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Force of intrusion in orthodontics /certified fixed orthodontic courses by Indian dental academy
1. FORCE OF INTRUSION
INDIAN DENTAL ACADEMY
Leader in continuing dental education
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2. • INTRUSION?
Burstone (1977) - the apical movement of the
geometric center of the root (centroid) in respect
to the occlusal plane based on the long axis of the
tooth.
• DEEP OVERBITE?
The excessive vertical overlap of the upper
anterior teeth over the lower.
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3. • WHY DO WE INTRUDE?
- Cl-II and few Cl-I malocclusions manifest deepbite
- Causing an extrusion of upper anterior teeth
- Leading to a gummy smile
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5. PRINCIPLES FOR OBTAINING
INTRUSION
- Light and constant force
- Single point of force application
- Sequential intrusion
- Good control of anchorage
- Analysis of the forces and movements involved
in the different biomechanical situations
Burstone
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6. IDEAL FORCE REQUIREMENTS
FOR INTRUSION
- 50gms total against the central incisor
- 100gms(0.9n)against the incisal segment in the
maxillary arch.
Burstone
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7. • This study compares the forces exerted by the
various intrusive sectional arch’s on the upper
anterior teeth using different wires.
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8. AIMS OF THE STUDY
Comparison of stresses exerted by-Utility Arch - 0.016 x 0.022 Elgiloy.
-Utility Arch – 0.016 x 0.022 Stainless Steel.
-Burstone Intrusion Arch (with coil)
- 0.016 x 0.022 Stainless Steel.
-Burstone Intrusion Arch (with coil)
- 0.016 x 0.022 TMA.
-Connecticut Intrusion Arch - 0.016 x 0.022
Nickel Titanium.
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9. On the alveolar bone of maxillary incisor
segment of a human skull using ‘strain gauges’
•
To compare intrusive forces produced by the
same arch wires using an instron machine.
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10. REVIEW LITERATURE
• ROBERT RICKETS (1950) - Rickets step down
base arch.
• CHARLES.R.BURSTONE (1977) - Intrusive arch
for placement in the central incisors or four
incisors.
• MARC.M.VANDERBULCKE et al (1986) - Center
of resistance
• JAMES.A.McNAMARA (1986) - The utility arch
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11. •
BHAVANA SHROFF et al (1995) - Appliance
for simultaneous intrusion and retraction of
upper anterior teeth.
•
VARUN KALRA (1998) - K-SIR Arch.
•
RAVINDRA NANDA et al (1998) - Connecticut
intrusion Arch.
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12. MATERIALS AND METHODS
• Human skull with all well aligned maxillary
teeth and good bone support.
• Fitted with a 0.018 slot preadjusted edgewise
bracket of roth prescription.
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15. WIRE AND ARCH WIRE FORMS
Burstone Intrusion Arch
0.016”X0.022” TMA
Utility Arch
0.016” X 0.022” SS
Utility Arch
0.016” X 0.022” Elgiloy
Burstone Intrusion Arch
0.016” X 0.022” SS
Connecticut Intrusion Arch
0.016” X 0.022” Nickel Titanium
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16. • The template was made
- Pressing a softened sheet of wax onto the test
jaw containing the full complement of teeth
therefore creating indentations on the wax
sheet.
- The wax was cut and the arch form transferred
to a template
- All the arch forms were then made around this
template.
- The connecticut arch was preformed and its
length adjusted and modified accordingly.
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17. THE TESTING SYSTEM
Two systems were employed
1.Strain gauge
2.Instron testing machine
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19. STRAIN GAUGE
-1mm strain gauge made of 45% nickel and
55% copper
-Fixed on to the alveolar bone of each maxillary
incisor at its approximate centroid
-Strain gauge connected to strain indicator using
an electrical wire.
-Wheatstone bridge circuit to measure the
strains.
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20. -Burstone and connecticut arches placed piggy
back on the base arch wire and secured.
-Strain meter ensured to check zero before each
reading
-Procedure repeated for each tooth.
-Utility arch was tied directly onto the anterior
brackets and readings recorded similarly
• Five arch wires in each sample was tested and
the result was calculated
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21. • Testing method
-The Youngs modulus = stress/strain
-The Youngs modulus of alveolar bone
= 1.4 x (10)3 kg/mm2
-Therefore 1.4 x (10)3 kg/mm2 = stress/strain
- strain = value obtained from the strain
indicator for individual teeth when intrusive
arch was engaged.
- stress was calculated subsequently substituting
the values.
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22. • Instron machine(model no.4204)
- subjected intrusion arch inserted into the
molar tubes accordingly
-incisor brackets detached to avoid interference
-levels of slots marked
-skull positioned to in the desired manner
-instron crosshead speed set at 2cm/min or
20mm/min
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23. -A 1mm stainless steel hook for pulling the arch
wire secured to the instron
-Wire was pulled till level marked at incisors
-Five different readings recorded for each
intrusion arch.
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26. STRESS VALUES EXERTED BY
DIFFERENT ARCHES ON THE
ALVEOLAR BONE OF THE
INCISOR SEGMENT IN GMS/MM2
GROUP
VALUES
GROUP-1
CONNECTICUT
INTRUSION ARCHNICKEL TITANIUM
56.12
58.04
60.00
51.40
54.28
GROUP-2
BURSTONE INTRUSION
ARCH-TMA
78.40
73.60
80.84
75.54
78.40
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30. • The analysis used for statistically evaluating
the five sets of arch wires were– THE STUDENTS ‘T’ TEST
– THE ANOVA ANALYSIS
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31. RESULTS
Arch forms that showed force in descending order:
1- UTILITY ARCH
- Elgiloy (group 5)
2- UTILITY ARCH
- Stainless steel(group 4)
3- BURSTONE INTRUSION ARCH
- Stainless steel (group 3)
4- BURSTONE INTRUSION ARCH
- TMA (group 2)
5- CONNECTICUT INTRUSION ARCH
- NiTi (group 1)
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32. STRESS VALUES EXERTED BY DIFFERENT
ARCHES ON THE ALVEOLAR BONE
0 – CONNECTICUT INTRUSION ARCH
0 - BURSTONE INTRUSION ARCH – SS
0 – UTILITY ARCH – ELGILOY
0 – BURSTONE INTRUSION ARCH – TMA
0 – UTILITY ARCH - SS
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33. INTRUSIVE FORCES EXERTED BY
DIFFERENT ARCHES
0 – CONNECTICUT INTRUSION ARCH
0 - BURSTONE INTRUSION ARCH – SS
0 – UTILITY ARCH – ELGILOY
0 – BURSTONE INTRUSION ARCH – TMA
0 – UTILITY ARCH - SS
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34. CONCLUSION
• From this study it is concluded that by listing
the force delivered by various intrusive arches ,
it is in the hands of the orthodontist to select
the ideal intrusive arch depending on the needs
of individual case and use his or her knowledge
of bio-mechanics to get the best of results.
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