dental wire Flashcards
(16 cards)
list 5 requirements of dental wire
1.tensile strength
2.elastic limit
3.ductility [ability to deform under tensile stress BEFORE fracturing, allowing it to be stretched or bent without breaking]
4.hardness
5.corrosion resistance
list the dental wires in order of strength
- chrome
- stainless steel
- titanium
- gold
- chrome and stainless steel = very similar mechanical properties [TS,elastic limit, ductility]
- chrome is +4 more MPa in TS
list the composition and properties of strengthening wire
composition
- zinc, iron and carbon
properties
NA natural ware
low [everything]
-cost, strength, stiffness, formability, weldability, resilience, elasticity, biocompatibility, corrosion resistance
list the composition and properties of stainless steel wire
Composition
- Fe 67%
- Cr 19%
- Ni 10%
- Mo 4%
Properties
low
- stiffness
medium
- cost, natural ware, strength
high
- formability, weldability, resilience, elasticity, biocompatibility, corrosion resistance
list the composition and properties of chrome wire
composition
- Co 65.5%
- Cr 29%
- Mo 5.5%
properties
medium
- cost, stiffness, formability, resilience, elasticity
high
- natural ware, strength, weldability, biocompatibility, corrosion resistance
list the composition and properties of titanium wire
composition
- Ni 54%
- Ti 44%
- Co 2%
properties
- totally biocompatible
low
- formability, resilience, elasticity
medium
- cost
high
- natural ware, strength, stiffness, weldability, corrosion resistance
list the composition and properties of gold wire
composition
- Au 63%
- Pt 7%
- Pd 5%
- Ag 10.5%
- Cu 12%
- Zn 0.5%
- Ni 2%
properties
- nil natural ware
low
- strength, stiffness
med
- formability, resilience, elasticity
high
- cost, weldability, biocompatibility, corrosion resistance
list the application of strengthening wire
wire strengthening
list the application of stainless steel wire
wire strengthener
clasp construction
ortho wire
welding/soldering
list the application of chrome wire
clasp construction
ortho wire
welding/soldering
list the applications of titanium wire
clasp construction
ortho wire
welding/soldering
list the applications of gold wire
clasp construction
welding/soldering
describe work hardening in dental wires, how and why its done
- process of making a metal harder/stronger through plastic deformation [bending it at the same place repeatedly makes it harder until it breaks]
- when metal = plastically deformed = dislocations move and additional ones are generated
- more dislocations = they will interact = becoming pinned/tangled
- results in a decrease of mobility and strengthening of the materials
- work hardening ^ TS, YS and hardness at expense of reduced ductility
describe annealing in dental wires, how and why its done
- heat tx which alters the physical/chemical properties of material
- annealing furance heats material above the recrystallisation temp and then cools it
why
- induces ductility + softens materials = more malleable + easier to work w
- routinely done in ortho wire bending to reduce wire stress
- reduces effects of work hardening [occurs during bending]
- heating/cooling reduces brittleness = prevents fracturing
- also removes stresses that occur when welds solidify
- main drawback = time consimung procedure adding to cost breakdown
provide a brief overview of the relationship between work hardning, annealing and heat treatment
- annealing hardens the wires via plastic deformation and dislocations to ^ TS,YS and hardness at the expense of ductility
- annealing heats/cools the wire, inducing ductility, making it more malleable/workable + relieves stress/brittleness from bending
- heat tx heats/cools wire to greatly ^ hardness + mechanical strength
describe heat tx in dental wires, how and why its done
- ability to reverse annealing effects
- alloy is heated then quenched/cooled
certain alloys can be modified = greatly ^ hardness and mechanical strength
eg gold heat treated = eases polishing, reduces wear and damage on finished surface, increase strength and increase corrosion resistance
