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INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com
www.indiandentalacademy.com
INTRODUCTION
The term intrusion refers to the apical movement of
the geometric center of the Root (centroid) in respect to...
GRABER defined deep bite as “ A condition of excessive over
bite, where the vertical measurements between the maxillary
an...
Deep bite can be either skeletal or dentoalveolar
•Skeletal deep bite is due to
- upward rotation of mandible
- downward r...
Intrusion:
Absolute intrusion: where we intrude the incisors
keeping molars in place.
Relative intrusion: where we keep th...
In deep overbite cases correction of a bite occurs more
due to intrusion of lower anteriors rather than uppers. The reason...
It is logical to intrude the maxillary incisors to a significant
degree for many advantages are immediately gained:
1.Bite...
5. It will minimize the chances of moving the apices into juxta
position against the dense cortical bone.
6. The chances f...
Bite opening bends
Begg Technique is universally acknowledged for its efficient
bite opening mechanics, which is indeed on...
Anchor bends
First in the conventional begg’s , anchor bend is placed 3 mm
mesial to the molar tube in such a way that the...
Gable bend
This is a modified bite opening bend given in the arch
wire distal to the canine. This tends to cause extrusion...
Hocevar’s modification
In a modification given by Hocevar, bite opening bends are placed
on either side of canine, which r...
Mollenhauer’s
In a modification given by Mollenhauer, where a bite
opening curve is given, it will result in extrusion of ...
Kameda’s modification
In this modification both the anchor bends and gable
bends are given, there is extrusion of the cani...
Swain s modification
Swain advocates giving a mild gingival curve in the
anterior region which starts from mesial side of ...
Vertical step up bend
This intrusive action can be further augmented by
incorporating a vertical step up bend 3mm in heigh...
Even such a design may extrude the canine relative
to the lateral incisors. This is prevented by making the
cuspid circle ...
Class II Elastics
In the conventional beggs, the intrusive force from the
bite opening bends acts through the brackets whi...
This displacement is usually resisted by placing the
class II elastics thereby avoiding the labial tipping of the
anterior...
This problem gave rise to a modification of the force
delivery system where the proclination of the teeth is corrected
fir...
Power arms
This method is given by Dr. JYOTHENDRA KUMAR
The power arms are made from .017.025 or larger size wire.
The op...
The power arm moves the point of force application close to
the center of resistance (CR).
This produces near pure transla...
Palatal elastics from TPA:
This modification given by Dr. JAYADE
TPA is fitted only after the molar relationship is correc...
An additional oval shaped wire is soldered in the center, kept slightly
lower than the palate so that it rests on the dors...
High hat pins may be used in engaging elastics onto lateral
incisors. The force of palatal elastic not only neutralizes th...
Intrusion Utility Arch
This was devised by RICKETTS with the help of basic
biomechanical principles developed by BURSTONE....
Components
Molar section: This can have various bends for correction
of molar position.
Posterior vertical step: About 34...
Wire selection
Rectangular chrome cobalt alloy is much preferred as it can
be easily manipulated and loops can be formed w...
Fabrication
The intrusion arch is stepped gingivally at the molars, passes the
buccal vestibule and then it is stepped at ...
Retraction
Incisor retraction is achieved by bending down the end of
the molar segment gingivally. This helps in preventio...
Intrusion
Intrusion is achieved by placing an occlusally directed
Gable bend in the posterior portion of the vestibular se...
Three piece intrusion arch
This appliance was introduced by BURSTONE, modified by
SHROFF, LINDHAUER
Along with the intrusi...
This consists of
 A posterior anchorage unit, which is adapted into molars
and premolars
 An anterior segment with poste...
• The anterior segment is bent gingivally distal to the laterals
and then bent horizontally creating a step approximately ...
• Now the spring is activated by making a bend mesial to
helix and then sinched back and attached to the anterior
segment....
•Along with this an elastic chain can be attached from the hook of
the anterior segment to the molar tube to facilitate in...
Headgears
High pull headgears:
The effect on the dentition results on the location of center of
resistance relative to the...
Cervical pull headgears:
Here when the inner and outer bows are in same plane there
is clockwise rotation of both maxilla ...
Combination headgears:
In these cases also the resultant force vector which moves
through the center of resistance brings ...
The K. Sir (Kalra simultaneous Intrusion and
Retraction Springs)
This appliance was introduced by Dr Varun Kalra in the ye...
To obtain bodily movement and preventing tipping of teeth into
extraction space a 90o Vbend is placed at the level of eac...
A 60o V bend is located posterior to the center of inter bracket
distance produces an increased clockwise moment in the fi...
Then a 20o anti rotation bend is placed in the arch wire just distal
to the ‘U’ loop. This prevents the buccal segments fr...
Activation
Before the arch wire is used in the mouth, a trial activation
should be done out side the mouth this is done to...
After the TRIAL ACTIVATION, the neutral position of the loop
is determined by extending the mesial and distal edges of the...
Now the arch wire is inserted into the auxiliary tubes of
the molars and engaged into the 6 anterior teeth.
Then it is act...
When the loop is first activated, tipping movement generated
by the retraction force will be greater than opposing movemen...
Reverse Curve Nitinol Wire
When a reverse curve NiTi wire is in the molar tubes of the
lower arch, the anterior segment cu...
Removable appliances for Intrusion
Though these appliances do not fall under the exact classification of
Intrusive applian...
Anterior bite plane is the most commonly used removable
appliance for treatment of deep bite. It is a modified hawley’s
ap...
Functional Appliance
Activator: Selective trimming is done for the extrusion of molars
and intrusion of incisors.
Extrusio...
Magnetic Appliance
The Active vertical Corrector:
This was introduced by DELLINGER in 1986. This
consisted of upper and lo...
Seated Active Vertical Corrector (AVC).
www.indiandentalacademy.com
Magnetic Activator Device (MAD II)
This was developed in 1993 by DARENDILIER. These are
used for correction of open bite a...
This appliance by Kalra, Burstone, and Nanda increases the
interocclusal space and allows upward and forward autorotation ...
The Magnetic Twin Block Appliance:
The functions of twin block were made more accurate by
incorporation of magnets by cler...
Tip Back Springs: (Intrusion springs):
This was proposed by Burstone. These are made of 0.0170.025”
TMA wire. Prior to th...
This is defined as a pre calibrated spring to
produce the desired retraction, uprighting and
intrusion of the incisors. Th...
The point of force application is located at the first molar
tube in a suggested horizontal distance of 10mm posterior to ...
The wire has been made of 0.0160.022”S.S wire so as to make it
more rigid and to secure undisturbed structure of the acti...
The advantages of P.G. springs are
• The PG retraction spring can be used as a module for controlled
retraction of both ca...
It was believed that actual intrusion of incisors or molars are not
exactly possible and one that occurred for the correct...
www.indiandentalacademy.com
Thank you
For more details please visit
www.indiandentalacademy.com
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Intrusion mechanic and appliances /certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078

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Intrusion mechanic and appliances /certified fixed orthodontic courses by Indian dental academy

  1. 1. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. INTRODUCTION The term intrusion refers to the apical movement of the geometric center of the Root (centroid) in respect to the occlusal plane or plane based on long axis of a tooth. The intrusion mechanics is basically used in orthodontics in one specific condition- DEEP BITE www.indiandentalacademy.com
  3. 3. GRABER defined deep bite as “ A condition of excessive over bite, where the vertical measurements between the maxillary and mandibular incisal margins is excessive when the mandible is brought into habitual centric occlusion”. www.indiandentalacademy.com
  4. 4. Deep bite can be either skeletal or dentoalveolar •Skeletal deep bite is due to - upward rotation of mandible - downward rotation of maxilla - combination •Dentoalveolar deep bite is due to - overeruption of anteriors - infra occlusion of the molars - combination www.indiandentalacademy.com
  5. 5. Intrusion: Absolute intrusion: where we intrude the incisors keeping molars in place. Relative intrusion: where we keep the incisors from erupting further while growth provides vertical space into which the posteriors are erupted. www.indiandentalacademy.com
  6. 6. In deep overbite cases correction of a bite occurs more due to intrusion of lower anteriors rather than uppers. The reason for this may be the size of the tooth. It has been proved that light orthodontic forces, rather than causing any other type of tooth movement, causes intrusion of teeth rapidly When a tooth is intruded extremely light force of optimum range of 25gms is what is required, as the force is concentrated over a small area at the apex and produce appropriate pressure within the periodontal ligament during the process. www.indiandentalacademy.com
  7. 7. It is logical to intrude the maxillary incisors to a significant degree for many advantages are immediately gained: 1.Bite opening is attained by moving the maxillary incisors into the alveolus. 2. Potential for increasing a “gummy” smile is minimized. 3.The unfavorable tipping of the occlusal cant will not be as common. 4. There will be a reduction in the total amount of class II elastics that will be required www.indiandentalacademy.com
  8. 8. 5. It will minimize the chances of moving the apices into juxta position against the dense cortical bone. 6. The chances for root resorption are diminished 7. The need for lingualizing maxillary incisors will be lessened. 8.Torquing requirements will be reduced, and when needed will be accomplished within a more adequate anatomical area, and not restricted by the lingual cortical plate. 9. It will be easier to gain a class I relationship of the maxillary cuspids. www.indiandentalacademy.com
  9. 9. Bite opening bends Begg Technique is universally acknowledged for its efficient bite opening mechanics, which is indeed one of the strength of the technique. this is the procedure where there is incorporation of bends in the arch wire so that it helps in the intrusion of the anterior teeth and extrusion of the molars. Many authors have proposed different sites for the bite opening bends in the arch wire. www.indiandentalacademy.com
  10. 10. Anchor bends First in the conventional begg’s , anchor bend is placed 3 mm mesial to the molar tube in such a way that there is gingival displacement of the anterior part of the arch wire therefore when the arch wire is placed in the bracket, there is a intrusive force acting on the anterior segment. www.indiandentalacademy.com
  11. 11. Gable bend This is a modified bite opening bend given in the arch wire distal to the canine. This tends to cause extrusion of the canines and the intrusion of the central and laterals www.indiandentalacademy.com
  12. 12. Hocevar’s modification In a modification given by Hocevar, bite opening bends are placed on either side of canine, which results in more intrusion of central incisors and relative extrusion of lateral incisors and canine. www.indiandentalacademy.com
  13. 13. Mollenhauer’s In a modification given by Mollenhauer, where a bite opening curve is given, it will result in extrusion of the canine and intrusion of central and lateral incisors www.indiandentalacademy.com
  14. 14. Kameda’s modification In this modification both the anchor bends and gable bends are given, there is extrusion of the canine and intrusion of the incisors www.indiandentalacademy.com
  15. 15. Swain s modification Swain advocates giving a mild gingival curve in the anterior region which starts from mesial side of one canine to the mesial side of the other canine for the better intrusion of the anteriors. www.indiandentalacademy.com
  16. 16. Vertical step up bend This intrusive action can be further augmented by incorporating a vertical step up bend 3mm in height mesial to the molar tube. After giving this bend, anchor bend of required degree can be given in the upper end of the step up bend. www.indiandentalacademy.com
  17. 17. Even such a design may extrude the canine relative to the lateral incisors. This is prevented by making the cuspid circle in such a way that the posterior segment of the arch wire is kept gingival and the anterior segment is kept occlusal. www.indiandentalacademy.com
  18. 18. Class II Elastics In the conventional beggs, the intrusive force from the bite opening bends acts through the brackets which are placed in the labial aspect of the incisor crown. This results in the labial crown and the lingual root tipping. This displacement is generally undesirable except in case of class II div II cases where there is a lingually placed incisors. www.indiandentalacademy.com
  19. 19. This displacement is usually resisted by placing the class II elastics thereby avoiding the labial tipping of the anteriors. KESLING analyzed this use of class II elastics and found out that anchor bends produced around 45 grams of force and the class II elastics produced around 30 grams of force. Therefore the net resultant force was around 15 grams on each side this 15 grams spread over three teeth amounting about 5 grams on each tooth which was too little for active intrusion www.indiandentalacademy.com
  20. 20. This problem gave rise to a modification of the force delivery system where the proclination of the teeth is corrected first, then latter intrusive force are applied. So, initially the intrusive force through anchor bend should be given around 45 grams and class II force should be 60 grams. In this situation there is more of retractive force than the intrusive force. Later the intrusive force is increased to 60 grams and the class II decreased to 30 grams which will result in more intrusion. The increase in the force of intrusion is obtained by the increasing the degree of anchor bends gradually. Giving 30 degree bend initially and increasing to 50 degrees. The decrease in class II elastic force is done by placing the elastics for longer time i.e 3-5 days or by changing the elastics from yellow to road runner elastics www.indiandentalacademy.com
  21. 21. Power arms This method is given by Dr. JYOTHENDRA KUMAR The power arms are made from .017.025 or larger size wire. The optimal length of the power arms is about 57mm and follows the contour of the alveolus. The power arms are soldered to the bands, just above the molar tubes. www.indiandentalacademy.com
  22. 22. The power arm moves the point of force application close to the center of resistance (CR). This produces near pure translation, eliminating rotation and the undesirable moments incident to force application further away from the CR. In the present technique elastics are placed from the molar power arm posteriorly and on the intermaxillary circle anteriorly. This not only helps to avoid labial tipping of the anteriors , but also bring about effective intrusion www.indiandentalacademy.com
  23. 23. Palatal elastics from TPA: This modification given by Dr. JAYADE TPA is fitted only after the molar relationship is corrected, incisor proclination reduced and spacing closed. The TPA carries a hook that is bent into the TPA itself or soldered to it.the hook should lie in line with that of the lateral incisors. www.indiandentalacademy.com
  24. 24. An additional oval shaped wire is soldered in the center, kept slightly lower than the palate so that it rests on the dorsum of the tongue. This helps to generate a constant intrusive force on the entire assembly, which neutralizes the extrusive component of palatal elastics on molars. Four brackets are bonded onto the cingulum of incisors as gingivally as possible with bracket slot facing incisally. A plain 0.016 sectional wire, with ends bent is placed in palatal brackets. www.indiandentalacademy.com
  25. 25. High hat pins may be used in engaging elastics onto lateral incisors. The force of palatal elastic not only neutralizes the labially proclining component of archwire but also augments the intrusive force on incisors. The resultant force passes close to the center of resistance of the teeth and parallel to long axis of the tooth. www.indiandentalacademy.com
  26. 26. Intrusion Utility Arch This was devised by RICKETTS with the help of basic biomechanical principles developed by BURSTONE. This appliance consists of a continuous wire that extends across both buccal segments but engages only the first permanent molars and four incisors www.indiandentalacademy.com
  27. 27. Components Molar section: This can have various bends for correction of molar position. Posterior vertical step: About 34mm in height and position of vertical step varies depending on the type of utility arches The buccal bridges: Which should be contoured to prevent tissue irritation and sufficient expansion should be given in the wire on both sides. Anterior section which fits the bracket slot of incisors www.indiandentalacademy.com
  28. 28. Wire selection Rectangular chrome cobalt alloy is much preferred as it can be easily manipulated and loops can be formed with little difficulty For 0.018 slot – Mandible 0.016 X 0.022 or 0.016 X 0.016 Maxillary 0.016 X 0.022 For 0.022 slot - 0.019 X 0.019 for both the arches Rectangular wire is preferred to the round wire to control torque and to prevent the uncontrolled tipping www.indiandentalacademy.com
  29. 29. Fabrication The intrusion arch is stepped gingivally at the molars, passes the buccal vestibule and then it is stepped at the incisors to avoid distortion from the occlusal forces. There should be 5 mm distance between the anterior border of the auxiliary tube and posterior vertical segment. Activation Activation are of 2 types :- Retraction Intrusion www.indiandentalacademy.com
  30. 30. Retraction Incisor retraction is achieved by bending down the end of the molar segment gingivally. This helps in prevention of protrusion of lower incisors during intrusion. www.indiandentalacademy.com
  31. 31. Intrusion Intrusion is achieved by placing an occlusally directed Gable bend in the posterior portion of the vestibular segment. BENCH advocated giving a tip back bend in molar segment which will cause the incisal segment to lie in the vestibular sulcus. Intrusive force is created by placing the incisal segment into incisal brackets. But the draw back is that it may lead to the posterior tipping of the first molars. www.indiandentalacademy.com
  32. 32. Three piece intrusion arch This appliance was introduced by BURSTONE, modified by SHROFF, LINDHAUER Along with the intrusion of the anterior teeth it also helps in the retraction of the anteriors and thereby enhancing space closure www.indiandentalacademy.com
  33. 33. This consists of  A posterior anchorage unit, which is adapted into molars and premolars  An anterior segment with posterior extension, which runs through the four incisors and canine  Intrusion cantilever spring which is placed between the anterior and posterior segment. • After alignment of molars and premolars, the posterior segment made up of 0.017 X 0.025 SS is placed in right and left molars and premolars a TPA can also be given for more consolidation of posterior teeth. www.indiandentalacademy.com
  34. 34. • The anterior segment is bent gingivally distal to the laterals and then bent horizontally creating a step approximately 3mm. The distal part extends posteriorly to the distal end of canine bracket where it forms a hook. •Now the intrusion springs are fabricated. First the wire is bend gingivally, mesial to the molar tube helix is formed. On the mesial end of the spring, a hook is made through which it is attached to the anterior segment www.indiandentalacademy.com
  35. 35. • Now the spring is activated by making a bend mesial to helix and then sinched back and attached to the anterior segment. This will cause anterior intrusion and molar extrusion. www.indiandentalacademy.com
  36. 36. •Along with this an elastic chain can be attached from the hook of the anterior segment to the molar tube to facilitate intrusion along with retraction. www.indiandentalacademy.com
  37. 37. Headgears High pull headgears: The effect on the dentition results on the location of center of resistance relative to the line of action of force. •a) When the direction of pull is placed behind the center of resistance of the maxilla and maxillary dentition a clockwise rotation of maxilla and dentition is observed. Molars will show intrusion and incisors will extrude. Net effect is clockwise rotation of Occlusal plane. •b) When pull in front of center of resistance of both maxilla and the maxillary dentition, an anti clockwise rotation is observed. Molars tend to extrude and incisors intrude. Occlusal plane also rotates anti clockwise. Therefore bite opening is facilitated.www.indiandentalacademy.com
  38. 38. Cervical pull headgears: Here when the inner and outer bows are in same plane there is clockwise rotation of both maxilla and maxillary dentition. The incisors will move inferiorly to a greater extent than molar region. The Occlusal plane will also rotate in clockwise direction and bite will deepen up. But if the outer bow is bent upwards so that direction of traction is between the maxilla and maxillary dentition, maxilla will rotate clockwise and dentition in anticlockwise direction. Hence incisors will experience upward influence and molars a downward influence and bite will be opened up. www.indiandentalacademy.com
  39. 39. Combination headgears: In these cases also the resultant force vector which moves through the center of resistance brings about a more of distal movement of molars and a minimal amount of intrusion of the molars. The outer bow is angulated about 15o Headgears can be used in combination with other appliances or by itself to bring about active or absolute intrusion of the teeth. www.indiandentalacademy.com
  40. 40. The K. Sir (Kalra simultaneous Intrusion and Retraction Springs) This appliance was introduced by Dr Varun Kalra in the year 1998. This is a continuous 0.0190.025” TMA archwire with closed 7mm2mm U loops at the extraction sites. www.indiandentalacademy.com
  41. 41. To obtain bodily movement and preventing tipping of teeth into extraction space a 90o Vbend is placed at the level of each ‘U’ loop, this ‘V’ bend when placed between first molar & canine during space closure, creates two equal and opposite moments to counter the moments caused by the activation forces of closing loops. www.indiandentalacademy.com
  42. 42. A 60o V bend is located posterior to the center of inter bracket distance produces an increased clockwise moment in the first molar, which augments molar anchorage as well as intrusion of anterior teeth. www.indiandentalacademy.com
  43. 43. Then a 20o anti rotation bend is placed in the arch wire just distal to the ‘U’ loop. This prevents the buccal segments from rolling mesio-lingually due to the fore produced by loop activation. www.indiandentalacademy.com
  44. 44. Activation Before the arch wire is used in the mouth, a trial activation should be done out side the mouth this is done to reduce the stress build up from bending the wire and thus reduce the severity of the ‘V’ bends. www.indiandentalacademy.com
  45. 45. After the TRIAL ACTIVATION, the neutral position of the loop is determined by extending the mesial and distal edges of the ‘U’ loop. The neutral position is established when the ‘U’ loop is 3.5 mm wide. www.indiandentalacademy.com
  46. 46. Now the arch wire is inserted into the auxiliary tubes of the molars and engaged into the 6 anterior teeth. Then it is activated by 3 mm so that the mesial and distal ends of the loop is barely apart www.indiandentalacademy.com
  47. 47. When the loop is first activated, tipping movement generated by the retraction force will be greater than opposing movements produced by the V bends, which will lead to controlled tipping movements of the teeth into extraction sites. When the loop deactivates there will be more bodily movement and root movement of the teeth. Therefore the loop should be activated only after 6-8 weeks. It is usually placed for 4-5 months. www.indiandentalacademy.com
  48. 48. Reverse Curve Nitinol Wire When a reverse curve NiTi wire is in the molar tubes of the lower arch, the anterior segment curves gingivally. So when the anterior segment is forced occlusally into the bracket slot, it will result in the intrusive force on the incisors and extrusive force on the molars, therefore opening the bite DRAWBACKS: •Anterior flaring of the incisors •Anterior proclination cant be corrected •Space closure cannot be initiated www.indiandentalacademy.com
  49. 49. Removable appliances for Intrusion Though these appliances do not fall under the exact classification of Intrusive appliances. Many of the removable appliances we use in our day-to-day practice can be modified to bring about the intrusion of teeth to correct the vertical discrepancies. www.indiandentalacademy.com
  50. 50. Anterior bite plane is the most commonly used removable appliance for treatment of deep bite. It is a modified hawley’s appliance with a ledge of acrylic behind the upper incisors. The presence of acrylic will result in disoccluding the posterior teeth and thereby free to erupt. As the posterior teeth erupt the height of the bite plate is gradually increased. Bite Planes www.indiandentalacademy.com
  51. 51. Functional Appliance Activator: Selective trimming is done for the extrusion of molars and intrusion of incisors. Extrusion of the molars is achieved by loading acrylic in the lingual surface above the area of maximum convexity of the maxillary molars and below the area of maximum convexity of mandibular molars Intrusion of the incisors is done by loading of the acrylic in the incisal edge of the anterior teeth www.indiandentalacademy.com
  52. 52. Magnetic Appliance The Active vertical Corrector: This was introduced by DELLINGER in 1986. This consisted of upper and lower bite blocks with samarium cobalt magnets in stainless steel casesembedded in them. These helped in the intrusion of anteriors. www.indiandentalacademy.com
  53. 53. Seated Active Vertical Corrector (AVC). www.indiandentalacademy.com
  54. 54. Magnetic Activator Device (MAD II) This was developed in 1993 by DARENDILIER. These are used for correction of open bite and deep bite cases. They bring about intrusion by placing repelling magnets, which are placed opposing each other. In cases of class II mal occlusion with open bite, the posterior repelling magnets on maxillary plate, bring about expansion of maxillary arches and also the intrusion of molars. www.indiandentalacademy.com
  55. 55. This appliance by Kalra, Burstone, and Nanda increases the interocclusal space and allows upward and forward autorotation of the mandible, thereby decreasing lower facial height and facial convexity. This appliance resulted in intrusion of posterior teeth and an upward and forward autorotation of the mandible. www.indiandentalacademy.com
  56. 56. The Magnetic Twin Block Appliance: The functions of twin block were made more accurate by incorporation of magnets by clerk. He used samarium cobalt and neodymiumIronBoron in his well-accepted twin block. These magnets were embedded in the inclined surfaces of the twin block in repulsive mode. This reduced the need for any reactivation. www.indiandentalacademy.com
  57. 57. Tip Back Springs: (Intrusion springs): This was proposed by Burstone. These are made of 0.0170.025” TMA wire. Prior to this the U/L arches have to be leveled and aligned and preferably a rigid 0.0170.025” S.S. wire should be engaged in the bracket. These are indicated in patients requiring true intrusion of the incisors and can be used in the following conditions. Growing patients with forward growth rotations. For every deep curve of spee in lower arch. Cases of deep overbite due to extrusion of incisors. For steepened natural plane of occlusion. www.indiandentalacademy.com
  58. 58. This is defined as a pre calibrated spring to produce the desired retraction, uprighting and intrusion of the incisors. The segmentation requires formation of the active unit  anterior segment consisting of the four incisors whereas the two posterior segments include the buccal teeth of each side. Investigations have shown that center of resistance measures to be about 7mm distal and 9 to 10mm gingival to the center of lateral incisor bracket for the anterior unit. The posterior segments are connected by a TPA to form one rigid multirooted entity of the reactive unit. PG Retraction Spring (Poul Gjessing) www.indiandentalacademy.com
  59. 59. The point of force application is located at the first molar tube in a suggested horizontal distance of 10mm posterior to the center of resistance of the posterior segment. This can result in a moment of the extrusional force of 1020gm/mm=200gm/mm. The direction of this moment is opposite to moment of couple. The segmented arch offers freedom in selection of the points of force application relative to the center of resistance of anteriors and the posterior units or the retraction spring can be monitored to improve the desired movement of the active unit and reduce unwanted side effects in the reactive unit. www.indiandentalacademy.com
  60. 60. The wire has been made of 0.0160.022”S.S wire so as to make it more rigid and to secure undisturbed structure of the activated spring, stability in placement of the spring in the mucobuccal fold and resistance against masticatory functions. www.indiandentalacademy.com
  61. 61. The advantages of P.G. springs are • The PG retraction spring can be used as a module for controlled retraction of both canines and incisors. • The initial horizontal force of 100gm suggested for incisor retraction can be identified by the shape of the activated spring. • The incisor segments intrusion is induced with a magnitude of 10 to 25gm on each side. • Reduced moment to force ratio as a result of larger inter bracket distance. • Unwanted side effects on buccal segments are low. • Reactivation is done every 46 weeks. The treatment time is about 56 months. www.indiandentalacademy.com
  62. 62. It was believed that actual intrusion of incisors or molars are not exactly possible and one that occurred for the correction of some cases was relative intrusion. But over the years  advancements in orthodontic technique and appliances have proved that diagnosis, treatment planning and application of precise appliance system can bring about the true intrusion of anteriors and to some extend posterior units  with an application of optimum force. The final result with the use of an intrusive appliance lies in the hands of the orthodontist. Conclusion www.indiandentalacademy.com
  63. 63. www.indiandentalacademy.com Thank you For more details please visit www.indiandentalacademy.com

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