This document discusses instrumental functional analysis, which involves mounting dental casts onto an articulator to analyze mandibular position and movement. It describes using a Mandibular Position Indicator (MPI) and axiography to obtain measurements of the difference between a patient's retruded contact position and maximum intercuspal position. The MPI provides vertical, horizontal, and lateral displacement data, while axiography produces a dynamic record of mandibular movements. Comparing MPI readings from symptomatic TMJ patients and asymptomatic subjects found no statistically significant differences in condylar position between groups. This suggests that displacement alone may not be a primary factor in TMJ disorders.
2. INDIAN DENTAL ACADEMY
Leader in continuing dental education
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3. What is Instrumental Analysis
Mounted casts
Mandibular position
RCP – Hinge axis – Centric relation
ICP
Mandibular movements
Condyle/disc complex
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4. 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
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5. Why do an Instrumental Analysis
Ligaments attached to the mandible.
Compromises necessitated by various
skeletal patterns.
Head posture and total body posture.
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6. Why do an Instrumental Analysis
Hand held casts ICP
Articulator mounting functioning of
mandible
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7. Why do an Instrumental Analysis
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.
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8. The SAM 2 Articulator
Made for diagnosis
Semi-adjustable
MPI and Axiograph
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11. Mounting casts on the SAM 2
Accurate
impressions
Stone casts
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12. Mounting casts on the SAM 2
Base of casts –
Split cast former
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13. Mounting casts on the SAM 2
Face bow record
Oriented to soft
tissue Po and
Orbitale.
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14. Mounting casts on the SAM 2
Face bow record transferred to acticulator
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15. Mounting casts on the SAM 2
Obtaining
interocclusal record
Deprogramming
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16. Mounting casts on the SAM 2
Mandible guided
into retral position
by the operator
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17. Mounting casts on the SAM 2
Roth power centric
technique.
Delar wax
Ant – 6 thicknesses
Post – 2 thicknesses
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18. Mounting casts on the SAM 2
Orient upper and
lower casts with wax
bite.
Mount lower
3 wax bites – to
confirm accuracy
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19. Use of the MPI
Adhesive grid on
incisal table
Grid mark
Incisal pin reading
Articulator
programmed with 3
co-ordinates
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20. Use of the MPI
Transfer max. cast
to MPI
Exactly same
relation as to upper
member.
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21. Use of the MPI
Max. cast
interdigitated with
mand. Cast.
Incisal pin reading
(Delta H).
Mark on incisal
table grid (Delta L).
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22. Use of the MPI
Adhesive grid on
black cubes of MPI
Mark position of
condylar spheres
with blue
articulating paper.
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23. Use of the MPI
Pin of the dial
placed into cube.
Cube slid against
condylar sphere.
Dial gauge reading
(Delta Y)
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24. Use of the MPI
Cubes slid medially
to perforate grid.
Point of perforation
indicates hinge
axis.
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25. Use of the MPI
Data obtained from
MPI:
3 grids
Incisal pin reading
Dial gauge reading
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26. 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
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27. Use of the MPI
Interpreting the results
RCP and ICP
correspond.
ICP is displaced below
RCP - distraction
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28. 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
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29. Axiography
Records mandibular movements in all 3
planes of space.
Diagnosis of subclinical discopathies.
Similar data from MPI – more dynamic.
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30. Axiography
Facebow – on cranium.
2 vertical bars
(parasaggital flag bows)
2 grids.
2nd part anchored to
mandible.
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32. 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.
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37. Axiography
Child 1 mm
Young adult 0.5mm
Middle age
/Elderly 0.3 mm
Less = no protection
against strong forces.
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39. 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.
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40. Interpretation of Axiograpic
Tracings
Sagittal movements
Coincide for first 10-12mm
Bilaterally identical
No Bennett movement.
(0.2-0.3 mm acceptable)
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41. Interpretation of Axiograpic
Tracings
Sagittal movements
Muscle in-coordination
Bilat. not symmetrical
Unable to repeat
movement smoothly.
Co-relate with clinical
findings.
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42. Interpretation of Axiograpic
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
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43. Interpretation of Axiograpic
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
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49. Interpretation of Axiograpic
Tracings
Opening and closing
should coincide
Flattening of condylar
head don’t coincide.
Radiographic
evaluation.
Degenerative bone
disease? Pain?
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54. Interpretation of Axiograpic
Tracings – Special Situations
Reciprocal Click
Disk is pulled anteriorly (on
protrusion)
Condyle is repositioned in the
disc
Normal movement
Condyle slips away from the
disc
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56. 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
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61. 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
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62. Introduction
Is condylar position important in etiology of
TMD? – Inconclusive evidence
If ‘Yes’ then how much.
Comparison between patients with TMD
and Asymptomatic patients.
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64. 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
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65. Results
All MPI readings found to be very similar
Range and means very close
No statistical significance even at 10%
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68. 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
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69. An Evaluation Of Condylar Position
In Class II Div. 2 Malocclusion
Using The Mandibular Position
Indicator
Dr. Sonali M.
MDS Dissertation – Feb 1998
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70. 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?
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71. Materials and Methods
30 subjects
14 male, 16 female
10-30 yrs
Upright or lingually inclined incisors
50% or more of overbite
Overjet upto 4 mm
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72. Materials and Methods
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.
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73. 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
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74. 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
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75. 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.
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76. 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.
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77. 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
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