05 October 2024: Clinical Research
Anterior Disc Displacement and Cortication Patterns in the Temporomandibular Joint
Sedef Kotanli1ACE*, Menduh Sercan Kaya1BEDOI: 10.12659/MSM.945967
Med Sci Monit 2024; 30:e945967
Abstract
BACKGROUND: Anterior reduction disc displacement (ARDD) of the temporomandibular joint (TMJ) can present with pain and clicking of the jaw when chewing. This study aimed to evaluate the relationship between articular eminence cortication (AEC) and mandibular condyle cortication (MCC) in 81 patients with ARDD of the TMJ using cone beam computed tomography (CBCT) imaging.
MATERIAL AND METHODS: We examined images of 142 patients who applied to the outpatient clinic between 2022 and 2024 for various reasons and whose radiographic records included CBCT and MRI images. Sixty-one patients who did not meet the inclusion criteria were excluded from the study. MRI images of the remaining 81 patients were analyzed and evaluated for the presence of ARDD. Subsequently, all mandibular condylar processes and articular eminences included in the study were examined by CBCT and the degree of cortication was classified and noted. The relationship between MCC and AEC and ARDD was evaluated with the SPSS 23.0 program (SPSS, Chicago, IL, USA).
RESULTS: ARDD was observed in 46 (28.4%) of 162 condyles examined. Type 1 cortications were observed in 8 (17.4%), type 2 in 36 (78.3%), and type 3 in 2 (4.3%) of the condyles with disc displacement; 80.0% (8) of type 2 cortications were found in patients with ARDD (P<0.001), and 75.0% of type 3 cortication was observed in intact condyles (P<0.001).
CONCLUSIONS: This study shows that loss of AEC and MCC may be a significant factor in the diagnosis of ARDD, and decreased AEC and MCC may be a criterion for the diagnosis of ARDD.
Keywords: Mandible, Tomography, cortical bone, Joint Diseases
Introduction
The temporomandibular joint (TMJ), a symmetrical ginglymo-diarthrodial joint, is involved in deglutition, mastication, and speech. It is mainly composed of bony components such as the glenoid fossa of the temporal bone, the articular eminence and the condylar process of the mandibular bone, and a fibrocartilage disc [1,2]. The bony components of the TMJ, the articular eminence and the mandibular condyle, usually develop simultaneously. Cortical bone formation in the mandibular condyle begins at the age of 12–14 years and homogeneous and compact cortical bone can be observed in people aged 21–22 year old [3]. The development of the morphology of the condyle and articular eminence are compatible with each other. Therefore, it is expected that articular eminence cortication (AEC) and mandibular condyle cortication (MCC) are compatible [4]. MCC and AEC are parameters that allow the quality and density of the cortical bone surrounding the mandibular condyle and articular eminence to be categorized [4]. The articular disc, which contains dense fibrous connective tissue, allows for balanced distribution of the forces coming into the joint and ensures compatibility between the bony components of the TMJ (mandibular condyle and glenoid fossa) and divides the joint space into upper and lower compartments [2,5].
In a healthy condyle, the posterior band of the disc is located above or slightly in front of the condyle when the mouth is closed. Joint disorders can occur as a result of deviation of the disc from its proper position [5]. Disc displacement can cause partial or complete separation of the disc from the disc space at the condyle-disc junction [6]. When the mouth is closed, the articular disc is displaced anteriorly to the condyle head; when the mouth is opened, the disc is repositioned at the condyle head, as is normal. When the articular disc repeatedly fails to undergo reduction and causes limited mouth opening, the diagnosis of nonreducible disc displacement is made [6,7]. This deviation can occur medially, laterally, posteriorly, and anteriorly, and in combinations of these directions, but usually anteriorly [8]. In this case, if the posterior joint attachment of the disc is positioned anterior to the condyle when the mouth is closed and the disc is in its proper position when the mouth is open, this is called anterior reduction disc displacement (ARDD) [6,8]. In ARDD, the posterior disc attachment is positioned behind the condyle during mouth opening and a clinking sound is produced [7,8]. Disc displacements can be asymptomatic or symptomatic [8]. Studies have shown that 30% of asymptomatic patients have disc displacement [9]. Arthrography and magnetic resonance imaging (MRI) are used to examine the TMJ disc in detail. However, arthrography involves use of ionizing radiation and risk of allergy to contrast agents [8]. Therefore, MRI is the best standard method used in imaging to understand the position of the disc. The advantage of MRI is that it does not emit ionizing radiation, in addition to its high accuracy, sensitivity, and excellent anatomical detail in monitoring the position and structure of the disc [8,10,11]. However, since MRI is unable to provide a quality image in hard tissue examination, computed tomography (CT) and cone beam computed tomography (CBCT) are used when the bony components of the TMJ require monitoring. CBCT is more advantageous than CT in hard tissue imaging, with low cost, high resolution, and relatively low radiation doses [2,4,12].
Disc displacements are considered to differ from degenerative joint diseases because the quality of the structural components of the TMJ is not necessarily expected to change. To a certain extent, the TMJ tries to compensate for the forces acting on it, but if these forces can no longer be tolerated, regressive modeling (maladaptation) occurs [13]. Therefore, this study aimed to evaluate the relationship between articular eminence cortication (AEC) and mandibular condyle cortication (MCC) in 81 patients with anterior reduction disc displacement (ARDD) of the temporomandibular joint (TMJ) using cone beam computed tomography (CBCT) imaging.
Material and Methods
ETHICS APPROVAL:
This study was conducted retrospectively on the medical and radiologic records of patients who applied to Harran University Dentistry Oral Diagnosis and Maxillofacial Radiology Outpatient Clinic. Approval for the study was obtained from the Harran University clinical research ethics committee with the decision numbered 24.03.31. Informed consent was obtained from all patients in accordance with the Declaration of Helsinki.
INCLUSION AND EXCLUSION CRITERIA:
The images of 142 patients who applied to the outpatient clinic between 2022 and 2024 for various reasons and whose radiographic records included CBCT and MRI images were analyzed. Age, sex, and medical history information of the patients were obtained from hospital records. Images of 54 patients were excluded due to artifacts in the image, insufficient imaging area, presence of systemic diseases affecting the maxillae, incompatibility of the images with the imaging parameters, poor image quality, lack of information in the medical records, patient age below 22 years or above 31 years, and fracture lines, cysts, and tumors in the examined area.
MAGNETIC RESONANCE IMAGING (MRI) EVALUATION PARAMETERS:
Two maxillofacial radiologists evaluated the T1-weighted images (666/11 TR/TE) of the remaining 88 patients obtained with an MRI machine (Magnetom Skyra; Siemens Medical Solutions, Erlangen, Germany) with a field of view of 200×230, a matrix of 256×256, and a magnet power of 3.0 Tesla with 3-mm-thick slices in the open and closed positions. One radiologist had 8 and the other had 2 years of experience. The evaluations were repeated by 2 observers at 14-day intervals, and 7 images that could not be reconciled were excluded. Consequently, we included 31 patients with disc displacement with anterior, anteromedial, or anterolateral reduction and 50 healthy patients without any reduction of the articular disc.
CONE BEAM COMPUTED TOMOGRAPHY (CBCT) EVALUATION PARAMETERS:
CBCT images of 81 patients were obtained with a Castellini X-Radius Trio Plus dental tomography device (imola, ITALY) using 16 mAs and 90 kVp irradiation parameters and examined by 2 observers at 14-day intervals. CBCT images with a voxel size of 0.3 mm, a slice thickness of 1 mm, and a field of view (FOV) of 13×16 cm were evaluated for AEC and MCC on a full HD screen with a maximum screen resolution of 1920×1080 and a screen size of 15.6 inches using the IRYS viewer 15.1 software program and were recorded as follows.
CLASSIFICATION OF MANDIBULAR CONDYLE CORTICATION (MCC) AND ARTICULAR EMINENCE CORTICATION (AEC):
Classification of Mandibular Condyle Cortication (Figure 1):
Classification of Articular Eminence Cortication (Figure 2):
STATISTICAL ANALYSIS:
Cronbach’s alpha analysis was used to assess inter- and intra-observer correlations. The data obtained were evaluated with the SPSS 23.0 program (SPSS, Chicago, IL, USA). The compatibility of the variables with normal distribution was analyzed by Kolmogorov-Smirnov test. For parametric variables with normal distribution, the independent
Results
EVALUATION OF THE RELATIONSHIP BETWEEN ANTERIOR REDUCTION DISC DISPLACEMENT (ARDD) AND MANDIBULAR CONDYLE CORTICATION (MCC):
ARDD was observed in 46 (28.4%) of 162 condyles examined. Type 1, type 2, and type 3 MCC were observed in 8 (17.4%), 36 (78.3%), 2 (78.3%), and 2 (4.3%), respectively, of the condyles with ARDD. Type 1 MCC was not observed in condyles without ARDD. Type 2 MCC was observed in 87.8% of patients with ARDD and 12.2% in intact condyles. Type 3 MCC was detected in 1.8% of patients with ARDD. There was a significant association between MCC and ARDD (P<0.05) (Table 1).
EVALUATION OF THE RELATIONSHIP BETWEEN ANTERIOR REDUCTION DISC DISPLACEMENT (ARDD) AND EMINENCE CORTICATION (AEC):
Type 1 cortication was not found when AEC was evaluated, 80.0% (8) of type 2 cortications were found in patients with ARDD, and 75.0% of type 3 cortication was observed in intact condyles. A significant correlation was observed between AEC and ARDD (P<0.05) (Table 2).
Discussion
Disc displacement, defined as the disruption of the relationship of the TMJ disc with the articular eminence, condyle, and fossa, is one of the most common TMJ disorders [14]. The development of the condyle and articular eminence are parallel to each other, and the cortical volume of the condyle is associated with disc displacement [4,14]. In our study, we aimed to investigate the relationship between the degrees of MCC and AEC with ARDD and to investigate whether a preliminary diagnosis of disc displacement can be made according to the level of cortication loss, and we concluded that decreased AEC and MCC may be a criterion for the preliminary diagnosis of ARDD. To the best of our knowledge, there is no other study in the literature examining MCC and AEC in ARDD patients. Comparison of the degree of healthy and diseased MCC and AEC will provide a basis for the classification of normal and pathologic conditions.
Arthrography can provide very good images with which to determine the position of the TMJ disc. However, this method has the disadvantages of exposing the patient to high doses of radiation, being an invasive procedure, being expensive, and causing hypersensitivity reactions. Ultrasonography, which is a noninvasive and inexpensive method, cannot show the exact disc position. MRI, on the other hand, has the advantages of being noninvasive, showing the disc position accurately, and not exposing patients to radiation during imaging. Therefore, in this study, MRI images were used to assess the disc position [8,10,11]. However, in hard tissue examination, CT and CBCT can provide clear imaging. Considering the high cost of CT, the length of imaging time, and the amount of radiation exposure to the patient, CBCT imaging systems have been found to be more advantageous [1,8,15]. For these reasons, CBCT is a routinely used imaging method and CBCT images were used in the evaluation of cortications.
Many studies examining cortication in the hard tissue components of the TMJ have indicated that cortication may be an effective parameter in determining bone age. The classification of AEC and MCC was based on these studies [3,4,16–21]. In a study of 40 patients, MCC showed a positive correlation with age [16]. Sphenooccipital synchondrosis and MCC were also examined in 253 patients and the relationship between age and MCC was emphasized [17]. The articular eminence of the TMJ and the mandibular condyle develop simultaneously. The articular eminence acquires its final form at around 20 years of age, while the homogeneous, continuous compact bone around the mandibular condyle is formed at about age 21–22 years; therefore, the present study had a lower age limit of 22 years [3]. In the study conducted by Ingervall et al [18] with microradiograms, the fact that the trabecular bone in the TMJ is replaced by the cortical bone and reaches its almost adult appearance at the age of 20 years supports the accuracy in our minimal age selection. Bayrak et al [19] examined the relationship between age and MCC, and found a positive correlation between chronologic age and MCC and that type 1 and type 3 cortications were observed at the age of 31 years at the most in all cases in the study. Therefore, the maximum age was accepted as 31 years in the present study.
Parafunctional habits such as bruxism, stress, and lateral pterygoid muscle hyperactivity can cause reduced disc displacement [22]. Overloads on the mandibular articular surface can lead to cortical bone loss in related structures [20]. Yalçin and Bozan assessed the relationship between AEC, MCC, and mandibular cortical index, concluding that examining the cortication of bone structures may be useful in assessment of TMJ diseases [4]. Renders et al [23], using microCT, found that the anterior cortex of the mandibular condyle had a lower degree of bone mineralization and more heterogeneity than the subchondral and posterior cortex. They also reported that bone loaded with high and frequent forces is more prone to remodeling and will show less mineralization. Condyle morphology can differ between the contralateral condyles of the same person. It is thought that the development of the cortex in the condyle will affect the morphology of the condyle, just like malocclusions [21]. Loss of AEC and MCC on the side with ARDD was significantly different from on the intact side. Abnormal forces to the TMJ are likely to cause ARDD and loss of cortication. In this case, it is possible that the loss of cortication in AEK and MCC can be used not only for the detection of degenerative joint disease and age but also for the diagnosis of ARDD. Cortication loss also occurs in patients without ARDD. This supports that different stress magnitude, direction, and frequency cause cortication loss. In addition, cortication loss in the mandibular condylar process was always found to be equal to or greater than in the articular eminence. Our results suggest that cortical loss can be observed before ARDD occurs because of abnormal forces on the condyle. In our opinion, this loss occurs first in the condyle and then in the articular eminence.
The most important limitation of this study is the lack of detailed clinical examination of patient dues to the retrospective nature of the study. Only patients with anterior disc displacement (including anteromedial and anterolateral) were included in our study. Medial, lateral, posterior, and combinations of these displacements were not included because there were not enough patients. Prospective studies are needed on this topic. Different populations, different sample groups, and different disease groups can be used to investigate the relationship between ARDD and MCC.
Another limitation of the study is that the etiologic factors in the process of ARDD formation and loss of cortication could not be fully investigated. Cohort studies will contribute to the understanding of this process and its etiologic factors.
Conclusions
We found a positive correlation between ARDD and AEC and MCC type, and that decreased AEC and MCC may be a criterion for the preliminary diagnosis of ARDD. In agreement with previous studies, MRI was found to be advantageous in the visualization of soft tissue components of the TMJ and CBCT in the examination of bone components.
Figures
Figure 1. Cone beam computed tomography images are shown in the sagittal axis (A–C). White arrowheads indicate cortication of the mandibular condyle. Classification of mandibular condyle cortication (MCC) describes the density and quality of cortical bone around the mandibular bone. (A) Type 1: There is no homogeneous and continuous compact bone in the periphery of the mandibular condyle. (B) Type 2: There is partially homogeneous and discontinuous compact bone in the periphery of the mandibular condyle. (C) Type 3: There is homogeneous and continuous compact bone in the periphery of the mandibular condyle. Figure 2. Cone beam computed tomography images are shown in the sagittal axis (A, B). White arrowheads indicate articular eminence cortication. Classification of articular eminence cortication (AEC) describes the density and quality of cortical bone around the mandibular bone: (A) Type 2: There is partially homogeneous and discontinuous compact bone on the surface of the articular eminence. (B) Type 3: There is homogeneous and continuous compact bone on the articular eminence surface.References
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