**3. Classification of TMJ disorders**

The temporomandibular joint is mainly classified into three main groups: GROUP I—MUSCLE DISORDERS.

GROUP II—ARTHRALGIA, ARTHRITIS & ARTHROSIS.

GROUP III—DISC DISPLACEMENT.

Group I consist of myofascial pain and myofascial pain with limitation in aperture. Group II consists of arthralgia (joint pain), osteoarthritis and osteoarthrosis.

Group III consists of disc displacement with reduction, disc limitation without reduction, and disc displacement without reduction and with limitation of aperture.

TMD can be further subdivided into pain-related disorders such as myofascial pain and arthralgia and typically non-painful disorders.

TMDs are characterised by pain in the preauricular area, TMJ/muscles of mastication, limitation/deviation in the mandibular ROM and TMJ sounds (clicking, popping and crepitus) during mandibular function, headaches and jaw tenderness on function. Clicking is the most common symptom of TMJ dysfunction.

A number of studies have examined physical therapy for TMJ dysfunction and pain, including massage, electrotherapy, active exercise and manipulation therapy. Ultrasound therapy reduces pain and inflammation and improves mouth function [8].

#### **3.1 Causes**

The main causes Of TMJ disorder are unclear, but it is multifactorial.

Capsule inflammation and muscle pain are caused by occlusion, stress, anxiety or abnormalities of intra-articular disk. Parafunctional habits may cause TMJ microtrauma or masticatory muscle hyperactivity [9].

TMJ disorders may also arise after macro-trauma or facial trauma also due to malposition of TMJ disc termed 'internal derangement' and osteoarthritic changes.

Severely injured in the TMJ leads to disordered; for example, it can result in a severe blow on the jaw to break bones or damaged disk, which could destroy the smooth movement of the joint, causing pain or bad occlusion [10].

Some behavioural factors like continuous chewing gum may also lead to unrest in the TMJ joint.
