Intrusion in orthodontics

• 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.
www.indiandentalacademy.com

• 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

GUMMY SMILE IDEAL SMILE LINE
CORRECT INCISOR RELATION INCREASED OVERBITE

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

IDEAL FORCE REQUIREMENTS
FOR INTRUSION
- 50gms total against the central incisor
- 100gms(0.9n)against the incisal segment in the
maxillary arch.
Burstone

• This study compares the forces exerted by the
various intrusive sectional arch’s on the upper
anterior teeth using different wires.

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.

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.

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

• 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.

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.

ARMAMENTARIUM

WIRES AND ARCH WIRE FORMS
INTRUSIVE
ARCHES
ARCH WIRE
MATERIAL
COMPANY
Burstone
intrusion arch
Stainless steel Straight length-unitek
Burstone
intrusion arch
TMA Straight length-ormco
Utility arch Elgiloy Straight length-american
orthodontics
Utility arch Stainless steel Straight length-unitek
Connecticut
intrusion arch
Nickel titanium Preformed-ortho
organizers

WIRE AND ARCH WIRE FORMS
Burstone Intrusion Arch
0.016”X0.022” TMA
Burstone Intrusion Arch
0.016” X 0.022” SS
Utility Arch
0.016” X 0.022” Elgiloy
Utility Arch
0.016” X 0.022” SS
Connecticut Intrusion Arch
0.016” X 0.022” Nickel Titanium

• 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.

THE TESTING SYSTEM
Two systems were employed
1.Strain gauge
2.Instron testing machine

STRAIN INDICATOR
DIGITAL DISPLAY
INSTRON MACHINE

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.

-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

• 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. www.indiandentalacademy.com

• 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

-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.

STRAIN GAUGE IN
POSITION
STUDY SET-UP

INTRUSIVE FORCES BEING MEASURED USING
INSTRONwww.indiandentalacademy.com

STRESS VALUES EXERTED BY
DIFFERENT ARCHES ON THE
ALVEOLAR BONE OF THE
INCISOR SEGMENT IN GMS/MM2
GROUP VALUES
GROUP-1
CONNECTICUT
INTRUSION ARCH-
NICKEL 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

GROUP-3
BURSTONE INTRUSION
ARCH- STAINLESS STEEL
87.52
90.10
92.24
92.10
85.54
GROUP-4
UTILITY ACH-STAINLESS
STEEL
123.2
126.6
123.2
128.4
130.42
GROUP5
UTILITY ARCH-
ELGILOY
150.08
153.8
156.8
153.8
150.08

INTRUSIVE FORCES EXERTED BY
DIFFERENT INTRUSIVE ARCHES
EVALUATED USING A INSTRON
MACHINE
GROUP VALUES
GROUP-1
CONNECTICUT
INTRUSION ARSH-
NICKEL TITANIUM
35.12
34.96
34.95
34.96
35.00
GROUP-2
BURSTONE INTRUSION
ARCH-TMA
59.20
59.45
59.50
59.35
59.50

GROUP-3
BURSTONE INTRUSION
ARCH-STAINLESS STEEL
79.91
80.01
79.35
79.61
80.23
GROUP-4
UTILITY ARCH-STAILESS
STEEL
110.00
110.01
110.10
109.90
110.10
GROUP-5
UTILITY ARCH-ELGILOY
126.10
126.20
125.90
125.80
126.10

• The analysis used for statistically evaluating
the five sets of arch wires were-
– THE STUDENTS ‘T’ TEST
– THE ANOVA ANALYSIS

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)www.indiandentalacademy.com

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

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

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.

Intrusion in orthodontics

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