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Student number: 1059937

Assignment 1:

COMPARE AND CONTRAST THE USE OF THE FOLLOWING IN ORTHODONTICS:REMOVABLE APPLIANCES, FUNCTIONAL APPLIANCES, FIXED APPLIANCES

October 2010

Word Count: 3859

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Contents:

Introduction 3

Hardware requirements and construction 4

Ease of use and placement 7

Patient use & compliance 11

Actions of the appliance 13

Conclusions 19

References 21

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Introduction

Following the detection and diagnosis of an orthodontic malocclusion, treatment is planned and

then effected with the use of appliances.

Certain orthodontic problems require the use of one or several types of appliance. This

paper identifies that most of these appliances fall into three loose categories: removable,

functional and fixed (illustration 1).

The author intends to highlight their roles within traditional and contemporary

orthodontics whilst also stating their perceived advantages, disadvantages and limitations, as

well as the potential risks of use.

Illustration1

ORTHODONTIC APPLIANCES

REMOVABLE FUNCTIONAL FIXED

Upper removable fixed labial

Retainers >>Herbst >>Pre adjusted (Straight Wire Appl.)Clear aligners >> Self-ligating

removable lingual>>Twin block >>S.W.A. & self-ligating>>Herbst >>Bonded retainers>>Activator>>Frankel

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Har dware requirements construction

The component parts of orthodontic appliances can vary greatly. This variation means that each

appliance will tend to have a specific set of indications, but also limitations with functions it

cannot perform.

The earliest forms of traditional orthodontic appliances are the removable ones (Littlewood,

2001), namely the URA or upper removable appliance. The simplest way to approach its

construction is by use of the acronym ARAB (Mitchell, 2007), which stands for: Active

components; Retentive components; Anchorage; Base plate. Table 1 (below) lists the types of

components commonly seen in a URA.

Alternative removable appliances include orthodontic retainers and clear aligners both of which

serve very different purposes and will be discussed later in this article.

Table 1

COMPONENT PURPOSE TYPES

Active supply forces to effect tooth movement bows

elastics

screws

springs

Retentive secure the appliance to the dentition bows

clasps

cribs

Anchorage resistance of unwanted tooth movement -

Base plate Binds the other components together and acrylics

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reinforces anchorage

Functional appliances work to modify mandibular growth by harnessing

(utilising/removing/modifying) the forces of the erupting teeth, dento-facial growth and oro-facial

musculature (Millett, 2003). They typically have no active components.

Their construction is slightly more complex compared to URAs (Rock, 1990) and fixed-

appliances due to the nature of its requirements as an appliance. There are several types of

functional appliance and some common examples of these are outlined in table 2 below. Their

component parts and construction are similar to that of upper removable appliances.

Table 2 (modified from Mitchell, 2007)

TYPE EXAMPLES OF COMPONENTS DESCRIPTION

ACTIVATOR

e.g. Bionator No clasps least bulky of the activator appliances

Passive labial bow full time wear except meal times

palatal loop Allows arch expansion

FRANKEL Acrylic pads manages abnormal soft tissue patterns

lower incisor capping expands arches, widens the alveolar processes

buccal shields 4 sub types; FR type I for class II/I cases expensive to fabricate and repair (easily damaged)

HERBST Cemented splints fixed due to cementation, thus full time wear

Telescopic pin and tubes variable posturing of the mandible can be controlled

TWINBLOCK buccal blocks removable appliance

head gear attached via tubes 14-16hours per day for headgear use

Clasps

MagnetsPassive labial bow

Functional appliances are constructed in the laboratory but designed chair side with the patient.

A working bite registration is taken with the patient posturing the mandible forward whilst the

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teeth are out of occlusion (Clark, 2010). These records are sent to the laboratory for fabrication

of the appliance.

Fixed appliances are comprised of a series of selected component parts which are assembled

intra-orally. These are typically mass produced in factories (unlike URA and functional

appliances which are laboratory-made).

Common component parts include (modified from Millett, 2003):

Brackets and bands which are bonded to the teeth and made in a variety of materials

and sizes; these hold the active components in place.

Archwires the key active component of fixed orthodontics; will be either round or

rectangular, and are typically made from stainless steel, nickel titanium, cobalt chrome

(Elgiloy), or Beta-titanium alloys.

Accessories cement lutes for bonding brackets and bands; elastics for inter/intra-

maxillary traction; modules to keep the arch wires inside the bracket slot; springs e.g.

coil springs for space opening/closure; elastomeric chains for traction and derotation.

Comparatively, URA construction is relatively simple in that they are designed by prescription

and manufactured in the laboratory from impressions and a bite registration. This saves the

clinician a considerable amount of chair side time and cost (Mitchell, 2007) compared to

functional appliances which require a more complex treatment planning and prescription, and

greater time allocated to the registration phase and adjustment and fitting stages(Clark, 2010).

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By contrast fixed appliance components come ready made, however necessitate far more

extensive treatment planning and effort during their placement and adjustment (Roberts-Harry,

2004).

It would be wise to also include a brief mention of allergies to dental materials at this

stage. Prior to appliance selection, it is invaluable to know if the patient has any allergies to any

materials used in the construction and components of orthodontic appliances. Common

hypersensitivity reactions can occur with certain acrylic resins (typically the auto polymerizing

types) used to construct the base plate of some removable appliances (Jacobsen, 1989); or to

the nickel an cobalt content in certain types of orthodontic components such as wires and

brackets (Janson, 1998). Alternative material choice can be used to overcome such simple

obstacles to the provision of care.

Ease of use and placement

Removable appliances are relatively simple to use, requiring very simple adjustments prior to

fitting. A URA would be adjusted to ensure a suitable fit and that the patient can remove and

insert it away from the surgery. The retentive components need to be checked or problems such

as anchorage loss and prolonged treatment times may occur. The active components would

then be activated where appropriate, and lastly, detailed post operative instruction (including

appliance hygiene and care) would be given to the patient along with future appointment times

where treatment progress can be monitored and adjustments made.

Clear aligners are simpler to use once the necessary pre-treatment has been performed.

This usually involves interproximal reduction (IPR) to provide sufficient space that will facilitate

tooth movement once the aligners are in situ (Bishop, 2002).

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Lastly is the retainer which must be checked and adjusted carefully before supplying the

patient with post-op instructions detailing the amount of wear time which may very depending on

the nature of the orthodontic treatment provided (McNally, 2003).

Functional appliances are fitted in a similar sequence as most types are a form of removable

appliance. The key difference is in the time required at fit and adjustment appointments which

relate to the complexity of this type of appliance. The overjet when the patient has the appliance

fully seated needs to be measured and checked that it is an appropriate amount (Clark, 2010).

For example, in Twin Block therapy the initial opening between premolars should be 3-5mm

(Rock, 1990). If it is not then adjustments using a straight hand piece and acrylic bur may need

to be used. However if the opening is excessive then the appliance may need to be remade.

This could be due to an error during bite registration or during lab construction and ideally either

should be identified before a remake to avoid the same problem occurring again. As well as

detailed post op instructions for dietary advice and appliance care, the patient may also need to

be informed on when and how to use expansion screws if there is one. Once removable or

functional appliance therapy is complete, there is little or no clean up procedure, except in fixed

Herbst appliances which have been cemented to the arches (Mitchell, 2007).

Fixed appliance placement is far more complicated. The armamentarium required differs from

that used in removable and functional appliance therapy because the appliance is not a

constructed one. Pre treatment records are checked; appropriate brackets, bands and lutes are

chosen in advance and bonded individually or in groups depending on the operators experience

and / or training. Archwires are then applied to the slots in the brackets and held there using

auxiliaries such as elastic modules. This is an oversimplified description of the process of

placing fixed appliances. The essence of placement and use of this appliance type is typically

categorised into the three phases outlined in the table below:

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Table 3 (modified from Gill, 2008)

PHASE AIMS DESCRIPTION

1 LEVELLING & ALIGNMENT bracket placement

use of separators if banding required

Light forces with circular arch wires

2 WORKING ARCHWIRES progression to rectangular arch wires

maintain arch formbodily tooth movements

reduce overbite and overjet

manage space closure

3 FINISHING fine detailed movements

settling the occlusion to improve stability

Debonding the brackets

Retention

The correct placement of the brackets is pivotal to treatment success (Ireland, 2003). It is the

most technique sensitive aspect of fixed appliance therapy. The clinician must first determine

where to position the bracket. Typically this is done by identifying anatomical landmarks on the

facial surfaces of the teeth (see image below).

FACC - facial axis of the clinical crown

FAP - facial axis point

AP - archwire plane

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Image 1 (taken fromhttp://www.learn-ortho.com/tips-frame1.htm/ )

In traditional fixed appliance systems wire bending was necessary in order to generate the

forces required to effect desirable tooth movements (Rock, 1995). However more contemporary

methods have arisen more recently based around what is commonly called the Andrews

straight wire appliance (S.W.A.). To make life simpler, the brackets of a S.W.A. system have

built-in three-dimensional values (tip, torque, in-out), which saves the operator a tremendous

amount of chair-side time as little or no wire bending is required (Rock, 1995). Another segment

of this paper discusses in more detail the types tooth movements are possible with fixed

appliances.

With time saved with the reduced work-load associated with wire bending, more time can then

be spent on the next phase of placement: bonding. This is the way in which the brackets are

bound to the surfaces of the teeth (obviously varies with lingual orthodontic appliances, hence

the name). Glass ionomer or composite resin lutes are most commonly used (Banks, 2010).

Today the latter is most often used which means that great care with isolation and bonding

procedures is essential to maximise retention of the bracket to the tooth surface. Bonding failure

ultimately will have deleterious effects on the clinicians time and costs, (Brown 2009) but also

prolong the length of treatment for the patient due to delays.

Once bonding is complete, the placement of the archwire and auxiliaries is performed, and

postoperative instructions and appointment times can be given to the patient.

At the end of treatment the brackets must be debonded. Care must be taken at this

stage to make sure that the enamel is not harmed and also to check that no cement has been

left behind.

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After the completion of fixed appliance therapy, bonded lingual retainers may be

employed to resist unwanted tooth movements and orthodontic relapse. These too are typically

bonded with some form of passive wire (e.g. twist-flex) and a composite resin lute (Tabrizi,

2010). Normally they are applied directly by the clinician; however for ease of use some

orthodontic laboratories offer constructed jigs which hold the wire in place during bonding in

order to save the clinician time.

The author would summarise that removable appliances can be the simplest to place and use;

however the complexity of functional and fixed appliance placement and use is outweighed by

their many applications in orthodontics.

Patient use & compliance

The following table highlights the ease of appliance use from the patient perspective. These

factors can affect the levels of patient compliance, which in turn can have significant impact

upon the course of treatment.

Table 4 (modified from Mitchell, 2007)

removable appliance can be cleaned with ease and no obstruction to OH

relatively simple to insert

patient may be inclined not to wear appliance for certain reasons

functional common types are removable >> easy to clean; no obstruction to OH

relatively simple to insert

patient may be inclined not to wear removable typesfixed types will cause obstruction to easy OH

Attachment of head gear may prove cumbersome

Risk of harm from head gear/extra oral attachments

fixed appliance cannot be removed

obstruction to simple OH as not removable

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attachment of head gear and elastics may prove cumbersome

Risk of harm from head gear/extra oral attachments

If an appliance is not worn / cared for correctly or simply not worn regularly at all, then treatment

will either become prolonged or fail (Schott, 2010). For this reason it is crucial at the

assessment stage to ascertain whether the patient is suitable for a particular appliance.

In the case of removable and removable-functional appliances, the most common

compliance issue is that of getting the patient to wear the appliance for the maximum daily time

allocated. Tell-tale signs of a lack of appliance wear would become evident at follow up and

adjustment appointments. This disadvantage is also a great advantage as removable

appliances are far more easily cleaned compared to fixed ones and whilst out of the mouth the

effect of good oral hygiene can be maximised.

The effect on speech can also become a barrier to continued wear, however if the

patient is reassured that speech will acclimatise after a given period of time, compliance may

also improve.

Retainers must also be included here. Because they are removable, patients have the

ability to choose not to wear them as and when directed. The potential disaster here is

orthodontic relapse (McNally, 2003).

Functional appliances are relatively simple for the patient to use, however due to their typically

bulky nature can sometimes spend more time out of the mouth than in. This in some cases is a

design flaw where a patient cannot tolerate the obtrusiveness of the appliance. A key study by

OBrien in 2003 analysed the failure to complete treatment rates for fixed Herbst appliances

were far less than removable Twin block appliances.This related to the prolonged wear times,

aesthetics of the appliance and the amount the bite was opened by.

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When connected to extra-oral devices such as head gear, functional appliance use can

become more difficult for the patient. We have to take into account the age of the patient and

that he/she may not alone have the dexterity to make the connections safely. There have been

many papers highlighting the risk of trauma to the soft tissues, in particular the eyes (Travess,

2004), due to the detachment of head gear apparatus from the appliance during night time. To

protect against such iatrogenic risks, patients are routinely given safety goggles.

There have been studies on the levels of compliance with removable appliance types. Some

have even go as far to measure to change in compliance when microsensors are connected to

them, allowing the clinician to monitor wear time and patterns (Ackerman, 2009). This may even

go as far as to be a motivational aid for the patient.

With fixed appliances the key disadvantage is that there are issues with maintaining an

exemplary level or oral hygiene. Otherwise common iatrogenic risks such as enamel

decalcification and periodontal disease are likely to ensue post-treatment (Travess, 2004). This

disadvantage is also a major plus in that full-time wear is guaranteed, meaning that treatment

progresses smoothly without interruptions, saving a lot of time for both the clinician and the

patient.

Fixed bonded retainers guarantee compliance, however common problems include the

inability of the patient to floss. This can lead to the accumulation of calculus which will cause

periodontal problems. Other issues include the likelihood of composite resin leakage (Uysal,

2009), leading to caries which may go undetected for some time, or the passive wire debonding

from the teeth without the patients knowledge, again leading to a caries risk and the chance of

relapse. Regular check ups and the use of floss picks can be used to prevent these problems.

Actions of the Appliance

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The function of retainers is to hold the teeth in their finished state upon completion of

treatment with any of the three orthodontic appliance types. After teeth have been repositioned

a retainer (e.g. Hawley, Essix) may be used between 6-12 months or an indefinite period whilst

the periodontal ligament fibres reorganise and the teeth settle into a state of balance with the

soft tissues (Sheridan, 1993; McNally, 2003).

Functional appliances are used for growth modification, typically in class II cases. The key word

here is growth. If the patient is not growing, or about to enter a stage of growth (i.e. biologically

is an adult) the functional appliance use in contraindicated. In such cases orthodontic

camouflage should be considered (Ireland, 2003). Standing height charts are used by

orthodontists in the assessment and treatment planning stages to ascertain the appropriate

timing and use of functional appliances. Active growth phases for children when functional

appliances are indicated normally lies in the pubertal growth spurt phase. This is typically11 - 13

years of age for girls and 12 - 14 years of ages for boys (Mitchell, 2007).

The essence of functional appliance therapy is to encourage the mandible into a more

forward position whilst either holding back or retruding the maxilla (Gill, 2008). The maxillary

dentition can be retracted and the mandibular dentition proclined. There are a variety of

appliances available, each with distinct purposes. A summary can be seen in Table 5 below.

PASSIVE TOOTH BORNE ACTIVATOR Opens the bite; advances the mandible

BIONATOR forward posturing of mandible; blocks between the teeth to

control vertical dimensions

HERBST bonded splints between arches dictate mandibular position

TWIN BLOCK dual-arch plates with ramps, guiding the mandible forward when

the patient closes

TISSUE BORNE FRANKEL small pad against the lingual mucosa behind mandibular incisors to

stimulate mandibular posturing.serves as an arch expansion as well as jaw growthdevelops soft tissues e.g. lip competency to provide a more stable &balanced result

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Table 5 (modified from Millett, 2003)

The types of change brought about by functional appliance use are usually divided into the

following categories outlined below (modified from Ireland, 2003):

Dento-alveolar

Tipping (retraction / proclination of the incisors)

Arch expansion in the maxilla

Overbite reduction

Mesial and distal movement of the buccal segments

Skeletal & Soft tissue

Impeding maxillary growth and promoting mandibular growth

Altering condylar growth and glenoid fossa position

Increasing mandibular growth (not entirely proven)

Altering neuromuscular function to encourage bone remodelling

For sometime, orthodontic opinion has been divided over whether or not functional appliances

indeed have an effect on increasing mandibular growth (ONeill, 2004), or simply provide tipping

movements (dento-alveolar change). Although there are not enough valid studies that can be

used to measure this, a study by O'Brien in 2003 suggested that 98% of the changes are dento-

alveolar by way of tipping the teeth.

Fixed appliances are able to produce the following tooth movements (modified after Mitchell,

2007):

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First order movements

Tipping movements made in the plane of the archwire, i.e. labial/buccal-lingual/palatal

2nd order movements

Tilting movements made in the vertical plane, i.e. mesio-distal angulation

3rd order movements

Rotational movements (torque) through bucco-lingual/palatal forces.

The ability of fixed appliances to produce tooth movement in these three dimensions created the

following indications for their use (modified after Mitchell 2007):

bodily tooth movements to correct most skeletal discrepancies

tooth intrusion (and therefore overbite reduction)

tooth extrusion

tooth rotation

closure of spaces (bodily movements)

generate multiple tooth movements simultaneously (unlike removable appliances)

Self-ligating bracket systems (e.g. Damon) are an alternative to traditional straight wire

appliance systems. This more contemporary approach negates the need for wire or elastic

ligatures to hold the wire closely within the bracket slot to effect desired tooth movements. In the

Damon system there is a sliding mechanism which replaces conventional ligatures. The effect of

ligatures is friction, or resistance against the wire (Reznikov, 2010). This friction a) slows down

the alignment of the teeth, potentially increasing treatment times; and b) increases forces upon

the teeth, restricting the vascular supply (Profitt, 1993), which can add to patient discomfort

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during treatment. Another benefit ofDamon brackets include the fact that some are generally

smaller in size (as no attachment for ligatures is required), which mean reduced visibility. This

can increase patient acceptance, but not necessarily compliance which is related to the

appliance being fixed. However there is now lower profile ceramic / glass brackets (e.g.

Radiance) for conventional fixed appliance use which also offer a better aesthetic appearance

during treatment times.

As with most dental procedures there are risks associated with orthodontic treatment. Iatrogenic

(e.g. trauma to soft tissues), periodontal and enamel decalcification (i.e. oral hygiene) risks have

been highlighted earlier, where they relate more to the compliance with and the appropriate use

of an appliance.

However there are also risks associated with tooth movements. The most common of

these is root resorption (Roberts-Harry, 2004). This risk is most applicable to fixed appliances

where there is a prolonged force upon the teeth. A high level of resorption is seen in 3-5% of

orthodontic cases using fixed appliances (Roberts-Harry, 2004). Although this is hard to

manage once the harm has already occurred, it is best avoided by checking the pre-operative

radiographs for blunted, shortened, or pipette-shaped roots (Mitchell, 2007), as these are more

likely to undergo resorptive changes during treatment. This must be outlined to the

patient/parent/guardian during the consent stage of the examination. Other causes can include

a previous history of trauma to the teeth, root treatments, and previous orthodontic treatment

(Roberts-Harry, 2004).

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C onclusions

Rather than attempt to define which is the best appliance system within orthodontics, this paper

has attempted to identify the indications, limitations and risks associated with orthodontic

appliances.

The history of their use would suggest that traditionally upper removable appliances were

favoured because of their ease of construction and use, but also because there lacked an

appropriate level of postgraduate training to use fixed appliance systems that developed in the

United States (Littlewood, 2001). Cost was also a significant factor. However once the

advantages of fixed appliances became more widely recognised; the ability for appropriate

training more accessible; and associated costs reduced, a decline in the use of removable

appliances followed (Littlewood, 2001). This does not mean that they have completely lost their

place in orthodontics, as they have significant advantages over fixed treatments as outlined

within this paper. There has even begun a new trend in removable orthodontic aligners e.g.

Inman aligner, to treat mild anterior crowding in adults, and Invisalign orClearstep to treat more

demanding cases in a more aesthetic manner compared to fixed appliances.

Functional appliance use has always been limited to use in the growing patient, typically to treat

class II div I malocclusions (but also class II div II, and class III cases). There are still on going

studies that aim to answer the debate on the exact effect of functional appliances on skeletal

growth and modification, but despite the clear lack of evidence base are commonly used in

conjunction with fixed appliances to treat a wide range of orthodontic discrepancies. Regardless

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of the literature, functional appliances are able to produce significant changes in tooth position

to improve a malocclusion.

Fixed appliance use continues to rapidly change and expand. Depending on the operators

training and experience, a variety of fixed systems may be employed. We are currently seeing

an increase in the use of self - ligation systems e.g. Damon and lingual orthodontic systems.

Compared to removable and functional appliances, fixed appliances offer a wider range of

indications for use. However treatment times can range from 12 to 24 months, and the risks of

treatment can lead to severely negative effects on the dentition, such as root resorption and

decalcification. Patient selection must therefore be made very carefully to ensure that the

benefits of treatment outweigh the risks, and this applies to both removable and functional

appliances also.

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Brown K (2009) The impact of bonding material on bracket failure rate. Vital 6, 2830

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Daljit S. Gill (2008) Orthodontics at a Glance, Blackwell Munksgaard

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