Stress distribution produced by the correction of the mandibular second molar in lingual crossbite

The purpose of this study was to evaluate the stress distribution produced in the dentoalveolar system by a mandibular posterior crossbite appliance used for the correction of mandibular second molars in lingual version. A photoelastic model was fabricated using a photoelastic material (PL-3) to simulate alvelolar bone and ivory-colored resin teeth. The model was observed anteriorly and posteriorly with a circular polariscope and photographically recorded before and after activation of mandibular posterior crossbite appliances. An uncontrolled tipping and an extrusive force were generated when the traction force was applied on the buccal surface of the mandibular second molar. A controlled tipping and an intrusive force were generated when the traction force was applied on the lingual surface of the mandibular second molar. We concluded that to escape the extrusion and uncontrolled tipping that creates occlusal interferences associated with the correction of mandibular second molars in lingual version, the lingual traction force is more useful than the buccal traction force.     

后牙反[牙合]骨性安氏Ⅲ类错[牙合]早期矫治后腭的变化

目的：探讨以乳磨牙为支抗的上腭快速扩大联合前牵引矫治早期骨性Ⅲ类错[牙合]合并后牙反[牙合]畸形患者腭形态的变化。方法：12例替牙早期骨性Ⅲ类错[牙合]合并后牙反[牙合]病例,第一阶段Hyrax支架式上腭快速扩大器扩大2—3周至上颌牙舌尖咬在下颌牙颊尖。第二阶段前牵引至前牙覆盖2～4mm,对矫治前后模型进行腭形态测量。结果：腭底宽增加1．98mm±0．97mm,磨牙距增加5．04mm±1．30mm,腭底宽增加量／磨牙距的增加量为41％,上颌牙槽突夹角增加8．57°±4．05°,左磨牙的倾斜角颊倾8．99°±4．06°,右磨牙的倾斜角颊倾8．34°±3．94°,变化均有显著性差异。腭深度改变无显著性差异。结论：上腭快速扩大联合前牵引是矫治替牙早期骨性Ⅲ类错[牙合]合并后牙反[牙合]畸形的较好方法,腭底宽、磨牙距、上颌牙槽突夹角、磨牙倾斜角的增加均有显著性差异。腭的明显变化使畸形的上腭趋向正常。     

Tomas微种植体矫治力系统竖直倾斜磨牙的三维有限元研究

目的 探讨微种植体复合矫治力系统竖直倾斜磨牙的影响.方法 对上颌第二恒磨牙向近中、颊侧倾斜的干燥头颅骨进行多层螺旋CT扫描,利用有限元软件建立上颌第二恒磨牙及其牙周支持组织的三维有限元模型,并观察计算机模拟微种植体位于不同位置、施加不同的远中向力和根颊向力偶矩时磨牙牙周膜的位移.结果 当微种植体位于第二恒磨牙近中颊侧牙槽骨,进行力学加载时,磨牙产生向远中倾斜、腭侧旋转的趋势;位于近中(牙合)面和近中腭侧牙槽骨,进行力学加载时,磨牙均产生向远中倾斜、颊侧旋转的趋势.结论 合理运用复合矫治力系统可以更有效地竖直倾斜磨牙.     

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锁[牙合]可发生于单侧或双侧,分为正锁[牙合]和反锁牙合。处于游离端位置的第二磨牙区锁[牙合]的矫治一直是正畸治疗中的一个难点。本文主要介绍了利用微小种植体支抗腭移或颊移上颌后牙,颊移下颌后牙解决第二磨牙区正、反锁[牙合]的方法,并对如何解决矫治中会出现的锁[牙合]伴上下后牙近中倾斜、拥挤的情况进行了详细描述。     

A jointed fan-type expander: a newly designed expansion appliance for the upper dental arch of patients with cleft lip and/or palate

Most patients with repaired cleft lip and/or palate have malocclusion and show various forms of occlusal discrepancy between the upper and lower dentition. In unilateral clefts, the teeth in the collapsed small segment are usually in lingual crossbite, although in most cases they are in normal buccolingual occlusal relation in the molar region. Expansion appliances should fulfill the following functions: the application of expansion force to the alveolar bone of the maxillary complex without buccal tipping of the teeth (to obtain the differential segmental movement); force to the lateral segments of the maxilla without their distortion; and expansion of the smaller segment without creating posterior crossbite. Unfortunately, many appliances do not satisfy these functions. A new fan-type expansion appliance has been designed by the authors to solve these problems. This appliance consists of three parts, as follow: an expansion screw; four bands (anchorage); and a joint connecting both buccal segments. The expansion screw is set in a direction tangent to the curve drawn by the intended fan-type movement of the collapsed small segment. The joint converts the expansion force from parallel to an arched direction.     

The goshgarian transpalatal bar: A clinicaland an experimental investigation

The Goshgarian transpalatal bar is a fixed appliance that can be used inthe treatment of Class II malocclusions. This study examines the effects of the appliance on the maxillary molars and determines the force-activation characteristics of the appliance with a laboratory model. The pretreatment and posttreatment cephalometric films and dental cast records of 11 patients with Class II malocclusions are evaluated. Results show that Class II correction is achieved as a result of distobuccal rotation and distal tipping of the activated molar. A potential negative side effect on the nonactivated molar is a slight mesial movement. Both intermolar and interbicuspid widths were substantially increased with buccal root torquing. Intrusion and extrusion of the molars did not occur. The distal and transverse forces generated by the Goshgarian palatal bar were linear, however, when distal activation exceeded 35°, the appliance became plastic. Transverse forces were twice as great as with a quad helix and distal forces were one fourth to one eighth of those generated with a headgear.     

第二磨牙锁He与牙弓后部拥挤

目的选择第二磨牙锁的成年患者,通过对其Ｘ线头颅侧位片的测量,与正常进行比较,对第二磨牙锁的病因做初步分析,为今后的临床治疗工作提供参考。方法分别测量正常和后牙锁患者的头颅侧位片,测量上颌第一磨牙远中最突点在颅底平面的投影和翼上颌裂点在前颅底平面的投影两者之间的距离,测量数据进行ｔ检验。结果第二磨牙锁患者上颌第一磨牙到上颌骨后壁的距离明显小于正常。结论第二磨牙锁与后部牙弓间隙不足密切相关,分析牙列拥挤度时,还应考虑后牙段间隙问题,尤其是推磨牙向后的病例,如果预测后牙段有拥挤的可能,应尽早拔除第三磨牙。     

A comparison of dental and dentoalveolar changes between rapid palatal expansion and nickel-titanium palatal expansion appliances.

A tandem-loop nickel titanium temperature-activated palatal expansion appliance was developed that produces light, continuous pressure on the midpalatal suture and requires little patient cooperation or laboratory work. The purpose of this study was to compare the effectiveness of the nickel titanium palatal expansion appliance with that of a rapid palatal expansion appliance. The study sample comprised 25 patients who required palatal expansion as part of their orthodontic treatment. The sample was divided into 2 groups, with 13 patients in the nickel titanium group and 12 patients in the rapid palatal expansion group. Study models were taken before treatment and at the end of the retention period after expansion. Intermolar width, palatal width, palatal depth, alveolar tipping, molar tipping, and molar rotation were analyzed. In addition, occlusal radiographs were obtained before and 2 weeks after expansion to evaluate for sutural separation by the appliances. Results showed significant increases in midpalatal sutural separation, tipping of the alveolus, and tipping of the molars after expansion in both groups. However, greater midpalatal sutural separation was found in the rapid palatal expansion group and greater molar rotation was found in the nickel titanium group. Stepwise multiple regression analysis showed that alveolar tipping, palatal width change, and molar tipping are the best predictors of intermolar width change in the rapid palatal expansion group. Radiographic evidence of midpalatal sutural separation was less obvious in the nickel titanium group. These results suggest that both the nickel titanium and the rapid palatal expansion appliances are capable of expanding the maxillary dentition and alveolar process and are equally capable of correcting posterior crossbites. In the current study, the rapid palatal expander widened the palate more reliably, whereas the nickel titanium expander tipped the molars buccally to a greater extent and caused more distal molar rotation. The clinician's choice of expander will depend on his or her initial diagnosis and treatment goals.     

Skeletal and dentoalveolar changes in the transverse dimension using microimplant-assisted rapid palatal expansion (MARPE) appliances

Conventional rapid palatal expansion (RPE) has been proven to be a reliable treatment for correcting transverse maxillary deficiency in young patients. However, side effects including dental tipping and risk of periodontal problem limited its application to young patients after the pubertal growth spurt. Surgically assisted rapid palatal expansion (SARPE), a supplement to RPE, could be applied in skeletally mature patients. However, SARPE was an invasive method, and the morbidity, risks and cost related to surgical treatment might discourage many adult patients. The use of Microimplant-Assisted Rapid Palatal Expansion (MARPE) appliance, which can potentially avoid surgical intervention, is gaining popularity in treatment of maxillary transverse deficiency (MTD) in young adolescent patients. However, the literature on the skeletal and dentoalveolar changes with this appliance is scarce. To evaluate the immediate skeletal and dentoalveolar changes in the transverse dimension with the maxillary skeletal expander (MSE), a MARPE appliance with hybrid anchorage, using cone-beam computed tomography (CBCT). Twenty-two patients (11 males and 11 females, mean age 14.97 ± 6.16 years) with transverse maxillary deficiency were treated using the MSE (Biomaterials Korea, Inc., Seoul, Korea). The appliance consisted of a central expansion screw that were welded to four tubes that served as guides for microimplant placement. The microimplants were 1.8 mm in diameter and 11 mm in length. The longer length of microimplants permitted bicortical engagement of the palatal and nasal floor, reducing the force transmitted to the anchored teeth during expansion. The appliance activation varied with age and skeletal maturity of the patient. The expansion was terminated when 2–3 mm of overexpansion was achieved. CBCT scans were taken before treatment (T1) and immediately after expansion (T2). Measurements were taken to evaluate the amount of total expansion, skeletal expansion, and angular dental tipping at the first molar region. A total expansion of 5.41 ± 2.18 mm was achieved, 59.23 ± 17.75% of which was attributed to skeletal expansion (3.15 ± 1.64 mm) with the first molars exhibiting buccal tipping of 2.56 ± 2.64°. The use of MARPE appliances such as MSE can be used to correct transverse maxillary deficiency in adolescent patients with minimal dentoalveolar side effects.     

Rapid maxillary expansion--tooth tissue-borne versus tooth-borne expanders: a computed tomography evaluation of dentoskeletal effects

This study evaluated rapid maxillary expansion (RME) dentoskeletal effects by means of computed tomography (CT), comparing tooth tissue-borne and tooth-borne expanders. The sample comprised eight girls aged 11 to 14 years presenting Class I or II malocclusions with posterior unilateral or bilateral crossbite that were randomly divided into two treatment groups, palatal acrylic (Haas-type) and hygienic (Hyrax) expanders. All appliances were activated up to the full seven mm capacity of the expansion screw. The patients were subjected to a spiral CT scan before expansion and after a three-month retention period when the expander was removed. One-millimeter-thick axial sections were scanned parallel to the palatal plane, comprising the dentoalveolar area and the base of the maxilla up to the inferior third of the nasal cavity. Multiplanar reconstruction was used to measure maxillary transverse dimensions and posterior teeth inclination by means of a computerized method. The results showed that RME produced a significant increase in all measured transverse linear dimensions, decreasing in magnitude from dental arch to basal bone. The transverse increase at the level of the nasal floor corresponded to one-third of the amount of screw activation. Tooth-borne (Hyrax) and tooth tissue-borne (Haas-type) expanders tended to produce similar orthopedic effects. In both methods, RME led to buccal movement of the maxillary posterior teeth, by tipping and bodily translation. The second premolars displayed more buccal tipping than the appliance-supporting teeth. The tooth tissue-borne expander produced a greater change in the axial inclination of appliance-supporting teeth, especially first premolars, compared with the tooth-borne expander.     

Posterior transpalatal distraction with pterygoid disjunction: a short-term model study.

The transpalatal distractor (TPD) allows for maxillary expansion according to the concepts of distraction osteogenesis. Unlike tooth-borne, surgically assisted rapid palatal expansion devices, the bone-borne TPD is designed to avoid periodontal ligament compression, buccal root resorption, fenestration, tooth tipping, and orthodontic relapse during and after the expansion. When the distractor is placed on the palate at the level of the second premolar and pterygomaxillary disjunction is not performed, more expansion occurs in the anterior part of the maxilla than it does in the posterior. The aim of this investigation was to test the hypothesis that pterygomaxillary disjunction and placement of the TPD on the palate at the level of the first molars result in more parallel expansion of the maxillary segments. Twenty consecutive patients were included in a prospective way, and their predistraction and postdistraction models were electronically analyzed. The change in resistance and force application resulted, on average, in parallel segment expansion. The results showed that pterygomaxillary disjunction and posterior placement of the TPD are indicated for patients having transverse maxillary deficiency with lateroposterior crossbite.     

Dentoskeletal effects of a temporary skeletal anchorage device–supported rapid maxillary expansion appliance (TSADRME): A pilot study

Objective:To quantitatively evaluate maxillary skeletal expansion using cone-beam computed tomography (CBCT) images and propose a novel way to quantify the dental tipping effects of temporary skeletal anchorage device–supported rapid maxillary expansion appliance (TSADRME).Materials and Methods:Images from 25 patients receiving rapid maxillary expansion with incorporated temporary skeletal anchorage devices (TSADs) before activation (T1) and after removal (T2) were analyzed to detect dentoskeletal changes.Results:A significant increase from T1 to T2 was found for all linear measurements except buccal maxillary width at the canines. The greatest buccal expansion was at the first molar, decreasing anteriorly. However, the greatest palatal expansion was at the first premolar. All younger subjects (8–16 years old) exhibited less dental tipping and greater expansion overall compared with the older subjects. There was great variability in dental tipping of first molars (mean = 4.31°), with some subjects demonstrating mild uprighting of these teeth.Conclusions:The TSADRME appliance is an effective, clinically useful device that results in mild molar tipping and may positively affect expansion in the area of TSAD placement.     

The effects of orthopedic forces on the craniofacial complex utilizing cervical and headgear appliances.

1. A three-dimensional anatomic model of a human skull was produced with birefringent materials for photoelastic analysis. By means of photoelastic techniques during application of high-pull and cervical extraoral traction, stresses were visualized within the model. 2. Extraoral anchorage affected the position of the maxillary molar and its resulting alveolar development. Cervical headgear had a much greater tipping effect on the maxillary molar than did the high-pull headgear. Both appliances examined could produce stresses which may be transmitted to distant eraniofacial sutures. As opposed to high-pull traction, cervical pull in general stressed more areas and to a much greater degree. 4. The pterygoid plates of the sphenoid bone, the zygomatic arches, the junction of the maxilla with the lacrimal bone and the ethmoid, and the maxillary teeth were affected by both types of headgear. 5. Only cervical traction produced stresses at the frontal process of the maxilla and the Zygomaticofrontal suture. 6. There were two findings which had not been previously reported: First, cervical traction tended to open the palate in the posterior region. Second, high-pull traction produced compressive stresses at the junction of the right and left maxillae inferior to the anterior nasal spine.     

内收前牙时微种植钉调控牙合平面的有限元分析

目的:探讨内收上前牙过程中,前牙区不同大小压低力对上颌平面变化的影响.方法:应用CBCT扫描、MIMICS以及ANSYS等软件建立微种植钉内收前牙的三维有限元模型,设置前牙区分别为0、0.5、0.75、1 N的压低力,计算分析前后牙的位移趋势以及平面的变化.结果:单纯的内收力使上前牙舌倾、第一磨牙远中倾斜、上颌平面顺时针旋转.随着前牙区压低力增大,上前牙舌倾程度降低,接近整体移动,第一磨牙远中倾斜移动的趋势减小,平面顺时针旋转的情况得以抑制.结论:通过改变前牙区压低力的大小,可以有效地改变上颌前牙的移动方式及平面的旋转;在内收前牙时增加0.5~0.75 N压低力,更有利于防止上颌平面的顺时针旋转.     

Dimensional changes in the palate associated with slow maxillary expansion for early treatment of posterior crossbite

Objectives:To compare palatal symmetry, dimensions, and molar angulations following early mixed-dentition slow maxillary expansion with parameters in normal controls.Materials and Methods:A total of 30 patients treated with a Haas-type expander for unilateral posterior crossbite with functional shift were compared with 30 controls matched for dental age, gender, and molar relationship. Records were taken before (T1) and after expansion (T2). Palatal width, surface area, volume, and molar angulations were measured on digitized models. Surface area and volume were split in half then divided into anterior, middle, and posterior segments to measure symmetry. Student''s t-test was used to assess group differences.Results:Mean intercanine width increased 4.65 mm, and intermolar width increased 4.76 mm. The treated mean surface area increased 127.05 mm² compared with 10.35 mm² in controls. The treated palatal volume increased 927.55 mm³ compared with 159.89 mm³ for controls. At T1, the controls showed significant differences in surface area and volume between the anterior palatal segments. At T2, this difference occurred in surface area of middle palatal segments of the treated sample. First permanent molars showed an increased buccal and distal inclination after treatment, opposite to controls. The increase in buccal inclination was greater on the crossbite side.Conclusions:The Haas-type expander results in similar expansion across the canines and first molars. A palate that is symmetrical before expansion may become asymmetric after expansion but only in the middle segment. Changes in individual molar angulation following palatal expansion can be measured without radiation imaging.     

A comparison of different treatment techniques for posterior crossbite in the mixed dentition.

In this retrospective investigation, the changes occurring during the treatment of patients with posterior crossbite in the mixed dentition with the use of expansion plate and quad-helix appliances were evaluated and compared with those resulting from growth and development occurring in a control group of patients of similar age and type of malocclusion. The expansion plate group consisted of 13 patients, the quad-helix group of 14 patients, and the control group consisted of 10 children with transverse posterior crossbites in the mixed dentition. The research material was formed from orthodontic models and lateral and frontal cephalometric radiographs from 37 children. It was observed in this investigation that transverse expansion is achieved by both the expansion plate and quad-helix appliances. However, the average period of treatment was 1.2 years for the expansion plate, and 0.6 years for the quad-helix appliance. Although posterior crossbite was corrected in a fairly short period of time, the quad helix appliance caused considerable buccal tipping of the maxillary first permanent molars.     

传统与改良Hyrax扩弓器对牙弓、牙槽骨、基骨影响的CBCT对比研究

目的应用CBCT比较传统Hyrax扩弓器与改良Hyrax扩弓器对牙弓、牙槽骨及基骨的影响。方法将30例上颌牙弓狭窄的患者随机分为2组,传统Hyrax扩弓器组15例患者,8男7女,平均年龄(14.1±2.5)岁,改良Hyrax扩弓器组15例患者,9男6女,平均年龄(13.9±2.6)岁。收集2组患者扩弓前及扩弓3个月后的CBCT扫描数据,重建三维影像并测量牙弓、牙槽骨及基骨的相应指标,应用配对样本的t检验分析2组扩弓后测量指标的变化,应用独立样本的t检验分析2组测量指标之间的差异。结果 2组都存在基骨的改变及牙弓宽度的增加,2组之间的比较显示传统Hyrax组的第一、二前磨牙牙弓宽度大于改良Hyrax组,第一磨牙颊侧及腭侧牙槽骨厚度的变化2组并无统计学的差异,而第一前磨牙颊侧及腭侧牙槽骨的厚度变化2组有统计学差异,此外,2组之间绝对牙倾斜度比较也并无统计学差异。结论两种快速扩弓方法对于纠正上颌牙弓狭窄都有较为明显的效果,传统Hyrax扩弓器对第一前磨牙牙弓宽度及颊腭侧牙槽骨厚度的影响更大。     

腭中缝微种植钉联合铸造支架前移上磨牙的临床效果评价

目的: 研究微种植钉和铸造支架直接牵引上颌第二、第三磨牙前移关闭上颌第一磨牙缺隙的临床疗效。方法: 选择12例上颌第一磨牙缺失,且只接受局部正畸治疗的患者为研究对象。在腭中缝两侧植入微种植支抗钉2颗,制作铸造支架,稳定连接上颌同侧前磨牙和微种植钉。设计力线接近阻抗中心,颊舌侧加力牵引磨牙近中移动,关闭间隙。采用Graphpad Prism 6.0 软件包对所得数据进行配对t检验。结果: 所有间隙均顺利关闭,磨牙近中平均移动5.7 mm,磨牙轴倾度基本正常,牙周状况良好,其余牙保持原有咬合关系。结论: 利用微种植钉和铸造支架可以有效牵引上颌第二、第三磨牙近中移动,关闭上颌第一磨牙缺隙。     

A comparison of dentoalveolar inclination treated by two palatal expanders

The objective of the present study was to evaluate buccal dentoalveolar inclinations in subjects treated with a Hyrax (tooth-borne) or acrylic-bonded (tooth-tissue borne) palatal expander. The sample comprised 39 patients (10 males and 29 females) aged between 11 and 16 years randomly assigned to two groups. Rapid maxillary expansion (RME) was carried out with a Hyrax appliance in one group (n = 21) and with an acrylic-bonded appliance in the other (n = 18). Their mean ages were 13 years 9 months and 13 years 6 months, respectively. Orthodontic study models were obtained before RME (T1) and approximately 1 week after completion of maxillary expansion (T2). A line of barium sulphate solution was drawn between the upper first molars on the models, and radiographs were taken. The radiographic images of the models were transferred to digital medium, and buccal tipping of the molar crowns and alveolar processes were evaluated by means of a software program. The data were analysed by paired and Student's t-tests. Both RME appliances produced significant (P < 0.001) dentoalveolar tipping during RME, but this was greater in the Hyrax group (P < 0.05).     

Dental tipping and rotation immediately after surgically assisted rapid palatal expansion

The purpose of this investigation was to evaluate the effects of dental tipping and rotation immediately after surgically assisted rapid palatal expansion (SARPE). Fourteen patients (10 females, four males; mean age 25.6 years) who required a SARPE procedure were available for this study. A palatal expander appliance was cemented on four abutment teeth (first premolars and first molars) of each patient 1 week prior to surgery. Maxillary study models were taken before surgery and 2-3 weeks after full expansion (7 mm). Each model was trimmed to have the base parallel to its occlusal plane. From an occlusal view, measurements were made to determine if the abutment teeth underwent rotation from SARPE. From a postero-anterior view, the abutment teeth were examined for any tipping effect due to SARPE. The results showed that from pre- to post-expansion, the two first premolars displayed 2.32 +/- 8.29 degrees of mesiobuccal rotation (P > 0.05) and the two first molars displayed 3.09 +/- 5.89 degrees of mesiobuccal rotation (P > 0.05). Each first premolar showed 6.48 +/- 2.29 degrees of buccal tipping (P < 0.05) and each first molar 7.04 +/- 4.58 degrees of buccal tipping (P < 0.05). SARPE induced a slight mesiobuccal rotation (P > 0.05) and significant buccal tipping of the first premolars and the first molars (P < 0.05). Some overexpansion is suggested to counteract the relapse effect of buccal tipping of the posterior teeth that takes place during SARPE.