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Biomechanics of hg /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 ,or call

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  • 1. INDIAN DENTAL ACADEMY Leader in continuing dental education
  • 2. INTRODUCTION:    To achieve a harmonious dentofacial relationship as a result of orthodontic treatment, extraoral devices using the neck or cranium as anchorage have been employed. These extraoral appliances have been used to influence the maxillary and mandibular growth patterns by inhibiting and/or redirecting their normal growth potentials in children before and during maximal pubertal growth. The efficient use of the headgear requires a sound knowledge of basic biomechanics. Understanding how to control the direction and magnitude of the forces produced by various headgear designs is paramount in achieving desirable clinical results.
  • 3.  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.  The use of headgear therapy is very common in the treatment of Class II and class III malocclusions as well as to distalise the maxillary dentition. Extraoral maxillary traction appliances are used to improve the dental relationship between the maxilla and the mandible, as well as the skeletal relationship between the two jaws.
  • 4. COMPONENTS OF HEADGEAR: The principal components are  Force delivering unit: usually a facebow or a J hook that delivers force to the intra oral location  Force generating unit: this is the active unit- usually springs of elastic bands  Anchor unit: its location depends on the direction of the force applied, and is usually from the neck or the head. Force is transmitted to the dental arch by  Facebow: the force is delivered to the first molar by the face bow which is engaged in the buccal tube. It can be attached to removable appliances also. The facebow has an inner and an outer bow. The inner bow is available in either 0.045-0.051 inch, dependent on the size of the headgear tubes on the first molars. The outer bow is usually 0.072 inch.
  • 5. The different methods of making the inner bow stop mesial to the first molar buccal tube are  u- loop: advantage is that the length of the arm can be altered by adjusting the loop;  Bayonet bend: horizontal inset bend that keeps the anterior segment of the bow away from the brackets.  Friction stops: stops can be fixed at the desirable location by crimping it  Stop screws: the position of these screws can be changed and can be re-used. Outer bow is attached to the anchor unit and can be of different types depending on its length:  short- outer bow shorter than the inner bow  medium- outer bow almost the same length as that of the inner bow  long- outer bow is longer than the inner bow
  • 6.       Facebows can be used to control all three dimensions: vertical, sagittal and transverse both dental and skeletal. Facebows can be used to apply force to specific teeth or to the entire arch. It can serve as an orthopedic appliance to modify mandibular and maxillary growth vectors. Facebows are primarily used for their ability to produce sagittal changes. This is the traditional use of the straight pull or the cervical pull. High pull is often used for the vertical, intrusive force which can be applied to the maxillary molars or the entire maxillary arch. Maxillary molar buccal tubes can be either occlusal or gingival. Advantage of placing the tube gingivally is that the tube is closer to the center of rotation of the molar, which reduces the molar tipping effect and is advantageous in conditions where only molar movement is desired.
  • 7. If the facebow is used for orthopedic correction, it is advantageous to place the tube occlusally because the patient finds it easier to insert the inner bows into the tubes. If omega loops are to be used, then these loops can block gingivally placed headgear tubes. Adjustments to the inner bow can be made in  buccolingually  superoinferiorly  anteroposteriorly Buccolingual: If the bow is inserted into one headgear tube, the other bow should be expanded 5 mm buccal to the opposite tube. As the patient fully engages the appliance, he must constrict the inner bow slightly. This will create expansive force on the molars. If maxillary expansion is desired and facebow is being used, a greater amount of expansion must be built in the inner bow. If constriction of the maxillary arch is desired, then the inner bow must be constricted. 
  • 8. Superoinferiorly: 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 a vertical direction and it should be in a passive position.  Anteroinferiorly: the facebow should be placed so that the inner and 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. Unilateral face-bows – Hershey (AJO 1981)  Face-bows which successfully and predictably provide an asymmetrical delivery of distal force to their innerbow terminals are termed "unilateral face-bows”. 
  • 9. There are four types of unilateral facebow designs available:  Power-arm face-bow. In this design, one outer bow is longer and/or wider than the other, with the longer or wider bow tip located on the side anticipated to receive the greater distal force. While effective in producing unilateral distal forces, the power-arm face-bow also generates lateral forces which tend to move the favored molar tooth into lingual cross-bite and the other molar into buccal cross-bite. Soldered-offset face-bow. Here the outer bow is attached to the inner bow by a fixed soldered joint placed on the side favored to receive the greater distal force.
  • 10.    Swivel-offset face-bow. In this design the outer bow is attached to the inner bow through a swivel joint located in an offset position on the side favored to receive the greater distal force. Spring-attachment face-bow. Here an open coil of spring is wrapped around one of the inner-bow terminals of a conventional bilateral face-bow. The coil is placed distal to the stop on the side favored to receive the greater distal force. Yoshida et al in AJO 1998 evaluated the effects and side effects of asymmetric face-bows. They suggested that the power arm face-bow is thought to be relatively recommendable because it showed an acceptable asymmetric effect and is easily fabricated from a commercially available face-bow. They concluded that all asymmetric face-bows generate lateral forces as side effects as long as the force delivery system with a combination of an asymmetric face-bow and a neck strap or head cap is applied.
  • 11.  J hook: each J hook consists of a 0.072 inch wire contoured so as to fit over a small soldered stop on the archwire, usually between the upper lateral incisors and the canines.  Headgears are available in a wide variety of configurations, each programmed to deliver force in a predetermined direction. The direction of force determines the general direction in which a tooth, a group of teeth or skeletal unit responds.
  • 12. CLASSIFICATION      1. Headgears can be classified according to the area of attachment into  cervical area of the neck (cervical strap)  occipital area of the head (occipital strap)  the chin (chin cup)  frontal or reverse pull  combination of cervical and occipital (straight pull or combee)  very high pull (parietal) 2. according to the purpose of usage:  A. growth modulators 1. Protractors 2. Retractors 3. To control vertical excess A. reverse pull A. high pull A. chin cup B. straight pull C. cervical pull D. combination B. for space regaining C. molar distalisation D. intrusion of maxilla
  • 13. SELECTION OF HEADGEAR:   1. Headgear anchorage location: location of the anchorage unit determines the type of force that will be applied to the unit. The relation of the force to the Cres of the unit to which it is applied determines the effects that will be produced by the orthopedic force.  High pull headgear: this applies a superior (intrusive) and distal force to the maxilla and the maxillary dentition.  Cervical pull: this produces an inferior (extrusive) and distalising force on the maxilla.  Combination headgear: no moment is produced and a distalising force is applied to the maxilla. Since the Cres of the molar is located in the mid root region, force vectors above this point will result in a distal root movement. Forces below this point will result in a distal crown movement. Similar considerations apply to the maxilla.
  • 14.  2. Age: according to proffit, the ideal age to begin modifying growth is around 8 years (because in some cases, juvenile acceleration of jaw growth occurs at the age of 7-8 yrs just before pubertal growth spurt). It is important to begin growth modification early in girls, since girls undergo pubertal changes by an average of 2 yrs before boys. The treatment of skeletal malocclusions is usually done at the age of 8-9 yrs in girls and 1011 yrs in boys depending on the developmental status. Selection based on MPA (according to Alexander)  A low angle or normal growing (SN-MP< 37 0) case is suitable for cervical headgear.  If SN-MP is between 37-410, a combination headgear is used.  If SN-MP>410, then a high pull HG is used.
  • 15. Based on occlusal plane requirements: Action desired extrusion and steepening extrusion and flattening intrusion and steepening intrusion and flattening distal force and flattening distal force and steepening distal force and no moment headgear type cervical HG; outer bow even or low cervical HG; outer bow very high high pull HG: outer bow postr to Cres high pull HG; outer bow antr to Cres combination; outer bow above Cres combination; outer bow below Cres combination; outer bow at Cres
  • 16. IDEAL PATIENTS FOR TREATMENT WITH HEADGEARS: 1. Patients with maxillary excess:  Ideal patients for treatment with extraoral force against the maxilla show  skeletal class II malocclusion with a component of excessive horizontal or vertical growth of the maxilla  some protrusion of maxillary teeth  Reasonably good mandibular dental and skeletal morphology as this will be minimally affected by extraoral forces.  Potential for continued mandibular growth 2. Patients with horizontal maxillary deficiency:  These patients are ideal candidates for treatment with extraoral forces using the reverse pull headgear. This causes reciprocal downward and backward rotation of the mandible. Ideal patients should have  normally positioned or slightly retrusive but not protrusive maxillary teeth  normal or short but not long anterior facial height  ideal age of 8 yrs
  • 17. 3. Patients with vertical maxillary excess:  In these patients, restriction of vertical maxillary growth is needed along with an augmentation of mandibular growth that is left. Control of vertical eruption of teeth in both the arches is important.   high pull headgear for upper molars is given Interocclusal bite blocks can also aid in prevention of eruption of posterior teeth. E.g. high pull HG with functional appliances. Ideal patients are   long face patients skeletal open bite
  • 18. USES OF HEADGEARS:  Anchorage reinforcement is the most common use of headgear and is used when intraoral sources are insufficient.  distalisation of upper molars when used in the treatment of class II  space maintenance after extraction  canine retraction using J hooks – for anchorage conservation  overjet reduction – Ashers facebow is used to retract upper and lower anteriors simultaneously  intrusion of molars and incisors using high pull headgear  Growth redirection: when used as an orthopedic appliance, headgears can redirect or inhibit maxillary growth and allow normal growth to express clinically by removing dentoalveolar compensations.
  • 19.        Expansion or contraction of the arch: distal driving of molars can result in cross bite as the arch expands posteriorly. This can be avoided by having the facebow expanded in the molar region by about 3-5 mm. This method can be used for the correction of crossbite with headgears. Uprighting of molars space closure torquing roots Correction of rotations of molars. Restriction of mesial drift of teeth associated with age. Reduction of the eruption of teeth into the intermaxillary growth space.
  • 20. HEADGEAR BIOMECHANICS:  The prescription in orthodontics is force application. The mechanical influence of the appliance produces a reaction in the biologic system under stress. Local response can be anticipated in the affected tissues. If force is applied during growing period, a modification of growth dynamics is evident. Force systems a headgear can deliver depends on the magnitude, direction, point of application and its line of action. To determine the effect of the headgear force, the line of action of the force with respect to the body to which it is applied – tooth, arch or the maxilla has to be examined. Hence, knowledge of the approximate location of the body’s center of resistance is essential to choose the force system desired in treatment mechanics.
  • 21.  Force magnitude: Recommended force values per side for  full permanent dentition – 400-600 gms  early mixed dentition – 150-250 gms  late mixed dentition – 300-400 gms  Retention in permanent dentition – 150-400 gms.  Duration: according to Graber, forces of 12-16 hour duration applied as intermittent forces appear to be the most effective for orthopedic changes. Because the headgear is tooth borne, intermittent force minimizes tooth movement while still providing for skeletal change. An intermittent heavy force is less damaging to the periodontium and the teeth.  Force direction or vector: this depends on the location of the extraoral attachment and the location of the outer bow.
  • 22. Center of resistance of maxilla:  Miki 1979 and Hirato 1984 reported that the location of the center of resistance in the midface of the human skull is between the first and second upper premolars anteroposteriorly, and between the lower margin of orbitale and the distal apex of the first molar vertically in the sagittal plane.
  • 23.  Lee in AJO 1997 determined the Cres of the maxilla using holographic inferometry. They found that the Cres of the maxilla was located at the distal contacts of the maxillary first molars, one half the distance from the functional occlusal plane to the inferior border of the orbit. Hence the application of 500 gms per side of force applied 15 mm above the occlusal plane and directed 200 downward from the occlusal plane produced pure translatory movement of maxilla. Protraction of maxilla below the CRes produces counterclockwise rotation of the maxilla. They suggested that by varying the force system, the amount and direction of maxillary rotation might be controlled.
  • 24.  The center of resistance of the dentomaxillary complex when viewed in the sagittal plane is located on a line perpendicular to functional occlusal plane at the distal contact of first maxillary molars. When viewed in the frontal plane, there are two centers of resistance since the dentomaxillary complex is essentially comprised of two bones that articulate with each other at the mid palatal suture. If forces are applied in the presence of a 0.036 stainless steel TPA or a sutural expander, then the two units act as a single unit.
  • 25. Clinical location of the Cres: (angle 1999 Stanley Braun)  The location of the Cres clinically is important. This can be done by holding an amalgam plugger or similar instrument in the maxillary vestibule when the teeth are in occlusion and the soft tissues and lips are relaxed. The amalgam plugger is positioned at the Cres of maxilla. The instrument is then palpated externally and a mark is made on the skin surface corresponding to it. The procedure is done for the other side also. The outer bow may then be adjusted so that the force vector passes through this point.
  • 26.  Tanne et al concluded that the Cres of the maxilla was located at the posterosuperior ridge of the pterygomaxillary fissure. He suggested that the nasomaxillary complex was suspended by a sutural system similar to the desmodontal system of a tooth, possessing a Cres.  Since the handle for applying force to the maxilla is the teeth, a given force vector must be analyzed relative to both the Cres of the dental units (which lies between the bicuspid roots) as well as to the Cres of the skeletal unit. If no rotational effect is desired, then the force vector must pass through the Cres of both the skeletal and dental units. The force passing through both centers of resistance will lead to pure translatory reactive movement with the centers of rotation at infinity.
  • 27.  When planning the direction in which the dental and skeletal units should move to approach a given treatment goal, the effect of growth on the development of these structures must also be considered. The force vector and the growth vector together determine the resultant vector of spatial displacement. The tendency towards extrusion or intrusion in the molar or incisor regions will be determined by the direction of force vector and notably by the rotational tendencies derived from the relation of the force vector to the center of resistance. The least rotational and vertical change is obtained in an arrangement wherein the applied force vector passes through the Cres of the upper arch and the maxilla and this is the desired condition for vertical control.
  • 28. TYPES OF HEADGEARS: CERVICAL HEADGEAR:  This was first introduced by SILAS KLOEHN in 1947. It is the most commonly used facebow in clinical practice. Typically it is used in growing patients with decreased vertical dimension. The purpose of the facebow is to restrict the forward growth of the maxilla. The vector of force is below the occlusal plane producing both extrusive and distalising effects. Component parts:  molar tubes with headgear tubes  inner and outer bow soldered together in the center  A neck strap that is placed around the back of the neck to provide traction to the dentition.
  • 29.  Effects of cervical headgear:  to erupt the entire upper jaw  tends to move the upper jaw distally  Steepen the occlusal plane.  Expansion of the upper arch. Effect of different positions of the outer bow: when the outer bow is bent upwards: The forces that are produced are A distalising force to the upper teeth, which is good for correction of class II relation. When the outer bow is bent upwards, bringing it down to the occlusal plane tends to produce a negative moment that flattens the occlusal plane. Hence the steepening effect of the cervical headgear is nullified. Eruption of the entire upper arch tends to increase the mandibular plane angle and tends to worsen the class II skeletal relationship. this type is good for patients with forward growth rotation
  • 30. when the outer bow is bent downwards: Forces that are produced are     Positive moment on the occlusal plane is seen that tends to steepen the occlusal plane since the pull is below the Cres. Extrusive force and a distalising force. When the outer bow and inner bow are in the same level, no moment is produced and there is a net distalising and extrusive force. When the outer bow is shorter than the inner bow, the headgear strap hook is placed too far anteriorly. This results in a greater tendency to steepen the occlusal plane when the straps are engaged. The pull of the bow is further forward from the Cres and this tends to steepen the occlusal plane. When the outer bow is long, there is a tendency to flatten the occlusal plane.
  • 31. Kloehn headgear can be used to  distalise the entire maxillary segment  anchorage reinforcement  retraction of upper incisors  correction of class II molar relationship  Correction of crossbites.  Cervical headgear is used early in the treatment of class II malocclusions to inhibit forward displacement of maxilla or maxillary teeth, while rest of the dentofacial structures continue their normal growth. Advantages  Direction of pull is advantageous in treatment of short face class II maxillary protrusive cases with low MPA and deep bites. Disadvantages:  It normally causes extrusion of the upper molars. This movement is seldom desirable except in patients with reduced lower anterior facial height. It is contraindicated in patients with steep mandibular planes and in open bite cases.
  • 32. Studies on cervical headgear:  Cook et al in AJO 1994 studied growing children with Class II, Division 1 malocclusions who were treated with two different techniques: one group with orthopedic cervical headgear/lower utility arch (CHG/LUA) and another with cervical headgear alone. The outer bow was bent 200 upward and the inner bow was expanded. A force of 450 gms was used on either side. The authors found that CHG produced Class II correction through maxillary orthopedic and orthodontic changes, did not cause the upper molar to extrude beyond the amount seen with normal eruption, and did not produce an opening rotation of the mandible even in those patients who had dolichocephalic facial patterns.  Mirja Kirjavainen in AJO 1997 evaluated the effects of the cervical headgear therapy with an expanded inner bow to treat Class II malocclusion and dental arches.
  • 33.   The cervical headgear was used with a 10 mm expanded inner bow and a 15° upward bend of the long outer bow, 12 to 14 hours a day with a force of 500 gm per side. Class I relationships were achieved in all subjects in 15 months. At the same time, the maxillary and mandibular dental arches were widened. Melsen et al in AJO 2003 studied the intramaxillary molar displacement 7 years after treatment with Kloehn headgear and cervical traction. Two groups of 10 patients were studied. In one group, the outer bow was tilted upward by 200 and in another group, it was tilted down by 200. In the group that had the outer bow tilted downwards, molar correction was faster. In both the groups, the maxilla was moved backward and downward. A strong tendency of the molars to return to the key ridge was demonstrated, and there was no evidence that the Class I relationship obtained by extraoral traction was more stable than that obtained by functional or intramaxillary appliances.
  • 34. OCCIPITAL HEADGEAR:  The occipital headgear consists of a facebow which fits over the occiput of the head. The force generated by a high pull (occipital) has both distalising and intrusive forces since the force is exerted above the occlusal plane. Such forces are used in conditions where vertical control of the molars is important. As growth guiding appliance, a high pull headgear can decrease the vertical development of the maxilla, thereby allowing for autorotation of the mandible and maximizing the horizontal expression of mandibular growth. Occipital pull with short outer bow (force anterior to Cres) This results in a force system at the unit’s Cres with a moment that tends to flatten the occlusal plane and creates distalising and intrusive components.
  • 35. b.  occipital pull with force passing through Cres In this configuration, there is no moment that is created and hence there is no change in the cant of the occlusal plane. Intrusive and distal components of force are produced. c. occipital pull with long outer bow( force posterior to Cres)  The force system at the unit’s Cres has a moment that tends to steepen the occlusal plane. Intrusive and distalising forces are produced. This system might be required in class II open bite patients.
  • 36. Advantages:  These headgears can be used in patients with steep mandibular planes and in cases wherein mandibular growth is more vertical than horizontal. They can also be used in certain open bite cases caused due to excessive eruption of buccal teeth. Studies on high pull headgear:  Firouz et al in AJO 1992 examined the skeletal and dental effects of the high-pull extraoral appliance, when the resultant force was directed through the level of trifurcation of the maxillary molars. Patients wore the headgear for a 6-month period, an average of 12 hours a day. The authors found that by directing the force of the headgear approximately through the center of resistance of the maxillary molars, it was possible to translate the molars in the direction of the applied force. Hence both intrusion and distal movement of the molars can be achieved at the same time..
  • 37.  Burke and Jacobson in AJO 1992 evaluated vertical changes in growing patients with high MPA Class II, Division 1 malocclusions who were treated with cervical and occipital headgears applied from different angles relative to the occlusal plane. They found greater vertical changes in pts with cervical HG. The changes in occlusal plane between the two types of headgears were most significant. Posterior maxillary dentoalveolar changes between the two groups were significant.
  • 38. COMBINATION HEADGEAR. Combination headgears have both occipital and cervical traction springs. This is perhaps the most versatile type because the pull can be readily controlled by selecting the force level of the springs and by controlling the length of the outer bow. For distal translation of the upper posteriors, a distal traction is needed that passes through the Cres, neither above nor below. The combination type headgear will allow a distal force straight through Cres by having equal occipital and cervical components on the outer bow, which is angled upwards to allow the force to pass through the Cres.
  • 39. J PULL HEADGEAR:  This headgear consists of two separate curved hooks which are attached directly onto the maxillary archwire in the anterior region. This type of headgear is most commonly used for the retraction of the canines and incisors rather than for orthopedic purposes. J-hook HG is limited in use only with a maxillary fixed appliance and a continuous arch wire. It is preferable if all the teeth are included in the archwire. The intraoral point of attachment is directly to the maxillary archwire, distal to the lateral incisors. This HG is mainly used to retract and intrude the maxillary incisor teeth and to prevent or correct ‘gummy smiles’.
  • 40. ASYMMETRIC HEADGEARS: Haack&Weinstein AJO 1958:  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). 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. Small lateral forces on the molars are always developed by this eccentric design.
  • 41. REVERSE PULL HEADGEAR  Maxillary protraction is recommended for skeletal Class III patients with maxillary deficiency. Delaire and others used face mask for maxillary protraction. Petit later modified Delaire’s concept by increasing the amount of force generated and thus reducing the overall treatment time. In 1987, McNamara introduced the use of bonded acrylic expansion appliance with acrylic occlusal coverage for maxillary protraction. Turley improved patient co-operation by fabricating customized facemasks.
  • 42.  The principle of maxillary protraction is to apply tensile force on the circumaxillary sutures and thereby stimulate bone apposition in the suture areas; in doing so, the maxillary teeth become the point of force application, and the face (forehead, chin, zygoma) or occipital area becomes the anchorage source. Literature reveals that early treatment with a maxillary protraction appliance is effective in correcting the Class III malocclusion due to maxillary retrusion.
  • 43.  Class III skeletal patterns often exhibit a high incidence of deficient transverse maxillary growth and maxillary expansion is often the first treatment procedure. McNamara and Turley have recommended the use of bonded rapid palatal expansion appliance for several days before beginning protraction in order to facilitate maxillary movement. After active protraction of the maxilla, retention is vitally important in maintaining the treatment effects of the facemask. Petit suggested the Fränkel III regulator be used for 6 months postprotraction.
  • 44. Treatment effects of face mask:  The maxilla moves downward and forward with a slight upward movement in the anterior and downward movement in the posterior palatal plane as the result of protraction force; at the same time posterior teeth extrude somewhat. As a consequence, downward and backward rotation of the mandible improves the maxillomandibular skeletal relationship in the sagittal dimension but results in an increase in lower anterior facial height. This rotation is a major contributing factor in establishing an anterior overjet improvement. According to sung et al in AJO 1998, face mask produced an increase in the effective length of the maxilla and a decrease in the length of the mandible. Protraction groups show an inhibition of mandibular growth.
  • 45. Design and construction  An adjustable anterior wire with hooks is connected to the midline framework to accommodate a downward and forward pull on the maxilla with elastics. To minimize opening of bite as the maxilla is repositioned, the elastics are attached near the maxillary canines with a downward and forward pull of 300 to the occlusal plane. Maxillary protraction generally requires 300-600 gms of force per side. Patients are instructed to wear the appliance for 12 hrs a day.
  • 46. Design and construction of the anchorage system Banded palatal expansion appliance  In the mixed dentition, banded palatal expansion appliance is constructed by using bands fitted on the maxillary primary second molars and permanent first molars. Molar bands are joined by soldering a heavy wire (0.043 inch) to the palatal plate and a hyrax type screw is placed in the midline. The appliance is activated twice daily (0.25 mm per turn) for one week. In patients with constricted maxilla, activation is carried out for two weeks or more depending on the discrepancy. Bonded palatal expansion appliance  This appliance incorporates a hyrax type screw into a wire framework made from 0.040 inch that extends around the buccal and lingual surfaces of the dentition. The primary molars and permanent first molars are covered with acrylic. A separate wire is bent to cross the occlusion between the primary first and second molars and ends with a hook for protraction with elastics.
  • 47. Appliance design:  The facial mask consists of a forehead pad and a chin pad that are connected with a heavy steel support rod. A crossbow is connected to support this rod to which are attached rubber bands to produce a forward and downward elastic traction on the maxilla. The position of the pads and the crossbow can be adjusted simply by loosening and tightening set screws within each part of the appliance.  The orthopedic facial mask system introduced by McNamara in 1987 has a bonded RPE in addition to the facial mask and elastics. Protraction with expansion can also be done using a banded palatal expander, a quad helix, slow expansion etc
  • 48. SEQUENCE OF ELASTICS. SIZE At the time of delivery 3/8 ” After 2 weeks 1/2 ” Increased to a maximum of 5/16”   FORCE 8 oz 14 oz DURATION 2 weeks Young patients (4-9 years of age) should wear the mask on a full time basis except during meals. Duration is 4-6 months. They can be retained with only night time wear or with a maintenance plate, chin cup or FR III. In older patients, it is worn at all times except during school.
  • 49. Force application:  According to Delaire, Nanda et al in AJO 1978 and other biomechanical studies and clinical reports on maxillary protraction, upward and forward rotation of the maxilla occurs when protraction force on molars is applied parallel to the occlusal plane. This type of maxillary rotation can be minimized when the force is applied in the canine area, 20° to 30° below the occlusal plane. Nanda found that with the same line of force, different midfacial bones were displaced in different directions depending on the moments of force generated in the sutures. Kokich and Shapiro in AJO 1979 found that anterior positioning of the maxillary complex was associated with a small amount of counterclockwise rotation during treatment. Protraction of maxilla below the Cres produces counterclockwise rotation of maxilla. Hata et al in AJO 1987 found that the counterclockwise rotation can be counteracted by applying a heavy downward vector of force.
  • 50. FACE MASK WITHOUT EXPANSION    Baik (AJO 1995) studied on protraction with labiolingual stabilization of maxilla. He compared this with a group of patients with protraction and expansion using banded RME. His study was in a group of maxillary deficient children, 8-13 yrs of age. He found significantly greater forward movement of the maxilla (+2 mm) in protraction with RME compared to protraction with out RME (+0.9mm). In the same study, greater forward movement of the maxilla (+2.8mm) was found when protraction was initiated during maxillary expansion compared with protraction after expansion. This study shows that better results are obtained with protraction during expansion. Also, protraction without expansion is inferior. According to several authors, palatal expansion is used to disarticulate the maxilla and initiate cellular response in the circummaxillary sutures, allowing a more positive reaction to the protraction forces.
  • 51.  Orthopedic effects require greater forces than do orthodontic movements. Successful maxillary protraction can be achieved by using 300-500 gm of force per side in the primary and mixed dentition. Most studies recommend wearing the headgear for duration of 12 hrs/day. According to Hata et al, effective forward displacement of the maxilla can be obtained clinically by applying a force 5 mm above the palatal plane. In deep bite cases, a forward pull from the level of the maxillary arch with a concomitant anterior rotation of the maxilla aids in treatment. Several clinical studies report that a 300-450 forward and downward protraction force applied to the canine region produces an acceptable clinical response.
  • 52. Sutures involved in maxillary protraction:  Several circum-maxillary sutures play an important role in development of the naso-maxillary complex. A change in these sutures during treatment in the growing period occurs. The sutures are a. Frontomaxillary, b. Nasomaxillary, c. Zygomaticomaxillary, d. Zygomaticotemporal, e. Pterygopalatine, f. Intermaxillary, g. Ethmomaxillary, h. Lacrimomaxillary and i. Zygomaticofrontal.
  • 53.  Most of the orthopedic effects are seen within 3-6 months after maxillary expansion. Prolonged use of protraction forces results in dentoalveolar changes including mesial movement of maxillary molars and proclination of maxillary incisors. Studies have shown that the effects on the maxilla remained stable. In patients who were followed up after protraction, the anterior position of the maxilla was maintained post treatment.  Gallagher et al in AJO 1998 found that in the post treatment follow up for face mask therapy patients, the maxilla showed a relative relapse by not displacing forward as much as normal. The anterior rotation caused by treatment was negated. The mandible followed a normal downward and forward growth pattern.
  • 54. Treatment timing:  According to Kim et al in AJO 1999 and several other authors, treatment should be started as early as possible to produce a more significant response from protraction therapy. Treatment changes in the younger group are larger than those in the older group. Protraction face mask therapy is still effective but to a lesser degree in growing patients older than 10 years of age. The optimal timing for intervention is at the time of eruption of the upper central incisors. A positive overjet and overbite at the end of treatment appears to maintain the anterior occlusion at the end of treatment. Better skeletal and dental response is obtained in the primary and early mixed dentitions.
  • 55. Indications for facemask therapy     The facemask is a most effective tool for treating skeletal Class III malocclusion with a retrusive maxilla and a hypodivergent growth pattern. Patients presenting initially with some degree of anterior mandibular shift and a moderate overbite have an improved treatment prognosis. Correcting the anterior crossbite usually results in a downward and backward rotation of the mandible that diminishes its prognathism. The presence of an overbite helps to maintain the immediate dental correction after treatment. For patients presenting with a hyperdivergent growth pattern and a minimal overbite, a bonded palatal expansion appliance to control vertical eruption of the molars is recommended. During retention, a mandibular retractor or a Class III activator with a posterior bite block can be used for vertical control.
  • 56. CHIN CUP THERAPY  The objective of early treatment with a chin cup is to provide growth inhibition or redirection and posterior positioning of mandible. Force magnitude and direction.  There are two types of chin cup- the occipital pull chin cup that is used for patients with mandibular protrusion and the vertical pull chin cup that is used in patients presenting with a steep mandibular plane and excessive anterior facial height. Most studies recommend an orthopedic force of 300-500 gm per side (AJO 1987).  Patients are instructed to wear the appliance 14 hours/day. The orthopedic force is usually directed either through the condyle or below the condyle.
  • 57. HEADGEARS WITH OTHER APPLIANCES HEADGEARS WITH REMOVABLE APPLIANCES: Margolis acrylic cervico occipital anchorage:  Margolis in 1976 incorporated extraoral force with removable appliances for pts with class II malocclusions, using them both in active and retentive phases of treatment. The Margolis appliance is called an ACCO. Modified maxillary removable Hawley type appliance permits the use of extraoral forces against the maxillary dentition. Multiple ball end clasps and occlusal coverage can increase the resistance to dislodgement by extraoral traction. Margolis used this appliance to hold the torque correction achieved with fixed appliances. This appliance was later modified by the addition of 1 mm buccal tubes to the labial wire and soldering them vertically at the canine-lateral incisor embrasure to receive the Jhook extraoral force arms. An inclined plane was added to eliminate functional retrusion and free the mandible for all possible forward growth.
  • 58.  A new ACCO is made after extraoral forces and inclined plane have created a class I buccal segment. The ACCO should be worn both day and night with a minimum of 12 hrs nocturnal headgear wear. ACCO can be continued to be used as a retainer after active treatment and extraoral force can be applied as indicated with the ACCO to treat any residual sagittal abnormality or tendency to return to original class II relationship.
  • 59. Jacobson’s splint  Jacobson used a splint similar to the ACCO with extra oral traction for correction of mild class II malocclusions. The reduction in overjet and the sagittal discrepancy reduce the deforming action of the abnormal perioral muscle function. The force magnitude for this type of removable appliance must not be too great to prevent dislodgement of the appliance.
  • 60.  The direction of pull of the extra oral force should coincide roughly with that of the Y-axis or a line extending from the symphysis to a point 1.5 cm in front of the external auditory meatus. This prevents the unfavorable basal maxillary tipping and extrusion of teeth. The Jacobson craniomaxillary splint is used with occlusal coverage to aid in retention and to prevent maxillary eruption while allowing unimpeded upward and forward eruption of the mandibular buccal segment that assists in sagittal correction.
  • 61. Verdon combination appliance:  An appliance similar to Jacobson’s splint was used. The basic appliance of choice is a modified active plate. The major objective is to effect a change through a distalising influence on the maxillary arch leaving the mandibular arch alone. An occipital headcap is used to prevent tipping down the anterior palatal plane. A cervical strap can be used but the force values are significantly smaller, producing more dentoalveolar and less basal effects.
  • 62. Graber appliance:  It was used for the treatment of class II division I malocclusions. The direction of force is high and the appliance stands away from the molar and premolar areas to allow expansion of the arch. This acts similar to the buccal shields of Frankel appliance. This appliance works as an active retainer for class II correction maintaining individual tooth positions.
  • 63. HEADGEAR WITH FIXED APPLIANCES: Edgewise appliance:   Various types of headgears are used with the edgewise appliance depending on the type of malocclusion and the stage of treatment for effecting dental and skeletal changes. Kloehn type of headgear is the type most commonly used mainly to reinforce anchorage. In growing patients, it produces skeletal changes if high forces are used. The end of the outer bow is bent up at an angle of 150 to prevent tipping of molars. This produces opening of the bite due to extrusion of molars. Hence it should only be used in patients with normal or deep overbites. In patients with normal or low mandibular plane angles, kloehn face bow can be used to obtain skeletal corrections.
  • 64.     Straight pull headgear is used on the upper arch if extrusion of the teeth is not desired. This type is used on the upper arch during retraction of the canines and incisors. High pull headgear with facebow is used to intrude molars in selected cases of open bites. Intrusion of buccal teeth produces a rotation of mandible thereby closing the openbite and reducing the LAFH. High pull headgear using J-hook can be used in the anterior segment for deep bite correction and for correction of gummy smiles.
  • 65. Straight wire appliance:  When anchorage is critical, the anterior teeth are retracted by the use of a modified Asher’s face bow which can be hooked either to a neck strap to retract the lower or upper anteriors or an anterior high pull headcap to retract and intrude the upper incisors.  Ashers high pull facebow with headcap is used to retract the incisors using 12-15 oz of force.
  • 66. Begg appliance:  Extraoral forces are usually not required with begg since begg mechanics minimizes the need for anchorage conservation. However, headgears can be used in isolated cases for distalisation of teeth or when orthopedic control of maxilla is favored over extraction or orthognathic surgery. Such indications would include severe skeletal class II problems with high ANB differences combined with excessive maxillary protrusion. Headgear would also be indicated in nonextraction cases requiring distal positioning of the posterior teeth or maxilla to produce an acceptable anteroposterior dental and skeletal relationship.
  • 67. Level anchorage system:  High pull face bow headgear is used to the maxillary molar or a high pull J hook headgear attached to the maxillary area, with 1 pound pressure on each side, worn 12 hours per day by a growing patient will reduce the ANB approximately by 10. Anchorage space in the lower arch needed to correct the ANB angle is reduced by approximately 1 mm for each 6 months of headgear wear.
  • 68. HEADGEARS WITH FUNCTIONAL APPLIANCES Headgears with activator  Levin et al in AJO 1985 reported the use of a cervical headgear with the activator. A cervical HG with a long outer bow applying a force of 400 gms was used. It was concluded that activator cervical headgear therapy results in a simulation of normal mandibular occlusal development and a redirection of maxillary dentoalveolar development. Mesofacial and brachyfacial types appeared to respond most favorably to treatment.
  • 69.   Pfeiffer in AJO 1982 described the combination activator — cervical headgear therapy. They preferred to use cervical headgear, where necessary, for two reasons: (1) to extrude maxillary molars, and (2) to apply orthopedic traction to the maxilla and an activator to induce orthopedic mandibular changes, restrain maxillary growth, and cause selective eruption of teeth. Cura et al in AJO 1996 compared the effects of activator and activator with HG therepy. A high pull head gear was used with a force of 400 gms per side for 17 hrs a day. They found greater improvement in the sagittal base relationship in cases treated with combination therapy than in patients who were treated with activator alone.
  • 70.  Stockli and Teusher in their combination therapy said that vertical and sagittal control oh maxillary growth was essential in the management of class II patients. Their activator HG combination achieved control in all the three planes of space. A high pull HG was used for depression of molars and vertical control of the maxilla.
  • 71. Headgears with herbst appliance.  Was first reported by weislander in AJO 1984. It is indicated only in cases of severe class II MO in early mixed dentition. In order to transfer as much force as possible to the base of the maxilla, splints may be used with an attempt to distribute the force over the total dentoalveolar area for better anchorage purposes. Orthopedic forces in human beings, usually in the magnitude of 500 to 1,000 gm of pressure on each side were suggested. When the total maxillary dental arch is used as anchorage, forces up to 1,500 gm on each side can be applied without discomfort to the patient. In most cases treated in the mixed dentition, appliances were constructed for nighttime wear only, and 12 to 18 hours of wear gave maximum treatment effect. The orthopedic effect of treatment may increase if proper anchorage is used and if the appliance is worn 24 hours.
  • 72.   Weislander in AJO 1993 evaluated the effect of treatment and retention on a group of consecutive cases several years out of retention and to compare the initial changes during Herbst treatment with the long-term situation 8 years after treatment. An average increase of 2mm was found in the mandibular body length. Prolonged retention with activator was needed to minimize relapse. Findings indicated that maxillary sutural remodeling might be more receptive long-term to orthopedic treatment than the mandibular condylar growth process. Schiavoni in AJO 1992 evaluated the possibility of controlling vertical dimension by using Herbst appliance and high pull headgear in hyperdivergent facial patterns. The high-pull headgear had an orthopedic restriction of the maxillary vertical development rather than an effect on the sagittal plane. Elimination of anterior inferences by orthodontic repositioning of the front teeth and preventing extrusion of the posterior teeth allowed an anterior rotation of the mandible, with improvement of the sagittal correction and beneficial reduction in lower face height.
  • 73.  Rabie and Hagg in Sem Orthod 2003 investigated the effect of adding HG to the herbst appliance and in the retention period. A high pull HG whose outer bow was adjusted to be 300 above the occlusal plane was used. The HG delivered a force of 400-500 gms. Results showed that the maxillary restraint and improvement in jaw base was greater in patients who had HG during the treatment period. Rotation of the palatal plane was seen in the herbst group but not the HG- herbst group. The authors concluded that adding HG to the herbst resulted in increased orthopedic effect on the maxilla and a large increase in the jaw base relationship.
  • 74. Headgears with Bionator  Dahan et al in AJO 1989 described the use of a bioactivator with high pull headgear for treatment of class II division I malocclusion cases. High-pull headgear was adjusted to the buccal tube units of the multianchorage system. The headgear was worn every night (8 to 10 hours) during the first year of treatment. They concluded that the combination of a bimaxillary appliance with extraoral forces leads to rapid changes in the correction of Class II, Division 1 skeletal conditions.
  • 75. Headgears and Twin block  Parkin and sandler in AJO 2001 compared the effects of two modifications of twin block. The effect of twin block appliance modified by the incorporation of a high pull headgear and torquing springs positioned on the maxillary incisors was studied. The headgear force was directed at the Cres of the maxilla in an attempt to control the vertical position of the maxilla. Flying headgear tubes situated next to the maxillary second premolars were used to apply a force of 400 gm per side, worn for 120 hours per week.
  • 76.  They found that in pts with headgear, the maxillary plane appeared to have rotated in an anticlockwise direction. Vertical eruption of the maxillary molars was restricted by headgear. A restraint in the anteroposterior position of the maxilla was demonstrated. The authors concluded that the addition of high pull headgear in patients with twin block allowed effective vertical and sagittal control of the maxilla with no increase in LFH/TFH.
  • 77. Headgears with frankel appliance:  Owen et al in JCO 1985 modified the FR by adding posterior bite blocks and a headgear for the control of the posterior maxilla. A high pull headgear was used for posterior maxillary control. The modified function regulator appeared to offer advantages in combining functional jaw orthopedics with directional force headgear in the early comprehensive treatment of long face patients.
  • 78.  They suggested that the vertical dimension or anterior facial height (ANS-Me) could be held constant or even decreased through the holding or intrusion of the upper molars. Although no condylar growth was demonstrated in this study, there was a potential for increased mandibular growth.
  • 79. HEADGEARS FOR MOLAR DISTALISATION: According to Nanda et al  By directing the forces through the Cres of the maxillary molars, intrusion and distalisation of molars can be achieved.  An average of 500 gms was suggested to translate the molars distally and at the same time initiate maxillary changes that are normally associated with high force levels.  If the headgear is used for a short period of 6 months with good patient co-operation, significant dental improvement in the class II molar relation can be achieved.
  • 80. Disadvantages of headgear treatment: Samuels et al AJO 1996 in a review of orthodontic facebow injuries and safety equipment found that the cause of the injuries could be roughly grouped into four categories. 1. Accidental disengagement when the child was playing while wearing the headgear 2. Incorrect handling by the child during the fitting or removal of the headgear 3. Deliberate disengagement of the headgear caused by another child 4. Unintentional disengagement or detachment of the headgear during sleep.
  • 81. Assessment of patient compliance Cureton AJO 1993. The methods currently used to determine headgear wear are subjective. Some methods used are  molar mobility,  cleanliness of headgear tubes,  cleanliness of headgear strap,  ease of placement by patient,  questioning patient,  space creation between teeth,  molar positioning comparing pretreatment models and/or cephalograms,  the position of the junction of the inner and outer bow of the headgear compared with the previous appointment, and  Anchorage maintenance.
  • 82. Instructions to be given to the patient include:       Patients should be advised not to wear their headgear while playing. Before removing the face-bow, the patient must always remove the headgear first. Where a locking face-bow has been fitted, patients should check to make sure it is seated correctly. If any problems occur with the headgear, then patients should cease wearing it and return to see the clinician as soon as possible. If the appliance is detaching during sleep, the patient must cease wearing it and return to see the clinician. The patient and parent should also be advised that if any eye injury is suspected to have been caused by any part of the orthodontic appliance, however minor, then an immediate ophthalmologic examination is necessary because penetrating injuries may be relatively asymptomatic and immediate antibiotic therapy is required if any resultant infection is to be controlled
  • 83. Headgear timers  If the orthodontist had full knowledge of the actual amount of wear between appointments, this would be a significant boon to therapy. In addition, this could markedly increase patient compliance. Northcutt was one of the first to introduce a timing headgear. The timing headgear unit consists of a miniature electronic timer and is used with a digital readout meter. It was initially used with a cervical pull appliance, but was later available in a high-pull mode.
  • 84.     Selçuk type headgear-timer (STHT) was introduced by Enis Guray 1997 The Selçuk type headgear timer was reported to be 100% accurate, unaffected by intensity of force variables, reliable, easy to construct, safe, and inexpensive. Clinical tests showed a significant increase in headgear wear. An objective appraisal of extraoral force affects is enhanced by having a validating measurement of actual appliance wear. With the ability to control direction of force and to measure intensity, it is now possible to have an equally accurate measure of the third element of the triad —duration of wear.
  • 85. CONCLUSION  The choice of appliance should be based on the proper diagnosis of different aspects of the malocclusion and not because a particular appliance is thought to have a greater influence on modifying growth. Clinicians should be thoroughly familiar with the appliances they are using, including their potential benefits and limitations. They should also be aware of the effects of these appliances on the dentofacial structures when formulating a treatment plan for each individual patient. Regardless of the appliance used, there is a large and similar amount of variation in individual patient response to treatment.
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