|Year : 2012 | Volume
| Issue : 1 | Page : 122
|Comparative evaluation of condylar position in symptomatic (TMJ dysfunction) and asymptomatic individuals
Soumya Padala1, Sridevi Padmanabhan1, Arun B Chithranjan2
1 Division of Orthodontics, The Ohio State University, Columbus, Ohio, USA
2 Department of Orthodontics, Faculty of Dental Sciences, Sri Ramachandra University, Porur, Tamil Nadu, India
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|Date of Submission||25-Feb-2011|
|Date of Decision||26-Jul-2011|
|Date of Acceptance||21-Jan-2012|
|Date of Web Publication||26-Jul-2012|
| Abstract|| |
Context: The etiopathogenesis of temporomandibular joint (TMJ) disorders has been attributed to multiple factors and, while the importance of centric relation (CR) has been acknowledged in dental literature, the role of condylar position and CR-CO (CO-centric occlusion) discrepancy in TMJ dysfunction (TMD) has been a source of controversy.
Aim: To establish the relationship between condyle position and TMD.
Setting and Design: This was a case-control study to evaluate condylar displacement and interarch CR-CO discrepancy in symptomatic subjects (with TMD) and compare them with asymptomatic subjects.
Materials and Methods: Forty subjects were screened for TMD based on Helkimo index and grouped into asymptomatic and symptomatic groups. CR was registered using the modified Roth power centric bite registration after neuromuscular deprogramming. Models thus mounted on an Advanced Dental Design (AD2) articulator were evaluated for interarch CR-CO discrepancy. The condylar position discrepancy was recorded on a device MCD (measured condylar deviation).
Statistical Analysis: The Student's t test was used to test statistical significance. The paired t test and the unpaired t test were used for comparing results within and between the groups. Pearson correlation coefficient was used to find out the correlation between MCD measurements and dental three-dimensional (3D) model analysis measurements. The Chi-square test was used to evaluate the qualitative data.
Results: The average vertical and horizontal condylar displacements were significantly greater in the symptomatic group than in the asymptomatic group. There were significant deviations at the level of the occlusion in both groups.
Conclusion: Condyle position may play a significant role in the etiopathogenesis of TMJ disorders.
Keywords: Centric relation, CR-CO discrepancy, functional occlusion
|How to cite this article:|
Padala S, Padmanabhan S, Chithranjan AB. Comparative evaluation of condylar position in symptomatic (TMJ dysfunction) and asymptomatic individuals. Indian J Dent Res 2012;23:122
The temporomandibular joint (TMJ) is one of the most complex joints in the body, and the normal functioning of the masticatory system depends on its harmonious functioning.  Muscle action is a determinant of both the vertical and horizontal position of the condyle in the glenoid fossa. Harmony is established by coordination between occlusion, muscle, and joint. 
|How to cite this URL:|
Padala S, Padmanabhan S, Chithranjan AB. Comparative evaluation of condylar position in symptomatic (TMJ dysfunction) and asymptomatic individuals. Indian J Dent Res [serial online] 2012 [cited 2013 Dec 8];23:122. Available from: http://www.ijdr.in/text.asp?2012/23/1/122/99060
There are two important reasons why condylar position may be of interest. First, it has been suggested that condylar position may be related to dysfunction of the gnathic system ,, and, secondly, condylar position can have a very dramatic effect on the position of the mandibular corpus which, in turn, can significantly affect diagnosis and treatment in various disciplines of dentistry. 
Centric relation (CR) position has been defined by the Glossary of Prosthodontic Terms as 'a maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective disks, with the complex in the anterior-superior position against the slopes of the articular eminences.  Okeson, has described CR as the orthopedically and musculoskeletally stable position of the mandible  and Moffet provided histological evidence to show how the structures of the joint were designed to withstand heavy loads with the condyles in the CR position. 
It is desirable for the maximum intercuspation [centric occlusion (CO)] position to coordinate with the CR position, and restorative dentists who have successfully used the concept of CR as a desirable treatment goal assert that there is a relationship between unfavorable condylar position, as determined by the occlusion, and temporomandibular joint dysfunction (TMD).  In orthodontic treatment also it has been stressed that the goal of orthodontic treatment must be to adapt the teeth to joints and not to adapt the joints to the teeth.  Hidaka,Roth and Cordray and others have also stressed on the importance of orthodontists aiming for functional occlusion where CR and CO coincide. ,,
The American Dental Association and the American Academy of Craniomandibular Disorders have concluded that two-dimensional (2D) radiographs are insufficient to assess condylar position for diagnostic purposes.  In the recent past, three-dimensional (3D) imaging has been used to evaluate condylar position.  However, this is expensive and not possible in all cases. The condylar axis can also be influenced by the occlusion, and instrumentation such as the SAM® articulator, which uses the mandibular position indicator (MPI), or the Pandent® articulator, which uses condylar position indicator (CPI), enable the clinician to determine, record, and compare the positional changes of the condyle between CR and CO in all three spatial planes; , the accuracy and repeatability of the technique has been confirmed. ,
The etiology of TMD continues to be an unresolved controversy. It is believed to be multifactorial and the contribution of occlusal factors is said to be in an associational context and not necessarily cause and effect. Very few studies have evaluated the CR-CO discrepancy in a group with TMD and compared it to an asymptomatic group. 
The aim of this study was to:
- Statistically evaluate the 3D nature and extent of condylar displacement between SCP (Seated condylar position)/CR and MIC(Maximum intercuspation)/CO in symptomatic subjects (with TMD) and compare them with asymptomatic subjects in order to establish a relationship between condyle position and its role in etiopathogenesis of TMJ disorders.
- To statistically evaluate and compare the 3D nature of dental interarch displacement in the above subjects between SCP/CR and MIC/CO.
- To establish the correlation between condylar displacement and dental interarch displacement.
| Materials and Methods|| |
All patients reporting to the Department of Orthodontics, Sri Ramachandra Dental College, Porur, India, between the ages of 15 and 35 years were screened for TMJ dysfunction. The preliminary screening included the following:
Patients having at least one or more of the following signs and symptoms: Muscle contraction headache, facial muscle pain, muscle fatigue, limited range of motion, pain, noise, or locking in the joints, pain upon movement, parafunction (clenching, grinding), occlusal attrition, and a modified Helkimo index score ≥1 were considered as having potential TMD.
- Written medical and dental histories
- Clinical examination
- Modified Helkimo index 
- Maxillary and mandibular models
- Radiographs (OPG/TMJ tomograms).
The control group (group B) consisted of 20 patients without TMD; the above symptoms were absent and therefore these subjects had a modified Helkimo index score ≤1.
The mean age in group A was 24.5 years and in group B it was 23.4 years.
The articulator system used was the Advanced Dental Design (AD2) articulator, which is modeled on the Panadent® system. After facebow transfer, the patient was prepared for the modified Roth power centric bite registration. All patients were neuromuscularly deprogrammed at the chair before registration of the SCP/CR by asking them to bite continually with a moderate pulsating biting force (5 seconds clench, 5 seconds relax) on a wooden tongue depressor for 5-10 min.
The power centric registration , refers to the use of the patient's power closure muscles (masseter, medial pterygoid, and superior head of the lateral pterygoid) to seat the condyles as closely as possible to CR, with the condyles centered transversely and seated against the articular disks at the posterior slope of the articular eminences, without dental interferences.
This dual bite registration was taken in two sections (anterior and posterior) using DeLar® blue wax (DeLar Corp., Lake Oswego, OR). The centric occlusion (CO) or habitual occlusion wax bite registration was made with a single layer of dead-soft pink Moyco® wax (Great Lakes Orthodontics, Tonawanda, NY) [Figure 1].
Another accessory of the AD2 articulator is the MCD (measured condyle deviation), which records in all three planes of space the position of the condyle in CR and when the teeth are in maximum intercuspal position (MIP) or centric occlusion (CO). This procedure is called CPR (condyle position recording) [Figure 2]. In CPR, the condylar distraction in vertical, horizontal, and transverse planes was measured on millimeter graphs to the nearest 0.25 mm using a digital caliper [Figure 3].
|Figure 3: CR-CO discrepancy in horizontal ,vertical and transverse directions measured in mms|
Click here to view
This was followed by 3D model analysis. The initial premature occlusal contact in the SCP/CR was marked with blue-colored articulating paper, and the following parameters were measured to the nearest 0.1 mm with a digital caliper in the SCP/CR and MIC/CO: (1) horizontal: Overjet and Angle classification at first molar, right and left; (2) vertical: Overbite; (3) transverse: Dental midline.
The Student's t test was used to test statistical significance. The paired t test was used for comparing results within the group, and the unpaired t test was used to compare the results between the groups. Pearson correlation coefficient was calculated to assess correlation between MCD measurements and dental 3D model analysis measurements (overjet, overbite, Angle classification, and dental midline). The Chi-square test was used to evaluate statistical significance of the qualitative data.
The data are presented as the mean and standard deviation (SD). Analysis was performed using SPSS® (Statistical Package for Social Sciences). Statistical significance was at P≤.05.
| Results|| |
Examination of each subject's casts marked for the initial contact in the SCP/CR revealed that in 15 out of 20 asymptomatic subjects (75%) the premature occlusal contact occurred on the posterior-most tooth, while 19 of the 20 symptomatic subjects (95%) had a premature occlusal contact on the posterior-most tooth. The Chi-square test showed that this difference was not statistically significant (P=.07652).
In 17/20 (85%) asymptomatic subjects and 18/20 (90%) symptomatic subjects overjet was larger in the SCP/CR as compared to MIC/CO. The mean overjet difference from CR to CO in asymptomatic subjects was 0.65 ± 0.80 mm and 0.88 ± 0.92 mm in symptomatic subjects; this difference was not statistically significant (P=.413). The change in overjet between CR and CO within the same group was statistically significant; however, the mean difference between the groups was not.
In 16/20 (80%) asymptomatic subjects and 19/20 (97.5%) symptomatic subjects, overbites were smaller in the SCP/CR as compared to MIC/CO. In two (5%) asymptomatic subjects overbite remained unchanged and in two (5%) asymptomatic subjects overbites increased in SCP/CR. In 1/20 (2.5%) symptomatic subject overbite increased in SCP/CR.
The mean overbite difference from CR to CO was -0.93 ± 1.27 in asymptomatic subjects and -1.02 ± 1.28 in symptomatic subjects; the difference between the two groups was statistically nonsignificant (P=.808).
Horizontal AP model analysis
A change in Angle classification at the first molar between the SCP/CR and MIC/CO was seen in 5/20 (25%) of the asymptomatic subjects and in 7/20 (35%) of the symptomatic subjects.
Dental midline differences
The dental midlines were coincident at CR and CO in 15/20 (75%) asymptomatic subjects and in 10/20 (50%) symptomatic subjects. The Chi-square test showed P value of .60653, which is statistically nonsignificant. The mean midline shift from CO to CR in asymptomatic subjects was 0.89 ± 0.55 mm and 0.96 ± 0.65 mm in symptomatic subjects (P=.751; statistically nonsignificant).
Condylar position analysis
The mean horizontal displacement of 40 condyles in the asymptomatic group was 0.82 ± 0.49 mm, whereas it was 1.51 ± 1.41 mm in the symptomatic group. This difference was statistically significant (P=.004).
The mean vertical displacement of 40 condyles was 0.7 ± 0.51 mm in asymptomatic subjects and 1.18 ± 1.23 mm in symptomatic subjects. This difference was statistically significant (P=.001).
The mean transverse condylar displacement in the asymptomatic subjects was 0.61 ± 0.38 mm, whereas it was 0.96 ± 0.89 mm in symptomatic subjects. The difference between the two groups was not significant (P=.058). In 10/20 (50%) of asymptomatic subjects and in 11/20 symptomatic subjects the displacement was towards the left.
| Discussion|| |
Although TMD is said to be multifactorial in origin, the importance of occlusion and its relationship to the prevalence of TMD has been a source of controversy.
To accurately study the dental interarch and condyle positional changes between MIC/CO and the SCP/CR, it is important to use a method that reduces or eliminates the influence of the occlusion on the musculature. A number of studies have shown that the neuromusculature positions the mandible to achieve maximum intercuspation, regardless of the position of the condyles. ,,,,, The constant repetition of the proprioceptive trigger receptors to the muscles cause them to become patterned to the deviated closure, and these memorized patterns of muscle activity are called muscle splinting or 'engrams.' The resultant muscle function can be so dominant that the acquired mandibular position (the occlusion-dictated condylar position) will often be mistaken by the clinician for the seated condylar position. Neuromuscular deprogramming is the key to reproducibility so that the condyle can be accurately seated. ,,,,
While the patient's own masticatory musculature may be used to seat the condyles in the desired position, Dawson  advocated that the patient be made to bite on cotton rolls for deprogramming prior to registering the SCP/CR. Karl and Foley  found that although there was an 18% chance of detecting measurement of more than 2 mm in either the horizontal or vertical direction with the Roth registration technique alone, this figure more than doubled to 40% with the addition of a hard anterior deprogramming appliance before registration of the SCP/CR. Cordray  reported that 5-10 minutes of chairside deprogramming with a hard tongue blade can be effective for initial deprogramming. Therefore, in this study, subjects were neuromuscularly deprogrammed by having them bite continually with a moderate pulsating biting force on a wooden tongue depressor for 5-10 minutes. The registration technique advocated by Roth was employed, which uses a two-piece wax bite with a hard anterior stop to achieve condylar seating; the inter-rater and intra-rater reproducibility of this technique has been previously established. ,
The AD2 articulator designed by Dr. Robert Williams was used in this study; like other articulators, it reproduces the border mandibular movements with 3D curved path analogs of motion that include lateral border, protrusive, and curved path Bennett pathways.
The MCD used in the AD2 system is similar to that of the Panadent® , and it was used in this study. Hick  compared the SAM® and Panadent® articulator systems and concluded that there was no statistical difference between the recordings obtained using the two articulators.
Three-dimensional evaluation of the models showed that in most of the subjects in both groups premature occlusal contact was on the posterior-most tooth, which is in agreement with previous studies. ,,,, Okeson  has described how a premature posterior contact can cause the condyle to displace from the disc as the mandible pivots from this premature occlusal contact and moves into maximum intercuspation. The body of the mandible and the mandibular dentition move upward and forward from the initial premature occlusal contact in the SCP/CR to MIC/CO. Thus detection of this premature occlusal contact is vitally important for diagnosis.
Dental midlines were coincident at CR and CO in 75% of asymptomatic subjects and in 50% of symptomatic subjects. While this was statistically nonsignificant, it could be clinically significant as it reflects a mandibular shift from the SCP/CR to accommodate the maximum intercuspation bite. In group A, the number of subjects in whom changes in Angle classification was observed, was slightly more (35%) than number of subjects in group B (25%).
Overjet increased in both the groups in SCP/CR than in MIC/CO; however, the mean overjet difference between the two groups was statistically nonsignificant. Overbite reduced in both the groups in SCP/CR than in MIC/CO, but the mean overbite difference from CR to CO between the two groups was statistically nonsignificant [Table 1]. This has also been documented in previous studies ,,,, and is an important factor in determining whether treatment options will include extractions or orthognathic surgery.
|Table: 1 Paired Student's t Test - Intragroup comparisons of interarch displacements between CR and CO|
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The SCP/CR position of the condyles and the MIC/CO position of the condyles were found to be different in almost every subject in this study; similar findings have also been reported by other authors. ,,,
The mean horizontal displacement and the mean vertical displacement in the symptomatic group was significantly greater than in the asymptomatic group; however, the mean transverse displacement was not statistically significant [Table 2]. The average horizontal and vertical displacement in both the groups was acceptable according to previously established normal parameters ,, [≥1.6 mm in the horizontal (AP) plane, ≥2.0 mm in the vertical plane (SI), and >0.5 mm in the transverse (ML) plane]. However, a significant point was that the magnitude of the horizontal (AP) or vertical (SI) discrepancy was found to be ≥2 mm in 20% of the asymptomatic sample while it was 45% in the symptomatic subjects. This is larger than that noted in the studies of Hidaka  who reported that 16% of subjects showed ≥2 mm AP (horizontal) or SI (vertical) displacement and Utt  who reported that 19% showed ≥2 mm AP (horizontal) or SI (vertical) displacement.
|Table: 2 Unpaired Student's t Test - Comparisons of interarch displacements and condylar displacements between CR & CO|
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A statistically significant positive correlation was observed between horizontal condylar displacement and the overjet difference at CR and CO. However, no other significant correlations were noted between condylar displacement and dentoalveolar changes.
In a significant number of orthodontic cases, the decision-making process would be affected by an articulator mounting in the seated condylar position due to the presence of a significant condylar displacement and the resulting change in the 3D dental interarch relationships. Shildkraut  proved that discrepancies of this magnitude produced a strong statistically significant difference in 21 of the 24 cephalometric measurements investigated causing differences in mandibular position.
| Summary and Conclusion|| |
- Condylar displacements in the horizontal and vertical directions were greater in the symptomatic group than in the asymptomatic group and this was statistically significant. This was not true for transverse deviations.
- Deprogramming and mounting models in the SCP/CR revealed significant deviations at the level of the occlusion as evidenced by posterior premature occlusal contacts, increased overjet, decreased overbite, and midline and Angle's classification deviations in both the groups. Although the dental interarch discrepancy in the SCP/CR was greater in the symptomatic group when compared to the asymptomatic group, this was not statistically significant.
- A statistically significant positive correlation was observed between horizontal condylar displacement and the overjet difference at CR and CO. However no other significant correlations were noted between condylar displacement and dentoalveolar changes.
The findings of this study indicate that recording and evaluating the CR-CO discrepancy in individuals presenting with signs and symptoms of TMD may reveal significant dental inter-arch discrepancies and condylar displacements of significant magnitude. While orthodontists might not find it practical to mount diagnostic models in all cases, it might be advisable in patients with signs and symptoms of TMD.
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Division of Orthodontics, The Ohio State University, Columbus, Ohio
[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2]
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