Exam 2 Flashcards
Anterior Guidance
Influence of the contacting surfaces of anterior teeth on tooth limiting mandibular movements. The steepness of the lingual surfaces of max anterior teeth determines the amount of vertical movement of the mandible.
Condylar guidance
Mandibular guidance generated by the condyle and articular disc traversing the contour of the glenoid fossa. It depends on the steepness of the articular eminence.
Working side contacts
Contacts of teeth made on the side of the articulation toward which the mandible is moved during working movements.
Non working or balancing side interference
Undesirable contacts of the opposing occlusal surfaces on the non working side (which interferes with the working side occlusal contacts.) one of the features of ideal occlusion is ABSENCES of posterior interferences.
Occlusal equilibration
The modification of the occlusal form of the teeth with the intent of the equalizing occlusal stress, producing simultaneous occlusal contacts or harmonizing cuspal relations.
When do we do occlusal equilibration?
When managing certain TMD after the occlusal appliance therapy has eliminated TMD symptoms and to compliment treatment associated with major occlusal changes like Orthodontics and Prosthodontics
Primary goals of equilibration or selective grinding
- With the condyles in CR (musculoskeletal stable position) and the articular discs properly interposed, all possible posterior teeth contact evenly and simultaneously between centric cusp tips and opposing flat surfaces.
- When excursive movements happen, laterotrusive contacts on the anterior teeth disocclude the posterior teeth.
- When the mandible is protruded, contacts on the anterior teeth disocclude the posterior teeth
Posselts envelope of motion
Term that refers to the range of motion of the mandible. The shape of the envelope carries depending on the plane, but it generally resembles a beak, a shield, or a diamond
What is the envelope of motion useful for?
Studying the anatomy and function of the TMJ and understand the relationship between the position of the teeth and the movement of the jaw
3 planes of movement
Sagittal, frontal, horizontal
Mandibular movements in sagittal plane
ICP= MIP
RCP = Retruded contact position
R = rotation
T= translation
Pr= maximum protrusion
E = Edge to edge
Mandibular movement frontal plane
Shield shape
1 = jaw movement to the right
2= depression of mandible to maximum opening
3= jaw movement to the left
4 = depression of mandible to max opening
Mandibular movement in horizontal plane
Diamond shape
RCP= retruded
ICP = intercuspal position
R= maximum lateral movement
2 movements for mouth opening
Rotation
Translation
Rotation
Occurs in the inferior joint cavity
Opening of 20 -25 mm
Translation
Occurs in the superior joint cavity
Opening of 25-35 mm
Maximum opening
45-55 mm
Lateral movement
10-12 mm
Protrusive movement
8-10 mm
Articulator
Mechanical instrument that represents the TMJ and jaws, to which maxillary and mandibular casts may be attached to stimulant some or all mandibular movements
Facebow
Instruments used to record the spatial relationship of the maxillary arch to some anatomical reference point or points (Condyles horizontal axis and one other selected anterior point) and then transfer the relationship to an articulator
Class I
Only vertical motion is possible
Accepts a single static registration
Class II
Permits horizontal and vertical motion but does not orient the motion to the TMJs
Class III
Instruments that stimulates condylar pathways by using averages of mechanical equivalents for all or part of the motion.
Semi-adjustable
Class Iv
Instrument that will accept 3D dynamic registrations, allow for orientation of the casts to the TMJs and simulation of mandibular movements.
Fully adjustable.
Components of the articulator
Condylar guidance
Anterior guide pin
Anterior guide table
Member
Mounting plate
Condylar guidance
Lateral and horizontal condylar inclination - represents the posterior determinants
Anterior guide pin
Rigid rod attached to one member contacting the anterior guide table of the opposing member. Maintains vertical separation
Anterior guide table
Where the anterior guide pin rests to maintain VDO and influence articulator movements. It influences the degree of separation of the casts in all relationships
Member
Upper member holds maxillary cast and lower member holds mandibular casts
Mounting plate
Removable metal or resin devices that attaches to the superior and inferior members of the articulator which are used to attach casts to articulator
Functional mandibular movements
All normal, proper or characteristic movements of the mandible made during speech, mastication, yawning, swallowing, and other associated movements
Occlusal trauma
Trauma to the periodontium from functional or parafunctional forces causing damages to its attachment by exceeding its adaptive and reparative capacities.
Primary and secondary
Primary occlusal trauma
Forces acting on teeth with normal periodontal support
Secondary occlusal trauma
Forces acting on teeth with decreased periodontal support
Parafunction
Disordered function like clenching and grinding of the teeth
Bruxism
Parafunctional grinding of teeth. It is an oral habit consisting of involuntary rhythmic or spasmodic nonfunctional gnashing, grinding or clenching of teeth. It may lead to occlusal trauma
3 main skeletal components
Maxilla
Mandible
Temporal bone
Maxilla
-upper facial skeleton
-2 maxillary bones fused at midpalatal suture
-dentoalveolar support
-bony attachment to skull
Mandible
-body and ramus
-lower facial skeleton
-dentoalveolar support
-no bony attachment to skull (muscle and ligament suspension, mobile)
-processes of the ramus (coronoid and condylar process)
Temporal bone
Supports the mandible at articulation with cranium
Mandibular condyles
-Portion of the mandible that articulates with cranium bilaterally
-condylar process in made of condyle and condylar neck
-condyle has medial and lateral poles
- medio-lateral (18-23mm)
- anteroposterior (8-10mm)
Glenoid fossa
-site of mandibular condyle articulation
-oval depression on inferior aspect of temporal bone
-located anterior to external auditory meatus
Articular eminence
-forms anterior limit of the mandibular fossa
-convex prominence of thick dense bone
-variable degree of convexity (dictates protrusive path of mandibular condyle)
Gross anatomy of TMJ
-Complex diarthrodial joint with 2 functional movements
-rotatory and sliding
Rotatory movement
Inferior compartment between mandibular condyle and articular disc
Sliding (translation)
In superior compartment between disc and temporal component
Articular disc
-Divides joint space into superior and inferior compartments
-Avascular dense fibrous CT
-biconcave, oval in shape
-ant and post bands with an intermediate zone in between
-medial and lateral attachments
Superior compartment
Between disc and mandibular fossa
Inferior compartment
Between disc and condyle
Retrodiscal tissue
-post attachment
-bilaminar zone
-loose neurovascular tissue bordered by 2 lamina - superior and inferior
Superior lamina
Temporal posterior attachment
Inferior lamina
Condylar posterior attachment
TMJ capsule
-Fibrous and no elastic membrane surrounding the TMJ
-function is to create a seal for joint space
-stability
-limits separation and range of movement of articular components- prevents tissue damage and lateral and medial dislocation of joint
TMJ ligaments
-Thick fibrous tissue limiting joint movement
-sphenomandibular ligament
-stylomandibular ligament
Masticatory muscles
-masseter
-temporalis
-medial pterygoid
-lateral pterygoid
Clinical importance of masticatory muscles
-muscles of mastication maintain postural position of mandible at rest against gravity
- TMJ disorders frequently involve pain
Accessory muscles of mastication
-Suprahyoid muscles
-infrahyoid muscles
-platsyma
-orbicularis oris
-buccinator
Suprahyoid muscles
Digastric, stylohyoid, mylohyoid, geniohyoid
Infrahyoid muscles
Omohyoid, sternohyoid, sternothyroid, thyrohyoid
Masseter
Quadrilateral, covers lateral aspect of ramus
Superficial part, deep head
Masseter superficial part = origin
Inferior border of the ant 2/3 of zygomatic arch
Masseter Superficial part= insertion
Angel of the mandible
Masseter Superficial part action
Elevation, bilateral
Ipsilateral, excursion
Protrusion, bilateral
Masseter Deep head origin
Inf border of post 1/3 and internal aspect of zygomatic arch
Masseter Deep head insertion
Lateral superior ramus
Masseter Deep head action
Elevation, bilateral
Ipsilateral excursion
Retrusion, bilateral
Temporalis
Fan shaped
Temporalis origin
Inf temporal line of skull, temporal fossa
Temporalis insertion
Coronoid process
Temporalis action
Elevation, bilateral
Retrusion (post fibers)
Disc
Dense fibrous CT, slightly innervated
Articular surface of condyle located on the line intermediate zone of the disc
Maintains morphology unless destructive forces or structural changes in joint. If that happens = morph of disc can be irreversibly altered —> biomechanical changes
Acts as non-ossified bone contributing to both joint systems
Functions as true articular surface in both joint systems
Synovial fluid
Both join cavities are filled with synovial fluid
2 purposes
2 purposes of synovial fluid
Articular surfaces are nonvascular, synovial fluid acts as a medium for providing metabolic requirements to these tissues.
Serves as a lubricant between the articular surfaces during function
Retrodiscal tissue
Loose CT attaches to posterior part of disc.
Highly vascularized and innervated.
Innervation of TMJ
Trigeminal nerve (V3) mandibular nerve - auriculotemproal nerve
Biomechanics of TMJ
Extremely complete joint system.
Two TMJs connected to the same bone (mandible), cant act without influencing the other.
Structure and function has 2 systems
Interarticular pressure happens
One joint system TMJ
Tissue that surround the inferior synovial cavity (condyle and articular disc). The disc and its attachment to the condyle is called the condyle-disc complex and is the responsible for the rotational movement in the TMJ
Second system TMJ
Made up of the condyle-disc complex functioning against the surface of the mandibular fossa. Translation occurs in this superior joint cavity between the disc and the mandibular fossa
Do the articular surfaces of the joint have any structural attachment or union?
No, but contact must be maintained for join stability
How is Stability of the joint maintained?
Constant activity of the muscles
3 important principles of the biomechanics of the TMJ
- Ligaments do not actively participate in the normal function of the TMJ
- Ligaments do not stretch, they ELONGATE
- Articular surfaces of the TMJ must maintain constant contact (produced by muscles of mastication (elevator))
Mechanics of mandibular movement
Rotation
Translation
Rotation
Occurs as movement within the inferior cavity of the joint. Between the superior surface of the condyle and the interior surfaces of the articular disc.
Can occur in all 3 planes, 20-25 mm
Translation
Occurs when the mandible moves forward. Happens within the superior cavity of the joint between the superior surface of the articular disc and the inferior surface of the articular fossa.
40-60 mm max opening
Temporomandibular disorders
Several clinical problems that involve the masticatory musculature, the TMJ and associated structures or both, identified as a major cause of nondental pain
Most common symptoms of disorders
Pain, limited or asymmetric mandibular movements, TMJ sounds, headaches, earaches, jaw pain, facial pain, coexist with other cranial mandibular and Orofacial pain conditions
Epidemiology of TMD
40-75% at least one sign of joint dysfunction
~33% at least one symptom
50% joint sounds
5% mouth opening limitation
Children less than adults
More women (they seek treatment more)
Only 3.6% to 7% need treatment
Etiology of TMD
Predisposing factors (increase risk of TMD), initiating factors (onset of TMD), perpetuating factors (factors that interfere with healing or enhance progression of TMD), long term successful management
Trauma
Any force applied to the mastication structures that exceeds the normal function load
Direct, indirect, micro
Direct trauma
Direct blow to structures, produces injury via impact, inflammation, structural failure, loss of function, onset occurs within 24-72 hours of the trauma
Indirect trauma
Sudden blow without direct contact to affected structures, whiplash injury, pathways of pain from cervical area to the trigeminal area, not uncommon to see symptoms of TMD following injury to neck without direct trauma to face or jaw
Microtrauma
Sustained and repetitious adverse loading of the masticatory system through postural imbalance or from parafunctional habits, postural habits, intensity and frequency of parafunctional jaw activity may be exacerbated by stress and anxiety, sleep disorders and medications, intense and persistent parafunctional can also occur in patients with neurological disorders = cerebral palsy, orofacial dyskinesia and epilepsy
Anatomic factors
Skeletal relationship, occlusal relationships
Must of the association noted were judged to be secondary to joint alteration and not etiologic
Skeletal relationship
Skeletal malformations, arch discrepancies, post injuries to teeth.
Steepness of the articular eminence
Occlusal relationships does literature support the role of etiology in TMD?
Literature does not support the role of occlusion in etiology of TMD
Overbite, anterior open bite, over jet, unilateral posterior crossbite, missing posterior teeth
Overbite
Associated with more joint sounds and muscle tenderness
Anterior open bite
Associated with condylar changed and rheumatoid arthritis
Overjet
TMD symptoms and osteoarthritis changes
Unilateral posterior crossbite
More common in TMD patients
Missing posterior teeth
Internal derangement and osteoarthritic changes
Pathophysiologic factors
Systemic - managed in cooperation with physician
Degenerative, endocrine, infectious, metabolic, neurological, rheumatologist, vascular disorders
Psychosocial factors
Anxiety and depression
Alcohol, tranquilizers, narcotics, contributes to the chronic its of many TMD patients
Medial pterygoid origin deep head
Pterygoid fossa between lateral and medial pterygoid plates
Medial pterygoid origin superficial head
Pyramidal process of palatine bone, maxillary tuberosity
Medial pterygoid insertion
Angle of the mandible medial ramus
Medial pterygoid action
Elevation, bilateral
Protrusion, bilateral
Contralateral excursion, unilateral
Lateral pterygoid superior head origin
Greater wing of sphenoid bone, inferior aspect
Lateral pterygoid superior head insertion
TMJ capsule, disc, anterior condylar neck
Lateral pterygoid superior head action
Stabilization of disc position
Lateral pterygoid inferior head origin
Lateral pterygoid plate of sphenoid bone
Lateral pterygoid inferior head insertion
Condylar neck
Lateral pterygoid inferior head action
Protrusion, bilateral
Depression, bilateral
Contralateral excursion, unilateral
What is the only structure capable of retracting the disc posteriorly on the condyle?
The superior Retrodiscal lamina
What is attached to the anterior border of the disc and what happens when it is active?
Superior lateral pterygoid, the fibers will pull anterior and medially
What also attached to the neck of the condyle?
Lateral pteryoid, dual attachment does not allow the muscles to pull the disc forward
What happens when the inferior lateral pterygoid is protracting the condyle forward?
The superior lateral pterygoid is inactive. It activates during mandibular closure
What is the mechanism by which the disc is maintained with the translating condyle dependent on?
The morphology of the disc and interarticular pressure
