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Dental Materials > Abrasion. finishing and margination > Flashcards

Abrasion. finishing and margination Flashcards

1
Q

what are finishing and margination procedures used to do

A
  • reduce excess restorative material. margination: specifically at the margins
  • develop appropriate occlusion and contour
  • smooth any roughness
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2
Q

what is an abrasive material composed of

A
  • particles of sufficient hardness and sharpness to cut or scratch a softer material
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3
Q

how is finishing and margination accomplished

A
  • with rotary cutting instruments for amalgam restorations
  • round bur = for occlusal stress
  • fine-fluted carbide bur = for interproximal overhangs
  • greenies and brownies to finish
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4
Q

what is used for finishing composite restorations

A
  • cuttlebone, greenies and brownies
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5
Q

why is proper finishing important

A
  • improves aesthetics
  • decreases tarnish and corrosion
  • improves health and surrounding tissue
  • increases the longevity of the restoration
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6
Q

what are the goals of finishing

A
  1. remove excess material
  2. smooth roughened surfaces
  3. produces an aesthetically pleasing appearance with minimum trauma to hard and soft tissues
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7
Q

what are the benefits of smooth restorations

A
  1. resists accumulation of soft deposits and stain
  2. less irritating to the gingival mucosa and tissues
  3. more resistant to the effects of corrosion and tarnish, surface breakdown because of a more polished surface
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8
Q

what is finishing

A
  • the process uses a diminishing series of abrasive to:
  • contour the restoration
  • remove surface scratches and stain
  • bring a lister to the surface
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9
Q

what are the 3 factors that affect abrasion

A
  1. rate of abrasion
  2. number of particles
  3. pressure and speed
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10
Q

what is rate of abrasion determined by

A
  • size of the particles

- irregularity of the particles

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11
Q

what does the size and irregularity of the particles determine

A
  • the depth of the scratches in the material being abraded

- therefore, the amount of the material being removed

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12
Q

what is hardness

A
  • the ability of a material to resist abrasion
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13
Q

what is the Moh scale

A
  • ranks materials by their relative abrasion resistance
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14
Q

what is the hardest of all minerals

A
  • diamond

- 10 on the Moh scale

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15
Q

what is topaz on the Moh scale

A
  • 8
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16
Q

what is apatite on the Moh scale

A
  • not hydroxyapatite, the mineral

- 5

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17
Q

what is gypsum on the Moh scale

A
  • 2
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18
Q

what are considerations in manipulating an abrasive

A
  • size of the particles: large = more abrasive, small = less abrasive
  • shape of the particles: irregular = more abrasive, regular = less abrasive
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19
Q

how are coarse to fine abrasive particles measures

A
  • in micrometers
  • coarse = 100um and over
  • medium = 20-100um
  • fine = 20um to sub micron sizes
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20
Q

what does grit refer to

A
  • size of the abrasive particles
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21
Q

what in dentistry is used with various degrees of coarseness

A
  • trophy paste
  • abrasive disks
  • rotary diamonds
  • finishing strips (half fine and half coarse)
  • metal finishing strips (3 levels of abrasives)
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22
Q

what happens when we increase the concentration (numbers) of the abrasive to contact the surface

A
  • faster the surface will be abraded
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23
Q

how do we decrease the concentration (number) of abrasive particles

A
  • dilution (water)
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24
Q

what will happen if we increase the speed of the abrasive

A
  • increases the rate of abrasion

- produces frictional heat - detrimental effects on the tooth and patient comfort

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25
Q

what will happen if we increase the pressure of the abrasive

A
  • deeper scratches
  • less control of the amount of material being removed
  • decreases tactile sensitivity
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26
Q

overall, what does the amount of material being removed depend upon (4 factors)

A
  1. hardness of material being abraded
  2. characteristics of the particles in the material doing the abrading
  3. number of particles in the abrading material
  4. speed of the rotating device and the amount of pressure applied
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27
Q

what are the 3 delivery designs of abrasives

A
  • loose abrasives
  • bonded abrasives
  • coated abrasives
28
Q

what are loose abrasives and how are they classified

A
  • can be either powders or liquids

- classified by grit/particle size: coarse, medium, fine, superfine

29
Q

how are loose abrasives applied

A
  • with wheels
  • brushes
  • cups
  • soft pads
30
Q

what are bonded abrasives

A
  • abrasive particles are uniformly incorporated onto a shape
  • shapes are:
  • points
  • disks
  • cups
  • brushes
  • wheels
31
Q

what are the 3 types of coated abrasives

A
  • rotary disks
  • finishing strips
  • lightening strips
32
Q

what are finishing strips

A
  • safe-sided because coated on one side only to protect the adjacent tooth
  • flexible: paper or plastic, but not sterilizable
33
Q

what are lightening strips

A
  • sterilizable
  • more abrasive
  • safe-sided
  • less flexible
  • metal
34
Q

what materials are commonly used in abrasives

A
  • diamond
  • carbide finishing burs
  • silicon carbide
  • aluminum oxide
  • sand
  • silicon dioxide
  • pumice
  • rouge
  • tin oxide
  • calcium carbonate
35
Q

how does diamond come prepared for abrasives

A
  • loose: fine particles come in a paste for polishing composites and porcelain restorations
  • bonded: diamond burs
  • coated: lightening strips
36
Q

how does carbide finishing burs come prepared for abrasives

A
  • 7-30 cutting flutes
  • higher the #, the finer the final finish
  • 7 cutting flutes = 9 Moh Scale
37
Q

how does silicon carbide come prepared for abrasives

A
  • Moh scale = 9.5
  • synthetic
  • very hard and efficient finishing disks or rotary devices
38
Q

how does aluminum oxide come prepared for abrasives

A
  • white and tan powders used in blasting restorations

- burley wheels = aluminum oxide impregnated rubber wheels

39
Q

how does sand come prepared for abrasives

A
  • Moh scale = 7

- coated disks and strips (hand held finishing)

40
Q

how does silicon dioxide come prepared for abrasives

A
  • Moh scale = 7

- prophy paste

41
Q

how does pumice come prepared for abrasives

A
  • Moh scale of 6
  • flour of pumice = extremely fine
  • used in prophy paste
42
Q

how does rouge come prepared for abrasives

A
  • Moh scale = 5 to 6

- iron oxide/block form

43
Q

how does tin oxide come prepared for abrasives

A
  • Moh scale = 2-3
  • extremely fine abrasives
  • polishing agent for enamel and restorations
  • comes in a powder
  • mixed with a water or glycerine
44
Q

how does calcium carbonate come prepared for abrasives

A
  • Moh scale = 3
  • chalk
  • prophy paste
  • dentifrice
45
Q

what is prophylaxis paste

A
  • mix: 50-60% abrasive material
  • lubricant reduces: rate of abrasion, amount of frictional heat
  • preservatives: prolong shelf life
  • flavouring and colouring: increase patient acceptance
  • Moh scale: 1-2 rankings higher than the surface they are polishing
46
Q

how do we begin polishing

A
  • by selecting the least abrasive paste which will remove the stain
  • apply as wet as possible using low speed and light touch
47
Q

what is margination

A
  • the process of removing restoration pre maturities to bring the restoration flush with the cavosurface tooth structure
48
Q

what is margination based upon

A
  • clinical and radiographic findings
49
Q

what are clinical considerations for marginations

A
  • biofilm trap and interferes with flossing
50
Q

what instruments do you need for margination

A
  • amalgam knife
  • scalers
  • files
  • rotary cutting diamonds
  • carbide burs
51
Q

how do you use handcuffing instruments for margination

A
  • begin apical to the margin of the restoration
  • use a shaving motion
  • move in diagonal overlapping strokes
52
Q

what are considerations for finishing procedures for restorations

A
  1. choose: the abrasive agent appropriate for finishing the material
  2. start: with the more abrasive agent going to the least abrasive agent (with margination)
  3. care: must be taken to remove all of the abrasive agent last used or it will continue to abrade the surface being polished
  4. anatomic form: of the tooth makes a smooth continuous line flush with the tooth surface
  5. ditch or gouge: take care not to ditch or gouge the softer cementum surface or the restoration itself
  6. contact area: do not need to finish the contact area because polishing this area may result in an open contact
53
Q

when should you finish an amalgam

A
  • 24 hours after insertion

- during an oral prophylaxis recall

54
Q

how do you complete amalgam finishing

A
  • evaluating cavosurface margins for excess material

- remove as indicated

55
Q

what dies amalgam finishing begin with

A
  • special multi tufted finishing burs

- bonded and coated abrasives greater than 25 um

56
Q

what does amalgam finishing end with

A
  • bonded
  • coated
  • loose abrasives from 20 um - sub micron particle size
57
Q

what are the 3 steps for composite finishing

A
  1. initial finishing: marginal and occlusal excesses are removed with diamonds or multi tufted carbide burs
  2. intermediate finishing: flexible discs - coarse to superfine
  3. final finishing: sub micron aluminum oxide-based polishing paste applied with soft cups and felt pads
58
Q

how do we finish gold alloys

A
  • burley wheels on a slow speed handpiece

- followed by a rouge on a rag wheel (not intramurally)

59
Q

how do we finish a porcelain restoration

A
  • rubber polishing points and wheels designed for porcelain are used for finishing
  • diamond polishing paste
60
Q

what are the 5 materials we do not polish

A
  1. composites
  2. glass ionomers
  3. compomers
  4. porcelain
  5. gold alloys
61
Q

what do we polish

A
  • amalgams with prophylaxis paste and finishing strips on IP areas avoiding the contact area
  • stained composites: avoid ultrasonic and air polishing devices
  • aluminum oxide polishing paste is best
  • polish only if stain is present
62
Q

how does air polishing work

A
  • uses a combination of:
  • sodium bicarbonate
  • aluminum trihydroxide
  • air
  • water
  • under pressure of 40 psi
63
Q

how does air abrasion work

A
  • uses:
  • compressed air
  • 27-50 um aluminum oxide powder
64
Q

what PPE should we use in procedures that create aerosols like polishing

A
  • normal PPE
  • pre procedural antimicrobial rince
  • high speed evacuation
  • face shield
65
Q

what should the patient be educated about

A
  • staining
  • dietary staining foods: pigmented beverages, pigmented foods, tobacco stain
  • each recall appt
  • abrasive home remedies: toothbrush abrasion, wear of restorations, exposed dentin and cementum
66
Q

the process of abrasion can produce

A
  • undesirable effects if not carefully controlled
67
Q

the appropriate use of abrasives can

A
  • produce a surface that will contribute to the longevity of the restoration and health of surrounding tissues

Dental Materials (18 decks)

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