30. Extra-oral anchorage (EOA) appliances-general description. Principles of action and design

Question 1

Extraoral anchorage appliances

Answer 1

• Anchorage points outside oral cavity=>
• Exert orthopaedic forces on teeth, dental arches, and jaws=>
• Dental and skeletal changes

Question 2

How orthodontic and orthopaedic forces differ in effects

Answer 2

• Orthodontic forces=>light forces (50-100g)=>
• Tooth movement
• Orthopaedic forces => heavier (300-500g) =>
• Skeletal changes affecting magnitude and direction of bone growth

Question 3

Planes of space extraoral anchorage appliances produce their effects

Answer 3

Sagittal, transverse, and vertical

Question 4

Basis of orthopaedic appliance therapy

Answer 4

• Intermittent forces of very high magnitude alter jaw growth=>
• Modify bone apposition patterns at periosteal sutures and growth sites
• Worn intermittently for about 10-12 hours per day

Question 5

Why tooth movement reduced with orthopaedic appliances

Answer 5

• Intermittent application allows replenishment of normal circulation=>
• Focuses effects on skeletal changes rather than tooth movement

Question 6

Required magnitude of force for skeletal changes

Answer 6

• Extraoral forces of 400-600g per side required to achieve skeletal changes=>
• Compress periodontal ligament=>
• Hyalinisation and prevents tooth movement while maximizing skeletal changes

Question 7

How duration of force application affects orthopaedic changes

Answer 7

• Intermittent heavy forces applied for 12-14 hours/day most effective=>
• Less damaging to teeth and periodontium compared to continuous heavy force application

Question 8

Why direction of force important in orthopaedic treatment

Answer 8

• Must pass through center of resistance (COR) of skeletal structures for maximum effectiveness
• Should be appropriate to achieve desired skeletal effect

Question 9

Significance of center of resistance (COR) in orthodontic treatment

Answer 9

• Crucial point for effective force application
• For molars=>located at mid-root region, 1-2mm apical to furcation area
• Forces through or near COR cause specific movements=>
• Bodily movement, distal root tipping, or distal crown tipping

Question 10

COR of maxilla location and how force application affects it

Answer 10

• Above apices of premolar teeth=>
• Posterosuperior aspect of zygomaticomaxillary suture
• Forces through this point=> translation of maxilla in distal direction,
• Forces above or below=>rotation

Question 11

Patient age importance in orthopaedic appliance therapy

Answer 11

• Mixed dentition period advisable to take advantage of’ growth potential
• Treatment may need to continue until completion of adolescent growth to prevent relapse=>
• Re-expression of patient’s fundamental growth pattern

Question 12

Optimal time of day for applying extraoral forces

Answer 12

• During evening and night=>
• Increased release of growth hormones and other growth-promoting endocrine factors=>
• Associated w/ skeletal growth and follow circadian pattern

Question 13

Most widely used orthopaedic appliances

Answer 13

• Headgear=>exerts force on maxilla
• Reverse Pull Headgear=>force on both maxilla and mandible simultaneously
• Chin Cup=>force on mandible

Question 14

Components that make up a headgear in orthodontics

Answer 14

• Extraoral Anchorage=>provides external point of attachment for applying force
• Facebow=>redistributes applied force to teeth and jaws
• Pull-Force Elements=>connects facebow to head cap and generates necessary force
• Intraoral Support Unit=>anchors facebow inside mouth=>
• W/ molar bands or tubes

Question 15

Types of head caps

Answer 15

1. Occipital Pull (Straight Pull)
2. Parietal Pull (High Pull)
3. Cervical Pull (Low Pull)
4. Combination Pull

Question 16

Occipital Pull (Straight Pull)

Answer 16

• Anchorage Location=>Occipital region
• Forces Produced=>distal and some intrusive forces
• Indications=>Class II long-face patients and open bite cases
• Contraindications=>deep bite patients

Question 17

Parietal Pull (High Pull)

Answer 17

• Anchorage Location=>Parietal region
• Forces Produced=>Intrusion of upper molar and maxilla=>
• Decreases lower facial height
• Indications=>Class II long-face patients and open bite
• Contraindications=>Deep bite patients

Question 18

Cervical Pull (Low Pull)

Answer 18

• Anchorage Location=>Neck
• Forces Produced=>distalisation and extrusion of upper molars=>
• Increase lower facial height
• Indications=>class II deep bite
• Contraindications=>Long-face syndrome, open bite patients, gummy smile

Question 19

Combination Pull

Answer 19

• Anchorage=>combination of cervical and occipital
• Forces Produced=>distal force straight through center of resistance=>
• w/ equal occipital and cervical components

Question 20

J’ hook in headgear

Answer 20

• Extraoral force transmitted from head cap to hooks soldered on arch wire=>
• By two separate wires on each side=>
• Direct force application more precisely

Question 21

Structure and function of a facebow

Answer 21

• Outer bow
• Inner bow
• Junction

Question 22

Pull-force element in headgear

Answer 22

• Provides force necessary to achieve desired orthodontic effects
• Connects facebow to head cap and composed of springs, elastics, or other stretchable materials
• Modern headgears=>use traction modules w/ pre-adjusted maximum pull force that disengage automatically if over-activated=>
• Prevent whip-back of facebow

Question 23

Role intraoral support unit plays in headgear

Answer 23

• Anchors facebow w/in mouth=>
• Via buccal tubes on orthodontic molar bands or molar tubes
• In some cases=>inner bow directly inserted into acrylic base of a removable appliance

Question 24

Principles of using headgears

Answer 24

• Center of Resistance of Dentition=>
• Inner bow attached to maxillary first molars via buccal tubes=>
• Force acting on molars displaces them
• COR of molars determines movement type
• Center of Resistance of Maxilla=>
• Above apices of premolar teeth at posterosuperior aspect of zygomaticomaxillary suture=>
• Produce maxilla translation or rotation depending on direction
• Point of Origin of Force=>
• Occipital Headgear=>superior and distal force
• Cervical Headgears=>inferior and distal force
• Point of Attachment=>
• Hook on distal end of outer bow where force generating unit attaches=>
• Altering point of attachment or angle between inner and outer bow=>
• Changes direction of force on maxilla and dentition

-Movement types-(bodily movement, distal root tipping, distal crown tipping).

Question 25

Uses of Headgears

Answer 25

* **Orthopaedic Effect**=>Forces applied on maxilla to restrict downward and forward growth * **Anchorage Augmentation**=> Extraoral forces reinforce anchorage when intraoral sources insufficient * **Distalisation of Molars**=> Extraoral forces effectively move upper molars distally=> * Corrects molar relation, gaining space for crowding correction, or anterior retraction. * **Molar Rotation**=> Inner bow adjustments produce rotational forces on molars * **Space Maintenance**=> Prevents mesial movement of molars=> * Maintaining arch length. ## Footnote - Daily wear of 8 hours is typically sufficient

Question 26

Protraction mask in orthodontics

Answer 26

* Aka Reverse pull headgear" or "protraction headgear," => * **Applies force on maxilla and mandible simultaneously**=> * **Correct Class III malocclusion**

Question 27

Primary principle behind protraction mask's function

Answer 27

* Pulling force on maxillary structures w/ reciprocal pushing force on forehead or mandible=> * Forward movement (protraction) of maxilla and maxillary arch=> * Simultaneously mesial movement of maxillary posterior teeth and caudal (downward) traction on mandible (retraction)

Question 28

Indications for using a protraction mask

Answer 28

* **Prognathic mandible** (forward-positioned lower jaw) * **Retrognathic maxilla** (backward-positioned upper jaw) * *Combination of both conditions*

Question 29

Contraindications for using protraction mask

Answer 29

* **Severe skeletal disharmonies** * Mandibular deviation=< growth asymmetry between left and right condyle

Question 30

Age at which protraction mask most effectively applied

Answer 30

* **4 to 7 years=>**most effective * Skeletal changes quicker w/ less daily wear * **7 to 10 years=>**still effective but less * **10 to 14 years=>**possible but w/ poorer results compared to younger age groups

Question 31

Importance of treating Class III malocclusion at early age

Answer 31

* Prevent irreversible changes to hard and soft tissues * Correct skeletal discrepancy between upper and lower jaw=>normal growth * Improve occlusal function * Simplify major treatments during teenage years * Enhance facial aesthetics=> psychosocial development

Question 32

Length and frequency protraction mask worn daily

Answer 32

* **12-22** hours/day * **12-18** months=> * Depending on jaw and bone growth during this period ## Footnote -14-16 hours per day sufficiently effective.

Question 33

Components of protraction mask

Answer 33

* **Face Frame**=>vertical and horizontal metal bars * **Vertical bar, single/double, and horizontal bar** has hooks for elastics * **Forehead Pad**=>support on forehead * **Chin Cup**=>support on chin * **Intraoral Support Unit**=>occlusal bite planes and lingual arches molded to molar bands=> * w/ hooks for attaching extraoral elastics * Acrylic bite planes cover posterior teeth in maxillary arch and reinforced w/ transpalatal bar or expansion screws

Question 34

How extraoral elastics function w/protraction mask

Answer 34

* **Forward traction on upper arch**=> * *Connect hooks on bite plane to transverse grid of face mask*=> * Force for maxillary protraction

Question 35

Types of Face Masks

Answer 35

* Protraction Headgear by Hickham * Face Mask of Delaire * Tubinger Model * Petit Type of Mask

Question 36

Types of chin cup in orthodontics

Answer 36

* Occipital Pull Chin Cup * Vertical (Parietal) Pull Chin Cup

Question 37

Occipital Pull Chin Cup

Answer 37

* Anchorage from **occipital region** * Pull force directed **vertically and sagittally=>** * Behind and under **mandibular condyle=>** * **Rotates mandible backward and downward=>** * **Bite opening** * Indications=>**Class III w/ mild to moderate mandibular prognathism or normal overjet**=> * *& slightly protrusive lower incisors*

Question 38

Vertical (Parietal) Pull Chin Cup

Answer 38

* Anchorage from **parietal region of head** * Pull force directed **vertically through maxillary molars’ area=>** * **Molar intrusion** * Indications=>**steep mandibular plane angle=>** * Excessive anterior facial height + skeletal open bite

Question 39

Biomechanical considerations when using protraction mask

Answer 39

* **450g force per side required for skeletal changes** * *Direction of Force=>**15-20° downward pull to occlusal plane produces forward translatory motion of maxilla***=> * If Force parallel to occlusal plane=> * Forward translation and upward rotation of maxilla

Question 40

Recommended force magnitude and duration of wear for chin cups

Answer 40

* **150-300g** force per side=> * Over next **2 months**, force is gradually increased to **450-700g** per side. * Use **12-14 hours/day** to achieve desired results