Biting, chewing, gnawing: Is the TMJ special?

The Temporomandibular Joint (TMJ) is a combined hinge and plane jointthat connects your jaw to the temporal bones of the skull [1]. With theexception of the ear ossicles, the TMJ is the only freely movable jointbetween skull bones [2]. The TMJ is a unique structure, with one on eachside of the jaw, comprised of three major components including thearticular eminence, the articular disc and the condylar process of themandible. These components are surrounded by the articular capsule,which encircles the circumference of the joint. Attached to the articularcapsule are three ligaments, the lateral ligament, the sphenomandibularligament and the stylomandibular ligament which help strengthen the joint,prevent the displacement of the mandible and limit the movement of themandible at the TMJ. The TMJ allows movements such as retraction,protrusion, depression, elevation and rotation which enable mouth openingand closing and chewing [3], therefore compared to other joints in the body,the TMJ allows a different range of movements contributing to itsuniqueness. Its speciality is further emphasized by the fact that it works asa pair that is unlike any other. If you consider other parts of the body, forexample the joints in the finger, you are able to move one joint withoutdisturbing the other two. However, it is impossible to just move one TMJwithout moving the other. This paired function is the reason whyimbalances and irregularities on one side automatically translate tocompensatory mechanisms on the other side [4]. Although it is clear theTMJ has unique features, you may argue that it is just one of many otherjoints in the body. So, is it really that special?

Although the research above suggests a relationship between psychological factors and TMJ disorders,

further evidence has shown that TMJ disorders can be caused by a number of other factors that are not of a psychological origin. For example, various types of

arthritis, such as rheumatoid arthritis and osteoarthritis, jaw injury and long-term (chronic) grinding or clenching

of teeth [7]. Therefore, in this respect the TMJ is not special as the disorders are like those of other joints in

the body e.g arthritis of the spine.

Although the TMJ is one of many joints in the body and its disorder shares similar causes to that of other joint

disorders, there are many

Introduction

Discussion and Conclusions

Results

SCHOOL OF DENTISTRYLiverpool, L69 3GN, UK. Email: hlarichm@student.liv.ac.uk

[1]WebMD. Temporomandibular disorders (TMD) and joint pain; Jan 25 2017

[2] Tortora GJ, Derrickson BH. Principles of anatomy and physiology (Tortora, principles of anatomy and physiology).

14th ed. United Kingdom: Dec 23 2010. [3] TeachMeAnatomy. Temporomandibular joint; Feb 17 2013

[4] Haddad J. Anatomy. Michigan Center for TMJ & Sleep Wellness Logo. What makes the Temporomandibular joint

special; Dec 9 2015[5] National Institute of Dental and Craniofacial Research.

TMJ disorders; Dec 1 2016[6] Mottaghi A, Razavi MS, Pozveh EZ, Jahangirmoghaddam

M. Assessment of the relationship between stress and temporomandibular joint disorder in female students before

university entrance exam. Dec 1 2011[7] Clinic M. Mayoclinic. TMJ Disorders; Jun 21 2016[8] Sumdili. Dentistry and medicine. Anatomy of the

Temporomandibular Joint (TMJ); 2014

Methods

explanations to prove its speciality. Along with those mentioned earlier, the

TMJ is also special because in most joints, there’s a single fluid-filled cavity (the synovial cavity) that surrounds the entire joint, but in the TMJ the articular disk divides the joint in half, with two

separate synovial cavities, one on either side of the disk. This helps each TMJ

move as if it’s two joints [4].

It is clear that both the structure and the function of the TMJ is unique and hence

overall this joint is special.

References

Abbie Richmond

Google and google scholar were first used to identify any informationrelevant to the poster title. A variety of sources were provided,however not all proved to be relevant and useful for this particular title.Subsequently, a plan was written in order to gather all the relevantinformation and this was then formulated into categories. A mind mapwas then created to link all the ideas taken from the various researchfindings. All the ideas generated were then arranged in an order thatthey would appear in the text. The text for this poster was firstly writtenout in Microsoft Word and was then copied and pasted into MicrosoftPowerPoint.

TMJ disorders are a group of conditions that cause pain and dysfunction in the jaw joint and the muscles which

control jaw movement [5].

Research has been conducted to assess the relationship between psychological stress and anxiety and TMJ joint disorders in female students before a university entrance examination. A prospective study was carried out to assess this, in which participants were randomly selected. One hundred and thirty pre-university students

in Isfahan were evaluated with Ketel's test of anxiety, exam stress test and temporomandibular disorder questionnaires [6]. The participants were assessed twice, firstly eight months before the entrance exam and then one month before the entrance exam. Clinical assessments consisted of masticatory muscles and

sternocleidomastoid muscle palpation, temporomandibular joint palpation for pain and noise and its movement, and mouth opening limitations [6]. Data was then analysed using the Wilcoxon rank test and a paired t-test with the P value under 0.05 being considered significant. Results found that the level of anxiety and

occurrence of temporomandibular disorders increased between the two assessments and had the highest level in the second assessment [6]. It appears that as your level of anxiety increases, so does the occurrence of TMJ disorders in individuals and therefore it is reasonable to suggest a possible relationship between anxiety and

TMJ disorders.

This piece of research further supports the argument for the speciality of the TMJ. This is because it suggests the fact that psychological factors such as stress or anxiety can have a direct impact on the TMJ. Arguably, this is unlike any other joint in the body, with their disorders being mainly physiological rather than

psychological. Therefore, the TMJ appears to be a very unique structure in the body.

Figure 1,taken from[8].

Labelleddiagram ofthe TMJ.

Comparison of the meanresults of the Ketel test andthe exam anxiety test inOctober and May (Pvalue<0.05)

Figure 2 taken from [6]