Additional Effects of Therapeutic Exercises Under a Behavioral Umbrella for Chronic Temporomandibular Disorders Treatment

TMD is an alteration of the jaw function associated with disorders at the mastication muscles, mandibular joint and its associated tissues. It constitutes a major health problem since it's one of the main causes of oro-facial chronic pain and interferes with daily life. It is associated with headache, otological symptoms, cervical dysfunction and alterations in posture at the cervical level. The TMD involves genetic, anatomical, hormonal factors, traumatisms, motor behaviour, psycho-social aspects and occlusal problems.

The psychological aspects of patients with TMD have a huge importance, affecting their ability to manage pain and interfering with the resolution of the picture. It can even cause the pain to become chronic. The most prevalent symptoms in TMD are somatization and depression. Chronic pain can lead to plastic changes in the brain that lead to hyper-excitability of the central nervous system. Persistent pain produces protective memories that involve antalgic behaviour, avoidance and kinesiophobia. The literature shows that somatization, depression, fear of pain, fear of movement and catastrophism in conjunction with the amplification of pain are key factors in the chronification of TMD.

The TMD treatment must provide the ideal circumstances for the repair and adaptation. The TMD is usually a benign self-limiting process, so the guidelines always recommend non-invasive, reversible treatments in the first instance and within the bio-psycho-social approach.

For conservative management, the most evidence-based approach is manual therapy (MT). The one that has demonstrated more effectiveness is the mobilisation with impulse and / or mobilisation both at cervical and mandibular level. MT improves motor response, range of motion and modulates pain intensity via peripheral, medullary and supraspinal mechanisms. Theories suggest that hypoalgesia is caused by several mechanisms mediated by the periaqueductal gray substance.

Different studies analyse MT and motor control exercises (MC) as a whole or separately, comparing them with other therapies such as education, splints, medication, botulinum toxin, arthroplasty and arthroscopy. In these cases, MT with MC are superior to these therapies. Despite this, MC exercises do not suggest adding significant improvement in the treatment of TMD, at least in the short term. Shafer et al., In a recent systematic review, state that there is currently no evidence for the use of MC exercises of any kind for the management of TMD in general. However, according to a recent research line MC with education is the clue for the management of chronic pain. The objective of the exercises is to perform a cognitive approach to provide the desensitization of the central nervous system, generate new memories and eliminate the protective movement associated with chronic pain. It also promotes eliminating catastrophism, avoidance and fear of pain behaviour associated with chronification. This leads us to think that it should be studied more carefully if CM performed with a cognitive approach adds beneficial effect to MT in the treatment of chronic TMD not only in purely mechanical aspects but also in psycho social aspects of the individual and longer term.

The current studies are of low quality, have biases in the selection, randomisation and allocation concealment. Patient selection and diagnostic criteria are not standardised. There is a lack of blind of the evaluator and examiner. The therapy or exercise is not well described making them difficult to reproduce. The new lines of research require more detail about the type of exercise to be performed and the MT applied as recommended by the intervention report guides.

HYPOTHESIS The combination of MT and Myofunctional MC (MMC) is more effective than MT applied in a unique way for the treatment of pain, function and psycho social symptoms associated with chronic TMD.

Inclusion criteria

• Primary diagnosis of TMD type: I myofascial and or II displacement of disc and or III other arthralgias. According to the diagnostic criteria of Dworkin S. Et al. The clinical examination and algorithms that will be carried are the ones included in the the axis I of the Diagnostic criteria for TMD (DC/TMD). We will use the Spanish version.
• 6 months of TMD evolution and pain in the last 30 days.
• Signs of pain and disability of at least 7 points on the CF-PDI.
• Normal neurological examination.
• Normal orthopantomography (without fracture or severe joint bone disease).
• To accept the participation and sign the informed consent.

Exclusion criteria

• Severe dermatological or intrabuccal problems, head or neck injuries.
• Orthopantomography with recent fractures or severe articular bone pathology.
• Previous treatment (three months before) with manual therapy splints or acupuncture.
• Previous diagnosis of severe psychiatric disorder.
• Systemic, rheumatologic or neurodegenerative diseases.
• Previous diagnosis of primary headache or unilateral neck pain of recent appearance.
• Associated clinic of neurological pain, radiculopathy or myelopathy.
• Not understanding Castilian or Catalan.