intro to ortho labs

Question 1

IOTN - index of ortho treatment need

Answer 1

The I.O.T.N. attempts to rank malocclusion in terms of the significance of various occlusal traits for an individual’s health and perceived aesthetic impairment.

The identifies those individuals who would most benefit from Orthodontic treatment. The Index incorporates two components:

Aesthetic Component (AC)
Dental Health Component (DHC)

Question 2

dental health component

Answer 2

The DHC records the various occlusal traits of a malocclusion that would increase the morbidity of the dentition and the surrounding structures

Question 3

stainless steel

Answer 3

mostly used for metallic part of ortho appliance

Question 4

how is stainless wire is made

Answer 4

made by drawing the metal in a cold state through a series of dies of successively smaller diameter.

this causes work hardening which gives the wire its spring properties.

stainless steel will be further work-hardened during the bending process of constructing component parts for Orthodontic appliances.

Question 5

bauschinger effect

Answer 5

when a coil is bent in a wire, it is differentially stretched so that the outer surface becomes more work hardened and thus has better spring properties that the inner surface.

if the coil is activated in the same direction as the previous bending, its elastic recovery is greater than if it is deflected in the opposite direction.

Question 6

fractures of stainless steel wire can occur when

Answer 6

1. Overworked: The wire has been excessively overworked by bending and then straightening the wire at the same point creating extreme stresses within the immediate area which can result in fracture.
2. Mechanical abrasion crushed or marked: This can occur if the wire has been damaged by burs or stones in the finishing process of removable appliances or if the wire has been marked or crushed during the fabrication of components.
3. Fatigue: This can be caused by a repeated straining action. E.g., continually strained to engage a deep undercut with an Adams clasp.
4. Weld Decay: Is an intergranular corrosion created by overheating the alloy this causes the Chromium carbides to precipitate at the grain boundaries, the oral fluids can now access the surface of the other metals resulting in a galvanic action which weakens the area sufficiently to result in fracture.

Question 7

what type of ss is used in ortho

Answer 7

18/8 austenitic stainless steel alloy

(austenitic is the crystalline space lattice structure of the alloy. The alloy cannot be heat hardened and remains in a soft condition unless it has been cold worked, this material is corrosion resistant when cold worked)

Question 8

constituents of ss wire

Answer 8

72% - Iron
18% - Chromium
8% - Nickel
1.7% - Titanium
0.3% - Carbon

Question 9

iron with carbon

Answer 9

forms steel

Question 10

chromium forms

Answer 10

passive oxide film over the surface of the metal that enables the stainless steel to be corrosion resistant.

Question 11

nickel

Answer 11

assists yo achieve austenitic structure at room temp with chromium

and improves corrosion resistance

Question 12

titanium

Answer 12

prevent the precipitation of chromium carbides at the grain boundaries when the alloy is heated during welding or soldering