Below is listed the main criteria for the selection of an orthodontic wire (Desirable characteristics)
(O’Brien W.J., Dental Materials and their selection, Pg 284)
- A large springback
- Low stiffness
- Good formability
- High stored energy
- Corrosion resistance
- Biocompatibility and environmental stability
- Low surface friction
- Capability to be welded or soldered to auxillaries
- Cost
Discuss each of these characteristics and why you think they are listed as desirable criteria for orthodontic wire.
A large springback:
ReplyDeleteGives the wire a wider range of use. As the wire has a higher maximum strain it allows bending the wire a number of times before it cannot return to original position.
Low stiffness:
Important because we use relatively small lengths of wires in fabricating orthodontic appliances, thus the wire needs to have a low stiffness to enable the bending of the wires in their various angles. The stiffer the wire the longer it would have to be.
Good formability:
We need different shapes, diameters, angles, etc. for the different components and forming needs to be done at room temperature thus good formability is essential.
High stored energy:
The higher the stored energy the more movement of the tooth is possible.
Corrosion resistance:
Critical, as wires are typically bent thus could expose the tissues of the mouth to corrosion which can cause a danger to the patient's health.
Biocompatibility and environmental stability:
Also vital as the appliance regularly is in contact with the tissues of the mouth and must therefore not influence or be influenced by the tissues. they must also remain chemically stable as they are often in the oral cavity for extended periods of time.
Low surface friction:
Limit scratches from occurring on the wire, not sure??????
Capability to be welded or soldered to
auxillaries:
Important as certain appliances require the bent wires to be either soldered or welded in place. This gives the wires numerous applications.
Cost:
Probably in some cases most important as this directly influences the use of the wires, if too expensive - will probably not be considered. And most of the time the laboratory has to have numerous stock of wires and it being expensive could influence the profitability of such appliances.
With regards to the cost and its influence on whether you will use it or not would probably be in relation to;
DeleteIf the patient needs to wear the appliance for a long time the more expensive wire would be the best option, also it would depend on the treatment/appliance to be made which would determine your choice of wire. It is not always if the patient can afford the wire or not.
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ReplyDeleteI would have to agree with most of what mr samuels has commented although from my research of Low surface Friction i found that:
ReplyDeleteThe development of materials with low surface friction for straight wire mechanics are highly desirable because they can reduce the strain on anchorage. Friction between the bracket and arch wire can cause loss of force, as a result the desired tooth movement is slowed down or even inhibited. It is therefore desirable that orthodontic wires and brackets show the lowest possible friction coefficients.
Not one type of wire may consist of all the above criteria therefore optimal use of orthodontic wires can be made by carefully selecting the appropriate wire type and size to meet the demands of a particular clinical situation.
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ReplyDelete
ReplyDeleteFormability
It refers to the ability of wires to be bent into desirable shapes without fracturing or deforming permanently
Shape memory
This phenomenon is characterized by a steady accumulation of force in the wire to the point of deformation. Similarly, when the wire is deactivated and returns to its original configuration the forces
remain constant over a long period of time, which
is clinically required to ensure physiological tooth
movement also revers to the resilience of a wire
Wire characteristics of clinical relevance
ReplyDeleteSeveral characteristics of orthodontic wires are considered desirable for optimum performance during treatment. These include a large springback, low stiffness, high formability, high stored energy, biocompatibility and environmental stability, low surface friction, and the capability to be welded or soldered to auxiliaries and attachments. A brief description of each of these desirable wire characteristics is provided.
1. Springback. This is also referred to as maximum elastic deflection, maximum flexibility, range of activation, range of deflection, or working range. Springback is related to the ratio of yield strength to the modulus of elasticity of the material (YS/E). Higher springback values provide the ability to apply large activations with a resultant increase in working time of the appliance. This, in turn, implies that fewer arch wire changes or adjustments will be required. Springback is also a measure of how far a wire can be deflected without causing permanent deformation or exceeding the limits of the material.
2. Stiffness or load deflection rate. This is the force magnitude delivered by an appliance and is proportional to the modulus of elasticity. Low stiffness or load deflection rates provide:
(1) the ability to apply lower forces,
(2) a more constant force over time as the appliance experiences deactivation, and
(3) greater ease and accuracy in applying a given force.
3. Formability. High formability provides the ability to bend a wire into desired configurations such as loops, coils, and stops without fracturing the wire.
4. Modulus of resilience or stored energy (MR) This property represents the work available to move teeth. It is reflected by the area under the line describing elastic deformation of the wire
5. Biocompatibility and environmental stability. Biocompatibility includes resistance to corrosion and tissue tolerance to elements in the wire. Environmental stability ensures the maintenance of desirable properties of the wire for extended periods of time after manufacture. This, in turn, ensures a predictable behavior of the wire when in use.
6. Joinability. The ability to attach auxiliaries to orthodontic wires by welding or soldering provides an additional advantage when incorporating modifications to the appliance.
7. Friction. Space closure and canine retraction in continuous arch wire techniques involve a relative motion of bracket over wire. Excessive amounts of bracket/wire friction may result in loss of anchorage or binding accompanied by little or no tooth movement. The preferred wire material for moving a tooth relative to the wire would be one that produces the least amount of friction at the bracket/wire interface
1) Large springback- According to O' Brien, springback is the elastic strain recoverd on unloading from the permannent deformation range. This is a desired property as it allows one to bend the wire a number of times before deformation.
ReplyDelete2) Low stiffness or the rate of force delivery is the slope of the elastic of unelastic curves. This is dependent on the two fundamental factors namely: the coomposition and the structure of wire; and the wire segment geometry (cross section shape and size and the segment length). This property is desirable as the wire then requires less bending effort.
3) Formability allows one to shape the wire hence it is a desirable property.
4) High stored energy refers to the appliance's ability to move the teeth over a period of time.
5) Corrosion resistance is an important factor as it prevents the appliance from deteriorating during use and to also avoid the formation of mercury.
6) biocompatibiltiy and enviromental stability - these are important factors as the appliance should have affinity towards the patients tissue and the environment. The patient is to wear the appliance for a period of time hence it should be"friendly".
7) low surface fusion - this property prevent wear when in contact with teeth.
8) Capability to be soldered- This allows the wire to have optimal strength by creating a joint.
1. A large springback:
ReplyDeleteOrthodontic wires need a large springback to increase the range over which it can apply a force. The large springback also allows one to very the amount of force to be applied to a tooth.
2. Low stiffness:
Orthodontic wire should not be stiff as this will make it difficult to work with and the amount of force which it can apply to a tooth will be too much regarding the cross section of the wire.
3. Good formability:
The wire needs to be manipulated with ease to allow easy adjustment to take place and event to obtain the desired form or shape or structure.
4. High stored energy:
The wire needs to be able to store energy as this will be used to move a tooth over a certain range.
5. Corrosion resistance:
This is required as the wire is placed in the oral cavity where it is exposed to different pH levels and moisture. If corrosion should occur, this will influence the biocompatability of the material.
6. Biocompatibility and environmental stability:
It needs to be biocompatable to resist allergic reactions in the mouth.
7. Low surface friction:
There should be low surface friction as the wires need to move along each other at some times. Low surface friction will also reduce the plaque build up.
8. Capability to be welded or soldered to auxillaries:
The wire needs to be able to be welded as some complex cases require welding of certain components.
9.Cost:
The wires should be affordable as to cut down on the cost of the final product and make it affordable to the consumer.
1. A large springback
ReplyDeleteHigher springback value provide the ability to apply large activations with resultant increase in number of arcwire change. It is also a measure of how far a wire can be deflected without causing permanent defamation.
2. Low stiffness
Low stiffness leads to the modulus to apply lower forces, a more constant force to be delivered over time and great ease and accuracy in applying a given force.
Good formability
High formability provides the ability to bend a wire into desired configuration such as loops, coils etc. without fracturing the wire
3. High stored energy
This property signifies the energy stored capacity of the wire.
4. Corrosion resistance
It is important that orthodontic wire is resist to deterioration caused by the oral environment. Most corrosion of dental alloys is insidious and invisible to the naked eye, however when it occurs some of the elements are released and cause biologic effects such as toxicity, allergy or mutagenicity. most of the orthodontic wires provides this quantity
5. Biocompatibility and environmental stability
Biocompatibility includes resistance to corrosion tissue tolerance to element of the wire. Environment stability ensures the maintenance of desire properties of the wire for an extended period of after manufacture. These are properties are essential to ensure predictable behavior of the wire when in use.
6. Low surface friction
When selecting a wire, the wire should produce least amount of friction at the bracket/ interface wire. Excessive friction can result in loss of anchorage or binding accompanied by little or no tooth movement.
7. Capability to be welded or soldered to auxillaries
This increase the utility of the wire since more auxiliaries can be fixed onto it.