The retraction of upper incisors with the PG retraction system

The aim of this study was to evaluate the effect on the dentoalveolar structures of the application of PG springs for retraction of upper incisors and to compare the outcome with the effect of a closed coil spring retraction system. Thirty-six subjects with Angle Class I or Class II malocclusions were selected for the study. Each subject had the two upper first premolars extracted and presented a symmetrical extraction space of at least 3 mm distal to the lateral incisors after canine retraction. The subjects were divided into two groups, the PG group with 17 subjects and the coil group with 19 patients. One group had the incisors retracted by PG universal retraction springs, whereas in the other a closed coil spring system was used. The average chronological ages were 18 years 4 months for the PG group, and 18 years 7 months for the coil group. In both groups the springs were activated to produce an initial force of 150 g per side. To examine the type of movement of the anterior and posterior teeth, and the time and rate of space closure, 20 parameters were measured and evaluated statistically with Wilcoxon and Mann-Whitney U-tests. In both groups the incisor retraction was accompanied by mesial movement of the buccal segments. Distal movement of the root apex of the incisors was observed in both groups, although more pronounced in the PG group (P < 0.01). A significant incisor intrusion resulting in a decrease in overbite was found in the PG group, whereas the deep bite increased significantly in the coil spring group. The PG spring produced a three-dimensional control in the movement of the upper incisors, so that application of additional intrusive mechanics after completion of the incisor retraction became unnecessary.     

Severe Class II anterior deep bite malocclusion treated with a C-lingual retractor

A C-lingual retractor was placed on the lingual aspects of the six maxillary anterior teeth in a 24-year-old female patient with a Class II anterior deep-bite malocclusion. The treatment plan consisted of extracting both the upper first premolars and intruding and retracting the upper six anterior teeth. Transpalatal arches were soldered to the upper first and second molar bands and used as an intra-arch anchor unit for upper space closure. Double NiTi closed coil springs were used palatally between the hooks of the C-lingual retractor and the transplantar arches. A high-pull headgear was used for anchorage reinforcement during en masse retraction. It took 14 months to treat this patient. The correct overbite and overjet was obtained by simultaneously intruding and retracting the upper six anterior teeth into their proper positions by C-lingual retractor mechanics, which contributed to an improvement in facial balance. The treatment result was stable 6 months after debonding. The application of this new appliance, consideration in case selection, and sequence of treatment are presented.     

Comprehensive comparison of canine retraction using NiTi closed coil springs vs elastomeric chains:: A split-mouth randomized controlled trial

ObjectivesTo compare canine retraction using NiTi closed coil springs vs elastomeric chains comprehensively in a split-mouth randomized controlled trial.Materials and MethodsThe canines in 64 quadrants were randomly retracted into the first premolar extraction spaces using NiTi closed coil springs or elastomeric chains, in the maxilla and mandible. The retraction force was 150 g. Cone beam computed tomography scans and study models were obtained before the start of canine retraction and 6 months later. The rate and total amount of canine retraction, canine rotation, tipping, and root resorption were evaluated. A visual analogue scale was used to evaluate patients'' pain experience.ResultsThe two methods were statistically similar for dental changes, rate of canine retraction, and root resorption. However, patients reported significantly more days of pain with the elastomeric chain compared to the NiTi closed coil springs.ConclusionsWithin the constraints of the current study, using either NiTi closed coil springs or elastomeric chains as force delivery systems for canine retraction results in no significant difference in the rate of canine retraction, tipping, rotation, or root resorption. Pain experience during retraction using elastomeric chains is more significant yet needs further investigation.     

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目的采用三维有限元法模拟不同方向牵引力内收上前牙,分析前牙位移趋势及应力分布,为临床治疗提供指导。方法研究于2012年在福建医科大学进行。建立唇侧直丝弓矫治器、6个上前牙及其牙周膜和前颌骨的三维有限元模型。模拟在0.48 mm×0.64 mm英寸主弓丝上,以种植钉为支抗、1.47 N矫治力整体内收上前牙,设定前牙区牵引钩为0-6 mm、后牙区种植钉高度分别为8和14 mm。加载后求解,计算出各前牙的位移及牙周膜第一主应力。结果滑动法整体内收上前牙时,牵引钩长度主要影响前牙的矢状向位移方式：牵引钩长度增加至6 mm的过程中,侧切牙在唇舌向上由舌向倾斜运动变为舌向整体平移和舌向控根运动外,中切牙和尖牙的三维位移只有数量的增大,趋势基本保持不变。支抗种植钉高度主要影响前牙垂直向位移：种植钉位置越高,侧切牙的压低位移增大,尖牙的伸长位移减小,即前牙整体压低的趋势更明显。结论种植支抗整体内收前牙时,单纯调整牵引钩长度和支抗种植钉高度难以实现前牙段的整体内收,有必要对前牙段增加适当的垂直向压低力量。     

上颌切牙内收前后牙根及牙槽骨的变化

目的 通过锥形束CT（CBCT）测量并分析上颌前突患者上颌切牙内收治疗前后牙根及牙槽骨的变化。方法 选取2014年1月—2015年12月完成的正畸病例37例,其中男性17例,女性20例,平均14.5岁。所有患者拔除上颌双侧第一前磨牙且使用种植钉强支抗内收上颌切牙,通过头影测量获取上颌切牙内收角度、内收量及伸长量,使用NewTom NNT软件对CBCT数据进行多平面重建,调整冠状、轴向与矢状轴,选取通过切缘和根尖的牙齿长轴最长的矢状截面测量上颌切牙内收治疗前后牙根及牙槽骨的变化。结果 上颌前牙内收治疗前后,中切牙内收角度为12.92°±6.43°,内收量为（5.54±2.21） mm,伸长量为（0.60±0.95） mm,牙根吸收长度为（0.81±0.46） mm,牙根吸收率为6.80%±3.60%,切牙内收治疗前后牙根长度变化具有统计学差异（P<0.05）,治疗后唇侧牙槽骨高度降低量为（0.20±0.22）mm,治疗前后差异有统计学意义（P<0.05）。牙根吸收率与上颌中切牙切端的水平向位移及根尖至唇侧皮质骨的距离具有相关性;唇侧牙槽骨高度变化量与上颌切牙内收角度的相关系数为0.354,具有统计学意义（P<0.05）。结论 上颌前突患者代偿性治疗后,上颌切牙产生了明显的牙根吸收,唇侧牙槽骨高度降低。牙齿移动量越大,或超出了牙槽骨的解剖限制和改建限度,容易导致牙根吸收。唇侧牙槽骨高度变化量与切牙内收角度呈负相关。     

口外颈牵引装置早期矫治安氏Ⅱ类1分类错的疗效研究

目的 评价口外颈牵引装置对生长发育期的安氏Ⅱ类1分类错(牙合)患者的疗效。方法 采用侧位X线头影测量,对15例患者进行观察分析。结果 上颌骨向前生长受到抑制,下颌骨生长得到充分表达,上下颌骨矢状不调得以改善。上颌第一恒磨牙伸长并向远中移动,上颌切牙唇倾角度减小,第一恒磨牙关系恢复至中性(牙合),覆(牙合)、覆盖有不同程度的减小。同时发现,腭平面角、(牙合)平面角、下颌平面角均无显著性变化。结论 口外颈牵引装置对生长发育期安氏Ⅱ类1分类错(牙合)有明显的矫形效果。     

Ⅱ类1分类错[牙合]正畸治疗前后牙齿移动与软组织侧貌变化的线性相关分析

目的通过对Ⅱ类1分类错[牙合]患者正畸治疗前后的头影测量指标进行相关性分析,探讨影响面部软组织侧貌变化的相关因素。方法选取2012年6月至2017年11月于上海交通大学医学院附属第九人民医院口腔颅颌面科就诊的42例已完成正畸治疗的Ⅱ类1分类错[牙合]患者[男性10例,女性32例,年龄(23.8±6.3)岁,平均矫治时间1.9年],拔除4颗第一前磨牙或2颗上颌第一前磨牙后进行正畸治疗纠正磨牙关系,测量矫治前后硬组织及软组织相关头影测量指标30个,包括上下唇突点、颏唇沟点、软硬组织颏前点及颏顶点的矢状向及垂直向距离、鼻唇角及颏唇角等。对矫治前后各指标变化量进行线性回归分析,根据标准化回归系数(Beta)分析影响上下唇、鼻唇角、颏唇角等面部软组织的主要相关因素。结果30个头影测量指标中18个矫治前后差异均有统计学意义(P<0.05),与矫治前相比,矫治后上中切牙点矢状向距离[(63.87±7.14)mm]、上唇突点矢状向距离[(77.73±7.60)mm]显著减小(P<0.05)。14对头影测量指标变化量间存在线性关系,其中上唇突点矢状向变化量与上中切牙点矢状向变化量强正相关(r=0.649,P<0.01),上唇突点垂直向变化量与上中切牙点垂直向变化量中度正相关(r=0.544,P<0.01),软组织颏顶点矢状向变化量与Y轴角变化量中度负相关(r=0.537,P<0.01)。多元逐步后退回归分析显示,上唇突点内收量与上中切牙点内收量、平面角增大量以及上中切牙角增大量均相关,且与上中切牙点内收量相关性最大(Beta=0.79);上唇突点下移量与上中切牙点下移量、上中切牙角减小量、上颌第一磨牙面中点到腭平面距离减小量以及平面角增大量相关,且与上中切牙点下移量及平面角增大量的相关性最大(Beta均为0.59);下唇突点下移量与上、下中切牙点下移量相关,且与上中切牙点下移量相关性更大(Beta=0.36)。结论Ⅱ类1分类错[牙合]矫治后鼻唇颏关系得到一定改善,切牙的矢状向变化对唇突度的影响最大,且下唇矢状向与垂直向移动与上中切牙的位置关系更密切,牙齿移动对颏部的影响有限。     

种植体支抗内收上颌全牙列的三维有限元分析

目的:研究在种植体支抗内收全牙列的过程中,不同的牵引钩高度对上颌全牙列的生物力学效应和影响。方法:运用螺旋CT,MIMICS、CADTIA和SOLIDWORKS软件,建立微种植体支抗内收全牙列的三维有限元模型,并计算在3 N正畸力负载下上颌全牙列在牵引钩高度为1、4、7、10 mm时的受力大小和初始位移。结果:随着牵引钩高度的增加,矢状向力逐渐增加而垂直向力逐渐减小,上牙列逐渐由顺时针变为逆时针方向旋转。结论:通过改变牵引钩的高度,可以有效地改变上牙列的移动方式;上牙列的阻抗中心的高度位于平面上方9～12 mm之间。     

Displacement and stress distribution in the temporomandibular joint during clenching.

The aim of this study was to analyze biomechanical reactions in the mandible and TMJ during clenching under various restraint conditions. A three-dimensional finite element model of the mandible, including the TMJ, was created for test purposes. The results were as follows: (1) Under any restraint conditions, displacement was greatest on the surface of the condyle and less on the articular disc and the surface of the glenoid fossa, in that order. Resultant stresses followed the same trend. (2) Displacement and stress were greatest when the lower central incisor was restrained and attenuated as the posterior teeth were restrained. Because the biomechanical reaction of the TMJ during clenching was greatest when the lower central incisor was restrained, premature contact of these teeth may be one of the factors involved in the initiation of temporomandibular arthrosis.     

Effects of pulsed electromagnetic field vibration on tooth movement induced by magnetic and mechanical forces: a preliminary study

BACKGROUND: This study was designed to determine whether or not high-frequency and low-magnitude vibration affects orthodontic tooth movement caused by magnetic or/and mechanical forces. METHODS: Forty-four 7-week-old Wistar rats were randomly divided into four groups, with each group further divided into experimental and control subgroups. Neodymium-Iron-Boron (Nd-Fe-B) magnets and Sentalloy closed coil springs were placed between maxillary or mandibular first molars and incisors to activate tooth movement. The animals of experimental subgroups were exposed to the vibration induced by pulsed electromagnetic fields (PEMF) whilst the control subgroups were under normal atmosphere. The experiment lasted for 14 days and all of the animals were sacrificed for examination. The changes in the space between the molar and incisor were measured to indicate the amount of tooth movement. RESULTS: The coil springs, either with sham or active magnets, move molar much more than magnets alone, regardless of absence or presence of PEMF (p < 0.001). Under PEMF, the coil spring moved significantly more amount of tooth movement than that of coil-magnet combination (p < 0.01), as did the magnets compared to sham magnets (p < 0.019). Under a non-PEMF scenario, there was no significant difference in tooth movement between coil spring and coil-magnets combination, nor was there difference between magnets and sham magnets. CONCLUSIONS: It is suggested that the PEMF-induced vibration may enhance the effect of mechanical and magnetic forces on tooth movement.     

影响双颌前突青少年患者唇部内收因素的研究

目的 探讨影响双颌前突青少年患者正畸治疗后唇部内收的因素.方法 对满足纳入标准的37例双颌前突青少年患者进行治疗前后的X线头影测量分析.测量治疗前软组织、硬组织、牙体组织项目及治疗后软硬组织变化项目共27项,应用多元线性回归（后退法）筛选影响唇部变化的敏感因素.结果 治疗后上中切牙颈缘点矢状向变化,治疗前年龄,上唇缘点至E线距离和颏部厚度影响上唇缘点矢状向内收变化,回归方程相关系数为0.875;治疗后下中切牙切缘矢状向变化,治疗前下唇缘点至E线距离,下唇紧张度,颏唇角和颏部厚度影响下唇缘点矢状向变化,回归方程相关系数为0.887.结论 治疗前生长潜力、骨性、牙性、软组织特点,及治疗后牙性变化影响双颌前突患者唇部内收变化.     

Iatrogenic TMJ difficulty: cervical traction may be the etiology.

Patients in cervical traction for the treatment of cervical spine syndromes frequently complain that the traction makes them worse. It is possible that such patients may be suffering from TMJ symptoms. The physician treating a patient with cervical traction should consider prescribing an occlusal splint for patients without posterior teeth. The splint should be designed to distribute the stresses through the mandible to the maxillae via the teeth, splint, and TMJ.     

Neuromuscular objectives of the human masticatory apparatus during static biting

OBJECTIVE: The central nervous system controls the muscles of mastication and may dictate muscle outputs according to a biologically important objective. This study tested the hypotheses that (a) the effective sagittal TMJ eminence morphology, and (b) the outputs of the masticatory muscles during static biting, are consistent with minimisation of joint loads or minimisation of muscle effort. DESIGN: Numerical modelling predicted effective eminence morphology (from sagittal plane directions of TMJ force for centred loading over a range from molar to incisor biting) and TMJ and muscle forces during static unilateral biting in seven subjects. In vivo effective eminence morphology was measured from jaw tracking recorded from each subject. Muscle activities during biting tasks on first molar and incisor teeth were measured by electromyography using surface or indwelling electrodes. RESULTS: Subject-specific predicted effective eminence morphology correlated with in vivo data (0.85< or =R2< or =0.99). Mixed and random coefficient analysis of covariance indicated good agreement between predicted and measured muscle outputs for all muscles of mastication investigated. Individual linear regression analysis showed that modelled muscle outputs accurately predicted EMG data, with average errors of 8% for molar and 15% for incisor biting. CONCLUSIONS: Effective sagittal eminence morphology was consistent with minimisation of joint loads for all subjects. Masticatory muscle outputs during unilateral biting were consistent with minimisation of joint loads or minimisation of muscle effort, or both, depending on the subject. These results are believed to be the first to test model predictions of muscle output during biting for all muscles of mastication.     

前牵引颏部反作用力对颞下颌关节应力及位移的影响

目的 建立颅颌面骨的三维有限元模型,分析前方施加反作用力牵引颏部对颞下颌关节应力及位移产生的影响。方法 以健康成年男性作为研究对象,采集螺旋CT原始图像数据,利用Mimics、MSC、Magics、Marc图像处理软件建立三维有限元模型,在颏部施加大小为5 N的作用力,并改变施力方向,测定颞下颌关节及颌骨的应力及位移变化情况。结果 三维有限元模型包括上颌骨、下颌骨、颞下颌关节、颅骨,共包括颅骨三维有限元模型节点28760个和110790个单元,上颌骨20487个节点、76982个单元,下颌骨8273个节点、33080个单元。施加载荷为5 N时,方向与平面呈37°时,上颌骨20487个节点的等效Mises应力值为0.143 N,下颌骨8273个节点的等效Mises应力值为0.111N,髁突头部14305个节点的等效Mises应力值为0.829 N。施加载荷为5 N时,颞下颌关节位移从颏部至髁突部位逐渐递减,位移方向与载荷施加方向一致。颏部位移最大,约为0.015 mm;髁突位移最小,约为0.006 mm。结论 本研究成功建立的颅颌面骨三维有限元模型,与生物实体有高度相似性,可用于前方牵引反作用力的相关研究,并可高度模拟牵引力在颞下颌关节的分布情况。     

A cephalometric evaluation of high-pull molar headgear and face-bow neck strap therapy.

The effects of two different extraoral appliances were evaluated over a 1-year period. Of the thirty-seven cases selected for study, twenty were treated with a face-bow neck strap and seventeen were treated with a high-pull molar headgear. Patients ranged in age from 10.10 to 16.6 years and averaged 13.4 years. The appliances exerted less than 600 Gm. of force per side and were worn for 12 to 16 hours per day. All cases were fully banded, and extraction and nonextraction treatment were included. An analysis of pretreatment data revealed a high degree of selection. Patients selected for high-pull treatment generally exhibited larger anterior face heights, steeper mandibular plane angles, and a greater amount of tooth eruption of the upper first molars than the patients selected for neck strap therapy. A control group of ten untreated subjects was matched to each treatment group to permit assessment of the impact of treatment on growth. Relative to normal growth, treatment with face-bow neck strap traction tended to direct the maxilla and mandible downward and backward. The palatal plane was lowered anteriorly and point A was retracted. The maxillary molars were extruded, and concomitantly an increase in anterior face height and mandibular plane angle was observed. On the other hand, the high-pull molar headgear traction resulted only in increased mandibular molar eruption. However, there was also a nonsignificant tendency for point A to be held back and for lower anterior face height to increase. The comparison of the two treatment samples revealed that the functional occlusal plane was tipped down at the back as the maxillary molars were more extruded in the neck strap sample. In the high-pull sample, the functional occlusal plane was unchanged and the mandibular molars were more extruded than they were in the neck strap group.     

J钩牵引方向对上颌切牙牙周膜初始应力影响的三维有限元分析

目的 分析J钩牵引方向变化对上颌切牙牙周膜应力分布的影响,探讨J钩牵引过程中的力学机制,为临床正畸提供客观的理论依据。方法 建立上颌牙齿及矫治器的三维有限元模型;在弓丝定点上以1.5 N的力保持与矢状面颊向30°不变,与牙合平面角度从0°~90°之间每5°加载一次,描绘出上颌切牙牙周膜应力图。结果 随着牵引角度增大,上切牙牙周膜压应力区由腭侧近颈缘和唇侧近根尖逐渐变为腭侧近根尖和唇侧近颈缘;牵引角度65°~75°时,中切牙牙周膜应力比较均匀,牵引角度45°~55°时,侧切牙牙周膜应力较均匀。结论 随着角度的增大,切牙由舌倾趋势变为唇倾趋势。     

Reverse sagittal split of the mandibular ramus for an unusual deformity

A reverse sagittal split osteotomy of the mandible for advancement or retraction of the mandible is described to be used in selected instances when the transoral modified sagittal ramus osteotomy would probably result in a pathologic fracture or an inadequate proximal segment. This procedure provides the same benefits as does the modified sagittal split osteotomy. A disadvantage of the procedure is that it requires both intraoral and extraoral incisions.     

成人安氏Ⅱ类1分类错牙合患者正畸前后唇部软组织测量和评估

目的 测量和评估成人安氏Ⅱ类1分类错牙合患者正畸前后的唇部软组织形态. 方法 选择30例已经完成正畸治疗的安氏Ⅱ类1分类错牙合成年患者,术后模型及头影测量的数据均在正常范围内. 对其正畸前后正面像和头颅侧位片唇红的矢状向厚度和垂直向厚度进行测量. 结果 正畸后上唇垂直向厚度有变小的趋势,下唇垂直向厚度有变大的趋势,差异有统计学意义(P<0. 05). 上唇矢状向唇红部组织厚度术后有增大的趋势,下唇矢状向唇红部组织厚度矫正后有减少的趋势,且有统计学意义(P<0. 05). 上颌上中切牙(U1C)矢状向内收量与上唇红(TUL)的内收呈显著正相关,下唇红(TLL)矢状向位置的变化与下颌切牙突点(L1C)位置变化存在正相关,下唇红(TLL)矢状向位置的变化与上颌切牙突点(U1C)位置变化存在正相关. 结论 安氏Ⅱ类1分类错牙合成人患者拔牙矫治后,可以通过切牙回收量较好地预测其唇部软组织正畸前后的矢状向厚度和垂直向厚度变化.     

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.     

Traumatic neuroma following sagittal mandibular osteotomy

A case of painful traumatic neuroma, arising from the inferior alveolar nerve after sagittal osteotomy of the mandible with demonstrable radiological change, is reported. The co-existence of temporomandibular joint (TMJ) pain-dysfunction syndrome and a painful traumatic neuroma had posed diagnostic problems. Some modifications of the surgical technique are discussed with a view to minimizing damage to the inferior alveolar nerve during sagittal osteotomy of the mandible. The aetiology, clinical features, diagnosis and treatment of traumatic neuromas are reviewed.