Removable Appliances

Question 1

What is the force needed for tipping tooth with a spring?

What diameter springs for buccal and palatal springs and how much activation is needed for each?

Answer 1

• 25-50 g of force
• buccal 0.7mm spring activate 1-2mm
• palatal 0.5mm spring activate 3mm

Question 2

What types of bows are used and what diameters are they?

Answer 2

• Robert’s retractor (buccal arms in tubing) 0.5mm (3mm activation) - flexible so good for larger OJ
• Labial bow with U loops 0.7mm (1mm activation by closing U) - rigid good for small OJ

Question 3

What movement can be achieved with screws?

Answer 3

• Used when teeth to be moved also need retention with clasps
• 0.2mm for each turn of key
• turned 1 or 2 times a week giving 1 or 2mm movement a month

Question 4

What can be used to procline incisors?

Answer 4

• Z-spring 0.5mm (1-2mm activation)
  good retention needed
• Screw appliance - good when proclaiming 4 incisors

Question 5

What can be used for mesial/distal movement of incisors, premolars and canines?

Answer 5

• Palatal finger spring (0.5mm) should lie at gingival margin and point of application at right angled to intended direction of movement
• Buccal canine retractor (0.7mm)
• Screw appliance to move molar distally - screw positioned to open anteroposteriorly

Question 6

What can be used for buccal movement of premolars?

Answer 6

• T spring (good retention required)

Activated by pulling the spring away from the acrylic

Question 7

What can be used for buccal movement of molars?

Answer 7

• Screw can be used to correct crossbite

Question 8

What retention components can be used?

Answer 8

• Adams clasp (0.7mm)
• Southend clasp on upper 1-1 for anterior retention (0.7mm)
• Labial bow on upper 2-2 for anterior retention (0.7mm) (incisors need to be proclined)

Question 9

When would you need an anterior bite plane?

Answer 9

Used when OB needs reducing (buccal segment erupts)

Question 10

When would you need a posterior bite plane?

Answer 10

When occlusal interferences need to be eliminated when correcting a Crossbite?

Question 11

Anchorage definition

Answer 11

Source of resistance to the forces generated in reaction to the active components. This reaction force is dissipated over the teeth which are contacted by the appliance

Question 12

Types of anchorage

Answer 12

-Simple anchorage - active movement of one tooth vs tooth of larger root surface area
- Compound - two or more teeth used as anchorage
- Reciprocal anchorage - two groups of teeth pitted against each other resulting in reciprocal movement
(- Extra oral anchorage- prevents forward movement of the anchor (upper buccal) teeth) [200-250g for 10-12h per night]

Question 13

Why does direction of headgear force need to be considered?

Answer 13

• Direction of force below occlusal plane as well as distal movement also extrudes upper molars and increases vertical dimension (acceptable in its with reduced VD)
• Direction of force above occlusal plane as well as distal movement also intrudes upper molars and decreases VD
• A combination pull - may act along the curve of speed and therefore not affect VD therefore commonly used

Question 14

What instructions on wear of removable appliances?

Answer 14

• Pt should wear appliance all day and night
• Pt should remove appliance for sport
• Pt should clean teeth and appliance after each meal
• Pt should be able to insert appliance
• Pt should avoid hard and sticky food
• If appliance breaks pt should return to emergency clinic

Question 15

How often do pt need recall for removable appliance?

Answer 15

• 4 weeks for reactivation

- Check tx plan, OH, loss of anchorage (by recording OJ and molar relationship), tooth movement, retention

Question 16

Problems with removable appliances?

Answer 16

• Slow rate of tooth movement
• Frequent breakages
• Appliance becomes loose
• Anchorage loss - part time wear, forces exerted by active components exceed anchorage resistance
• Palatal inflammation