Orthodontics : 2/removable Appliances : Construction And Design /first Semester

Front 1

Define " removable appliance "

Back 1

a term generally used to describe appliances consisting of an acrylic base plate that is held in place with clasps , and that commonly incorporate active components such as springs or expansion screws

Front 2

What are removable appliacnes used for ?

Back 2

for the treatment of simple malocculsion where teeth have to be tipped about a fulcrum close to the middle of the root

Front 3

Components of removable appliacne

Back 3

1) pressure source ( Active components ) to produce the desired movments
2) Dispersal of the force to the anchorage ( Anchoragne components )
3) Clasping requirments for the retention ( Retneitve components )
4) Baseplate ( to hold all the componetns togeather )

Front 4

What are the pressure soruces ? ( Active componets types ? )

Back 4

1) Springs
2) Labial Bow
3) Screws

Front 5

1) springs

Back 5

1) made of stainless steel wire contain :
18% --> chromium 8% --> Nickel

2) Elasticity : the propriety which enables a material to return to its original shape and dimension

3) Mallebaility : the proprety of a metal to be deformed by compression without cracking

4) tastless

5) Immune to corrosion : chromium forms a surface layer of chromium oxide which prevent corrosion

Front 6

Factor of Deflection forumla

Back 6

D = PL^3/T^4
d = is the amount of deflection
P = is the amount of pressure
L = is the length of the spring
T = is the thickness = diameter

According to this forumla :
1) D will be double when P is doubled D:P 1:1
2) D will increasse by 8 times if the L of the spring is doubled
3) D will increasse by 16 times if the T is halved

Thickness + ==> D - ==> pressure +
Length + ==> D + ==> pressure -

Front 7

Cantilever spring

Back 7

Incorpation of coils :
-increase the effective length of the spring and so increase their deflection

coil conditons :
- for the maximal effect they should
1) be made reasobnely large ==> 2.5 mm diameter .
2) placed close to the attachment point of the spring

point of contact of the spring :
- when a tooth is contacted by a spring at a single point , it'll move in the direction of the resultant force which is prepandicular to the tangent at the point of contact with the tooth .

Front 8

Again ... componets of revmoable appliances

Back 8

1) Active component
2) Retentive component
3) Anchorage component
4) Connecting bast plate

Front 9

2) Anchorage

Back 9

anchorage components :
1) prevnetion of UNWANTED tooth movment
2) can be any of :
A) retentive componets
B) baseplate

Front 10

3) Retintive components

Back 10

1) clasps
2) labial bow

retitnve componetns have to be distributed to provide :
((((((anterior and postieror retnetion ))))))

Front 11

4) Baseplate

Back 11

- connects the componets of the reomvable applaince togather

Front 12

Removable applaicance Vs. fixed applaicnes

Back 12

1) removable applicance can only acheive tipping movments
2) fixed applaince can ahcieve all types of tooth movments

advantages of remoable applaicne :
1) easy to clean
2) better OH maniantce
3) more asethtics
4)chepaer
5) easy to adjust

disadvantages of removable applaicne :
1) only simple tooth movmemtn can be acheived ( tipping )
2) relies on patant coopreation to wear the applaice
3) less retentive in the lower arch ==> fixed here better

Front 13

types of tooth movments

Back 13

1) tiiping
2) rotaion
3) intursion
4)extursion
5)bodily movments
6)toruqe