Brief discussion on removable appliances, various types of clasps, their indications and uses. Various forms of removable appliances along with their indications and clinical uses

1. O R T H O D O N T I C S
F I N A L Y E A R B D S
REMOVABLE APPLIANCES

2. MODE OF ACTION
 Following types of tooth movements occur:
 Tipping
 Movement of blocks of teeth
 Influencing the eruption of opposing teeth
 Flat anterior bite plane
 Buccal capping

3. INDICATIONS FOR USE OF REMOVABLE
APPLIANCES
 Adjunct to fixed appliance treatment
 Extraoral traction to segments of teeth or entire arch to help achieve
intrusion/ distalisation
 Arch expansion
 Development of buccal segment teeth
 Disocclusion of arches
 Space maintainers
 Retainers – allow settling of occlusion

4. ADVANTAGES AND DISADVANTAGES
ADVANTAGES DISADVANTAGES
Can be removed for tooth
brushing
Appliance can be left out
Palatal coverage increases
anchorage
Only tilting movements possible
Easy to adjust Good technician required
Less risk of iatrogenic damage Affects speech
Acrylic can be thickened to form
anterior bite plane
Intermaxillary traction not
possible
Useful as retainer or space
maintainer
Lower removable appliance are
difficult to tolerate
Can be used to transmit forces to
blocks of teeth
Inefficient for multiple individual
tooth movements

5. DESIGNING REMOVABLE APPLIANCE
 Four components (A.R.A.B):
 Active
 Retentive
 Anchorage
 Base plate

6. CENTER OF RESISTANCE VS. CENTER OF
ROTATION
 Center of Resistance- Located 1/3 to ½ of distance from
alveolar crest to root apex. Forces passing through it
cause bodily tooth movement. Influenced by number of
roots, root surface area and level of alveolar bone heights
 Center of Rotation- Point around which tooth rotates

7. ACTIVE COMPONENTS
 Springs
 Force is proportional to radius of wire (by power 4), spring
deflection on activation and, inversely proportional to length
of wire (by power 3)
 Light force over long activation range is preferred
 Coils incorporated to increase wire length
 Smallest diameter wire used is 0.5 mm
 Spring is adjusted close to gingival margin for more
controlled tooth movements

8. ACTIVE COMPONENTS
 Screws
 Direction of tooth movement determined by position of screw
 Bulky and expensive
 Each quarter turn of screw expands plate by 0.25 mm
 Activation limited by PDL
 Elastics
 Classified by size ranging from 1/8” to ¾” and force they deliver 2 oz, 3
oz, 4.5 oz
 Selection based on root surface area of teeth to be moved and the
distance over which they stretch

9. RETENTIVE COMPONENTS
 Adams Clasp
 Designed to engage undercuts on mesial and distal surfaces on
buccal aspects of erupted first permanent molar
 Should engage 1 mm of the undercut
 For molars, 0.7 mm wire used. However, for premolars,
canines, central incisors and decidous molars, 0.6 mm wire
used
 Versatile and easily adapted
 Extra-oral traction tubes, labial bows or buccal springs can be
soldered to the bridge of the clasp
 Hooks or coils can be fabricated in the bridge of the clasp
 Double cribs can be constructed

10. OTHER METHODS OF RETENTION
South End Clasp Ball End Clasp
Plint Clasp Labial Bow

11. BASE-PLATE
 Can either be a passive or active component of the appliance
 Self cure or heat cure acrylic – commonly self cure unless appliances with
additional strength are needed
 Anterior bite- plane
 Overbite correction by eruption of lower lower buccal segment teeth
 Formed by increasing the thickness of the acrylic plate behind the upper incisors,
lower teeth occlude here. Used for overbite correction OR elimination of possible
occlusal interferences

12. BASE-PLATE
 Buccal Capping
 Indicated when overbite is decreased AND when occlusal
interferences need to be eliminated
 Produced by covering the occlusal surfaces of posterior teeth
 Acrylic should be as thin as possible to avoid patient
discomfort

13. COMMONLY USED REMOVABLE APPLIANCES
Z- SPRING SCREW EXPANSION APPLIANCE
NUDGER APPLIANCE ELSAA HAWLEY RETAINER

14. COMMON PROBLEMS DURING TREATMENT
 Slow rate of tooth movement- 1 mm/ mo in children
and less than that in adults
 Frequent breakage of appliance
 Anchorage loss
 Palatal inflammation

15. Q U E S T I O N S ?
THANK YOU