Oral Radiology-2 PDF University of Jordan Dentistry 019

University of Jordan Dentistry 019 Oral Radiology-2 WE ARE JUST FEW STEPS AWAY! Written by: Sara Abdullah Corrected by: Doctor: Mustafa Al khader Sheet# 10 ▪ Tempomandibular Joint (TMJ): 1) Normal anatomy of TMJ: The temporomandibular joint (TMJ) com...

University of Jordan Dentistry 019 Oral Radiology-2 WE ARE JUST FEW STEPS AWAY! Written by: Sara Abdullah Corrected by: Doctor: Mustafa Al khader Sheet# 10 ▪ Tempomandibular Joint (TMJ): 1) Normal anatomy of TMJ: The temporomandibular joint (TMJ) composed of both osseous (bony) and soft tissue components. Therefore, pathologies affecting the soft tissues can consequently influence the function and integrity of the TMJ, and those involving the osseous structures can also impact the joint's integrity. A) Bony component: Condylar head, condylar neck, articular eminence, glenoid fossa and external auditory canal. B) Soft tissue component: Lateral pterygoid muscle, interarticular disk and retro-discal tissue. ▪ The interarticular disk is composed of anterior band, posterior band and a thin intermediate (middle) part. In the normal closed mouth position of the mandible, the posterior band is positioned on the top of the condyle. Moreover, the middle zone is the articulating part, which articulates between the condylar head and the glenoid fossa in the normal closed position of the mandible. ▪ The most common site of perforation is the retro-discal tissue. Arthrography is the best method to visualize perforation. ▪ CBCT (Cone Beam Computed Tomography) is the preferred imaging modality for the visualization of bony structures. ▪ MRI (Magnetic Resonance Imaging) is the only imaging modality for examining the articular disk, as one of the soft tissue components of TMJ. Using MRI we can observe: A) Photo A (sagittal view) demonstrates the posterior band of the articular disk on top of the condylar head. B) Photo B is a coronal view that is needed for the investigation for any medial or lateral displacement of the disk. Page | 2 2) Normal radiographic imaging of the mandible in a closed position: ▪ In a normal closed position of the mandible, the condylar head typically resides at the center of the glenoid fossa, although there are normal variations that must be considered. ▪ Four distinct abnormal placements of the condyle can be observed, each suggesting a specific condition: 1) Posteriorly positioned condyle indicates an anterior disc displacement. 2) Anteriorly positioned condyle indicates rheumatoid arthritis. 3) Inferiorly positioned condyle indicates fluid or blood accumulation. 4) Superiorly positioned condyle indicates the presence of perforation. ▪ If the condyle is positioned anterior to the articular eminence and out of articulation with the glenoid fossa (the eminence observed posterior to both the condyle and the disc) and the patient reported an inability of closing his mouth after an extended period of it being open, this scenario suggests a condition of condylar dislocation or open locking (photo on the right). 3) Normal radiographic imaging of the mandible during opening: ▪ During mouth opening, the condylar head starts moving downward and forward up to the apex of the articular eminence at maximum opening. ▪ More than 8 mm anterior to the articular eminence is considered abnormal and is characterized as hypermobility. Additionally, hypermobility can also occur posteriorly. 3) Diseases and anomalies affecting TMJ: A) Condylar Hyperplasia: This condition leads to an enlargement of both the condylar head and the ipsilateral mandibular ramus, and is characterized by: 1) Shift in the midline toward the contralateral side (unaffected side). Page | 3 2) Posterior open bite on the ipsilateral side (affected side). 3) Limitation in mouth opening. ▪ The photo on the right represents an OPG for a patient with condylar hyperplasia on the right side. ▪ As a differential diagnosis, we need to consider condylar tumors. However, with condylar hyperplasia, there are typically no alterations in the trabeculation or cortication of the bone, which are commonly observed in cases of tumors. B) Coronoid Hyperplasia: This involves an enlargement of the coronoid process, leading to its impingement against the medial surface of the zygomatic arch, which in turn causes limited mouth opening. Coronoid hyperplasia is identified when the enlargement extends 1 cm above the inferior border of the zygomatic arch. C) Arthritis: ▪ There are multiple arthritic conditions that may affect the condylar area, such as rheumatoid arthritis. ▪ Rheumatoid arthritis is a systemic, inflammatory disease that affects both sides of the body (bilateral) and leads to joint destruction, significant osseous alterations, and damage to the synovial membrane. The ongoing destructive process may lead to a diminished size of the condyle. As demonstrated in the radiograph on the left which shows a reduced condylar size in comparison to the normal size shown in the right radiograph. ▪ TMJ is affected in 50% of cases of rheumatoid arthritis. And it’s considered the most common cause of bilateral ankylosis. D) Juvenile Arthrosis: ▪ A condition characterized by bone destruction in the absence of any preceding inflammatory process. This destruction can present as the absence of the condylar Page | 4 neck, a flattened condylar head, and dorsal inclination, collectively giving rise to what is known as a toadstool-like appearance (as presented in the radiograph C ▲). E) Bifid Condyle: ▪ A condition in which there is a true condylar duplication that may be accompanied with vertical depression which may be mistaken with vertical fracture. However, the presence of a continuous cortication in a bifid condyle suggests that it is a case of bifid condyle, as opposed to a fracture, where there is cortical interruption. ▪ Bifid condyle sometimes may be caused by an actual trauma leading to a fracture but with time and body adaptation the condition is presented as a bifid condyle charectarized by a heart-shaped appearance. F) Internal derangement/disc displacement: ▪ Normally, whether the mouth is in a closed position or during mouth opening, there is a consistent articulation with the intermediate zone in between the condylar head and the articular eminence. Therefore, during opening both the condyle and the disc must move to the eminence simultaneously. ▪ In the case of anterior displacement, particularly when the mouth is closed, the posterior band of the disc is anterior to the condylar head instead of being on the top of it, and the intermediate zone is not articulating with the condyle. ▪ The anterior displacement can be categorized into two types: with reduction or without reduction, which is determined based on the relationship of the condyle and the disk during mouth opening. ▪ In the case of anterior displacement with reduction (ADWR), during mouth opening, the condyle moves to the eminence beneath the disc (in the intermediate zone), thereby reestablishing the normal positional relationship with the disc. Clinically the patient will present with a clicking sound in the TMJ. Page | 5 ▪ In contrast, in the case of anterior displacement without reduction (ADWOR) the disc remains anterior to the condyle and does not reposition itself during mouth opening, which result in a persistent abnormal relationship between the condyle and the disc. In long-term cases of ADWOR the patient may present with crepitus sounds and disc perforation. ▪ In MRI (A) the white arrow is pointing on the anteriorly displaced disc in the closed mouth position. During mouth opeinig (MRI (B)), the condyle moves beneath the disc and regain the normal position at the eminence. So this case represent ADWR. ▪ MRI (C), represents a coronal view of the condyle showing lateral displacement of the disc. The black arrowhead is pointing at the capsule. ▪ MRI (A, B, C, D) represent an anteriorly displaced disc without reduction. In MRI (C, during opening) the disc is anterior to the condyle and no normal relationship is established. ▪ (B) and (D) are T2-wieghted MRI which is used to visualize joint effusion (fluid accumulation in the joint) which is usually associated with pain. However, joint effusion can also be found as a normal finding without any underlying pathology. G) Degenerative joint disease( DJD) (osteoarthritis/osteoarthrosis): ▪ A condition in which there is bone destruction manifested as: 1) Flattening of the articular eminence, glenoid fossa and the condylar head. 2) Flattening of joint surfaces can lead to bony prominences called osteophytes. Over time these Page | 6 osteophytes can breakdown and separate from the original bone structure, the detached fragments are called joint mice. 3) Sometimes we can see bone marrow sclerosis. 4) Pseudocysts (photos A and B) can also be seen, with various degrees of destruction and erosions (photos C and D). ▪ However, bone flattening accompanied by bone marrow sclerosis, in the absence of any signs or symptoms, can often be interpreted as bone remodeling and changes associated with aging. H) Ankylosis: ▪ True ankylosis is characterized by the direct involvement of the joint itself, it could be osseous or fibrous. ▪ False ankylosis, conversely, occurs due to factors outside the joint, such as muscle spasm. ▪ The most common causes of unilateral ankylosis are trauma or inflammation ▪ In this radiograph, the loss of the joint space is not present. However, the irregularities on the two articulating surfaces (the condyle and the temporal bone) indicate fibrous ankylosis. I) Osteomyelitis in TMJ: ▪ As previously discussed, osteomyelitis manifests as moth- eaten appearance of bone and onion skin periosteal reaction. ▪ Osteomyelitis can potentially spread to the TMJ. Page | 7 J) Synovial osteochondromatosis: ▪ A metaplastic condition, in which the capsule will be fragmented resulting in cartilaginous bodies in the joint space. Over time these cartilaginous bodies will be calcified, resulting in calcified bodies inside the joint space. These calcifications that are uniformly distributed and surrounded with cortication are termed as synovial osteochondromatosis. K) chondrocalcinosis (pseudogout): ▪ This condition is characterized by the deposition of calcium pyrophosphates dihydrate crystals in the joint space. ▪ Radiographically, there are randomly distributed pinpoint calcifications. L) Fracture: ▪The condylar neck is often suspected to be the site of fracture in cases of trauma to TMJ, as it is considered the weakest point in the region. ▪ When a fracture occurs at the condylar neck and the fragmented piece shifts downward, forward, or medially from its original position due to the pull of the lateral pterygoid muscle, this displacement can lead to an increase in radiopacity (photo on the right). ▪ If the fractured bony fragment remains in its original position, without any displacement, then the fracture will be demostrated in radiographic images as a radiolucent line (fracture line). ▪ When a unilateral fracture of TMJ is identified, it is essential to conduct further investigations for a potential parasymphyseal fracture on the contralateral side. On the other hand, bilateral fracture necessitates the investigation for symphyseal fractures. Page | 8 M) Benign tumors: ▪ Most commonly osteoma and osteochondroma, which manifest as bony growths associated with changes in the trabeculation and cortication of bone. N) Malignancy and metastasis: ▪ Osteosarcoma, characterized by the sunray appearance (periosteal reaction). ▪ Chondrosarcoma, characterized by the destructive nature associated with bone formation. ▪ Another example of malignancies in TMJ is multiple myeloma. O) Deep antegonial notch: ▪ The presence of a deep antegonial notch can be an indication of destruction in the condylar head. This occurs as a compensatory mechanism in response to condylar head destruction. The patient's masticatory muscles become hyperactive in an attempt to compensate for the impaired function of the TMJ. This increased muscular activity leads to remodeling of the bone at the site of muscle attachment, resulting in the deepening of the antegonial notch. ِّ ‫َوقُ ْل َر‬ ‫ب ِّز ْدنِّي ِّعلْ ًما‬ Page | 9