Progress is Impossible without change, and those who cannot change their minds cannot change anything.
—George Bernard Shaw
Over the past few years it is becoming increasingly apparent that the dental surgeon can no longer overlook or ignore the patients presenting with temporomandibular joint dysfunction as temporomandibular joint (TMJ) function forms an integral part of oral physiology.
The TMJ evokes much emotion. It is the orphan articulation of dentistry and medicine. It is deeply respected by those who attempt to know it well and is reviled by those who choose not to pursue the knowledge of its vagaries. The magnificently complex and compact structure is virtually ignored by those who claim expertize for every other bone and joint. It is both, a microcosm and a galaxy.
The TMJ has many structural features that make it a unique joint. The TMJ is a synovial joint, which is also known as ginglymoarthrodial (diarthrosis) joint. Joint is not totally capsulated as it allow insertion of two head of lateral pterygoid muscle anteriorly, because of this peculiar architect of TMJ, it is more prone for disorder like hypermobility, subluxation and dislocation.
The diagnosis and treatment of TMJ disorders remains one of the most challenging areas of dentistry. Advances in both the diagnostic imaging and the understanding of the underlying mechanism of dysfunction of TMJ have been made possible by recent developments in imaging and treatment modality. With the newly expanded diagnostic imaging capabilities, the clinician must determine which technique offers the highest probability of significantly aiding diagnosis and treatment. Imaging procedures may be utilized in the examination of not only the osseous components but also of the soft tissue components of the joint.
The term temporomandibular joint disorder (TMD) embraces a number of clinical problems that involve the masticatory musculature, the TMJ (both osseous and soft tissue component) and its associated structures. The most common cause of TMJ dysfunction is thought to be due to internal derangement of the joint; about 80% of all the TMJ problems are related to the displacement of the articulator disc or internal derangement's.2
Symptomatic TMJ dysfunction affects 28% of the adult population, with a smaller but significant percentage experiencing severe impairment. The clinical problem is complex since TMJ dysfunction is multifactorial. Although most occurrences are related to internal derangement, many joints are painful secondary to nondiscogenic causes, such as, referred pain from spondylosis of the upper cervical spine and other inflammatory and neoplastic bone lesions in the vicinity of the TMJ.
The etiology of internal derangement is obscure, although in 25% of patients a history of trauma is elicited, of which 30% of causes are iatrogenic and result, from procedures that necessitate jaw extension, for example, tonsillectomy, endoscopies, and molar tooth extraction. Not uncommonly, misdiagnosis continues for several years, particularly during childhood and adolescence because of a variety of poorly understood presenting symptoms. As a result, severe degenerative changes in the TMJ are observed even in children. The main causes of internal derangements are trauma, abnormal functional loading and degenerative joint disease. Para function habits may be one of the initiating and perpetuating factors that affect primarily the masticatory muscles and secondarily the joint.
Internal derangements of the TMJ are described as disturbances in the normal anatomical relationship between the disc and the condyle or as disc displacement with or without reduction. Disc displacement may be in any direction, anterior, posterior, medial or lateral, anterior displacement being the most common. Such derangements change the normal function of the TMJ and usually are associated with symptoms like joint sounds, pain and limitation of the range of mandibular motion or deviation. As a result of internal derangement, degenerative changes in the articulating tissue and perforation of the disc or at the junction between the disc and retrodiscal tissue may occur.
Plain film and tomographic examinations are useful screening modalities for the TMJ. They are valuable for determining the presence of osseous changes and traumatic injury to the osseous components of the joint. Negative findings on plain film are most frequent but do not give confirmation that the joint is normal, as they do not provide information regarding the presence or absence of soft tissue disease. These techniques are successful in detecting the shape of the condyle, joint outline, and osseous changes including flattening, osteophytosis, sclerosis, and erosion. Comparisons of techniques indicate that tomography is superior to radiography, but it requires an experienced operator, requires more imaging time, and renders a higher radiation dose. However, for determining the position of the condyle in the glenoid fossa, tomography is the ideal technique.
Other useful information that can be obtained on radiography is the extent of condylar translation at the maximal mouth opening. Restriction of anterior condylar translation at the maximal mouth opening implies that3 the condyle does not translate all the way to the most inferior aspect of the articular eminence. This suggests that soft tissue is interposed between the joint components, which may indicate disk displacement without reduction but is not pathognomonic. Therefore, these methods are ineffective in evaluating internal derangement of the TMJ.
All imaging techniques are not equally effective for each of the many conditions that affect the TMJ. Efficacy of any imaging examination rests not just with its technical adequacy but also with its diagnostic accuracy, a complex interaction between the image and person interpreting it. TMJ imaging involves assessment of the integrity and relationships of the hard and soft tissues, including the mandibular condyle, glenoid fossa and articular eminence of the temporal bone, and the articular disk and its attachment.
With the rapid progress in TMJ imaging technique, disc displacement has increasingly been thought to be involved in the development of TMJ internal derangement. Conventional and routine imaging techniques have limitations when used for diagnosis of internal derangement as they cannot give any information regarding the disc position. Although TMJ arthrography can to some extent be helpful, but it being an invasive procedure is not very popular.
Magnetic resonance imaging (MRI) is currently considered the optimum modality for imaging the TMJ in patients with temporomandibular disorder particularly for the soft tissue. It can provide valuable information of the condition of TMJ particularly of the articular disc, joint effusion, posterior bilaminar zone and early condylar bone marrow changes.