Orthodontic Appliances Flashcards by Robyn Harvey

there are two types of functional appliances, what are they?

removable
fixed

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what are removable appliances?

orthodontic appliances (braces) which are not attached to the teeth and can be removed for cleaning and sporting activities

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what are the different types of removable appliances?

conventional removable appliances
removable functional appliances
removable retainers
aligner treatment

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what are the 4 key components of conventional removable appliances?

B - baseplate
A - active component
R - retentive components
A - anchorage

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what do active components include?

springs - e.g. Z springs
screws - e.g. midpalatal screw
bows - e.g. labial bows

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the force produced by the component is dependent on what?

length of wire
radius (diameter) of wire
elastic modulus (stiffness) of wire

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the force delivered by springs is worked out by what formula?

F = E.d.r4/L3

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What does the formula for the force delivered by springs stand for?

F = force
E = stiffness of wire
D = deflection of wire
R = radius of wire
L = length of spring

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if you increase the length of wire, what happens to the force?

lighter force exerted

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if you double the diameter of the wire, what happens to the force?

x 16 increase in force

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if you double the length of the wire, what happens to the force?

x 8 reduction in force

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the larger the diameter of the wire, the more/less deflection is required?

less

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what does retentive components include?

southend clasps
adams clasps
delta clasps
ball ended clasps

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what is the baseplate?

made of acrylic
holds the components together
can incorporate bite planes (posterior and anterior)
provides anchorage for the appliance

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what is the purpose of an anterior bite plane?

Prevents posterior teeth from making contact
Good for patients who grind and clench their teeth
Reduces muscle activity
Overcomes deep overbite
Helps with TMD
Permits further eruption of posterior teeth
Permits intrusion of anterior teeth

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what is the purpose of a posterior bite plane?

Corrects anterior open bites
Permits further eruption of anterior teeth
Permits intrusion of posterior teeth

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what is anchorage?

the resistance to unwanted tooth movements

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how would you increase anchorage?

clasping more teeth
moving only one or 2 teeth at a time
using lighter forces

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what are the advantages of removable appliances from the patient’s perspective?

can remove for cleaning
can remove for sport/wind instruments

what are the advantages of removable appliances from the orthodontic perspective?

good anchorage
can move blocks of teeth
cheap
less chairside time than fixeed appliances
easy to adjust

what are the limitations of removable appliances from the patient’s perspective?

dependant on patient co-operation
temporary effect on speech/eating
lower removable appliance not well tolerated

what are the limitations of removable appliances from an orthodontic perspective?

limited ortho movement - no bodily movement tipping only
retention post correction can be difficult
requires good technical support

what is the main type of functional removable appliance in the UK

twin block

how does a twin block work?

works by posturing lower jaw forward, the stretched musculature and soft tissues creating a force which is transmitted to the dentition
soft tissue envelope around teeth is changed =, resulting in tooth movement, establishment of new occlusal relationship and reduction in overjet

what is the active component of twin blocks

midpalatal screw

what is a southend clasp used for?

retention in the anterior region

what is an adams clasp used for?

for retention on posteriors - often first molar - retentive v shaped loops

what is a delta clasp used for?

retention of posteriors - retentive loops are closed triangle shaped

what are ball ended clasps used for?

placed interproximally, used whenever additional retention is required

what are the common problems faced with removable appliances?

poor patient compliance breakage of appliance appliance is loose excessive tilting of teeth candida infection gingival inflammation

what are removable appliances most commonly used for?

anterior cross bite

what is the key difference between conventional removable appliances and functional removable appliances?

a conventional removable works by applying force directly to the teeth through screws or springs it has no change in terms of musculature or ligaments

what is an example of a fixed functional appliance?

herbst

what is a fixed appliance?

any appliance thats attached to the teeth by bands/bonds and brackets

how does a fixed appliance work?

moves teeth by interaction between the wire and the brackets and bonds/bands

what are othodontic wires made up of?

nickel titanium stainless steel

what are the most common types of fixed appliances?

conventional metal fixed appliance (train tracks) ceramic fixed appliances trans-palatal arch quad helix rapid maxillary expansion temporary anchorage device (miniscrews)

what are the advantages of fixed appliances?

can treat a wide variety of malocclusions optimal and precise tooth movements can use with auxiliaries for complex malocclusions can diverge roots to create space for implants can close space bodily can use sectional or full arch not as bulky in mouth/easier to tolerate wearing than removable

what are the limitations of using fixed appliances from the patients aspect?

demineralisation/caries gingivitis periodontal destruction soft tissue trauma pulpal necrosis root resorption gingival recession

what are the limitations of using fixed appliances from the practitioner's point of view?

orthodontic appliances can cause damage if used incorrectly practitioner can increase risk of root resorption/pulp death practitioner skill affects end result both health and aesthetics

what are the 2 ortho treatment phases?

active treatment retention phase

what is the biggest worry after orthodontic treatment has been carried out?

relapse

how do you prevent relapse?

retainers should be worn 7 nights a week for life

what are the 2 types of removable retainers?

hawley clear plastic

what are the 3 types of fixed retainers?

twist-flex ortho-flex memotain (NiTi)

what are fixed retainers good for?

severe rotations diastemas (spaces)

how does a conventional metal fixed appliance work?

most commonly made from stainless steel and attached onto teeth using composite resin orthodontic wire (archwire) is tied (or ligated) into the bracket using coloured elastic rings as treatment progresses the orthodontist will progress to thicker wires which can place greater forces onto the teeth (tightening)