Abrasion. finishing and margination Flashcards
what are finishing and margination procedures used to do
- reduce excess restorative material. margination: specifically at the margins
- develop appropriate occlusion and contour
- smooth any roughness
what is an abrasive material composed of
- particles of sufficient hardness and sharpness to cut or scratch a softer material
how is finishing and margination accomplished
- with rotary cutting instruments for amalgam restorations
- round bur = for occlusal stress
- fine-fluted carbide bur = for interproximal overhangs
- greenies and brownies to finish
what is used for finishing composite restorations
- cuttlebone, greenies and brownies
why is proper finishing important
- improves aesthetics
- decreases tarnish and corrosion
- improves health and surrounding tissue
- increases the longevity of the restoration
what are the goals of finishing
- remove excess material
- smooth roughened surfaces
- produces an aesthetically pleasing appearance with minimum trauma to hard and soft tissues
what are the benefits of smooth restorations
- resists accumulation of soft deposits and stain
- less irritating to the gingival mucosa and tissues
- more resistant to the effects of corrosion and tarnish, surface breakdown because of a more polished surface
what is finishing
- the process uses a diminishing series of abrasive to:
- contour the restoration
- remove surface scratches and stain
- bring a lister to the surface
what are the 3 factors that affect abrasion
- rate of abrasion
- number of particles
- pressure and speed
what is rate of abrasion determined by
- size of the particles
- irregularity of the particles
what does the size and irregularity of the particles determine
- the depth of the scratches in the material being abraded
- therefore, the amount of the material being removed
what is hardness
- the ability of a material to resist abrasion
what is the Moh scale
- ranks materials by their relative abrasion resistance
what is the hardest of all minerals
- diamond
- 10 on the Moh scale
what is topaz on the Moh scale
- 8
what is apatite on the Moh scale
- not hydroxyapatite, the mineral
- 5
what is gypsum on the Moh scale
- 2
what are considerations in manipulating an abrasive
- size of the particles: large = more abrasive, small = less abrasive
- shape of the particles: irregular = more abrasive, regular = less abrasive
how are coarse to fine abrasive particles measures
- in micrometers
- coarse = 100um and over
- medium = 20-100um
- fine = 20um to sub micron sizes
what does grit refer to
- size of the abrasive particles
what in dentistry is used with various degrees of coarseness
- trophy paste
- abrasive disks
- rotary diamonds
- finishing strips (half fine and half coarse)
- metal finishing strips (3 levels of abrasives)
what happens when we increase the concentration (numbers) of the abrasive to contact the surface
- faster the surface will be abraded
how do we decrease the concentration (number) of abrasive particles
- dilution (water)
what will happen if we increase the speed of the abrasive
- increases the rate of abrasion
- produces frictional heat - detrimental effects on the tooth and patient comfort
what will happen if we increase the pressure of the abrasive
- deeper scratches
- less control of the amount of material being removed
- decreases tactile sensitivity
overall, what does the amount of material being removed depend upon (4 factors)
- hardness of material being abraded
- characteristics of the particles in the material doing the abrading
- number of particles in the abrading material
- speed of the rotating device and the amount of pressure applied
what are the 3 delivery designs of abrasives
- loose abrasives
- bonded abrasives
- coated abrasives
what are loose abrasives and how are they classified
- can be either powders or liquids
- classified by grit/particle size: coarse, medium, fine, superfine
how are loose abrasives applied
- with wheels
- brushes
- cups
- soft pads
what are bonded abrasives
- abrasive particles are uniformly incorporated onto a shape
- shapes are:
- points
- disks
- cups
- brushes
- wheels
what are the 3 types of coated abrasives
- rotary disks
- finishing strips
- lightening strips
what are finishing strips
- safe-sided because coated on one side only to protect the adjacent tooth
- flexible: paper or plastic, but not sterilizable
what are lightening strips
- sterilizable
- more abrasive
- safe-sided
- less flexible
- metal
what materials are commonly used in abrasives
- diamond
- carbide finishing burs
- silicon carbide
- aluminum oxide
- sand
- silicon dioxide
- pumice
- rouge
- tin oxide
- calcium carbonate
how does diamond come prepared for abrasives
- loose: fine particles come in a paste for polishing composites and porcelain restorations
- bonded: diamond burs
- coated: lightening strips
how does carbide finishing burs come prepared for abrasives
- 7-30 cutting flutes
- higher the #, the finer the final finish
- 7 cutting flutes = 9 Moh Scale
how does silicon carbide come prepared for abrasives
- Moh scale = 9.5
- synthetic
- very hard and efficient finishing disks or rotary devices
how does aluminum oxide come prepared for abrasives
- white and tan powders used in blasting restorations
- burley wheels = aluminum oxide impregnated rubber wheels
how does sand come prepared for abrasives
- Moh scale = 7
- coated disks and strips (hand held finishing)
how does silicon dioxide come prepared for abrasives
- Moh scale = 7
- prophy paste
how does pumice come prepared for abrasives
- Moh scale of 6
- flour of pumice = extremely fine
- used in prophy paste
how does rouge come prepared for abrasives
- Moh scale = 5 to 6
- iron oxide/block form
how does tin oxide come prepared for abrasives
- Moh scale = 2-3
- extremely fine abrasives
- polishing agent for enamel and restorations
- comes in a powder
- mixed with a water or glycerine
how does calcium carbonate come prepared for abrasives
- Moh scale = 3
- chalk
- prophy paste
- dentifrice
what is prophylaxis paste
- 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
how do we begin polishing
- by selecting the least abrasive paste which will remove the stain
- apply as wet as possible using low speed and light touch
what is margination
- the process of removing restoration pre maturities to bring the restoration flush with the cavosurface tooth structure
what is margination based upon
- clinical and radiographic findings
what are clinical considerations for marginations
- biofilm trap and interferes with flossing
what instruments do you need for margination
- amalgam knife
- scalers
- files
- rotary cutting diamonds
- carbide burs
how do you use handcuffing instruments for margination
- begin apical to the margin of the restoration
- use a shaving motion
- move in diagonal overlapping strokes
what are considerations for finishing procedures for restorations
- choose: the abrasive agent appropriate for finishing the material
- start: with the more abrasive agent going to the least abrasive agent (with margination)
- care: must be taken to remove all of the abrasive agent last used or it will continue to abrade the surface being polished
- anatomic form: of the tooth makes a smooth continuous line flush with the tooth surface
- ditch or gouge: take care not to ditch or gouge the softer cementum surface or the restoration itself
- contact area: do not need to finish the contact area because polishing this area may result in an open contact
when should you finish an amalgam
- 24 hours after insertion
- during an oral prophylaxis recall
how do you complete amalgam finishing
- evaluating cavosurface margins for excess material
- remove as indicated
what dies amalgam finishing begin with
- special multi tufted finishing burs
- bonded and coated abrasives greater than 25 um
what does amalgam finishing end with
- bonded
- coated
- loose abrasives from 20 um - sub micron particle size
what are the 3 steps for composite finishing
- initial finishing: marginal and occlusal excesses are removed with diamonds or multi tufted carbide burs
- intermediate finishing: flexible discs - coarse to superfine
- final finishing: sub micron aluminum oxide-based polishing paste applied with soft cups and felt pads
how do we finish gold alloys
- burley wheels on a slow speed handpiece
- followed by a rouge on a rag wheel (not intramurally)
how do we finish a porcelain restoration
- rubber polishing points and wheels designed for porcelain are used for finishing
- diamond polishing paste
what are the 5 materials we do not polish
- composites
- glass ionomers
- compomers
- porcelain
- gold alloys
what do we polish
- 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
how does air polishing work
- uses a combination of:
- sodium bicarbonate
- aluminum trihydroxide
- air
- water
- under pressure of 40 psi
how does air abrasion work
- uses:
- compressed air
- 27-50 um aluminum oxide powder
what PPE should we use in procedures that create aerosols like polishing
- normal PPE
- pre procedural antimicrobial rince
- high speed evacuation
- face shield
what should the patient be educated about
- 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
the process of abrasion can produce
- undesirable effects if not carefully controlled
the appropriate use of abrasives can
- produce a surface that will contribute to the longevity of the restoration and health of surrounding tissues
