MANDIBULAR MOVEMENTS

PREPARED UNDER THE GUIDANCE OF:Dr Mahesh VermaDr Sadhna MateDr Shubhra GillDr Rekha GuptaDr Nidhi SainiDr Anshum GuptaDr Aditi NandaDr Ashish Thomas KunnekelDr Dheeraj KoliDr Rajiv GuptaDr Sandhya RaniDr Sumit Dubey

MADE BY:

ASHI SINGH

FINAL YEAR

ROLL NO. 4

ANALYSIS OF OCCLUSION

“occlusion” simply means the contact between teeth.

The word ‘Centric'is an adjective.

It should only be used to qualify a noun. Centric what?

Centric Occlusion (CO): “ the occlusion of the oppossing teeth when the mandible is in centric relation . This may or may not coincide with the maximal intercuspal position.”

It can be described as the occlusion the patient makes when they fit their teeth together in maximum intercuspation. Common synonyms for this are Intercuspation Position (ICP), Bite of Convenience or Habitual Bite. It is the occlusion that the patient nearly always makes when asked to close their teeth together, it is the 'bite' that is most easily recorded. It is how unarticulated models fit together. Finally, it should be remembered that it is the occlusion to which the patient is accustomed ie the habitual bite.

CENTRIC RELATION

Centric Relation: "a maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective discs with the complex in the anterior-superior position against the slopes of the articular eminences."

Centric Relation (CR) is not an occlusion at all. CR has nothing to do with teeth because it is the only 'centric' that is “reproducible” with or without teeth present.

Centric Relation is a jaw relationship it describes a conceptual relationship

between the maxilla and mandible.

'uppermost and midmost' OR 'uppermost and rearmost' position.

There is support for the uppermost and foremost hypothesis from a study of anatomy: the bone and fibrous articulatory surfaces are thickest in the anterior aspect of the head of the condyle and the most superior aspect of the articular eminence of the glenoid fossa.

SIGNIFICANCE OF CENTRIC RELATION

a reproducible position of the mandible relative to the maxilla, and that this position is reproducible irrespective of the guidance that the occlusal surfaces of the teeth may provide.

Patients with no teeth still have a centric relation.

Furthermore there is inter- and intra-operator reliability in finding it.

MAXIMAL INTERCUSPATION

Maximum intercuspation "the complete intercuspation of opposing teeth independent of condylar position.“

it defines both the anterior-posterior and lateral relationships of the mandible and the maxilla, as well as the superior-inferior relationship known as the vertical dimension of occlusion.

LONG CENTRIC

Long centric is really just a “short protusion” -Frank cilanza

Long centric : “ the range of tooth contact in maximum intercuspation”

Freedom in centric occlusion occurs when the mandible is able to move anteriorly for a short distance in the same horizontal and sagittal plane while maintaining tooth contact.

"Long centric" concept is applied only for anterior teeth and occlusal movements from rather than toward the center.

An easier way of imagining Freedom in Centric Occlusion is to state that if the front teeth hit together as hard or harder than the back teeth, then there is no freedom in that centric occlusion. Two common examples of occlusions that may not have this freedom are firstly those which have an Angles Cl II div (ii) incisor relationship and secondly when anterior crowns have been provided with palatal surfaces which are too thick.

IDEAL OCCLUSION

1. The coincidence of Centric Occlusion in Centric Relation (CO = CR), when there is freedom for the mandible to move slightly forwards from that occlusion in the same sagittal and horizontal plane (Freedom in Centric Occlusion).

2. When the mandible moves there is immediate and lasting posterior disclusion (anterior guidance on front teeth).

RELATED ANATOMICAL STRUCTURES

MANDIBLE

BASIC TMJ ANATOMY

GINGLYMOARTHROIDAL JOINT

COMPUND JOINT It can be divided into 3 regions in

the sagittal plane. MANDIBULAR CONDYLE ARTICULAR CAPSULE AND

DISC TMJ LIGAMENTS: 3 PRINCIPLE

AND 2 ACCESSORY MANDIBULAR FOSSA SYNOVIAL TISSUES

MANDIBULAR CONDYLE

• The condyle is essentially ovoid, not spherical.

• Perpendicular to the ascending ramus of the mandible

• Dense cortical bone covered with dense fibrous connective tissue with irregular cartilage like cells.

MANDIBULAR FOSSA

Dense cortical bony surface of temporal bone

Posterior to the articular eminence

Posterior non articular fossa is formed by tympanic plate

Thin at the roof of the fossa and tympanic plate.

ARTICULAR CAPSULE

Ligamentous capsule surrounding the joint

Attached to the neck of the condyle and Around the border of the articular surface of the temporal bone.

Anterolateral aspect of the capsule may thicken and form the Temporomandibualr ligament.

ARTICULAR DISC

Biconcave oval structure interposed between the condyle and the temporal bone.

1mm in the middle and 2-3mm at the periphery

Dense collagenous connective tissue

Centre area is avascular and devoid of nerve.

PRINCIPAL LIGAMENTS

ACCESSORY LIGAMENTS

MUSCLES OF MASTICATION

METHODS OF STUDYING MANDIBULAR MOVEMENTS

CINEMATOGRAPHIC TECHNIQUE: By using motion picture

Cine-radiologic studies: Using serial tracing of successive frames of the film

Pantography : one of the best methods

1. MECHANICAL

2. ELECTRONIC PANTOGRAPHY

MECHANICAL PANTOGRAPHY BY STUART AND McCOLLUM Devices containing 2 face bows one fixed to the

maxilla and the other fixed to the mandible. One holds the writing device and other holds the

recording table. Recording in three planes: Horizontal, frontal,

sagittal. complex handling Size and weight are cumbersome Eg: Stuarts pantography, Granger pantography,

Denar pantography.

ELECTRONINC PANTOGRAPHY

BY HOBO AND TAKAYAMA (1983) Measures right and left eccentric movement

by means of small optoelectronic sensor fixed to the maxilla.

Sensors used is light weight Used in patients with 4 or more

osseointegrated implants

DETERMINANTS OF MANDIBULAR

MOVEMENT

POSTERIOR DETERMINANTS MORPHOLOGY OF THE TMJ: Shape of the articular eminence Steeper: longer the cusp Flat: shorter the cusp

Anatomy of the medial walls of the mandibular fossae

Allows more lateral translation: shortet Allows minimal lateral translation: taller

Configuration of the mandibular condylar process.

Greater the intercondylar distance : shorter the angle between laterotrusive and mediotrusive movt.

Lesser the intercondylar distance : larger the angle between laterotrusive and mediotrusive movt.

• DICTATES THE ACTUAL PATH AND TIMIMG OF THE CONDYLAR MOVEMENT.

ANTERIOR DETERMINANTS

RELATIONSHIP OF ANTERIOR TEETH Horizontal overlap Vertical overlap Maxillary lingual concavities

OCCLUSAL PLANE

More paralell to condylar guidance-shorter cusps

Less paralell to condylar guidance-longer cusps

CURVE OF SPEE• More convex shorter radius) – cusps must be shorter

• Less convex larger radius) – cusps may be longer

MANDIBULAR MOVEMENTS

CLASSIFICATION OF MANDIBULAR MOVEMENT: BASED ON THE DIMENSION OF MOVEMENT

ROTATION around sagittal axis around horizontal axis around frontal axis

TRANSLATION BASED ON THE TYPE OF MOVEMENT Rotation Protusion Retrusion Lateral movt.

laterotrusion Bennett movement

immediate side shift precurrent side shift progressive side shift

BASED ON THE EXTEND OF MOVEMENT Border movement

in horizontal plane sagittal plane coronal plane envelope of motion

Intraborder movements Functional movement Parafunctonal movement

BASED ON THE DIMENSION OF MOVEMENT

The complex 3 dimensional mandibular movements can be broken down into 2 basic components-

TRANSLATION ROTATION

Rotational Movement Rotational Movement • Rotation: “The process of turning around

an axis movement of a body about its axis.”

• Rotation is movement between the superior

surface of the condyle and the inferior surface of the articular disc.

When the mandible is in centric relation the condyles can rotate around a horizontal axis up to an opening of 20-25 mm measured at the central incisors.

If opening of the mandible continues beyond 20-25 mm then translation of the mandible occurs.

This pure rotational movement is also referred to as hinge movement and the axis is referred to as terminal hinge axis.

SAGITTAL AXIS OF ROTATION

Sagittal Axis of Rotation One condyle moves inferiorly out of the terminal

hinge position. Opposite condyle remains in terminal hinge position

HORIZONTAL AXIS

Horizontal Axis of Rotation Opening and closing motion Hinge axis Pure rotational movement Terminal hinge axis when the condyles are in their most

superior position

FRONTAL AXIS

Frontal/Vertical Axis of Rotation • One condyle moves anteriorly out of the terminal hinge position. • Opposite condyle remains in terminal hinge position • Does not occur naturally.

TRANSLATIONAL MOVEMENTS

Occurs when the mandible moves forward (protrusion), backward ( retrusion) & lateral

Occurs within the superior cavity of the joint. Mandibular movement in many mammals is

controlled by a pure hinge joint.. The three hypotheses concerning condylar

translation considered in a study are That it results in a center of rotation of the

mandible in the area of the mandibular foramen, minimizing displacement of the inferior alveolar neurovascular bundle during mandibular movement,

That it reduces the amount of stretch in the masseter muscle during opening, allowing the muscle to function within an efficient portion of the muscle fiber length-tension curve, and

That it prevents compromise of the airway and other cervical structures by the tongue and mandible during opening.

BASED ON THE TYPE OF MOVEMENT

PROTUSION PROTUSIVE

MOVEMENT :while incising or grasping the food.

Mandible translates forward and downwards.

Right and left condyle disc assemblies also move forward and downward a total movement of 10mm.

Forms an S shaped curve in the sagittal plane.

Angle formed by the protusive condylar path and the horizontal reference plane : CONDYLAR GUIDANCE ANGLE.

Mandibular anterior teeth protude forward and downward along the lingual concavities of the maxillary anterior teeth disoccluding the posterior : CHRISTENSON’S PHENOMENA

The orbits of the incisal point from maximum intercuspation to edge – edge occlusion : PROTUSIVE INCISAL PATH ( Mean length : 5mm).

The angle formed by the protusive incisal and the horizontal reference plane is called : INCISAL GUIDANCE.

Incisal guidance angle : 50-70 degree. Sagittal inclination of protusive incisal is steeper than the sagittal

inclination of protusive condylar.

RETRUSION

RETRUSIVE MOVEMENT: Mandible is forcefully moved behind centric relation.

Achieved by the fibres of Temporalis, Digastrics and deeper fibers of masseter .

About 0.5mm Determinants :

fibres of bilamina and TM ligament contour of the posterior slope of glenoid fossa

LATEROTRUSION When the mandible moves away from the mid sagittal

plane . Can occur on the right or left side. Usually takes place while chewing food. When the condyle moves laterally the condyles do not

share the same path of movement. Eg: If the right condyle is moving towards the right side:

right condyle is considered as the working /laterotrusive condyle and the left condyle is the nonworking/ mediotrusive/ balancing condyle

The working side is not limited by any anatomic structures other than the TM ligament, hence can take any of the 5 condylar paths

laterally outwards : laterotrusion laterally + downwards :laterodetrusion laterally + forward: lateroprotusion laterally +backwards : lateroretrusion.

The non working condyle will move along an arc forward, downward and medially as determined by the entoglenoid process of the glenoid fossa.

Bennett Angle

Angle formed between the sagittal plane and the average path of the advancing/balancing condyle as viewed in the horizontal plane during lateral mandibular movements.

Mean : 16 ° (Hobo and Machizuku)

BENNETT MOVEMENT

“ The bodily lateral movement or lateral shift of the mandible resulting from the movements of the condyles along the lateral inclines along the mandibular fossae in the lateral jaw movement.”

Its recorded in the region of the translating condyle of the non working side .

During lateral movement, the mandible shifts by 1 to 4 mm towards the working side , called the Bennett movement.

This shift may occur before or along with laterotrusion.

The Bennet movement has 3 attributes: AMOUNT: more medial the wall – medial the pole of the orbiting

condyle, greater the amount of Bennet movement. Looser the TM ligaments – rotating condyle – greater the

movement. TIMING: When Bennet movement occurs early a shift is seen

before the condyle begins to translate from the mandibular fossa. This is called immediate shift If it occurs in conjunction with eccentric movements : Progressive

shift . DIRECTION: The direction of Bennet movement depends

primarily on the direction taken by the rotating condyle during the bodily movement.

IMMEDIATE SIDE SHIFT : Lateral translation before forward movement of the non working condyle.

The mandible shifts before the forward movement of nonworking condyle . Range: 1-4 mm

PRECURRENT SIDE SHIFT : Major translation during the first 2-3 mm of forward movement of non working side.

Shifts rapidly during the first 2-3mmand then continues to shift less rapidly.

If major movement is in the first 4mm of anterior movement of non working condyle, its called DISTRIBUTED SIDE SHIFT.

PROGRESSIVE SIDE SHIFT/BENNETT SIDE SHIFT : Lateral translation during the first 2-3 mm of forward movement of non working condyle.

Gradual and does not change with time.

ATTRIBUTES OF BENNET MOVEMENT DETERMINE THE CUSPAL MORPHOLOGY Increased immediate shift : shorter posterior

cusps In laterosuperior movement : shorter

posterior cusps In lateroinferior movement: larger posterior

cusp

IMPORTANCE OF BENNET MOVEMENT

Reproducing the cusp Its direction and timing influence the freedom

of movement to and from centric and eccentric Jaw position through corresponding sulci of antagonist

FISCHER ANGLE

THE ANGLE FORMED BETWEEN THE SAGITTAL PROTUSIVE CONDYLAR PATH AND SAGITTAL LATERAL CONDYLAR PATH : FISCHER ANGLE

Mean : 5 °

5 different patterns Unique curve type Concave curve type Straight type Convex curve Unique convex curve

type

BASED ON THE EXTEND OF MOVEMENT

Single-Plane Border MovementsThe mandibular movements are limited by ligaments, the articular surfaces of the TMJ, and the morphology and alignment of the teeth. The outer range of movement is

reproducible and called border movements.

SAGITTAL PLANE

Sagittal Plane Border Movement

Posterior open border Anterior open border Superior contact border Functional movements

Sagittal Plane Border Movement

POSTERIOR OPENING BORDER MOVEMENT

ANTERIOR OPENING BORDER MOVEMENT

SUPERIOR CONTACT BORDER MOVEMENTS

DETERMINANTS OF SUPERIOR CONTACT MOVEMENTS

THE AMOUNT OF VARIATION BETWEEN THE CR AND ICP

THE STEEPNESS OF THE CUSPAL INCLINES .

THE AMOUNT OF OVERJET AND OVERBITE IN ANTERIORS

LINGUAL MORPHOLOGY OF THE ANTERIOR TEETH

GENERAL INTERARCH RELATIONSHIP.

COMMON RELATONSHIP OF TEETH WHEN THE CONDYLES ARE IN CENTRIC RELATION

FORCE APPLIED TO THE TEETH WHEN CONDYLES ARE IN CENTRIC RELATION WILL CREATE A SUPEROANTERIOR SHIFT OF THE MANDIBLE TO THE INTERCUSPAL POSITION

WHILE THE MANDIBLE MOVES FORWARD, CONTACT OR THE INCISAL EDGES OF THE EDGES OF MANDIBULAR ANTERION TEETH WITH LINGUAL SURFACES OF THE MAXILLARY ANTERION TEETH CREATES AN INFERIOR MOVEMENT

HORIZONTAL MOVEMENT OF THE MANDIBLE WHILE THE INCISAL EDGES OF MAXILLARY AND MANDIBULAR TEETH PASS ACROSS EACH OTHER

CONTINUED FORWARD MOVEMENT OF THE MANDIBLE RESULTS IN A SUPERIOR MOVEMENT WHILE THE ANTERIOR TEETH PASS BEYOND THE END TO END POSITION RESULTING IN POSTERIOR TOOTH CONTACT

CONTINUED FORWARD MOVEMENT IS DETERMINED BY THE POSTERIOR TOOTH SURFACES UNTILL THE MAXIMUM PROTUSIVE MOVEMENT, AS ESTABLISHED BY THE LIGAMENT, IS REACHED. THIS MAXIMUM FORWARD POSITION JOINS THE MOST SUPERIOR POINT OF ANTERIOR BORDER MOVEMENTS.

THE MANDIBLE IN THE POSTERIOR POSITION IS LOCATED SOME 2-4 MM BELOW THE INTERCUSPAL POSITION

Functional Movements

Begin and end at ICP Postural position – 2-4 mm below the ICP; functionally ready

position maintained by the myotatic reflex . Clinical rest position – 8 mm inferior and 3 mm anterior to the ICP; M of M at their lowest level of activity Chewing stroke – begins at ICP, drops downward and slightly

forward, returns slightly posterior Postural Effects on Functional Movement Upright position – Postural position 2-4mm below ICP Extended upward – Tooth contact posterior to ICP • Alert feeding position

Tooth contact anterior to ICP

CLASS II MAXIMUM OPENING IS LESS DUE TO SMALLER SIZE OF THE

MANDIBLE.

PROTUSIVE MOVEMENT IS GREATER DUE TO AMOUNT OF HORIZONTAL AND VERTICAL OVERLAP.

ARC OF HINGE OPENING, INTEROCCLUSSAL CLEARANCE IS GREATER

CLASS III MAXIMUM OPENING IS

GREATER BECAUSE OF THE LENGTH OF MANDIBLE

PROTUSIVE MOVEMENT IS SMALLER

ARC OF HINGE OPENING IS GREATER BECAUSE OF THE JAW SIZE.

HORIZONTAL PLANE

Border Movement Horizontal Plane

Left lateral border Continued left lateral border

with protrusion Right lateral border Continued right lateral border

with protrusion Functional movements

Horizontal Plane Border Movement

Functional movements

LEFT LATERAL BORDER MOVEMENT

LEFT LATERAL BORDER MOVEMENT IN HORIZONTAL PLANE

CONTINUED LEFT LATERAL BORDER MOVEMENTS WITH PROTUSION IN THE HORIZONTAL PLANE

RIGHT LATERAL BORDER MOVEMENT IN THE HORIZONTAL PLANE

CONTINUED RIGHT LATERAL BORDER MOVEMENT WITH PROTUSION IN THE HORIZONTAL PLANE

CONTINUED RIGHT LATERAL BORDER MOVEMENT WITH PROTUSION IN THE HORIZONTAL PLANE

FUNCTIONAL RANGE WITH THE HORIZONTAL BORDER MOVEMENT

Functional Movements • Begin and end at the ICP • Mandible drops inferiorly to desired opening and

shifts up on the side of the bolus until ICP is reached

FRONTAL PLANE

Frontal (Vertical) Border and Functional Movement

BORDERS COME CLOSER AS THE MOUTH IS OPENED

Mandibular Lateral Translation

In visualizing this movement, one must remember that the condyle is essentially ovoid, not spherical, and that during lateral excursions, the irregularly shaped condyle rotates simultaneously about three axes. Moving the vertical axis of rotation may have a pronounced effect on the path traced by mandibular cusps against the maxillary teeth. Mandibular lateral translation can only be approximated or averaged on a semi-adjustable articulator.

LEFT LATERAL SUPERIOR BORDER MOVEMENTIN THE FRONTAL PLANE

Left Lateral Superior Border Movement • Primarily determined by morphology and occlusal relationship of

the teeth • Secondarily by the condyle-disc-fossa relationship

Left Lateral Opening Border Movements• Laterally convex path until maximum opening

Right Lateral Superior Border Movement• Mandible moves to the right in a inferiorly concave path

RIGHT LATERAL OPENING BORDER MOVEMNET

Frontal (Vertical) Border and Functional Movement

Mandible drops directly inferiorly until the desired opening is achieved. Then shifts to the side where the bolus is placed and rises up.

ENVELOPE OF MOTION

CLINICAL CONSIDERATIONS

Compensating curve are incorporated in denture to balance in lateral and protrusive movement

Accurate reproduction of hinge axis , centric relation is required to attain mandibular position with normal muscular activity in CD patients

Reference position and movements are important for functional analysis of the occlusion

In class 2:short cusps posterior)-due to lack of anterior guidance

Immediate denture: movement patterns are not changed as teeth are

restored immediately. So balance articulation is to be given

• Fixed partial denture:• Condylar guidance: shallow protrusive guidance-short cusps Steeper protrusive condylar guidance-longer cusps Anterior guidance Increased anterior guidance-longer cusps Decreased anterior guidance-longer cusps

FUNCTIONAL MOVEMENTS

CHEWING

While incising the food, adults open their mouth a comfortable distance and move the mandible forward until they incise, with the anterior teeth meeting approximately edge to edge .

The food bolus if then transported to the center of the mouth as the mandible returns to its starting position, with the incisal edges of the mandibular anterior teeth tracking along the lingual concavites of the maxillary anteriors.

The mouth then opens slightly, tongue pushes the food onto the occlusal table, and after moving sideways , the mandible closes into the food until the guiding teeth (typically canines ) contact.

The cycle is completed as the mandible returns to its starting position. This pattern repeats itself till the food bolus has been reduced to

particles that are small enough to be swallowed . The direction of mandibular path closure is influenced by The inclination of the occlusal plane with the teeth apart The occlusal guidance as the jaw approaches intercuspal position.

The chewing pattern in children

The chewing pattern in children is different from that in adults.

Until the age of about 10 children begin the chewing stroke with a lateral movement.

At the age of 10, they start to chew increasingly like adults, with a more vertical stroke.

PARAFUNCTIONAL MOVEMENTS

BRUXISM Sustained grinding, rubbing or

gnashing of teeth with greater than normal chewing force.

Is initiated at subconscious level

May be diurnal, nocturnal or both.

Nocturnal is more harmful because the patient is unaware of it while sleeping, therefore difficult to detect.

Etiology : still unclear relation to malocclusion neuromuscular disturbances response to emotional stress sleep disturbances combination of the above

stated factors.

As the degree of muscle activity necessary to avoid interferences increases, increase in muscle tone results, with subsequent pain in hyperactive musculature, which can lead to restricted movements.

Much of the force on their teeth may have a lateral component. Buccolingual forces in particular result in PDL widening. The fulcrum effect of rubbing on posterior interference will create

a protusive or laterotrusive movement, that can cause overloading of the anterior teeth, with resultant excessive anterior wear.

Pattern : Initially on the canines to the central and laterals, once vertical overlap diminishes, posterior wear facets are observed.

CLENCHING Forceful clamping together of the

jaws in a static relationship. The pressure thus created can be

maintained over a considerable time with short periods of relaxations in between.

Etiology : stress anger physical exertion intense concentration on a given

task. DOES NOT necessarily result in

damage because the concentration of pressure is directed more or less through the long axes of the posterior teeth without the involvement of detrimental lateral forces.

Clinical features: Abfraction, may result from sustained

clenching. damage to the periodontium damage to the TMJ elevators become overdeveloped progression of muscle splinting, myospasm,

myositis may occur.

BIBLIOGRAPHY MANAGEMENT OF TEMPOROMANDIBULAR DISORDERS AND

OCCLUSION : Jeffery P Okeson TEXTBOOK OF COMPLETE DENTURES : Charles M. Heartwell, Jr OCCLUSION ,PRINCIPLES & TREATMENT: JOSE DOS SANTOS, Jr CONTEMPORARY FIXED PROSTHODONTICS: Rosensteil Functional Occlusion : Dawson WHEELER'S DENTAL ANATOMY, PHYSIOLOGY AND OCCLUSION,

8th edition. Ash, Major M.; Nelson, Stanley. www.ncbi.nlm.nih.gov www.nature/bdj/journal Journal of orthodontics, 2005 Journal of oral rehab , 1997