Instrumental functional analysis / /certified fixed orthodontic courses by Indian dental academy

Instrumental Functional
Analysis

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INDIAN DENTAL ACADEMY
Leader in continuing dental education


What is Instrumental Analysis



Mounted casts
Mandibular position






RCP – Hinge axis – Centric relation
ICP

Mandibular movements
Condyle/disc complex


Why do an Instrumental Analysis


The mouth is the worst articulator






Morphology of the occlusal surfaces of the
teeth.
Neuromuscular adaptation to the occlusion
(proprioception)
The morphology of the hard and soft
structures of the TMJ







Ligaments attached to the mandible.
Compromises necessitated by various
skeletal patterns.
Head posture and total body posture.






Hand held casts  ICP
Articulator mounting  functioning of
mandible




Once the casts are mounted on the
articulator


Compare RCP and ICP.



Accurately see max-mand relation.



3 dimensional determination of position of
condyles in fossa.


The SAM 2 Articulator


Made for diagnosis



Semi-adjustable



MPI and Axiograph


Mandibular Position Indicator




Measures deviation
from RCP to ICP
3-dimensional
measurements


Axiograph





Records
mandibular
movements
Dynamic record
Takes into account
PDL, Muscles, Soft
tissues etc.


Mounting casts on the SAM 2




Accurate
impressions
Stone casts




Base of casts –
Split cast former




Face bow record


Oriented to soft
tissue Po and
Orbitale.




Face bow record transferred to acticulator






Obtaining
interocclusal record
Deprogramming




Mandible guided
into retral position
by the operator




Roth power centric
technique.




Delar wax
Ant – 6 thicknesses
Post – 2 thicknesses







Orient upper and
lower casts with wax
bite.
Mount lower
3 wax bites – to
confirm accuracy


Use of the MPI






Adhesive grid on
incisal table
Grid mark
Incisal pin reading
Articulator
programmed with 3
co-ordinates

Use of the MPI




Transfer max. cast
to MPI
Exactly same
relation as to upper
member.


Use of the MPI






Max. cast
interdigitated with
mand. Cast.
Incisal pin reading
(Delta H).
Mark on incisal
table grid (Delta L).

Use of the MPI




Adhesive grid on
black cubes of MPI
Mark position of
condylar spheres
with blue
articulating paper.

Use of the MPI






Pin of the dial
placed into cube.
Cube slid against
condylar sphere.
Dial gauge reading
(Delta Y)

Use of the MPI




Cubes slid medially
to perforate grid.
Point of perforation
indicates hinge
axis.


Use of the MPI


Data obtained from
MPI:



3 grids
Incisal pin reading
Dial gauge reading


Use of the MPI


Results obtained –






Delta H = vertical increase or decrease
Delta L = protrusive or retrusive movement
Delta X = protrusive ( + ) or retrusive ( – )
Delta Z = compression ( + ) or distraction ( – )
Delta Y = right or left transverse movement


Use of the MPI


Interpreting the results




RCP and ICP
correspond.
ICP is displaced below
RCP - distraction


Use of the MPI
ICP

is above RCP compression
Plus or minus Delta Y
values - the condyle is
being repositioned
medially or laterally by
the maximum
intercuspation of teeth

Axiography


Records mandibular movements in all 3
planes of space.



Diagnosis of subclinical discopathies.



Similar data from MPI – more dynamic.


Axiography


Facebow – on cranium.






2 vertical bars
(parasaggital flag bows)
2 grids.

2nd part anchored to
mandible.


Axiography


Tray or



Para-occlusal clutch


Axiography







Locate hinge position – as reference
position.
Open and close mandible – teeth don’t
touch.
Stylus should purely rotate at one point.
May be difficult to locate in some
patients.

Axiography






All mandibular movements related to
this.
Adolescents – 1 mm anterior.
Reference position marked on the
graph.


Axiography




Stylus replaced by a
dial gauge.
Three dimensional
recording.


Axiography


Step 1 - Movements 


Protrusion-retrusion;



opening-closing;



unguided mediotrusion



guided mediotrusion


Axiography


Step 2 – Joint
resiliency test.



Upward pressure
Condyle displaced
superiorly & anteriorly.


Axiography






Child  1 mm
Young adult  0.5mm
Middle age
/Elderly  0.3 mm
Less = no protection
against strong forces.


Axiography


No resiliency 





Flattening of codylar
head
Disc derrangements
Splint therapy
indicated


Axiography






Step 3 - Maximum intercuspation mark the position.
Step 4 - Habitual occlusion - mark the
position.
Step 5 - Phonation, mastication, rest
position, swallowing –record the border
positions.

Interpretation of Axiograpic
Tracings
Sagittal movements


Coincide for first 10-12mm



Bilaterally identical



No Bennett movement.
(0.2-0.3 mm acceptable)


Tracings
Sagittal movements


Muscle in-coordination





Bilat. not symmetrical
Unable to repeat
movement smoothly.
Co-relate with clinical
findings.


Tracings


Protrusion & Retrusion –
coincide in pattern and
timing
 Loose ligaments – alter
position of disc
 Superior line for prot.
 Inferior line for ret.
 No Bennett mov. –
check Pteryoids


Tracings


Mediotursive movement






Condyle rotates in the inf. Concavity of disc
Disc translates along the eminence
Tracing = morphology of the eminence

Tracings of movt. should coincide


Tracings


Causes for not
coinciding –





loose ligaments
subluxation
luxation
reduction


Tracings
Fischer Angle
Normal movement

Movement due to
displaced disc


Tracings






Positive Bennett movt.
should be seen.
If not – avoidance of
prematurities
Negative Bennett movt.
= displaced disc.


Tracings


Mediotrusive tracings





Unguided
Guided

Helps in differential diagnosis
-muscles or ligaments (?)


Tracings
Opening and closing




Translatory movements  upper
compartment
Rotational movements  lower
compartment


Tracings








Opening and closing
should coincide
Flattening of condylar
head  don’t coincide.
Radiographic
evaluation.
Degenerative bone
disease? Pain?


Tracings – Special Situations


Over rotation of
mandible at end of
full mouth opening




Muscle distraction



Pain of muscles
Correlate findings of
palpation.




Condyle ant. to
reference position



Loose ligaments
Hyperactive muscles




During ICP



Prematurities
Functional distraction


Reciprocal Click
Disk is pulled anteriorly (on
protrusion)
Condyle is repositioned in the
disc
Normal movement
Condyle slips away from the
disc



Hyperactive
temporalis muscle.


Computer Aided Axiography


Advantage –





Mand. movements in X, Z and Y (Bennett)
planes are recorded directly into the
computer.
Timing of movement is also measured
Accuracy






Location of hinge
axis
Repeated
movements can be
superimposed


CADIAS


History,



Clinical examination,



Muscle palpation,



Instrumental analysis,



Model analysis and



Cephalometric analysis,



Growth predictions,



Skeletal and dental VTO and



Different cephalometric
analyses.


A Comparison Of Mandibular
Condylar Location Between
Unstrained Retral Position And
Maximum Intercuspal Position In
Temporomandibular Dysfunction
Cases And In Asymptomatic
Subjects, Using A Mandibular
Position Indicator
Dr. Divakar H. S.
MDS Dissertation – Feb 1995

Introduction






Is condylar position important in etiology of
TMD? – Inconclusive evidence
If ‘Yes’ then how much.
Comparison between patients with TMD
and Asymptomatic patients.


Introduction
Methods of assessing condylar position
 Radiographic







Transcranial
Laminography (CT Scan)

MRI
Sonography
Clinical Methods



Axiograph
MPI


Materials and Methods


40 patients








25 with TMD symptoms
15 asypmptomatic
No h/o arthritis, trauma or ortho. treatment.

History, photographs – Rest position &
ICP
Procedure for SAM and MPI

Results


All MPI readings found to be very similar


Range and means very close



No statistical significance even at 10%


Discussion

Symptomatic Asymptomatic
(25)

No Anteroposterior
displacement
No Vertical
displacement

(15)

3 (12%)

None

5 (20%)

2 (13%)


Discussion


Range of movements




Greater than suggested by Roth (both groups)

Asymmetric movements


25% subjects in both groups


Summary and Conclusions


Condylar shift occurred in both groups



No significant difference in amount of shift



Asymmetric movements in both groups



TMD cannot be predicted using condylar
position

An Evaluation Of Condylar Position
In Class II Div. 2 Malocclusion
Using The Mandibular Position
Indicator
Dr. Sonali M.
MDS Dissertation – Feb 1998

Introduction







Posterior position of condyle in Class II
div 2 patients – often used to advantage.
Is it true?
Correlation with overjet, overbite jaw
sizes, incisor inclinations?
Cause of TMD?




30 subjects







14 male, 16 female
10-30 yrs

Upright or lingually inclined incisors
50% or more of overbite
Overjet upto 4 mm







History – including symptoms of TMD
Clinical examination
Study models, lateral ceph
Mounted casts of SAM 2 articulator, and
use of MPI to assess condylar position.


Results


Results were tabulated








Condylar position at ICP – both sides
seperately
Overjet
Overbite
Size of both jaws
Incisor inclinations and relationship
Other MPI readings (Vertical pin reading, Dial
gauge reading, incisal table reading

Results




18 of the 30 – retrusion of at least 1
condyle
Correlation of retrusion with other features






No correlation with overjet
No correlation with overbite
Size of mandible – large mandible in pts with
retrusive condyles
Maxilla was small in most cases

Results









Amount of max. incisor retroclination did not
affect posterior placement.
No correlation with inclination of lower
incisors.
No correlation with inter incisal angle.
Retrusion of condyle may be associated with
TMD – Asymmetric placement more prone.
TMD symptoms – seen more in adult pts.

Clinical implications




Pts with retrusion may develop TMD later
in life.
Anterior relocation seen in pts with
retrusion of condyle – not if condyle is
normally placed.


References




JCO Interviews : Dr. Slavicek on clinical and
instrumental functional analysis for diagnosis and
treatment planning. July 1988
Clinical and instrumental functional analysis for diagnosis
and treatment planning Parts 4 – 7. JCO Sept – Dec
1988



MDS Dissertation – Feb 1995 – Dr. Divakar H.S.



MDS Dissertation – Feb 1998 – Dr. Sonali M



Concepts in functional occlusion and management of
functional disorder of TMJ - Dr. N. R. Krishnaswamy Manual of the 7th IOS PG Convention

Thank you
Leader in continuing dental education


Instrumental functional analysis / /certified fixed orthodontic courses by Indian dental academy

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