ORTHODONTIC INTRUSION

1. Intrusion
PREBERD BY
ABDULQ AWI ABDULGHANI
ALHADDAD ABDULSALAM
ABDALWAHAB
PRESENTED TO
Dr. Laraine Rowena L. Andrada

2. Introduction
Intrusion refers to the apical movement of the geometric center of the root (centroid) in respect to the occlusal plane
or plane based on the long axis of the tooth. Burstone
Marcotte defines intrusion as the” tooth movement that occurs in an axial (apical) direction and whose center of
rotation lies at infinity. It is an axial type of translation”
Nicolai as “ translational form of tooth movement directed apically and parallel to the long axis”

3. Correction of the deep overbite can be accomplished in a number of ways depending on the initial
diagnosis and treatment objectives.
Deep bite can be corrected by various tooth movements which include:
 Extrusion of posterior teeth
 Up righting of posterior teeth
 Increasing the inclination of incisors
 Intrusion of anterior teeth
 Combination of one or two of the above tooth movements
Intrusion of anterior teeth to correct deep overbite may be indicated in patients with unaesthetic
excessive maxillary incisor showing at rest position of the lip (5-8mm)

4. Pseudo intrusion refer to the labial tipping of the incisor around the centroid.
Relative intrusion – Deep bite correction by extrusion of posterior teeth rather than
true intrusion of the anterior teeth

5. True intrusion is obtained by applying a single intrusive
force through the center of resistance of the anterior
teeth.
The precise selection of the point of application of the
intrusive force with respect to the axial inclination of the
incisors is critical and will define the type of tooth
movement
If the incisors are flared and the intrusive force is
applied anterior to the Cres further flaring occurs so to
prevent this force should be applied distally in order to
direct the force passes through the Cres
Biomechanics In Intrusion

7. Major Principles Of Intrusion
Six major principle of intrusion should be followed;
if genuine intrusion and greater control of force system is needed:
1. Controlling force magnitude and constancy.
2. Anterior single point contacts.
3. Point of force application.
4. Selective intrusion.
5. Control of reactive units.
6. Avoiding extrusive mechanics.

8. In order to maintain a constant force during intrusion, wire
with a low load deflection rate should be used.
If a high load deflection spring is used for intrusion as
teeth moves, a rapid drop in force magnitude occurs, so
that optimal force may be only momentarily reached.

9. POINT OF FORCE APPLICATION
Passing through center of resistance Intrusion of incisor segment
Passing labial to the center of resistance Flares the crown more labially

10. SELECTIVE INTRUSION
Leveling with a continuous arch or with a sectional wire can
produce undesirable side effects. Many times the overbite is
corrected not because of intrusion but by extrusion.

11. Control Of The Reactive Unit
Two basic side effects should be anticipated from intrusive mechanics
 From the lateral view a moment is created which tends to alter the plane of occlusion of the
buccal segment and therefore in the upper arch, the plane is steepened.
1.The force are kept as low as possible
2.Teeth in the buccal segment are rigidly connected and the right and the left buccal stabilizing
segment are connected
3.So add more teeth for anchorage
4.Do as much retraction as possible to decrease the length of moment arm

12. . Second major side effect produced by an intrusive arch can be seen
from the frontal view with an intrusive force acting on the incisors, there is
an equal and opposite extrusive force acting at the molars.
 since the extrusive force is acting buccally at the tube, a moment is
created that tends to tip the crowns lingually and roots buccally.
One of the functions of the lingual arch is to resist side effects

13. It is wise to intrude the maxillary incisors to a significant degree prior to any retraction:
1. Bite opening is achieved by moving maxillary incisors into the alveolus.
2. The potential for increasing a gummy smile is minimized.
3. The unfavorable tipping of the occlusal cant will not be as common.
4. It will minimize the chances of moving the apices into the dense cortical bone.
5. There will be a reduction in the total amount of class II elastics that will be required.
6. The torquing requirements will be reduced.

14. Intrusion Force

15. Proffit suggested 10-20 grams of force needed for intrusion.
Bench, Gugino and Hilgers in 1978, advocated intrusive force of
15 to 20 grams per lower incisor and 60 to 80 grams for all four
lower incisors.
Lui and Herschelb in 1981 suggested use of 80 to 100 grams of
force for four incisors intrusion.
Though there has been many opinions regarding an ideal force
for intrusion, all recognize the need for light continuous force

16. Appliance for intrusion
The extraoral traction force can be attached anteriorly by means of j hook to the arch wire
or to a hook soldered to the arch wire.
J –hook can be applied to the maxillary teeth to retract and intrude the maxillary incisor
teeth.
The line of force passing mesial and apical to the center of resistance causes intrusion and
distalize upper incisors.
Head Gear + Maxillary intrusion splint = For whole Arch Intrusion.
J Hook Head Gear

17. ANCHORAGE BENDS / TIP BACK BENDS
Placed immediately posterior to the 2nd premolar bracket
• Bent so that when inserted into the buccal tubes the anterior section of the arch wire lies in the
buccal sulci Causes intrusion of anteriors.

18. GABLE BEND
Modified bite opening bend given in the arch wire distal to the canine
This tends to cause relative extrusion of canines and intrusion of central and laterals

19. Given by Richard A. Hocevar,
Bite opening bends are placed on either side of the
canines, which results in more intrusion of central incisors
and relative extrusion of laterals and canines
Hocevara’s Intrusion Bend
Reverse curve of spee correct the deep bite by extrusion of the
posteriors and intrusion and flaring of the anteriors
BITE OPENING CURVES

20. Intrusion Arches
Intrusion can be accomplished in two ways with intrusion arches.
1. With continuous arch wire that by passes the premolars and canine teeth.
2. With segmented base arch wire.
So that there is no connection along the arch between the anterior and posterior segments and an
auxiliary depressing arch.

21. 1. Ricket’s Utility Arch
2. Tip back Springs ( Intrusion Springs)
3. Burstone’s Continuous Intrusion Arch.
4. Burstone’s Three Piece Intrusion Arch
5. K-Sir (Kalra Simultaneous Intrusion And Retraction)
6. Connecticut Intrusion Arch
7. PG Retraction Spring
8. Translation Arch
9. Lingual Arch For Intruding And Up righting Lower Incisors

22. https://youtu.be/PEKSrStDXig

23. BIO – MECHANICS OF INTRUSION ARCHES
One couple systems
The end that is tied as a point contact
• The end which is engaged in the bracket slot a force and a couple •
1-couple system couple is generated only at the site of full
engagement
It is statically determinate magnitudes of the forces and moments
produced can be determined clinically after the appliance is inserted
into the bracket.
 Two couple systems
Both the ends of the wire is engaged into brackets
Magnitudes of the forces and moments produced can
not be determined clinically after the appliance is
inserted into the bracket.
• Because of the inability to measure force systems
produced by 2-couple appliances clinically, they are
referred to as being statically indeterminate

24. The basic mechanism for intrusion consists of three parts:
1. The posterior anchorage unit.
2. The anterior segment.
3. The intrusion arch itself.

25. Three-piece Intrusion Arch
Consists of
 Posterior anchorage segment
 Anterior segment with posterior extension
 Intrusive cantilevers
Sometimes chain elastics

26. Biomechanics
Intrusive force through Cres will intrude incisor along line of action of this force.
An intrusive force perpendicular to the distal extension and through Cres will have the same
effect.

27. To obtain a line of action of the intrusive force through the center of
resistance and parallel to the long axis of the incisors, the point of force
application must be more anterior and a small distal force should be given
If the intrusive force is placed farther distally and an appropriate small distal
force is applied, intrusion and simultaneous retraction of the anterior teeth
occurs because of the tip back (clockwise) moment created around the center
of resistance of the anterior segment consisting of four incisors.

28. Temporary Anchorage Devices
Factors to consider when placing mini-implants includes
1. Sufficient interdental bone
2. Less soft tissue irritation
3. Larger anterior segment
According to Nanda the ideal location for placement of TADS for anterior intrusion is between the roots of
the canine and lateral incisors
The selection of the point of application of intrusive force with respect to Cres of the anterior segment
Anterior intrusion with TADS

29. The Cres of the six anterior teeth is estimated to be halfway between the Cres of the four incisors and
canine
A light distal force was delivered by an E-chain to the anterior segment to alter the direction of the
intrusive force , so that true intrusion of the anterior teeth could be achieved on their long axis

30. BIOMECHANICS FOR MOLAR INTRUSION
Some of the common indications for molar intrusion are
1. Increased anterior facial height
2. To initiate auto-rotation
3. Prosthetic purpose : making space for prosthesis Increasing the interdental height.

31. INTRUSION OF SINGLE MOLAR
• Force should be balanced Bucco-lingually and mesio-distally for pure
intrusion.
• Line of force should pass through the cres of molar :
• Centre of occlusal table
• Near the furcation area
• Closer to the palatal root of maxillary molar.
• Recommended insertion site of minis crews :
• Buccal surface – mesial interdental area
• Palatially – distal interdental area

32. Additional minis crews can be placed on either side of the alveolar slope to adjust the force
direction.
• Three or four minis crews are useful to prevent or correct the tipping of severely extruded
molars.

33. INTRUSION OF MOLARS ON BOTH SIDES
Symmetrical intrusion – intrusive force delivered through trans palatal bar connecting both molars Control of palatal tipping :
1. Expansion of TPA
2. Additional minis crews on buccal side Control of mesio-distal tipping ( sagittal direction) Minis crew should be inserted on
the line connecting the central fossa of both molars

34. Intrusion of maxillary molars
 Engagement of rigid rectangular wire in buccal side
 Y- Plates are placed at the Zygomatic buttress.
 TPA in the palatal side – to prevent buccal tipping of the posteriors
 Magnitude of intrusive force : 400 g / side

35. Intrusion of maxillary molars
When maxillary molars are intruded at the same
level as anteriors , anterior segment is included
with a continuous arch wire .
Simultaneously, arch wire is ligated to the miniplates to
intrude/ maintain their exact position for few months.

36. Intrusion Of Mandibular Molars
•Anterior open bite with increased mandibular posterior height
•L- plates placed at the molar region of the mandibular body.
•Intrusive force of 400-500 gms/side
•Lingual arch and lingual torque is given in the rectangular wire to prevent buccal flaring

39. REFERENCES
Contemporary orthodontics- Proffit •
Orthodontics-current principles and techniques- Graber , Vanarsdall, Vig
• Charles J. Burstone “ Biomechanics of deep overbite correction” semin orthod 2001: 7: 26-33
• Bhavana Shroff, Steven J Lindauer , Charles J Burstone “ Segmented approach to simultaneous intrusion and
space closure: biomechanics of three piece base arch appliance” Am J Orthod dentofac Orthop 1995:107: 136-43.
• Richard J. Smith, Charles J. Burstone, “ Mechanics of tooth movement” vol 85, 294-307
• McNamara JA Jr. Utility arches. J clin orthod 1986;20:p.452-456.
• Martina R. Paduano S. The Translation Arch. J Clin Orthod. 1997;3;11:p.750-753
• Nanda, R. and Uribe, F.A., 2009. Temporary Anchorage D

40. Thank you