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Relatively, quick

to make =

reduces patient

waiting time.

Correct small

malocclusion.

(Overbite, eliminate

occlusal

interference).

Easy cleaning.

Relative low

cost.

Can alter and

affect speech.

Limited uses on

the lower arch.

Cooperation and

certain skill

needed from

patient.

Only small

movements

possible.

‘Simple tilting

movements, rotations,

intrusive and extrusive

movements, apical

bodily movements,

only really for upper

labial teeth.’ (J D Muir, R T Reed, 1979).

Often used in

addition to Fixed

Mechanotherapy.

Used after

orthodontic

surgery to

maintain teeth in

correct position.

Key

Blue = Positives of Removable Orthodontics

Red = Negatives of Removable Orthodontics

Yellow = Uses of Removable Orthodontics

Space closure

(better with

fixed

orthodontics).

Information was found in – Orthodontics Principles and Practice,

Basavaraj Subhashchandra Phulari, 1st edition, 2011, Jaypee Brothers Medical Publishers.

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“A device placed inside the mouth to correct or alleviate malocclusion and

designed to be removed or replaced by the patient.”

(Mosby’s Medical Dictionary,

8th Edition, 2009, Elsevier)

‘An invention serving a

particular purpose, used

to perform one or more

relatively simple tasks.’

‘Faulty contact

between the upper

and lower teeth when

the jaw is closed.’

‘To remove the errors

or mistakes.’

‘Separated in relationship

by a given degree.’

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Base Plate:

This component is the largest of all, and

connects all other components together in

a single functioning unit.

This unit is HeatCure Acrylic Resin, which

is a polymer and monomer mix, then when

heated for 15minutes at 45⁰C will bind and

become solid.

When designed well, it helps to give;

retention, anchorage (stopping undesirable

drifting of teeth) and helping to spread a

‘more uniform force over the palate’ –

reducing stressed points which could cause

pain for the patient.

Adams clasp:

It is a Retentive component, due to the ability

to incorporate wire in the undercut zone.

Recommended wire diameter is 0.7mm (6’s) +

0.6mm (4’s) – must give sufficient force.

There are 3 main areas to the Adams clasp:

The Arrowhead part of the clasp fits

mesio-bucaally and disto-buccally.

Therefore creating a passive force,

which will retain the device without

mechanical/strenuous force.

The Connecting Bridge, connects the

arrowheads, horizontally in the middle

third area of the crown of the tooth.

Two Retentive Arms (distal and

mesially between adjacent teeth) with

two retentive tags (which ensure that

the acrylic can flow underneath the

arms = more retention).

Picture was taken from (The Moodle area of Principles of Dental Technology, Handbook for coursework).

Information was found in – Orthodontics Principles and Practice,

Basavaraj Subhashchandra Phulari, 1st edition, 2011, Jaypee Brothers

Medical Publishers.

http://www.slideshare.net/ricobenavides/copy-removable-

orthodontic-appliances

Occlusal Rests:

Acts as a brake, stopping the teeth from

erupting upwards, due to the force from the

mid-line screw.

Expansion Screw:

An Active Component used to expand the

Removable Orthodontic appliance.

The device is in two halves and connected

by a triple ended screw, the central area

of the screw has hole into which an

external key can be used to tighten the

device methodically.

It could be said that a spring screw would

give a ‘constantly even amount of force

which can then be delivered with lighter

forces’.(S. Momeni Danaei, M. Hematian, etal,

2009).

Mattress Spring:

It is an Active component, due to the role that it plays in

moving the two centrals mesially.

This type of spring can be used here due to the device being in

the palate of the mouth, giving space for the ‘U’ loops

extending to the retentive arm.

Recommended wire diameter is 0.7mm – must give sufficient

force.

Bite Plane:

The purpose of this Retentive component is to occlude the anterior

lowers earlier which ensures to put the posterior teeth out of

occlusion. Because otherwise there would possibly be occlusal

interference with the device. (W.J.B.Houston,C.D.Stephens etal, 1992).

Also to continue encouraging the patient to bite into the corrected

position. This will allow time for facial muscular adaptation to the

new position. (Jonathan Sandler, David DiBiase, October 1996).

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Active Components:

Mattress spring: This spring is activated by compressing the legs together - the labial force can then be exerted through the free end which is

touching the palatal aspect of the teeth, moving them anteriorly. ‘It is recommended that 0.6mm stainless steel wire be used, for sufficient force

to be exerted without too much stiffness which is what 0.7mm would provide’ (http://www.homesteadschools.com/dental/courses/OrthodonticsII/Chapter01.html).

Mid-line screw: for this component to work the base plate must have been sawn in half, after the appliance has been acrylated. This allows the

screw to push out laterally causing the plate to ‘expand’. Which is why it is so important for the occlusal stops to be in place holding the

anchorage teeth in position. ‘For the activation to begin the dentist will most likely insert the device into the patient’s mouth in a passive state or

with slight activation to allow the patient to get comfortable with the device. The patient will then use a screw to tighten up the 3-pinned screw, and they will adjust the device on prescription of the dentist’. (J D Muir, R T Reed, 1979)

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Anchorage

Definition = ‘The resistance to displacement offered by an anatomical structure used to help move a tooth’ (http://medical-

dictionary.thefreedictionary.com/anchorage).

For teeth to be moved, sufficient force is needed in a certain direction, for this to occur, correctly, we use the given rule ‘an equal and opposite force is

needed’ (Jason B. Cope, March 2005). Otherwise no pressure is applied and the tooth movement will not happen.

‘Anchorage is far easier in a fixed device as mechanics such as the new implant miniscrews technique would take away the need for patient compliance

and gives the best source of anchorage intra-orally possible’. (Chang HP, Tseng YC, March 2014)

In the appliance the sources of anchorage comes from the:

Adams cribs; the legs with tags are embedded in the acrylic base with the bridge, arrowhead and upper retentive

arms around the tooth crown.

The occlusal stop, on the same posteriors, sufficient anchorage for the movement of two anteriors.

Classification of Anchorage according to Moyer’s (Italics = Applied to the case in hand specifically).

Orthodontics. Part 9: Anchroage control and distal movement, D.Roberts-

Harry & J.Sandy, British Dental Journal, Volume 196, No.5, March 13 2004)

(Orthodontics Principles and Practice, Basavaraj Subhashchandra Phulari, 1st edition, 2011, Jaypee Brothers Medical Publishers).

According to the jaws involvement:

Intra-maxillary anchorage: where teeth from the same arch, as the teeth that are being moved, are used as

anchorage. It’s dependent on; size of the root area i.e. how stable they are compared to the teeth that are

being moved. A certain amount of teeth are needed to be incorporated into the anchorage system, as well as

the base plate, for there to be substantial ‘anchorage’. Our anchorage is all on the upper arch.

Inter-maxillary anchorage = teeth on the opposing arch.

According to the manner of the force application:

Simple: preferably twice the amount of teeth are used to create a suitable anchorage unit, for resistance

utilization in tipping. There are 4 cribs in total, on the 4’s + 6’s for the movement of 2 teeth.

Stationary: here it is the resistivity of the anchorage unit (teeth) to bodily, for the movement of other teeth.

Reciprocal: resistance here is given by two malposed i.e. incorrectly aligned teeth units, moving towards a

more normal occlusion.

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According to the No. of anchorage units:

Simple = ‘resistance provided by a ‘single’ tooth with more alveolar support than that of the tooth being move’.

Compound = ‘2+ teeth, with greater anchorage/alveolar support are used to move a unit of 2+ teeth with less

alveolar support’.

Multiple = ‘when more than one type of resistance units are needed for a suitable level of anchorage’.

According to the site of anchorage:

Intra-oral Anchorage: ‘When teeth/roots, alveolar and basal bone and perioral musculature is used

individually or as a coalition to create an anchorage unit’. Oral Mucosa (hard palate) is used here due to

sufficient depth.

Extra-oral Anchorage: ‘normally shown in the form of headgear attached to the teeth via a face-bow, using

tubes on the headgear as attachment points or the device can be an ‘all-in-one’ piece’.

1. Cervical = applied via an elastic strap or spring around the neck.

It is not to be used with removable devices, as it can lead to them dislodging in the mouth.

2. Occipital = applied via a head-cap placed around the occipital bone area of the skull i.e. the back.

Positives only really include that it is easy to fit.

Easily dislodged, low level of anchorage given.

3. Variable = applies force between the cervical and occipital.

Positives include that it is highly secure and comfortable with an array of variations to produce tipping

movements/extrusions.

However it can be seen as more intrusive for the patient and takes longer to fit. But the positives

certainly would help to reassure the patient of a more positive outcome with this device.

4. Reverse = used in mesial movement of teeth. This method uses intra-oral hooks instead of the face-bow

which may be a huge advantage in the patient’s eye.

Muscular Anchorage: when the perioral musculature is used as anchorage.

Orthodontics. Part 9: Anchroage control and distal movement, D.Roberts-

Harry & J.Sandy, British Dental Journal, Volume 196, No.5, March 13 2004)

(Orthodontics Principles and Practice, Basavaraj Subhashchandra Phulari, 1st edition, 2011, Jaypee Brothers Medical Publishers).

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Practical work Evaluation - Z-Spring for Correction of Maxillary Central Incisors.

I started with the Adams cribs (0.7mm stainless-steel wire), which were to be seated around the 4’s and 6’s. I believe that once I

learned how to handle the pliers and wire with greater agility then they became easier to make. The main areas of the crib that

needed greatest attention is the: height of the retentive arms – ensuring that they don’t tower above the crown which would

disrupt occlusion, I found this difficult to begin with, but discovered to achieve this, I needed to make smaller tighter arrowheads

which meant that the retentive arms could begin lower. (fig1)

Then a certainty is that the legs coming down into the palate don’t touch the gingiva on the model, as acrylic wouldn’t be able

to flow under and could then lead to irritation of the gums and recession. However they mustn’t be too high, as I found when

trimming my acrylated base, a leg became visible therefore not having the 0.5mm coverage needed (fig2). This was an easy fix, I

first roughened up the area with a bur, then mixed up some more acrylic and placed over the area. Another issue was that I often

didn’t angulate them anteriorly enough that they might have caused an issue when trimming the base, as you must ensure that

the base didn’t creep past the hard-soft palatal border.

I also found that my bridges were just above the 1/3 – ½ crown height recommended, which could also cause occlusion problems.

This I also related to arrowheads being too tall (fig3).

Fig1

Fig2

Fig3

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Once Adams cribs were made, then a Z-spring (0.5mm stainless-steel wire) was needed. After all the stress of the

cribs this metalwork was greatly appreciated to make. However I noticed when the device was acrylated, that I hadn’t

placed this component adjacently posterior to the centrals so that the active arm was touching, therefore I have

ended up with a non-active device (fig4).

Once all appliances were on the model, then they were waxed on, to ensure that they didn’t move whilst acrylating and some areas needed to be free of

acrylic so that they were ‘active’. I.e. the coils and active arm of the Z-spring (fig6).

I also placed a strip of work around the labial and buccal surfaces of the teeth, I was

told that this would help to support them and reduce acrylic getting in between the

teeth. However I don’t believe that I was successful in this, as I broke 2 anteriors when

removing the set acrylic appliance (fig5).

The acrylating wasn’t too much of a trouble, although it would have been a good idea to use a tool to remove any unnecessary acrylic i.e. over the palatal

border and on crown surfaces to reduce later grinding time. The acrylic only needs to be up to half tooth height and on the palatal surface. The model is

then placed into a water bath for 15 minutes at 45⁰c.

The appliance is then ground using a tungsten-carbide bur to shape and soften edges, an area for attention is the base, I found that mine was too thick

and therefore would be found heavy for the patient.

Pumicing is then done to remove scratches and soften all of the none-working surfaces, here I noticed that I had pumiced a line into the appliance. To

remove it was simple, just apply the ‘correct’ method of circular motions. I would certainly say that I had learned from this appliance a few steps in

which to make the whole process more efficient and some areas of the process to take time and look better at the work before moving on. Setting myself

little steps of completion helped me in later work, so that I never needed to go back a stage or ended up doing a repair before it was even finished.

Acrylic border;

behind is

retained in

acrylic, infront is

allowed to be

active.

Fig4

Fig5 Fig6

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Bibliography:

Books:

J D Muir, R T Reed, 1979, Tooth Movements with Removable Appliances, 1ST Edition, Kent, Pitman Medical.

W.J.B.Houston, C.D.Stephens, Walter Jack Tulley, 1992, Textbook of Orthodontics, 2nd Edition, University of Michigan, Butterworth-Heinemann.

Mosby Staff, 2009, Mosby’s Medical Dictionary, 8th Edition, Missouri, Elsevier.

Basavaraj Subhashchandra Phulari, 2011, Orthodontics Principles and Practice, 1st Edition, New Delhi, Jaypee Brothers Medical Publishers.

Journals:

D. Roberts-Harry & J. Sandy, March 13 2004, Orthodontics. Part 9: Anchorage control and distal movement, British Dental Journal, Volume 196 No.5

Jonathan Sandler, David DiBiase, October 1996, The inclined biteplane - a useful tool, American Journal of Orthodontics and Dentofacial Orthopedics,

Volume 110 Issue 4.

Jason B. Cope, March 2005, Temporary anchorage devices in orthodontics: A paradigm shift, Seminars in Orthodontics, Volume 11 Issue 1.

Chang HP, Tseng YC, March 2014, Miniscrew implant applications in contemporary orthodontics, PubMed

(http://www.ncbi.nlm.nih.gov/pubmed/24581210).

S. Momeni Danaei, M. Hematian, M. Oshagh, Morteza Oshagh, A. Saboori, A. Zade, October – December 2009, In vitro evaluation of force-expansion

characteristics in a newly designed orthodontic expansion screw compared to conventional screws, Indian journal of dental research, pg.247.

Internet pages:

29/12/2013, http://www.homesteadschools.com/dental/courses/OrthodonticsII/Chapter01.html), General orthodontic knowledge.

29/12/2013, http://medical-dictionary.thefreedictionary.com/anchorage, Definitions for medical words.

02/04/2014, http://www.slideshare.net/ricobenavides/copy-removable-orthodontic-appliances, Wire diameters.