominantly at the velopharyngeal level.

Management of Severe Class II Malocclusion With Sequential Fixed Functional and Orthodontic Appliances: A Case for MOrthRCSEd Examination

Fixed functional appliance is an effective way of treating skeletal Class II malocclusion in children and adolescents. The following case report documented a 13-year-old boy with 15 mm overjet treated by a phase I 12-month growth modification therapy using Herbst appliance with Hyrax palatal expander and high pull headgear in a stepwise mandibular advancement protocol followed by a phase II pre-adjusted edgewise appliance therapy. It is one of the cases submitted for the Membership of Orthodontics Examination of the Royal College of Surgeons of Edinburgh.

Condylar growth and mandibular positioning with stepwise vs maximum advancement

The aim of this study was to compare the effects of several Class II malocclusion treatments on condylar growth and positioning of the mandible. The material comprised series of lateral cephalograms obtained at the start, after about 6 months, and after about 12 months of treatment from 3 groups of consecutively treated patients who used a headgear-activator with stepwise mandibular advancement (HGA-S), a headgear-activator with maximum jumping of the mandible (HGA-M), and a headgear-Herbst appliance with stepwise advancement (HGH-S), respectively. Six-month growth data from matched controls were used to calculate the net treatment effects. Mandibular prognathism was enhanced after stepwise advancement but not after maximum jumping, and only during the initial phase of therapy; the effect was significantly greater for the fixed functional appliance than for the removable functional appliance. Lower-facial height was increased by the HGA-S, unchanged by the HGA-M, and restrained by the HGH-S. The low construction bite of the HGH-S meant that the extent of bone apposition on the posterior and superior parts of the condyle was similar, whereas the high construction bite of the HGA-S and the HGA-M meant that the effect on the superior part was greater, but only significantly so after stepwise advancement. The mode of jumping, the vertical opening, and whether the functional appliance is fixed or removable affect the amount and pattern of condylar growth, and the position of the mandible.

Stepwise advancement versus maximum jumping with headgear activator

The aim of this study was to compare the effects of stepwise mandibular advancement versus maximum jumping and extended treatment versus early retention. The material was obtained prospectively and consisted of lateral cephalograms taken at the start (T0), after initial (T1), and at the end (T2) of treatment, from two groups of consecutively treated skeletal Class II patients who had undergone therapy with headgear activators. The first headgear activator group, HGA-S (n=24; mean age 11.9 +/- 1.2 years), was treated for 13 months and had 4-mm mandibular advancement every 3 months. The second headgear activator group, HGA-M (n=31; mean age 11.2 +/- 1.5 years), had maximum jumping, 6-8 mm interincisal opening, for a total of 15.4 months, and with reduced wear for the last 6.9 months. The dropout over 12 months was 41 and 46 per cent, respectively. Pre-treatment growth changes were obtained as a reference. An independent t-test was used to determine differences in baseline dentofacial morphology between the groups, a paired t-test for intra-group comparisons, and an independent t-test to evaluate differences between the groups. The results, in both groups, showed enhanced mandibular prognathism during the initial phase (T0-T1), followed by normal growth (T1-T2), and lower face height enhancement throughout treatment (T0-T2). For both groups, the mandibular plane and occlusal angle increased, possibly enhanced by 'extrusion' of the lower molars. For both groups, maxillary forward growth was restrained only during the initial phase, but the effect remained significant at T2 for the HGA-S group. In the HGA-M group, the lower incisors were protruded, while in the HGA-S group, they were unaffected. The findings indicate that both modes of mandibular jumping resulted in skeletal and dental effects. The length of active treatment seemed to be decisive in maintaining the treatment effects; stepwise advancement had less dental effects.

Neovascularization and bone formation in the condyle during stepwise mandibular advancement.

The aims of this investigation were to identify the temporal expression of vascular endothelial growth factor (VEGF) in the mandibular condyle and to correlate it with the pattern of new bone formation during stepwise mandibular advancement. Two hundred and fifty female, 35-day-old Sprague-Dawley rats were randomly divided into 10 groups, with 10 rats allocated to the single-step bite-jumping subgroup, 10 rats to the stepwise advancement subgroup and five rats to the control subgroup. In the experimental groups, the mandibles were kept in a continuous forward position. The initial stepwise advancement commenced on day 35, whereas the second advancement started on day 65. The rats were sacrificed on experimental days 3, 7, 14, 21, 30, 33, 37, 44, 51 and 60. Sections (7 microm) were cut through the condyle in the parasagittal plane and stained with anti-VEGF antibody. Each section was counter-stained with haematoxylin for observation of the cellular response. The sections were digitized and quantitatively analysed with a computer-assisted image analysing system. The results showed that the initial advancement in the stepwise group led to significantly less expression of VEGF when compared with single advancement. However, the second advancement on day 30 resulted in a significant increase in VEGF expression when compared with the one-step group and the natural growth control group. Thus, it was concluded that changes in the amplitude of mechanical loading, produced by stepwise advancement, have a significant effect on the production of VEGF by the chondrocytes. During the later stages of advancement, more VEGF and more condylar bone was produced.

Vascular endothelial growth factor expression and bone formation in posterior glenoid fossa during stepwise mandibular advancement

This study assessed the amount of vascular endothelial growth factor (VEGF) expression and related the findings to new bone formation in the posterior glenoid fossa during stepwise mandibular advancement. A total of 250 female Sprague-Dawley rats, 35 days old, were randomly divided into 10 groups, each including 5 control and 20 experimental rats. Within each group, 10 experimental rats were fitted with functional appliances with a 1-step advancement of 3.5 mm. Another 10 were fitted with stepwise appliances with an initial advancement of 2 mm and a subsequent increase to 3.5 mm on day 30. The rats in the experimental groups were killed on days 3, 7, 14, 21, 30, 33, 37, 44, 51, and 60, respectively. The matched controls were killed on the same time points. Sections (7 μm) were cut through the glenoid fossa sagittally and stained with anti-VEGF antibody. VEGF expression in the posterior glenoid fossa was evaluated with a computer-assisted image-analyzing system. Both VEGF expression and new bone formation were greater in the experimental rats than in the controls. During stepwise advancement, initial VEGF expression was less than that of 1-step advancement, but the second advancement elicited another peak on day 44. New bone formation was also less than that of 1-step advancement during early stages of stepwise advancement but then began to increase from day 37 onward. The maximum increase was observed on day 60. Stepwise advancement of the mandible delivers mechanical stimuli that produce a series of tissue responses that lead to increased vascularization and bone formation.

Stepwise advancement using fixed functional appliances: Experimental perspective

This study was designed to identify the pattern of bone formation in thetemporomandibular joint in response to the stepwise mandibular advancement compared to single step advancement with fixed functional appliances. Two hundred fifty 35-day-old female Sprague-Dawley rats were randomly divided into 20 experimental and 10 control groups. Appliances were fitted to position the mandible forward in the experimental groups. Veneers were added to achieve movement. The rats were then sacrificed at different time points. Sections were cut and stained with periodic acid and Schiff's reagent for evaluation of new bone formation. Newly formed bone was measured by a computer-assisted image analyzing system. The results showed that, during the first advancement, bone formation in the condyle and glenoid fossa was less than that of 1-step advancement. In response to the second advancement, new bone formation was significantly higher when compared with single advancement with a maximum increase of 50% and 100% in the condyle and glenoid fossa, respectively. In conclusion, the stepwise advancement produces more skeletal effects than single advancement and a more prominent effect with stepwise advancement was found in the glenoid fossa compared with the condyle.