HEADGEARS
www.indiandentalacademy.com
INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
www.indiandentalacademy.com
Definition: A class of appliances characterised by the extroral positions of activating elements and supporting structure and having remotely located responsive force.
www.indiandentalacademy.com
History:
More than 100 years ago Kingsley is reported to have used occipital anchorage during treatment. In 1907, Angle referred to extraoral anchorage and illustrated his occipital headgear and traction bar, which he replaced with “Baker’s anchorage”. In seventh edition of his text, Angle described the use of extroral traction combined with extraction of upper premolars. www.indiandentalacademy.com
Kingsley’s headgear
Angle’s headgear
www.indiandentalacademy.com

According to Breitner, in 1911 Oppenheim introduced the concept of center of rotation of a tooth as the point around which a tooth would rotate when a force was applied to the crown. Oppenheim also recognised that if a force could be arranged so that it passed through the center of rotation then a tooth, such as a molar would move bodily. www.indiandentalacademy.com
Since such bodily movement does not involve tipping or rotation, the focal point for the force to produce the translatory movement has become known as the center of resistance. Kloehn took up the use of extraoral traction following a publication by oppenheim in 1936 and must be given the credit for use of cervical traction as 1st phase in 2 phase treatment of class II and maxillary anterior crowding. Phase I was concerned with distalising the maxillary I permanent molar before pubertal growth spurt. www.indiandentalacademy.com
Kloehn – type headgear
To translate molar distally, Kloehn advocated alternately tipping the molar crowns and roots. Distal crown tipping was produced by positioning the outer bow of the face bow below the center of resistance and distal root tipping by positioning the ends of the bow above the center of resistance. Weber showed examples of extraoral traction designed to distalise mandibular teeth. www.indiandentalacademy.com


Appliances resembling chin cups have been in use since the early 1800's. According to Graber, the early attempts with the chin cup were not successful because of incomplete knowledge of mandibular and facial growth, its use on nongrowing patients, and an inadequate understanding of the forces generated by the chin cup. Armstrong applied 500 Gm. of force via chin cups on 100 adolescent patients with mandibular prognathism. He reported that half of his patients showed improvement in the Class III profile, whereas none of the control, nontreated patients showed any favorable change. www.indiandentalacademy.com

Thilander treated sixty patients with chin cups for 1 to 6 years. A significant percentage of patients did not improve. The patients who showed improvement were comparatively young and showed favorable dental changes. The force generated by the chin cup in his study was only 150 to 200 Gm.

Graber, Chung, and Aoba reported results in patients treated with chin cups for 12 to 14 hours each day with a force of 1.5 to 2 pounds on each side. They showed that mandibular growth could be redirected with a chin cup. They asserted that continuous use of the appliance for a long period or through active growth www.indiandentalacademy.com was necessary to achieve stable results .

Graber treated 35 Class III malocclusions in children between the ages of 5 and 8 years with chin cup therapy for 3 years. He found that the therapy was particularly effective in patients with increased vertical growth of the face.

Several clinical studies in the past have noted that treatment of patients in skeletal Class III should include protraction of the maxilla with or without chin cups. Oppenheim suggested a technique for moving the maxilla forward. He noted that restriction of growth or distal movement of the mandible was impossible. www.indiandentalacademy.com
Kettle and Burhapp reported an appliance for cleft lip and palate which successfully inhibited forward growth of the mandible and simultaneously caused anterior movement of the maxilla.
Nelson described an appliance which used anterior pull on the maxilla by means of a football-type helmet. Haas showed downward and forward movement of the maxilla as a result of palatal expansion. The maxillary effect was enhanced by the use of Class III elastics from a chin cup to the distal aspect of the palatal appliance.
Delaire, Verdon, and Floor have extensively used a facial mask to protract the maxilla anteriorly. Elastics generating forces of 1,000 to 2,000 Gm. are used from distal of the maxillary molars to the wires of the mask to move the maxilla anteriorly. www.indiandentalacademy.com
Types Of Headgear 1)
According to the means of attachment to teeth Using face - bow, which slots into tubes soldered onto the bridge of a removable appliance crib or tubes which form an integral part of a band attachment or tubes which are incorporated in the design of a functional appliance. The face – bow is an inner – outer bow. Inner bow is available either in 0.045” or 0.51” depending on the size of headgear tube. Outer bow is usually 0.072” www.indiandentalacademy.com
2) J – hooks which can be directly attached onto the arch wire in a fixed appliance or attached to hooks soldered onto the labial bow of a removable appliance.
 1) 2)
According to force element Elastic strap or elastic bands Spring loaded
www.indiandentalacademy.com

According to direction of pull
a)
Cervical pull Straight pull High pull (Occipital) Reverse Pull or protraction headgear Combination headgear Interlandi which gives more options for force direction. Chin cup -- occipital and vertical
b) c) d) e) f) g)
www.indiandentalacademy.com
High Pull
Cervical pull
Combination pull
www.indiandentalacademy.com
BIOMECHANICAL CONSIDERATIONS
Mechanics describes the effects of forces on bodies and can be generally divided into three areas: 1) statics 2) Kinetics 3) strength of materials. Statics describes the effects of forces on bodies that are at rest or have a constant velocity. Force is action of one body on another body that tends to change or changes the shape of that second body. A force is equal to mass times acceleration (F = ma). Unit is Newton or gram. Millisecond/s^2. Grams are substituted for Newton in clinical orthodontics because the contribution of acceleration to the magnitude of force is clinically irrelevant. www.indiandentalacademy.com
A force is a vector and is defined by the characteristics of vectors, which have magnitude and direction. Magnitude of vectors represent its size. Direction is described by the vector’s line of action and point of origin. The sum of two or more vectors is called resultant. Clinically, the determination of horizontal , vertical and transverse components of a force improves the understanding of the direction of tooth movement that might be expected. www.indiandentalacademy.com
Center of resistance
A free body can be considered to have a single point within it where all of its mass is centered. The center of mass is the point through which an applied force must pass for a free object to move linearly without any rotation. Tooth is restrained body in which this center of mass is called center of resistance. It can be described in each plane of space. Single tooth, units of teeth, complete dental arches and the jaws themselves each have center of resistance. In other words the center of resistance is the point on the body where a single force would produce translation i.e ., all points moving in parallel, straight lines www.indiandentalacademy.com
The center of resistance of a tooth is dependent on the root length and morphology, the number of roots, and the level of alveolar bone support. The exact location of the center of resistance is not easily identified. Analytical studies have determined that the center of resistance for single rooted tooth with normal alveolar bone levels is about one fourth to one third the distance from the cementoenamel junction to the root apex. Miki and Hirato found that the location of the center of resistance of the midface of the human skull was between the first and second upper premolars anteroposteriorly, and between the lower margin of orbitale and distal apex of the first molar vertically in the sagittal plane. It is distal to the lateral incisor roots for intrusive movements of www.indiandentalacademy.com maxillary anterior teeth.


1. 2. 3. 4.
In maxillary first molar the center of resistance is estimated to be in the middle third of the root near the junction of cervical third or approximately at the trifurcation of the roots. The center of resistance should not be regarded as a fixed point within a tooth, but rather as the composite point of all factors, offering different components of resistance to a certain force application. The tooth anatomy and mass distribution within the tooth The structure of the periodontal attachment The degree of bony surroundings The adjacent teeth. www.indiandentalacademy.com
Center of resistance of maxilla
www.indiandentalacademy.com



The point of application of a force is simply the point of contact between the body being moved and the applied force. Direction is indicated by the body of the arrow itself and the arrowhead. Without the head of the arrow, the body alone indicates the line of action. The sense is determined by which end we put the arrowhead on. Since the movement of a tooth (or any object) is determined by the net effect of all forces on it, it is necessary to combine applied forces to determine a single net force, or resultant. www.indiandentalacademy.com
 
There may be a force on a tooth that we wish to break up into components. For example, a cervical headgear to maxillary molars will move the molars in both the occlusal and distal directions. It may be useful to resolve the headgear force into the components that are parallel and perpendicular to the occlusal plane, in order to determine the magnitude of force in each of these directions. www.indiandentalacademy.com
Center of rotation
The center of rotation of a body is a point around which the body will rotate or tip. The center of rotation can be changed, being dependent on external force application. When a force is applied to a tooth and its line of action does not pass through center of rotation, then tipping will occur around a center of rotation which may be located anywhere between the center of resistance of the tooth and infinity. www.indiandentalacademy.com
Resolving a force into components It is often useful to divide a single force into components at right angles to each other. Usually, the objective is to determine how much force is being delivered perpendicular and parallel to the occlusal plane, Frankfort horizontal, or the long axis of the tooth.
www.indiandentalacademy.com
Moment of force
Forces not acting through the center of resistance do not solely produce linear motion. The moment of force results in some rotational movement. The moment of force is the tendency for a force to produce rotation. It is unrecognized in clinical orthodontics. Awareness of moment of force is required to develop effective and efficient appliance designs. Two variables determine the moment of force – the magnitude of the force and the distance. Either one can be manipulated by the clinician to achieve the desired force systems. www.indiandentalacademy.com
Moment of a couple  

This is another method of achieving rotational movements. A couple is two parallel forces of equal magnitude acting in opposite directions and separated by a distance. Direction is determined by following the direction of either force around the center of resistance to the origin of opposite force. www.indiandentalacademy.com
BIOMECHANICS OF HEADGEAR
Understanding how to control the direction and magnitude of the forces produced by various headgear designs is paramount in achieving desirable clinical results. Decreasing the patient's length of treatment and improving the treatment results would be only two of the benefits derived from applying well-planned force systems. A method of analyzing force systems produced in the anterior-posterior and vertical planes will aid the clinician. www.indiandentalacademy.com
In 1971 Armstrong demonstrated the importance of the precise control of magnitude, direction, and duration of extraoral force to increase its efficiency and effectiveness in treating malocclusions in the late mixed dentition. Gould has shown how changes in the inclination of the facebow affect the direction of the force and ultimately the direction of tooth movement. Greenspan presented reference charts elaborating the different moments and forces produced with the various headgear designs. www.indiandentalacademy.com
Moments (M) and forces produced by force vectors applied at varying positions relative to the center of resistance (CR) of a constrained body in this case the maxillary 1st molar. The vertical (V} and horizontal (H) forces are proportional in magnitude to the legs of the triangle that is constructed . In (a) the vertical and horizontal components of the force are approximately equal. The moment's direction is counterclockwise since the line of force is above CR. The magnitude of M is the product of LF times the perpendicular distance (identified as P)from LF to CR. LF goes through CR in (b) thus there is no M produced. The tooth will translate parallel to the line of force. The posterior force component is larger than the superior. The LF in (c) will produce a posterior and interior movement. The moment (P x LF) is below CRwww.indiandentalacademy.com and is therefore clockwise.



The magnitude of the moment produced by the headgear is calculated by multiplying the perpendicular distance (P) from the LF to the CR by the magnitude of the force. Thus, for a given force, the greater the distance from the CR that the force is applied, the greater will be the moment. A comprehensive understanding of the potential, limitations, and undesirable side-effects can be gained by understanding the mechanical principles involved in its application. We can now apply our basic principles to assess force systems applied by various headgear designs. www.indiandentalacademy.com
Cervical Headgear
The cervical (Kloehn) headgear is a device that many orthodontists have used routinely in the great majority of their headgear cases. It is composed of three basic parts: (1) molar bands and tubes, (2) inner bow and outer bow soldered together near the middle of the two bows, and (3) a neckstrap that is placed around the back of the neck to provide traction. This extraoral pull is generally applied bilaterally, for three main purposes: (1) as a restraining force, (2) as a retracting force, or (3) as a supplementary force. www.indiandentalacademy.com
The cervical headgear is applied in early treatment of Class II malocclusion to inhibit forward displacement of the maxilla or maxillary teeth, while the rest of the dentofacial structures continue their normal growth. As demonstrated by Oppenheim, this can cause a change in the intermaxillary relationship from Class II to Class I. Perhaps the change in molar relationship is due not so much to the distal force, but to the clockwise moment that very effectively tips the molar crown distally. www.indiandentalacademy.com
The main disadvantage to the use of the cervical headgear is that it normally will cause extrusion of the upper molars. This movement is seldom desirable except in treatment of patients with short lower facial heights. These patients, it should be remembered, are few and far between. The decision to treat with cervical headgear needs to be based on a complete understanding of the desired tooth movement and the force system that is produced with this headgear style. www.indiandentalacademy.com
Force systems with cervical headgear. OB (Outer bow)-A lies along the LFO and therefore only vertical and horizontal forces will be produced no M. The position of OB-B will produce an extrusive F posterior F and counterclockwise M since it is above CR. Outer bows located below the LFO will produce posterior forces and smaller extrusive forces since they are closer vertically to the neckstrap and clockwise moments. www.indiandentalacademy.com


The different moments and forces produced by the cervical headgear depend on the situation of the outer bow in relation to the LFO. By definition, when the outer bow lies along the LFO, no moment occurs, and the force system will be reduced to a bodily movement in a posterior and extrusive direction. If the outer bow is placed above this line (angle of above 20- 30 degree above occlusal plane), the moment produced by the force will be in a counterclockwise direction. On the other hand, if the outer bow is adjusted below this line the moment created will be clockwise. However, the direction of the forces are the same extrusive and posterior. It should bewww.indiandentalacademy.com noted though that
If the outer bow is located below (angle of less than 20 degree to occlusal plane) the neckstrap, the resultant force will be a small intrusive one, instead of extrusive. Of course, a distal force and large clockwise moment will also be produced. The direction of pull provided by the cervical headgear is especially advantageous in treating short-face Class II maxillary protrusive cases with low mandibular plane angles and deep bites, where it is desirable to extrude the upper posterior teeth. Also, the clockwise moment that is so readily produced with this headgear is very effective in helping conserve anchorage in extraction cases. outer bow is short -- steepen the occlusal plane outer bow is long -- flatten the occlusalwww.indiandentalacademy.com plane
If the teeth are banded and stabilized, cervical pull appliance, produces a force below both center of resistance of maxilla and the dentition.. The distances of the force vector to A and B determine the center of rotation (x). www.indiandentalacademy.com
High Pull Headgear
The high-pull headgear, like the cervical-pull, is analyzed using the same principles of force and moment production described before. This style headgear always produces an intrusive and posterior direction of pull, due to the position of the headcap.
The direction of the moment that is produced is dependent on the position of the outer bow . If the outer bow is placed anterior to the LFO (angulated > 45 degree to occlusal plane) moment produced will be counterclockwise.
On the other hand, if the outer bow is placed posterior to this line (angulated less than 45 degree to occlusal plane), the moment produced will be in a clockwise www.indiandentalacademy.com direction.
High-pull headgears produce intrusive and posterior forces. Locating the outer bow in front of the LFO (A and D) will produce a counterclockwise M while an OB behind (B and C) will create a clockwise M. An OB located on the LFO would of course produce no M.
www.indiandentalacademy.com
 

The magnitude of this moment will be proportional to the distance of the outer bow to the CR. If a distal and intrusive movement with no moment is desired, the outer bow must be placed somewhere along the LFO. This force system would be beneficial in a long-face Class II patient with a high mandibular plane angle, where intrusion of maxillary molars would decrease facial height and improve the facial profile. www.indiandentalacademy.com
Short outer bow angulated high to create the headgear force line of action that is far anterior to the unit’s centre of resistance. This results in a force system at the unit’s center of resistance with a moment that tends to flatten the occlusal plane and distal and intrusive force www.indiandentalacademy.com
With long outer bow such that the headgear force’s line of action passes through the unit’s center of resistance and therefore no change in the cant of occlusal plane
www.indiandentalacademy.com
Long outer bow. The equivalent force system at the unit’s center of resistance has a moment that tends to steepen the occlusal plane and a force with intrusive and distal components. May be necessary for class II open bite patients. www.indiandentalacademy.com
Straight Pull Headgear or Interlandi or Combination headgear
This style headgear is a combination of the high-pull and cervical headgear, with the advantage of increased versatility. Depending on the force system desired, the orthodontist has the opportunity to change the location of the LFO. The prime advantage of this headgear is its ability to produce an essentially pure posterior translatory force. This is accomplished by placing the LFO through the center of resistance, parallel to the occlusal plane. Clinically, this means bending the outer bow to the same level as CR, and hooking the elastic to a notch at the same vertical level. www.indiandentalacademy.com
The straight-pull headgear is versatile in that the clinician has many optional LFO's . In this case an OB located on the LFO would cause translation in a posterior and slightly superior direction. OB's above the LFO will produce posterior and extrusive forces and clockwise moments. Placing the outer bow along an LFO that Is parallel to the maxillary occlusal plane will produce a pure posterior translation.
www.indiandentalacademy.com


The relation of the outer bow to the LFO dictates the direction and magnitude of forces and moments. Placing the outer bow above the LFO will produce a posterior force, counterclockwise rotation, and most often an intrusive force. However, if the LFO cants up anteriorly (attachment site of elastic is lower on headcap than at outer bow), an extrusive force will be produced. If the outer bow is below the LFO, the force produced will be posterior and superior, and the moment will be in a clockwise direction. www.indiandentalacademy.com

The straight-pull is the headgear of choice in a Class II malocclusion with no vertical problems.

It is also the headgear of preference when the main thrust of headgear wear is to prevent anterior migration of maxillary teeth, or possibly even translate them posteriorly.
www.indiandentalacademy.com
Force’s line of action passes through center of resistance. No moment acting to change the cant of occlusal plane, and there is pure distal force passing through the center of resistance. www.indiandentalacademy.com
This configuration is typical for redirecting maxillary horizontal growth in class II patients and /or to move maxillary molars distally via translation. When a force is applied to a headgear with inner and outer bows, one side effect is buccal expansion component of forces, which act bilaterally. This side effect is often helpful in class II malocclusions because it is often necessary to expand the posteriors to maintain proper interception as the buccal segment class II interrelationship is corrected. If such expansion is not required, it can be prevented by using a transpalatal arch. www.indiandentalacademy.com
Vertical Pull Headgear
The main purpose of this headgear is to produce an intrusive direction of force to maxillary teeth, with posteriorly directed forces. If the outer bow is hooked to the headcap so that the line of force is perpendicular to the occlusal plane and through the CR, pure intrusion may take place. Due to the multiple notches in the headcap, this headgear is also very versatile, as the LFO orientation may be changed. However, upon establishing the LFO, our principles of determining force systems produced remains unchanged. www.indiandentalacademy.com
The vertical-pull headgear is used primarily when a large magnitude of pure intrusion is needed. The outer bow must be located on the LFO to obtain pure intrusion (A). An OB located anterior to the LFO will produce an intrusive force and a smaller posterior force and a counterclockwise moment (B and C). Locating the OB posterior to LFO will cause intrusion a small anterior force and a clockwise moment (D and E). www.indiandentalacademy.com



The head is divided into two components: the anterior component from the LFO forward and the posterior component located behind the LFO. If the outer bow is placed anywhere in the anterior compartment, the moment created will be counterclockwise, and the forces produced will be intrusive and posterior. If the outer bow is placed anywhere in the posterior section, the moment will be clockwise and the vertical force will be intrusive, but the horizontal force will be forward. If this latter force system is desired, it will require inserting the inner bow into the buccal headgear tube www.indiandentalacademy.com from the distal.

The vertical-pull headgear is not as commonly used as are the others.

However, it is very useful when pure intrusion of buccal segments is required, as in the Class I open-bite patient.
www.indiandentalacademy.com
Adjusting Directional Pull of occipital Headgear
Several possibilities exist but what movement is needed in buccal segments should be analyzed. If distal translation is needed , a distal force straight through the center of resistance is needed. The combination or interlandi headgear will allow this by having equal occipital and cervical components on an outer bow, which is angled upward to pass through the center of resistance. Intrusion of upper anterior segment with a base arch would produce a undesirable side effect of eruption and a rotation of upper buccal segments. To prevent this an upward and backward force anterior to the center of resistance of buccal segments is needed which can be done by using a short outer bow and the occipital pull. www.indiandentalacademy.com
Asymmetric Headgear
Right versus left asymmetries can be corrected using transpalatal or lingual arches to correct asymmetric molar axial inclinations. The same mechanism can be used to correct asymmetric molar rotations. If buccal occlusion is asymmetric e.g. Class I on one side and class II on the other side, without asymmetries either in molar axial inclinations or in rotations, then it is most logical to achieve the correction with asymmetric headgear. Distal forces exist on both sides, but they are three times greater on the long outer bow side than on the short outer bow side. www.indiandentalacademy.com


Lateral forces, directed toward the short outer bow side exist with this headgear. Crossbite development should be kept in mind. These are usually cervical or combination type.
www.indiandentalacademy.com

Suggestions to be noted with regard to the use of the asymmetric cervical gear: 1. The differential in length of arms of face-bow need not be great, only sufficient to alter the geometry so that the resultant bisector crosses the molar line closer to the more anteriorly positioned molar than to the other. Excessive difference in arm lengths could increase the lateral forces. 2. The diameter of wires can be increased for greater rigidity; it is suggested that the arch wire be 0.055 inch and the face-bow 0.075 inch (the 0.075 inch face-bow is approximately five times as stiff as the 0.50 inch one). 3. The arms of the face-bow should clear the cheeks so www.indiandentalacademy.com as not to introduce more undesirable lateral forces.
Asymmetric Headgear forces
www.indiandentalacademy.com


Rigorous force analysis of the several cervical gears of different design using elastic straps shows that the fundamental principle involved in the distribution of the forces to the right and left molars is the geometry of the direction of the right and left forces emanating from the cervical elastic band. If these forces are symmetrical with reference to the midsagittal line of the head, then the distribution of the reactionary forces at the right and left molars will be equal, irrespective of the design of the rigid portions of the appliance (or the point of attachment of face-bow to arch wire). www.indiandentalacademy.com
If the direction of forces from the cervical elastic band is asymmetrical with respect to the midsagittal line of the head, then the anterior-posterior components of the reactionary forces on the right and left molars will be unequal, the molar nearest the resultant of the two elastic band forces receiving the greater force. 2. Small lateral forces on the molars are always developed by this eccentric design. These forces can be manipulated to cause all lateral reaction to occur on one side or the other by springing the labial arch inward or outward, respectively. 
www.indiandentalacademy.com
Headgear to lower jaw 1) 2) 1. 2.
Headgear bracket-tube combinations can be attached to either lower first or second molar. If the bracket-tube combination is on the first molar, it is advantageous to place the headgear tube occlusally. First molar is preferred since The lingual arch is on the first molar and gives better control. It is easier for the patient. Possible directions are: The posterior segments tend to move back A positive moment will be produced, which will steepen the occlusal plane. www.indiandentalacademy.com
J- hook Headgear J-hooks to arch wire A line of pull attached to the incisor region of the arch wire and passing occlusally to the center of the resistance will place a distally directed force upon the maxillary teeth, but will also tip the occlusal plane downwards at the incisor end of the arch. A line of pull through center of resistance will produce distal movement of the maxillary arch without undesirable rotational effects. A more vertical direction of pull, mesial and apical to center of resistance produces an anti-clockwise moment and an intrusive effect upon the incisor end of the arch wire Disadvantage is that the flexibility of arch wire results in unavoidable deformations which subject the teeth near the attachment to diurnal reversals of force application as the extraoral appliance is attached or disengaged. Heavy arch www.indiandentalacademy.com wires minimize this rebound effect, but not eliminated.
J-hooks to individual teeth  If the center of resistance of a single tooth coincides with the centroid the line of force of a J-hook headgear intended to produce upright bodily movement of an individual tooth should ideally pass through this center of resistance.  Most authorities suggest an occipitally directed line of force to move maxillary canines distally. But straight pull is suggested as it is difficult to obey theoretical concepts when moving mandibular canines. www.indiandentalacademy.com
Direction of Headgear Force Given by the line of action of force from the point of origin to the point of application of force. Anteroposterior Plane:  Explained by linear vectors of force. An anteroposterior force that does not pass through the occlusal plane will certainly have a vertical component. a) Force directed upwards above the occlusal plane has an intrusive effect on maxilla. b) Force directed downwards below the occlusal plane has an extrusive effect on maxilla. c) Force passing along Center of Resistance produces www.indiandentalacademy.com translation. 
d) Force away from center of resistance( mesially, distally, apically, occlusally) produces a moment tending to change the occlusal cant. e) Magnitude of moment is determined by moment arm. Greater the moment arm – closer the Center of rotation moves towards canter of resistance and greater is the moment. f) Medium length of outer bow is chosen for translation. g) Short / long outer bow chosen when moment is desired. www.indiandentalacademy.com
Vertical Plane: a) Direction determined by the sense of the line of action. b) Outer bow along the Center of resistance produces translation. c) Force apical / occlusal to center of resistance produces moment ( Extrusive / intrusive / distal). d) Magnitude dependent on the inclination of line of action. www.indiandentalacademy.com
Lateral Plane: a) Shape or length of outer Bow has no effect on force application provided the distance of point of attachment to the midline axis are equal. Headgear tube placed buccal to center of resistance. b) Hence any force applied, passes buccal to center of resistance tending to roll the molars, buccally on intrusion and palatally on extrusion. This rotatory tendency is directly proportional to the perpendicular distance of buccal tube to center of resistance (moment arm). Clinically this moment is countered using 1. Palatal bar www.indiandentalacademy.com 2. Rectangular headgear tubes
Magnitude of Force
When line of action is closer to center of resistance greater force of 450 – 500 gms may be applied for orthopedic changes.
Forces away from center of resistance that produce a moment should be restricted to 50 – 150 gm as in J – hook headgear to prevent damage to periodontium during dento alveolar changes that take place during a moment.
www.indiandentalacademy.com
Duration of Force
Intermittent force for 12 – 14 hrs in preadolescent age from early evening until next morning.
Typical duration of treatment of about 12 to 18 months, depending on rapidity of growth and patient cooperation.
www.indiandentalacademy.com
CLINICAL APPLICATIONS OF HEADGEAR FORCE 
There are four main uses of headgear force
1.
Anchorage control Tooth movement Orthopedic changes Controlling the cant of the occlusal plane
2. 3. 4.
www.indiandentalacademy.com
Anchorage Control
In class II treatment, headgear force can play a major role in ensuring that buccal segment teeth do not move mesially when anteriors are retracted. Intraoral mechanics often result in eruption of teeth. Headgear produces a vertical force greater than the force of side effect Inner and outer bows can be of any shape, convolution, and length. Only the angle and level of the final line of action after the strap forces have been applied to know exactly the force www.indiandentalacademy.com of headgear system.
Vertical force on molar tube, a side effect of intraoral mechanics
Vertical component of occipital headgear force negates extrusive intraoral force side effect
www.indiandentalacademy.com



The reaction force from headgear is dissipated against the bones of the cranial vault, thus adding the resistance of these structures to the anchorage unit. The only problem with reinforcement outside the dental arch is that springs within an arch provide constant forces, whereas elastics from one arch to the other tend to be intermittent, and extraoral force is likely to be even more intermittent. For first molar extraction cases -Interlandi headgear to be suitable and well tolerated www.indiandentalacademy.com
Tooth movement 

Adjustment of outer bow such that a horizontal force is produced that passes through the center of resistance of maxillary first molar and the patient wears the headgear at a level of 14 hours each night consistently, clinical experience shows that the first molars will move distally 2mm in 24 months without tipping. Distal tipping is not preferred as finite element studies have shown that the stress levels at the periodontal ligament-bone and tooth interfaces are beyond acceptable limits even when tipping forces are very light. www.indiandentalacademy.com
Intrusion in deep bite cases Headgear can be used in adjunct to upper utility arch. High pull headgear allows more intrusive control permitting maximal incisor movement whilst minimizing possible molar tipping and also used to deliver orthopedic force on developed premaxillary segment. 120 to 150 g force is delivered. Distalization of molars Headgear is the obvious choice. Fill time wear is necessary. Molar extrusion should be avoided so straight pull or high pull is used and not cervical. Force – 300g on each side. Unilateral molar distalization in unilateral class II can be www.indiandentalacademy.com achieved by asymmetric cervical headgear
Canine retraction using direct headgear force  Headgear using four hooks is used, which over a base arch wire 19 x 25 steel.  200 g of force supplied to each point of attachment to slide the canines posteriorly www.indiandentalacademy.com
Orthopedic changes 
If the headgear is applied through the center of resistance of maxilla, which is in the posterosuperior part of maxilla. Determined clinically by dropping a line vertically 10mm from the outer canthus of eye and making a horizontal from that point to meet the pupil line in front of the face. www.indiandentalacademy.com
If a preadolescent patient wears the headgear at least 12 hours each night , the forward component of maxillary growth is redirected. Effects of orthopedic forces on maxilla  Cervical traction produces stresses along the frontal process of maxilla, zygomaticofrontal suture, and the junction of the palatine bones, areas where high-pull traction produced no observable effect. Only the high-pull headgear produces stress at the anterior junction of maxillae (anterior nasal spine). 
www.indiandentalacademy.com
Pterygoid plates of the sphenoid High stress develops upon activation. These stresses begin in the middle of the posterior curvature of the plates and just superior to their anterior junction with the palatine bone and maxilla. As the force increases, the stresses progress superiorly toward the body of the sphenoid bone. Zygomatic arches Cervical and high pull both produce similar stress . Starts at the inferior border of the zygomaticotemporal suture and proceeds posteriorly along the zygomatic process of temporal bone. Cervical force produces more intensitywww.indiandentalacademy.com at lower load level.
Junction of the maxilla with the lacrimal and ethmoid bones Both cervical and high pull produce a stress concentration at the junction of the maxilla with the lacrimal bones and with the orbital plates of ethmoid. Maxillary teeth High stresses around maxillary molars with cervical traction. These located around the middle third of the mesiobuccal root and around distobuccal root at a position toward apex. Also distal to second molar. Frontal process of maxilla Stresses produced anterior to nasolacrimal foramen only with www.indiandentalacademy.com cervical pull.
Zygomaticofrontal suture Just before maximum cervical load stress begins to appear. Only with cervical pull. Palate Cervical traction produces stress in posterior region developing in the horizontal portion of palatine bones. High pull has no effect. Anterior junction of left and right maxillae Only high pull produces forces below the anterior nasal spine and just lateral to the suture between the two www.indiandentalacademy.com maxillae.
Sphenomaxillary suture- large compressive stresses. Temporozygomatic suture- tensile normal stresses Sphenozygomatic suture- large tensile stresses Frontozygomatic suture- large compressive stress Frontomaxillary suture- large tensile stress 

Sphenomaxillary and sphenozygomatic sutures, in particular, resisted the posterior displacement of the complex Stresses in the nasomaxillary sutures are varied by the direction of headgear force, and the force applied in the direction closest to that of the CRe may produce the most effective sutural modification for controlling maxillary www.indiandentalacademy.com growth.



Clinical studies have also demonstrated that extraoral force is effective at restricting maxillary horizontal growth. In fact, several studies are also available which indicate that headgear therapy can reposition the maxillary complex posteriorly and inferiorly in growing patients. Armstrong has demonstrated remarkably rapid (three to four months) correction of Class II malocclusions in growing patients with the use of continuous heavy forces parallel to the occlusal plane. Although not attached to the mandible or primarily aimed at mandibular alteration, headgear treatment has been shown to effect mandibular remodeling; the mandible and chin point have been shown to relocate anteriorly in standard edgewise treatment. Whether this represents a change which would not www.indiandentalacademy.com
In Class II malocclusions with a fault in maxilla, profile convexity of the upper jaw can be a) Basal – large S-N-A angle b) Dentoalveolar – increased sell-nasion-prosthion (SN_Pr) angle. c) Dental – increased upper incisor to S-N plane angle Maxillary basal prognathism requires heavy orthopedic force. When evaluating the maxillary base, the inclination should also be considered. An upward and forward inclination aggravates maxillary protrusion. (Schwarz (1958) termed this as www.indiandentalacademy.com pseudoprotrusion)
A retro inclination (palatal plane tipped anteriorly can actually compensate for maxillary prognathism. The control of the vertical dimension in this type of malocclusion often depends on the inclination of the maxillary base, especially if it is combined with either a deep overbite or an open bite. Combined activator – headgear therapy is required.
www.indiandentalacademy.com
Short face( skeletal Deep bite) Class II when growth potential remains  Goal is to increase face height and correct deep bite, while allowing more eruption of the lower than the upper teeth so that the occlusal plane rotates up posteriorly.  Although cervical headgear tends to open the bite anteriorly and therefore would help to correct a deep bite problem, it differentially erupts the upper rather than the lower molars and does not produce the desired change in the orientation of occlusal plane.  www.indiandentalacademy.com So functional appliances are useful in these patients.
Class II with normal face height and growth potential Clinical studies show that in these patients , many have deep bite due to excessive eruption of lower incisors. And can be treated successfully by two stage treatment. Stage I using headgear or functional appliances. Straight pull or high pull headgear is preferred over cervical headgear, to reduce the elongation of maxillary molars and better control the inclination of the mandibular plane. www.indiandentalacademy.com
Skeletal open bite Characterized by excessive AFH. Major diagnostic criteria are: 1. Short mandibular ramus 2. a rotation of the palatal plane down posteriorly. Typical growth pattern shows vertical growth of the maxilla, often more posteriorly than anteriorly, coupled with downwardbackward rotation of the mandible and excessive eruption of maxillary and mandibular teeth. Only two thirds of the patients have actually an open bite – in others excessive eruption of incisors keeps the bite closed – but rotation of the mandible produces class II malocclusion even if the mandible is normal in size and severe class II if the mandible is small. www.indiandentalacademy.com


Successful growth modification would be restraining vertical development and encouraging anteroposterior mandibular growth while controlling the eruption of teeth in both jaws. High pull headgear to the maxillary first molars is the least effective because it does not control the eruption of other teeth. Furthermore use of molars as primary handle on maxilla presents three problems: 1.Vertical component of force produces buccolingual tipping . 2. The level of force application is limited by the tolerance and response of the supporting tissues of these two teeth. www.indiandentalacademy.com 3. Molar movement is the predominant dental change.
 
High pull headgear with maxillary splint is better, as it provides en masse dental control. Advantages 1. restraint of anteroinferior displacement of maxillary complex with growth. 2. restraint of maxillary teeth 3. Disengagement corrects occlusal interferences, facilitating correction of functional mandibular displacements. 4. Direction and distribution of extraoral force application to the maxilla may be adjusted over a broader range. 5. incisors can be retracted by including labial bow in the design and full control over incisor tipping possible. www.indiandentalacademy.com 6. safety enhanced.
But this does not control the eruption of lower teeth. Eruption of lower teeth is controlled most readily by interocclusal bite blocks, easily incorporated into a functional appliance. If the bite blocks separates the teeth more than the freeway space, force is created against both upper and lower teeth that opposes eruption. So the most effective treatment is a combination of a functional appliance with bite blocks and high pull headgear. If cervical (Kloehn type) headgear is used, the maxillary molars are driven distally into the “wedge” as the molars are extruded or tipped down and back. The mandible is rotated down and back, increasing the apparent mandibular retrusion and allowing compensatory alveolodental growth to stabilize this undesirable saggital change. The maxillary incisors are usually tipped down and back at the same time, restricting forward mandibular growth. This result is now known as kloehn effect. www.indiandentalacademy.com
With combined activator – headgear treatment, high pull headgear attached to activator exerts a retarding force on horizontal and vertical maxillary growth vectors. A high pull headgear does not tip the palatal plane down and does not tip up the anterior end of the palatal plane, which tends to enhance maxillary incisor protrusion and upper lip prominence.
www.indiandentalacademy.com

The headgear-activator has the following modes of action: 1. Intrusion and retraction of upper front teeth 2. Distalization of upper molars 3. Maxilla retraction 4. Mandibular growth stimulation, especially in the brachyfacial group 5. Opening of the facial axis in the brachyfacial group 6. Maintenance of the facial axis in the dolichofacial group 7. Minor, if any, tilting of lower incisors 8. Stopping lower incisor eruption 9. Stopping the descent of the palate www.indiandentalacademy.com

Vertical control is obtained in two ways. 1.The untrimmed interocclusal acrylic acts as a bite block, preventing molar eruption and clockwise mandibular rotation. 2.The inclination of the outer facebow allows precise control over the direction of force, according to the following principles: a) A force passing through the center of resistance produces pure translation in the direction of the force. b) A force passing at a distance from the center of resistance generates a moment, with a combined effect of rotation (from the moment) and translation (from the force). www.indiandentalacademy.com
Cephalometric guidelines for headgear treatment Direction of growth Broad mandibular base and ascending ramus together with a very marked, thick symphysis suggest a change in direction toward horizontal growth. Narrow mandible and thin symphysis – vertical growth. Growth potential If the mandible is too small in class II in a growing individual, growth may be expected to be quite considerable. A well developed mandible in a posterior position must be considered to offer poor prospects for successful correction of class II malocclusion, except in cases with translation. Convexity of nasomaxillary complex SNA angle large ANS far anterior to N- Pog line. Ante – inclination of maxilla (large J angle) will increase protrusion (pseudo protrusion). Midface (N – Sn) is short. Extreme case – www.indiandentalacademy.com Microrhinal dysplasia.
Timing of headgear treatment
The most optimum treatment time is between maturational stages SMI 4 to 7, a very high velocity period of growth. The next most desirable time to treat is during the accelerating velocity period between stages SMI 1 to 3 the least desirable time is during the decelerating velocity period between maturational stages SMI 8 to 11. This information is clinically useful for all growth related mechanics of treatment, retention, and www.indiandentalacademy.com
Skeletal maturity index
SMI 1: third finger, proximal phalanx; width of epiphysis as wide as or wider than diaphysis. SMI 2: third finger, middle phalanx; width of epiphysis as wide as or wider than diaphysis. SMI 3: fifth (little) finger; width of epiphysis as wide as or wider than diaphysis. SMI 4: ossification of adductor sesamoid of thumb SMI 5: third finger, distal phalanx; capping of both sides of epiphysis SMI 6: third finger, middle phalanx; capping of both sides of epiphysis SMI 7: fifth finger, middle phalanx; capping of both sides of epiphysis SMI 8: third finger, distal phalanx; complete fusion SMI 9: third finger, proximal phalanx; complete fusion. SMI 10: third finger, middle phalanx; complete fusion. SMI 11: radius; complete fusion (skeletal growth completed). www.indiandentalacademy.com
Reverse headgear or Protraction headgear
Several authors have reported on the effects of anteriorly directed forces on the maxillary complex both clinically and experimentally. In his study, Dellinger examined anterior maxillary displacement and reported that the maxilla could be moved forward significantly in animals. Kambara demonstrated significant maxillary changes in suture areas and an anterior displacement with a slight anterior rotation of the maxillary complex. Ishii found that the relapse of facial bones was very slight and the modality of relapse was divided into two phases— the posterior rotation of the maxillary complex taking place 1 month after removal of the applied forces and the dental changes following the protraction period. Oppenheim suggested a technique to displace the maxilla forward to achieve a cosmetic improvement without www.indiandentalacademy.com subjecting the patient to a surgical procedure.
Irie and Nakamura reported that the acceleration of forward growth of the midface and improvement of jaw relationship were obtained clinically by means of maxillary protraction with the chin cup. Delaire and associates claimed that using the facial mask to protract the maxilla anteriorly worked effectively in an extensive number of young patients. Nanda and associates and Yamaguchi and associates introduced a modified protraction headgear bow to control force variables such as direction and point of force application. Nanda and associates also presented the theoretical aspects and technical improvements necessary for relating biomechanical approaches to study alterations in craniofacial morphology. www.indiandentalacademy.com
Used in horizontal-vertical maxillary deficiency. Usual effect of reverse headgear was forward movement of the maxillary teeth with little or no skeletal effect on maxilla, along with downward and backward rotation of the mandible. In the late 1970’s Delaire and coworkers in France showed that forward positioning of the skeletal maxilla could be achieved with reverse headgear if treatment was begun at an early age. Best data indicate that increase in maxillary growth occurs only in young patients (below age 10). Hence a child with maxillary deficiency should be referred for complete evaluation as early as possible. The chance of successful forward movement is essentially zero by the www.indiandentalacademy.com


But even in young patients, two side effects are almost inevitable when reverse headgear is used: 1. forward movement of maxillary teeth relative to maxilla and 2. downward and backward rotation of the mandible. Hence ideal patients for this method should have both a) Normally positioned or retrusive, but not protrusive, maxillary teeth b) Normal or short, but not long, anterior facial www.indiandentalacademy.com vertical dimensions.
Protraction forces applied 10 mm above the Frankfort horizontal plane produced a posterior rotation of the maxilla with a forward movement of nasion; Protraction forces applied 5 mm above the palatal plane produced a combination of parallel forward movement and a very slight anterior rotation; Protraction forces applied at the level of the maxillary arch produced an anterior rotation and forward movement of the maxilla; All three protraction forces caused the constriction of the anterior part of the palate. www.indiandentalacademy.com
Delaire’s Facemask
Delaire’s facemask is simple and well accepted by children. The attachment is to a maxillary splint incorporating all the teeth. If a three dimensional deficiency exists so that the maxilla is narrow as well as deficient anteroposteriorly and vertically, slow expansion can be done simultaneously with protraction. www.indiandentalacademy.com
Diagnostic principles for treatment of maxillary deficiency with protraction headgear


1. Determine whether the mandible, on closure, is in centric relation or in a "convenient" anterior position. Anterior positioning generally results from tooth contact relationships which "force" the mandible into a forward position. In contrast, centric relation is determined by the muscles, the ligaments, and the temporomandibular joint anatomy under the control of the nervous system. The practical implication is that a Class I problem can appear to be a Class III malocclusion (pseudo-Class III malocclusion) when the mandible is forced anteriorly. Even a true Class III malocclusion can appear much more serious if there is an anterior path of closure of the mandible. 2. Nature of the skeletal discrepancy must be defined because treatment, to a large extent, is based on this differential diagnosis. www.indiandentalacademy.com
3.A malocclusion reflects the interplay of many conditions that may be impossible to evaluate singularly. One important variable is the potential growth and development of a patient with a Class III malocclusion. 1. Maxilla retrognathic -- Treatment should be started early, as early as 4 years of age, for two fundamental reasons. a) One is that extraoral traction which pulls the maxilla anteriorly functions in the same direction as the direction of development. b) Second, unlike posterior movement of the mandibular arch, anterior movement of the maxillary arch appears to have a greater chance of remaining stable. www.indiandentalacademy.com


With this kind of treatment, we can expect to achieve ( 1) an orthopedic protraction of the maxilla with a strong enough force (500 to 1,000 Gm per side). (2) an increase in the inclination of the maxillary incisors to obtain a sufficient overjet, associated more or less with (3) bodily movement of all the teeth in an anterior direction, (4) both an improvement in function and a more esthetic profile. Studies indicate similar skeletal response can be obtained when maxillary protraction was initiated either before age 8 years (5 to 8 years) or after age 8 years (8 www.indiandentalacademy.com to 12 years).

Augmenting forward growth of maxilla is not as successful as restraining the growth as seen clinically. This is because, 1. inability to produce enough force at the posterior and superior sutures to separate them in older children. 2. extent of interdigitation of bony spicules across the sutural lines.

Clinical experience suggests that more than 3mm forward displacement of the maxilla is unlikely, probably because of soft tissue limitations. www.indiandentalacademy.com
Chin cup therapy
Used in mandibular excess. Recent research indicates that condylar growth is largely a response to translation as surrounding tissues grow. Elastic type of chin cup produces lingual inclination of lower incisors, an undesirable side effect even with plastic chin cup. Ideal patient with excess mandibular growth for chin cup therapy is one who has: a) A mild skeletal problem, with ability to bring the incisors end to end b) Short vertical facial height c) Normally positioned or protrusive, but not retrusive lower incisors. A reverse overjet of more than 4 mm inwww.indiandentalacademy.com preadolescent period
1.The downward vertical growth of the midface is inhibited by use of the chin cup. Posterior vertical development is inhibited more than anterior vertical development, resulting in a clockwise rotation of the maxilla and midface. 2. The chin cup has no effect on the anteroposterior growth of the midface. 3. The modifications in midfacial growth appear to be adaptational responses to similar alterations in mandibular growth caused directly by the chin cup. Such modifications are necessary to maintain harmonious growth between the maxilla and mandible. 4. Force transfer from the chin cup via the mandible to the middle cranial fossae results in a closure of the cranial flexure angle, N-SBa°, and alterations in the manner of growth of Ba (x) and S (y). 5. The maxillary molars move in a mesial direction at a rate greater than in the control group, but are not affected in their rate of eruption. The increased mesial movement is probably related to the increased www.indiandentalacademy.com rate of forward movement of the mandibular molars.
Two main approaches to chin cup therapy
Response to chincup therapy
www.indiandentalacademy.com
SELECTION GUIDELINES FOR HEADGEAR TYPES 1. Cervical pull face bow headgear a) A large horizontal component of force is present, but also a vertical component, which may extrude the maxillary molar. b) Molar extrusion may assist the treatment of class II, low Frankfurt-mandibular angle, increased overbite cases. c) Limited molar extrusion will probably not affect class II cases with an average FMA, particularly if angle SNB is average. Facial changes must be monitored during treatment. d) High FMA, class II cases, should never be subjected to this line of force to avoid the creation of an unfavorable mandibular rotation, with consequent ill effects upon the www.indiandentalacademy.com face.
Outer arms bent downwards will tilt distally the crowns of mesially tilted molars. f) Outer arms bent upwards appear to result in more upright, but less distal movement. 2. Straight pull face bow headgear a) A very large horizontal component of force is present. b) A small vertical force component may produce mild extrusion. c) It will probably effect less distal movement of the root, than of the crown. e)
www.indiandentalacademy.com
3. High pull face bow headgear a) Root axial control may be achieved to produce effective upright distal movement of the molar teeth or tilting as is required. b) The molar will be intruded and the ratio between distal and intrusive movement will depend upon the steepness of the angle of pull. c) It is a suitable line of force to move distally the fully banded maxillary arch, intruding the molar end and less certainly the incisor end. d) In high FMA, class II cases, with reduced or even average overbite, distal movement with extrusion of maxillary molars is probably to be avoided, and high www.indiandentalacademy.com pull anchorage may be advantageous.
e) In high FMA, class II cases, with anterior open bite, a vertical line of force commencing occlusally and passing distally to the center of resistance, will intrude the maxillary molars and may rotate downwards the incisal end of a fully banded arch. 4. Cervical pull J-hook headgear a) Used to the maxillary incisor region, a tipping of the incisal end of the occlusal plane in a downward direction may result, with a reduction of open bite. However molar extrusion is probable. b) Used to the mandibular incisor region, it may depress the chin creating more vertical space into which maxillary teeth may be extruded during class III treatment. The resultant downward and backward rotation reduces the anterowww.indiandentalacademy.com posterior basal discrepancy.
5. Straight pull J-hook headgear a) It is suitable for moving mandibular canines distally. b) Attached to the maxillary incisor region, distal arch movement occurs, but a downward tipping of the incisal end of the arch is probable. 6. High pull j-hook headgear a) A line of force to the maxillary incisor region passing mesial and apical to the center of resistance, will intrude the upper incisors, move them distally and augment palatal root torque. b) A line of force to the maxillary incisor region passing through the center of resistance will have a large distal and smaller intrusive effect upon the incisor region. Theoretically this may produce the greatest orthopedic effect. www.indiandentalacademy.com
c)
A line of force to the maxillary incisor region passing occlusal to the center of resistance may have a mild downward tipping effect upon the incisal end of the occlusal plane.
d) It is the direction of choice for distal movement of maxillary canines or to sliding jigs for maxillary molar distal movement or anchorage
www.indiandentalacademy.com
The following are to be followed with headgear treatment: 1. Routine use of Visual Treatment Objective of some type of comparative treatment goal. 2. Routine cephalometric x-rays at six to nine month intervals to evaluate treatment changes and progress. 3. Knowledge of normal growth and the effects of orthodontic treatment and extraoral forces to the patient. 4. A prediction of the future skeletal pattern of the patient, the accuracy of which can be enhanced by the control that can be exerted upon the skeletal pattern by proper www.indiandentalacademy.com orthodontic and orthopedic treatment.
Extraoral anchorage in Edgewise
Either occipital or cervical anchorage may be used to supplement the intraoral Class II elastics. Wire hooks extending from a plastic cervical tube can be used to attach the Class II loops on the maxillary arch wire. Traction was derived from rubber bands secured to the posterior ends of the wires within the tube. The amount of pressure is determined by the reaction of the teeth; it should be strong enough to cause moderate tenderness following eight or ten hours' application. www.indiandentalacademy.com
Headgear in Pre-adjusted edgewise appliance Anchorage Extra oral force is the most effective way to provide posterior anchorage control in upper arch. Combination headgear using a force level of 150 – 250 g for occipital pull and 100 – 150 g for the cervical pull. These force values allow for slightly stronger pull on the occipital component of the headgear, keeping forces directed slightly above the occlusal plane and minimizing the tendency for vertical extrusion of upper posterior teeth, while simultaneously allowing effective distalization of molar. On high angle cases where little distalization of molar is required, an occipital headgear alone can be utilized. www.indiandentalacademy.com
In very low angle cases, where musculature is strong enough to minimize vertical extrusion of the posterior teeth, a cervical headgear can be considered.
In controlled space closure
Combination headgear with ‘J’ hook carried directly to arch wire hooks in the maxilla in selected cases with the arch wire turned upside down. www.indiandentalacademy.com
Headgear in refined Begg technique In third stage  In treatment of malocclusions such as very large overjet, very deep overbite or severe bimaxillary protrusion, anchorage needs to be reinforced.  A headgear may be added to the upper molars to augment anchorage in sagittal and vertical direction.
www.indiandentalacademy.com
Components of face bow system 
Maxillary molar tubes are positioned gingivally or occlusally on the molar bracket.

The advantage to gingival placement is that the tube is closer to the center of rotation of molar, which reduces molar tipping. www.indiandentalacademy.com
The outer Bow
The outer bow ends anteriorly to the ears. Then when a patient wears a combination face bow, the high pull portion will fit naturally in front of the ears and the neck strap will attach below the ears. In all cases, the outer bow is positioned in the horizontal plane parallel to and even with the inner bow. When using a high pull retractor, the end of the outer bow should coincide with the location of the maxillary first molars. It is bent 60 degree angle superior to horizontal. The outer bow must be adjusted to www.indiandentalacademy.com fit the face of the patient. Should be 5 to 10mm away from cheeks.
Outer bow resting passively between lips
Outer bow several millimeters from cheek
www.indiandentalacademy.com
Length of outer bow is critical to the desired changes
www.indiandentalacademy.com
The Inner Bow
Proper adjustment of the inner bow will allow the wire to slide in and out of the headgear tubes easily when the posterior strap is not attached. Adjustments to the inner bow can be made in six directions: bucco-lingually, superior- inferiorly, anteroposteriorly. First Bucco-lingual force is controlled. If the bow is inserted into one headgear tube, the other bow end should be expanded approximately 5mm buccal to the opposite tube. This expansion bend is made near the anterior portion of the inner bow. www.indiandentalacademy.com
As a class II molar relationship is corrected, the relative forward movement of the lower arch will produce a cross bite tendency unless the upper arch width is expanded
www.indiandentalacademy.com
Vertical adjustments can be made at molar adjustment loops
www.indiandentalacademy.com
If maxillary arch expansion is desired and a face bow is used, a greater amount of expansive force must be built into the inner bow. Inner bow is expanded more than 5mm. Secondly, in superior-inferior direction When the patient closes his mouth and relaxes his lips, the anterior junction of the inner and outer bows should not be pushing either lip in vertical direction. The bow should be in a passive position between the lips. In order to maintain this position , the posterior ends of the inner bow are adjusted superiorly or inferiorly. www.indiandentalacademy.com
Lastly, antero-posterior adjustment. Inner-outer bow junction is just anterior to the point where the lips seal. It may be necessary to enlarge or constrict the loops in the inner bow to achieve this position.
www.indiandentalacademy.com



The potential of these devices to injure the face has been recognized by the orthodontic community. Among the possible sites of injury are the eyes. With improper handling, headgear appliances can result in penetrating ocular injuries. The removable metallic bow contains two projections that normally fit into the mouth. However, when pulled forward, the bow can slip from the oral cavity, retract under tension, and strike the eyes with substantial force. Spectacles may provide protection, but it is also possible that these metallic projections under tension could slip beneath the frames and strike the eyes. The distance between these two projections approximates the interpupillary distance. Thus, there www.indiandentalacademy.com is an added risk of
In general, bacterial endophthalmitis occurs infrequently after penetrating ocular injuries. However, in headgear injuries, the risk of bacterial infection is extremely high because the penetrating object is contaminated with saliva. The normal flora of the oral cavity consists of a multitude of organisms, including S viridans, anaerobic and aerobic staphylococci, gram-negative diplococci (Neisseria and Branhamella species), Corynebacterium, Lactobacillus, anaerobic Vibrio, and Actinomyces species. Thus, patients are susceptible to mixed-flora infections. In response to the occurrence of facial injuries, manufacturers are developing new appliances with devices that prevent disengagement or that release the elastic traction when sharp www.indiandentalacademy.com forces are applied
Safety release headgear with spring mechanism which breaks apart when excessive force is applied. www.indiandentalacademy.com
Thank you www.indiandentalacademy.com Leader in continuing dental education
www.indiandentalacademy.com