By Claudia Blandford, M.E.Sc., EIT

The temporomandibular joint dysfunction (TMD) describes the impaired movement and function of the jaw, due to injury in the bone or soft tissue of the surrounding structure. TMD symptoms can include pain, clicking noises and restricted movement. Although some TMD patients present with objective physical signs such as clicking or medical imaging showing a displaced disk, other diagnoses are based more on subjective pain and movement symptoms. As such, legitimacy questions can arise in injury claims, specifically whether the TMD has occurred as a result of a particular incident or motor vehicle collision, or whether the claimant is experiencing symptoms due to a pre-existing condition or coincidental injury.

Trauma has been identified as an initiating factor of TMD; however, some research suggests that trauma more likely acts as a catalyst for the dysfunction in those with physiological, psychological and behavioural predispositions or perpetuating factors. Some of these factors include maxillofacial occlusion (over or underbites), or teeth grinding and jaw clenching habits. Women are also more susceptible to TMD, as are those who experience stress, anxiety or depression.

Although most researchers agree that a direct impact to the jaw can induce TMD, the literature is undecided on the effect of indirect loadings, such as whiplash mechanisms, to temporomandibular joint health. There have been some studies showing a statistically moderate to high prevalence of TMD among patients with whiplash-associated disorders (WAD), but other research denies this prevalence. Complicating TMD diagnoses is the fact that some WAD symptoms can present as TMD because referred pain from the neck can be experienced in the face and jaw. Biomechanically, this injury mechanism has been refuted based on an analysis comparing jaw joint loads under mastication (chewing) and joint loads under neck flexion-extension. It found that the kinetics of a whiplash event resulting in accelerations exceeding regular jaw loading would cause objective signs of serious cervical spine injury such as fracture, hemorrhage, or paralysis. More recently, low speed computational and live human experimental studies have been introduced to the body of literature, confirming that it is unlikely that people subjected to rear collisions of less than 10 km/h change in velocity (delta-V) will sustain indirect trauma to the temporomandibular joint.

CEP Forensic can investigate TMD injury by assessing a collision incident for severity, and by determining whether jaw contact occurred. If the severity of the collision was less than 10 km/h delta-V and there was no impact to the jaw, it is unlikely that TMD resulted from the collision. As always CEP Forensic can also determine the likelihood of WAD and this combined biomechanical analysis can provide valuable insight into vehicle collision injury claims.

If you have any questions or would like to learn more about this topic, please contact our Biomechanical Engineering team at 877 686-0240 or info@cep-experts.ca

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