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Advanced Prosthodontics > Polymers and Application for Orthodontic Aligners > Flashcards

Polymers and Application for Orthodontic Aligners Flashcards

1
Q

what are the ideal properties of orthodontic archwires

A
  • high strength
  • low stiffness
  • high elastic range
  • high formability
  • weld or solder
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2
Q

tooth movement during:

A

wire unloading or recovery

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3
Q

tooth movement related to:

A

elastic strain recovery during wire unloading

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4
Q

what wire do you use for more crowding initial stage:

A

low stiffness, higher resilience

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5
Q

what wire do you use for the final stage and final adjustments

A

high stiffness

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6
Q

similar stiffness considerations when using:

A

aligners

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7
Q

what are the advantages and disadvantages of stainless steel wire

A
  • advantages: lowest cost, excellent formability
  • disadvantages: high stiffness: high E modulus = 168-180 GPa; highest force delivery, require frequent adjustments (not low continuous force delivery), corrosion susceptibility
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8
Q

what are the advantages and disadvantages of beta titanium wire

A
  • advantages: intermediate stiffness: E modulus = about 65 GPa; intermediate delivery force
  • disadvantages: expensive, higher bracket friction
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9
Q

what is the composition of nickel- titanium wire

A
  • 55% nickel
    45% titanium
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10
Q

what are the advantages and disadvantages of nickel titanium wire

A
  • advantages: lowest stiffness: E modulus = about 35 GPa; lowest force delivery, low continuous unloading force at varying deflection, less frequent adjustments
  • disadvantages: expensive, second highest brack friction, lowest in vivo corrosion resistance (Ni release)
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11
Q

which wire has the highest to lowest 3-point bend load/deflection

A

stainless steel > beta titanium > nickel titanium

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12
Q

tooth movement with aligners no more than _____ at one time

A

0.2mm

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13
Q

more complex case:

A

more time to completion and more aligners

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14
Q

describe the treatment effectiveness of aligners

A

aligner therapy and conventional fixed orthodontics are both effective overall
- conventional fixed more effective to produce adequate occlusal contacts, control tooth torque and retention

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15
Q

similar biomechanics to wires, aligner is under load when:

A

placed onto misalinged teeth

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16
Q

teeth move during:

A

elastic strain recovery of the polymer

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17
Q

elastic strain recovery moves teeth to:

A

~ original shape of each aligner

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18
Q

aligner is worn for how long

A

about 1 week

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19
Q

what aligner system does each company use: align technology, clear correct, dentsply sirona, dynaflex, henry schein

A
  • invisalign
  • clear correct
  • SureSmile Aligners
  • EZ- align
  • SLX clear aligners
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20
Q

what are the polymer componets of the thermoplastic polymer sheets

A
  • polyurethane (PU)
  • polypropylene (PP)
  • polycarbonate (PC)
  • polyethyleen terephthalate (PET)
  • polyethylene terephthalate glycol (PETG)
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21
Q

what is the monomer/polymer of restorative composites

A
  • Bis-GMA, Bis- EMA, TEGDAM, UDMA, HEMA
  • methacrylate- based (MA) monomers that form a polymer resin network via polymerization reaction not heat forming
  • polymer resin network with fillers- composite is not a polymer only*
22
Q

what is the align 1st material

A

single layer polyurethane

23
Q

what is the modification material

A

multilayer polyurethane/copolyester

24
Q

describe the properties of multilayer polyurethane/copolyester

A
  • increased flexibility (more elastic)
  • more constant forces
  • based on peer assessment rating score: no diffrence in clinical outcomes between the 2 materials
25
besides polyurethane, other aligner manufacturers and materials:
polyethylene terephthalate; polyethylene terephthalate glycol (PETG), polycarbonate (PC), polypropylene (PP)
26
describe PETG
- most common - polyester modified with ethylene glycol to link polymer components (similar to ethylene glycol added to denture based PMMA to increase polymer stability) - PETG easier to print
27
describe thermoforming thermoplastic polymer sheets
- first used and most common - commercial lab vs in office
28
describe 3D printing orthodontic aligner fabrication
- most promising is photo-polymerization from clear resin - other possibilities include fused filament fabrication (FFF), selective laser sintering (SLS), selective laser melting (SLM), sterolithography apparatus (SLA)
29
what are the aligner material options for thermoformed
- essix plus; essix C+: polypropylene/ethylene copolymer - smart track: polyurethane/copolyester multilayer - clarity: propriety 5- layer copolymer blend - clear correct: zendura polyurethane tri-layer
30
describe the contents of Tera Harz TC-85DAC photopolymer
- urethane oligomer 20-60% - proprietary ingredient 30-80%
31
describe urethane oligomer
- oligomers and polymers are both chains of repeating units called monomers, but differ primarily in length - oligomers are short chains with a small number of repeating units, while polymers are much longer chains with more repeating units - difference in length significantly impacts properties and applications
32
what are the aligner material options for 3D printing
- Tera Harz - shape memory polymer
33
with aligners or orthodontic archwires tooth movement occurs during:
unloading or elastic strain recovery
34
unlike ortho archwires, aligners significantly affected by:
stress relaxation
35
stress (force) applied by the aligner is reduced when the aligner is subjected to:
prolonged strain over time
36
stress applied by the aligner is reduced when the aligner is subjected to prolonged strain over time. Similar issue with:
orthodontic elastics - results in loss of effectiveness
37
aligner properties affected by:
- material chemical structure - material thickness - thermoforming process - storage and loading conditions
38
describe material chemical structure of aligners
increased cross linking, increased ring structure, less flexible (lower elasticity)
39
______ material is stiffer (higher modulus)
thicker
40
describe the thermoforming process in aligners
increase in stiffness and force, more affect high pressure thermoform than vacuum formed
41
describe storage and loading conditions of aligners
- clinical application environment: wet, loaded - decreased force and modulus - recommendation to report properties only after storage in wet, loaded conditions
42
patients must wear aligners at least ________ to optimize treatment efficiency
20 hours a day (ideally 22 hours)
43
modified (higher modulus) material less affected by:
aligner removal frequency
44
what are the potential concerns related to aligners
- eluted polymer breakdown products released into oral cavity - nano- and microplastic particle (NMP) ingestion or inhalation - environmental impact of aligner therapy
45
what are the concerns with eluted polymer breakdown products release into oral cavity
- phalate free polymers may be preferable: PU, PC, PP - typically, resins for printing are more cytotoxic than thermoforming polymers - post curing and processing reduced toxicity; toxicity decreases with time
46
what is the concern with nano- and microplastic particle (NMP) ingestion or inhalation
- increased particle release with increased wear time - higher NMP levels in placenta than mothers blood
47
what are the concerns with the environmental impact of aligners
- aligners are considered medical waste - orthodontic pollution - 3D printed polymer models (Casts) - discarded aligners - left over aligner waste related to thermoformed aligners - water waste after thermoforming aligners - plastic cases - proposed recycling programs
48
due to limitations of aligner therapy the treatment often includes bonded composite resin attachments to:
enhance tooth movement in more complex cases
49
what are the examples of attachments
- invisalign attachments - 3M clarity precision grip
50
what are consideration factors in attachments
shape, dimensions, placement
51
the composite resin used for attachments is ______ compared to restorative material
the same
52

Advanced Prosthodontics (15 decks)

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