Ortho lab Flashcards
What are the components of stainless steel?
Iron - 72%
Chromium - 18%
Nickel - 8%
Titanium - 1.7%
Carbon - 0.3%
What is the function of chromium in SS?
Adds corrosion resistance
What do we mean by “hard” stainless steel and why do we use it for orthodontic appliances?
Hard means the SS has been cold worked - cold working increases strength.
It gives the material its spring properties and allows it to be bent into desirable positions.
Define overjet and what the ideal is.
Overjet - misalignment in the horizontal relationship between U+L incisors i.e. how much they stick out.
Ideal is 1-2mm
What are the active components?
The components that move teeth through application of forces.
What size of wire are active components made out of?
0.5mm
What are retentive components?
Ones that are resistant to displacement force
What are the 5 displacement forces of an orthodontic appliance?
Talking
Gravity
Biting
Tongue
Active components
What is anchorage?
Resistance to unwanted tooth movement
*Newton’s 3rd law
What is the baseplate of an ortho appliance?
Connector - holds components together
What is the main source of anchorage in an ortho appliance?
The baseplate
Why should an orthodontic appliance only move 1 or 2 teeth?
To assist with anchorage. You may get too much unwanted tooth movement if you try to move too many teeth
EVERY ACTION HAS AN EQUAL AND OPPOSITE REACTION.
What would happen if you applied too much force to a tooth/ tried to move it too quickly?
Run the risk of tooth necrosis as the blood and nerve supply could be cut off if moved too quickly.
What is the main tooth movement you can achieve with a removable ortho appliance?
Tipping/ tilting
What tooth movement is nearly impossible to achieve with removable ortho appliances?
Rotation
What are some advantages of removable orthodontics?
Cheaper than fixed
Non-destructive to tooth surface
Shorter chairside time required
OH easier to maintain
Excellent anchorage
Less specialised training required to manage
What are some disadvantages of removable orthodontics?
Non-compliance - patient can take out
Less precise control of tooth movement
Only 1-2 teeth can be moved at a time
Technical staff required to construct appliances
Difficult to correct rotations.
What type of PMMA is used for removable ortho and why?
Self-cure
Very quick to make - only 15 minutes
What is the mnemonic for the technical instructions for making a removable appliance?
ARAB
Active components
Retentive components
Anchorage
Baseplate
What are the 10 steps of fitting a removable appliance?
Check the patient and appliance match
Check the appliance matches the design specifications
Inspect appliance and look for sharp areas
Check the integrity of the wirework
Try in the patient’s mouth and check for blanching
Check the posterior retention - Adam’s clasp - check/ adjust flyovers then arrowheads
Check the anterior retention
Activate the appliance - 1mm per month
Demonstrate insertion and removal of the appliance - get the pt. to show them doing this correctly
Book a review appt. in 4-6 weeks to re-activate appliance as will be passive by this time.
How does the baseplate provide anchorage?
The baseplate distributes the force
What does ID tubing do?
Encases thin (0.5mm) wire - gives strength and rigidity in the buccal aspect of buccal canine retractors.
What are some problems with a high flyover on an Adam’s clasp?
Changes occlusion
Metal fatigue can occur due to repeated stresses
Wire distortion
Damage to soft tissues
What is a Flat Anterior Bite Plan used for and how does it work?
Used to correct overbites.
Corrects by the lower molars continuing to erupt while the upper molars do not.
Why is it unlikely that lower anteriors will not over-erupt with Posterior Bite Plane (PBP)?
Lower anteriors are not in occlusion anyway and they tend to have a maximum eruption level that they do not tend to pass.
What gauge of wire should be used for primary dentition?
0.6mm
What is the definition of an overbite?
The VERTICAL misalignment between upper and lower teeth.
i.e. over-closing
What is the definition of a posterior crossbite?
Lateral (buccal or lingual) misalignment of the posterior teeth.
The maxillary teeth would be more lingual the mandibular teeth on one or both sides - which is abnormal.
What is the definition of an anterior crossbite?
A malocclusion where the anterior teeth are misplaced labially/ palatially with reference to the opposing teeth.
What is the function of titanium in SS wires?
Prevents precipitation of chromium-carbides at grain boundaries when heated
What are some reasons for stainless steel fracture?
Mechanical abrasion
Over-worked
Weld decay
Fatigue
What is the Bauschinger effect?
If a coil is activated in the same direction then the elastic recovery is greater than if deflected in the opposite direction
What are the 10 things you should instruct a patient on aftercare for a URA?
Avoid sticky foods
Take out during sports
Wear all the time - compliance is necessary for success of treatment
Saliva may be increased
Speech may be impaired - practice speaking
Emergency contact details incase of breakage
Will feel bulky
Will feel uncomfortable - shouldn’t last long but this is how you know its working
Keep in for eating but remove afterwards to clean
