Occlusal plane canting reduction accompanies mandibular counterclockwise rotation in camouflaging treatment of hyperdivergent skeletal Class II malocclusion

ObjectiveTo investigate the occlusal configurations of the hyperdivergent skeletal Class II malocclusion and their alterations during the camouflaging treatment in an attempt to identify occlusal changes that might be related to mandibular counterclockwise rotation.Materials and MethodsCephalograms of 126 subjects with hyperdivergent skeletal Class II malocclusion and 126 subjects with a clinically normal skeletal pattern were chosen. Several measurements were calculated and compared between the groups. To examine the effects of treatment, two groups were established according to mandibular rotation: counterclockwise rotation (CCR) and the opposite clockwise rotation (CR). After 40 subjects were excluded, the other 86 Class II subjects were assigned to CCR (n  =  22) and CR (n  =  64). Their pretreatment (T1), posttreatment (T2), and postretention (T3) cephalograms were obtained. Measurement changes (T3-T1) were analyzed in each group and compared between groups.ResultsCompared with the normal skeletal pattern, the cant of the occlusal plane (OP) of the study subjects was significantly steeper and the vertical heights of the incisors were significantly larger for the malocclusion. Compared with the changes in CR, there was a prominent reduction of the OP canting with remarkable intrusion of the maxillary incisor in CCR.ConclusionIncreased OP canting with overerupted incisors is evident in the hyperdivergent skeletal Class II malocclusion. During the camouflaging treatment, reduction of OP canting could occur. It was accompanied by mandibular counterclockwise rotation and intrusion of the maxillary incisor.     

Three-dimensional alterations in pharyngeal airspace,soft palate,and hyoid bone of class II and class III patients submitted to bimaxillary orthognathic surgery: A retrospective study

IntroductionThe aim of this retrospective study was to evaluate changes in pharyngeal airway space (PAS), soft palate, and hyoid bone position after bimaxillary orthognathic surgery in skeletal Class II and Class III patients.MethodsPatients were divided into Group 1: Class III patients who underwent maxillary osteotomies and mandibular setback surgery (N = 43); and Group 2: Class II patients who underwent maxillomandibular advancement surgery (N = 36). Cone beam computed tomography (CBCT) images were acquired one month before and six to eight months after orthognathic surgery. PAS area, volume and minimum axial area (MAA), soft-palate morphology, and hyoid bone position measurements obtained before and after orthognathic surgery were compared using the Gamma family test (p ≤ 0.10).ResultsIn Class II group the maxillomandibular advancement surgery significantly increased the PAS area, volume, and MAA and significantly affected hyoid bone position and soft-palate morphology. In Class III group, maxillary osteotomies and mandibular setback also showed increase in PAS area, however without statistically significant values for most of the evaluated measurements.ConclusionThe results of the present study indicate that PAS and related structures are expected to be improved in Class II patients submitted to bimaxillary surgery, and they are not negatively affected by bimaxillary surgery in Class III patients.     

Changes in posterior airway space and hyoid bone position after surgical mandibular advancement

Objective: To evaluate cephalometric changes in posterior airway space (PAS) and in hyoid bone distance to mandibular plane (MP) 1–3 years after bilateral sagittal split osteotomy (BSSO).

Material and methods: The sample consisted of 36 females and 16 males who underwent mandibular advancement by BSSO. To observe sagittal changes in PAS and in hyoid bone distance to MP both pre- and postoperative cephalograms were analyzed using WinCeph^® 8.0 software. For the statistical analyses paired T-test and multivariate logistic regression models were used.

Results: By the surgical-orthognathic treatment the sagittal dimension of PAS showed variable changes but it mainly diminished when the mandibular advancement exceeded 6?mm. In most cases the hyoid bone moved superiorly by BSSO. Logistic regression models showed that males, patients with narrow PAS at the baseline, and those with counterclockwise rotation of the mandible by the treatment gained more increase in PAS. However, an increase in sagittal PAS dimension tended to relapse over time. Concerning the movement of the hyoid it was found that the more PAS increased the less hyoid moved superiorly. In males the change in hyoid position was more obvious than in females.

Conclusion: Males, patients with narrow PAS at the baseline, and those whose mandible moved in the counterclockwise direction with moderate advancement gained more retrolingual airway patency by BSSO.     

Changes in the oropharyngeal airway of Class II patients treated with the mandibular anterior repositioning appliance

Objective:To evaluate the effects of functional appliance treatment on the oropharyngeal airway volume, airway dimensions, and anteroposterior hyoid bone position of growing Class II patients.Materials and Methods:Twenty Class II white patients (mean age, 11.7 ± 1.75 years) treated with the MARA followed by fixed appliances were matched to an untreated control sample by cervical vertebrae maturation stage at pretreatment (T1) and posttreatment (T2) time points. Cone beam computed tomography scans were taken at T1 and T2. Dolphin3D imaging software was used to determine oropharyngeal airway volume, dimensions, and anteroposterior hyoid bone position.Results:Multivariate ANOVA was used to evaluate changes between T1 and T2. Oropharyngeal airway volume, airway dimensions, and A-P position of the hyoid bone increased significantly with functional appliance treatment. SNA and ANB decreased significantly in the experimental group (P ≤ .05). Changes in SNB and Sn-GoGn failed to reach statistical significance.Conclusions:Functional appliance therapy increases oropharyngeal airway volume, airway dimensions, and anteroposterior hyoid bone position in growing patients.     

Class II malocclusion treatment effects with Jones Jig and Distal Jet followed by fixed appliances

Objectives:To compare the skeletal, dentoalveolar, and soft tissue changes in Class II malocclusion patients treated with Jones Jig and Distal Jet distalizers followed by fixed appliances.Materials and Methods:The experimental groups comprised 45 Class II malocclusion subjects divided into two groups. Group 1 consisted of 25 patients treated with the Jones Jig, and group 2 consisted of 20 patients treated with the Distal Jet. Group 3 comprised 19 untreated Class II subjects. Cephalograms were analyzed before and after orthodontic treatment. For intergroup comparisons, one-way analysis of variance and post hoc Tukey tests were performed.Results:During treatment, the experimental groups exhibited significant increases in occlusal plane inclination and maxillary second molar mesial tipping. Additionally, the molar relationship improved and overjet decreased significantly in the experimental groups. The Jones Jig group showed greater mandibular incisor proclination and greater overbite reduction than the control group. No significant intergroup differences in nasolabial angle changes were found.Conclusions:Treatment protocols using the Jones Jig and Distal Jet followed by fixed appliances were effective in correcting Class II malocclusion by means of dentoalveolar changes without significant skeletal and soft tissue changes. The experimental groups showed occlusal plane clockwise rotation and greater mesial tipping of maxillary second molars when compared to the untreated group.     

Uvulo-glosso-pharyngeal dimensions in different anteroposterior skeletal patterns

The aim of this study was to investigate the uvulo-glosso-pharyngeal dimensions in subjects with different anteroposterior jaw relationship. Cephalometric radiograph of 90 subjects (45 females and 45 males, aged 14-17 years) were divided into three groups according to the ANB angle, ie, group 1, skeletal Class I (ANB angle 1-5); group 2, skeletal Class II (ANB angle >5); and group 3, skeletal Class III (ANB angle <1). In addition, each group was divided into two subgroups according to sex. Statistical analysis was undertaken using analysis of variance and least significant difference test. Pearson's Correlation test was also performed. Sex differences were found in Class I and III subjects. No sex differences were detected in Class II subjects. On average, tongue length was significantly shorter in Class III subjects (P < .05), tongue height was reduced in Class II female subjects, the soft palate was thicker in Class III females and the vertical airway length (VAL) was reduced in Class II male subjects (P < .01). In Class II subjects, the hyoid bone was closer to the mandible vertically and to C3 horizontally compared with Class I (P < .01) and Class III (P < .001) male subjects. Anteroposterior skeletal pattern showed a weak, but significant correlation with inferior pharyngeal airway space (R = -0.24, P = .024), vertical position of hyoid bone in relation to mandibular plane (R = -0.26, P = .014), and anteroposterior position of hyoid bone in relation to C3 (R = -0.561, P = .000). In conclusion, uvulo-glosso-pharyngeal dimensions are affected by anteroposterior skeletal pattern.     

成人骨性Ⅲ类错口咽气道容积大小和舌骨位置的锥形束CT研究

目的:应用锥形束CT（cone-beam computed tomography,CBCT）和Invivo5软件测量成人骨性Ⅲ类错口咽气道容积大小和舌骨位置,分析上、下颌骨的位置对气道的影响,为正畸临床评估口咽气道容积及舌骨位置提供理论依据。方法:随机筛选CBCT资料,按纳入标准和上、下颌骨矢状位置,将研究对象分为3组,筛选出60例骨性Ⅰ类错作为对照组;将成人骨性Ⅲ类错分为上颌后缩组和下颌前突组,每组60例。采用第三方软件Invivo5将CBCT扫描数据进行三维重建,建立三维坐标系,应用测量工具测量口咽气道及舌骨位置,采用SPSS19.0软件包对上述3组进行两两比较。结果:成人骨性Ⅲ类下颌前突组分别较上颌后缩组、骨性Ⅰ类组口咽气道容积大（P<0.05）,但骨性Ⅲ类上颌后缩组与骨性Ⅰ类组口咽气道容积无显著差异（P>0.05）;舌骨矢状向位置由前到后为骨性Ⅲ类下颌前突组、骨性Ⅲ类上颌后缩组、骨性Ⅰ类组（P<0.05）;舌骨垂直向位置,骨性Ⅲ类下颌前突组显著高于上颌后缩组、骨性Ⅰ类组（P<0.05）,但骨性Ⅲ类上颌后缩组与骨性Ⅰ类组无显著差异（P>0.05）。结论:成人不同骨性错畸形上气道三维特征不同,下颌骨矢状位置、长度较上颌骨对口咽气道容积、形态、走向、舌骨矢状位置影响更为显著。CBCT及Invivo5是评价上气道的实用工具,可为正畸临床评估骨性错患者上气道三维结构及舌骨位置、制订合理有效的治疗方案提供指导。     

Treatment changes of hypo- and hyperdivergent Class II Herbst patients

Objectives:To determine the relative effects of Herbst appliance therapy in hypo- and hyperdivergent patients.Materials and Methods:The treated group included 45 growing Class II, division 1, patients treated with stainless steel crown Herbst appliances, followed by fixed edgewise appliances. The untreated control group consisted of 45 Class II, division 1, subjects, matched to the treated sample based on Angle classification, age, sex, and pretreatment mandibular plane angle (MPA). Subjects were categorized as hypo- or hyperdivergent based on their MPAs. Pre- and posttreatment cephalograms were traced and superimposed on cranial base and mandibular structures.Results:The primary effect of the Herbst in terms of maxillomandibular correction was in the maxilla. It significantly restricted maxillary growth, producing a “headgear effect.” Mandibular treatment changes depended on divergence. Hyperdivergent patients experienced a deleterious backward true mandibular rotation with Herbst treatment. Hypodivergent patients, as well as untreated hypo- and hyperdivergent controls, underwent forward true mandibular rotation. However, hypodivergent chins did not advance any more than expected for untreated hypodivergent Class II patients.Conclusions:Hypo- and hyperdivergent patients benefit from the Herbst''s headgear effect. While the mandibular growth of hypodivergent patients overcomes the negative rotational effects, hyperdivergent patients undergo a deleterious backward mandibular rotation and increases in facial height.     

骨性Ⅱ类不同矢状骨面型成人上气道容积和舌骨位置的锥形束CT研究

目的 应用CBCT研究成人骨性Ⅱ类不同矢状骨面型上气道的容积大小和舌骨位置.方法 按标准筛出180例CBCT影像资料并分为骨性Ⅰ类组,骨性Ⅱ类下颌后缩组和骨性Ⅱ类上颌前突组,每组60例.In vivo 5 软件进行三维重建,测量上气道容积及舌骨位置指标,并进行统计学分析.结果 三组鼻咽气道大小无统计学差异(P>0.05).口咽气道容积测量,骨性Ⅰ类组>骨性Ⅱ类上颌前突组>骨性Ⅱ类下颌后缩组,且下颌后缩组明显小于其他两组(P<0.05).三组之间舌骨位置的评价参数H-VPS之间存在差异(P<0.05).结论 骨性Ⅱ类不同矢状骨面型成人口咽气道容积大小存在差异,骨性Ⅱ类下颌后缩组舌骨矢状位置最靠后.颌骨、气道和舌骨三者之间存在一定关联.     

Dentoskeletal effects produced by a Jasper Jumper with an anterior bite plane

Objective:The aim of this retrospective study was to evaluate the dentoskeletal effects produced by a modified Jasper Jumper with an anterior bite plane for the correction of Class II division 1 malocclusion.Materials and Methods:A sample of 32 growing patients (mean age  =  11.9 ± 1.4 years) with Class II division 1 malocclusion and increased overbite were treated with a modified Jasper Jumper (JJ) and anterior bite plane protocol and compared with a matched control group of 30 subjects with untreated Class II malocclusion (mean age 12.2 ± 0.8 years). Lateral cephalograms were taken before treatment (T1) and at the end of comprehensive treatment (T2). Mean treatment duration was 2.1 ± 0.4 years. The T1–T2 changes in the two groups were compared with Student’s t-tests for independent samples.Results:The JJ group was successfully treated to a Class I occlusal relationship with a significant reduction in overjet (–3.9 mm, P < .001) and overbite (–3.1 mm, P < .001). The JJ group exhibited a significant increase in mandibular length and a significant improvement in maxillomandibular sagittal skeletal relationships. The lower incisors were significantly proclined, while the lower first molars demonstrated significant movement in a mesial direction.Conclusions:Use of a modified JJ appliance and anterior bite plane is an effective protocol for the treatment of Class II malocclusion with increased overbite and greater skeletal (75%) than dentoalveolar (25%) effects mainly at the mandibular level.     

Changes in pharyngeal airway dimensions and hyoid bone position after maxillary protraction with different alternate rapid maxillary expansion and construction protocols: A prospective clinical study

Objective:To evaluate the changes in pharyngeal airway dimensions and the position of the hyoid bone after maxillary protraction with different alternate rapid maxillary expansion and construction (Alt-RAMEC) protocols in patients with skeletal class III malocclusion as a result of maxillary retrusion.Material and Methods:The patients with skeletal class III malocclusions were consecutively divided into two groups. Group 1 consisted of 17 patients (11 boys and 6 girls, mean age 11.31 ± 1.71 years) who had the Alt-RAMEC protocol for 5 weeks, and group 2 consisted of 17 patients (10 boys and 7 girls, mean age 11.64 ± 1.24 years) who had the Alt-RAMEC procedure for 9 weeks. In this study, 4 angular and 13 linear measurements were performed to evaluate the skeletal and pharyngeal airway changes that occurred after maxillary protraction.Results:A significant increase in the maxillary growth, inhabitation of mandibular growth, and clockwise rotation of the mandible caused the improvement of the maxillo-mandibular relationship in both groups. Those changes caused a significant increase in the upper pharyngeal airway dimension (P < .01) and affected the vertical position of the hyoid bone in both groups (P < .05 and P < .01, respectively). However, changes that occurred in both groups were found to be similar for all airway variables (P > .05).Conclusion:Upper pharyngeal dimension and vertical position of the hyoid bone were affected by the maxillary protraction with different Alt-RAMEC protocols. There were no statistically significant differences between the groups.     

The effect of zigzag elastics in the treatment of Class II division 1 malocclusion subjects with hypo- and hyperdivergent growth patterns. A pilot study.

The aim of this study was to investigate the effect of zigzag elastics in the treatment of Class II division 1 malocclusion subjects with hypo- or hyperdivergent growth patterns. Two groups were established, each consisting of 10 subjects classified as hypo- or hyperdivergent according to their pre-treatment SN-GoGn angle. The cephalometric radiographs taken before and after an elastic application period of approximately 4 months were used to generate 22 variables. In both groups, there were no statistically significant differences in the vertical position of the lower molars, the SN-GoGn angle or the inclination of the lower incisors, whereas the sagittal skeletal relationship was improved as a result of an increase in the SNB angle and the mandibular length (P < 0.01). Upper incisor extrusion was statistically significant in both groups (P < 0.05). The downward rotation of the occlusal plane and the increase in overbite were found to be significant in the hypodivergent group (P < 0.05). Significant differences were observed between the groups in the extrusion of the upper incisor, the inclination of the occlusal plane, and the amount of overbite (P < 0.05). The results show that the zigzag elastic system is preferable, especially in hyperdivergent Class II division 1 subjects, as the use of such elastics does not cause an unfavourable effect on vertical jaw base relationship.     

Nonsurgical treatment of a hyperdivergent skeletal Class III patient with mini-screw–assisted mandibular dentition distalization and flattening of the occlusal plane

Treatment of hyperdivergent skeletal Class III malocclusion is challenging for orthodontists, and orthognathic-orthodontic treatment is usually required. This report presents the successful nonsurgical treatment of a 20-year-old man who had a skeletal Class III malocclusion with anterior open bite, anterior and posterior crossbite, hyperdivergent growth pattern, steep occlusal plane, early loss of three first molars, and an uncommon convex profile with a retruded chin. An orthodontic camouflage treatment plan was chosen based on the etiology and the patient''s complaints. Tooth #37 was extracted. Miniscrews were used for uprighting and intruding of the lower molars, distalization of the lower dentition, and flattening of the occlusal plane. After 34 months of active treatment, Class I relationships, proper anterior overjet and overbite, flat occlusal plane, and an esthetic facial profile were achieved. The results demonstrated that the biomechanics involved in the nonsurgical treatment assisted with miniscrews to distalize the mandibular dentition and flatten the occlusal plane while keeping the mandibular plane stable was effective for treating this hyperdivergent skeletal Class III patient with a convex profile and anterior open bite.     

安氏Ⅰ类错牙合畸形牙合平面与上气道形态功能及舌骨位置的相关性

目的 探讨安氏Ⅰ类错牙合畸形牙合平面与上气道形态功能与舌骨位置的相关性及其临床意义。方法 随机选取2014年1月—2019年1月治疗的安氏Ⅰ类错牙合畸形牙合患者120例,观察正畸治疗前与治疗3个月时上气道形态功能指标（SNA、SNB、ANB、SPPS、MPS、IPS、S-PNS、Ba-PNS）变化情况;根据牙合平面角度（OP-SN）将患者分为A（35例,10°≤OP-SN<15°）、B（45例,15°≤OP-SN<20°）、C（40例,20°≤OP-SN<25°）3组,观察治疗3个月时3组患者睡眠指标变化[平均血氧饱和度（MSaO₂）、最低血氧饱和度（LSaO₂）、氧减指数、平均脉率]以及牙合平面（OP-SN）、上气道形态功能与舌骨位置（H-PS、H-VPS）变化情况,采用SPSS 20.0软件中的Pearson相关性分析评价牙合平面与上气道形态功能以及与舌骨位置的相关性。结果 正畸治疗后SNA、MPS、IPS、S-PNS、Ba-PNS较治疗前显著升高（P<0.05）,而SNB、ANB、SPPS较治疗前显著下降（P<0.05）;3组不同牙合平面中OP-SN、ANB角随牙合平面角度升高而升高,而SNA、SNB角随牙合平面角度升高而降低,组间差异具有统计学意义（P<0.05）;OP-SN与SNA、SNB呈负相关（P<0.05）,与ANB呈正相关（P<0.05）;SNA、SNB、ANB、SPPS、MPS、TPS上气道形态测量指标与H-PS、H-VPS指标呈正相关（P<0.05）。结论 安氏I类错牙合畸形牙合人群平面与上气道形态功能及舌骨位置密切相关。     

Quantitative evaluation of retromolar space in adults with different vertical facial types:: Cone-beam computed tomography study

ObjectiveTo investigate the differences in mandibular retromolar space among skeletal Class I subjects with different vertical divergence using cone-beam computed tomography (CBCT).Materials and MethodsA total of 123 skeletal Class I patients (aged 20–40 years) were categorized into hypodivergent, normodivergent, and hyperdivergent groups based on S-N/Go-Me and facial height index (FHI). Mandibular retromolar space was measured at four planes parallel to the occlusal plane along the sagittal line and molar cuspal line, respectively. The mandibular retromolar space was compared among the three vertical groups.ResultsThe hyperdivergent group had a significantly smaller mandibular retromolar space compared with the other two groups, while the hypodivergent group had the largest retromolar space. In addition, the hyperdivergent group had a larger number of subjects whose roots contacted the lingual cortex of the mandibular body.ConclusionsThe hyperdivergent group tends to exhibit the smallest mandibular retromolar space and highest risk of cortex contact. Clinicians should keep in mind that successful molar distalization requires sufficient retromolar space, especially for hyperdivergent subjects, which should be verified with CBCT.     

双侧下颌升支矢状劈开截骨术对男性下颌前突患者舌骨位置及咽气道间隙影响研究

目的　研究双侧下颌升支矢状劈开截骨术（BSSRO）对男性下颌前突患者舌骨位置和咽气道间隙的影响,探讨BSSRO与阻塞性睡眠呼吸暂停低通气综合征（OSAHS）的关系。方法　选择2012—2017年于中国医科大学附属口腔医院行BSSRO的男性下颌前突畸形患者30例作为病例组,分别于术前、术后1 ~ 2周及术后6 ~ 12个月拍摄头颅侧位片;选择同期具有正常矢状骨面型的30例男性成年正畸治疗患者作为对照组,正畸治疗前拍摄头颅侧位片。AutoCAD软件测量上下颌骨位置、舌骨位置及咽气道间隙相关测量项目,比较分析病例组术前、术后的上下颌骨位置、舌骨位置和咽气道间隙的变化以及病例组与对照组之间的差异。结果　病例组术后下颌骨后移。病例组术前与对照组相比,舌骨测量值中舌骨体最前上点（H 点）到X 轴的垂直距离（H-X）、H 点到下颌平面的垂直距离（H-MP）显著减小（P < 0.05）,H 点到第三颈椎最前下点（C3点）的距离（H-C3）显著增加（P < 0.05）;咽气道测量值中腭垂尖至中咽壁点距离（U-MPW）、下颌骨后下缘与舌背交点到咽后壁距离（MT-MTP）、过会厌最上点（E点）咽腔间隙距离（EPA-EPP）显著增加（P < 0.05）。病例组术后1 ~ 2周及术后6 ~ 12个月与术前相比,H-X、H-MP显著增加,H-C3显著减小,U-MPW、MT-MTP、EPA-EPP显著减小（P < 0.05）;术后6 ~ 12个月与术后1 ~ 2周相比,H-X显著减小,H-C3显著增加,U-MPW、MT-MTP显著增加（P < 0.05）。病例组术后6 ~ 12个月与对照组相比,反映舌骨位置和咽气道间隙的各项指标差异均无统计学意义（均P > 0.05）。结论　男性下颌前突患者行BSSRO术后短期内舌骨位置向后下移位,咽气道间隙减小,随时间推移,逐渐回复到正常范围,提示男性下颌前突患者行BSSRO术后发生OSAHS的风险不大。     

Pharyngeal airway space changes after counterclockwise rotation of the maxillomandibular complex.

The purpose of this study was to evaluate the effects of double-jaw surgery with counterclockwise rotation of the maxillomandibular complex on the pharyngeal airway space and velopharyngeal anatomy in patients with high occlusal plane facial morphology. Fifty patients (22 men, 28 women) with high occlusal plane facial morphology underwent double-jaw surgery with counterclockwise rotation of the maxillomandibular complex. The patients were divided into 2 groups: group 1, 30 patients (8 men, 22 women) who underwent maxillary and mandibular advancement and group 2, 20 patients (14 men, 6 women) who underwent maxillary advancement and mandibular setback. Presurgery and postsurgery lateral cephalometric radiographs were analyzed to correlate changes in pharyngeal airway space dimensions and velopharyngeal anatomy with maxillary and mandibular positional changes. The calibration showed a more than 0.94 correlation for both intra- and interoperator error. The average follow-up time was 29.6 months in group 1 and 22.2 months in group 2. Mean maxillary surgical change at point A was 4.15 mm in group 1 and 2.5 mm in group 2. Mean mandibular surgical change at the genial tubercles was 7.5 mm in group 1 and -4.95 mm in group 2. After surgery, group 1 patients had an increase in pharyngeal airway space of 47% at the soft palate and 76% at the base of the tongue relative to the amount of mandibular advancement. Group 2 patients had a decrease in pharyngeal airway space of 47% at the soft palate and 65% at the base of the tongue relative to the amount of mandibular setback. Double-jaw surgery with counterclockwise rotation of the maxillomandibular complex significantly affects the pharyngeal airway space and velopharyngeal anatomy in patients with high occlusal plane facial morphology, with both mandibular advancement and setback.     

Three-dimensional changes of the hyoid bone and airway volumes related to its relationship with horizontal anatomic planes after bimaxillary surgery in skeletal Class III patients

Objective:To evaluate longitudinal changes of the hyoid bone position and pharyngeal airway space after bimaxillary surgery in mandibular prognathism patients.Materials and Methods:Cone-beam computed tomography scans were taken for 25 mandibular prognathism patients before surgery (T0), 2 months after surgery (T1), and 6 months after surgery (T2). The positional displacement of the hyoid bone was assessed using the coordinates at T0, T1, and T2. Additionally, the volume of each subject''s pharyngeal airway was measured.Results:The mean amount of posterior maxilla impaction was 3.76 ± 1.33 mm as the palatal plane rotated 2.04° ± 2.28° in a clockwise direction as a result of bimaxillary surgery. The hyoid bone moved backward (P < .05, P < .001) and downward (P > .05, P < .05) at 2 months and 6 months after surgery, while the total volume of the pharyngeal airway significantly decreased at the same time points (P < .001, P < .001). There was significant relationship between the changes of the hyoid bone position and airway volume at 2 months after surgery (P < .05). The change of the palatal plane angle was positively correlated to the decrease in the total airway volume (P < .001).Conclusions:The null hypothesis was rejected. The hyoid bone moved inferoposteriorly, and the pharyngeal airway volume decreased for up to 6 months after bimaxillary surgery. The decrease in the pharyngeal airway volume was correlated to the changes in the palatal plane inclination and the positional change of the hyoid bone.     

Effects of fixed functional therapy on tongue and hyoid positions and posterior airway

Objective:To evaluate how therapy with a fixed functional appliance affects airway dimensions, dentoalveolar changes, and tongue and hyoid positions.Materials and Methods:A retrospective study was carried out on 46 pre- and posttreatment lateral cephalometric radiographs of 23 post-peak Class II patients (12 girls, 11 boys) treated with a Forsus Fatigue Resistant Device (FRD) appliance. The radiographies were taken at the start and at the end of Forsus FRD appliance therapy when a Class I or overcorrected Class I canine and molar relationship was achieved. The process took an average of 5 months 13 days ± 1 month 4 days. Skeletal and dental parameters were measured using Dolphin software, and the sagittal airway area was measured by AutoCAD software.Results:Analyses of the pre- and posttreatment means revealed that there was no statistically significant skeletal correction of the sagittal malocclusion; increase of lower incisor inclination, decrease of upper incisor inclination, decrease of interincisal angle, and rotation of occlusal plane all contributed to the reduction of overjet. The tongue area and intermaxillary space area increased in response to these dentoalveolar changes; however, there was no statistically significant change in the hyoid position or the oropharyngeal area between the two time points.Conclusions:The dentoalveolar changes produced by Forsus FRD appliance did not cause any significant posterior airway changes in young adult patients.     

Cone-beam evaluation of pharyngeal airway space in adult skeletal Class II patients with different condylar positions

Objectives:To test the null hypothesis that there is no significant difference in pharyngeal airway space among adult skeletal Class II patients with different condylar positions using cone-beam computed tomography (CBCT).Materials and Methods:The CBCT records of 60 patients with skeletal Class II malocclusion (ANB angle ≥ 4°, Wits ≥ 0) were selected from the CBCT database. According to the condyle position, the patients were divided in three groups: anterior group (CD ≤ −12%), centric group (−12% ≤ CD ≤ +12%), and posterior group (CD ≥ +12%). Three-dimensional (3D) pharyngeal airway models were reconstructed using InvivoDental software 5.1.3. The volume and area of the pharyngeal airway space were measured in the 3D airway model.Results:The volume and area of the pharyngeal airway space in the centric group were significantly smaller than those in the posterior group (P < .01). The volume and area of the pharyngeal airway space were smallest in the anterior group and significantly increased in the centric and posterior groups (P < .001).Conclusions:The null hypothesis was rejected. Significant differences were noted in pharyngeal airway space among adult skeletal Class II patients with different condylar positions.