Components of the temporomandibular joint A, articular eminenceC, condyle;D, articular discE, external auditory meatusL, lateral pterygoid muscleR, retrodiscal tissue

Masticatory system as a functional unit1. Jaws 2. Teeth3. Temporomandibular joints (tmjs) 4. Associated ligaments5. Muscles of mastication6. Tongue7. Cheeks8. Lips9. Sensory motor innervation (and vasculature)

In the edentulous patientLost

Teeth Periodontal ligament nerves

Tongue and other structuresFunctional anatomyControl and limits of jaw and joint motionRelationships Control of the lipsPhysiological environment

Ideal occlusion That are harmonious with the existing tmjs

and masticator)1 musclesStable occlusal contacts Vertical dimension of occlusion

Complexity of mandibular movementsMany different mandibular movements occur

during MasticationSpeechSwallowingRespirationFacial expressionParafunctional movements

Bruxism Clenching

Knowledgeable of mandibular movementsTo understand various aspects of occlusion

To arrange artificial teeth

To select and adjust recording devices and articulators

Factors that regulate jaw motionThe direction of the movement

Neuromuscular system

Limited by the movement of The two condyles And the guiding influences of the contacting teeth

The condyles and teeth modify mandibular movements initiated by the neuromuscular system

Influence of opposing tooth contactsThe manner in which the teeth occlude is related

Occlusal surfaces of the teethMuscles. Tmjs Neurophysiological components

Including the patient's mental well-beingOcclusal surfaces of the teeth should meet

Evenly on both sides. Mandible is not deflected its normal path of

closureArc the dentures displaced from the residual

ridges

When mandibular movements are madeWith the opposing teeth of complete dentures

in contact The inclined planes of the teeth should pass

over one another smoothly Not disrupt the influences of the condylar

guidance posteriorly and the incisal guidance anteriorly.

All mandibular motion is either ROTATION or TRANSLATION Rotational movements

In the lower compartment of the TMJ Between the superior surface of the condyles

and the inferior surface of the articular disk. Translatory, or gliding, movements of the

mandible Take place in the upper compartment of the

TMJ Between the superior surface of the articular

disk as it moves with the condyles and the inferior surface of the glenoid fossa.

In a healthy jointThe condyle is in a superoanterior position in the fossa with the articular disc interposed when the teeth are in maximum intercuspation

In a healthy jointIn the initial stage of opening, the condyle rotates in position, with the disc remaining stationary

In a healthy jointIn maximum opening, the condyle translates forward, with the disc still interposed

Muscular involvement in jaw motionIncreased activity during

Any jaw movement. Movement of the mandibleFixation on a given positionStabilization

Neuromuscular regulation of mandibular motionMastication is a programmed event

In a "chewing center" Located within the brain stem

Probably in the reticular formation of the pons

Conscious effortNot required for the continuation of chewingEither induce or terminate chewing

Sensory impulses From the orofacial region Modify the basic cyclic pattern of the chewing

center to achieve optimal function

Peripheral

influences

Peripheral

influences

Jaw reflexes

Jaw reflexes

Motion regulation The impulses initiated at the subconscious

level can produce involuntary movements or modify voluntary movements

Impulses from the subconscious level, including the reticular activation system, also regulate muscle tone, which plays a primary role in the physiological rest position of the mandible

Envelop of motion

The Envelope of Motionlimits of possible

motion and certain mandibular reference positions

Envelope of motion (mandibular border movement area) in the sagittal plane.

•CO, Centric occlusion;

•CR, centric relation;

•MHO, maximum hinge-opening position

• MO, point of maximum opening of the jaws

•P, most protruded position of the mandible with the teeth in contact

•Rest, postural rest position

Envelope of motion (mandibular border movements) in the frontal plane•CO, Centric occlusion

•MO, point of maximum opening of the jaws

• Rest, postural rest position.

Postural rest position of the mandible hypotheses Active mechanism

This position is assumed only when the muscles that close the jaws and those that open the jaws are in a state of minimal contraction to maintain the posture of the mandible.

Passive mechanismTolds that the elastic elements of the jaw

musculature, and not only muscle activity, balance the influence of gravity.

The current consensus is that the physiological rest positionActively determined. Usually 2 to 4 mm below the maximum

intercuspation positionEMG rest position is usually several

millimeters lower than in the clinical rest position. Up to an interocclusal distance of about 10 mm

More accurate to refer to a "range of posture" rather than to a single rest position.

Rest position of the mandibleRelative stable for reasonable lengths of time.Factors can influence the postural rest position

Wear Loss of teethAgingGeneral health factorsPosition of the head

Head is reclined The distance between the teeth is less

Head is inclined The distance is greater.

Therefore the patient's head should be upright and unsupported

The mandible moves about a horizontal axis, as seen in a hinge axis opening.

Mandibular movement occurs around a vertical axis during a lateral excursion.

The mandible also rotates around a sagittal axis when one side drops down during a lateral excursion.

A protrusive movement occurs when the mandible moves forward

When the mandible moves into a left lateral excursion

the right condyle (A) moves forward and

inwardwhile the left condyle

(B)will shift slightly in a

lateroposterior direction.

Bennett angle(S'PB)

The Bennett angle used in articulators with an immediate lateral translation capability is measured from the sagittal plane after the

(I) immediate or early

lateral translation has occurred.

Bennett angleIn the nonworking condyle (NW)

The "traditional" Bennett angle

(SCB) measures the angle

from the sagittal plane to the endpoint of the movement of the condyle center.

The farther anterior a tooth the less the

influence of the temporomandibular joint (TMJ)

the greater the influence of the anterior guidance (AG).