The position of the mandibular condyle at maximal mouth opening in normal subjects

: To investigate the position of the mandibular condyle at maximal mouth opening in individuals 19 to 30 years of age with no functional disorders of the masticatory system. : Measurements were made in 153 subjects (99 men, 54 women), and 41 men and 44 women had transcranial radiographs taken of their right and left temporomandibular joints in the closed and maximal opening positions. : In all subjects the condyle moved forward beyond the summit of the articular eminence, and in more than half the subjects the condyle was located inferior to the eminence at maximal opening. : The correlation between maximal opening and anterion shift of the condyle from the summit of the eminence was significant, but the correlation with vertical shift of the condyle was not significant. The correlation between the form of the glenoid fossa (length and depth) and anterior or vertical shift of the condyle from the summit of the eminence also was not significant.     

Treatment of chronic mandibular dislocations using a new miniplate

Temporomandibular joint (TMJ) dislocation is defined as an excessive forward movement of the condyle beyond the articular eminence with complete separation of the articular surfaces and fixation in that position. The aim of this study was to describe a modified miniplate designed for treating chronic mandibular dislocations and evaluate the results of its placement in one patient, who was followed for 18 months. The treatment of chronic mandibular dislocation using this modified miniplate was shown to be efficient in relation to the postoperative maximal mouth opening, recurrence and articular function.     

Dautrey's procedure: an alternative for the treatment of recurrent mandibular dislocation in patients with pneumatization of the articular eminence

Temporomandibular joint (TMJ) dislocation is an involuntary forward movement of the mandible beyond the articular eminence with the condyle remaining stuck in the anterior-most position, leaving the patient unable to close their mouth. Conservative treatment for this condition includes the injection of sclerosing agents or the intramuscular administration of botulinum toxin type A, while surgical therapy requires either removal or augmentation of the articular eminence. Once the surgical treatment plan has been determined, pneumatization of the articular eminence may turn a relatively simple procedure into a great surgical challenge. We present herein the cases of two patients suffering from recurrent mandibular dislocation who happened to have pneumatization of the articular eminences. Both patients were treated with a down-fracture of the zygomatic arch, known as Dautrey's procedure, modified by the application of a miniplate connecting the displaced arch and the lateral portion of the articular eminence. Neither patient had suffered a new episode of dislocation at their most recent postsurgical visit.     

Temporomandibular joint mobility assessment: a comparison between four methods

SUMMARY Temporomandibular joint (TMJ) mobility is assessed in different ways. Measurement of the interincisal distance in maximal mouth opening added to the vertical overlap of the dentition, i.e. linear mouth opening (LMO); measurement of angular displacement of the mandible relative to the cranium at maximal mouth opening, i.e. angle of mouth opening (AMO); assessment of the condylar position relative to the articular eminence performed on transpharyngeal radiographs in maximal mouth opening, i.e. condylar mobility (CM); measurement of angular displacement of the mandible at maximal mouth opening relative to the closed mouth position of the mandible, assessed on transpharyngeal radiographs in maximally opened and in closed mouth position, i.e. radiographic angle of mouth opening (RAMO). To compare these TMJ mobility assessment methods and to analyse the relationship between LMO, AMO and mandibular length (ML), 28 healthy volunteers (13 females, 15 males), mean age 29.6 years (range 21–41) with a symmetrical mouth opening pattern were assessed. LMO, AMO, ML, and RAMO were measured and CM was assessed on transpharyngcal radiographs. LMO and AMO were strongly and significantly related (r=0.71). LMO was significantly influenced by AMO and ML. No significant differences between AMO and RAMO were found. CM was strongly and significantly related to AMO (r=0.72) and weakly but significantly related to LMO (r=0.42). Based on the results of this study recommendations are made regarding the appropriate application of TMJ mobility assessment methods.     

Arthrocentesis followed by intra-articular autologous blood injection for the treatment of recurrent temporomandibular joint dislocation

Temporomandibular joint (TMJ) dislocation is an excessive forward movement of the condyle beyond the articular eminence with complete separation of the articular surfaces and fixation in that position. This study was conducted to assess autologous blood injection to the TMJ for the treatment of chronic recurrent TMJ dislocation. Fifteen patients with bilateral chronic recurrent condylar dislocation were included in the study. Bilateral TMJ arthrocentesis was performed on each patient, followed by the injection of 2 ml of autologous blood into the superior joint compartment and 1 ml onto the outer surface of the joint capsule. Preoperative and postoperative assessment included a thorough history and physical examination to determine the maximal mouth opening, presence of pain and sounds, frequency of luxation, recurrence rate, and presence of facial nerve paralysis. Eighty percent of the subjects (12 patients) had a successful outcome with no further episodes of dislocation and required no further treatment at their 1-year follow-up, whereas three patients had recurrent dislocation as early as 2 weeks after treatment. Autologous blood injection is a safe, simple, and cost-effective treatment for chronic recurrent TMJ dislocation.     

Is condylar position a predictor for functional signs of TMJ hypermobility?

Temporomandibular joint (TMJ) hypermobility is noted only when it interferes with smooth mandibular movements. These interferences (viz. clicking sounds and jerky mandibular movements) result from condylar dislocation in front of the eminence at wide mouth opening, or alternatively in front of the articular disc (posterior disc displacement). The aim of this study was to test the hypothesis that condyles of hypermobile persons are positioned more anterosuperiorly to the crest of the eminence during maximum mouth opening than those of persons without TMJ hypermobility. Possible posterior disc displacement was also evaluated. Nine persons with symptomatic hypermobility and nine control persons free of internal derangements were included, their diagnoses being based upon opto-electronic movement recordings. Condylar positions during maximum mouth opening were analysed on magnetic resonance images with two slightly different methods, showing the degree to which the condyles are displaced around the eminence. No posterior disc displacements were found in any of the magnetic resonance images. After excluding an outlier and using both measurement methods, a small difference in condylar position was found between the two groups of subjects. The condyles of all hypermobile persons travelled beyond the eminence; however, so were the condyles of nearly half of the non-hypermobiles. The large overlap between both groups suggests that condylar position alone is not a good predictor for symptomatic TMJ hypermobility. It is probably the combination of condylar location in front of the eminence with a particular line of action of the masticatory muscles, which gives rise to functional signs of hypermobility.     

髁突运动异常的曲面断层观察

为研究髁突的运动度，用曲面断层张、闭口片对１４４例颞下颌关节紊乱综合征（ｔｅｍｐｏｒｏ－ｍａｎｄｉｂｕｌａｒｊｏｉｎｔｄｉｓｔｕｒｂａｎｃｅｓｙｎｄｒｏｍｅ，ＴＭＪＤＳ）患者的髁突与关节结节之间的位置关系进行分析。根据髁突与关节结节的关系及双侧运动是否一致将髁突的运动度分为６型，并对各型的性别与年龄组成、张口度与张口型、弹响与疼痛情况、病程及骨质改变进行了分析。结果说明下颌过大运动所造成的关节结构及下颌肌肉、韧带的急性损伤是产生ＴＭＪＤＳ的主要原因之一。     

Treatment of chronic mandibular dislocations using miniplates: follow-up of 8 cases and literature review

Temporomandibular joint (TMJ) dislocation is an excessive forward movement of the condyle beyond the articular eminence with complete separation of the articular surfaces and fixation in that position. This study reports 8 cases using miniplates for chronic mandibular dislocations, evaluates the results and critically reviews the literature. The sample was obtained from the records of the Oswaldo Cruz University Hospital and comprises patients undergoing chronic mandibular dislocation treatment using 2.0 mm titanium miniplates between August 2002 and March 2004. Pre- and postoperative assessment included a thorough history and physical examination to determine the maximal mouth opening, presence of pain and sounds, frequency of luxations, recurrence rate and presence of facial nerve paralysis. The mean maximal mouth opening preoperatively was 42.75 ± 11.53 mm and was 45.62 ± 8.52 mm postoperatively. There was no facial nerve paralysis. Miniplate fracture was observed in 2 cases and there was one recurrence. Treating chronic mandibular dislocation using miniplates was shown to be efficient in relation to postoperative maximal mouth opening, recurrence and articular function, however, the possibility of the miniplate fracturing must be considered.     

Study on the reconstruction of a four-dimensional movement model and the envelope surface of the condyle in normal adults

The objective of this study was to reconstruct the envelope surface of the condyle and the four-dimensional trajectory model in mandibular border movement in normal adults. Eleven healthy subjects were selected as volunteers. Cone-beam computed tomographic (CBCT) scanning was performed on the volunteers. The three-dimensional (3D) movement path of the mandible was recorded using a virtual articulator (PN-300), which was based on a 3D model of the mandible. We used Proplan CMF 3.0 (Materialise) software to perform this from the DICOM data generated by CBCT scans. The distance of condylar movement was measured in this model during volunteers’ mouth opening, protrusion, and lateral excursions. The envelope surface of the condyle was reconstructed by merging a functional condylar surface at each recording moment during the movement of the whole border. In the mandibular digital models, the condyle moved downward firstly, and moved upward to the position of maximum mouth opening. The condyle moved forward and downward during protrusion. The working condyle rotated slightly and the non-working condyle moved forward, downward, and inward during lateral excursions. The mean (SD) movement distance of 11 subjects was 19.04 (4.37) mm during mouth opening (including downward and upward) and 9.75 (2.38) mm during protrusion. During lateral excursions the mean (SD) movement distance of the working condyle was 2.87 (1.13) mm, the mean (SD) movement distance of the non-working condyle was 10.85 (3.25) mm. The envelope surface of healthy volunteers showed a double-peak pattern. The envelope surface of the condyle and four-dimensional movement model can be reconstructed by merging the trajectory of the mandible recorded from the novel virtual articulator PN300 and a 3D image of the mandible.     

The relationship between maximal jaw opening and size of skeleton: a cephalometric study

summary The purpose of this study was to investigate the correlation between maximal mouth opening and size of the skeleton. The subjects were dental students at the Dental School of the Health Sciences University of Hokkaido with no functional disorders of the masticatory system. The stature and maximal mouth opening were recorded in 29 males and 31 females. These subjects agreed to have a lateral cephalogram taken at the closed and maximal mouth opening positions. The correlations between the maximal mouth opening and the body height, mandibular length and mandibular angle were significant. The correlation between the maximal mouth opening and the movement of the condyle was also significant.     

The temporomandibular ligament and the articular eminence as constraints during jaw opening

It is generally thought that during symmetrical jaw opening the mandible rotates about an axis passing through the centres of the two mandibular condyles, and translates down the articular eminence. The author argues that there are no data to support this assumption. The true combination of movements can only be understood by understanding the constraints that operate during jaw opening and these are the articular eminence and the temporomandibular (TM) ligament. The TM ligament is pulled taut during jaw opening, and so acts like the chains of a swing: the mandible rotates about the lowest attachment of the TM ligament to the condyle and swings about the most posterior attachment to the articular tubercle. The effects of combining the swing and rotation are demonstrated by a simple mechanical model. The functional advantage of the TM ligament is that it keeps the condyle close to the temporal bone during jaw opening, until the condyle passes under the articular eminence. The constraints described in this paper may have important implications related to the diagnosis and treatment of some disorders of the TM joint (to be described in a later paper).     

Occupational differentiation in dentistry 3. Hypermobility of the temporomandibular joint and condylar position at maximal mouth opening

Hypermobility of the temporomandibular joint is only noted when it interferes with smooth mandibular movements. These interferences may result from a condylar dislocation beyond the temporal eminence at maximum mouth opening. Aim of this study was to test whether the condyle of a symptomatically hypermobile temporomandibular joint is positioned more anterosuperiorly to the temporal eminence at maximum mouth opening than a condyle without hypermobility. Nine persons with a hypermobile temporomandibular joint and 9 control persons participated. Diagnostics were based upon opto-electronic mandibular movement recordings. Condylar positions at maximum mouth opening were assessed by magnetic resonance imaging. A small significant difference in condylar position was found between groups. Condyles of persons with a hypermobile temporomandibular joint moved beyond the temporal eminence. However, this was also true for nearly half of the control persons. This suggests that condylar position alone is not a sufficient condition for symptomatic hypermobility of the temporomandibular joint. Maybe, symptoms of hypermobility only become apparent in combination with a particular line of action of the masticatory muscles.     

髁突运动中心大张口轨迹与关节窝形态的关系及临床应用探讨

目的　探讨髁突运动中心大张口轨迹与关节窝形态的关系 ,对TMD患者髁突运动中心轨迹特征进行初步研究。方法　利用自行开发的髁突运动中心轨迹显示分析系统 ,分别以运动中心、终末绞链轴点作为参考点 ,观察 10名健康人和 7例临床检查怀疑盘前移位的TMD患者大张口轨迹 ,与磁共振成像得到的相应关节窝形态及关节盘位置诊断结果进行比较。结果　健康人左右侧运动中心轨迹与关节窝形态曲线重合率分别为 80 % (8/ 10 )和 90 % (9/ 10 ) ;终末绞链轴点轨迹与关节窝形态重合率均为 0 (0 / 10 )。TMD患者中 ,11侧盘前移位关节 ,除 1侧可复性盘前移位关节外 ,髁突运动中心轨迹均与正常的轨迹明显不同 ,出现各种改变 ;3侧正常盘位关节 ,髁突运动中心轨迹均与健康人的轨迹相似。结论　运动中心轨迹较终末绞链轴点个体稳定 ,可认为是较理想的研究髁突运动轨迹的参考点     

Cephalometric analysis of condylar adaptations to altered mandibular position in adult rhesus monkeys, Macaca mulatta

Morphological adaptation to altered position of the mandible was investigated in 19 young adult rhesus monkeys (n = 10 experiment and 9 control). The experimental animals had a bite-splint cemented to the maxillary dentition which opened the bite interincisally by 15 mm and was worn continuously for 48 weeks. Lateral radiographic cephalograms were taken prior to the experiment and at 12-week intervals thereafter. Computerized cephalometry, facilitated by the use of radio-opaque bone markers, was used to assess changes in mandibular position and morphology. An immediate effect of the bite-splint was the clockwise rotation (opening) of the mandible and anterior translation of the condyle on the articular eminence, much as occurs normally during jaw depression. During the next 48 weeks, the mandible (1) rotated anti-clockwise (closed) due mainly to antero-superior displacement of the maxilla and intrusion of the mandibular dentition and (2) underwent a significant increase in length (p less than 0.05). These findings indicate that the mandibular condyle of young adult monkeys is capable of small, but biologically significant, compensatory growth after displacement.     

Correction of condylar displacement following intraoral vertical ramus osteotomy

Fifteen patients who demonstrated condylar sag after intraoral vertical ramus osteotomy for the correction of mandibular prognathism were treated nonsurgically to establish the desired postoperative occlusion. A mean inferior displacement of 3.33 mm and anterior displacement of 2.18 mm were observed tomographically after surgery. Postoperatively, a geometric splint was constructed to compensate for the magnitude of condylar displacement and was used to replace the original splint to hold the distal segment in an overcorrected position. Skeletal fixation was maintained for 5 to 6 weeks. Tomographic evaluation of the temporomandibular joint (TMJ) during maxillomandibular fixation showed a slight superior (1.03 mm) and posterior (0.51 mm) movement of the condyle in the fossa. After release of fixation and removal of splint, a further superior (2.05 mm) and posterior (1.01 mm) repositioning of the condyle was observed. This later movement correlated with the placement of light class III elastic traction to seat the condyles into the glenoid fossae and establish a class I occlusion. Temporomandibular joint tomograms confirmed complete seating of the condyles in the fossa and lateral cephalograms demonstrated a corresponding change in the position of the mandible to the desired postoperative position. This technique has been effective in preventing postoperative malocclusion resulting from condylar sag.     

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.     

A comparative study of the treatment of unilateral fractured and dislocated mandibular condyles in the rabbit

This study evaluated the results of three methods of managing simulated unilateral dislocated fractured mandibular condyles in the rabbit. The first method consisted of surgical reduction of the fractured condyle to its anatomic position and its subsequent fixation with a titanium plate. The second method differed from the first by completely detaching the condyle, then replacing it as free graft. The third method left the fractured condyle in its dislocated position outside the glenoid fossa. Eighteen rabbits were used, 6 animals for each method. Half the animals in each group were killed at 4 weeks, the other half at 14 weeks postoperatively. Clinical, morphologic, functional, radiologic, and histologic examinations were conducted on all animals. The results indicated that open reduction with internal fixation with no disruption of the blood supply to the condyle provided the most favorable results. While closed reduction without internal fixation gave good functional results, definite reduction in ramus height on the operated site was observed in this group of animals. Animals that had open reduction and internal fixation using the condyle as a free graft did not do as well as the other two groups. Despite good mouth opening and occlusion, more animals showed facial asymmetry and it was more severe. None of the condyles were lost as result of necrosis, but healing took longer when compared with the other group of animals.     

An adult case of TMJ osteoarthrosis treated with splint therapy and the subsequent orthodontic occlusal reconstruction: adaptive change of the condyle during the treatment.

This article reports treatment for a 21-year 11-month old female patient with severe osteoarthrosis of the TMJ with a special reference to adaptive changes of the condyle during the treatment. She had severe open bite with a Class II molar relationship; she had limited mouth opening, TMJ sounds, pain, and tinnitus. Lateral tomograms showed flattening and deep erosion on the left condyle, and an MRI revealed anterior disk displacement without reduction. By manipulation and splint therapy, TMJ pain and tinnitus were eliminated, then orthodontic treatment was initiated, maintaining the splint-induced position of the condyles. After 2 years of orthodontic treatment with a multibracket appliance, an acceptable occlusion was achieved with a Class I molar relationship. On lateral tomograms after treatment, bony deformation of the left condyle disappeared and adaptive remodeling was recognized with a uniform joint space in the left TMJ. However, repositioning of the disk was not achieved. Adaptive changes or functional remodeling experienced in this patient may be due to stable occlusion, uniform joint space, and the consequent biomechanical equilibrium in the TMJ.     

Relationship between the temporomandibular joint and pantographic tracings of mandibular movements

Lateral polytomography of the TMJ and pantographic tracings of mandibular movement were performed in 30 patients with TMJ pain-dysfunction syndrome. The condyles were classified as rounded or flattened. The articular eminences were classified as convex or flattened. Two types of immediate side shift, progressive side shift and vertical protrusive tracing, were observed. Type A was curved, Type B was straight. A significant relationship was found between the shape of the TMJ and the tracing pattern. Type A immediate side shift (when present), progressive side shift, and vertical protrusive tracings were more typical of patients with rounded condyles and convex articular eminences. Type B was typical of patients with flattened condyles and, to a lesser extent, flattened articular eminences. Superior displacement of the rotating condyle was found only in patients with flattened condyles.     

The control of condylar growth: an experimental evaluation of the role of the lateral pterygoid muscle

The present study used 21 male albino rats to test the hypothesis that lateral pterygoid traction regulates the growth of the mandibular condyle. The condyles, the rami, and the top of each glenoid fossa were marked with metallic implants, and, following bilateral section of the condylar neck, one lateral pterygoid muscle was extirpated. On the basis of the literal details of Petrovic's cybernetic model, it was assumed that the continued forward growth of the midface and the backward translation of the glenoid fossa would combine to produce a progressive disturbance in the buccal occlusion that would, in turn, generate a reflex contraction of the remaining lateral pterygoid muscle. Initially, however, growth of the isolated condyles would have little impact on the spatial position of the rest of the mandible. As a result, the condyles on the side with the intact lateral pterygoid should grow for a time at a maximal, open-circuit rate, whereas the experimental condyle, deprived of all muscle traction, should show only a minimal "commanded" rate of growth. The serial change in the position of the condylar and ramal implants was assessed cephalometrically for 6 weeks, and between-sides differences were analyzed by randomized block analysis of variance. The presence or absence of the lateral pterygoid muscle had no significant effect on the anteroposterior position of the condylar implants and only a slight, transitory effect on their vertical position. The translation of the ramal implants, however, was greatly affected by the condylotomy. On both control and experimental sides, the mandible collapsed upward and backward until contact between the growing condyle and ramus had been achieved, whereupon a downward and forward pattern of translatory growth was re-established. Although it could not be shown that lateral pterygoid traction per se is a significant factor in the growth of isolated condyles, it was concluded that the condyle is vitally important to the translatory growth of the mandible as a whole. On the basis of these data and the current literature, a simple hypothesis was advanced for the control of condylar growth by the ongoing pattern of functional loading and for the role of this growth in the normal downward and forward displacement of the rest of the mandible.