5 Fixed Appliances

8/12/2019 5 Fixed Appliances

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This script includes all the information that was mentioned in the slides, the pictures are from othersources than the slide as no soft copy is available.

Fixed Appliances

Today we will talk about fixed appliances, last time we talked about removable appliances, now

before starting discussion, let's know the benefits and risks of these appliances.

Fixed appliances benefits and risks

So, what do you think the benefits for orthodontics treatment for the patient?

- Improving esthetics and appearance of patient: it is a psychological effect. According tostudies, 60% of children teased about their teeth were upset by this. So, improving the teethappearance will improve their psychological, self esteem and self confidence.

- Second benefit is dental health: now, in theory; well-aligned teeth are easier to clean (it'seasier to brush teeth when they're well aligned).

So, malalignment of teeth will make it difficult to brush, and more susceptibility to dental cariesand periodontal problems. But, is it true in reality according to studies? NO! Because teeth

brushing and oral hygiene depends on patients attitude towards oralhygiene, many patients are with wellaligned teeth but with very poor oral hygiene, and many patients with malaligned teeth but withgood oral hygiene.

So, in theory, well aligned teeth will be easier to clean, but very little evidence showed that well

aligned teeth will suffer less pathology.

Now what are the riskson the other hand?

- Decalcification/demineralizationwhich is the earliest stage of dental caries, and then theymay develop caries.

- As a result of excess tooth movement or heavy forces to the tooth from appliances, they mayget root resorption.

-

If you move teeth outside of neutral zone, you may get periodontal problem by gingivalrecession.

- Also, any orthodontic movement is susceptible to relapse. If the patient doesnt wear retainers. That iswhy we ask our patient to wear retainers to prevent relapse.

- Also it may interfere with medical problems, if the patient has very serious medicalproblem unless it is under control and the patient is aware of it.


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This is decalcification (whiting or white spot lesions) after wearing orthodontic appliances; in severecases it may develop cavitations which is caries. It is around the bracket.

Definition of fixed appliance

It is appliance that fixed to the teeth and cannot be removed by the patient .

So, compared to removable appliance, the patient can take appliances out, and put it back again,

while fixed app liances is bonded to the teeth and cannot be removed by the patient.

Mode of action

Now, what is the mode of action? In case of removable appliances, when you give single forces

through the active component, you will get tipping movement.

But in case of fixed appliances, you give mechanical forces couple to crown which can achievebodily movement, (Couple it means 2 points not single point), so it's not single contact (whichresults in tipping).

In conjunction with single force it can achieve rotation, apical and bodily movement.

Reasons of fixed appliance

Why do we use fixed appliance?

- Precision: If you need accurate tooth positioning, you need fixed appliance, removableappliance can't achieve perfect alignment, if you need perfection then you need to use fixappliance.

- Correction of rotation: If there is very severe rotation, like 90 degrees rotation, you needfixed appliances.

- Multiple tooth movement:. So, if patient have multiple tooth problem, you need multipletooth movement.

- Full range of tooth movements : you need to move the tooth body.


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- Inability to remove the appliance: if the patient is incomplainant and every time you givehim a removable appliance, thepatient doesnt wear it, you can use fixed so the patient can't remove it.

- Essential in lower arch: because it inconvenient to use removable appliances in the lowerarch because of the tongue, it will cause discomfort and it won't be as retentive as in the

upper arch.

Indications of fixed appliances

- Tooth movement that is not possible with removable appliances; which only can maketipping of teeth, so if you need other movement (rotate, torque, bodily movement) you needfixed appliances.

- If you need to close a space, you need to move the crown as well as the root , when youuse removable appliance, you make tipping of teeth which means you move the crown to oneside but the root is moving to the other side, if you want to move them parallel, you need

fixed appliance.

- Multiple tooth movement is required.- Overbite reduction by intrusion of incisors : remember when we talked about anterior bite

plane? So removable appliance can achieve overbite reduction however mainly by

overeruption of posterior teeth. But, if you want to reduce overbite by intrusion of incisors,because the patient has gummy smile for example, you'll need fixed appliance.

Instructions to the patient

- Maintain high level of oral hygiene otherwise the patient will get decalcification, cariesand depressed dental health such as gingival recess ion.

- Avoid hard or sticky foodbecause hard food will result in breakage of fixed appliance.- Avoid consumption of sugar containing food between mealsto prevent caries.- Cooperate fully with wearing headgear or elastic traction if required: if you asked the

patient to wear head gear for anchorage control and stabilization he must cooperate,

otherwise he'll need to do extraction.

- Attend regularly to have the appliance adjusted.Components of fixed appliances

- Bands: which is cemented on molar teeth and made of stainless steel.


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- Brackets: which is bonded on labial and buccal surface of teeth, but nowadays there islingual brackets. Bracket material could be stainless steel, plastic or ceramic.

base

tie-wings

slot

(Ceramic and plastic are esthetic brackets because they are tooth colored).

- Archwire: to move teeth, in orthodontics there are many types, but mainly we use nickeltitanium and stainless stee l, in the past we used to use gold archwires.

- Auxiliaries: anything that you use to hold archwire, apply force, open spaces or whatever.The material is ligatures or elastics.

The Archwire moves the teeth and the brackets tell (guide) the archwire where the teeth must move.So the arch wire will be in brackets' slot, when the Archwire is deflected it will try to go back to itsoriginal position (because it's elastic), so it will move the teeth with it until the wire is fixed in the

bracket slots then the archwire will stop moving the teeth.

Brackets:

It is rectangular in shape, thats why it is a couple force applications, it has three components:

- Horizontal slot (bracket slot): where the archwire fits.- Tie-wings: gingival and occlusal, to which ligature ties are attached to hold the Archwire in

place.

- Bracket base: bonded on the labial surface. It should be rough/mesh type for mechanicalretention with the composite resin; you bond these bases to enamel.

Brackets material can be stainless steel, plastic, ceramic or titanium, gold, Co-Cr but usually it's

made of stainless steel.


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Plastic bracket tend to stain and distort during treatment. That's why nowadays we don't use plasticbracket.

Ceramic bracket usually don't stain but have other disadvantages:

- Brittle and easily fracture especially the tie wings.- Extremely hardand can cause wear of opposing enamel: If you bond the lower teeth with

ceramic brackets and they bite on the palatal surfaces of upper incisors they don't break,

they'll cause wear of the opposing enamel (abrasion).

- Increased risk of enamel damage at debonding (taking off the braces) because of highbond strength between ceramic and enamel (it's higher than bonding between metal andenamel).

- Increased friction: when the tooth moves there will be frict ion between the archwire and theslot of the bracket, so if there is high friction tooth movement will be slow, the friction with

ceramic is higher than with stainless steel, to overcome this problem they made the bracketfrom ceramic but the slot from metal (e.g. Clarity), still this technique has a disadvantage

because the junction between the metal and the ceramic is weak, so it can be easily broken.

- More expensive than metal brackets.Sometimes, there is patient with smile zone only shows upper anterior teeth, and they requestesthetics brackets, despite the disadvantages of ceramic, you may use them only for the upper

anterior teeth and the rest you'll use metal brackets as a combination of both, or we can use ceramic

brackets for all teeth, except if we have deep bite, then we can't use ceramic brackets on the lowerincisors because the touch the palatal surface of the upper incisors and this will cause tooth wear.

Types of brackets by location:

Buccal fixed palatal fixed

- Buccal fixed appliances: most common, advantages of buccal type are: Good access for the orthodontist to work and good access for the patient to clean. Ease of work and reduced working time.


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Excellent finishing and detailing because we can see the buccal and the labial surfacedirectly but for palatal and lingual surface it's difficult to see d irectly.

The disadvantages are poor esthetics, because it's on the labial side, and if there is caries or

decalcification it will be visible .

- Lingual fixed appliances: advantages of lingual types are good esthetics and ifdecalcifications develop it will not be visible. Other benefit is good bite opening, when

you put bracket on palatal surface, the lower incisors will occlude on the brackets, so it willact as anterior bite plane. So, it's good for bite opening.

Disadvantages are poor access, difficulty in working, reduced interbracket span (it's adisadvantage because the length of the wire will be reduced so there will be less flexibility),

increased working time, patient discomfort (the tongue may be traumatized so there will bepain and ulcerations) and poor finishing and detailing.

Types of brackets by fixed appliance techniques:

1- Standard edgewise : developed by Edward angle in 1928.

Slot orientation is horizontal. Slot dimension is 0.022x0.028to allow control of tooth position in 3 plane spaces. Same bracket or band is applied to every tooth that is why it's called "standard"

edgewise. They used to use bands on every tooth in the past, but when we started to use

bracket without bands? When composite developed.

Precise control of tooth position and angulations is achieved by placing bends into Archwire .

Advantages: the first appliance to allow precise control of tooth position to be achieved

relatively simply.

Edward angle is the father of orthodontics; he is the first person to be professionally work withorthodontic movement; however Arab talked about orthodontic tooth movement long time beforehim.


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of theses brackets is that the treatment time is reduced as the friction is eliminated or reduced. Thefriction like we talked about, when we bend the Archwire, the friction of Archwire to the slot is

increased. So if this is a door, the friction will be decreased.

There are many types of self-ligating like Damon, speedand 3m smart clip and others.

TheDamonbracket is self ligating, meaning it has a built in sliding door that secures the bracket

to the wire, this allows the wire to slide through the braces freely (no friction).

Archwires

Now we will go to another component of fixed appliances which is the archwire. They are many typeof archwire, but what we use in orthodontics mainly titanium and stainless steel, in the past they usedto use gold and cobalt-chromium. There are two types of archwire:

1. Active:Archwire is deflectedon tying in to the bracket so that the forces move the teeth.2. Passive:Archwire is not deflected; the forces are applied by elastics or auxiliary spring.

In above case, when the archwire is bended there is deflection, do you think this archwire will applyforces? YES! But when it's straight wire do you think it is active? NO! It is passive archwire to

maintain the arch form from getting forces from other directions or something else other thanarchwire.

So when it applies force, it is active, but when it doesnt apply forces, it is passive.

Elastic behavior of archwires

Now to understand how archwire apply force to teeth, you need to understand something called

"elastic behavior" of the Archwire.

Elasticity: the ability of the material to recover following the removal of an applied force .Elastic behavior is defined in terms of stress-strain response of any material.

Stress: force per unit of area. So you apply the force on the object from outside, inside the object itwill receive stress (because there will be force which is equal in amount and opposite in direction

inside the material).

Strain: deflection per unit of length. It's internal distortion produced by applied load.

Conclusion: stress and strain are from internal; force and deflection are from external.

Force deflection curve

So, in force deflection curve or stress-strain cure, there are 3 major properties of Archwire materialthat are critical in defining their clinical usefulness: strength, springiness (elasticity, the inverse of

stiffness) and range (how much can I bend it).

Strength = stiffness x range


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How stiff the wire is, and what is the range the wire can withstand by deflection before it distorts,

these are governed by the proportional limit, yield strength and ultimate tensile strength

So this graph represents stress (force) proportional to strain (deflection) :

- Proportional limit: the point at which the wire starts to deform, the wire will reactelastically until proportional limit is reached, where the wire will bend and elasticity doesn'tapply.

- Yield strength: the point at which 0.1% deformation is measured.- Ultimate tensile strength: maximum load that archwire can sustain before failure

(fracture).

- Stiffness= 1/springiness. It's the opposite of springiness; springy wire means that itsflexibility or elasticity is high, stiff wire means more solid wire. Each value is proportionalto the slope of the elastic portion of the force defection curve. The more horizontal the slopethe springier the wire. The more vertical the slope the stiffer the wire.

- Modulus of elasticity (slope). Slope represents the stiffness.- Wire with increasing stiffness: NiTi


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It's the amount of permanent deformation that the wire can withstand before breaking, I.e.deformation without breakage, so if you bend a formable wire it will not go back to it's

original position.

Properties of an ideal archwire

High strength, good spring back, large range of action, high resilience, low stiffness, formable,

joinable which means we can solder/weld it, low friction (so the sliding is better),biocompatible, low cost, superelasticity, shape memory and aesthetic. You have to understand

just the properties that were explained.

What is the most biocompatible material? It is Titanium molybdenum alloy (TMA)

Types of archwire materialGold alloy, stainless steel, cobalt chromium, nickel titanium, titanium molybdenum alloy

(TMA), composite plastics.

Esthetics ArchwireThere are esthetic archwire; however we dont like to use them for many reasons

These will be either:

Coated metal wires: coated stainless steel or Niti. The coating can be a white epoxyresin or Teflon coating. This means the wire itself is metal but it is coated by whitematerial for better esthetics. The disadvantage of metal coated archwire is that with time,it will be worn out and only metal is left without white epoxy res in and Teflon coating.

Non-metallic materials:without metal, full composite plastics.Auxiliaries

It is components other than archwire and bands/bracket.

- Elastomeric modules: round modules to hold the archwire in the bracket slot (it comesin different colors).

- Ligature wire: it has the same function as elastomeric modules . Sometimes we preferthese because the elastomeric is elastic and will not make a 100% accurate movement


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(torque, bodily movement, angulation or anything else) to the teeth, its gauge (the ligaturewire) is (0.09 to 0.1).

- Coil spring: it is either open or closed. It's open if we want to open the space, and closedif we want to close the space, it's either stainless steel or nickel titanium.

- Hooks: either crimpable (it's stretched and attached to the wire), or sliding (movesalong the wire).

- Elastomeric chain (power chain): to close the spaces. It can be spaced or non-spaced (inspaced there is increased distance between the circles, which can be short or long) it is

related to the amount of forces that we need.


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Non spaced

Short spaced

Long spaced

- Intermaxillary elastics: Many of our patient wearing intermaxillary elastics betweenupper and lower teeth to correct the relationship between them. And it's called class II

and class III depending on direction of tooth movement that you want. If you have classII canine and molar, and want to change into class I, you have to use class II elastics,

from upper canine to lower molar, this elastic (class II) will move the upper anteriorbackward and lower posterior forward. Next, Class III elastic is from lower canine to

upper molar this elastic (class III) will move the upper posterior forward and loweranterior backward.

Class II Class III

It comes in different size; the force is dependent on the size that we chose, you have to

measure the force with force gauge, to make sure, because sometimes when you get it fromthe company it's written that it gives 4.9 oz (which is around 140 g) but when you measure it,it may not be 140, so ideally you have to make sure before using it.


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6. Finishing: If there is any minor details to be adjusted; you need to finish it, like the caninerelationship and the molar relationship, after this you debonded the appliance.

7. Retention:after debonding, if there is no retention there will be relapse.Features of fixed appliance

More complex: require specialist More time-consuming. Demand excellent oral hygiene. Require well motivated patient. More expensive. Less effect on speech than removable (because there is no acryl).

Disadvantages of fixed appliance

- Requires more time.- Repairs are more time-consuming.- Non esthetics, sometimes it's esthetic, like ceramic or if it's from the lingual side .- When damaged can cause discomfort.- Need excellent oral hygiene.

THE END

This script is dedicated to my partner M.Husam Droubi, Prince of moisture control.

Done by: Ammar Aldawoodyeh

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5 Fixed Appliances