CBCT of skeletal changes following rapid maxillary expansion to increase arch-length with a development-dependent bonded or banded appliance

Objective:To assess the three-dimensional (3D) skeletal response to a standardized 5 mm of rapid maxillary expansion (RME) in growing children (6–15 years) with maxillary width deficiency and crowding.Materials and Methods:A bonded appliance was used prior to the eruption of the maxillary first premolars (Mx4s), and a banded appliance was used thereafter. A consecutive sample of 89 patients (29 boys and 60 girls) from a large pediatric dentistry and orthodontics practice was divided into four groups: 1) 6–8 years old (n  =  26), 2) 9–11 years old with unerupted Mx4s (n  =  21), 3) 9–11 years with erupted Mx4s (n  =  23), and 4) 12–15 years (n  =  19). For all patients, the 3D evaluation of dental and skeletal effects was performed with cone-beam computed tomography (CBCT).Results:For both appliances in all patients, CBCT confirmed a triangular pattern of expansion in both the frontal and sagittal planes. Overall, both appliances produced significant maxillary expansion (>80% of the 5-mm activation), but older children showed a progressively more dental (less skeletal) response. Comparison of the two types of expanders in the crossover sample, children aged 9–11 years, showed that the bonded RME produced the most efficient skeletal expansion in the preadolescent sample. Increased maxillary width at the level of the zygomaticomaxillary suture was the best indicator for development of maxillary arch circumference.Conclusion:Development-dependent appliances (bonded RPE before Mx4s erupt, and a banded device thereafter) provided optimal RME treatment for all children from age 6–15 years.     

Soft tissue profile changes after rapid maxillary expansion with a bonded expander

The aim of this study was to evaluate the short- and long-term treatment effects of rapid maxillary expansion (RME) on the soft tissue facial profile of subjects treated with a modified acrylic-hyrax device. The sample comprised 10 males and 10 females in the mixed dentition. Their average age was 9.3 years ± 10 months pre-treatment (T1), with a narrow maxilla and posterior crossbite, treated with a modified fixed maxillary expander with an occlusal splint. Lateral cephalometric radiographs obtained at T1, immediately post-expansion (T2), and after retention (T3) were used to determine possible changes in the soft tissue facial profile. The means and standard deviations for linear and angular cephalometric measurements were analysed statistically using analysis of variance and Tukey's test (α = 0.05). The measurements at T2 differed significantly from those at T1 and T3. However, RME did not produce any statistically significant alteration (P > 0.05) in the soft tissue profile for any of the cephalometric landmarks evaluated when compared at T1 and T3. The use of a fixed expander associated with an occlusal splint did not cause significant alterations in the soft tissue facial profile at T3. This modified device is effective for preventing the adverse vertical effects of RME such as an increase anterior face height in patients with a crossbite.     

Buccal alveolar bone changes following rapid maxillary expansion and fixed appliance therapy

ObjectivesTo assess factors that may be associated with buccal bone changes adjacent to maxillary first molars after rapid maxillary expansion (RME) and fixed appliance therapy.Materials and MethodsPretreatment (T1) and posttreatment (T2) cone-beam computed tomography scans were obtained from 45 patients treated with RME and preadjusted edgewise appliances. Buccal alveolar bone thickness was measured adjacent to the mesiobuccal root of the maxillary first molar 4 mm, 6 mm, and 8 mm apical to the cementoenamel junction, and anatomic defects were recorded. Paired and unpaired t-tests were used to compare alveolar bone thickness at T1 and T2 and to determine whether teeth with posttreatment anatomic defects had thinner initial bone. Correlation analyses were used to examine relationships between buccal alveolar bone thickness changes and amount of expansion, initial bone thickness, age at T1, postexpansion retention time, and treatment time.ResultsThere was a statistically significant reduction in buccal alveolar bone thickness from T1 to T2. Approximately half (47.7%) of the teeth developed anatomic defects from T1 to T2. These teeth had significantly thinner buccal bone at T1. Reduction in alveolar bone thickness was correlated with only one tested variable: initial bone thickness.ConclusionsRME and fixed-appliance therapy can be associated with significant reduction in buccal alveolar bone thickness and an increase in anatomic defects adjacent to the expander anchor teeth. Anchor teeth with greater initial buccal bone thickness have less reduction in buccal bone thickness and are less likely to develop posttreatment anatomic defects of buccal bone.     

腭中缝快速扩展前后下颌骨位置三维变化的螺旋CT测量研究

目的使用螺旋CT观察在上颌骨快速扩展(RME)前后下颌骨位置在三维方向上的变化。方法使用螺旋CT观测10例恒牙早期患者扩弓前后下颌骨各标志点间位置和角度改变。结果RME治疗后,下颌骨在前后向位置无明显改变;在垂直向向下移动并且有顺时针旋转的趋势。在水平向下颌骨有向非反侧移动的趋势,下颌骨后部较前部移动更明显。结论下颌骨位置在RME前后在矢状向,垂直向和水平向三个方向均发生了相应的改变。使用螺旋CT可以对这种三维位置变化进行详细研究。     

Three-dimensional changes of the naso-maxillary complex following rapid maxillary expansion

Objective:To assess the volumetric changes and the maxillary response of the naso-maxillary complex (NMC) following rapid maxillary expansion (RME).Materials and Methods:Thirty consecutive patients (14 males and 16 females) with a mean age at first observation of 9.5 ± 1.8 years for males and of 11.8 ± 1.7 years for females, presenting a posterior unilateral or bilateral crossbite and requiring RME, were selected for the study. Each patient underwent expansion to correct the transverse occlusal relationships. Computed tomography scans were taken before RME (T1) and at the end of the active expansion phase (T2). Measurements were performed on scanned images. The Kolmogorov-Smirnov test was performed; the mean differences between measurements at T1 and T2 were compared using the t-test (α  =  .05).Results:All volumetric, maxillary, transverse skeletal anterior and posterior variables as well as all dental anterior and posterior linear and angular variables representing the NMC displayed statistically highly significant increases after RME (P < .001).Conclusions:After RME the total volume of the NMC increased by 12%, the nasal volume by 17%, and the maxillary volume by 10.6%. The maxillary and the nasal contributions represented 69.75% and 30.25%, respectively.     

Three-dimensional assessment of the spheno-occipital synchondrosis and clivus after tooth-borne and bone-borne rapid maxillary expansion:: A retrospective CBCT study using voxel-based superimposition

ObjectivesTo assess changes in spheno-occipital synchondrosis after rapid maxillary expansion (RME) performed with conventional tooth-borne (TB) and bone-borne (BB) appliances.Materials and MethodsThis study included 40 subjects with transverse maxillary deficiency who received TB RME or BB RME. Cone-beam computed tomography images (CBCT) were taken before treatment (T0), and after a 6-month retention period (T1). Three-dimensional surface models of the spheno-occipital synchondrosis and basilar part of the occipital bone were generated. The CBCTs taken at T0 and T1 were registered at the anterior cranial fossa via voxel-based superimposition. Quantitative evaluation of Basion displacement was performed with linear measurements and Euclidean distances. The volume of the synchndrosis was also calculated for each time point as well as the Nasion-Sella-Basion angle (N-S-Ba°). All data were statistically analyzed to perform inter-timing and intergroup comparisons.ResultsIn both groups, there was a small increment of the volume of the synchondrosis and of N-S-Ba° (P < .05). Basion showed a posterosuperior pattern of displacement. However, no significant differences (P > .05) were found between the two groups.ConclusionsAlthough TB and BB RME seemed to have some effects on the spheno-occipital synchondrosis, differences were very small and clinically negligible.     

Effects of a bonded rapid maxillary expansion appliance during orthodontic treatment.

The aim of this prospective study was to evaluate changes in the transverse plane following use of an acrylic bonded rapid maxillary expansion (RME) appliance in growing individuals during the active phase of treatment. The sample comprised 14 consecutively treated orthodontic patients (11 girls, 3 boys) who required the use of an RME device on the basis of their individual treatment plans. The mean patient age at the start of treatment was 12.8 years, and the mean overall treatment time was 3.08 years. Seven posteroanterior cephalometric and two dental cast measurements were assessed. Repeated measure analysis of variance and Duncan's multiple range test were used to assess treatment changes. Lower nasal and maxillary base widths and angles, and upper intermolar width increased significantly during RME treatment. Upper intermolar and intercanine widths measured from the dental casts also increased significantly. Except for upper intercanine width, all measurements remained constant at the end of orthodontic treatment. The results of this study suggest that dentoskeletal changes in the transverse dimension following the use of an acrylic bonded RME are maintained satisfactorily at the end of fixed appliance therapy.     

Transverse dentoalveolar response of mandibular arch after rapid maxillary expansion (RME) with tooth-borne and bone-borne appliances:: A CBCT retrospective study

ObjectivesTo assess and compare spontaneous expansion of mandibular posterior teeth between tooth-borne (TB) and bone-borne (BB) rapid maxillary expansion (RME).Materials and MethodsThis study included 36 adolescents with bilateral maxillary crossbite receiving tooth-borne (average age: 14.4 ± 1.3 years) or bone-borne (average age: 14.7 ± 1.4 years) maxillary expansion. Cone beam computed tomography was acquired before expansion (T1) and after 6 months'' retention (T2). Specific linear and angular measurements were performed in the coronal view to assess buccal inclinations and widths of mandibular posterior units. All data were statistically analyzed.ResultsIn both groups there was a significant increase in buccal-lingual inclination of mandibular posterior teeth ranging from 1.67° to 2.30° in the TB group and from 1.46° to 2.11° in BB group. Mandibular posterior widths showed an increase ranging from 0.80 mm to 1.33 mm in TB group and from 0.64 mm to 0.96 mm in the BB group. No differences between groups were found for linear or angular measurements.ConclusionsA clinically significant gain of space in the mandibular arch should not be expected after RME.     

Evaluation of miniscrew-supported rapid maxillary expansion in adolescents: A prospective randomized clinical trial

Objectives:To evaluate and compare the dental and skeletal changes with conventional and miniscrew-supported maxillary expansion appliances in adolescents.Materials and Methods:Forty patients were divided into two groups, with one group receiving a tooth-borne expander and the other group receiving an expander supported by four miniscrews (bone-borne). Multiplanar coronal and axial slices obtained from cone-beam computed tomography images were used to measure the changes in transverse skeletal widths, buccal bone thickness, tooth inclination, and root length. Paired t-tests and independent-sample t-tests were used to compare the two expansion methods.Results:Bone-borne expansion increased the maxillary suture opening more than 2.5 times than tooth-borne expansion both anteriorly and posteriorly. Between the maxillary first premolars, sutural expansion accounted for 28% and 70% of the total transverse width increase in the tooth-borne and bone-borne expander groups, respectively. Similarly, 26% and 68% of the total expansion was of skeletal nature in the tooth-borne and bone-borne expander groups between the maxillary first molars. The pattern of expansion was variable, with most of the patients in both groups demonstrating a triangular-shaped sutural opening that was wider anteriorly. Subjects in the conventional group experienced significantly more buccal bone reduction and greater buccal inclination of the teeth. No significant differences were observed for root length measurements between the two groups.Conclusion:Use of bone-borne expansion in the adolescent population increased the extent of skeletal changes in the range of 1.5 to 2.8 times that of tooth-borne expansion and did not result in any dental side effects.     

上颌四眼圈簧扩弓后对上颌牙齿及上颌骨变化影响的 CBCT 研究

目的：使用锥体束 CT（CBCT）评估上颌四眼簧慢速扩弓后上颌牙齿及上颌骨宽度的变化。方法：选择13例需要综合性正畸治疗的患者（男5例,女8例）,平均年龄（14．4±2．2）岁,使用上颌四眼圈簧扩弓。对患者扩弓前（T1）后（T2）的变化进行 CBCT 扫描,测量扩弓前后两侧尖牙、第一前磨牙、第二前磨牙和第一磨牙之间的牙冠和根尖之间的宽度,第一磨牙的倾斜度,基骨弓和腭中缝宽度的变化。应用 SPSS 17．0软件对测量结果进行配对 t 检验。结果：四眼圈簧扩弓后牙弓变化明显。4对牙的牙间距分别增加了（2．47±1．05）mm、（2．97±1．90）mm、（2．79±1．21）mm、（3．15±1．15）mm,根尖距分别减小了（1．19±0．40）mm、（2．12±0．68）mm、（2．02±0．65）mm、（1．34±0．63）mm,左侧磨牙倾斜度减小了4．45°±2．86°,右侧磨牙倾斜度减小了4．02°±1．45°,基骨弓宽度增加了（2．37±0．96）mm,腭中缝宽度增加了（1．21±0．50）mm,差异均具有统计学意义（P ＜0．001）。结论：四眼圈簧扩弓器对上颌牙弓的扩弓主要通过牙齿倾斜移动完成,而非整体移动。     

A comparison of sagittal and vertical effects between bonded rapid and slow maxillary expansion procedures.

The purpose of this study was to determine the vertical and sagittal effects of bonded rapid maxillary expansion (RME), and bonded slow maxillary expansion (SME) procedures, and to compare these effects between the groups. Subjects with maxillary bilateral crossbites were selected and two treatment groups with 12 patients in each were constructed. The Hyrax screw in the RME treatment group and the spring of the Minne-Expander in the SME treatment group were embedded in the posterior bite planes, which had a thickness of 1 mm. At the end of active treatment these appliances were worn for retention for an additional 3 months. Lateral cephalometric radiographs were taken at the beginning and end of treatment, and at the end of the retention period. The maxilla showed anterior displacement in both groups. The mandible significantly rotated downward and backward only in the RME group. The inter-incisal angle and overjet increased in both groups. No significant differences were observed for the net changes between the two groups.     

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.     

上颌快速扩弓的颅面复合体三维有限元模型的建立

目的建立上颌快速扩弓的颅面复合体三维有限元模型。方法利用螺旋CT扫描获取颅面复合体二维图像原始DICOM数据,结合Mimics10.0、ProE Wildfire 4.0、MSC.Marc.mentat 2005 R3和Geomagic studio10.0软件,建立包含上颌第一前磨牙、第一磨牙及其牙周膜、带环的颅面复合体三维有限元模型。结果所建三维有限元模型单元数达到522 800,具有良好的几何和生物相似性,可以导入到CAD软件中进行处理。结论应用螺旋CT结合Mimics10.0、MSC.Marc.mentat 2005 R3和Geomagic Studio10.0软件建立颅面复合体三维有限元模型的方法是可行和有效的。     

Comparison of nasal volume changes during rapid maxillary expansion using acoustic rhinometry and computed tomography

The purpose of this study was to compare nasal volume changes using acoustic rhinometry (AR) and computed tomography (CT). The subjects were 10 children (6 girls and 4 boys, with an age range of 12-14 years) who required rapid maxillary expansion (RME) on the basis of their individual malocclusion. All patients were found to have normal nasal cavities following anterior rhinoscopic examination. AR and CT were undertaken at the start of treatment (t(1)) and 6 months after expansion (t(2)). Volume changes due to expansion were evaluated using Wilcoxon's test, and the correlation between the two methods was assessed with correlation analyses. Both methods demonstrated that nasal volume significantly increased following the use of RME (P<0.05). Correlation analyses showed no difference in volume (P>0.05) using either of the two methods.     

Effects of a modified acrylic bonded rapid maxillary expansion appliance and vertical chin cap on dentofacial structures

The aim of this study was to determine the sagittal, transverse, and vertical effects of a modified acrylic bonded rapid maxillary expansion (RME) device used with a vertical chin cap on dentofacial structures. The study group consisted of 34 patients (25 girls and 9 boys) who were selected without regard to their skeletal class and gender. All subjects had permanent dentition (mean age, 12.7 years) and needed maxillary expansion. Study Group I (RME only) was composed of 17 subjects, and study Group II (RME with vertical chin cap) was composed of 17 subjects. Twenty-nine measurements were made on the patients' cephalometric films and plaster models. The means and standard deviations for linear and angular cephalometric measurements were analyzed statistically, and intra-group and inter group changes were evaluated by paired and Student's t-tests using SPSS 10.1 for windows. We found that the maxilla moved anteriorly relative to the anterior cranial base. The nasal width, maxillary width, intercanine width, mandibular intermolar width, maxillary intermolar width, and overjet all increased, while the upper molars tipped buccally in both groups. In Group I, the mandible rotated posteriorly, the lower anterior facial height increased, and the overbite decreased. These effects were reduced in Group II. We conclude that the vertical chin cap is an effective appliance for preventing the adverse vertical effects of RME in patients with a crossbite and a vertical growth pattern.     

Effects of face mask treatment with and without rapid maxillary expansion in young adult subjects

Objectives:To investigate the skeletal, dental, and soft tissue effects of the face mask (FM) treatment with and without rapid maxillary expansion (RME) in young adult subjects with maxillary retrognathia.Materials and Methods:Pretreatment and posttreatment cephalometric radiographs from 32 subjects who had a skeletal Class III malocclusion were analyzed. The subjects were divided into two groups: FM group (N  =  17; 3 male and 14 female subjects; mean [SD] age 14.47 [0.89] years) was treated with FM only, while the RME+FM group (N  =  15; 3 male and 12 female subjects; mean [SD] age 14.67 [1.28] years) was treated with both FM and RME. Ten cephalometric linear and nine angular variables were measured to assess dentofacial changes. Within-group and between-group comparisons were determined by a paired t-test and Student''s t-test, respectively.Results:Forward displacement of the maxilla and a clockwise rotation of the mandible occurred in both groups. The maxillary-mandibular relationship improved and soft tissue changes resulted in a more convex profile. The maxillary incisors were more proclined in the FM group than in the RME+FM group, the only difference between the two groups. Notably, the mandibular incisors moved backward in both groups.Conclusions:Forward movement of the maxilla can be obtained in young adults after face mask treatment. However, there was no difference in this phenomenon between the FM and RME+FM groups.     

前方牵引联合快速扩弓矫治不同年龄骨性Ⅲ类错的硬组织变化

目的研究年龄对于前方牵引联合快速扩弓矫治效果的影响。方法将75例3~15岁的骨性Ⅲ类错患儿分成3组,在矫治前、矫治后分别摄X线头颅侧位片,对3组X线片进行头影测量分析,并进行统计学处理。结果3个年龄组矫治后均发生了显著的硬组织变化,且这些硬组织指标在不同年龄组差异有显著性。结论年龄对于前方牵引联合快速扩弓矫治效果有较为明显的影响,矫治后上颌骨以及下颌骨的位置均与年龄有关。     

螺旋CT测量快速扩弓后上颌骨位置三维变化

目的观察快速扩弓(RME)治疗前后上颌骨位置三维方向的变化。方法使用螺旋CT,测量10例恒牙患者RME治疗前后上颌骨各测量点的位置和角度改变。使用配对符号秩检验对比分析各项数据结果。结果RME治疗后上颌骨各测量点均向前、向下移位。代表硬腭的PNS′-ANS连线在正中矢状平面上的投影顺时针旋转0·9°,而代表上颌骨腭突的PNS′-ANS在正中矢状平面上投影的角度变化不明显。冠状平面观,两侧上颌骨下部扩开量较上部大,二者相互向外侧呈楔形倾斜。腭中缝呈前后较小中间稍大的纺锤形扩大。结论RME治疗前后上颌骨位置在矢状向、垂直向和水平向上均发生了相应的改变。应用螺旋CT可以对这种三维位置变化进行详细研究。     

Skeletal changes in vertical and anterior displacement of the maxilla with bonded rapid palatal expansion appliances

The purpose of this study was to determine whether anterior and inferior displacement of the maxilla seen with rapid palatal expansion when done with a banded rapid palatal expansion appliance is significantly different from an occlusally bonded rapid palatal expansion appliance. It was hypothesized that the bonded appliance would limit unwanted displacement of the maxilla by producing vertical forces on both arches in a manner similar to a functional appliance. The study was conducted using the bonded appliance on 20 adolescents and comparing the results with those of a banded appliance population—namely, 60 cases from Wertz's study. Lateral cephalometric radiographs were taken before treatment and again after the expansion appliances were removed. The results of this study suggest that the downward and anterior displacement of the maxilla often associated with the banded rapid palatal expansion appliance may be negated or minimized with the more versatile bonded appliance.