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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