Functional Occlusion

Functional Occlusion

Presented by-Dr. Ruchi SaxenaDept. of Orthodontics

Contents

Mechanics of Mandibular movement Types of functional occlusion Criteria for optimal functional occlusion Functional occlusion for the Orthodontist

Mechanics of Mandibular Movement

Complex series of rotational & translational activities

Combined and simultaneous activities of TMJ 2 types of movement :Rotational

Translational

Rotation

Dorland’s Medical dictionary defines rotation as “ the process of turning around an axis: movement of body about its axis”

-Rotational movement

around a fixed point

in the condyle

-Rotational movement

occurs in 3 planes of space

Horizontal axis of rotation

Hinge movement Terminal hinge axis Pure rotation

Frontal (vertical) Axis of rotation

One condyle moves anteriorly Vertical axis of other condyle remains in

terminal hinge axis This type of isolated

movement does not occur

naturally

Sagittal Axis of rotation

One condyle moves inferior while other remains in the terminal hinge position

Ligaments of TMJ

prevent inferior movement

Translation Movement

A movement in which every point of the moving object has same velocity

Single plane border movement

Border movements-when the mandible moves through the outer range of motion reproducible limits results.

Sagittal plane border and functional movement

Frontal plane border and functional movement

Horizontal plane border and functional movement

Sagittal plane border and functional movement

1.Post. Opening border 2.Ant. Opening border 3.Superior contact border 4.Functional

Posterior opening border movement 2 stage hinging movement

-rotational movement of

the mandible with the

condyles in the

terminal hinge position

-pure rotation occurs

till anterior teeth are

20-25 mm apart

2nd stage

TMJ ligaments tightens

anterior &inferior movement

of condyle

shift in the axis of rotation

2nd stage Max opening is in the range of 40-60 mm

Anterior opening border movement

Contraction of lateral pterygoid Posterior movement of condyle

Superior contact border movements

Its precise delineation depends upon five factors-

The amount of variation between CR & CO Steepness of cuspal inclines of posterior teeth

Amount of vertical and horizontal overlap of anterior teeth

The lingual morphology of anterior teeth

The general inter arch relationships of teeth

Common relationship of the teeth when condyles are in the centric relation (CR)

Force applied to the teeth will create a superioanterior shift of the mandible to ICP

While the mandible moves forward, contact of the incisal edges of the mandibular anterior teeth with the lingual surfaces of the maxillary anterior teeth creates an inferior movement

Horizontal movement of the mandible while the incisal edges of maxillary and mandibular teeth pass across each others

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 contacts

Continued forward movement is determined by the posterior tooth surfaces untill the maximum protrusive movement is established by the ligaments

Functional movement

Free movements Chewing stroke Postural position

Postural effect on functional movement

Horizontal plane border &functional movement Goathic arch tracing Rhomboidal shape pattern

Horizontal components

1.Left lateral border movement 2.continued left lateral border with protrusion 3.right lateral border 4.continued right lateral

border with protrusion

Left lateral border movement

Contraction of right lat pterygoid Relaxation of left lat pterygoid Orbiting condyle- right side Rotating condyle- left

Continued left lateral border movements with protrusion Contraction of both left and right lateral pterygoid Condyle moves anteriorly to the right

Right lateral border movements

Contraction of left lateral pterygoid while right side muscle relaxes

Continued right lateral border movement with protrusion

Mandibular border movements in the horizontal plane recorded at various degrees of opening. The border comes close together as the mouth is opened

Functional movements

Occurs near the ICP Initially it begins at a distance from ICP

Frontal border &functional movement Shield shape pattern 1.Left lateral superior 2.Left lateral opening 3.Right lateral superior 4.Right lateral opening 5.Functional

Left lateral superior

Determined by the morphology & inter arch relationships of maxillary and mandibular teeth

Inferiorly concave

path is generated

Left lateral opening border movements An opening movement of the mandible

produces a laterally convex path

Right lateral superior border movements

Right lateral opening border movement

Functional movement

Begins and ends at ICP

Envelope of motion

By combining border movements in all the planes, a three dimensional envelope of motion can be produced that represents the maximum range of movements of the mandible.

Shape differs from person to person

Functional occlusion is defined as an arrangement of teeth which will provide the highest efficiency during all excursive movements of the mandible which are necessary during function

Types of functional occlusion

Lateral

Protrusive

Retrusive

Protrusive: It includes the eccentric contacts that occur when the mandible moves forward. Ideally six mandibular anterior teeth contact along the lingual inclines of maxillary anterior teeth while the posterior disocclude. These are called as a guiding inclines of the anterior teeth

Protrusive movement of the mandible

Disclusion of the posterior teeth must be immediate

It occurs in 3 stages 1. Initial contact

2. Beginning of anterior discluding factor

3. End to end position

For proper disclusion there must be proper horizontal & vertical overlap – free mandibular movement

Vertical overlap of the maxillary anterior teeth- should be at least 1.5mm of interocclusal space

What if there is too much of

1. horizontal overlap?? (class II div 1)

2. Vertical overlap?

(class II div 2 )

3. Or no overlap? (class III or open bite )

Class II div 1

Patient has to reach out for ant teeth to engage

No immediate disclusion

Horizontal forces on posterior teeth

Class II div 2

Unwanted occlusal forces on the anterior teeth during disclusion

Class III or open bite

No anterior disclusion

Retrusive movements

It occurs when the mandible moves posteriorly from ICP It is quite small (1-2mm) This movement is restricted by ligaments of TMJ

Lateral : It includes tooth contact that occurs on canines and posterior teeth on the side which mandible moves.

The condyle on the side towards which movement occurs is referred as working side

The condyle on the other side is non working or balancing side

During lateral movement the working side

condyle may rotate, rotate or move

laterally and also upward &downward.

This lateral movement is called Bennette movement

This movement necessary to permit rotation of the condyles because-

1.Restraining effects of tempromandibular ligament

2.Walls of the glenoid fossa

3.Eccentric shape of the condyle

Bennette movement can be of two types- Immediate or early shift Gradual or progressive shift

During lateral movements the functional occlusion can be of two types:

Canine guided Group function

Canine guided or cuspid protected occlusion This theory was put forward by Nagao 1919 Shaw 1924 D’Amico 1958

It includes disclusion of all the posterior teeth by cuspid in lateral excursions

During lateral mandibular movement the upper and lower canines of working side contact, causing disclusion of all posterior teeth on working and balancing sides. Hence the terms canine protected , canine guided occlusion, canine rise, canine lift.

Canine guided lateral movement of mandible

Lateral excursion may also be guided by the central/ lateral incisors on the working side acting in a group function with canine.

The canine must be the major discluding tooth.

Why canine ??

Longest and largest root therefore the best crown root ratio

Dense compact bone Fewer muscles are active when canine

contacts during eccentric movement Lower muscle activity less force

Concave palatal surface of upper canine-

suitable for lateral gliding movement

Greater root surface area providing greater proprioception ????

Class II div 1

Canine to lower

Incisors contact \

Class II div 2

Lateral excursion may be guided by upper canines and lower incisors /retroclined incisors

Class III or open bite

guidance from posterior teeth on lateral excursion

Group functional occlusion

Group function refers to the distribution of lateral forces to the group of teeth rather than protecting those teeth from contact in function by assigning all the forces to one particular tooth.

Group function

This is advantageous if the PDL support of canine is compromised

It is indicated wherever the arch relationship doesn’t allow anterior disclusion

Since the 1st tooth contact is an eccentric position and on the inclines of cusps of posterior teeth the force is torsional.

The force exerted has both vertical and horizontal component

How to reduce horizontal component? Reduce the magnitude of force striking the

inclines

-Simultaneously striking many working surfaces

Reduce the angle of inclines

-Making vertical component more than

horizontal

Similiarities between group function and cuspid protected functional occlusion Both provide multiple post contact with

ICP located coincident with centric relation position

Absence of posterior contact on balancing side during lateral excursion

No posterior contact during anterior incision

Anterior group functional guidance during protrusion with post disclusion

(Mc Adam 1974 JPD)

Mutually protected occlusion

An occlusal scheme in which the posterior teeth prevent excessive contact of anterior teeth in maximum intercuspation and the anterior teeth disengage the posterior teeth in all mandibular excursive movement

Canine protected occlusion is a form of mutually protected articulation

Optimum functional occlusion

It describes conditions which appears to be least pathogenic for the greatest number of patient over a longest time

Criteria for the optimal functional occlusion

Optimal orthopedically stable joint position

Optimal functional tooth contact

Optimal orthopedically stable joint position Patient is comfortable Position of joint is stable Should be able to accept the load applied across

the joint by muscles The mandible should be able to move in any

possible direction without teeth getting in its way.

The mandible should close into maximum intercuspation without deflecting the condyle from the ideal relationship in the fossae.

Centric relation- defined by

“Gnathologists” as that position of the

condyle which is uppermost, midmost &

rearmost in the fossa when the jaws are

at closed position

Musculo skeletally stable position

Okeson defined centric relation when the condyles are located in their most superior anterior position in the articular fossa resting against the posterior slope of articular eminence with the articular disc properly interposed

The most superoanterior position of the condyle (solid line ) is MS the most stable position of the joint. However, if the inner horizontal fibres of the TM ligamnet allow for some posterior movement of the condyle, posterior force will displace the mandible from this to a more posterior, less stable position ( dotted line). The two positions are at the same superior level

Management of Tempromandibular Disorders and Occlusion 5th edition JEFFERYP.OKESON

The retrodiscal tissue is vascularized and well supplied with sensory nerves

force pain and breakdown

Post aspect of mandibular fossa is seen to be quite thin and apparently not meant for stress bearing.

Positional stability of joint is dictated by the muscles that pull across the TMJ

Masseter- superior &anterior Medial pterygoid- superior & anterior Temporalis- straight superior

However optimal joint relationship is achieved only when the articular discs are properly interposed between condyles and the articular fossa

The purpose of the disc is to seprate, protect, and stabilzes the condyle in the mandibular fossa during functional movements,

This MS position is similar to the superior

position defined by Dawson as CR

Optimal functional tooth contacts

Musculoskeletal stable position of the joints can be maintained only when it is in harmony with a stable occlusal condition

When only right side occlusal contacts are present, activity of the elevator muscles tends to pivot the mandible using the tooth contacts as a fulcrum. The result is an increase in joint force to the left TMJ and a decreased force to the right TMJ

Management of Tempromandibular Disorders and Occlusion 5th edition JEFFERYP.OKESON

with bilateral occlusal contacts & increase in number of the occluding teeth stability is achieved

Management of Tempromandibular Disorders and Occlusion 5th edition JEFFERYP.OKESON

The optimum occlusal conditions during

mandibular closure would be provided by

even and simultaneous contact of all

possible teeth. This furnishes maximum

stability for the mandible while minimizing

the amount of force placed on each tooth

during function.

Therefore the optimal functional occlusal developed to this point can be described as-

Simultaneous contact of all the possible teeth when the mandibular condyles are in their most superioanterior positions, resting against the posterior slopes of the articular eminence with the disc properly interposed.

Musculoskeletal stable position (CR)

coincides with the maximum intercuspal

position of the teeth (CO)

It is generally accepted that in most

individuals with a natural dentition there is

a short path of movement between the

retruded contact position and intercuspal

in anterior- posterior direction

Hildebrand (1931), Heath (1949), Posselt

(1952 ), Shefter&Mcfall (1984) have

shown that a discrepancy of 0 .5-1.5 mm

exists between CR & CO

William (1971), Aubrey (1978), Park

(1978 ),Roth (1981) promotes the concept

of an ideal treatment goal being

coincidence of the CR and CO

Epidemiological studies fail to find this type of occlusion in natural dentiton

Why this should be then the goal following orhtodontic treatment….???

Argument put forward is non

coincidence of the two position (CR&CO)

is associated with TMD

(Solbergetal 1979: Ingerwall et al 1980)

However the evidence is inconclusive…..

CR does not exactly coincide with CO There is no disadvantage to the patient of

having a CR that coincides with CO Treatment need not be unduly lengthened

to achieve this goal

Direction of force placed on teeth

Role of periodontal ligament Acts as natural shock absorber controlling

force of occlusion Orientation of PDL fibre helps in

dissipation vertically directed force on the long axis

Management of Tempromandibular Disorders and Occlusion 5th edition JEFFERYP.OKESON

To summarize, if a tooth is contacted in such a way that the resultant forces are directed along the long axis of the teeth, the PDL is quite efficient in accepting the forces and breakdown is less likely.

The process of directing the occlusal forces along the long axis of tooth is called axial loading

2 methods of axial loading- 1. Development of tooth contacts on either

cusp tips or on flat surfaces

Tripodization Each cusp contact an opposing fossa such

that it produces three contacts surrounding the actual cusp tip.

Amount of force placed on the teeth

The TMJ permits various excursive movements of the mandible that allow horizontal forces to be applied on the teeth.

Horizontal forces are not accepted well by supporting structure so it is important to identify which teeth can best accept these horizontal forces.

The amount of force that can be generated between the teeth depends on the distance from the TMJ and the muscle force vectors. Much more force can be generated on the posterior teeth (A)than on the anterior teeth (B)

Management of Tempromandibular Disorders and Occlusion 5th edition JEFFERYP.OKESON

The posterior teeth function effectively in accepting forces during closure of the mouth.

Anterior teeth are in proper position to accept the forces of eccentric mandibular movement

Canine guided or group function??

Epidemiological studies have attempted to discover which type of lateral occlusion scheme is found in untreated natural dentition

Contradictory results!!!

May refelct various methodologies ….

Besler & Hanman (1985) concluded that canine protected occlusion don’t significantly alter muscle activity during mastication, but do significantly reduce muscle activity during para functional clenching.

Physiological studies were designed Williamson and Lundquist 1983

examined EMG activity of the temporalis and masseter muscles during lat excursion in individual with canine guidance and group function– less activity in individual with canine guidance

The evidence in favour of one type of occlusal scheme over another is scarce….

Mediotrusive contacts should be avoided in developing an optimal functional occlusion

The laterotrusive contacts need to provide adequate guidance to disocclude the teeth on the opposite side of the arch (mediotrusive or non working side)

Mediotrusive contacts can be destructive to masticatory system

Functional occlusion for orthodontist It is generally assumed that the ideal static

occlusal relationship is compatible with an

ideal functional occlusion but this is not

necessarily so……

There are various reasons for orthodontist to seek more knowledge in the area of functional occlusion-

1. The answer to the stability of the treated orthodontic case would at least partially rest in the functional dynamics of occlusion

2. The treatment rendered orthodontically is of benefit to the patient or at least no harm to him

3.To refute some of the claims made by non- orthodontists, that a good functional occlusion can not be obtained if bicuspids are removed for orthodontic purposes

Role of equilibration

Unrealistic!!!

Don’t grinde your teeth that’s my job!!!

For a case to be equilibrate to a stable centric most tooth position should be proper to begin with and should be close to centric

Very time consuming

Equilibration should not be performed untill growth has been completed

Stability of the jaw is a pre requisite for a stable equilibration

Basic concepts of functional occlusion Free movementof the mandible Mandible should be able to close into

maximum intercuspation One must utilize a specific set of

criteria for a functional occlusion goal throughout diagnosis, treatment &retention

Treatment objective

Roth 1981 Pleasing facial esthetics Molar relationship and tooth alignment-

Angle’s norms Functional occlusion evaluated

gnathologically

Stability of post treatment tooth positions and alignment

Comfort efficiency and longevity of the dentition, supporting structures & TMJ

Evaluation of occlusal disharmony

Occlusal interferences: Centric Excursive Protrusive

Lateral working

Lateral non working

Centric Interference

Interference between CR& CO

Mandible moves forwards, upwards and laterally

Directed by the sliding contacts of the inclined planes of occlusal surfaces of the maxillary teeth hence termed centric slide

Protrusive interferences

It occurs during protrusive gliding movements of mandible

Distal surface of maxillary & mesial surface of mandibular post teeth

Lingual incisal surface of maxillary and labial surface of mandibual teeth

Occlusal Correction: principles&practice Solnit&Curnutte

Working interferences The side towards which jaw moves Occurs between the buccal cusp of

maxillary and mandibular teeth

Non working interferences

It occurs on lingual cusps of maxillary teeth and buccal cusp of mandibular teeth

Sign and symptoms from occlusal interferences

Occlusal wear Excessive tooth mobility TMJ sounds Limitations of opening of movement Myofacial pain Contracture of mandibular musculature

Diagonosis and treatment planning

It is necessary to diagnose a case from a mandibular position of centric relation, if we wish to treat to centric occlusion

The neuromuscular positioning of the mandible to accommodate to occlusal discrepancies will hide the true discrepancies

Records should be taken in centric relation to evaluate how much discrepancies lies in which planes of space

The cephalometric tomograph of TMJ is a good indicator of state of bony elements of joints.

Use splints before orthodontic treatment…

The purpose of repositioning splint-

1. To enable operator to find true centric

which is stable and comfortable

2. To test patients response to change in

occlusion before embarking on complex

occlusal therapy

The mandibular postural changes during splint therapy due to-

1.Relaxation of muscles

2.Disrupt muscle engrams and reduce

symptoms

The objective is to- Seat the condyles in the most superior

position possible and to adjust the occlusal surface of the splint to achieve maximum intercuspation

Finishing to Gnathological principles Gnathological objectives- Stable centric relation and CR and CO

coinciding Simultaneous contact of centric stops Direction of stress should be directed

along the long axis Mutually protective occlusal scheme

Excursive occlusive scheme

Gentle lateral and protrusive lift Necessary in terms of post treatment stability Excessive lateral stress on cuspid lingual movement lower ant crowding

An improper anterior guidance in protrusive will tend to enhance the chance of relapse in maxillary teeth labially

Very common in post treatment orthodontic cases because of

bracket placement elongation of the maxillary incisors

Insufficient torque of the maxillary incisors

too steep anterior lift

insufficient glide

The Ideal and the possible

Ideally centric relation and habitual centric occlusion of the teeth should be coincidental

Is it so???

Roth 1981- there is some slight repositioning of the mandible in even the best of the cases

Shefter& Mcfall 1984 Agergberg & Sandstrom 1988

Discrepancy of 0.5-1.5 mm exists

Journal of Orthodontics: March 2000

Functional Occlusion: A review

J.R. Clark & R D Evans

What can be really achieved….

To treat the orthodontic case close enough

to centric so that there is-

No discernible discrepancy between CR and CO and if equilibration is necessary the case can be equilibrated

Ideal tooth positioning

Andrews once said “we (orthodontist) tend to look at teeth collectively rather than individually”

SIX keys to normal occlusion Further modified by Roth for an ideal occlusion

jco April1981: functional occlusion for orthodontist

Ronald.R. Roth

Lower incisors at the cephalometric goal of +1to A- pog line

Tip of the upper incisors 2-2.5mm below the lip embrasure of upper and lower lip

No more than 1 mm of attached gingiva should be visible upon a full smile

2-2.5 mm of overjet and overbite

A level or nearly level occlusal plane at the end of the treatment

Divergence of occlusal plane from angle of

eminence for excursive clearance

-Lower incisors point to point contact with the roots in a same plane.

Lower cuspid crowns angulated mesially 5 degree

Incisal tip 1 mm higher than the incisal edges of lateral incisors

Exaggerated mesial rotation on extraction cases

Lower bicuspids upright by 1 degree distal rotation more in extraction cases Lower molar should be upright distally by 1

degree

Lower buccal segment should have torque closer to Andrew’s measurement

Upper 6 yr molar should have

-Distal rotation

-Mesio axial inclination

-Buccal root torque

Upper bicuspid should be uprighted to 0 degree, with no rotation, distal rotation in extraction cases

Upper cuspid Contact point adjacent to the contact

points of bicuspids and lateral incisors Mesial crown tip of 11-13 degrees

Upper lateral and central incisors should be almost equal in incisal edge length

9 degrees and 5 degrees mesio axial inclination

Sufficient torque

There should be no spaces or rotations in the arch

The arch form should be modified catenary curve

Treatment priorities

Correction of crossbites Reduction of jaw relationship Elimination of crowding Establishment of the space for severely

malposed teeth Space consolidation of lower arch

Levelling of the Curve of Spee Finishing of the lower arch Establishment of the desired molar

relationship Consolidation of maxillary space and

retraction or intrusion of the maxillary anterior teeth

Artistic positioning and torque of maxillary anteriors

Over correction of buccal segment, curve of spee, rotations and root positions at extraction sites

Final detailing of tooth position

It is of utmost importance that lower arch must be finished and in the correct position to act as a template to receive the upper teeth

Detailing of tooth position in the treatment Bracket placement is of utmost importance in

achieving a good occlusal intercuspation Improperly placed bracket should be corrected

at earliest As Roth says “It is foolhardy to think that one

can achieve a consisitently good functional result by never reseating brackets or bands”

Prior to over correction – Analyze the tooth fit to see if the upper

arch can contain lower arch and still provide an over bite-

Tip Torque Cuspid height

Tipped incisors occupy more space

Torqued incisors occupy the arc of a bigger circle

Cuspids that have their contact gingival to bicuspids and lateral may take1/3rd less space

Rotation of the molar take up too much of space

Insufficient buccal root torque of upper molar makes for balancing and centric interferences

Lack of width in the lower bicuspid area can create a centric slide

It is well to to remember that the better the lower arch is treated the better the case will look after settling

Control of the vertical dimension and the molar fulcrum Avoid extrusion of the posterior teeth and

excess vertical alveolar growth- molar fulcrum

2 things can happen Appearance of open bite and tongue

thrust swallow No open bite but clicking of the TMJ

Open bite due to interference

Clicking of TMJ/stiffness

of mandibular musculature

Anchorage control of vertical direction is of utmost importance to prevent creating a molar fulcrum.

TPA or occipital pull head gear can be useful

In cases with short ramus height or posterior facial height care should be taken not to drive molars distally

Light flexible wires such as nitinol or D-Rect braided wire should be used

No attempts should be made to completely level the curve of spee

If long class II elastics are used there could be extrusion of molars tipping of occlusal plane less clearance of posterior teeth on movement of mandible

Short class II elastic extrude the lower bicuspid thus levelling curve of spee,

Overcorrection of the A-P relation

It is done with headgear and short class II elastics

Overcorrection is held upto 3 months

The wires can be changed to braided rectangular wires as needed to seat the occlusion

While the occlusion is being brought back from over correction, it is necessary to start checking to see if mandible is in centric

Next the patient is asked to execute various mandibulal excursions

The glide should be smooth and slow if cuspid guidance is correct and there are no interferences

Finishing in centric relation

Correct A-P jaw relationship( over correct then hold, then settle back)

Eliminate molar fulcrum Coordinate arch width and arch form with

mandible in centric relation Watch cuspids height and midline

Level curve of spee Check for centric deflection Marginal ridge heights rotations

After centric is obtained

Check tooth detailing by having patient to go through test excursions

Torque of upper incisors Tip of incisors and cuspids Overbite and overjet Flatness of curve of spee

Second molar position Look for anterior group function, posterior

clearance,cuspid guidance,and balancing interferences.

At the end of appliance therapy the occlusion should resemble a bilateral balanced occlusal scheme during the excursions

The anterior guidance should not be adequate

One must plan for this occurrence by keeping the anterior guidance a little shallow at the end of mechanotherapy.

Retention phase

Acc to Dawson, failure to properly establish the correct guidance is a major cause of post treatment instability

As long as the ant guidance remains intact capability of discluding the post teeth in eccentric jaw position, the protection of posterior teeth is assured

For this routine bonding of maxillary ant teeth with lingual retainer is advised

A functional rationale for bonded retainers: Angle orthodontics 1993

Bibliography

Occlusion: principles &concepts 2nd Edition Jose dos SantosEvaluation, Diagnosis &treatment of Occlusion problems- DawsonOcclusal correction : Principles &Practice Solnit & CurnutteOcclusion: 3rd edition Ramfjord& AshA colour Atlas of occlusion &malocclusion Howatt, Capp, BarrettFunctional occlusion for orthodontist- JCO 1981 Ronald.H.RothManagement of tempromandibular disorders &occlusion 5Management of tempromandibular disorders &occlusion 5 thth edition edition Jeffery P. OkesonJeffery P. Okeson