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Oral & Maxillofacial Surgery
Fifth Year

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  1. 1. TMJ  iBooks Author
  2. 2. Chapter 1 Anatomical Consideration  iBooks Author
  3. 3. Section 1 Applied Anatomy OBJECTIVES 1. To describe the different structures of TMJ. 2. To describe the biomechanics related to Jaw movement. TMJ Synonyms •Craniomandibular articulation •Diarthroidal joint •Mandibular joint •Synovial joint 2  iBooks Author
  4. 4. Section 2 Why TMJ is a unique Joint 1.It functions bilaterally in harmony Parts Of The Joint: 2.The articular disc is movable during joint 1.Articular eminence movement 2.Articular fossa 3.The articular surfaces are covered by fibrocartilage and not hyaline cartilage 4.The fibrocartilage is considered as the 3.Condyle 4.Capsule 5.Ligaments growth center for the mandible 6.Synovial Fluid 7.Articular disc 3  iBooks Author
  5. 5. Articular Eminence A raised area located on the articulated surface of the temporal bone. Articular Fossa The part of the temporal bone which mates to the upper surface of the disk is the glenoid (or mandibular) fossa. Condyle The part of the mandible which mates to the under-surface of the disc. The condylar head is about 20 mm wide mediolaterally and 10 mm thick dorsoventrally. 4  iBooks Author
  6. 6. Capsule Ligaments The capsule is a fibrous membrane that There are three ligaments associated with the surrounds the joint and incorporates the TMJ: one major and two minor ligaments. articular eminence. The major ligament: The Temporomandibular Ligament, is It attaches to the articular eminence, the actually the thickened lateral portion of the articular disc and the neck of the mandibular capsule, and it has two parts: an outer oblique condyle. portion and an inner horizontal portion. 5  iBooks Author
  7. 7. The two minor ligaments: The sphenomandibular ligament runs from The stylomandibular ligament separates the infratemporal region (anterior) from the the spine of the sphenoid bone to the lingula of mandible. parotid region (posterior), and runs from the styloid process to the angle of the mandible 6  iBooks Author
  8. 8. Synovial Fluid Function: The synovial fluid is a derivative of plasma These ligaments are important in that they define the border movements or the farthest extents of movements of the mandible. Movements of the mandible made past the extents functionally allowed by the muscular attachments will result in painful stimuli, and thus, movements past these more limited borders are rarely achieved in normal and contains low-molecular weight molecules, including glucose, urea, uric acid and proteins. The level of these molecules varies depending on the degree of inflammation in the joint. Total protein in normal synovial fluid is approximately 1.5 to 1.8 g/dl. In the inflamed state, this level increases. function. 7  iBooks Author
  9. 9. Articular Disc The articular disc is a fibrous extension of the Movie 1.1 Normal TMJ movement capsule in between the two bones of the joint. The disc functions as articular surfaces against both the temporal bone and the condyles and divides the joint into two sections. It is biconcave in structure and attaches to the condyle medially and laterally. The anterior portion of the disc splits in the vertical dimension, coincident with the insertion of the superior head of the lateral pterygoid. The posterior portion also splits in the vertical dimension, and the area between the split continues posteriorly and is referred to as the retrodiscal tissue. Different structures in harmony The disc features three zones of varying thickness. A prominent posterior thickening sits atop the condyle and fills the mandibular fossa above when the mandible is at rest. 8  iBooks Author
  10. 10. A less prominent anterior thickening lies just Unlike the disc itself, this piece of connective below the posterior of the articular eminence, tissue is vascular and innervated, and in some and a relatively; thin intermediate zone lies cases of anterior disc displacement, the pain between them. felt during movement of the mandible is due The resulting configuration is a biconcave disc that serves to provide reciprocal articular to the condyle compressing this area against the articular surface of the temporal bone. surfaces between its inferior aspect and the Joint Cavities. The disc effectively divides condyle and between its superior surface and the joint cavity into two distinct upper and the mandibular fossa and eminence. Only the lower compartments that allow two types of peripheral attachments of the disc contain joint movement, a hinge movement in the blood vessels; the disc its is avascular, getting lower compartment and a translatory its nourishment by diffusion from the movement in the upper compartment. periphery and from synovial fluid. 9  iBooks Author
  11. 11. Section 3 Innervation and vascularization Nerve supply Had there been any nerve fibers or blood vessels, people would Sensory innervation of the TMJ is derived from the auriculotemporal and masseteric branches of V3. bleed whenever they moved their jaws; however, movement itself would be too painful The posterior and posterolateral regions of the joint capsule contain free nerve endings of C and A delta types fibers that conduct pain impulses from the joint. This is a part of a feedback mechanism that limits excessive mandibular movements. The re t ro d i s c a l i n f e r i o r l a m e l l a c o n t a i n s p ro p r i o c e p t i v e mechanoreceptors that detect condylar movement and position. Blood Supply Its arterial blood supply is provided by branches of the external carotid artery, predominately the superficial temporal branch. Other branches of the external carotid artery namely: the deep auricular artery, anterior tympanic artery, ascending pharyngeal artery, and maxillary artery- may also contribute to the arterial blood supply of the joint. In order to work properly, there is neither innervation nor vascularization within the central portion of the articular disc. 10  iBooks Author
  12. 12. Chapter 2 Biomechanics of the joint during function  iBooks Author
  13. 13. Section 1 Different Jaw Movements OBJECTIVES 1. To discus different muscles action in relation to Jaw movement. The two movements that occur at this joint are: 1.anterior gliding 2.hinge-like rotation. When the mandible is depressed during opening of the mouth, the head of the mandible and articular disc move anteriorly on the articular surface until the head lies inferior to the articular tubercle. 12  iBooks Author
  14. 14. The mandible is moved primary by the Movie 2.1 Lateral movement four muscles of mastication: the masseter, medial pterygoid, lateral pterygoid and the temporalis. Movie 2.2 Medial pterygoid action These four muscles, all innervated by V3, work in different groups to move the mandible in different directions. Contraction of the lateral pterygoid acts to pull the disc and condyle forward within the glenoid fossa and 13  iBooks Author
  15. 15. mandible and the temporalis by pulling Movie 2.3 Muscle action during opening up on the coronoid process. down the articular eminence; thus, action of this muscle serves to open the mouth. The other three muscles close the mouth; the masseter and the medial pterygoid by pulling up the angle of the 14  iBooks Author
  16. 16. Jaw Movements: Muscle Action Actions Muscles Depression (Open mouth) Lateral pterygoid Suprahyoid Infrahyoid Elevation (Close mouth) Temporalis Masseter Medial pterygoid Protrusion (Protrude chin) Masseter (superficial fibres) Lateral pterygoid Medial pterygoid Retrusion (Retrude chin) Temporalis Masseter (deep fibres) Side-to-side movements (grinding and chewing) Temporalis on same side Pterygoid muscles of opposite side Masseter 15  iBooks Author
  17. 17. Chapter 3 Internal Derangement  iBooks Author
  18. 18. Section 1 What is Internal Derangement OBJECTIVES 1. Define Internal Derangement. 2. Describe signs & Symptoms related to it. 3. Identify patients with disc problems. 4. Differentiate between the two types of disc displacement. 5. Choose the correct line of treatment. Definition: It is defined as an abnormal positional and functional relationship between the disk and articulating surfaces. Emshoff R. and Rudisch A. (2003) defined internal derangements of the temporomandibular joint as an abnormal relation of the articular disc to the mandibular condyle and the articular eminence. Jaw pain, clicking of the joint, irregular and limited movement of the jaw are the characteristic symptoms of this disorder. 17  iBooks Author
  19. 19. Prevalence: Internal derangement and associated complications are the most common pathologic entities affecting the jaw. Solberg W.K. (1979) 82% of patients presenting with pain and functional disturbance of their TMJ will have displaced disks when examined with magnetic resonance imaging. The overall prevalence of symptomatic disk displacement or internal derangement may range between 20% and 30%, making them frequently encountered conditions. 18  iBooks Author
  20. 20. Disc Displacements Anterior disk displacement of the TMJ Movie 3.1 Disc displacement with reduction is a malrelationship of the disk to the condylar head and articular eminence. Although the disk may displace m e d i a l l y, l a t e r a l l y, o r ( r a r e l y ) posteriorly to the condyle, it generally displaces anteriorly. First stage in the sequence of events leading to osteoarthritis. TMJ morphology, have shown a path of progression that includes changes The video indicates the altered not only in the disc position, but also relation between the condyle and the in its configuration. disc during opening and closing. 19  iBooks Author
  21. 21. Internal derangements can be divided into 2 categories: anterior disk displacement with reduction and anterior disk displacement without reduction. The Signs & Symptoms: Disc displacement is considered to be associated with clinically noticeable clicking noises on opening and closing of the mouth as long as the condition in which the disk is located anteriorly and slips back into its normal position during opening of the mouth is called anterior disk displacement with reduction; the opposite condition is known as anterior disk displacement without reduction. disc reduces to its normal position on opening. Disc Displacement With Reduction: 1.Pain 2.Joint sounds (single, short duration) 3.Catching sensation during mouth opening 20  iBooks Author
  22. 22. 4.Deviation in opening pathway Disc Displacement Without Reduction: Pathogenesis: 1.Limited mandibular opening TMJ disc displacement results from 2.Normal eccentric movement to the ipsilateral side 3.Restricted eccentric movement to the contralateral side. its inability to slide smoothly due to increased friction or degenerative changes in the joint surfaces. The sequence of events, starting with increased friction in the upper joint 4.Pain compartment and culminating in disc 5.J o i n t s o u n d s ( l o n g d u r a t i o n sounds ) displacement. Activation of various parafunctions, such as clenching, compromises the lubrication system in the upper TMJ compartment. 21  iBooks Author
  23. 23. The resulting increased friction displaced disc is shared between two p re v e n t s t h e d i s c f ro m s l i d i n g vectors, one of which is directed together with the condyle. f o r w a rd . A p p a re n t l y, o n m o u t h On jaw opening, the condyle is pulled away from the disc by the inferior head of the lateral pterygoid muscle. closure, the superior belly of the lateral pterygoid muscle pulls the disc anteriorly. As a result, the ligaments joining the Subsequently, during mouth opening, disc to the condyle are gradually the condyle, which is now posterior to stretched, and the ‘mobilized’ disc the loose disc, gradually pushes it gravitates slightly downward and down the slope of the eminence, forward. displacing it further forward. Subsequently, on clenching, the Since the lateral articular disc bears unstable disc is propelled forward by the bulk of the shearing and pressure from the condyle. At this compressive loads, persistent loading point, the force on the slightly 22  iBooks Author
  24. 24. tends to drive it in a medial direction, which is the ‘path of least resistance’. Diagnosis: Gallery 3.1 MRI Etiology: 1.TRAUMA 2.FUNCTIONAL OVERLOADING 3.JOINT LAXITY 4.MASTICATORY MUSCLE SPASM 5.INCREASED FRICTION Disc displacement with reduction (arrows pointing to the disc) History 23  iBooks Author
  25. 25. Physical examination(TMJ clicking, Pain, Limitation of mandibular Treatment Extra-articular therapy: opening) 1.Splint therapy Radiographic evaluation: 2.Therapeutic manipulation OPG / MRI 3.Physical therapy Intra-articular therapy: 1.Surgical treatment 2.Arthroscopy 3.Arthrocentesis 24  iBooks Author
  26. 26. Arthrocentesis: Nitzan technique marked an evolution et al (1991) described a towards less surgical treatment. technique of irrigation of the upper Arthrocentesis is the most recent compartment of the TMJ with Ringer's s u rg i c a l a p p ro a c h f o r i n t e r n a l lactate solution to treat limited mouth derangement of the TMJ. opening due to internal derangement. The authors called this technique `arthrocentesis'. In the past many cases of anterior displacement of the disc or closed lock that did not improve with medical They reported an increase in mouth t re a t m e n t ( b i t e p l a t e s , m u s c l e opening from a range of 12±30 mm relaxants, diet and physical therapy) prior to the procedure, to 35±50 mm were initially treated with surgical following it. On a visual analogue repositioning of the disc and scale of 0±15, the pain decreased arthroplasty of the mandibular fossa. from a mean rating of 8.75 to 2.3. This 25  iBooks Author
  27. 27. Arthrocentesis has an intermediate the vacuum effect within the joint place between the medical and the compartment. surgical forms of treatment. Ease, lower cost of materials and excellent published results so far include this technique in the international protocol In 2003, Reston and Turkelson performed a meta-analysis of surgical Gallery 3.2 Arthrocentesis technique for the treatment of TMJ dysfunction. A r t h ro c e n t e s i s i s a s i m p l e y e t effective treatment of TMJ disorders, and it requires minimal invasion. Significant improvements in width of mouth opening have been reported with proven long-term results. It is speculated that the increase in mouth opening results from the elimination of 26  iBooks Author
  28. 28. treatments for TMJ articular disorders. They concluded that among patients refractory to nonsurgical Mechanism of Action: I. Reduction in pain level: therapies, surgical arthrocentesis and Arthrocentesis reduces pain by removing arthroscopy were most effective for inflammatory mediators from the joint. patients with disc displacement The combined treatment of without reduction. arthrocentesis and Sodium Hyaluronate It is suspected that lavage under sufficient hydraulic pressure could widen the narrowed joint space and release adhesion in the joint space. Arthrocentesis with sufficient pressure could be effective for closed injection may improve the results due to the long-term lubricating effect of Sodium Hyaluronate, which prevents the onset of inflammatory mediators that are responsible for pain. II. Maximal Mouth Opening: lock cases with adhesions in the Arthrocentesis under high pressure is an upper joint compartment. effective method to regain normal mouth 27  iBooks Author
  29. 29. opening in closed lock cases. This effect the anterior margin of the bony external is usually due to elimination of the auditory canal as it crosses over the adhesions around the disc. Also the posterior aspect of the zygomatic arch (a lubricating effect of Sodium Hyaluronate range of 8 to 35mm). The main trunk of which either maintains lubrication and the bifurcation of the facial nerve is minimizes wear and tear mechanically, or located a mean distance of 23 mm (a plays a role in nutrition of the avascular range of 15 to 28 mm) inferior to the parts of the disc and condylar cartilage. lowest concavity of the bony external auditory canal. III. Clicking : Usually disappears due to decreased friction and lubricating effect. Greene MW et al found the tympanic plate to be located at a range of 6 to 9 mm anterior to the posterior tragus and Nearby Vital Structures: perpendicular to the skin at a mean The frontal branch of the facial nerve is depth of 25.4 mm (range = 19 to 32 mm). located a mean distance of 20 mm from 28  iBooks Author