Introduction
A balance between the joint component, the muscle component, and the dental component is desired for the health of the masticatory system. Therefore, it is crucial to use radiography in conjunction with clinical evaluation to make the correct diagnosis of TMD. It will make it easier to develop a treatment plan that works. Imaging supports clinical findings, according to the 1992 revision of the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD).1
The word "ginglymo-diarthrodial," which combines the terms "ginglymoid (rotation) and arthrodial," is used to describe TMJ (translation). Disorders of the temporomandibular joint can have a variety of etiological causes. Factors include muscle hyperactivity, degenerative, and inflammatory illnesses affect the stability of the TMJ. These ultimately have a significant impact on the emergence of diseases of the temporomandibular joint (TMD).2
TMDs can manifest in a variety of ways, such as with pain and soreness in and around the TMJ, such as in the pre-auricular region, with decreased mouth opening, or with a clicking sound during functional jaw movement.3 Tinnitus, depression, hearing loss or impairment, ear plugging, earaches, trouble swallowing, and vertigo are a few more uncommon problems.4
Previous research has linked TMDs to abnormalities in the TMJ's soft and/or bony tissues.5 Several methods, including panoramic radiography, transcranial radiography, magnetic resonance imaging (MRI), and, more recently, cone-beam computed tomography, can be used to assess the architecture of the TMJ (CBCT).6
The limitations of standard radiography techniques are seen in cases where there are bony abnormalities within the TMJ. The radiographic evaluation is crucial to the diagnostic evaluation of a patient with TMD. The American Academy of Oral and Maxillofacial Radiology (AAOMR) has outlined the criteria for choosing an image for diagnosis, determining a course of therapy, and establishing a protocol for relevant follow-up for TMD patients.7
Due to anatomical structural overlap, osseous abnormalities such as osteophytes, erosions, and pneumatization of articular eminence are difficult to see on standard radiographs. This recommends and necessitates the employment of cutting-edge imaging modalities including arthrography, MRI, computed tomography (CT), and most recently, cone beam computed tomography (CBCT).8
The introduction of CBCT is a relatively new development in a field of clinically oriented CT technologies that is constantly increasing. At Mayo Clinic, the first CBCT scanner prototype was put to service in 1982. According to the current report, a number of CBCT systems have developed and are currently widely utilised for medical imaging.9 For the evaluation of osseous abnormalities in the TMJ, CBCT is regarded as a trustworthy diagnostic imaging method.10 Digital CBCT is as accurate as computed tomography (CT), but it exposes patients to less radiation, making it the preferred method over traditional CT.11 The doctor can check for osseous abnormalities in the TMJ using CBCT imaging, including osteophytes, erosion, flattening, subchondral bone sclerosis, ankylosis, and pseudocysts.12
Previous studies did find some structural damage in TMJ in some patients without TMDs. Therefore, there is a need to understand the importance of radiographic imaging and its correlation to TMD-related complaints. 13
Literature Review
Via 1988 to 2014, 256 publications were retrieved from a thorough data search in the PubMed and Google Scholar databases using the following search terms: temporomandibular joint dysfunction, cone beam computed tomography, temporomandibular joint imaging, radiography, and dental imaging. According to the parameters of the present review, a total of 32 papers were chosen and examined.
For the effective use of diverse imaging techniques such panoramic radiography, plain radiography, conventional and computed tomography, arthrography, and MRI, Fryback and Thornbury14 presented a six-level hierarchical model in 1991. All these imaging techniques are being practised with varying frequency in clinical practice to image TMJ. Unfortunately, all these imaging techniques have some kind of shortcomings in effectively visualizing the TMJ anatomy. Hence it is crucial and important to understand the accuracy and reliability of each imaging modality as it affects and determines the choice of treatment and prognosis of TMD patients.
Panoramic radiography is one of the most well-liked and often utilized imaging modalities for the facial region. Getting panoramic imaging of the TMJ is rather easy. Its low-grade sensitivity for osseous changes of the mandibular condyle is a disadvantage that significantly reduces its diagnostic accuracy and dependability. All that can be seen on conventional radiographs of the TMJ are its mineralized structures. These are impacted by a number of neighboring structures that are superimposed, which makes visibility challenging. They were disqualified from consideration in the RDC/TMD validation technique due to their restricted TMJ imaging range.14
According to the RDC/TMD validation protocol, Ahmed and Hollender in 200915 suggested the use of CT since it is more effective than other imaging modalities at identifying osseous abnormalities within the TMJ.
According to a comprehensive review by Hussain et al. from 2008,16 axially corrected tomography is the preferred imaging method for identifying erosions and osteophytes in the TMJ.
The usage of medical grade CT is largely restricted to hospital settings owing to its high equipment setup infrastructure cost and radiation dosage. Regarding TMJ Imaging, enormous amount of literature is available and being published in recent times as CBCT has inspired and fueled this research related to TMJ imaging.
Tecco and Saccucci et al in 201017 studied condylar volume and surface in caucasian young adult subjects and reported that the CBCT imaging of TMJ allows accurate measurements of both surface and volume of condylar element. These findings help in treating patients with TMJ disorders.
Osteoarthritis is viewed as a degenerative condition that worsens with age. Nearly 40% of patients over the age of 40 experience it. It is characterised by osseous changes in the TMJ, including flattening, osteophytes, sclerosis, erosion of the mandibular fossa, erosion, resorption of the condylar head, and loss of joint space.
The two most common degenerative alterations in the TMJ as seen on CBCT were flattening (59%) and osteophyte (29%), according to Pontual and Freire et al. in 2012.18
Numerous in-vitro studies have been conducted to examine the role of CBCT in identifying osseous anomalies and osteophytes in cadaveric TMJ. According to Librizzi and Tadinada et al., using a 6-inch FOV in CBCT rather than a 12-inch FOV is more useful for diagnosing the erosive changes in the TMJ in 2011.19
Using CBCT imaging, Alexiou et al. revealed in 200920 that the degenerative alterations in the TMJ get worse with age.
In 2010, Alkhader et al.21 performed a comparison of CBCT and MRI. According to their findings, CBCT is preferable to MRI for detecting abnormalities such osteophytes, flattening, or erosion as opposed to size changes. In clinical applications, MRI has a reduced spatial resolution and a greater slice thickness (>3mm). The accuracy of MRIs is impacted by the presence of fibrous structures in the TMJ, near proximity of the lateral pterygoid muscle to the articulating condyle, and air spaces within the temporal bone.
According to Palconet and Ludlow in 2012,22 there is little association between CBCT-based radiographic imaging and clinical signs and symptoms in individuals with TMJ osteoarthritis.
Early juvenile idiopathic arthritis (JIA) diagnosis in children is aided by CBCT imaging. If circumstances go unnoticed, this may influence facial development and cause growth deviations.
In order to volumetrically measure the TMJ damage in TMDs, Farronato and Garagiola et al.23 investigated the use of CBCT for quantifying the condylar and mandibular volumes.
Children with juvenile idiopathic arthritis were investigated by Huntjens and Wouters in 2008,24 specifically condylar asymmetries (JIA). They claimed that CBCT revealed a variety of condylar damage patterns, from minor cortical erosions to full condylar head deformity.
Palomo et al. in 200925 described a multiple maxillofacial fracture scenario, similar to Le forte III, and noted that, in most situations, neither conventional dental radiography nor medical CT alone can resolve all diagnostic difficulties. The use of CBCT in this situation helps to reveal pertinent details on the type of fracture, its extension, and the location of significant anatomic landmarks.
Children with TMJ dysfunction were the subject of a study by Sanchez Woodworth et al. in 198826 using arthrography, computed tomography (CT), and magnetic resonance imaging (MR) of one or both joints. They discovered that 85% of patients exhibited TMJ changes. Wiberg and Wänman in 199827 used TMJ tomography in young patients with signs and symptoms of temporomandibular disorders and found a high prevalence of 66% with temporomandibular joint alteration.
Price et al. in 201228 reported the incidental findings of TMDs to be 15.4% using in CBCT imaging.
TMJ changes made for 12.6% of all incidental findings in this group of 427 orthodontic patients, according to Edwards et al 201429 research on CBCT pictures of these individuals.
The prevalence rate of TMJ changes in CBCT pictures of dental implant patients ranged from 3.9% to 6.2%, according to Pette and Norkin et al 201230 analysis of incidental findings from a retrospective study of 318 cone beam computed tomography consultation reports.31
The articular fossa and condyle characteristics of people with TMD problems were examined by Okur et al. using CT of the temporomandibular joint. They found no obvious difference between the joint spaces of the two groups (asymptomatic group). Osteophytes were seen 14% of the time in CBCT pictures of TMD patients, according to Alkhader et al. in 2010.21
In their study, Palconet and Ludlow in 201222 found little connection between the structural alterations seen on CBCT images and the clinical symptoms and indicators of TMJ problems. Lee et al in 201232 in their study on 212 TM joints found that CBCT was able to detect more percentage of erosion compared with OPG. CBCT was able to detect 2.1% of osteophytes whereas OPG detected only 0.9% and hence proving that CBCT is superior to OPG.
Another study done by LeResche (1997)33 found that pain in the temporomandibular joint is twice as common in females as in males.
Future Considerations
Imaging is regarded as a crucial diagnostic aide to the clinical evaluation.34 No innovation or piece of technology is exempt from criticism, and CBCT is no different. On a few occasions, it has drawn criticism. The use of CBCT in the investigation of sinus, middle and inner ear implant, and dento-maxillofacial imaging is among the most extensively studied topics in head and neck imaging.9 The amount of study into TMJ imaging has increased dramatically. Even however, exploratory research has not yet been able to prove CBCT's superiority to other TMJ imaging modalities and support its therapeutic use through thorough clinical and prospective reviews.
Limitations of CBCT
The metal artefacts are lessened in more recent CBCT scanners with integrated FPD. However, the movement artefacts are still present and are a cause for concern. The distortion of the Hounsfield Units (HU) is another area of concern, hence CBCT cannot be used to estimate bone density. CBCT has a benefit because to the minimal radiation exposure to the patient. However, no such consensus regarding the radiation detector setup in phantoms for the CBCT dosimetry measurement has been developed as of yet. The majority of CBCT studies that have been published do not give enough details about the radiation dose, image quality, or CBCT equipment parameters. The ability of CBCT to see inside soft tissue is limited.2 Hence the role of CBCT in TMJ disc derangements is under question. Currently, CBCT has been largely adopted as a dental office-based diagnostic imaging technique. CBCT imaging in TMD’s assist in diagnosis and treatment planning but enthusiastic overuse of CBCT and patient safety must be taken into consideration.
Conclusion
Finding information about TMJ imaging reveals that the anatomy and physiology of the TMJ can be evaluated using a variety of radiographic techniques. Due to the superimposition of nearby structures and morphological differences, it is a region that is typically regarded as being challenging for imaging. To effectively manage the patient, however, the complexity of the TMD necessitates detailed and exact imaging of the area. Due to its low radiation dose to the patient, minimal setup equipment requirements, and special capacity to produce multiplanar reformation and 3D images, CBCT clearly has an edge over other imaging procedures. The use of CBCT in TMJ imaging has been the subject of promising studies. However, more systematic clinical studies, adequate training of the personnel and a complete understanding of the anatomical and functional dynamics of the TMJ are essential to harness the very true potential of this breakthrough technology.
According to prior research, patients with TMDs have a significant prevalence of bone abnormalities that can be seen on CBCT imaging. On CBCT pictures, it can be shown that the prevalence of different TMJ derangements was similar in both symptomatic patients with TMJ disease and those who had no symptoms. It demonstrates that a small number of people who have TMJ structural impairment may not exhibit it clinically. As a result, it is recommended as a conclusion that routine CBCT imaging be used in dentistry together with careful attention to clinical examination to detect this problem (TMD build-up) in its early stages.
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