WELLCOME

ORTHOPEDIC APLIENCES•'orthopedic therapy' is aimed at the correction of skeletal imbalance with thecorrection of any dentoalveolar malocclusion being of less importance, in which little or no tooth movement is desired. Therefore, orthopedic forces are heavier (= 400 gm) when compared to orthodontic forces (50-100 gm).

THE PHILOSOPHY OF EXTRAORAL FORCE

• a. Growth modification• b. Camouflage treatment• c. Surgical correction• Growth modification is, by far, the best option

if possible. Growth modification helps in altering the expression, direction and magnitude of growth, thus bringing about favorable jaw growth.

BASIS FOR ORTHOPEDIC APPLIANCES

• Amount of Force• The force magnitude should be h.igh i.e, at least greater than

400 gm (400-600 gm) per side to a maximum total of 2-3 Ib to make sure that only skeletal and no dental movement takes place.

• Duration of Force• According to most authors, intermittent forces produce skeletal

change whereas continuous forces produce dental movement. Extraoral appliances should be worn

for about 12-14 hours/day to bring about the desired effect.

Direction of Force• The direction of force application should be such as to

maximize the skeletaleffect. A favorable skeletal affect is seen when a force is directed posterioriy and superiorly through the center of resistance of the maxilla. The extra oral anchor unit can be cervical oroccipital to produce a low or high force vector. The length of the outer bow can also be altered to change the force vector. A cervical headgear produces extrusion of the molars along with distalization, whereas an occipital attachment produces intrusion, which is favorable in Class IIcorrection.

• Age of the Patient• Orthopedic appliances are most effective during the mixed

dentition period as it takes advantage of the prepubertal growth spurt. effect.

• Timing of Force Application• There is evidence that there is an increase in

the release of growth hormones more during the evening and night and is associated with the sleep onset. Therefore, it is advisable for the child to wear the headgear in the evening and throughout the night. Generally the child is more likely to wear the appliance at night.

ORTHOPEDIC APPLIANCES

• 1. Headgear• 2. Facemask• 3. Chin cup

HEADGEAR• Headgears are the most common among all the orthopedic

appliances. They are ideally indicated in patients with excessive horizontal growth of the maxilla with or without vertical changes along with some protrusion of the maxillary teeth, reasonably good mandibular dental and skeletal morphology.

• They are most effective in the pre-pubertal period.• Headgears can also be used to distalize the maxillary dentition

along with the maxilla. They are an important adjunct to gain or maintain anchorage.

• Components• 1. Force delivering unit-face bow, J hook.• 2. Force generating unit.• 3. Anchor unit-head cap, neck strap

Face Bow

• One of the most important components, which help in delivering extraoral force to the posterior teeth. The face bow consists of the following.

• Outer BowlWhisker Bow• It is made up of round stainless steel wire 0.051" or 0.062"

in dimension and is contoured around the face.• The outer bow may be:• 1. Short-outer bow is shorter than inner bow • 2. Medium-outer bow is the same length as the inner bow .• 3. Long-outer bow is longer than inner bow

Inner Bow

• It is made up of 0.045" or 0.052" round stainless steel wire and inserts into the round buccal tube on the maxillary first molars. The inner bow is adapted according to the shape of the arch. 'stops' in the form of 'U' loop, bayonet bends and friction stops are placed in the bow mesial to the buccal tube to prevent it from sliding too far distally through the tube.

• Junction• It is the point of attachment of the inner and outer bow,

which may be soldered or welded. It is usually positioned at the midline of the two bows, however, it may be shifted to one side in case of asymmetric face bows.

• Force Generating Unit• This connects the face bow to the anchor unit and delivers

the force to the teeth and the underlying skeletal structures. The force element may be springs or elastics. Springs are preferred as they provide a constant force whereas elastics undergo force decay.

• Anchor Unit• This is in the form of a head cap or a neck strap, which

makes use of anchorage from the skull or back of the neck respectively. A combination of the two may also be used.

Type• Headgears• They can be divided as follows• i. According to direction of force:• • Distal force• • MesiaI force• ii. According to location of anchor unit:• • Cervical pull• • Occipital pull• • High pull (Parietal)• • Combination pull

Cervical Headgear

• The anchor unit in this headgear is the nape of the neck. It causes extrusion and distalization of the molars along with distal movement of the maxilla.

• Indications• 1. Short face, Class IImaxillary protrusive cases with a low mandibular plane

angle and deep bite (true).• 2. Anchorage conservation. The forward movement can be resisted better if the

anchor molars are supported further using the forces generated by the cervical headgear.

• 3. Early treatment of Class II malocclusion as it helps to distalize the maxilla and correct Class II molar relationship.

• Contraindications• 1. Open bite cases• 2. High mandibular plane angle• 3. Long face cases with an increase in lower anterior face height.

Biomechanics of Headgear• An understanding of the biomechanics helps the clinician to

determine the force systems that need to be applied to produce the desired clinical effects. The line of action of force is the direction in which the force acts. The relationship of the line of force action to the center of resistance of the maxilla or first molar determines whether translation or rotation takes place.

• When a force does not pass through the center of resistance of the maxilla/molar, a moment is produced.

• The magnitude of the moment is determined by the product of the force magnitude and the perpendicular distance from the line of force to the center of resistance.

• The direction of the line of force can be changed by adjusting the length of the center bow or by bending the outer bow up and down to produce the desired clinical effect.

Treatment Effects• Skeletal Effect• The maxillary sutures namely the frontomaxillary, zygomaticotemporal,

zygomaticomaxillary and pterygopalatine sutures are the most important growth sites for development of maxilla. Therefore, to alter the maxillary growth, the headgears act by compressing the sutures thus restricting the normal downward and forward growth of the maxilla, while at the same time the mandible is allowed to grow normally.

• Dental Effect• Headgear being a tooth-borne appliance, produces certain dental effects

along with a skeletal change. Headgears usually cause distalization of the maxillary molars. Along with this, extrusion or intrusion of the molar may also be seen if the extraoral attachment is cervical or Occipital respectively. In most skeletal ClassII problems a cervical headgear is not desired as the extrusion of the maxillary molar caused by the infenorly directed force which causes downward and backward mandibular rotation, thus worsening the problem.

Uses of Headgears

1. To restrain the forward and downward growth of the maxilla and redirectioning maxillary growth.

2. Molar distalization: Headgear may be used to distalize the maxillary molar to correct the ClassII molar relationship or to gain space for relief of crowding.

3. Headgears can be used to reinforce molar anchorage in high anchorage cases. Headgears should be worn for at least 10 hr / day with a minimum force of 300 gm per side.

4. Headgear is an effective means of maintaining arch length by preventing mesial migration of molars.

5. Molar rotation can also be brought about with the inner bow of the headgear.

FACEMASK• Class III malocclusion is usually a result of a combination of maxillary

deficiency and mandibular excess. Growth modification for Class III problems is the

• reverse of Class Il, i.e. treatment involves restriction of mandibular growth along with downward and forward maxillary growth. When headgear applies a distal force to the maxilla, compression of the maxillary sutures can inhibit forward maxillary growth. Likewise, pulling the maxilla forward and separating the sutures should stimulate forward growth of the maxilla. Headgears which cause a forward pull on the maxilla are, therefore, called reverse pull headgear. Facemask.

• A facemask works on the principle of pulling the maxillary structures forward with the help of anchorage from the chin or forehead or usually both. A forward maxillary pull is applied with the help of heavy elastics that are attached to hooks on the rigid framework.

Indications1. Mild to moderate ClassIII skeletal malocclusion due to

maxillary retrusion, reverse pull headgear works best in young, growing children (around 8 years).

2. Ideal patients for facemask should have:• Normal or retrusive but not protrusive maxillary teeth as

facemask causes forward movement of the maxillary teeth relative to the maxilla.

• Short or normal, but not long, anterior vertical facial dimensions, i.e. a hypodivergent growth pattern.

3. Correction of postsurgical relapse after osteotomies.4. Selective rearrangement of palatal shelves in cleft patients

Parts of a Facemask Usually, a facemask is made up of the followingcomponents:1. Meta I framework2. Chin cup/pad3. Forehead cap4. lntra-oral appliance5. Heavy elastics

Biomechanical Considerations• The maxilla can be advanced 2-4 mm forward over a period of 8-12

months. The amount of maxillary movement is influenced by a number of factors like:

a. Amount of force Successful maxillary protraction can be brought about by 300-500 gm of force per side in the primary or mixed dentition.

• b. Direction of force According to most authors, a 15- 20° downward pull to the occlusal plane is required to produce forward maxillary movement. In most cases of maxillary deficiency, maxilla is deficient in the vertical plane as well, therefore, a slight downward, direction of force is usually desirable. The line of force passes below the center of resistance of the maxilla producing a counter-clockwise moment on the maxilla and dentition. This results in a possible extrusion of maxillary posterior teeth leading to a downward and backward rotation of the mandible.

• However, in patients with increased anterior facial height, downward pull is contradicted.

c. Duration of force A review of literature shows duration to vary between 3 and 16 months. On an average at least 8-12 months of wear is required to produce the desired effect.

d. Frequency of use 12-14 hrs/day.• Age of patient Optimal results are seen when facemask is used in the

primary or early mixed dentition period. An optimal time to intervene an early Class lII malocclusion is at the time of eruption of permanent maxillary central incisors. The anchor molars are also erupted by this time.

f. Anchorage systems Palatal arches or palatal expansion appliances may be used as anchorage for maxillary protraction. Various authors recommend palatal expansion before protraction as expansion is supposed to "disarticulate" the maxilla making it favorable to respond to protraction forces.

CHIN CUP

• It is an extr-aoral orthopedic device, which is useful in the treatment of Class III malocclusions that occurs due to a protrusive mandible but a relatively normal maxilla.

• Chin cup therapy attempts to retard or redirect the growth of the mandible in order to obtain a better antero-posterior relation between the two jaws.

Philosophy of Chin Cup Therapy

• Mandible grows by apposition of bone at the condyle and along its free posterior border. Condyle is not a growth center and condylar growth is largely a response to translation of surrounding tissues.

• This contemporary view offers a more optimistic view of the possibilities for growth restraint of the mandible, as with chin cup therapy.

Line of Direction of Force

• There are two ways to use the chin cup:• 1. Line of force acting directly through the condyle with the intent of impeding

mandibular growth in the same way that extraoral force against the maxilla impedes its growth. This method causes no opening of the mandibular plane angle.

• 2. Line of force acting below the condyle :• Chin is rotated downward and backward• Less force is required• Increase in facial height is achieved for a decrease in the prominence of the

chin.• 3. Vertical force on the chin:• Decrease in mandibular plane angle• Decrease in gonial angle• Increase in posterior facial height.

• Magnitude of Force• Most authors recommend a force of 300-600

gm/side.• Initially a lower force level (about 150 gm) may

be advised for the patient to get used to the appliance.

• Duration of Wear• A maximum of 12-14 hr/day of chin cup wear is

recommended.

Effects of Chin cupExtraoral force of the chin cup, directed against the mandibular growth. However,

most human studies have failed to conclusively prove that chin cup inhabits mandibular growth. However, the following effects are seen.

• a. Redirection of mandibular growth in a downward and backward direction.• b. Remodeling of the mandible and a decrease in mandibular plane angle and

gonial angle• c. Lingual tipping of lower incisors.• d. Improvement in skeletal and soft tissue profile.Therefore, chin cup works well in patients with reduced or normal lower anterior

face height but is contradicted in long face patients.• According to TM Craber, ideal patients for chin cup therapy are those suffering

from:• • A mild skeletal problem with the ability to bring the incisors.end-to-end or

nearly so.• • Short vertical face height• • Normally positioned or protrusive, but not retrusive lower incisors.

Types of Chin Cup

• 1. Occipital puIl chin cup derives anchorage from the occiput region. This is used in Class III cases with mild to moderate mandibular prognathism, who can bring their incisors in an edge-to-edge position at centric relation. Patients with short anterior facial height also benefit from this type of chin cup. This is the more commonly used chin up.

• 2. Vertical pull chin cup derives anchorage from the parietaI region. It is indicated in high angle cases or long face patients as it helps to close the angle of the mandible and increase the posterior facial height.

• Commercially Available• • Soft Elastic appliance• • Hickham-type appliance• • Unitek design• • Summit design

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