Orthodontic Appliances Flashcards
there are two types of functional appliances, what are they?
removable
fixed
what are removable appliances?
orthodontic appliances (braces) which are not attached to the teeth and can be removed for cleaning and sporting activities
what are the different types of removable appliances?
conventional removable appliances
removable functional appliances
removable retainers
aligner treatment
what are the 4 key components of conventional removable appliances?
B - baseplate
A - active component
R - retentive components
A - anchorage
what do active components include?
springs - e.g. Z springs
screws - e.g. midpalatal screw
bows - e.g. labial bows
the force produced by the component is dependent on what?
length of wire
radius (diameter) of wire
elastic modulus (stiffness) of wire
the force delivered by springs is worked out by what formula?
F = E.d.r4/L3
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
if you increase the length of wire, what happens to the force?
lighter force exerted
if you double the diameter of the wire, what happens to the force?
x 16 increase in force
if you double the length of the wire, what happens to the force?
x 8 reduction in force
the larger the diameter of the wire, the more/less deflection is required?
less
what does retentive components include?
southend clasps
adams clasps
delta clasps
ball ended clasps
what is the baseplate?
made of acrylic
holds the components together
can incorporate bite planes (posterior and anterior)
provides anchorage for the appliance
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
what is the purpose of a posterior bite plane?
Corrects anterior open bites
Permits further eruption of anterior teeth
Permits intrusion of posterior teeth
what is anchorage?
the resistance to unwanted tooth movements
how would you increase anchorage?
clasping more teeth
moving only one or 2 teeth at a time
using lighter forces
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)
