Week 6- Removable Appliances Flashcards
What are reasons for decline in use of removable appliances?
- Developed poor reputation
- Used inappropriately
- Technical advances to fixed appliances have made tx more efficient
- Relative costs of fixed appliances reduce
What are advantages of removable appliances?
- Removable for socially sensitive occasions
- Short chairside time for adjustment
- Move blocks of teeth efficiently
- Can remove occlusal interferences
- Can provide good anchorage with use of plate
- Cheap
What are disadvantages of removable appliances (6)?
- Heavily dependent upon patient compliance
- Unable to perform complex tooth movements
- Affect speech in short term
- Limited use in lower arch
- Require a laboratory to fabricate
- Difficult to repair
What are indications for removable appliances (9)?
- Growth modification during mixed dentition stage (functional appliances)
- Limited tooth movement (tipping)
- Correction of individual tooth positions
- Arch expansion
- Differential eruption of teeth
- Retention after comprehensive orthodontic treatment
- Crossbites
- Increase overjet and overbite
How can anterior bite planes treat deep bite?
Upper incisors contacting on bite plane, and molars are disengaged leading to over eruption of molars (and some lower incisor intrusion)
What are the components of a removable appliance?
- Active
- Retentive
- Anchorage
- Baseplate
How are stainless steel wires made
Made by drawing metal through series of dies
How does stainless steel wire become work hardened?
- As wire passes through die
- Bending loops in wire (outside of loop becomes work hardened)
What happens when stainless steel wire becomes work hardened?
Becomes more springy but also more brittle, making it more prone to fracture.
What happens when stainless steel wires becomes less work hard? How is this achieved?
Annealing (heating wire) reduced work hardening. This reduces brittleness but also springiness.
How does stainless steel wire become springy/brittle vs no spring/ductile?
Springy, brittle: Work hardening
No spring, ductile: Annealing
What are the components of a spring?
- Tag (embedded in baseplate)
- Coil (active part, compresses when activated, tends to open)
- Arm (undergoes slight bending, rigid lever)
How does the arm length on a spring impact?
Longer arm, greater range of action.
Since when has use of removable appliances been in decline?
1970’s
What are indications for anterior bite planes?
Increased overjet & overbite
What happens when there is intrusion force placed on lower incisors (e.g. anterior bite plane)
if intrusion force placed on lower incisors, it will create moment. Tip lower anteriors forward to help correct overjet.
What are contraindications for anterior bite plane?
If teeth are already quite retroclined in upper arch and proclined in lower arch
What has happened in this case?
There was increased overjet but upper teeth were already retroclined and lower teeth proclined. By retroclining the upper teeth further, it has lead to deepened bite as the result from the removable appliance was unstable. Teeth have relapsed into worse position.
What is the appliance used for in this case?
Posterior teeth moved buccally to correct unilateral cross bite
What can be used to correct single tooth crossbite?
Upper removable appliance (URA)
What are active components?
Springs
Screws
Bows
What are retentive components?
Clasps
Bows