[Effect of Twin-block in adolescents with mandibular retrusion and normal anterior overjet].

PURPOSE: To investigate the therapeutic effect of modified fixed Twin-block on patients whose mandible was retruded and anterior overjet was normal. METHODS: Thirty-six adolescents with mandibular retrusion and normal anterior overjet were selected. The goal of occlusal reconstruction was to move the soft tissue pogonion forward to the zero meridian(0°). Fixed Twin-block combined with the mini-implants on the mandibular buccal shelf was used to promote mandibular growth. After 12 months, the appliances were removed step by step to observe the stability of the jaw relationship. Fixed orthodontic treatment was performed to achieve ideal occlusion and coordinated profile. SPSS 13.0 software package was used for Student's t test. RESULTS: The length of mandibular body increased significantly which facilitated the forward movement of the soft tissue pogonion, and the profile changed from convex to straight. Comparison of the results before and after Twin-block treatment showed that Co-Gn, SNB, U1-SN, U6-0°, U1-0°, U1-L1, anterior overbite, anterior overjet, Pog's-0°, L1-0° and lower anterior facial height changed significantly (P＜0.05). Comparison of the results before and after fixed orthodontic treatment showed that PP-MP, SN-MP, U6-0°, IMPA, L1-0°,U1-SN, U1-L1, anterior overbite and overjet changed significantly(P＜0.05). CONCLUSIONS: Modified fixed Twin-block combined with mini-implants on the mandibular buccal shelf can effectively stimulate the mandibular growth and improve the lateral profile of patients with mandibular retrusion and normal overjet.

Efficacy of a modified twin block appliance compared with the traditional twin block appliance in children with hyperdivergent mandibular retrognathia: protocol for a single-centre, single-blind, randomised controlled trial.

INTRODUCTION: Compensatory mouth breathing, caused by nasopharyngeal obstructive diseases, is the main cause of hyperdivergent mandibular retrognathia in children. Such deformities require effective growth guidance before pubertal growth peaks. The traditional mandibular advancement device, twin block (TB), can guide the forward development of the mandible. However, the side effect of increasing the vertical dimension of the lower facial third, worsens the facial profile of children with divergent growth trends. To solve this problem, a modified TB (LLTB) appliance was designed to control the vertical dimension by intruding incisors and inhibiting the elongation of posterior teeth during the advancement of the mandible, which could avoid the side effects of traditional appliances and effectively guide the growth of the mandible in a normal direction. METHODS AND ANALYSIS: The study was designed as a single-centre, single-blind, randomised, parallel controlled trial. We aim to enrol 60 children aged 9-14 years with hyperdivergent skeletal class II malocclusion, using a 1:1 allocation ratio. The participants were will be randomly assigned to receive either the TB or LLTB treatment. The primary outcome will be a change in the angle of the mandibular plane relative to the anterior cranial base. The secondary outcomes will include changes in the sagittal maxillomandibular relation, occlusal plane, facial height, morphology of the mandible and upper airway width. Safety endpoints will also be evaluated. ETHICS AND DISSEMINATION: Ethical approval was obtained from the ethics committee of Shanghai Stomatological Hospital. Both participants and their guardians will be fully informed of the study and sign an informed consent form before participating in the trial. The results will be publicly available in peer-reviewed scientific journals. TRIAL REGISTRATION NUMBER: ChiCTR2000035882.

Stress distribution of the modified clear twin-block aligner on the temporomandibular joint, alveolar bone and teeth: A finite element analysis.

OBJECTIVE: The modified clear twin-block aligner (CTBA) was developed to provide a mandibular advancement appliance for the treatment of mandibular retrognathia. The objective of this study was to analyse the stress distribution changes of CTBA with 45°, 60° and 70° bite blocks. MATERIAL AND METHODS: A three-dimensional model of the craniomaxillofacial bones and teeth was generated from a spiral computed tomography (CT) scan. The models of the articular disc, capsule, periodontal ligament and CTBA were constructed mathematically. After assigning the appropriate material properties and the boundary condition using ABAQUS software, we simulated the CTBA with different bite blocks to analyse the mechanical effects. RESULTS: In the temporomandibular joint (TMJ) region, the posterior aspect of the condyle and glenoid fossa experienced tensile stress that was approximately about 22 times greater at 70° than at 45°. The Von Mises stress distribution on the articular disc tended to be uniform. The strain direction of the condyle was backward. In the maxillary bone, the stress on the labial alveolar bone was about 5.83MPa at 70° and greater than that on the lingual side. The resulting displacement of the dentition revealed a tendency for the upper teeth to shift backward and the lower teeth to move forward by 0.46 to 0.49mm. The foregoing stress and displacement rose as the angle of the bite blocks increased. CONCLUSIONS: CTBA with 70° bite blocks constituted an advantageous biomechanical setting for the treatment of mandibular retrognathia in teenagers and provided a superior therapeutic effect.

Effects of twin-block appliance on upper airway parameters in OSA children with class II malocclusion and mandibular retrognathia: a CBCT study.

Twin-block appliance had been advocated as a potential treatment option in paediatric obstructive sleep apnoea (OSA) due to their favourable effect in enhancing upper airway parameters and improving OSA symptoms. The aim of this study was to evaluate the effect of twin-block appliance therapy on upper airway parameters/dimensions and the apnoea-hypopnea indexes (AHIs) in OSA children with class II mandibular retrognathic skeletal malocclusion using cone-beam computed tomography. This prospective longitudinal study comprised 34 polysomnography-proven OSA growing children with class II mandibular retrognathic skeletal malocclusion between the ages of 8 and 12 years who had completed myofunctional twin-block therapy and matched corresponding controls. The upper airway was segmented into the nasopharynx, oropharynx, and hypopharynx, and the effect of twin-bock treatment on upper airway parameters/dimensions was assessed pre- and posttreatment using CBCT analysis, while a second standard overnight PSG was performed to determine changes in the AHI. At the nasopharynx level, minimal (nonsignificant) increases in all variables were observed within the twin-block group and between the groups (P > 0.05). At the level of the oropharynx, all variables increased significantly in the treatment group and between groups (P < 0.001), but these increases were nonsignificant in the control group. At the level of the hypopharynx, only the minimum cross-sectional area (MCA) increased significantly in the treatment group (P = 0.003). The change in MCA was also significant between the groups (P = 0.041). In addition, the upper airway length increased significantly in the twin-block group (P = 0.0154), and the AHI decreased by 74.8% (P < 0.001). CONCLUSION: Correction of class II mandibular retrognathic skeletal malocclusion with twin-block appliance resulted in a significant increase in upper airway volume, MCA, anteroposterior and lateral distances of the MCA at the level of the oropharynx, MCA at the level of the hypopharynx and upper airway length, and a significant decrease in AHI, but it had no effect on nasopharynx parameters. WHAT IS KNOWN: • CBCT imaging has been shown to be an effective and precise diagnostic tool for analyzing the upper airways and craniofacial structures. • Twin block appliance may be an effective treatment modality in children with OSA. WHAT IS NEW: • Minimal cross-sectional area of upper ways may be the most relevant potential parameter when explaining how the upper airway anatomy plays role of in the pathogenesis of pediatric OSA. • Twin block appliance induced favorable changes in upper airway morphology (oropharynx area mainly) and respiratory parameters in OSA children with class II malocclusion.

Thirteen-year-old female patient with class II division 2 and normodivergent mandibular retrognathia treated with a fixed buccal appliance. Clinical case No. 221052, Commission of Titularisation. European College of Orthodontics.

Date of birth>09/06/2004; sex: female. Pre-treatment documents>13years 4months old: 07/07/2017. Diagnosis>Skeletal class II with mandibular retrusion, normodivergent facial pattern; class II division 2. Treatment planning>bimaxillary buccal fixed appliance. Duration of active treatment>29months. Post-treatment documents>15years 6months; 20/12/2019. Post-retention documents>16years 7months old; 04/01/2021. Retention period>2years 9months and still continued.

Treatment effects of the MARA appliance and Activator-Headgear combined with fixed appliances in Class II division 1 malocclusion patients: A retrospective longitudinal study.

INTRODUCTION: Class II division 1 malocclusion treatment with functional devices offers acceptable results. These devices can be removable or fixed, and the essential difference between them is the need for compliance. It is clinically important to investigate if there are differences in the treatment effects of these devices that present different characteristics. OBJECTIVE: This retrospective longitudinal study compared the treatment effects of Class II correction with the MARA appliance, Activator-Headgear (AcHg) combination, both followed by multibracket fixed appliances, and an untreated control group. MATERIAL AND METHODS: Each experimental group was composed of 18 patients, with a baseline mean age of 11.70 and 10.88 years, treated for 3.60 and 3.17 years. The control group consisted of 20 subjects with baseline mean age of 11.07 years. The groups were evaluated before (T1) and after (T2) treatment. Lateral radiographs were used to evaluate the treatment changes with treatment (T2-T1), compared to the control group. Intergroup comparisons were performed using repeated-measures analysis of variance (ANOVA), followed by Tukey's test. RESULTS: The AcHg group showed significantly greater maxillary growth restriction than the MARA, while the mandibular changes were due to natural growth. Both devices promoted significantly greater maxillary incisors retrusion, mandibular incisors labial inclination, and improvement of overjet and molar relationships, compared to the control. CONCLUSIONS: Both functional devices followed by multibracket appliances were effective to correct Class II malocclusion. Nonetheless, the AcHg combination presents superior skeletal effects, due to significantly greater maxillary growth restriction compared to the MARA appliance. Moreover, the appliances presented similar dentoalveolar effects.

Three-dimensional evaluation of the effects of Bionator and Forsus appliances on oropharyngeal airway volume in patients with mandibular retrognathia.

OBJECTIVE: To evaluate whether there is a difference between the effects of Bionator and Forsus appliances on airway volume. METHODS: Forty patients with mandibular retrognathia were divided into two groups. The Bionator appliance was applied to Group 1, while the Forsus FRD EZ2 appliance was applied to Group 2. Three-dimensional images were captured before and after functional appliance use in both groups. Dolphin 3D software was used for airway measurements. RESULTS: No statistically significant difference was found between the groups in terms of volumetric and area measurements. There was a statistically significant difference between the minimum axial T and O-N border T measurements of the groups. CONCLUSION: The use of functional appliances may contribute to an increase in oropharyngeal airway dimensions, but there was no difference between the Bionator and Forsus groups in terms of volumetric measurements.

[Changes in tongue position and three-dimensional changes in upper airway before and after treatment with Twin-block combined with maxillary expansion appliance in children with mandibular retrusion].

PURPOSE: To observe changes of upper airway in three dimensions and tongue position after correction with Twin-block combined with maxillary expansion appliance in children with mandibular retrusion and history of mouth breathing. METHODS: Twenty children with Class Ⅱ malocclusion and mandibular retrusion were selected and treated with Twin-block combined with maxillary expansion appliance. Cone-beam CT(CBCT) data before and after treatment were imported into Mimics 21.0 software to measure the total volume of the upper airway (nasopharyngeal segment + oropharyngeal segment), as well as segmental airway volume of nasopharyngeal, glossopharynx and oropharyngeal space. The cross-sectional area and maximum sagittal diameter at the tip of uvula in glossopharyngeal airway,and maxillary width were measured, too. Anterior-posterior and height changes of tongue position were observed. SPSS 26.0 software package was used to perform paired sample t test and Wilcoxon signed rank test of the data. RESULTS: The total upper airway volume and the airway volume of the nasopharyngeal, oropharyngeal and glossopharyngeal segments increased significantly after correction. The cross-sectional area and maximum sagittal diameter at the tip of uvula in glossopharyngeal segment, and the maxillary width were increased significantly.Tongue position increased and moved forward. All the above data had significant different(P＜0.05). CONCLUSIONS: Twin-block combined with maxillary expansion appliance can increase the total volume of the nasopharyngeal segment, oropharyngeal segment, glossopharyngeal segment and upper airway in children with Class Ⅱ malocclusion and mandibular retrusion and expand the anterior-posterior depth of oropharynx airway.In addition,the treatment can increase maxillary width and normalize the tongue position, and contribute to the improvement of airway patency.

Effects of the advanced mandibular spring on mandibular retrognathia treatment: a three-dimensional finite element study.

BACKGROUND: The Advanced Mandibular Spring (AMS) was newly developed as a dentofacial orthopedic appliance in conjunctive use of clear aligners to treat Class II malocclusion with mandibular retrognathia in adolescents. This study aimed to launch a biomechanical assessment and evaluate whether the stress patterns generated by AMS promote mandibular growth. METHODS: A three-dimensional finite element model was constructed using images of CBCT and spiral CT. The model consisted of craniomaxillofacial bones, articular discs, retrodiscal elastic stratum, masticatory muscle, teeth, periodontal ligament, aligner and AMS. Mechanical effects were analyzed in three types of models: mandibular postural position, mandibular advancement with AMS, and mandibular advancement with only muscular force. RESULTS: The stress generated by AMS was distributed to all teeth and periodontal ligament, pushing mandibular teeth forward and maxillary teeth backward. In the temporomandibular joint area, the pressure in the superior and posterior aspects of the condyle was reduced, which conformed to the stress pattern promoting condylar and mandibular growth. Stress distribution became even in the anterior aspect of the condyle and the articular disc. Significant tensile stress was generated in the posterior aspect of the glenoid fossa, which conformed to the stress pattern stimulating the remodeling of the fossa. CONCLUSIONS: AMS created a favorable biomechanical environment for treating mandibular retrognathia in adolescents.

Craniofacial changes from 13 to 62 years of age.

BACKGROUND: In long-term studies of orthodontic, orthognathic, and prosthodontic treatments, control subjects are needed for comparison. OBJECTIVES: To study the craniofacial (skeletal, soft tissue, and dental) changes that occur in untreated subjects with normal occlusion between 13 and 62 years of age. MATERIALS/METHODS: Thirty subjects with a Class I normal occlusion and harmonious facial profile were studied. X-ray examinations were performed at 13 (T1), 16 (T2), 31 (T3), and 62 (T4) years of age, and data were obtained from cephalograms. In total, 53 angular and linear parameters were measured using superimposition-based and conventional cephalometric methods to describe the craniofacial changes. RESULTS: The jaws showed significant anterior growth from T1 to T2, and significant retrognathism from T3 to T4. The anterior face height and jaw dimensions increased significantly until T3. Significant posterior rotation of the mandible and opening of the vertical jaw relation, in addition to significant retroclination of the incisors and straightening of the facial profile, were found from T3 to T4. LIMITATIONS: Given the small sample size at T4, it was not possible to analyse the gender dimension. CONCLUSIONS/IMPLICATIONS: Craniofacial changes continue up to the sixth decade of life. These changes are consistent, albeit to a lesser extent, with the adolescent growth patterns for most of the studied parameters, with the exceptions of incisor inclination, sagittal jaw position, vertical jaw relation and inclination, and posterior face height.

Effectiveness of Continuous Positive Airway Pressure Versus Mandibular Advancement Device in Severe Obstructive Sleep Apnea Patients With Mandibular Retrognathia: A Prospective Clinical Trial.

AIM: Some obstructive sleep apnea (OSA) patients may have mandibular retrognathia (ANB > 4.7° and SNB < 76.2°). Currently, there are no studies that have compared the effectiveness of continuous positive airway pressure (CPAP) versus mandibular advancement device (MAD) in severe OSA patients with mandibular retrognathia. We explored the efficacy of CPAP versus MAD for the treatment of severe OSA patients with mandibular retrognathia. METHODS: A total of 105 patients were enrolled. Outcomes were assessed by using polysomnography, Epworth Sleepiness Scale (ESS), Snore Scale (SS), Self-rating Anxiety Scale (SAS), and compliance, before treatment and after 6 and 12 months of treatment. RESULTS: Continuous positive airway pressure was superior to MAD in improving polysomnographic outcomes and SS score, but reported compliance was higher on MAD. There is no significant difference between the 2 treatments in terms of ESS score and SAS score. Obstructive sleep apnea patients with mandibular retrognathia showed greater improvement than those without mandibular retrognathia in terms of apnea-hypopnea index and oxygen desaturation index after MAD. CONCLUSION: Continuous positive airway pressure and MAD are both effective in treating severe OSA patients with mandibular retrognathia. Mandibular advancement device is a good alternative to CPAP in severe OSA patients with mandibular retrognathia. Mandibular advancement device is more effective in treating OSA patients with mandibular retrognathia than those without. Trial registration: ChiCTR2000032541.

Diagnóstico e tratamento precoce da má oclusão de Classe III com Aparelho Disjuntor Hyrax e Máscara Facial de Petit com avaliação do tempo de uso com micro-sensor: relato de caso clínico / Early diagnosis and treatment of Class III occlusion with Hyrax Isolating Appliance and Petit Face Mask with evaluation of the time of use with micro-sensor: a clinical case report

O sucesso do tratamento precoce da classe III depende de um bom diagnóstico e da cooperação do paciente na utilização do aparelho extrabucal. Neste trabalho, por meio de um chip (Theramon) instalado na Máscara Facial de Petit da paciente, foi possível monitorar a quantidade de horas que a paciente utilizou o aparelho por dia, durante um período de quatro meses. Paciente do sexo feminino, 7 anos e 11 meses de idade portadora da má oclusão de classe III, utilizou o aparelho de disjunção da maxila (Hyrax) modificado, seguido da Máscara Facial de Petit com chip (Theramon) instalado. A média de uso foi maior do que 11 horas de uso diário. O uso deste dispositivo auxilia no monitoramento do tempo de uso do aparelho, cujo sucesso do tratamento depende da utilização deste pelo paciente(AU)

The success of early treatment of class III depends on a good diagnosis and the cooperation of the patient in the use of the extra oral appliance. In this study, the patient was able to monitor the number of hours the patient used the device per day during a period of four months using a Theramon chip installed in the Patient's Facial Mask. A 7-year, 11-month-old male with Class III malocclusion used the modified maxillary disjunction (Hyrax), followed by the Petit Facial Mask with a Theramon chip installed. The average use was greater than 11 hours of daily use. The use of this device assists in the monitoring of the time of use of the device, whose success of the treatment depends on the use of this by the patient(AU)

Long-term maxillary anteroposterior changes following maxillary protraction with or without expansion: A meta-analysis and meta-regression.

BACKGROUND: Maxillary protraction with or without expansion is a widely known orthopedic treatment modality in growing skeletal Class III patients. However, limited data are available regarding the outcomes of long-term changes in the maxilla. Aim of this meta-analysis was to assess the effectiveness of the long-term maxillary anteroposterior changes following a facemask therapy with or without rapid maxillary expansion in growing skeletal Class III patients. METHODS: A comprehensive literature search was conducted using the databases of PubMed, Science Direct, Web of Science, and Embase. Randomized controlled trials and cohort studies, published up to Sep. 2020, with maxillary protraction and/or expansion as keywords were included in this meta-analysis. Risk of bias within and across studies were assessed using the Cochrane tools (RoB2.0 and ROBINS-I) and GRADE approach. Overall and subgroup comparisons with the random-effect model were performed in this meta-analysis. Meta-regression models were designed to determine potential heterogeneity. RESULTS: There was a statistically significant increase (Mean difference, 2.29°; 95% confidence interval, 1.86-2.73; and p < 0.001 after facemask (FM) protraction. Mean difference, 1.73°; 95% confidence interval, 1.36-2.11; and p < 0.001 after rapid maxillary expansion(RME) and facemask protraction) in the Sella-Nasion-A point (SNA) angle in the treatment groups as compared with the control groups, when measured during the less than 3-year follow-up period. However, no statistically significant changes (Mean difference, 0.28°; 95% confidence interval, -0.57-1.13; and p = 0.52 after facemask protraction. Mean difference, 0.34°; 95% confidence interval, -0.64-1.33; and p = 0.50 after rapid maxillary expansion and facemask protraction) were observed in the SNA angle in the groups, when measured after 3 years of follow-up. Meta-regression analysis also showed that with increased follow-up duration, the effectiveness of maxillary protraction decreased. CONCLUSION: This meta-analysis revealed that maxillary protraction therapy could be effective for a short-term in correcting maxillary hypoplasia and the treatment result was not affected by mean age and sex. However, with increased follow-up duration, the sagittal maxillary changes gradually decreased. Limitations on this review were only the SNA angle was used and clinical heterogeneity was not discussed. The quality of evidence was moderate. Further long-term observational studies are necessary for a comprehensive evaluation of the effects on maxillary skeletal changes.

A Prospective Study Comparing Adolescent and Post-Adolescent Periods Regarding Effects of Activator Appliance in Patients with Class II Mandibular Retrognathia by Using 3dMDface Analysis and Cephalometry.

BACKGROUND The purpose of this prospective study was to compare adolescent and post-adolescent growth periods regarding the effectiveness of conventional activator appliance in patients with Class II mandibular retrognathia by using lateral cephalometric radiographs and three-dimensional photogrammetry (3dMDface). MATERIAL AND METHODS We enrolled 2 groups: 15 patients in the adolescent growth period and 17 patients in the post-adolescent growth period. All patients had Class II anomaly with mandibular retrognathia and were treated with conventional activator appliances. Lateral cephalometric radiographs and three-dimensional photogrammetric views were obtained at the beginning and end of the activator treatment of Class II patients. Maxillomandibular discrepancy, mandibular protrusion and lengths, convexity angles, facial heights, and dental measurements were evaluated cephalometrically. Projections of the lips and the chin and volumetric measurements of the lip and the mandibular area were assessed using three-dimensional photogrammetry. RESULTS Conventional activator therapy resulted in similar effects in both growth periods regarding improvements in the mandibular sagittal growth and maxillomandibular relationship (ANB° and the SNB° angles). Mandibular effective length was increased (Co-Gn length) and the maxillary horizontal growth was restricted (decreased SNA° angle) in both groups following the treatment. Treatment duration was significantly longer in the post-adolescent group. Increases in the projections of menton, pogonion, and sublabial points were observed in the three-dimensional photogrammetric views. Total lip volume was reduced while the mandibular volume was significantly increased in both groups. Lower gonial angle showed a greater increase in the post-adolescent group. CONCLUSIONS Correction of Class II anomaly with mandibular retrognathia was achieved with a combination of dental and skeletal changes in both growth periods. Conventional activator therapy may be an alternative treatment approach in the late growth period as it led to significant skeletal and dental changes.

¿Es inocua la ortopedia dentofacial? / Is dentofacial orthopedics harmless?

El enfisema subcutáneo es el proceso por el cual el aire penetra en el espacio subcutáneo, produciendo distensión de las partes blandas. Puede ser de origen traumático, iatrogénico o producirse de forma espontánea. Es infrecuente su aparición tras procedimientos dentales y no ha sido descrito asociado a la ortopedia dentofacial. Presentamos el caso de una paciente con enfisema subcutáneo tras un traumatismo por un aparato de avance mandibular tipo Herbst

Subcutaneous emphysema is the condition in which air penetrate the subcutaneous space causing soft-tissue distention. It may be traumatic, iatrogenic or may occur spontaneously. Its appearance is rare after dental procedures and has not been reported associated to dentofacial orthopedics. We report the case of a patient who developed subcutaneous emphysema after a trauma from a Herbst-type mandibular advancement appliance

Changes in the position of the condyle after bilateral sagittal split ramus osteotomy in patients with mandibular retrusion and protrusion: a new condyle: fossa matching concept.

The purpose of this study was to compare the condylar positional changes after bilateral sagittal split ramus osteotomy (BSSRO) in patients with mandibular retrusion and those with mandibular prognathism. We also studied the correlation between the degree of matching of the condyle and fossa, and condylar displacement. Thirty patients with mandibular retrusion (n=11) or mandibular prognathism (n=19) who underwent BSSRO were included. The condylar position was assessed from spiral computed tomographic (CT) scans taken preoperatively, during the first postoperative week, and at least 6 months postoperatively. All data were measured by MIMICS 17.0 and analyzed by Student's t test and Pearson's correlation analysis. The size of the condyles of patients with mandibular retrusion was significantly less than those of patients with mandibular prognathism (491.5 (172.8) compared with 823.2 (212.0) mm3). The size of the glenoid fossa in those with mandibular retrusion (599.6 (110.4) mm3) and those with prognathism (597.6 (151.6) mm3) did not seem to differ. Postoperatively the condyles moved outwards, backwards, and downwards in both groups of patients. Correlation analysis between the condyle:fossa volume ratio and the condylar positional changes showed that a large condyle:fossa volume ratio correlated with the smaller positional changes in the condyle. The condylar position changed immediately after mandibular advancement and setback, and persisted in the long term. Larger condyles tended to have fewer positional changes.

[Upper airway changes in patients with skeletal Class â ¢ maxillary retrognathia after rapid maxillary expansion and protraction: a meta-analysis].

PURPOSE: This study was to evaluate the upper airway changes in patients with skeletal Class Ⅲ maxillary retrognathia after rapid maxillary expansion and protraction. METHODS: An electronic search in PubMed, Cochrane Library, Embase, CNKI, CBM, VIP and Wanfang was performed until March 1st, 2018. According to the inclusion and exclusion criteria, two investigators respectively reviewed the literature and selected eligible studies, then assessed the risks of bias and extracted the data of the included studies. The extracted data were quantitatively analyzed with Revman 5.3 software. RESULTS: A total of 12 studies were included for meta-analysis. The results showed that, after treatment the nasopharyngeal volum(P<0.05) increased significantly. However, no statistically significant differences in oropharyngeal volume(P>0.05) and hypopharyneal volume (P>0.05) existed. The nasopharyngeal airway dimensions had increased significantly with the following measurements: PNS-ad1 (P<0.05), PNS-ad2(P<0.05). However, no statistically significant differences in lower pharynx dimension existed with the following measurements: MPS(P>0.05), IPS(P>0.05). CONCLUSIONS: Rapid maxillary expansion and protraction can increase nasopharyngeal volume and sagittal airway dimensions in skeletal Class Ⅲ subjects with maxillary retrusion. It may be suggested that rapid maxillary expansion and protraction have the potential to reduce the risk of obstructive sleep apnea syndrome in children with maxillary retrusion by enlarging airway space.

Treatment effects of two different appliances on pharyngeal airway space in mixed dentition Malay children.

BACKGROUND: Treatment of Class III malocclusion is related to redirecting the growth of mandible, which may have an impact on the pharyngeal airway. OBJECTIVE: To evaluate and compare the treatment effect of Reverse Twin-Block (RTB) and Reverse Pull Face Mask (RPFM) on Pharyngeal Airway Space (PAS) in early and late mixed dentition Class III samples. METHODS: Ninety-five mixed dentition Malay children with Class III malocclusion were included in this study. Data consists of 190 pre- and post-treatment lateral cephalograms of early (8-9 years) and late (10-11 years) mixed dentition Class III samples. forty-nine samples were under RTB and forty-six samples were under RPFM. Treatment changes were evaluated by McNamara airway analysis and changes in tongue and hyoid bone position. RESULTS: Both upper and lower pharyngeal airway width were increased after treatment with RTB and RPFM ruling out the chance of airway constriction. There was also posterior positioning of the tongue and hyoid bone indicating mandibular retrusion. No significant treatment changes were found on the Pharyngeal Airway Space by the factor age, gender or type of appliance. CONCLUSIONS: Both RTB and RPFM increased the Pharyngeal Airway Space and produced similar treatment effect. As age does not affect the treatment outcome significantly, treatment can be delayed until late mixed dentition stage.

Evaluation of changes in the upper airway after Twin Block treatment in patients with Class II malocclusion.

The purpose of this prospective case control study is to describe in growing patients with mandibular hypoplasia, treatment outcomes following functional therapy in terms of volumetric changes in nasopharynx and oropharynx, that is, upper and lower pharynx. We recruited 60 study participants aged between 8 and 12 years having mandibular Class II malocclusion and a reduced upper airway (UA) size, as determined by McNamara cephalometric analyses. Forty patients received Twin Block treatment, whereas the remaining 20 patients did not receive treatment, thus constituting the control group. The control group included patients who did not start treatment after their first visit but returned for a consultation one or 2 years later. All patients underwent an initial teleradiography examination of the skull and a final teleradiography examination to measure changes using McNamara cephalometric analysis of the UA. Pretreatment and posttreatment changes were assessed using Student's t test for independent samples with a significance level of 0.05. Both anatomical structures analyzed-the upper pharynx (nasopharynx) and lower pharynx (oropharynx)-showed significant increases after treatment regardless of whether the patients were boys or girls. The controls showed a decrease in UA size on average after approximately 2 years of growth. A clear relationship exists between the mandibular advancement achieved with TB treatment and an increased UA size. Therefore, the appliance is considered suitable for improving the respiratory quality of growing patients with a decreased UA size.