Trajectories of condylar points during nonworking side and protrusive movements of the mandible.

STATEMENT OF PROBLEM: During lateral excursive and protrusive jaw movements, condylar points are distant from any instantaneous rotational center. Therefore, it is likely that different condylar points would follow similar trajectories during these movements. PURPOSE: This study evaluated the effect of changes in condylar point location on trajectories of condylar points on the nonworking side and during a protrusive jaw movement and compared these changes with the effects described for open-close and working-side condylar movements in the same group of subjects. METHODS: The movements of 5 clinically determined condylar points were recorded in 44 subjects during a contralateral excursion and during protrusion (7 radiographically determined condylar points in 2 subjects). RESULTS: During any single jaw movement, the trajectory of each condylar point was similar in form and dimension to the other condylar points within that subject. CONCLUSION: Changes in condylar point location had little effect on the trajectories of condylar points on the nonworking side and during protrusive jaw movement.     

Analysis of sagittal condylar path inclination in consideration of Fischer's angle

This study investigated the sagittal condylar path during protrusive and lateral excursions by analysing the actually measured jaw movement data and re-evaluated the setting of the sagittal condylar path inclination in consideration of Fischer's angle. Protrusive and lateral excursions of 10 healthy subjects were measured using a three-dimensional mandibular movement analysing system. Condylar path inclinations at the hinge-axis point and the corresponding external point laterally extending from the condyle were evaluated in the sagittal plane. Fischer's angle was defined as the difference between the sagittal condylar inclinations during protrusive and lateral excursions on the non-working side, by keeping the corresponding horizontal distance from the intercuspal position (ICP) equivalent at the incisal point. Analysis was performed at three different magnitudes of excursions, where the incisal point was located at 1, 3 and 5 mm away from the ICP. There was no significant difference in the sagittal condylar path inclination or the Fischer's angle between two condylar reference points. However, they were significantly different across the three different magnitudes of excursions for both condylar reference points, i.e. sagittal condylar path inclination (P = 0.003 for protrusive excursion, and P < 0.001 for lateral excursion respectively; two-way repeated-measures anova), and Fischer's angle (P = 0.013, two-way repeated-measures anova) became smaller as the incisal point became distant from the ICP. Moreover, 3- and 5-mm eccentric positions were included in the 95% CI where Fischer's angle equals zero and were considered to be clinically acceptable to adjust the sagittal condylar inclination on the semiadjustable articulators.     

Electromyographic activity of the human lateral pterygoid muscle during contralateral and protrusive jaw movements

Understanding of the normal function of the lateral pterygoid muscle is limited. The principal aim here was to determine whether there is a progressive increase in lateral pterygoid activity as the mandibular condyle moves downwards and forwards as would be expected if the muscle is concerned with the precise horizontal positioning of the mandible. In eight humans, recordings were made of the activity of the superior (SHLP) and inferior (IHLP) heads of the lateral pterygoid and the masseter, anterior temporal, posterior temporal and digastric muscles, together with the movement of the palpated lateral condylar pole (JAWS-3D tracking system) during trials of a contralateral and a protrusive jaw movement. Recording sites in SHLP and, in one participant, IHLP were verified by computed tomography. In each participant there was a progressive increase in the rectified and smoothed SHLP and IHLP activity in association with condylar movement during the contralateral and protrusive jaw movement. Further, irregularities in condylar movement, which reflected variations in the rate at which the jaw was moved, were correlated in time with prominent bursts of SHLP and IHLP activity. In all participants there was a consistently high correlation coefficient between the rectified and smoothed SHLP and IHLP activity and condylar displacement during the contralateral or protrusive jaw movements. For example, the mean (+/-SD) correlation between anterior condylar translation during contralateral excursion and SHLP activity was 0.91+/-0.09, and for IHLP 0.96+/-0.02. For the masseter, anterior temporal, posterior temporal and digastric muscles, mean r-values were, respectively, 0.10+/-0.77; -0.14+/-0.72; 0.24+/-0.78; 0.54+/-0.47. When treated as a group the correlation coefficients for SHLP and IHLP were statistically significantly different from the correlation coefficients for the other muscles treated as a group (ANOVA; p < 0.002 for correlation with anterior translation). These observations support the notion that the lateral pterygoid provides the principal driving force for moving the jaw forwards or laterally in protrusive or lateral excursive condylar movements. Further, the data suggest that the muscle plays a part in the fine control of jaw movements.     

Anatomical location of various condylar points for jaw movement analysis in Japanese women

Summary The aim of this study was to determine anatomical locations of the hinge axis point, kinematic axis point and reference point for the palpated lateral condylar pole on lateral cephalograms. Subjects comprised 18 Japanese women selected according to following criteria: normal occlusion; and absence of signs and symptoms of stomatognathic function. Jaw movement and the condylar reference points noted earlier were recorded three‐dimensionally with six degrees of freedom, and kinematic axis point and hinge axis point were determined using an optoelectronic jaw‐tracking system. Lateral cephalograms were used to determine anatomical locations of the three points in the condyle. Mean location of hinge axis point was 12·9 mm anterior of the porion and 5·3 mm inferior to the Frankfort horizontal plane, the kinematic axis point was situated in 12·8 mm anterior and 0·1 mm inferior, and the reference point for the palpated lateral condylar pole was situated 10·7 mm anterior and 0·8 mm inferior, respectively. The kinematic axis point was located outside the condyle in the majority of subjects. The reference point for the palpated lateral pole offers a useful indicator in the analysis of condylar movements.     

Relationship between condylar and incisor point displacement during habitual maximum open-close movements

SUMMARY The relationship between condylar movements and incisor point movements during habitual maximum open-close movements were studied in 10 healthy male and 10 healthy female subjects. Jaw movements were recorded by means of an opto-electronic jaw movement recording system, OKAS-3D, capable of recording the six degrees of freedom at a sample frequency of 300 Hz. The lower jaw position of the lateral pole of the condyles was found by means of palpation. In order to analyse the movements, the opening and closing path of the incisor point were divided into ten equal intervals and the corresponding condylar displacement in each interval was calculated. A displacement index was obtained by normalizing the condylar displacement with respect to the maximum condylar displacement. Due to the normalization, the displacement index is not sensitive to possible errors in the location of the lateral condylar point. A clear condylar displacement was already recorded in the first movement interval, right at the start of opening (average displacement index in the first opening interval was significantly greater than zero, P < 0.0005). The condylar displacements in the start and the end interval of opening and closing were smaller than in the intermediate movement intervals ( P < 0.00005).     

Human lateral pterygoid muscle activity on the return phase of contralateral and protrusive jaw movements

Normal function of the lateral pterygoid muscle is not well understood. The principal aim of this study was to determine whether there is a progressive decrease in lateral pterygoid activity as the condyle moves posteriorly and superiorly during the return phase of a contralateral or protrusive jaw movement, as would be expected if the muscle is involved in controlling or stabilizing the condyle during the return phase of these movements. In seven humans, electromyographic activity was recorded in the superior (SHLP) and inferior (IHLP) heads of the lateral pterygoid, the masseter, anterior temporal, posterior temporal and submandibular group of muscles, together with condylar movement, during contralateral and protrusive jaw movement. In most individuals, there was a progressive decrease in rectified and smoothed IHLP activity in relation to condylar movement during the return phase of contralateral and protrusive jaw movement. However, this pattern usually was not seen when SHLP activity was studied in relation to condylar movement. Further, there was a high correlation coefficient between condylar displacement and the rectified and smoothed IHLP and anterior temporal muscle activities during the return phase of contralateral or protrusive jaw movement, while SHLP presented a much lower correlation. For example, the mean (+/-SD) correlation coefficient between posterior condylar movement (along anteroposterior axis) and IHLP activity during the return phase of a protrusive jaw movement was -0.73+/-0.36 (for contralateral movement: -0.71+/-0.56), for the anterior temporal 0.69+/-0.21 (contralateral: 0.81+/-0.09), and for the submandibular muscles, -0. 77+/-0.15 (contralateral: -0.34+/-0.71). For the SHLP, masseter and posterior temporal, values were -0.34+/-0.61 (contralateral: -0. 48+/-0.37), -0.24+/-0.57 (contralateral: 0.16+/-0.80), and 0.16+/-0. 77 (contralateral: 0.64+/-0.14), respectively. These findings suggest an important role for the IHLP and anterior temporal in controlling the movement of the condyle to the glenoid fossa on the return phase of contralateral and protrusive jaw movements. Further studies are needed to clarify the function of the lateral pterygoid muscle during these and other jaw movements.     

下颌前突患者下颌支矢状劈开截骨术后髁突运动轨迹的改变

目的:研究双侧下颌支矢状劈开截骨术对下颌前突患者髁突运动轨迹的影响。方法:采用ARCUSdigma下颌三维运动轨迹描记仪,以髁突运动中心为参考点,研究30例正常受试者、14例下颌前突患者手术前后开口、前伸和左右侧向髁突运动的轨迹。用SPSSV11.0统计软件包进行配对t检验和成组t检验。结果:下颌前突患者术前、术后、正常组左侧髁突的运动轨迹与右侧基本相同,左侧髁突与右侧的开口、前伸和侧方运动范围无显著性差异(P>0.05)。术前组与正常组髁突运动轨迹差别较大,术前开口、前伸和侧方运动范围均小于正常组(P<0.05);术后与正常组髁突运动轨迹接近,术后开口、前伸和侧方运动范围与正常组无统计学差异;术前与术后组髁突运动轨迹差别较大,术前开口、前伸和侧方运动范围均显著小于术后组(P<0.05)。结论:下颌前突患者手术后,随着术后正畸治疗及咬合自我调整,建立了正常的咬合引导关系,使下颌功能运动趋向正常。     

Lateral pterygoid myotomy with reattachment to the condylar neck: an adjunct to restore function after total joint reconstruction

OBJECTIVE: The purpose of this study was to investigate the results of performing a lateral pterygoid myotomy with reattachment to the condylar stump to restore more normal function after total joint reconstructive surgery. STUDY DESIGN: Twenty-four joints were reconstructed in 14 patients with stock Christensen chrome-cobalt prostheses. Patients were separated into 2 groups. Group I consisted of 4 joints without reattached lateral pterygoid muscle (-LPM), and group II consisted of 20 joints with reattachment of the lateral pterygoid muscle to the condylar stump (+LPM). Patients were evaluated at an average of 15 months postoperatively to assess mandibular movement. Group I was compared with group II, and statistical analysis was performed through the use of the Mann-Whitney test. Patient satisfaction was evaluated by using postoperative questionnaires. RESULTS: Group II had an average interincisal opening 7.3 mm greater than Group I (P <.001). Lateral movements averaged 3.86 mm in Group II versus 0.5 mm in Group I (P <.05). Protrusion was 2.83 mm greater in Group II than in Group I (P = 0.53). CONCLUSION: The reattachment of the lateral pterygoid muscle to the condylar stump during total joint reconstructive surgery may provide the patient with greater interincisal opening, lateral excursions, and protrusive movement. The preliminary data from these small, nonrandomized groups are promising for improved function following total joint reconstruction.     

Investigation of a possible relationship between kinematic points and condylar attachments of the lateral ligaments

Kinematic points are proposed as reference for assessment of condyle motion. They are defined by coincidence between open-closing and protrusive trajectories. According to anatomical findings, this feature should also apply to the condylar attachment of the lateral ligament that should guide the condyle on an arc around its tubercular fixation. Our aim was to examine if evidence for a correspondence between the kinematic point and the condylar attachment of the ligament could be derived from condylar dynamics. In 60 asymptomatic volunteers, open-closing and protrusive jaw movements were recorded with 6 d.f. Kinematic points were found 2. 5+/-2.9 mm anterior and 4.3+/-2.9 mm inferior from the terminal-hinge point. Their coinciding traces could be fitted by arcs with radii of 11.7+/-2.2 mm. The centres of the arcs were found 10.4+/-1.6 mm anterior and 4.9+/-2.4 mm superior from the kinematic points. When compared to anatomy, the local distributions of kinematic points and arc centres corresponded well to the condylar and tubercular fixation areas of the ligament. The findings provide circumstantial evidence for a correspondence between kinematic points and the attachment of the lateral ligament. Kinematic points could provide a better means to assess condyle motion than other posterior landmarks, when in addition, movements of adjacent points and rotational properties are considered.     

A preliminary study of the effects of tooth guidance on working-side condylar movement

Clinical observations have indicated that lateral working-side tooth contacts can produce a posterior shift of the working-side condyle, resulting in pain in the temporomandibular joint. This study examined the influence of lateral retrusive and lateral protrusive tooth guidance on the movements of working condyles of the lateral pole. Four patients with lateral retrusive natural tooth contacts and four patients with lateral protrusive natural tooth contacts were studied. Movement of the lateral pole of the working condyle was recorded under the following conditions: (1) natural teeth in contact, (2) wearing of a mandibular acrylic resin splint that created lateral protrusive or lateral retrusive tooth guidance, and (3) a central bearing screw and bearing plate separating the teeth. The results indicated that the condition of the patient's temporomandibular joints was a crucial factor in consistency of condylar tracings. Condylar tracings from patients with temporomandibular joint condyle-disk lacking coordination were inconsistent and unreproducible. Consistent, reproducible tracings for patients without condyle-disk disorders indicated that lateral retrusive guidance can cause a more posterior pathway of the lateral pole of the working condyle than lateral protrusive guidance. Future studies are necessary to establish the relationship between lateral tooth guidance and temporomandibular disorders.     

下颌偏斜患者下颌侧方运动时髁突的运动轨迹特征

目的 通过记录下颌偏斜患者的髁突运动轨迹，研究此类患者髁突运动的规律。方法 下颌偏斜患者31例（男性9例，女性22例），年龄12～26岁，平均18岁。使用CADIAX　Ⅲ型髁突运动轨迹轴图描计仪，记录并通过配对t检验和秩和检验分析患者下颌侧方运动时髁突的运动轨迹，并将其与患者下颌偏斜量进行多元线性回归分析。结果下颌偏斜患者下颌侧方运动时髁突的运动轨迹不对称，偏斜侧的运动位移大于非偏斜侧，差异有统计学意义（P＜0．01）；偏斜侧髁突的水平倾斜度小于非偏斜侧，差异有统计意义（P＜0．01）。随着偏斜量的增加，偏斜侧与非偏斜侧髁突的位移差距也相应增加，非偏斜侧髁突的位移相应减小，差异有统计学意义（P＜0．05）。结论下颌偏斜患者不仅颅面形态不对称，下颌侧方运动时髁突运动轨迹在长度、角度等方面也不对称，其与偏斜量有一定的相关性。     

Location of the hinge axis and the kinematic centre in asymptomatic and clicking temporomandibular joints

The study aimed to compare the locations of the hinge axis and the kinematic centre in both clicking and non-clicking TMJs. The six degrees of freedom optoelectronic jaw movement recording system OKAS-3D was used to record open/close movements in 10 asymptomatic subjects and 30 subjects with a clicking joint. Movement paths of the hinge axis and the kinematic axis were calculated. A t-test was used in the analysis of the locations of the two condylar movement reference points. Variances between the values of the hinge and the kinematic axes were compared with the F-test. Locations of the hinge axis and the kinematic centre on the average did not differ significantly for the asymptomatic subjects at the group level (P>0. 05), while individually the locations differed 4.96 mm on the average. The difference between the hinge axis and the kinematic axis was significant for the group of subjects with clicking joints (P<0.01), with the average individual level difference of 9 mm. Variances differed significantly between the coordinates of the hinge and the kinematic axes between the two groups of subjects (P<0. 01). The study shows the importance of the choice of a condylar movement reference point for the study of condylar movements and suggests the use of the kinematic centre in such studies.     

骨性Ⅲ类正颌手术前后髁突运动对称性分析

目的测量骨性Ⅲ类错患者正颌手术前后髁突下颌边缘运动的对称性,探讨成人骨性Ⅲ类错患者正颌术后髁突运动功能的恢复情况。方法选取成人骨性Ⅲ类错患者15人,分别在术前、术后6个月、术后9个月,运用下颌三维超声定位技术.ARCUSdigma系统对最大张口和前伸运动时两侧髁突对称性进行分析。结果下颌最大张口和前伸运动时,骨性Ⅲ类患者术前和术后6个月组的双侧髁突运动轨迹在冠状向上不一致,差异有统计学意义(P0.05);术后9个月组双侧髁突三维方向的运动轨迹均较好,与术前相比无统计学差异(P0.05)。结论成人骨性Ⅲ类错患者正颌术后9个月时下颌功能性运动逐渐趋于正常,提示应将正颌手术后正畸时间保持在9个月以上。     

The influence of canine guidance and condylar guidance on mandibular lateral movement

summary This Study investigates the definite influence of the working-side canine and balancing-side condylar guidances on mandibular lateral movement. Lateral movements were measured on 40 young adults (22 males and 18 females), using the three-dimensional mandibular movement analysing system. The inclinations of the paths were calculated on the working-side canine, incisor, balancing-side first and second molars and balancing-side condylar points in the frontal plane. Multiple regression analysis enabled quantitative evaluation of the influence of the canine path and condylar path on the path of each tooth. The canine path showed greater influence than the condylar path even on the balancing-side second molar path. There was no difference between male and female subjects in the influential ratio of the canine guidance to the condylar guidance on any tooth path. It was concluded that the influence of the anterior and posterior guidance on the lateral movement varied according to the type of tooth, but not to the gender of the subject. This functional characteristic was confirmed by the morphological finding that the relative location of the molars in relation to canine and condyle does not differ between the sexes. The difference in the guiding system between the protrusive and lateral movement is also described in this paper.     

The influence of anterior guidance and condylar guidance on mandibular protrusive movement

summary This Study reveals the influence of the incisal and condylar guidance on mandibular protrusive movement. The protrusive movements were measured on 54 young adults (27 females, 27 males) using a three-dimensional mandibular movement analysing system. The inclinations of the sagittal paths on the incisor, canine, 1st molar, 2nd molar and condylar points were calculated, and multiple regression analysis was performed to evaluate the influence of the incisal and condylar paths on the path of each tooth quantitatively. The influence of the incisal path on any tooth path was consistently greater than that of the condylar path. The condylar path had a greater influence on the paths of posterior teeth than on the paths of anterior teeth, especially in the female subjects. The influence of the condylar path on the molar paths was twice as great in the female than that in the male subjects. It was concluded that the influence of the incisal and condylar guidance on the protrusive movement path varies according to the kind of tooth and the gender of the subject. These guiding system characteristics were confirmed by morphological analysis.     

Clinical comparison between arthrocentesis and conventional conservative treatment with maxillomandibular fixation for unilateral high condylar fractures

This study aimed to compare the effects of arthrocentesis and conventional closed reduction for unilateral mandibular condyle fractures. A total of 30 patients with unilateral condylar fractures were evaluated. Patients with a high condylar fracture and magnetic resonance evidence of joint effusion (JE) were divided into two groups: those treated with intra‐articular irrigation and betamethasone injection (group I) and those given conservative treatment and rigid maxillomandibular fixation (MMF) (group II). All patients were assessed for mandibular range of motion (ROM), protrusive movements, lateral excursion movements on the fractured and non‐fractured sides, pain in the temporomandibular joint and malocclusion, both before and after treatment. There were no significant differences in regard to protrusion, lateral excursion movement and incidence of malocclusion at 12 months after treatment between the groups (P > 0·05). In group I, ROM and joint pain showed good improvement from the early stages of treatment, and those patients had better outcomes as compared to group II for those parameters at 1 and 3 months after injury. The present findings indicate that arthrocentesis may be more effective and provide faster healing than conventional closed reduction.     

Influence of tooth contact on the path of condylar movements.

The correlation between condylar inclination and tooth guidance was tested by comparison of recordings of condylar movement in right and left parasagittal planes during lateral excursion, opening, and protrusive movements in 13 subjects with temporomandibular joint (TMJ) clicks and 15 subjects without TMJ clicks. The characteristic tracing of mandibular movements at the condyle with tooth-guided versus non-tooth-guided conditions were investigated by use of a computerized Axiograph graph. The generated tracings of each subject were graphed and analyzed to calculate the horizontal condylar inclinations as related to the axis orbital reference plane. Information from a standardized questionnaire provided evidence of a definite correlation between the presence of TMJ clicking and a specific prior medical event (tonsillectomy). The data from computerized tracings of all subjects revealed no significant difference (p 0.05) in the mean angles of condylar guidance at any of the millimeter intervals examined regardless of whether the craniomandibular contact was an articulation of natural teeth or an articulation of maxillary natural teeth against a tray clutch. These results do not suggest that dynamic interarch tooth guidance or the change in vertical dimension reflect a significant alteration in the recordings of condylar guidance in clicking or nonclicking groups.     

The intra-articular distance within the TMJ during free and loaded closing movements

Previous studies on free opening and closing movements of the mandible have demonstrated that the opening movement traces of the condylar kinematic center (i.e., the condylar point for which the protrusive and the opening movement traces coincide) lie closer to the articular eminence than the closing traces. This indicates the presence of an intra-articular distance within the joint during free closing. Since the mandible behaves like a class III biomechanical lever, a counteracting mechanical load on the mandible during closing will press the condyle-disc complex against the articular eminence. Therefore, in this study the hypothesis was tested that the difference between opening and closing movement traces of the kinematic center is reduced when the closing movements are counteracted by a mechanical load. From 10 healthy participants, 20-second movement recordings were obtained by a six-degrees-of-freedom opto-electronic jaw movement recording system (OKAS-3D) for three types of movements: (1) free opening and closing movements, (2) free opening and loaded closing movements (i.e., the participants closed against a small or high manually applied downward-directed force to the chin), and (3) gum chewing. Off-line, the opening and closing movement traces of the kinematic center were reconstructed, and the average difference between the traces (the intra-articular distance) was calculated. The average intraarticular distance was significantly smaller during loaded closing than during free closing, whereas no significant differences were found in the intra-articular distances between the loaded situations of low and high manual loading and contralateral chewing (ANOVA and post hoc Bonferroni multiple comparisons of means test, p<0.005). In conclusion, loading of the mandible during closing movements reduces the intra-articular distance within the temporomandibular joint.     

骨性III类错畸形患者正颌手术前后下颌运动轨迹变化的初步研究

目的:应用下颌运动轨迹仪评价骨性III类错牙合畸形患者正颌手术前后下颌运动的变化。方法:对15例骨性III类错牙合畸形需正颌手术病例和20例正常牙合对照组,采用ARCUSDigma下颌运动轨迹仪测定受试者最大开口运动,前伸及左右侧边缘运动距离,记录由计算机通过切牙运动模拟的双侧髁突的运动轨迹间的最大差数(MRC)。通过自身比较以及与对照组比较,评价患者在术前、术后3个月及6个月时下颌运动的变化以及髁突运动的对称性。采用团体t检验和配对t检验进行统计学处理。结果:术前患者除开口度外,其他运动距离均小于对照组,前伸运动差异显著(P<0.05);开口时MRC值大于对照组(P<0.05)。术后3个月时,开口度及左侧运动距离下降,前伸和右侧运动略有增加;MRC呈上升趋势。术后6个月时,下颌运动距离均有所增加,除开口度外其余均超过术前水平,与对照组无统计学差异;MRC小于术前水平且与对照组差异无显著性。结论:骨性III类错牙合畸形患者下颌运动水平与正常牙合存在差异,髁突运动对称性较差。正颌手术能够有效地改善患者的下颌运动功能。