Three-dimensional evaluation of upper airway following rapid maxillary expansion: A CBCT study

Objectives:To evaluate, by using cone beam computed tomography, the skeletal, dental, oropharyngeal (OP) airway volume, and nasal passage (NP) volume changes that occur after rapid maxillary expansion (RME).Materials and Methods:Two groups were selected, each with 35 patients (15 males, 20 females), an RME group (mean age, 14.02 ± 1.46 years) and a control group (mean age, 14.10 ± 1.44 years). The RME group consisted of patients with maxillary constriction who were treated with Hyrax palatal expanders, and the control group comprised age- and sex-matched patients who underwent comprehensive orthodontic treatment without the use of a rapid maxillary expander.Results:All of the transverse skeletal (medial orbital width, lateral nasal width, maxillary width, and mandibular width) and interdental (intermolar, interpremolar, and intercanine) parameters were significantly enlarged in the RME group. A statistically significant increase in airway variables was seen in both groups between pretreatment (T0) and final records (T1). The mean increase of NP airway volume for the RME group (1719.9 ± 1510.7 mm³) was twofold compared with the control group (813.6 ± 1006.7 mm³), and no intergroup significant difference was found for the OP volume.Conclusions:Rapid maxillary expansion creates a significant increase in nasal passage airway volume but no significant change in the oropharyngeal airway volume.     

Dental and skeletal effects after total arch distalization using modified C-palatal plate on hypo- and hyperdivergent Class II malocclusions in adolescents

ObjectivesTo compare the dental and skeletal treatment effects after total arch distalization using modified C-palatal plates (MCPPs) on adolescent patients with hypo- and hyperdivergent Class II malocclusion.Materials and MethodsThe study group included 40 patients with Class II malocclusion (18 boys and 22 girls, mean age = 12.2 ± 1.4 years) treated with MCPPs. Fixed orthodontic treatment started with the distalizing process in both groups. Participants were divided into hypo- or hyperdivergent groups based on their pretreatment Frankfort mandibular plane angle (FMA) ≤22° or ≥28°, respectively. Pre- and posttreatment lateral cephalograms were digitized, and 23 variables were measured and compared for both groups using paired and independent t-tests.ResultsThe hyper- and hypodivergent groups showed 2.7 mm and 4.3 mm of first molar crown distalizing movement, respectively (P < .001). The hypodivergent group had a slight 2.2° crown distal tipping of first molars compared with 0.3° in the hyperdivergent group. After distalization, the FMA increased 3.1° and 0.3°, in the hypodivergent and hyperdivergent groups, respectively (P < .001). SNA decreased in the hypodivergent group, while other skeletal variables presented no statistically significant differences in the changes between the groups.ConclusionsThe hypodivergent group showed more distal and tipping movement of the maxillary first molar and increased FMA than the hyperdivergent group. Therefore, clinicians must consider vertical facial types when distalizing molars using MCPPs in Class II nonextraction treatment.     

应用CBCT评价隐形矫治技术远中移动上颌磨牙的临床疗效

目的 通过锥形束计算机断层扫描(CBCT)三维测量评估隐形矫治技术远中移动上颌磨牙的疗效.方法 收集应用Invisalign隐形矫治器作上颌磨牙远中移动的病例,共15例,平均年龄27岁8个月.使用微种植体或Ⅱ类牵引增强前牙支抗,治疗前后分别拍摄CBCT.使用SimPlant 11.04软件测量上颌磨牙三维方向移动量和切牙近远中向移动量,与预期牙移动量作比较,使用SPSS 19.0软件包进行统计分析.结果 第一和第二磨牙预期远中移动量平均为(2.33±1.06) mm,实际移动量为(1.92±1.00)mm,表达率为82.4％.与预期移动量相比,上颌磨牙实际远中倾斜4.12°、颊向倾斜4.19°,第一磨牙压人0.99mm,第二磨牙压入1.88mm.磨牙三维方向的实际与预期移动量之间的差异均有统计学意义(P＜0.01),而切牙的实际与预期近远中向位移无统计学差异(P.0.05).结论 Invisalign隐形矫治技术能够有效地远中移动上颌磨牙,伴有压入和轻微的远中和颊向倾斜.远中移动上颌磨牙时,使用微种植支抗或Ⅱ类牵引能够有效控制前牙支抗.     

Assessment of changes in the nasal airway after nonsurgical miniscrew-assisted rapid maxillary expansion in young adults

Objectives:To evaluate changes in the volume and cross-sectional area of the nasal airway before and 1 year after nonsurgical miniscrew-assisted rapid maxillary expansion (MARME) in young adults.Materials and Methods:Fourteen patients (mean age, 22.7 years; 10 women, four men) with a transverse discrepancy who underwent cone beam computed tomography before (T0), immediately after (T1), and 1 year after (T2) expansion were retrospectively included in this study. The volume of the nasal cavity and nasopharynx and the cross-sectional area of the anterior, middle, and posterior segments of the nasal airway were measured and compared among the three timepoints using paired t-tests.Results:The volume of the nasal cavity showed a significant increase at T1 and T2 (P < .05), while that of the nasopharynx increased only at T2 (P < .05). The anterior and middle cross-sectional areas significantly increased at T1 and T2 (P < .05), while the posterior cross-sectional area showed no significant change throughout the observation period (P > .05).Conclusions:The results demonstrate that the volume and cross-sectional area of the nasal cavity increased after MARME and were maintained at 1 year after expansion. Therefore, MARME may be helpful in expanding the nasal airway.     

Three-dimensional airway evaluation in 387 subjects from one university orthodontic clinic using cone beam computed tomography

Objective:To determine the linear, volumetric, and cross-sectional area measurements in a large sample of subjects seeking treatment in a university clinic of orthodontics.Materials and Methods:Cone-beam computed tomography (CBCT) scans from 387 patients were analyzed retrospectively. All scans were loaded into the 3dMDvultus program (Atlanta, Ga) for airway analysis using automated segmentation. Gender, age, height, weight, airway length, volume, and area of maximum constriction were collected.Results:The rostrocaudal length of the airway increased with age until the age of 15 years in female subjects but continued to increase in male subjects and ranged from 44 to 88 mm over the period of 8 to 18 years of age with the gender data combined. The volume of the airway increased through the entire 11-year age range from 2000 mm³ to 27,000 mm³. The rate of airway volume increased at a slower rate in female than in male subjects. The smallest cross-sectional area increased with age ranging from 20 to 250 mm² but at a slower rate with female subjects, while male subjects demonstrated a more exponential increase after the age of 13 years.Conclusions:The human airway increases in length and volume during a rapid period of craniofacial growth in patients between the ages of 8 and 18 years, and the site of maximum cross-sectional area constriction can vary.     

Retrospective CBCT analysis of airway volume changes after bone-borne vs tooth-borne rapid maxillary expansion

Objectives:To compare changes in upper airway volume after maxillary expansion with bone- and tooth-borne appliances in adolescents and to evaluate the dentoskeletal effects of each expansion modality.Materials and Methods:This retrospective study included 36 adolescents who had bilateral maxillary crossbite and received bone-borne maxillary expansion (average age: 14.7 years) or tooth-borne maxillary expansion (average age: 14.4 years). Subjects had two cone beam computed tomography images acquired, one before expansion (T₁) and a second after a 3-month retention period (T₂). Images were oriented, and three-dimensional airway volume and dentoskeletal expansion were measured. Analysis of variance was used to test for differences between the two expansion methods for pretreatment, posttreatment, and prepost changes. Paired t-tests were used to test for significance of prepost changes within each method.Results:Both groups showed significant increase only in nasal cavity and nasopharynx volume (P < .05), but not oropharynx and maxillary sinus volumes. Intermolar and maxillary width increased significantly in both groups (P < .05); however, the buccal inclination of maxillary molars increased significantly only in the tooth-borne group (P < .05). There was no significant difference between tooth- and bone-borne expansion groups, except for the significantly larger increase in buccal inclination of the maxillary right first molar after tooth-borne expansion.Conclusions:In adolescents, both tooth- and bone-borne RME resulted in an increase in nasal cavity and nasopharynx volume, as well as expansion in maxillary intermolar and skeletal widths. However, only tooth-borne expanders caused significant buccal tipping of maxillary molars.     

A comparison of treatment effects of total arch distalization using modified C-palatal plate vs buccal miniscrews

Objective:The purpose of this study was to compare the treatment effects of palatally vs buccally placed temporary anchorage devices.Materials and Methods:Of 40 Class II division 1 malocclusion patients, 22 were treated with modified C-palatal plate (MCPP) appliances (age 21.9 ± 6.6 years), and 18 (age 24.2 ± 6.8 years) were treated with buccally placed miniscrews between the maxillary first molar and second premolar. A total of 26 linear and angular measurements were analyzed on pre- and posttreatment lateral cephalograms. Multivariate analysis of variance was performed to evaluate the treatment effects within each group and to compare the effects between groups.Results:Overall, the MCPP appliances showed 4.2 mm of distalization, 1.6 mm of intrusion of the first molar with 2° tipping, and 0.8 mm extrusion of incisors. The miniscrew group resulted in 2.0 mm of distalization, 0.1 mm intrusion of the first molar with 7.2° tipping, and 0.3 mm of incisor extrusion. Regarding soft tissue change, in the MCPP group, the upper lip was significantly retracted (P < .001).Conclusions:Comparing the treatment effects between MCPP appliances and buccal miniscrews, the MCPP appliances showed greater distalization and intrusion with less distal tipping of the first molar and more extrusion of the incisor compared to the buccal miniscrews.     

高角型病例不同矢状骨面型口咽气道形态特征的研究

目的 通过CBCT影像比较高角不同矢状骨面型成人口咽气道三维形态的差异,探讨口咽气道各段与颌面部骨骼形态间的关系.方法 选取60例高角成人患者,按照ANB角的大小将所有患者分为骨性Ⅱ类、Ⅰ类、Ⅲ类三组,每组20例患者,男女比例为1:1.利用InvivoDental 5.1分析软件将每例患者CBCT图像的正中矢状平面和轴向平面在冠状、矢状、轴向三维空间进行调整,然后对腭咽、舌咽、口咽总气道进行线距、体积以及最小截面积测量,比较不同组间以及不同性别间的差异.结果 不同矢状骨面型间只有会厌顶横径(W-ETP)的差异具有统计学意义(P<0.05);不同性别间舌咽气道高(H-GP)、口咽气道总高(H-Total)、后鼻棘横径(W-PNSP)、会厌顶横径(W-ETP)、舌咽气道体积(V-GP)、口咽气道总体积(V-Total)的差异具有统计学意义(P<0.05),且男性均大于女性.结论 高角不同矢状骨面型成人口咽气道大小形态的差异仅体现在舌咽段最下端横径,男性口咽气道较女性更大更长.     

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.     

Three-dimensional space changes after premature loss of a maxillary primary first molar

Background.  A space maintainer is generally preferred when a primary first molar is lost before or during active eruption of the first permanent molars in order to prevent space loss. However, controversy prevails regarding the space loss after eruption of the permanent first molars.
Aim.  The purpose of this study was to examine spatial changes subsequent to premature loss of a maxillary primary first molar after the eruption of the permanent first molars.
Design.  Thirteen children, five girls and eight boys, expecting premature extraction of a maxillary primary first molar because of caries and/or failed pulp therapy, were selected. Spatial changes were investigated using a three-dimensional laser scanner by comparing the primary molar space, arch width, arch length, and arch perimeter before and after the extraction of a maxillary primary first molar. Also, the inclination and angulation changes in the maxillary primary canines, primary second molars, and permanent first molars adjacent to the extraction site were investigated before and after the extraction of the maxillary primary first molar in order to examine the source of space loss.
Results.  There was no statistically significant space loss on the extraction side compared to the control side ( P  = 0.33). No consistent findings were seen on the inclination and angulation changes on the extraction side.
Conclusions.  The premature loss of a maxillary primary first molar, in cases with class I molar relationship, has limited influence on the space in permanent dentition.     

Volumetric changes of the upper airway following maxillary and mandibular advancement using cone beam computed tomography

The objective of this project was to retrospectively evaluate changes in volume of different compartments of the upper airway in response to maxillary, mandibular, and bimaxillary advancement surgeries and to predict the extent of volumetric changes associated with these surgical movements. Pre- and post-surgical cone beam computed tomography scans of 36 patients were evaluated for changes in nasal cavity, nasopharyngeal, oropharyngeal, and hypopharyngeal compartments. The amount of movement for each surgery was measured from skeletal landmarks to reference planes and was correlated with volumetric changes. Maxillary advancement of 4.0 ± 2.2 mm increased the oropharyngeal volume significantly (41.40%), and mandibular advancement of 3.8 ± 1.6 mm also significantly increased the oropharyngeal volume (21.17%). Bimaxillary advancement of 5.1 ± 1.3 mm for the maxilla and 6.4 ± 3.1 mm for the mandible significantly increased nasopharyngeal (27.45%), oropharyngeal (66.39%), and hypopharyngeal (52.48%) volumes. Furthermore, for every millimeter anterior movement, oropharyngeal volume increased by 2319.2 ± 771.8 mm³. Bimaxillary advancement showed a greater increase than isolated maxillary and mandibular advancement in all pharyngeal compartments. Every millimeter of advancement in the bimaxillary group led to a significant increase in oropharyngeal volume, while every millimeter downward movement showed a significant increase in nasopharyngeal volume.     

高角成人口咽气道形态与颌骨形态间的关系

目的 通过锥形束CT(CBCT)图像分析高角成人口咽气道的形态与颌面骨骼形态间关系.方法在南昌大学附属口腔医院就诊的患者中随机选取60名高角成人患者的CBCT图像,利用InvivoDental 5.1分析软件对每位患者的口咽气道各部进行线距、体积以及最小截面积测量,将所有气道测量数据分别与颌骨形态相关指标进行Pearson相关分析.结果在男性组中SNB角与软腭尖矢状径、腭咽气道体积、舌咽气道体积、口咽气道总体积、最小截面积呈正相关,GoGn-SN角与软腭尖矢状径、会厌顶矢状径、腭咽气道体积、舌咽气道体积、口咽气道总体积、最小截面积呈负相关,S-Go/N-Me与软腭尖矢状径呈正相关;在女性组中SNA角与后鼻棘横径呈负相关,SNB角与舌咽气道高、后鼻棘横径、软腭尖横径呈负相关,GoGn-SN角与舌咽气道高呈正相关.结论高角成人口咽气道大小形态与颌骨形态间存在一定联系.在男性组中,随着下颌骨位置的前移,口咽气道有增大的趋势,随着下颌骨顺时针旋转,口咽气道有减小甚至阻塞的趋势;而在女性组中,随着上下颌骨位置的改变,口咽气道仅表现为局部形态的变化.     

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.