Full mouth rehabilitation/ Labial orthodontics

Part V
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

Contents
 Factors that determine disclusion
 Disocclusion
 Classification of occlusal rehabilitation
 Hobo’s twin table technique
 Hobo’s twin stage technique
 Conclusion

Factors that determine disclusion
I. Anterior guidance
II. Condylar guidance
III. Cusp angulation

 Takayama and Hobo derived kinematic formulae to
calculate anterior guidance from the condylar path.
Anterior guidance computed from these formulae
confirmed a statistical correlation to the data of
anterior guidance on the same patients at p < 0.01 level
of significance.

Angle of hinge rotation
 The mandible rotates around
the intercondylar axis during
eccentric movements when
anterior guidance is steeper
than the condylar path. The
factor that compensates for the
difference in steepness is the
angle of hinge rotation.

 Takayama and Hobo analyzed disclusion relative to the
angle of hinge rotation by using kinematic formulae.
The results indicated that the angle of hinge rotation
contributed to posterior disclusion by approximately
0.2 mm for protrusive movement
0.5 mm on average for lateral movement on both
working and nonworking sides.

 The amounts of disclusion were
1.1 +- 0.6 mm during protrusive movement
0.5 +- 0.3 mm on the working side
1.0 +- 0.6mm on the nonworking
 Measured at the mesiobuccal cusp tip of the mandibular
first molar .

Degree of disclusion
Measured
value
Angle of
hinge axis
Cusp shape
factor
Protrusive 1.1 0.2 0.9
Working 0.5 0.5 0
Non working 1.0 0.5 0.5

Cusp shape factor

 If the shapes of the posterior
cusps are less steep than the
condylar path, the posterior
teeth disclude even if anterior
guidance is parallel to the
condylar path.
 The semicircular shape of the
cusps affects the posterior
disclusion.
 This is called Cusp shape face .

Disocclusion

Deviation of condylar path
 When repetitive lateral movements were compared
with the respective condylar paths, no movement
traced the same line. The deviation in the condylar
path during eccentric movements was attributed to the
shock-absorbing nature of the articular disk. This
deviation in condylar path is referred as a "buffer
space."

Buffer space
(mm)
Disclusion (mm)
Protrusive 0.8 1.1
Working 0.3 0.5
Non working 0.8 1.0

The width between the eccentric and the returning
condylar path measured at 2mm from the condylar
position in maximum intercuspation.

Width between eccentric and
returning condylar path
Unit (mm) Mean SD
Protrusive
movement
0.44 0.26
Lateral movement 0.79 0.37

Comparison between sagittal condylar path
inclinations of eccentric and returning path
Unit (mm)
Eccentric path Returning path Differen
ce
Mean SD Mean SD Mean
Protrusive
movement
40.1 13.8 27.4 7.6 12.7
Lateral
movement
40.5 11.8 17.5 10.9 23.0

 Standard amount of disocclusion at second molars was
1.0 mm at protrusive movement of 3 mm.
 When the sagittal condylar path inclination decreased,
it displaced the position of the cusp of the mandibular
second molar in a superior direction by 0.020mm per
degree.
Influence of condylar path on
amount of disocclusion

 Rate of influence of sagittal lateral condylar path
inclination is
0.015 mm on the non working side
– 0.002 mm on the working side per degree.
 The influence of deviation in the condylar path on the
amount of disclusion was calculated :
 Protrusive : 0.26 mm
 Non working side : 0.35 mm
 Working side : - 0.05 mm

 When sagittal inclination decreases by one degree,
amount of disclusion decreases by
Protrusive : 0.038 mm
 When frontal inclination decreases by one degree,
amount of disclusion decreases by
Non working : 0.042 mm
Working : 0.038 mm
Influence of incisal path on
amount of disocclusion

Variation in incisal path is approximately 10 degrees
 Protrusive : 0.38 mm
 Non working : 0.42 mm
 Working : 0.38 mm

Cusp angle

 When the cusp angle increases by one degree the amount
of disclusion decreases by
0.046 mm during protrusive movement
0.046 mm on the non working side
0.041 on the working side.
 The influence of cusp angle is 40% - 44% of the total
influence far greater than condylar path but comparable
to incisal path.

Classification of occlusal
rehabilitation

There are four types of occlusal rehabilitation
situations:
A. The curve of Spee and the incisal guidance are
acceptable and the posterior teeth need rehabilitation.
The treatment plan includes the restoration of the lower
posterior teeth to the patient's curve of Spee.
 Then the upper posterior teeth are restored by the
functionally generated path technique.

B. The curve of Spee is irregular, but the incisal guidance is
acceptable.
The treatment plan involves the restoration of the lower
posterior teeth to a more desirable curvature.
Then the upper posterior teeth are restored with the
functionally generated path technique and the existing
incisal guidance.

C. The curve of Spee and the incisal guidance are both
unacceptable.
 The treatment plan involves:
 The correction of the incisal guidance by restoring the
upper anterior teeth by means of jackets or pinlays
 The restoration of the lower posterior teeth to a more
desirable occlusal curvature
 The restoration of the upper posterior teeth with the use
of the functionally generated path technique.

D. The curve of Spee and the incisal guidance are not acceptable,
and the upper and lower anterior teeth need rehabilitation.
 The treatment plan involves:
 The restoration of all the lower anterior teeth
 The restoration of the upper anterior teeth and the incisal
guidance
 The restoration of the lower posterior teeth to a more
acceptable occlusal curvature, and
 The restoration of upper posterior teeth with the use of the
functionally generated path technique

Hobo’s twin table
technique

It is critical to form the resin cones toward the outer
edge of the path.

Hobo’s twin stage
technique

STANDARD VALUE OF THE CUSP ANGLE
 Since there are minimal variations in cusp morphology
of permanent teeth immediately after eruption, and if
the value of the cusp angle at the time of eruption is
used as a reference for occlusion, making a restoration
following this guide should be ideal for the patient.

Cusp angle Cusp angle on molars (deg)
Sagittal protrusive effective 25
Frontal lateral effective
(working side)
15
Frontal lateral effective
(non working side)
20
Standard values of effective cusp angles
on molars

 Adjust the condylar path to 40 degrees and the anterior
guide table to 45 degrees when fabricating anterior
guidance with the anterior segment attached to the cast.
In this manner,
(1) The standard amount of disocclusion will be
obtained on molars
(2) A physiological anterior guidance will be fabricated.

Physiological discrepancy
If the sagittal condylar path of the patient is steeper than
the articulator adjustment value (40 degrees), the
amount of disocclusion increases.
If the condylar path in the patient is shallower than 40
degrees, the amount of disocclusion decreases to some
extent.
 The sagittal condylar path distributes +/- 14 degrees
(SD) from the mean value (40 degrees).

 Presently, the twin-stage procedure is contraindicated
in the following cases :
A. Abnormal curve of Spee
B. Abnormal curve of Wilson
C. Abnormally rotated tooth
D. Abnormally inclined tooth

Stage I: Fabrication of the cusp angle
 Adjust an articulator to the following values:
 Sagittal condylar path inclination =25 degrees
 Bennett angle=15 degrees
 Sagittal inclination of the anterior guide table=25
degrees
 Lateral wing angle=10 degrees.

 Make the anterior segment of the maxillary or
mandibular cast removable using dowel pins.
 Remove the anterior segment.
 Make the maxillary and mandibular casts on the
articulator so that they do not disocclude during
eccentric movement.
 Balanced articulation is obtained and every cusp will
have a standard cusp angle

Stage II: Fabrication of anterior teeth
 Adjust an articulator to the following values:
 Sagittal condylar path inclination=40 degrees
 Bennett angle=15 degrees
 Sagittal inclination of the anterior guide table=45
degrees
 Lateral wing angle=20 degrees

 Reassemble the anterior segment of the cast.
 The maxillary and mandibular casts on the articulator
produce the standard amount of disocclusion.
 Wax the palatal contours of the maxillary anterior teeth
so incisors contact during protrusive movement, and the
canines on the working side contact during lateral
movement.
 Anterior guidance is established and the standard
amount of disocclusion will be produced.

Articulator adjustments for twin stage
Stage
Condylar path Anterior guide
table
Sagittal
path
inclination
Bennett
angle
Sagittal
inclination
Lateral
wing
angle
Stage I: without
anterior teeth
25 15 25 10
Stage II: with
anterior teeth
40 15 45 20

Conclusion
 Modern dental treatment is designed to focus on one
predominant goal: optimally maintainable oral health.
 Any factor that lessens the maintainability of any oral
tissue is a factor that must be isolated and corrected. To
do less is to fail the task entrusted to us.

 The broad aim of our work and the restoration of
function must always be kept in mind. Then only
can we estimate the value of the techniques
involved, espousing some methods and materials
and rejecting others.

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