Removable Appliances Flashcards
Name 3 types of orthodontic appliances
- Removable appliances
- Upper removable
- Lower removable
- Retainers
- Fixed appliances
- Functional appliances
What is a removable appliance?
Removable appliances are orthodontic devices which can be taken out of the mouth by patient for cleaning
What is the mode of action of removable appliances?
Tip teeth around a fulcrum (usually about half way up the root)
Name 4 complex movements fixed appliances can cause
- Bodily movement
- Rotation
- Intrusion / Extrusion
- Root control
What is bodily movement?
Tip of the tooth and root move in the same direction
Name 5 advantages of removable appliances
- Simple to use
- Less chairside time than fixed appliances
- Less demanding on oral hygeine than fixed appliances
- Relatively simple to add pontic teeth
- Well accepted by patients
Why is there less chairside time when using removable appliances rather than fixed appliances?
Manufacturing is carried out outside of the clinical area
Name 4 disadvantages of removable appliances
- Limited range of tooth movement
- Require more laboratory time which is costly
- Lower removable appliances are uncomfortable
- They are removable
Name 4 reasons why removable appliances are in declining use
- Fixed appliances now more efficient
- Postgraduate orthodontic training courses are longer
- More cases treated by specialists
- Poorer treatment outcomes with removable appliances
Name 3 components of removable appliances
- Active components
- Retentive components
- Baseplate
Name 4 potential active components of a removable appliance
- Springs
- Screws
- Labial bows
- Elastics (rarely used)
Describe springs which are used in removable appliances
- 18:8 stainless steel (18% Cr, 8% Ni)
- Corrosion resistant
- Usually 0.5mm or 0.7mm thickness
- Optimum force is 25-60g
- 1mm per months for movement
Describe the principles of changing the force of Cantilever Spring
- Increasing diameter by 1 unit increases force to the power of 4
- Increasing length by 1 unit decreases force to the power of 3
Describe adjustment and activation of springs
- 0.7mm requires less activation than 0.5mm
- Usually aim to have 2-4mm activation
- Too small is rapid force decay as tooth moves
- Too large is difficulty to insert appliance
Describe the principles of activation
Direction of force applied is perpendicular to the tangent at the point of contact
What is the function of retentive components of the removable appliance?
Retain the appliance in the mouth
Name 3 types of clasps used on removable appliances
- Adams clasps
- Southend and Half-Jackson (incisors)
- Ball ended clasps
Describe an Adams Clasp
- Engage undercuts on molars or premolars
- 0.7mm SS
- Arrow head should engage undercut but should not impinge on soft tissues
What is a baseplate made of?
Cold cured acrylic resin
Name 3 functions of baseplates
- Hold various components together
- Anterior biteplane
- Posterior biteplane
What is the function of anterior biteplane?
Reduce a deep overbite
What is the function of posterior biteplanes?
Temporarily produce a vertical opening between the anterior teeth to allow proclination of lingually placed upper incisors
Name 6 most widely used biteplanes
- Anterior / Posterior biteplanes
- URA - Midline expansion screw
- Palatal springs to procline upper incisors
- Palatal finger spring
- Robert’s retractor
- Buccal canine retractor
Describe how an anterior biteplane can correct a deep overbite
- Posterior teeth separated by 2-3mm
- Disclusion of the posterior teeth
- Allows increased eruption of posterior teeth
- Ensure opposing teeth contact and overbite corrected
Describe how midline expansion appliances work
- Used for correction of crossbite
- Crib 6s and 4s (or Ds)
- Midline screw adjusted by patient once or twice per week
- 1 turn of screw expands by 1mm
Why may a posterior biteplane be build into a midline expansion appliance?
Discludes the posterior teeth to allow free movement and expansion
Describe palatal finger spring retractor
- Retracting canines and premolars
- Crib 6s
- 0.5mm springs
- Activate by 1/2 width of canine or premolar
Describe Robert’s Retractor
- Retracting incisors in Class II Div 1 relationship
- Crib 6s
- 0.5mm labial bow supported by SS tube
- Should be just behind incisal edges when passive
Describe buccal canine retractor
- Retracting canines to relieve crowding or reduce overjet
- Crib 6s
- 0.7mm springs
- Activate by 1/3 width of the canine
Describe the clinical procedure of a removable appliance
- Impression using alginate
- Appliance design on the lab form
- Lab casts up a working model one which appliance constructed
What is the clinical procedures when fitting a removable appliance?
- Check patient details
- Check baseplate (height baseplate)
- Insert and check retention
- Activate active components
Describe 5 instructions which should be given to patients following the fitting of a removable appliance
- Full time wear including while eating
- Removed only when cleaning or sport
- Contact orthodontist if any problems
- Brush teeth properly after each meal if possible
- Diet advice and OHI
Describe the follow up procedures for a removable appliance
- 4 to 6 week intervals
- Check for ulceration or discomfort
- Assess progress
- Check retention
Name 4 signs appliances are not being worn
- No tooth movement
- Patient unable to speak with appliance
- Springs still active
- Patient has difficulty inserting and removing appliance
Name 4 things to do when it is obvious a patient is not wearing their appliance
- Reinforce instructions to patient and parent
- Adjust if necessary
- Don’t carry out extractions until patient definitely wearing full time
- Reconsider whether patient is suitable for treatment
