Functional Occlusion Presented byDr. Ruchi Saxena Dept. of Orthodontics
Contents
Mechanics
Typ Types of functional occlusion occlusion
Criteria for optimal functional occlusion
Functional occlusion occlusion for th e Orthodontist
of Mandibular mov ement
Contents
Mechanics
Typ Types of functional occlusion occlusion
Criteria for optimal functional occlusion
Functional occlusion occlusion for th e Orthodontist
of Mandibular mov ement
Mechanics
of Mandibular
Movement
Complex series of rotational & translational activities
Combined and simultan eous activities of TMJ
2
types of movement :Rotational Translational
Rotation
Dorland¶s Medical dictionary defines rotation as ³ the process of turning around an axis: movement of body about its axis ´ -Rotational
movement
around a fi xed point in the condyle -Rotational
movement
occurs in 3 plan es of space
Horizontal
axis of rotation
Hinge
movement
Terminal hinge axis
Pur e rotation
Frontal (vertical) Axis of rotation
One condyle moves anteriorly Vertical axis of other condyle r emains in terminal hinge axis This type of isolated movement does not occur naturally
Sagittal
Axis of rotation
One condyle moves inf erior while other r emains in the terminal hinge position Ligaments of T MJ
pr event inf erior movement
Translation Movement
A movement in which every point of th e moving object has same velocity
Single
plane border movement
Border movements-when the mandible moves through the outer range of motion r eproducibl e limits r esults. Sagittal plan e border and functional movement Frontal plane border and functional movement Horizontal
movement
plane border and functional
Sagittal
plane border and functional movement
1.Post. Opening border
2.Ant.
3.Superior contact bord er
4.Functional
Opening border
Posterior opening border movement
2
stage hinging movement -rotational
movement of
the mandible with the condyles in the terminal hinge position -pur e
rotation occurs
till anterior teeth ar e 20-25
mm apart
2nd
stage
TMJ ligaments tightens anterior &inf erior 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 pr ecise delineation depends upon fiv e factors-
The amount of variation b etween CR & CO
Steepness
of cuspal inclines of posterior teeth
Amount of vertical and horizontal ov erlap of anterior teeth
The lingual morphology of ant erior teeth
The general inter arch r elationships of teeth
Common r elationship of th e teeth when condyles ar e in the centric r elation (CR)
Force applied to the teeth will cr eate 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 cr eates an inf erior movement
Horizontal
movement of the mandible while the incisal edges of maxillary and mandibular teeth pass across each others
Continued forward mov ement of the mandible r esults in a superior movement while the anterior teeth pass beyond the end-to-end position r esulting in posterior tooth contacts
Continued forward mov ement is determined by the posterior tooth surfaces untill the maximum protrusiv e movement is established by the ligaments
Functional movement
Fr ee movements
Postural position
Chewing stroke
Postural eff ect on functional movement
Horizontal
plane border &functional
movement
Goathic arch tracing
Rhomboidal shape pattern
Horizontal
components
1.Left lateral border movement
2.continu ed left
3.right lateral border
4.continu ed right lateral
lateral border with protrusion
border with protrusion
Left lateral border movement
Contraction of right lat pt erygoid
Relaxation of left lat pterygoid
Orbiting condyle- right side
Rotating condyle- left
Continued left lateral border movements with protrusion
Contraction of both l eft and right lat eral pterygoid Condyle moves anteriorly to the right
Right lateral border movements
Contraction of l eft lateral pterygoid while right side muscle r elaxes
Continued right lateral border movement with protrusion
Mandibular
border movements in the horizontal plane r ecorded at various d egr ees of opening. The border comes close together as the mouth is opened
Functional movements
Occurs near the ICP
Initially it begins at a distanc e from ICP
Frontal border &functional movement
Shield
shape pattern
1.Left lateral superior
2.Left
3.Right lateral superior
4.Right lateral opening
5.Functional
lateral opening
Left lateral superior
Determined by the morphology & int er arch r elationships of maxillary and mandibular t eeth Inf eriorly 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 thr ee dimensional envelope of motion can be produced that r epr esents the maximum range of movements of the mandible. Shape
diff ers from person to person
Functional occlusion is d efined as an arrangement of teeth which will provid e the highest efficiency during all excursive movements of the mandibl e which ar e 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 th e lingual inclines of maxillary anterior teeth while the posterior disocclud e. These ar e 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 stag es 1. Initial contact 2.
Beginning of ant erior discluding factor
3. End to end position
For proper disclusion ther e must be proper horizontal & vertical overlap ± fr ee mandibular movement Vertical overlap of the maxillary anterior teethshould be at least 1.5mm of interocclusal space
What
if ther e is too much of
1. horizontal ov erlap?? (class II div 1) 2.
Vertical overlap? (class II div
2
)
3. Or no overlap? (class III or op en bite )
Class II div 1 Patient has to r each out for ant t eeth to engage No
immediate disclusion
Horizontal
forc es 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 quit e small (1-2mm) This movement is r estricted by ligaments of TMJ
Lateral : It includes tooth contact that occurs on canin es and posterior teeth on the side which mandibl e moves.
The condyle on the side towards which movement occurs is r ef err ed as w orking side
The condyle on the other side is non w orking 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 because1.Restraining eff ects of tempromandibular ligament 2.Walls
of the glenoid fossa
3.Eccentric shape of the condyle
Bennette movement can be of two typesImmediate or early shift Gradual or progr essive shift
During lateral movements the functional occlusion can b e 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 th e posterior teeth by cuspid in lateral excursions
During lateral mandibular mov ement the upper and lower canines of working side contact, causing disclusion of all post erior teeth on working and balancing sid es. Hence the terms canine protected , canine guided occlusion, canine rise, canine lift.
Canine guided lateral movement of mandible
Lateral excursion may also b e guided by the central/ lateral incisors on th e working side acting in a group function with canin e. The canine must be the major discluding tooth.
Why
canine ??
Longest and largest root ther efor e the best crown root ratio Dense compact bone Fewer muscles ar e active when canine contacts during eccentric movement Lower muscle activity
less force
Concave palatal surface of upper caninesuitable for lateral gliding mov ement
Gr eater root surface ar ea providing gr eater 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 /r etroclined incisors
Class III or open bite guidance from posterior teeth on lateral excursion
Group functional occlusion Group function r ef ers to the distribution of lateral forces to the group of teeth rather than protecting those teeth from contact in function by assigning all th e forces to one particular tooth.
Group function
This is advantag eous if the PDL support of canine is compromised It is indicated wher ever the arch r elationship do esn¶t allow anterior disclusion
the 1st tooth contact is an eccentric position and on th e inclines of cusps of posterior teeth the force is torsional. Since
The force exerted has both vertical and horizontal compon ent
How
to r educe horizontal component?
Reduce the magnitud e of force striking the inclines -Simultaneously
surfaces
striking many working
Reduce the angle of inclines -Making
horizontal
vertical component mor e than
Similiarities
between group function and cuspid protected functional occlusion
Both provide multiple post contact with ICP located coincident with centric r elation position Absence of posterior contact on balancing side during lateral excursion
No
posterior contact during ant erior incision Anterior group functional guidanc e during protrusion with post disclusion (M c Adam 1974 JPD )
Mutually
protected occlusion
An occlusal sch eme in which the posterior teeth pr event excessive contact of ant erior teeth in maximum intercuspation and th e anterior teeth disengage the posterior teeth in all mandibular excursive movement C anine protected occlusion is a form of mutually protected articulation
Optimum functional occlusion
It describes conditions which app ears to be least pathogenic for the gr eatest 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 stabl e
Should
be able to accept the load applied across the joint by muscles The mandible should be able to move in any possible dir ection without teeth getting in its way.
The mandible should close into maximum intercuspation without deflecting the condyle from the ideal r elationship in th e fossae.
Centric
relation- defined by
³Gnathologists´ as that position of the condyle which is uppermost, midmost & rearmost in the fossa when the jaws ar e at closed position
Musculo
skeletally stable position
Okeson defined centric r elation when the condyles ar e located in their most superior anterior position in the articular fossa r esting against the posterior slope of articular eminence with the articular disc properly interposed
The most superoanterior position of th e condyle (solid line ) is MS the most stable position of the joint. However, if th e inner horizontal fibr es of the TM ligamnet allow for some posterior movement of the condyle, posterior force will displace the mandible from this to a mor e posterior, less stable position ( dotted line). The two positions ar e at the same superior level
Management
of T empromandibular Disorders and Occlusion JEFFERYP.OKESON
5th edition
The r etrodiscal tissue is vascularized and well supplied with sensory nerves
force pain and br eakdown
Post aspect of mandibular fossa is s een to be quite thin and appar ently not m eant for str ess bearing.
Positional stability of joint is dictat ed by the muscles that pull across the TMJ
Masseter -
superior &anterior
Medial
Temporalis- straight superior
pterygoid- superior & anterior
However
optimal joint r elationship is achieved only when the articular discs ar e 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 th e superior position defined by Daw son as CR
Optimal functional tooth contacts
Musculoskeletal
stable position of the joints can b e maintained only when it is in harmony with a stabl e occlusal condition
W hen
only right side occlusal contacts ar e pr esent, activity of th e elevator muscles tends to pivot the mandible using the tooth contacts as a fulcrum. Th e r esult is an incr ease in joint force to the left TMJ and a decr eased force to the right TMJ
Management
of Tempromandibular Disorders and Occlusion 5th edition JEFFERYP.OKESON
with bilateral occlusal contacts & incr ease in number of th e occluding teeth stability is achieved
Management
of Tempromandibular Disorders and Occlusion 5th edition JEFFERYP.OKESON
The optimum occlusal conditions during mandibular closur e would be provided by ev en
and simultan eous contact of all
possible teeth. This furnishes maximum stability for the mandible while minimizing the amount of force placed on each tooth during function.
Ther efor e the optimal functional occlusal developed to this point can b e described asS imultaneous 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 d entition ther e is a short path of mov ement between the r etruded contact position and int ercuspal in anterior - posterior dir ection
Hildebrand
(1931),
Heath
(1949), Posselt
(1952 ), Shefter&Mcfall (1984) have shown that a discr epancy of 0 .5-1.5 mm exists
between CR & CO
William
(1971), Aubr ey (1978), Park
(1978 ),Roth (1981) promotes the concept of an ideal tr eatment goal being coincidence of the CR and CO
Epidemiological
studies fail to find this type of occlusion in natural d entiton
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 (S olbergetal 1979: Ingerwall et al 1980 )
H ow ever
the evidence is inconclusive«..
CR does not exactly coincide with CO Ther e is no disadvantag e to the patient of having a CR that coincid es with CO Tr eatment need not be unduly lengthened to achieve this goal
Dir ection of force placed on teeth
Role of periodontal ligam ent Acts as natural shock absorber controlling force of occlusion Orientation of PDL fibr e helps in dissipation v ertically dir ected 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 r esultant forces ar e dir ected along the long axis of the teeth, the PDL is quite efficient in accepting the forces and br eakdown is less likely.
The process of dir ecting the occlusal forces along the long axis of tooth is call ed axial loading 2
methods of axial loading -
1. Development of tooth contacts on either cusp tips or on flat surfac es
Tripodization
Each
cusp contact an opposing fossa such that it produces thr ee contacts surrounding the actual cusp tip.
Amount of forc e placed on the teeth
The TMJ permits various excursive movements of the mandible that allow horizontal forc es to be applied on the teeth. Horizontal
forc es ar e not accepted well by supporting structur e so it is important to id entify 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 mor e force can be generated on the posterior teeth (A)than on th e anterior teeth (B)
Management
of Tempromandibular Disorders and Occlusion 5th edition JEFFERYP.OKESON
The posterior teeth function eff ectively in accepting forces during closur e of the mouth.
Anterior teeth ar e in proper position to acc ept the forces of eccentric mandibular mov ement
anine C anine
guided or group function??
miological Epidemiological
studies have attempted to discover which type of lateral occlusion scheme is found in untr eated natural dentition
Contradictory May r ef elct
results!!!
various methodologies «.
Besler
& Hanman (1985) concluded that canine protected occlusion don¶t significantly alt er muscle activity during mastication, but do significantly r educe muscle activity during para functional clenching.
Physiological studi es wer e designed
Williamson
and Lundquist 1983 examined EMG activity of th e temporalis and masseter muscles during lat excursion in individual with canin e 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 b e 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 sid e) Mediotrusive
contacts can be destructive to masticatory syst em
Functional occlusion for orthodontist
It is generally assumed that the ideal static
occlusal r elationship is compatibl e with an ideal functional occlusion but this is not necessarily so««
Ther e ar e various r easons for orthodontist to seek mor e knowledge in the ar ea of functional occlusion 1. The answer to the stability of the tr eated orthodontic cas e would at least partially r est in the functional dynamics dynamics of occlusion
orthodonticall y is of 2. The tr eatment r ender ed orthodontically benefit to the patient or at least no harm to him
3.To r efute some of the claims made by nonorthodontists, that a good functional occlusion can not b e obtained if bicuspids ar e r emoved for orthodontic purpos es
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 b e proper to begin with and should b e close to centric
Very time consuming Equilibration
should not b e performed untill growth has been completed
Stability
of the jaw is a pr e r equisite for a stable equilibration
Basic concepts of functional occlusion
Fr ee movementof the mandible
Mandibl e
O ne
should be able to close into maximum intercuspation must utilize a specific set of criteria for a functional occlusion goal throughout diagnosis, treatment &retention
Tr eatment objective
R oth
1981
Pleasing facial esthetics
Molar r elationship
and tooth alignm ent-
Angle¶s norms
Functional occlusion evaluated gnathologically
Stability
of post tr eatment tooth positions and alignment Comfort efficiency and long evity of the dentition, supporting structur es & TMJ
Evaluation
of occlusal disharmony
Occlusal interf er ences:
Centric
Excursive
Protrusive Lateral working Lateral non working
Centric Interf er ence Interf er ence between CR& CO Mandible
moves forwards, upwards and
laterally Dir ected by the sliding contacts of th e inclined planes of occlusal surfac es of the maxillary teeth hence termed centric slide
Protrusive interf er ences
It occurs during protrusiv e gliding movements of mandible Distal surface of maxillary & mesial surface of mandibular post t eeth Lingual incisal surfac e of maxillary and labial surface of mandibual teeth
cclusal C orrection: orrection: O cclusal Solnit&C urnutte urnutte
principles&practice
Working
interf er ences
The side towards which jaw mov es Occurs between the buccal cusp of maxillary and mandibular t eeth
Non
working interf er ences
It occurs on lingual cusps of ma xillary teeth and buccal cusp of mandibular t eeth
Sign
and symptoms from occlusal interf er ences
Occlusal wear
Excessive
TMJ sounds
Limitations of op ening of movement
Myofacial
Contractur e of mandibular musculatur e
tooth mobility
pain
Diagonosis and tr eatment planning
It is necessary to diagnos e a case from a mandibular position of c entric r elation, if we wish to tr eat to centric occlusion The neuromuscular positioning of th e mandible to accommodate to occlusal discr epancies will hide the true discr epancies
Records should b e taken in centric r elation to evaluate how much discr epancies lies in which planes of space The cephalometric tomograph of T MJ is a good indicator of stat e of bony elements of joints.
U se
splints before orthodontic treatment«
The purpose of r epositioning splint 1. To enable operator to find true centric which is stable and comfortabl e 2.
To test patients r esponse to change in
occlusion befor e embarking on compl ex occlusal therapy
The mandibular postural chang es during splint therapy due to1.Relaxation of muscles 2.Disrupt
muscle engrams and r educe
symptoms
The objective is toSeat
the condyles in the most superior position possibl e and to adjust the occlusal surface of the splint to achieve maximum intercuspation
Finishing to Gnathological principles
Gnathological obj ectivesStable centric r elation and CR and CO coinciding Simultan eous contact of c entric stops Dir ection of str ess should be dir ected along the long axis Mutually prot ective occlusal sch eme
Excursive
occlusive scheme
Gentle lateral and protrusive lift Necessary in terms of post tr eatment stability Excessive lateral str ess on cuspid lingual movement
lower ant crowding
An improper anterior guidanc e in protrusive will tend to enhance the chance of r elapse in maxillary teeth labially Very common in post tr eatment orthodontic cas es because of bracket placement the maxillary incisors
elongation
of
Insufficient torque of the maxillary incisors
too steep anterior lift insufficient glide
The Ideal and the possible
Ideally centric r elation and habitual c entric occlusion of the teeth should be coincidental Is
it so???
Roth 1981- ther e is some slight r epositioning 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 r eview J.R.
Clark & R D
Evans
What
can be really achieved«.
To tr eat the orthodontic cas e close enough to centric so that ther e isNo
discernible discr epancy between CR and CO and if equilibration is n ecessary the case can be equilibrated
Ideal tooth positioning
Andr ews once said ³we (orthodontist) tend to look at teeth collectively rather than individually´
SIX
keys to normal occlusion
Further modified by Roth for an id eal occlusion
j co 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 embrasur e of upper and lower lip
No
mor e than 1 mm of attach ed gingiva should be visible upon a full smil e
2-2.5
mm of overjet and overbite
A level or nearly level occlusal plan e at the end of the tr eatment
Divergence of occlusal plan e from angle of eminence
for excursive clearance
-Lower
incisors point to point contact with the roots in a same plane.
Lower cuspid crowns angulat ed mesially degr ee Incisal tip 1 mm high er than the incisal edges of lateral incisors
5
Exaggerated
mesial rotation on
extraction
cases
Lower bicuspids upright by 1 d egr ee distal rotation mor e in
extraction
cases
Lower molar should b e upright distally by 1 degr ee
Lower buccal segment should hav e torque closer to Andr ew¶s measur ement Upper
6 yr molar should hav e
-Distal
rotation
-Mesio
axial inclination
-Buccal
root torqu e
Upper
Upper
bicuspid should be uprighted to 0 degr ee, with no rotation, distal rotation in extraction cases cuspid
Contact point adjac ent to the contact points of bicuspids and lat eral incisors Mesial
crown tip of 11 -13 degr ees
Upper
lateral and central incisors should be almost equal in incisal edge length 9 degr ees and 5 degr ees mesio axial inclination Sufficient
torque
Ther e should be no spaces or rotations in the arch The arch form should b e modified catenary curve
Tr eatment priorities
Corr ection of crossbites
Reduction of jaw r elationship
Elimination
Establishment
Space
of crowding
of the space for sever ely malposed teeth consolidation of lower arch
Levelling of the Curve of Spee
Finishing of th e lower arch
Establishment
of the desir ed molar
r elationship
Consolidation of ma xillary space and r etraction or intrusion of th e maxillary anterior teeth
Artistic positioning and torqu e of maxillary anteriors Over corr ection 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 tr eatment
Bracket placement is of utmost importanc e in achieving a good occlusal int ercuspation Improperly placed bracket should be corr ected at earliest As Roth says ³ I t is foolhardy to think that one can achieve a consisitently good functional result by never reseating brackets or bands ´
Prior to over corr ection ± Analyze the tooth fit to see if the upper arch can contain lower arch and still provide an over bite Tip Torque Cuspid h eight
Tipped incisors occupy mor e space
Torqued incisors occupy th e arc of a bigger circle Cuspids that hav e their contact gingival to bicuspids and lat eral may take1/3rd less space
Rotation of the molar take up too much of space Insufficient buccal root torqu e of upper molar makes for balancing and c entric interf er ences Lack of width in the lower bicuspid ar ea can cr eate a centric slide
It is well to to r emember that the better the lower arch is tr eated 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 alv eolar growth- molar fulcrum 2
things can happ en
Appearance of open bite and tongue thrust swallow No
open bite but clicking of the TMJ
Open bite due to interf er ence
Clicking of TMJ/stiffness of mandibular musculatur e
Anchorage control of vertical dir ection is of utmost importanc e to pr event cr eating a molar fulcrum. TPA or occipital pull h ead gear can be useful
In cases with short ramus h eight or posterior facial height car e should be taken not to drive molars distally
Light flexible wir es such as nitinol or D -Rect braided wir e should be used No
attempts should be made to completely level the curve of spee
If long class II elastics ar e used ther e could be extrusion of molars tipping of occlusal plan e less clearance of posterior teeth on movement of mandible
Short
class II elastic extrude the lower bicuspid thus levelling curve of spee,
Overcorr ection of the A-P r elation
It is done with headgear and short class II elastics Overcorr ection is held upto 3 months The wir es can be changed to braided r ectangular wir es as needed to seat the occlusion
While
Next
the occlusion is being brought back from over corr ection, it is necessary to start checking to see if mandible is in centric the patient is asked to execute various mandibulal excursions The glide should be smooth and slow if cuspid guidance is corr ect and ther e ar e no interf er ences
Finishing in centric r elation
Corr ect A-P jaw r elationship( ov er corr ect then hold, then settle back) Eliminat e
molar fulcrum
Coordinate arch width and arch form with mandibl e in centric r elation Watch
cuspids height and midlin e
Level curve of spee
Check for centric deflection
Marginal
rotations
ridg e heights
After centric is obtained
Check tooth detailing by having pati ent to go through t est 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, post erior clearance,cuspid guidanc e,and balancing interf er ences.
At th e end of applianc e therapy the occlusion should r esemble a bilateral balanced occlusal scheme during the excursions The anterior guidance should not b e adequate
One must plan for this occurr ence by keeping the anterior guidanc e a little shallow at the end of mechanotherapy.
Retention phase
Acc to Daw son, failur e to properly establish the corr ect guidance is a major cause of post tr eatment instability As long as th e ant guidance r emains intact capability of discluding th e post teeth in eccentric jaw position, th e protection of posterior teeth is assur ed
For this routine bonding of maxillary ant teeth with lingual r etainer is advised A functional rationale for bonded retainers: Angle orthodontics 1993
Bibliography Occlusion: principles &concepts 2nd Edition Jose dos Santos Evaluation, Diagnosis &tr eatment of Occlusion problemsDawson Occlusal corr ection : Principles &Practice Solnit & Curnutte Occlusion: 3rd edition Ramfjord& Ash A colour Atlas of occlusion &malocclusion Howatt, Capp, Barrett Functional occlusion for orthodontist- JCO 1981 Ronald.H.Roth Management of tempromandibular disord ers &occlusion 5th edition Jeffery P. Okeson
