Tmj instrumentation

TMJTMJ
INSTRUMENTATIONINSTRUMENTATION
www.indiandentalacademy.comwww.indiandentalacademy.com

 1. INTRODUCTION1. INTRODUCTION
 2.NEED FOR RECORDING CR-CO DISCREPANCY2.NEED FOR RECORDING CR-CO DISCREPANCY
 1. CR DEFINITION1. CR DEFINITION
 2. CO DEFINITION2. CO DEFINITION
 3. CRITERIA FOR OPTIMAL FUNCTIONAL OCCLUSION3. CRITERIA FOR OPTIMAL FUNCTIONAL OCCLUSION
 4. SIGNS & SYMPTOMS OF CR-CO DISCREPANCY4. SIGNS & SYMPTOMS OF CR-CO DISCREPANCY
 5. MOUNTED VS HANDHELD CASTS5. MOUNTED VS HANDHELD CASTS
 3.METHODS OF RECORDING MM RELATIONS3.METHODS OF RECORDING MM RELATIONS
 4.RECORDING CONDYLAR POSITION4.RECORDING CONDYLAR POSITION
 a. FACEBOWa. FACEBOW
 b. ARTICULATORSb. ARTICULATORS
 c. MPIc. MPI
 d. ELECTRONIC MPId. ELECTRONIC MPI
 d. AXIOGRAPHYd. AXIOGRAPHY
 e. COMPUTERISED AXIOGRAPHYe. COMPUTERISED AXIOGRAPHY

INTRODUCTIONINTRODUCTION
 SYNOVIAL JOINTSYNOVIAL JOINT

MOVEMENTSMOVEMENTS can becan be
1. In upper joint space - hinge1. In upper joint space - hinge
2. In lower joint space – hinge + gliding2. In lower joint space – hinge + gliding
 Goals of orthodontic treatment -Goals of orthodontic treatment -
harmony between occlusal function andharmony between occlusal function and
TMJ.TMJ.
 Occlusion and its role on TMJ health –Occlusion and its role on TMJ health –
DEBATABLEDEBATABLE
 Ideal occlusal relationship shouldIdeal occlusal relationship should
coincide with ideal condyle-fossacoincide with ideal condyle-fossawww.indiandentalacademy.comwww.indiandentalacademy.com


RETRUDED AXIS POSITIONRETRUDED AXIS POSITION ––
 condyles articulate with the thinnest avascularcondyles articulate with the thinnest avascular
portion of their respective disksportion of their respective disks
 anterior-superior positionanterior-superior position
 discernible when the mandible is directeddiscernible when the mandible is directed
superiorly and anteriorly and restricted to a purelysuperiorly and anteriorly and restricted to a purely
rotary movement about a transverse horizontalrotary movement about a transverse horizontal
axis.axis.
 CENTRIC OCCLUSIONCENTRIC OCCLUSION
 The occlusion of opposing teeth when theThe occlusion of opposing teeth when the
mandible is in centric relation.mandible is in centric relation.
 This may or may not coincide with the maximumThis may or may not coincide with the maximum
intercuspation position.intercuspation position.www.indiandentalacademy.comwww.indiandentalacademy.com

• RETRUDED CONTACT POSITIONRETRUDED CONTACT POSITION -- occlusalocclusal
position when the first tooth contact occurs on theposition when the first tooth contact occurs on the
path of closure in the retruded axis position.path of closure in the retruded axis position.
• BENNETT ANGLEBENNETT ANGLE –– angle at which the orbitingangle at which the orbiting
condyle moves inward during laterotrusivecondyle moves inward during laterotrusive
movement and is measured in relation to themovement and is measured in relation to the
horizontal plane.horizontal plane.
• OCCLUSAL INTERFERENCEOCCLUSAL INTERFERENCE –– It is any toothIt is any tooth
contact that inhibits the remaining occludingcontact that inhibits the remaining occluding
surfaces from achieving stable and harmonioussurfaces from achieving stable and harmonious
contacts.contacts.

OPTIMAL FUNCTIONAL OCCLUSIONOPTIMAL FUNCTIONAL OCCLUSION
1.1. Musculoskeletally stable position.Musculoskeletally stable position.
2.2. Ideal condyle-fossa- disc relationship.Ideal condyle-fossa- disc relationship.
3.3. Bilateral occlusal contacts in RCP.Bilateral occlusal contacts in RCP.
4.4. RCP =ICP or a slide of < than 1 mmRCP =ICP or a slide of < than 1 mm
5.5. Working side contact during laterotrusion.Working side contact during laterotrusion.
6.6. No contact on balancing side duringNo contact on balancing side during
laterotrusion.laterotrusion.
7.7. Full extent of jaw movement has to be recorded.Full extent of jaw movement has to be recorded.
8.8. check the end-of-therapy occlusion usingcheck the end-of-therapy occlusion using
mounted models.mounted models.

NORMAL CONDYLE-DISC- FOSSANORMAL CONDYLE-DISC- FOSSA
RELATIONSHIPRELATIONSHIP
ROTHROTH-- acceptable difference between CR andacceptable difference between CR and
CO -1.00 mm AP, 1.00 mm in vertical planeCO -1.00 mm AP, 1.00 mm in vertical plane
and 0.5 mm in transverse planeand 0.5 mm in transverse plane..www.indiandentalacademy.comwww.indiandentalacademy.com

SIGNS OF CR-CO DISCREPANCYSIGNS OF CR-CO DISCREPANCY
 Occlusal wear.Occlusal wear.
 Excessive tooth mobility.Excessive tooth mobility.
 Temporomandibular joint sounds.Temporomandibular joint sounds.
 Limitation of opening or movement.Limitation of opening or movement.
 Myofascial pain.Myofascial pain.
 Contracture of mandibular musculature,Contracture of mandibular musculature,
making manipulation difficult or impossible.making manipulation difficult or impossible.
 Some types of tongue-thrust swallow.Some types of tongue-thrust swallow.

MOUNTED VS HANDHELD CASTSMOUNTED VS HANDHELD CASTS
 CLINICALCLINICAL
11.Patients will not willingly bite in CR if that is not.Patients will not willingly bite in CR if that is not
where the teeth fit best.where the teeth fit best.
2. An accurate clinical assessment of occlusal2. An accurate clinical assessment of occlusal
interfacing, even in CR, is suspect if tooth mobilityinterfacing, even in CR, is suspect if tooth mobility
is present.is present.
3. Border movements can be recorded.3. Border movements can be recorded.
4. Joint sounds can be heard.4. Joint sounds can be heard.
5. Lingual perspective of teeth cannot be seen5. Lingual perspective of teeth cannot be seen..

HAND-HELD CASTSHAND-HELD CASTS
1.1. When unmounted casts are set on their trimmed distalWhen unmounted casts are set on their trimmed distal
borders, only the facial perspective of the staticborders, only the facial perspective of the static
occlusion can be seen. If the casts are held in theocclusion can be seen. If the casts are held in the
hands without the wax bite, what is seen cannot behands without the wax bite, what is seen cannot be
relied on because all three vertical restraints arerelied on because all three vertical restraints are
exclusively dental.exclusively dental.
2.2. How the teeth interrelate when functioning cannot beHow the teeth interrelate when functioning cannot be
assessed with hand-held casts.assessed with hand-held casts.
3.3. Lingual perspective can be seen.Lingual perspective can be seen.

MOUNTED MODELSMOUNTED MODELS
HAND HELD CASTSHAND HELD CASTS
VsVs

1.1. Tooth mobility avoided by making impressions withTooth mobility avoided by making impressions with
soft materials to prevent deflection.soft materials to prevent deflection.
2.2. once casts are mounted - uncompromised picture of theonce casts are mounted - uncompromised picture of the
occlusal conditions can be observed.occlusal conditions can be observed.
3.3. Mounted casts lead to better diagnosis, better results,Mounted casts lead to better diagnosis, better results,
and to fewer retention problems.and to fewer retention problems.
4.4. How teeth interface in centric relation (CR) and whenHow teeth interface in centric relation (CR) and when
functioning can be seen facially and lingually withoutfunctioning can be seen facially and lingually without
patient's avoidance mechanism (proprioception).patient's avoidance mechanism (proprioception).

METHODS OF RECORDINGMETHODS OF RECORDING
MAXILLOMANDIBULAR RELATIONSMAXILLOMANDIBULAR RELATIONS
 Thielmann (1939)Thielmann (1939) – spiegelkinometer– spiegelkinometer
 Sears (1952)Sears (1952) – condyle migrator.– condyle migrator.
 Posselt (1957)Posselt (1957) – gnathothesiometer– gnathothesiometer
 BuhnerBuhner – Buhnergraph – for locating centric relation and– Buhnergraph – for locating centric relation and
verification of terminal hinge axis location.verification of terminal hinge axis location.
 Long (1973)Long (1973) – leaf gauge – shims made of acetate or– leaf gauge – shims made of acetate or
plasticplastic
 Williamson (1980)Williamson (1980) – vericheck– vericheck
 SLAVICEK (1988)-SLAVICEK (1988)- SAM articulator and MPISAM articulator and MPI

VERICHECK by WILLIAMSONVERICHECK by WILLIAMSON
The Vericheck instrument will measure the variation fromThe Vericheck instrument will measure the variation from
centric relation in three planes of spacecentric relation in three planes of space..

RECORDING CONDYLAR POSITIONRECORDING CONDYLAR POSITION
 FacebowFacebow
 ArticulatorsArticulators
 Mandibular Position Indicator(MPI)Mandibular Position Indicator(MPI)
 Electronic MPIElectronic MPI
 AxiographyAxiography
 Computerised AxiographyComputerised Axiography

FACEBOWFACEBOW
 First introduced byFirst introduced by RICHMOND HAYESRICHMOND HAYES- articulating- articulating
calipercaliper
 Later modified byLater modified by SNOWSNOW
 Serves to transfer 3-D relationship between Mx. DentalServes to transfer 3-D relationship between Mx. Dental
arch and starting point of mand. movement.arch and starting point of mand. movement.
 Transverse hinge axis- passes thru both condyles andTransverse hinge axis- passes thru both condyles and
associated with rotation of mand in vertical direction –associated with rotation of mand in vertical direction –
clinical relevanceclinical relevance- orientation of the maxillary cast.- orientation of the maxillary cast.
 TypesTypes
 ArbitraryArbitrary
 kinematickinematicwww.indiandentalacademy.comwww.indiandentalacademy.com

 Primary use- mount maxillary cast accurately onPrimary use- mount maxillary cast accurately on
the articulatorthe articulator
 Reference points-Reference points-
 1. Posterior- hinge axis1. Posterior- hinge axis
 2. Anterior- arbitrary2. Anterior- arbitrary
 Most semiadjustable articulators- rely on arbitraryMost semiadjustable articulators- rely on arbitrary
hinge axis.hinge axis.
 If a discrepancy exists between the hinge axis andIf a discrepancy exists between the hinge axis and
the articulator axis - premature contact will occurthe articulator axis - premature contact will occur
on the path of closure on the articulated model, noton the path of closure on the articulated model, not
present clinicallypresent clinically

Arbitrary facebow transferArbitrary facebow transfer
 Anatomic average values used based on the work ofAnatomic average values used based on the work of
SNOWSNOW
 Semiadjustable articulators rely on arbitrary hinge axisSemiadjustable articulators rely on arbitrary hinge axis
location.location.
 Line from tragus to outer canthus of eyeLine from tragus to outer canthus of eye
 11-13 mm from the tragus of ear- arbitrary location.11-13 mm from the tragus of ear- arbitrary location.
Kinematic face bow transferKinematic face bow transfer
 Required for fully adjustable articulators.Required for fully adjustable articulators.
 Recorded by using a special bow attached to the mandibleRecorded by using a special bow attached to the mandible
and is cemented to the teeth.and is cemented to the teeth.

Facebow – SAM 2Facebow – SAM 2

ARTICULATORSARTICULATORS
 First described by MITCHELL & WILKIE in 1958First described by MITCHELL & WILKIE in 1958
 Articulator- instrument that represents the TMJ and jawsArticulator- instrument that represents the TMJ and jaws
to which the maxillary and mandibular casts areto which the maxillary and mandibular casts are
attached. means of reproducing occlusal relationshipsattached. means of reproducing occlusal relationships
outside the mouth.outside the mouth.
 must be able to simulate an individual’s jaw movementmust be able to simulate an individual’s jaw movement
 mandibular movements are influenced by many softmandibular movements are influenced by many soft
tissue factors, hence impossible for jaw movements to betissue factors, hence impossible for jaw movements to be
precisely reproduedprecisely reprodued..

 semiadjustable articulators provide an adequatesemiadjustable articulators provide an adequate
representation of the true occlusion for orthodonticrepresentation of the true occlusion for orthodontic
diagnosis.diagnosis.
 Roth and Cordray - it is impossible to believe theRoth and Cordray - it is impossible to believe the
clinical finding as a true representation of occlusionclinical finding as a true representation of occlusion
- occlusal interferences.- occlusal interferences.
 only by articulator mounting can the true occlusiononly by articulator mounting can the true occlusion
be studied.be studied.

CLASSIFICATION OF ARTICULATORSCLASSIFICATION OF ARTICULATORS
FULLY ADJUSTABLEFULLY ADJUSTABLE SEMI-ADJUSTABLESEMI-ADJUSTABLE NON-ADJUSTABLENON-ADJUSTABLE
fivefive recordsrecords allall threethree recordsrecords 1 or 21 or 2 recordsrecords
Face bow recordFace bow record Face bow recordFace bow record Face bow recordFace bow record
Centric relation recordCentric relation record Centric relation recordCentric relation record Centric relation recordCentric relation record
Protrusive recordProtrusive record Protrusive recordProtrusive record Protrusive recordProtrusive record
Lateral recordsLateral records
Intercondylar distanceIntercondylar distance
recordrecord

Non adjustable articulatorsNon adjustable articulators
 average values are used to represent the inclinationaverage values are used to represent the inclination
of the glenoid fossa and condyle fossa relationship.of the glenoid fossa and condyle fossa relationship.
 cannot accurately reproduce an individual’scannot accurately reproduce an individual’s
mandibular excursive movements.mandibular excursive movements.
 only accurate position that can be used on aonly accurate position that can be used on a
nonadjustable articulator is one specific oclusalnonadjustable articulator is one specific oclusal
contact position.contact position.

AdvantagesAdvantages::
1.1. Inexpensive.Inexpensive.
2.2. Less time required to mount the casts.Less time required to mount the casts.
3.3. No procedures are required to mount casts.No procedures are required to mount casts.
DisadvantagesDisadvantages::
1.1. Restorations cannot be properly planned.Restorations cannot be properly planned.
2.2. Additional time is required to adjust theAdditional time is required to adjust the
restorations intraorallyrestorations intraorally..

Semi adjustable articulatorsSemi adjustable articulators
 can be modified by adjustments made in thecan be modified by adjustments made in the
condyle fossa portion of the instrumentcondyle fossa portion of the instrument
 Allows more variability in duplicatingAllows more variability in duplicating
condylar movements.condylar movements.
 It usually has 3 types of adjustmentsIt usually has 3 types of adjustments
1.1. Condylar inclination.Condylar inclination.
2.2. Lateral translation movement or Bennett angle.Lateral translation movement or Bennett angle.
3.3. Intercondylar distance.Intercondylar distance.

 condylar inclinationcondylar inclination: angle at which the: angle at which the
condyle descends. can be alteredcondyle descends. can be altered
 Bennett angleBennett angle: angle described by the orbiting: angle described by the orbiting
condyle during laterotrusive movements.condyle during laterotrusive movements.
semiadjustable articulators allow for a Bennettsemiadjustable articulators allow for a Bennett
angle movement only in a straight line.angle movement only in a straight line.
 Intercondylar distanceIntercondylar distance:: The distance betweenThe distance between
the rotational centers of the condyles.Threethe rotational centers of the condyles.Three
general settings - small, medium and large.general settings - small, medium and large.

Records requiredRecords required
1.1. Facebow transfer.Facebow transfer.
2.2. Centric relation interocclusal record.Centric relation interocclusal record.
3.3. Eccentric interocclusal recordsEccentric interocclusal records
1.1. The adaptability to patient’s specific condylar movement.The adaptability to patient’s specific condylar movement.
2.2. Accurately fitting restorations can be fabricated.Accurately fitting restorations can be fabricated.
Disadvantages:Disadvantages:
1.1. Initially more time is required.Initially more time is required.
2.2. More expensive than nonadjustable type.More expensive than nonadjustable type.
3.3. condylar path is in straight line, unlike the true condylarcondylar path is in straight line, unlike the true condylar
path, which follows a curved path.path, which follows a curved path.

Fully adjustable articulatorsFully adjustable articulators
 have a large range of adjustability in all threehave a large range of adjustability in all three
dimensionsdimensions
 most complex types of articulatorsmost complex types of articulators
 most sophisticated type for recordingmost sophisticated type for recording
mandibular movements.mandibular movements.
 adjustments that can be made areadjustments that can be made are
1.1. Condylar inclination.Condylar inclination.
2.2. Bennett angle.Bennett angle.
3.3. Rotating condylar movement.Rotating condylar movement.
4.4. Intercondylar distanceIntercondylar distance..

 Condylar inclinationCondylar inclination::Angle during protrusive andAngle during protrusive and
laterotrusive movements can be adjusted. capable oflaterotrusive movements can be adjusted. capable of
recording curvature of patients condylar movements.recording curvature of patients condylar movements.
 Bennett angleBennett angle:: both bennett angle and bennett shiftboth bennett angle and bennett shift
can be recordedcan be recorded..
 Rotating condylar movementRotating condylar movement::pathway of thepathway of the
rotating condyle duplicates that of the patientrotating condyle duplicates that of the patient..
 Intercondylar distanceIntercondylar distance:: can be adjusted in a fullycan be adjusted in a fully
adjustable articulator to match that in the patient moreadjustable articulator to match that in the patient more
precisely.precisely.

Records requiredRecords required::
1.1. An exact hinge axis location.An exact hinge axis location.
2.2. A pantographic recording.A pantographic recording.
3.3. A centric relation interocclusal record.A centric relation interocclusal record.
1.1. Ability to duplicate mandibular movements precisely.Ability to duplicate mandibular movements precisely.
2.2. Stable and anatomic interocclusal relatioship can beStable and anatomic interocclusal relatioship can be
obtained.obtained.
DisadvantagesDisadvantages::
1.1. Considerable amount of time is required.Considerable amount of time is required.
2.2. Highly expensive.Highly expensive. www.indiandentalacademy.comwww.indiandentalacademy.com

INDICATIONS FOR ARTICULATORINDICATIONS FOR ARTICULATOR
 When a significant discrepancy exists betweenWhen a significant discrepancy exists between
RCP & ICP (> 2mm).RCP & ICP (> 2mm).
 Orthodontic cases with multiple missing teeth.Orthodontic cases with multiple missing teeth.
 Cases undergoing orthognathic procedures.Cases undergoing orthognathic procedures.
 Mounting of study models pre orthodonticMounting of study models pre orthodontic
treatment and pre debond in individuals withtreatment and pre debond in individuals with
TMD is recommended.TMD is recommended.

USES OF ARTICULATORS INUSES OF ARTICULATORS IN
ORTHODONTICSORTHODONTICS
 For diagnosis and treatment planning.For diagnosis and treatment planning.
 For finishing.For finishing.
 In orthognathic surgical cases.In orthognathic surgical cases.

IN DIAGNOSIS AND TREATMENT PLANNINGIN DIAGNOSIS AND TREATMENT PLANNING
 Diagnosis carried out with teeth in ICP- misleading -Diagnosis carried out with teeth in ICP- misleading -
inappropriate treatment planinappropriate treatment plan..
 small proportion of patients have a large discrepancysmall proportion of patients have a large discrepancy
between RCP and ICP.between RCP and ICP.
 Such large discrepancies are not easy to diagnoseSuch large discrepancies are not easy to diagnose
clinically.clinically.
 may be necessary to deprogram the neuromusculature.may be necessary to deprogram the neuromusculature.
 Articulated models reveal the AP relationship ofArticulated models reveal the AP relationship of
maxilla and mandible more accurately.maxilla and mandible more accurately.
 ease with the visualisation of static and functionalease with the visualisation of static and functional
interrelationships of the teeth.interrelationships of the teeth.

 can be used to aid the clinician whether selectivecan be used to aid the clinician whether selective
grinding can be undertaken.grinding can be undertaken.
 sectioning of the teeth and repositioning them insectioning of the teeth and repositioning them in
wax - final results of orthodontics can be visualised.wax - final results of orthodontics can be visualised.
 orthodontic setup provides valuable information fororthodontic setup provides valuable information for
treatment planning.treatment planning.
 Patients with hypodontia and multiple missing teethPatients with hypodontia and multiple missing teeth
may not have a reproducible ICP. only reproduciblemay not have a reproducible ICP. only reproducible
relationship that can be recorded is RCP-requiresrelationship that can be recorded is RCP-requires
articulator mounted models.articulator mounted models.www.indiandentalacademy.comwww.indiandentalacademy.com

ARTICULATORS FOR FINISHINGARTICULATORS FOR FINISHING
 Non working side contacts are harmful to theNon working side contacts are harmful to the
dentition - trigger bruxism, TMJ disorders ordentition - trigger bruxism, TMJ disorders or
instability of tooth position. Hence theseinstability of tooth position. Hence these
interferences have to be eliminated.interferences have to be eliminated.

ARTICULATORS FORARTICULATORS FOR
ORTHOGNATHIC PLANNINGORTHOGNATHIC PLANNING
 essential part of presurgical preparationessential part of presurgical preparation
 ramus osteotomies - seperation of tooth bearing partsramus osteotomies - seperation of tooth bearing parts
of mandible from the condyle. no benefit inof mandible from the condyle. no benefit in
maintaining condyle tooth relationship during modelmaintaining condyle tooth relationship during model
surgery and hence an arbitrary mounting is sufficient.surgery and hence an arbitrary mounting is sufficient.
 maxillary surgery, autorotation of the mandible willmaxillary surgery, autorotation of the mandible will
be necessary - the condyle tooth relationship shouldbe necessary - the condyle tooth relationship should
be recorded as precisely as possible.be recorded as precisely as possible.

MANDIBULAR POSITION INDICATORMANDIBULAR POSITION INDICATOR
Dynamic and static positions of mandibleDynamic and static positions of mandible
determined by:determined by:
1.1. neuromuscular system and proprioceptivity.neuromuscular system and proprioceptivity.
2.2. morphology of hard and soft structures of the TMJ.morphology of hard and soft structures of the TMJ.
3.3. The morphology of the occlusal surfaces of the teeth.The morphology of the occlusal surfaces of the teeth.
4.4. Compromises necessitated by various skeletalCompromises necessitated by various skeletal
patterns.patterns.
5.5. Head posture and its relationship to the cervicalHead posture and its relationship to the cervical
spine.spine.
6.6. The limits of motion established by ligamentsThe limits of motion established by ligaments
attached to the mandible.attached to the mandible.www.indiandentalacademy.comwww.indiandentalacademy.com

MANDIBULAR POSITION INDICATORMANDIBULAR POSITION INDICATOR
 The M.P.I. quantifies differences between RCP &The M.P.I. quantifies differences between RCP &
ICP.ICP.
 used to perceive whether a clinically determinedused to perceive whether a clinically determined
symptom or sign can be related to differencessymptom or sign can be related to differences
between the patient's RCP and ICP, if early signs ofbetween the patient's RCP and ICP, if early signs of
discopathy are present, and if a treatment plan todiscopathy are present, and if a treatment plan to
move the teeth will result in an occlusion in whichmove the teeth will result in an occlusion in which
RCP and ICP are compatible.RCP and ICP are compatible.

MOUNTING OF CASTSMOUNTING OF CASTS
 Accurate impressionsAccurate impressions
 Stone castsStone casts

 Base of casts –Base of casts –
Split cast formerSplit cast former

Anatomic facebow oriented to soft tissue porion and orbitaleAnatomic facebow oriented to soft tissue porion and orbitale..

Face bow record transferred to articulatorFace bow record transferred to articulator

Recording centric relationRecording centric relation
Mandible guided into retralMandible guided into retral
position by theposition by the
operator(guided by theoperator(guided by the
thumb and forefinger atthumb and forefinger at
gnathion)gnathion)

Roth power centricRoth power centric
 Anterior segment- 3Anterior segment- 3
thickness wax. Canine-thickness wax. Canine-
canine.canine.
 Posterior segement – 2Posterior segement – 2
thickness wax. Molarthickness wax. Molar
region.region.

Roth power centric techniqueRoth power centric technique

M.P.I PROCEDUREM.P.I PROCEDURE
 Adhesive grid paper- onAdhesive grid paper- on
incisal tableincisal table
 Upper member lowered toUpper member lowered to
first contactfirst contact
 Incisal pin loweredIncisal pin lowered
 Grid mark – red markingGrid mark – red marking
 Vertical height of pinVertical height of pin
noted.noted.

maxillary cast is transferredmaxillary cast is transferred
to the M.P.I.to the M.P.I.
M.P.I and upper part of theM.P.I and upper part of the
SAM 2 articulator areSAM 2 articulator are
identical, except condylaridentical, except condylar
housing are replaced withhousing are replaced with
sliding blocks in the M.P.Isliding blocks in the M.P.I

 Mounted maxillaryMounted maxillary
cast is interdigitatedcast is interdigitated
with mandibular castwith mandibular cast
 Adhesive grids withAdhesive grids with
X, Z coordinates areX, Z coordinates are
placed on the lateralplaced on the lateral
sliding blocks of thesliding blocks of the
M.P.I.M.P.I.

 Adhesive grid on blackAdhesive grid on black
cubes of MPIcubes of MPI
 Mark position ofMark position of
condylar spheres withcondylar spheres with
black articulating paperblack articulating paper
(hinge axis position)(hinge axis position)

 Incisal pin vertical reading –Incisal pin vertical reading –
Delta HDelta H
 Horizontal difference betweenHorizontal difference between
RCP &ICP read at incisalRCP &ICP read at incisal
table -table - Delta LDelta L
 Dial gauge reading –Dial gauge reading – Delta YDelta Y

 Cubes slid medially toCubes slid medially to
perforate grid.perforate grid.
 Point of perforationPoint of perforation
indicates hinge axisindicates hinge axis..

ResultsResults
 Delta HDelta H = vertical increase or decrease read from= vertical increase or decrease read from
the incisal pin.the incisal pin.
 Delta LDelta L = protrusive or retrusive movement= protrusive or retrusive movement
measured from tne incisal table (grid)measured from tne incisal table (grid)
 Delta XDelta X = protrusive or retrusive. Indicates= protrusive or retrusive. Indicates
differences in horizontal condylar position.differences in horizontal condylar position.
 Delta ZDelta Z = compression or distraction. Indicates= compression or distraction. Indicates
differences in vertical condylar position.differences in vertical condylar position.
 Delta YDelta Y = right or left transverse movement.= right or left transverse movement.
Indicates differences in transverse condylarIndicates differences in transverse condylar
position.position.

ICP (black dot) aboveICP (black dot) above
RCP (red dot) indicatesRCP (red dot) indicates
compression.compression.
ICP (black dot) belowICP (black dot) below
RCP (red dot)RCP (red dot)
indicates distraction.indicates distraction.

ELECTRONIC MPIELECTRONIC MPI
 displays data that are the same as those takendisplays data that are the same as those taken
manually with the M.P.I. Standard records aremanually with the M.P.I. Standard records are
designated numerically as the differences between:designated numerically as the differences between:
1. RCP and the intercuspal position (ICP)1. RCP and the intercuspal position (ICP)
2. RCP and bilateral joint resilience (RES)2. RCP and bilateral joint resilience (RES)
3. RCP and estimated therapeutic position (ETP)3. RCP and estimated therapeutic position (ETP)
4. RCP and ideal vertical position (IVP)4. RCP and ideal vertical position (IVP)
5. RCP and forced bite position (FBP)5. RCP and forced bite position (FBP)
6. ICP and a new ICP after full-mouth6. ICP and a new ICP after full-mouth openingopening

AXIOGRAPHYAXIOGRAPHY
 Axiograph - diagnostic instrument- simulatesAxiograph - diagnostic instrument- simulates
condylar movement pathways.condylar movement pathways.
 The procedure is calledThe procedure is called AXIOGRAPHYAXIOGRAPHY. The. The
graphic output is calledgraphic output is called AXIOGRAM.AXIOGRAM.
 Records movements in all 3 planes of space.Records movements in all 3 planes of space.
 Early detection of subclinical discopathies.Early detection of subclinical discopathies.

Normal jointNormal joint
 Reference plane-Reference plane-
hinge axis.hinge axis.
 The axiographThe axiograph
simultaneouslysimultaneously
records hinge-axisrecords hinge-axis
movements in all 3movements in all 3
planes.planes.

 Facebow ofFacebow of
axiographaxiograph
attached toattached to
cranium.cranium.
 Hinge-axis bowHinge-axis bow
anchored to theanchored to the
mandible withmandible with
functionalfunctional
occlusion clutch.occlusion clutch.

Tracing of hinge axis movementTracing of hinge axis movement
 Three dimensional recording asThree dimensional recording as
stylus is replaced by dial gauge.stylus is replaced by dial gauge.

 Deranged joint- location and repeatability of aDeranged joint- location and repeatability of a
reference position is impossible.reference position is impossible.
 Difficulty to locate hinge axis may be due toDifficulty to locate hinge axis may be due to
1.1. Flattened condylar head.Flattened condylar head.
2.2. InflammationInflammation
3.3. Internal derangement.Internal derangement.
4.4. Loose ligaments.Loose ligaments.
5.5. Structural asymmetriesStructural asymmetries
6.6. Muscle imbalance.Muscle imbalance.

 Movements traced areMovements traced are
1.1. protrusion-retrusion,protrusion-retrusion,
2.2. opening-closing,opening-closing,
3.3. unguided mediotrusion-medioretrusion, rightunguided mediotrusion-medioretrusion, right
and then left;and then left;
4.4. guided mediotrusion-medioretrusion, right andguided mediotrusion-medioretrusion, right and
then leftthen left..
 Joint sounds – crepitation and clicking shouldJoint sounds – crepitation and clicking should
be recorded.be recorded.

Bennett movementBennett movement
 Mediolateral movement ofMediolateral movement of
the mandible measuredthe mandible measured
along the Y axis.along the Y axis.
 Bennett value altered byBennett value altered by
1.1. Medially displacedMedially displaced
meniscusmeniscus
2.2. LuxationLuxation
3.3. Subluxation.Subluxation.
4.4. Reduction.Reduction.

Resiliency testResiliency test
 Determines the ability to move the hinge-axis positionDetermines the ability to move the hinge-axis position
superiorly anteriorly to a loaded positionsuperiorly anteriorly to a loaded position
 Children -1mm of resiliency, young adult .5mm, andChildren -1mm of resiliency, young adult .5mm, and
middle-aged or elderly patients .3mm.middle-aged or elderly patients .3mm.
 No joint resiliency- results in deroundation - flatteningNo joint resiliency- results in deroundation - flattening
of the condyle head. Resiliency below normal requiresof the condyle head. Resiliency below normal requires
treatment with splints.treatment with splints.

Joint resiliency testJoint resiliency test
 Upward pressureUpward pressure
 Condyle displacedCondyle displaced
superiorly &superiorly &
anteriorlyanteriorly

Interpretation of AxiograpicInterpretation of Axiograpic
TracingsTracings
Sagittal movementsSagittal movements
 Coincide for first 10-Coincide for first 10-
12mm12mm
 Bilaterally symmetricalBilaterally symmetrical
 No Bennett movement.No Bennett movement.
(0.2-0.3 mm acceptable)(0.2-0.3 mm acceptable)

Sagittal movementsSagittal movements
When movements doWhen movements do
not coincidenot coincide
1.1. Muscle limitationMuscle limitation
2.2. Differentiate betweenDifferentiate between
muscular andmuscular and
ligamentous limtation.ligamentous limtation.
3.3. Correlate with clinicalCorrelate with clinical
findings.findings.

Protrusion – retrusion tracingsProtrusion – retrusion tracings
 Normally coincideNormally coincide in pattern and timingin pattern and timing
 Position altered by loose ligaments.Position altered by loose ligaments.
 Asymmetry in timing seen due to in coordinationAsymmetry in timing seen due to in coordination
of medial and lateral pterygoids.of medial and lateral pterygoids.
 Limited movement seen in class II div IILimited movement seen in class II div II
 No transverse deviation of bennett movement –No transverse deviation of bennett movement –
deviation indicates incipient discopathydeviation indicates incipient discopathy..

Mediotrusion – MedioretrusionMediotrusion – Medioretrusion
 principally a unilateral translation, with minimalprincipally a unilateral translation, with minimal
vertical movement.vertical movement.
 The condyle head rotates minimally within theThe condyle head rotates minimally within the
inferior concavity of meniscus.inferior concavity of meniscus.
 If tracings do not coincide - indicative of looseIf tracings do not coincide - indicative of loose
ligaments, subluxation, luxation, or reduction.ligaments, subluxation, luxation, or reduction.
 Medially displaced meniscus restrictsMedially displaced meniscus restricts
movement.movement.

Opening/closing movementsOpening/closing movements
 Opening movement involves the rotationalOpening movement involves the rotational
component of the mandible - is extremelycomponent of the mandible - is extremely
important in diagnosing morphological changesimportant in diagnosing morphological changes
in the head of the condyle.in the head of the condyle.
 Comparisons between rotational and translatoryComparisons between rotational and translatory
movements are paramount to a proper diagnosis.movements are paramount to a proper diagnosis.
 Rotational movements- lower joint abnormalitiesRotational movements- lower joint abnormalities
 Translatory movements- upper jointTranslatory movements- upper joint
abnormalities.abnormalities.

Overrotation of mandibleOverrotation of mandible

Deroundation of condyleDeroundation of condyle

Muscle distractionMuscle distraction

Highly active temporalisHighly active temporalis

Loose jointLoose joint

Functional distractionFunctional distraction

COMPUTER AIDED AXIOGRAPHYCOMPUTER AIDED AXIOGRAPHY
 enhances the tracking of hinge-axisenhances the tracking of hinge-axis
movements in all 3 planes along with timing ofmovements in all 3 planes along with timing of
movement and accuracy.movement and accuracy.
 computer displays the condylar movement incomputer displays the condylar movement in
real time.real time.

Locating hinge axisLocating hinge axis
 Located by having the patient rotate open,Located by having the patient rotate open,
without translation, for at least 10mm- If thewithout translation, for at least 10mm- If the
stilus is not on the hinge-axis position it willstilus is not on the hinge-axis position it will
scribe an arc.scribe an arc.
 uses this arc to form a circle and then calculatesuses this arc to form a circle and then calculates
its center, which is the site of pure rotation— theits center, which is the site of pure rotation— the
true hinge-axis.true hinge-axis.
 Accuracy of location- 0.01mmAccuracy of location- 0.01mm
 Accuracy of manual method – 0.2 mmAccuracy of manual method – 0.2 mm

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