7 topics with concise reviews: definitions, key facts, and class questions.
The temporomandibular joint (TMJ) is one of the most complex and functionally loaded articulations in the body. This chapter is dedicated to joint pathologies that maxillofacial surgeons regularly encounter in clinical practice, and requires a clear understanding of the topographic anatomy of the maxillofacial region.
The section systematically guides the reader from the basics (TMJ anatomy and biomechanics, methods of clinical and instrumental examination) to specific nosologies. The etiology, pathogenesis, and treatment principles of inflammatory (arthritis), degenerative-dystrophic (arthrosis), fibrous and bony fusions (ankylosis), as well as pain dysfunction syndrome, are analyzed in detail here.
In practical classes and examinations, instructors traditionally emphasize differential diagnosis of arthritis and arthrosis, and also ask to reproduce step-by-step the examination algorithm for a patient with a "clicking" jaw or restricted mouth opening. Understanding normal joint biomechanics is your main key to successfully passing this section.
What type of cartilage covers the articular surfaces of the TMJ?
Unlike most human joints, the surfaces of the TMJ are covered not with hyaline cartilage, but with a thinner and more fragile fibrous connective tissue cartilage.
What parameters of mandibular movements are considered normal?
Normally, vertical mouth opening (between the incisors) is 40–55 mm, and lateral excursions are symmetrical and equal to approximately 7 mm in each direction.
In which direction does the jaw shift during mouth opening in patients with chronic traumatic arthritis?
When opening the mouth, the mandible deviates (shifts) toward the affected joint.
Habitual dislocation always occurs after a previous acute dislocation, and targeted reduction (by the patient or a doctor) is always required to return the jaw to its place. In chronic dislocation, the condyle reduces itself during movements.
Habitual dislocation always has a history of an acute dislocation episode, and targeted manual reduction is strictly required to return the joint to normal. In chronic dislocation, the jaw reduces spontaneously during articulation.
What is the main difference between osteoarthritis and TMJ arthritis?
In osteoarthritis, cartilage is destroyed primarily, while reactive synovitis and inflammation join secondarily, running mildly and episodically.
What is the difference between TMJ dysfunction and osteoarthritis?
Osteoarthritis is a degenerative-destructive disease primarily affecting the articular cartilage, followed by bone tissue proliferation (sclerosis, osteophytes). Dysfunction, however, is mainly associated with muscle spasm and internal derangements, often without destruction of bony structures.
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