Radiographic study of condylar position in centric relation and centric occlusion

The present study was conducted to compare the spatial relationship of the condyles to their fossae in the centric occlusion and centric relation positions. Right and left TMJ radiographs were obtained on 40 young adults in the two positions. Direct measurements of the anterior, posterior, and superior spaces between the condyles and their fossae were made on the radiographs. Results were statistically analyzed; the following findings and conclusions were derived: (1) In the centric relation position, both condyles were placed more posteriorly and superiorly in their fossae than in the centric occlusion position. (2) In the centric occlusion position, both condyles were symmetrically placed in their fossae with equal spatial distances anteriorly and posteriorly. (3) Greater spatial differences existed between the centric occlusion and centric relation positions on the left side, which was the orbiting (balancing) side in most subjects. (4) Further studies are needed to develop a more physiologic approach for correctly relating the mandible to the maxillae when reconstructing the occlusion in both dentulous and edentulous patients.     

The difference in condylar position between centric relation and centric occlusion in pretreatment Japanese orthodontic patients

This study investigates the differences in condylar position between centric relation (CR) and centric occlusion (CO) in Japanese orthodontic patients before treatment. We employed 150 consecutive cases (age range: 6-57 years) for the study. Dental casts were mounted on a Panadent articulator with a power centric CR bite record. The differences in condylar position between CR and CO in all three spatial planes were measured using the Panadent Condyle Position Indicator (CPI). The subjects were divided into groups by age, gender, mandibular plane angle or angle classification. No significant differences in the magnitude of CPI measurements were found among the groups. The three-dimensional distances of condylar displacement on both sides were almost identical, and the superoinferior displacement (S-I) was greater (P < .0001) than the anteroposterior displacement (A-P). The S-I was greater (P = .02) on the left side than on the right side, while the A-P displacement was smaller (P < .0001) on the left side than that on the right side. Significant condylar displacement (2.0 mm for S-I and A-P, 0.5 mm for the lateral displacement, L) was found frequently in L (31.3%), S-I, and A-P, in that order. Fifty-eight (38.7%) of the subjects had significant displacement in L, S-I, or A-P. Moreover, Angle Class III subjects tended to have significant condylar displacement toward the left side. The results suggest that orthodontists should be aware of a high incidence of condylar displacement in Japanese orthodontic patients and measure condylar displacement before the start of comprehensive orthodontic treatment to unmask real jaw relationships and avoid possible misdiagnoses.     

Telemetric comparison of centric relation and centric occlusion reconstructions

Two complete fixed prostheses built with the occlusion in centric relation and with occlusion in the subject's existing centric occlusal position were tested with telemetry under conditions of actual use. The findings indicate that the subject did not use the centric relation position but accepted the prosthesis built to her preexisting centric occlusion. These findings are consistent with our previous results of telemetric studies conducted on patients with three-unit fixed prostheses.     

Movement between centric relation contact position and the intercuspal position.

Casts of 42 patients free from temporomandibular joint problems were mounted on an articulator in centric relation contact position. The movement of the horizontal axis of rotation was measured when the casts were moved from centric relation contact position to the intercuspal position. Measurements of the vertical and horizontal movements of the incisal pin were also made during this movement. There was a highly significant correlation between the movement of the horizontal axis in the horizontal plane and the ratio of vertical to horizontal movement as measured at the incisal pin. The greater this ratio was, the smaller the horizontal movement of the axis was; the smaller the ratio (the larger the horizontal component) was, the larger was the horizontal movement of the axis. The clinical implications are discussed.     

Variability of centric relation position in TMD patients

Reproducibility of the centric relation position for patients with temporomandibular disorders (TMD) is not documented in the current literature. It was the objective of this study to assess clinical variability of the centric relation position for TMD patients with a muscle-determined technique by means of an anterior deprogramming device, the leaf gauge. A sample of 60 patients with signs of TMD was selected, 8 men (Mean age 28,6, SD 5,2) and 52 women (Mean age 30,5, SD 10,1). All patients were examined with the Research Diagnostic Criteria, including pain on movement and/or function, mouth opening, joint sounds and palpation of masticatory muscles. All 60 patients were allocated to one of the following diagnostic subgroups: myofascial pain, disk displacement with reduction, disk displacement without reduction, osteoarthritis, trauma. Twelve control subjects were taken from a previous study. Three sequential centric relation records were taken; the first one was used to mount a set of casts to an articulator. Criteria of precision were formulated beforehand: 2 out of 3 centric relation records had to be identical in a split-cast procedure. Variables XL and XR represented mandibular displacement in the sagittal plane, variables YL and YR in the transversal plane, and ZL and ZR in the vertical plane, on the left and right condylar level respectively. Variables XMIN, YMIN and ZMIN represented the minimal sagittal, transversal and vertical displacement left or right respectively. Likewise, variables XMAX, YMAX and ZMAX represented the maximal sagittal, transversal and vertical displacement left or right. XDIFF, YDIFF and ZDIFF represented the difference between the minimal and maximal values of X, Y and Z. The diagnostic subgroup trauma was excluded, because there was only one patient. The null-hypothesis of no between-group differences in within-subject and total variability was tested with an analysis of variance (ANOVA). The level of significance was set at 0.05. To minimize type I errors caused by multiple testing Scheffe's test was used to maintain an overall significance of 0.05. No significant difference between patients and control subjects could be found for variables XL, XR, YL, YR, ZR and ZL. Variables XMIN, YMIN, ZMIN, XMAX, YMAX, ZMAX, XDIFF, YDIFF and ZDIFF showed no significant differences. Scheffe's testing for the variables XL, XR, YL, YR, ZL and ZR, as well as the variables XMIN, YMIN, ZMIN, XMAX, YMAX, ZMAX, XDIFF YDIFF and ZDIFF showed no significant differences. The results of this study suggest no variability in centric relation position between TMD-patients and control subjects by means of the leaf gauge.     

Laminagraphic study of mandibular condyle position when recording centric relation.

Laminagraphs were made of each temporomandibular joint of 20 subjects (1) with the mandible forcefully retruded to centric relation and (2) with the mandible positioned by a closing force while an anterior guidance prosthesis was being used. The radiographs were compared by measurements of condylar position; results indicated the condyles to be significantly more superior in the glenoid fossa when anterior guidance was used. The difference in anterior-posterior positioning of the condyles appeared to occur randomly. Measurements of the joint spaces with the mandible in centric relation using anterior guidance indicated that mandibular condyles were not centered in the fossae. There seemed to be a range in the size of the space that could be considered normal.     

Reliability of a measuring-procedure to locate a muscle-determined centric relation position

Although reproducibility of centric relation position, determined with an anterior deprogramming device, a leaf gauge, is widely accepted among clinicians, data confirming statistical evidence are lacking in the current literature. The objective of this study was to prove clinical reliability of a measuring-procedure to locate the centric relation position, determined with the leaf gauge. A sample of 15 subjects (6 men, 9 women, age 22 to 46), assessed with the Research Diagnostic Criteria to rule out any TMD-signs, was selected. Three observers each took three sequential interocclusal records with the leaf gauge, to mount a set of casts into the centric relation position in an articulator. Out of 15 subjects, 12 (5 men, 7 women) fitted criteria of precision--three out of three interocclusal records for each of the three observers--in a split-cast procedure. The applied statistical method is an analysis of variance model (ANOVA) with two factors for 3 observers and 12 subjects. The variance components estimation procedure is MIVQUE (0). The a was set at 0.05. No significant difference between observers for the measured variables sagittally (XL, XR), transversally (YL, YR), and vertically (ZL, ZR) could be found. MIVQUE variance components estimates for observers is < 0, varies for subjects from 0.04 to 0.20 and varies for error from 0.12 to 0.25 mm. Reliability of a measuring-procedure to locate a muscle-determined centric relation position could be established satisfactory.     

无颞下颌关节症状成人最大牙尖交错位与正中颌位间髁突位移的测量

目的研究无颞下颌关节症状青年人最大牙间交错位及正中关系位下的髁突位移方向及大小。方法取得受试者的口腔工作模型、拍摄全口曲面断层及X线头颅侧位片,进行筛选及jarabak头影测量分析。取得病人最大牙尖交错位(MICP)咬合记录。取得病人正中关系位(CRP)咬合记录,使用AD2解剖式架记录上下颌位置。将工作模型自架转移至MCD,分别于左右及横向3个面打点记录MICP和CRP时髁突的位置,测量两种位置下的打点差异。统计受试者髁突位移数据并结合头影测量指标进行统计分析。结果 (1)MICP-CRP髁突位移量在矢向、垂直向及横向均呈正态分布,P>0.05。(2)以Roth生理范围为标准,有34.5%的受试者其MICP-CRP位移量在此范围内;未超过该范围(T0组)与超过该范围(T1组),两组头影测量指标之间未见差异(P>0.05)。(3)MICP-CRP双侧髁突位移在三维方向不一致的比例约为31.1%;MICP-CRP方向一致者(TC)与不一致者(TD)头影测量指标之间未见差异(P>0.05)。(4)MICP-CRP双侧髁突位移量与头影测量指标的相关关系分析中(Pearson分析),L角、Go角与左侧髁突矢向位移量存在正相关关系(r=0.385,r=0.467);后前面高比与左右两侧垂直向位移量同时存在负相关关系(r=-0.442,r=-0.380)。结论由于无TMD症状人群口颌系统功能评价标准不能完全确定,因此研究对象存在假阴性的可能。研究结论与以往相关研究的不同提示我们口颌系统生理代偿机制个体巨大的差异性。