The part where the articulation of the temporal bone of the cranium and the mandible occurs is called the temporomandibular joint (TMJ)
Development of TMJ – Milestones
- 7th–8th weeks IUL – primary cancellous bone is first seen in the temporal mesenchyme and by 8th week it is seen in ramal mesenchyme
- 9th-week IUL – The rudimentary mandible is formed by intramembranous ossification
- 10th-week IUL – The condylar cartilage is first seen First sign of lower TMJ space is seen when a cleft is formed between the condylar process and the temporal component
- 12th week – The disk is connected to the upper part of the lateral pterygoid
- 14th week – Lower and upper TMJ spaces are fully formed
TMJ – structure
- Is formed by the mandibular condyle fitting into the mandibular fossa of the temporal bone
- Articular disc separates these two bones from direct articulation
- TMJ is made up of only two bones. Functionally, the articular disc serves as a non-ossified bone that permits the complex movements of the joint
- Hence, the craniomandibular articulation is considered a compound joint
Functions of synovial fluid which is present in the joint space –
- Providing metabolic requirements to these tissues
- Serves as a lubricant between articular surfaces during function
- The synovial fluid helps to minimize the friction
- Boundary lubrication – Occurs when the joint is moved and the synovial fluid is forced from one area of the cavity into another. It prevents friction in the moving joint and is the primary mechanism of joint lubrication
- Weeping lubrication – Articular surfaces to absorb a small amount of synovial fluid and under compressive forces, a small amount of synovial fluid is released. Metabolic exchange occurs here
Innervation of TMJ
- Branches of the mandibular nerve
- Auriculotemporal nerve
- Deep temporal and masseteric nerves
Vascularization of the Temporomandibular Joint
- Superficial temporal artery
- Middle meningeal artery
- Internal maxillary artery
- Deep auricular, anterior tympanic, and ascending pharyngeal arteries
- Inferior alveolar artery
Ligaments of TMJ
- Three functional ligaments support the TMJ – the collateral ligaments, the capsular ligament, and the temporomandibular (TM) ligament
- Two accessory ligaments also exist – the sphenomandibular and the stylomandibular
Common Symptoms of TMD include
- Decreased mandibular range of motion,
- Pain in the muscles of mastication,
- Temporomandibular joint (TMJ) pain,
- Associated joint noise with function,
- Generalized myofascial pain,
- Functional limitation or deviation of the jaw opening
Clinical relevance
- If a patient presents with early morning muscle tightness and pain, bruxism should be suspected
- The treatment of choice is likely to be an occlusal appliance that will alter CNS induced activity
- If patient reports that the pain began immediately following an alteration in the occlusion (i.e., placement of a crown) and is present much of the time, the occlusal condition should be suspected as a potential etiologic factor
- Alteration of the occlusal condition is generally not indicated since it is not an etiologic factor
- Proper assessment should be made to determine the most appropriate therapy. In this sense, patient’s history may be more important than the examination
Article by Dr. Siri P.B.
