ARTICULATIO Temporomandibular joint ■ paired joint, one on each side of the head, in which mandibula connects with the skull basis ■ Allows movement of the mandible for speech and mastication ■ one of the most frequently used articulation in the body ■ Adaptable Lateral pterygoid, superior part Articular tubercle ■ composed joint, complicated mechanism of movement Mandibular fossa Articular disk Head of mandible Joint capsule Lateral pterygoid, inferior part 1. JOINT SURFACES 2. JOINT CAPSULE 3. DISCS OF THE JOINT 4. LIGAMENTS 5. JA W MO VEMENTS 6. EXAMINATION OF THE JOINT 7. TOPOGRAPHY RELATIONSHIP 1. JOINT SURFACES Caput mandibulae, mand. Condyle head Fossa mandibularis (articular fossa, joint pit) with sharper ridge posteriorly-postglenoid proccess Tuberculum articulare ossis temporalis -articular eminence Dorsal part of the joint pit is pars tympanica ossis ^=^-=5; temporalis - ATM therefore has a very narrow connection to the tympanic cavity and to meatus acusticus externus Articular surfices are covered by fibrous cartilage r < V Joint pit - dorsally concave, ventr. convex 2. JOINT CAPSULE ■ On temporal bone its attached to the margins of joint surfaces, on mandibula it reaches to collum mandibulae ■ Relatively free, the medial and lateral walls are reinforced by the medial and lateral ligaments ■ The superior capsular attachments are relatively loose, it wraps temporal bone's articular eminence and articular fossa ■ The inferior attachments are more tightly bound, to the condyle's neck ■The inner surfaces are covered by synovial membrane —> produces synovial fluid (viscous ^ liquid) —> which hepls to lubricate the joint, brings nutrients to avascular cartilage and it reduces a friction during movements 3. DISC OF THE JOINT ■ Discus articularis, inserted between mandibular head mandibular fossa and articular tubercle ■ An oval, firm, plate of fibrous cartilage ■ Reduces sliding friction ISfiS ■ Fully separates the joint cavity, capsule is connected to its joint margins, and divides ATM into 2 joints - 2 synovi cavities Articular surfaces are completely separated by disc to: 1. cranial / upper compartment discotemporal joint 2. caudal / lower compartment discomandibular joint ■ Disc is biconcave with fibrocartilaginous structure ■ Matrix of disc consists primally of colagen and elastic fibres ■ In the pars anterior and posterior run transverse collagens fibres ■ Based upon the function it is divided into anterior, intermedia d posterior partes Attachment of articular disc Upper synovial cavity J Jt»£ \ / Lower synovial cavity — ^^^V\ **7aV48M*7 . Articular ^x / --ca^e / | Blip' / JWi Disc attachment to / \m\ \ medial and lateral *^ 1 + * \ poles of condyle fv!cG' tk3'^FT left t0 ri§ht' 3 fr°ntal section through the condyle, disc capsule and fossa. The d,sc fibers curve down to insert into the poles of the condyle ? ' Medially and laterally is the disc attached to the inner periphery of the articular capsule -> tightly bound and to the condyle, causing the disc to translate with the condyle during movements. Anteriorly, it's attached to some fibres of superior head of lateral pterygoid muscle. ■ Posterior part of the articular disk, so-called bilaminar, separates into upper and lower laminae of collagen fibres both insert into the posterior wall ■ Between these laminae and the posterior wall is filled with retroarticular Zenker plastic pad )ad ar space, Posterior tubercle Mandibular fossa Upper synovial cavity Articular eminence Upper elastic lamina Superior head 'of lateral pterygoid muscle Articular disc Lower collagenous lamina Posterior part of capsule Inferior head of lateral pterygoid muscle Lower synovial cavity Anterior part of capsule FlG. 29-1. Longitudinal section through the TMJ. The pad is responsible for stabilizing the disk on the condyle and supplying the joint On opening of the oral cavity - depresion of mandible a Zenker plastic pad of retrodiscal tissue is filled with blood to the veins in the space between the posterior thick part of the disc and the condyle as a result of negative pressi Physiologie disc position ■ Pars posterior of the disc lies on the superior portion of the condyle ■ In the centric condylar position the pars intermedia is located between anterosuperior convexity of the condyle and the articular protuberance Pars anterior lies in front of condvle Dislocation of the articular disc ■ Displacements of the disk in the anterior anteromedian or anterolateral direction ■ Posterior disk displacement - on rare occasions ■ The combination of ant. and lat. or medial displacement is called rotational displacement ■ Pure lateral or pure medial displacement is called sideways displacement ■ Chronic displacement is resulting in deformity of the disc ■ In approximately 10% of patients presenting with pain and dysfunction Trauma of the articular disc Mikrotrauma bruxism, stress, malocclusion, bad habits, chewing gum Macrotrauma an injury - either directly to the joint or to the head and neck intubation, lengthy dental work 4. LIGAMENTS OF THE TMJ Ligaments have three main functions: a) stabilization b) guidance of movement c) limitation of movement Articular: lateral medial... to rei rce the capsule Extraarticular stylomandibular sphenomandibular Lateral ligament From processus zygomaticus and tuberc. articulare —► collum mandibulae ■ A superficial, more vertically oriented part limits jaw opening ■ A deep, more horizontal part limits retrusion and laterotrusion Stylomandibular ligament From styloid process the posterior edge of the angle of the mandible ■ Restricts protrusive an mediotrusive movements + prevent excessive upward rotation tJoi Sphenomandibular ligament From sphenoidal spine —► lingula of the mandible ■ Limits protrusive and mediotrusive movement + passive jaw opening 5. MOVEMENTS OF THE TMJ > ATM is composed and paired joint, therefore it has complicated mechanism of movements > Functionally translation (gliding) movements occur in the discotemporal joint (discus articularis is shifting forwards and backwards) Rotational (hinge) movements are in discomandibular part (caput mandibulae is rotating along the transversal axis) > Both run simultaneously, bilaterally ^^^-s > Movements of the iaw involve the combination of gliding and rotational movements 5. MOVEMENTS OF THE TMJ Rotational movement - takes place in the lower compartment between the stationary disc and the moving condyle, the axis is transverse, movements accomplished are depression and elevation of mandible Gliding movement - takes place in the upper compartment between the superior surface of the disc, which is moving, and mandib. fossa, movements forward or backward - up and down the articular eminence Mandibular depression - the opening, the lowering of the lower jaw Lateral pterygoid + suprahyoid m. ■ With simple rotation at the joint can be achieved 15 - 20mm interincisor distance ■ During translation, the disc and condyle move under the articular eminence ^^^fl Mand. elevation - the closing of the mouth, the raising of the lower jaw Temporal + masseter + medial pterygoid m. ■ Translation - the condyles move backward and upwar along the articular eminence otation upward to attain centric position Mand. protrusion - shifting the entire jaw forwards Lateral et medial pterygoid + masseter m. ■ Slide the mandible forward ■ Maximal protrusion results in the lower (mandibular) incisors being a few mm anterior to the maxillary incisors Mand. retraction Temporal + masseter m ■ Move the mandible posteriorly ^ Condyles move backward and upward and reoccupy the mandibular fossa Laterotrusion, lateral deviation Lateral et medial pterygoid + masseter + temporal m. The condyle move to the right or to the left side During lateral movements, the each of condyle moves differently: on the working side - rotates around a vertical axis and moves lat. and ant. ^ on the nonworking side - ant., inf. and med. Hyper mobility Discus articul. with caput mandibulae could slide in front of tuberculum articulare into fossa infratemporalis Subluxation incomplete dislocation of a joint in which the patient is able to close his or her mouth without assistance Luxation (true dislocation) Joint is displaced from its articulations and requires manipulation by another individual to return to its normals position (cannot spontaneously return into its physiological position) Hypo mobility Ankylosis (intracapsular) The fibrous adhesions or bony fusion between condyle, disc, glenoid fossa, and eminence Pseudoankylosis (extracapsular) Pathology extrinsic to the joint Palpation of the preaurikular area Auscultation 7. TOPOGRAPHY RELATIONSHIP Cranially medial cranial fossa Dorsally external auditory tube Laterally glandula parotis , n.VII superficial temp, a.,v. auriculotemporal n. Medially chorda tympani, a. tympanica ant. ß