Improved clinical use of Twin-block and Herbst as a result of radiating viscoelastic tissue forces on the condyle and fossa in treatment and long-term retention: growth relativity.

Understanding mechanisms of action for orthopedic appliances is critical for orthodontists who hope to treat and retain the achieved corrections in patients with initial Class II mandibular retrognathism. That knowledge can help orthodontists produce clinically significant bone formation and avoid compression at the condyle-glenoid fossa region. It also assists us to understand the differences between short-term and long-term treatment results. It was previously thought that increased activity in the postural masticatory muscles was the key to promoting condyle-glenoid fossa growth. By analyzing results from several studies, we postulate that growth modification is associated with decreased activity, which leads to our nonmuscular hypothesis. This premise has its foundation on 3 key specific findings: significant glenoid fossa bone formation occurs during treatment that includes mandibular displacement; glenoid fossa modification is a result of the stretch forces of the retrodiskal tissues, capsule, and altered flow of viscous synovium; observations that glenoid fossa bone formation takes place a distance from the soft tissue attachment. The latter observation is explained by transduction or referral of forces. Evidence is presented, therefore, that the 3 trigger switches for glenoid fossa growth can similarly initiate short-term condylar growth modifications because the 2 structures are contiguous. These are displacement, several direct viscoelastic connections, and transduction of forces. Histologic evidence further shows that stretched retrodiskal tissues also insert directly into the condylar head's fibrocartilaginous layer. The impact of the viscoelastic tissues may be highly significant and should be considered along with the standard skeletal, dental, neuromuscular, and age factors that influence condyle-glenoid fossa growth with orthopedic advancement. These biodynamic factors are also capable of reversing effects of treatment on mandibular growth direction, size, and morphology. Relapse occurs as a result of release of the condyle and ensuing compression against the newly proliferated retrodiskal tissues together with the reactivation of muscle activity. To describe condyle-glenoid fossa growth modification, an analogy is made to a light bulb on a dimmer switch. The condyle illuminates in treatment, dims down in the retention period, to near base levels over the long-term.     

Condyle-fossa modifications and muscle interactions during herbst treatment, part 1. new technological methods

Changes in the condyle, the glenoid fossa, and the muscles of mastication were investigated in subjects undergoing continuous orthopedic advancement of the mandible with a Herbst-block appliance. The total sample consisted of 56 subjects and included 15 nonhuman primates (in the middle mixed, early permanent, and permanent dentitions), 17 human Herbst patients in the early permanent dentition, and 24 human controls from the Burlington Growth Center. The 8 nonhuman primates in the middle mixed dentition were the focus of this study. Mandibular advancement was obtained progressively in 5 animals by adding stops to the telescopic arms of fixed functional Herbst appliances with occlusal coverage; activations of 5.0 mm, 7.0 mm, and 8.0 mm were achieved. Two primates served as controls, and the third was a sham control. Two experimental animals and the 2 controls also wore surgically implanted electromyographic electrodes in the superior and inferior heads of the lateral pterygoid muscles and in the superficial masseter and anterior digastric muscles. Changes in condylar growth direction and amount were assessed with the Bj?rk method from measurements made on serial cephalometric tracings superimposed on metallic implants. Undecalcified sections, treated with intravenous tetracycline vital staining, were viewed with fluorescence microscopy to examine histologic changes in the condyle and the glenoid fossa. New bone formation in the fossa associated with continuous mandibular protrusion was quantified by using computerized histomorphometric analysis of decalcified histological sections and polarized light. The unique combination of permanently implanted electromyographic electrodes, tetracycline vital staining, and histomorphometry represents a significant technological advancement in methods and materials. Together, they demonstrated different muscle-bone interaction results for functional appliances than those reported in previous studies. In Part 1 of this study, we describe and discuss the techniques used in this research and give a brief overview of the findings; in Part 2 (to be published next month), we offer a more in-depth discussion of the results and the implications of our findings.     

生长发育高峰前期与高峰期安氏Ⅲ类错(牙合)颞下颌关节CBCT比较分析

目的 应用锥形束CT(CBCT)分析安氏Ⅲ类错(牙合)不同CVM分期颞下颌关节(TMJ)的生长发育差异.方法 分别对60名恒牙早期均角安氏Ⅲ类患者和60名恒牙早期正常(牙合)在牙尖交错位进行CBCT扫描,按颈椎CVM分期进行分组,使用Invivo5软件对影像重建并进行数据测量.通过SPSS22.0软件采用LSD法分析比较生长发育高峰前期与高峰期的髁突生长发育差异.结果 安氏Ⅲ类错(牙合)组相比正常(牙合)组中髁突绝大多数位于关节凹前位.安氏Ⅲ类错(牙合)组CS3-CS4期与CS1-CS2期生长变化差值显示髁突上间隙、前间隙减小量、后间隙增长量与正常(牙合)组相比有统计学差异(P<0.05);髁突前后径减小量、髁突高度增长量与正常(牙合)组相比有统计学差异(P<0.05);关节窝深度、关节后斜面角减小量、关节窝前后径增长量与正常(牙合)组相比有统计学差异(P<0.05).结论 安氏Ⅲ类错(牙合)生长发育高峰期相对于高峰前期髁突绝大多数位于关节凹前位且在关节凹中的位置更靠前上.髁突垂直向发育过度,更为细长,关节凹浅而宽.     

Replicating mesenchymal cells in the condyle and the glenoid fossa during mandibular forward positioning.

The purpose of this study was to identify and quantify the temporal sequence of replicating mesenchymal cells during natural growth and mandibular advancement in the condyle and the glenoid fossa. One hundred fifty 35-day-old female Sprague-Dawley rats were randomly divided into 10 experimental groups (10 rats each) and 10 control groups (5 rats each). The experimental groups were fitted with appliances that positioned the mandible forward. One hour before the rats were killed, bromodeoxyuridine (BrdU) was intravenously injected into them. Sections were cut and stained with anti-BrdU antibody to evaluate the number of replicating mesenchymal cells. Cellular uptake of BrdU was quantified with the Leica Qwin (Leica Microsystem Imaging Solutions, Cambridge, United Kingdom) system. The results showed that the numbers of replicating mesenchymal cells during natural growth were highest in the posterior region of the condyle and the anterior region of the glenoid fossa. In the experimental groups, the posterior region had the highest number of replicating cells for both the condyle and the glenoid fossa, with the condyle having 2 to 3 times more replicating cells than the glenoid fossa. The number of replicating mesenchymal cells, which is genetically controlled, influences the growth potential of the condyle and the glenoid fossa. Mandibular protrusion leads to an increase in the number of replicating cells in the temporomandibular joint. Individual variations in the response to growth modification therapy could be a result of the close correlation between mesenchymal cell numbers and growth.     

颞下颌关节盘前移位患者关节骨形态与矢状向关节盘位置的关系

目的　利用磁共振成像（MRI）技术和锥形束CT（CBCT）分析颞下颌关节盘前移位患者矢状向关节盘位置与关节骨形态的关系。方法　对97例患者的178个颞下颌关节（TMJ）进行回顾性分析，根据矢状向MRI上关节盘的位置分成4组，即对照组（关节盘无移位）、轻度组（关节盘轻度前移位）、中度组（关节盘中度前移位）和重度组（关节盘重度前移位）。然后利用Mimics 20软件基于CBCT数据进行TMJ的相关形态学参数测量，包括髁突线性尺寸（宽度、长度和高度）、髁突体积和表面积，关节窝的深度和长度，关节结节倾斜角，关节前、上、后间隙等，并对各组矢状髁突位置进行评估。使用方差分析、非参数检验和卡方检验等比较关节形态及位置参数的组间差异，采用相关性分析探索矢状关节盘位置与关节测量参数之间的相关性。结果　髁突的线性尺寸、关节窝深度、关节倾斜角、关节间隙和矢状髁突位置分布在4组间差异有统计学意义，而关节窝长度在4组间差异没有统计学意义；相关性分析显示：髁突的线性尺寸、髁突的体积及表面积、关节窝的深度、关节结节倾斜角和关节上间隙与关节盘矢状位置之间存在显著负相关，而关节后间隙与矢状关节盘位置之间存在显著正相关。结论　TMJ骨形态与不同矢状关节盘位置之间存在相关性，应警惕临床看到的关节骨形态的退行性改变可能是患者存在关节盘前移位的标志。     

Association between condylar position, joint morphology and craniofacial morphology in orthodontic patients without temporomandibular joint disorders

The present study investigated condylar position and joint morphology in adolescent patients and elucidated the possible association between the joint structure and condylar position, and craniofacial morphology. Sixty-five adolescent patients were selected as subjects and their tomograms and lateral cephalograms were analysed. No significant differences in joint spaces were found between the right and left temporomandibular joints. Both the condyles in this population were located slight anteriorly in the glenoid fossa. With respect to the association between condylar position, joint morphology and craniofacial morphology, the ramus plane angle also exhibited significant negative correlations with posterior, lateral and medial joint spaces. Furthermore, there was a significant negative correlation between the gonial angle and the anterior joint space. These findings imply that the condyle was likely to show more posterior position in the glenoid fossa when the mandible exhibited clockwise rotation. In conclusion, the condyle in the adolescent subjects showed a symmetrical anterior position relative to the glenoid fossa. In addition, the joint spaces and it ratios were significantly related to the craniofacial morphology associated with vertical dimension. It is suggested that the condylar position may be affected by craniofacial growth pattern.     

Condyle and fossa shape in Class II and Class III skeletal patterns: a morphometric tomographic study.

INTRODUCTION: The purpose of this investigation was to study the shapes of the condyle and the glenoid fossa in patients with Class II Division 1, Class II Division 2, and Class III malocclusions. METHODS: Axially corrected tomograms of 189 patients were used (109 Class II Division 1, 47 Class II Division 2, and 33 Class III). Five points on the condyle and 7 on the outline of the fossa were digitized. Size was assessed by the centroid size of each structure, and measurements of shape were made by principal component analysis of the Procrustes residuals. RESULTS AND CONCLUSIONS: Inspection of the principal components of shape showed that shape variability of the condyle was mainly related to inclination of the condylar head; shape variability of the fossa was related to inclination of the eminence and fossa height. Centroid size was correlated to age in the Class III group only. Condylar and fossa shapes were found to be different between the groups; the Class III group had a more elongated and anteriorly inclined condylar head and a wider and shallower fossa. In the Class III group, the condyle was closer to the roof of the fossa. The 2 Class II divisions differed only in the position of the condyle in the fossa, which was situated more anteriorly in the Class II Division 1 group.     

Craniofacial morphology and inclination of the posterior slope of the articular eminence in female patients with and without condylar bone change

This study investigated the association of craniofacial and glenoid fossa shapes and temporomandibular joint (TMJ) pathology in 39 orthodontic patients with signs and symptoms of TMJ disorders, using helical CT scans. Cephalometric measurements showed that 21 subjects with bilateral condylar bone change (BBC) had significantly smaller SNB angles, ramus heights and S-Ar/N-Ba ratios, as well as larger mandibular plane angles and lower anterior facial height than the 18 subjects with no condylar bone change (NBC). The average posterior slope of the left and right articular eminence in their central and lateral sections was significantly steeper in NBC than in BBC. Condylar bone change might, therefore, not only be related to the morphology of the mandible, but also of the glenoid fossa and cranial base. This appears to reflect adaptive changes in the condyle, articular eminence and cranial base in response to changes in loading.     

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目的探讨正畸治疗对成年安氏Ⅱ类高角型错患者颞下颌关节的影响。方法对2007年10月至2001年10月到云南省第二人民医院口腔正畸科就诊的21例成年安氏Ⅱ类高角型错患者,采用自锁托槽矫治技术进行正畸治疗,分别于治疗前、后,利用16层螺旋CT,进行颞下颌关节扫描,然后通过多层面重建(multiplanarreformation,MPR)技术对颞下颌关节进行三维重建及参数测量,并对结果进行统计学分析。结果治疗后有27侧髁状突处于关节窝内中性位,占57.2%(27/42),与治疗前比较,差异无统计学意义(P>0.05);而处于关节窝前位和后位的髁状突构成比分别为33.3%(12/42)和9.5%(4/42),与治疗前比较,差异均有统计学意义(均P<0.05)。髁状突前斜面倾角测量值在治疗后平均增大1.64°,与治疗前比较差异有统计学意义(P<0.05);关节结节后斜面斜度,关节窝前后径、内外径和关节窝高度的测量值与治疗前比较,差异无统计学意义(P>0.05)。结论正畸治疗能使成年安氏Ⅱ类高角型错患者的髁状突位置前移及髁状突前斜面适应性改建,但不会对颞下颌关节骨性结构和功能产生不利影响。     

成人与儿童颞下颌关节骨性形态比较研究

目的:比较成人与儿童颞下颌关节(temporomandibular joint,TMJ)骨性形态的差异。方法:用多排螺旋 CT(multislice CT,MSCT)对30例健康成年志愿者和20具咬合关系正常的儿童尸体 TMJ 扫描,结合影像中心保存的10例正常儿童 TMJ 的 MSCT 资料,在工作站上对上述60例120侧 TMJ 的 MSCT 图像进行多平面重建和参数测量,SPSS 软件对反映 TMJ 骨性形态特征的参数或其比值作统计学分析。结果:髁突纵轴倾斜角、髁突颈最小/髁突头最大横断面积、髁突前后径/关节窝前后径、髁突内外径/关节窝内外径、髁突在关节窝中后间隙/前间隙、关节窝前斜面倾角、关节窝深度、关节结节倾角,成人和儿童差异有显著性(P<0.05)。结论:成人与儿童 TMJ 骨性形态存在部分差异,它对 TMJ 疾病的防治有指导意义。     

Amount and direction of temporomandibular joint growth changes in Herbst treatment: a cephalometric long-term investigation

The amount and direction of condylar growth, glenoid fossa displacement, and "effective" temporomandibular joint (TMJ) changes (a summation of condylar growth, glenoid fossa displacement, and condylar position changes within the fossa) were analyzed in 35 Class II, Division 1 malocclusions (23 boys and 12 girls) treated with the Herbst appliance. Lateral head films in habitual occlusion and with the mouth wide open from before (T1) and after 7.5 months of Herbst treatment (T2) as well as 7.5 months (T3) and three years (T4) after treatment were evaluated. As a control group, a sample of 12 untreated male Class II Division I malocclusions was used during a 7.5-month time period corresponding to the treatment period (T2-T1) of the Herbst cases. The results revealed that during the treatment period (T2-T1) condylar growth was directed posteriorly about twice the amount as in the control subjects, and the fossa was displaced in an anterior inferior direction. The effective TMJ changes showed a pattern similar to condylar growth but were more pronounced. During the first posttreatment period (T3-T2), all TMJ changes reverted. The glenoid fossa was displaced backward; the amount of condylar growth and effective TMJ changes was reduced, and the changes were more superiorly directed. During the second posttreatment period (T4-T3), all TMJ changes were considered physiological. Conclusion: During Herbst treatment, the amount and direction of TMJ changes (condylar growth, fossa displacement, and effective TMJ changes) were only temporarily affected favorably by Herbst treatment.     

Development of the human temporomandibular joint. Computer-aided 3D-reconstructions

Computer-aided graphical three-dimensional reconstructions of histological serial sections of 12 human embryos and fetuses (25-250 mm Crown-rump length (CRL)) were used to trace the prenatal development of the elements of the human temporomandibular joint. The primordia of the condylar and coronoid processes could be identified as two bony peaks at the dorsal ends of the mandible at the stage of 25 mm CRL. The primordium of the temporal bone already existed at the stage of 37 mm CRL. The bone was apparent with a convex contour towards the condyle. The glenoid fossa was not yet visible. At 65 mm CRL, the osseous glenoid fossa could be distinguished at the enlarged temporal bone formation. The glenoid fossa developed posteriorly and medially from the condyle and extended in cranial and anterior direction. The glenoid fossa had various contours, changing from flat and slightly convex (65 mm CRL) to concave (250 mm CRL) with an articular tubercle. The distance between fossa and condyle increased proportionally. The lower joint cavity appeared at an earlier stage (65 mm CRL) than the upper joint cavity (70 mm CRL). Both cavities started development as isolated compartments fusing later on. The upper joint cavity followed the contour of the fossa, whereas the lower joint cavity followed the form of the condyle. The biconcave shape of the articular disc as well as the attachment of the lateral pterygoid muscle could be observed very early (70 mm CRL).     

Regeneration of mandibular condyle following unilateral condylectomy in canines.

PURPOSE: The purpose of this experimental study was to investigate regeneration of the mandibular condyle after unilateral condylectomy in canines. MATERIAL AND METHODS: Five 2-year-old beagle dogs underwent unilateral mandibular condylectomy and were sacrificed either immediately postoperatively (n=1) or 3 months later (n=4). Temporomandibular joints were examined radiologically and histologically, and sides were compared. RESULTS: All joints showed postoperative regeneration of the condylar head. Maximum regeneration of the condyle occurred medially, where most bone of the glenoid fossa was present, rather than laterally. From an anteroposterior perspective, regeneration of the condylar head was more favourable anteriorly, facing the inferior slope of the glenoid fossa. Regenerated articular cartilage was irregular. Articular discs displayed central thickening compared with unoperated joints. The bone of the glenoid fossa was normal. CONCLUSION: Unilateral mandibular condylectomy in canines resulted in a certain degree of condylar regeneration during a 3-month postoperative period, with some irregular articular cartilage formation.     

An unusual case of acquired unilateral condylar hypoplasia.

A case is described of acquired unilateral condylar hypoplasia, in which the right condyle seemed to have been fractured at an early age. There is evidence to suggest that the unresorbed condylar remnant persisted in the glenoid fossa and that a new condylar head had developed anterior to the articular emminence. This 'new head' showed a carrot-shaped radiolucent wedge suggestive of the condylar growth cartilage and, clinically, exhibited some growth potential. A complex composite odontome present in place of the mandibular right third molar may also have been caused by this early trauma.     

An analytic method for evaluating condylar position in the TMJ and its application to orthodontic patients with painful clicking.

The purpose of this study was to develop a new method for evaluating the three-dimensional position of the mandibular condyle relative to the glenoid fossa and further to investigate its clinical application to orthodontic patients with temporomandibular disorders (TMD). A three-dimensional configuration of the temporomandibular joint was constructed by 108 triangles for the condyle and 180 triangles for the glenoid fossa. The shortest distance between the condyle and glenoid fossa (CGFD) was calculated in the model along a line perpendicular to the center of gravity of a triangle on the condyle. The CGFD was determined in the anterior, posterior, middle, lateral, and medial areas on the condyle. Preliminary investigation revealed that the present technique is accurate, regardless of condylar rotation and/or inclination to the tomographic table. The technique was applied to the diagnosis of orthodontic patients with painful clicking and TMD. It is shown that the present approach provides a method for evaluating the positional relationship between the mandibular condyle and glenoid fossa in patients with TMD.     

髁突在关节窝中的位置及其在临床诊断治疗中的意义

临床治疗中,特别是髁突外伤骨折、正颌手术、修复咬合重建、正畸治疗以及在颞下颌关节紊乱病的诊断和治疗中,要考虑髁突在关节窝中的位置变化。本文通过文献回顾,结合我们的研究成果,讨论髁突在关节窝中的正常生理位置及其在颞下颌关节紊乱病特别是关节盘移位的诊断和治疗中的意义。目前多项研究认为,健康成年人髁突平均位置为基本中性,但存在较大变异;髁突后移可能是关节盘前移位的危险因素,关节盘前移位也可导致髁突后移;在关节盘移位的牙合垫治疗中,髁突在牙合垫戴入后显著向前、下移位,可有效改善盘突关系;稳定牙合垫使髁突前下移位不明显,改善盘突关系的效果有限。此外,再定位牙合垫使髁突前下移位还可促进髁突骨质的改建。     

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??Abstract??The condylar position should be taken into account in the diagnosis and treatment of condyle fracture??orthognathic surgery??occlusal reconstruction and temporomandibular disorders. The normal condylar position in the glenoid fossa and its clinical significance in the diagnosis and treatment of temporomandibular disorders??for example the disc displacement??will be discussed here through the literature review and the combination of our research findings. Many research data suggested a centric position of condyle in a normal joint??with individually variances. A posterior condylar position might be a risk factor of disc displacement??and on the other hand??the disc displacement might induce condyle to move posteriorly. With the use of anterior repositioning splint for treating anterior disc displacement with reduction??the condyle moved anteriorly and inferiorly??the condyle-disc relationship could be improved immediately. Besides??splint therapy may facilitate regenerative remodeling of condyles.     

The assessment of the short‐ and long‐term changes in the condylar position following sagittal split ramus osteotomy (SSRO) with rigid fixation

Summary The purpose of this study was to compare the short‐ and long‐term changes in condylar position related to the glenoid fossa, and skeletal and occlusal stability after orthognathic surgery. All of the study patients were assessed by cone‐beam computed tomography images for condylar rotational changes and anteroposterior position in the pre‐surgery, post‐surgery and post‐retention period. The condylar positions were evaluated on three planes: axial, coronal and sagittal. In the skeletal and occlusal measurements, there was no significant difference between the post‐surgery group and the post‐retention group. After sagittal split ramus osteotomy (SSRO), the condyle on the axial plane rotated inward (P < 0·05) and maintained during the post‐retention period. In the anteroposterior condylar position related to the glenoid fossa, the condyles had changed from the anterior position in the pre‐surgery group to a concentric position in the post‐surgery group and then returned to the anterior position in the post‐retention groups. These results suggested that the changed anteroposterior condylar position in the glenoid fossa after SSRO with rigid fixation had moved from a concentric to anterior position for post‐retention period.     

Orthopedic effect of the extraoral chin cup appliance on the mandible.

An anatomic photoelastic model of a human skull was constructed with the use of individual simulants for teeth, bone, and periodontal ligaments. The following effects of extraoral chin cup traction were observed: 1. Stresses were noted in the area of the pterygoid plates of the sphenoid bone due to the insertion of the simulated external pterygoid muscle. 2. Because of direct contact of the condyle against the posterior surface of the glenoid fossa, forces were seen to be transmitted to this anatomic area. 3. Stress trajectories followed the trabecular pattern of the anatomic configuration of the mandible. 4. Beginning at the apices of the incisor teeth, the stresses emanated through the body, the angle and retromolar triangle of the mandible, radiating in a posterosuperior fashion and concentrating at the neck of the condyle. 5. Selected sectioning of the mandibular model showed evidence of stress concentration at the lingual aspect of the angle and retromolar area as well as at the condylar neck at the level of the external pterygoid muscle insertion. The effects of orthopedic forces produced by an extraoral chin cup in this study are correlated with the histologic and clinical observations during the utilization of this appliance in the treatment of Class III malocclusion.     

骨性Ⅲ类偏颌患者髁突与(牙合)平面特征的CBCT研究

目的 利用锥形束CT(CBCT)测量分析骨性Ⅲ类偏颌患者髁突及(牙合)平面特征。方法 选取符合纳入标准的骨性Ⅲ类成年患者40例,所有个体按照颏下点偏离正中矢状面距离进行分组,分别测量各组左右两侧(牙合)平面角、髁突位置及形态,并对数据进行统计学分析。结果 骨性Ⅲ类偏颌患者的偏侧与对侧相比,(牙合)平面角、关节前间隙、关节上间隙、关节外间隙及髁突内外径差异有统计学意义(P<0.05),偏侧关节后位所占比例较大,下颌骨偏移量与偏侧髁突前间隙及对侧(牙合)平面角均呈正相关(P<0.01)。骨性Ⅲ类非偏颌患者的左右两侧(牙合)平面角、髁突位置及形态指标之间差异均无统计学意义(P>0.05),关节以前位、中位为主。结论 骨性Ⅲ类偏颌患者左右两侧(牙合)平面角、髁突位置及形态不对称,偏侧(牙合)平面角及髁突内外径较小,髁突向后下内方移位,且偏颌程度与(牙合)平面角及髁突位置之间存在相关性。