Dr K.R.Hassan

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FINISHING POLISHING MATERIALS

• By
• Dr K.R.Hassan
• Head Science of Dental Materials Department
• R.I.H.S
• Islamabad

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• FINISHING Process of removing surface
  defects/scratches.
• POLISHING Polishing is the process of providing
  luster or gloss on a material surface.
• FINISHED POLISHED RESTORATION
• A prosthesis or a direct
  restoration whose outer surface has been refined
  to a desired state of finish.

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GOALS

• The goals of finishing polishing
  procedures are to obtain the desired anatomy,
  proper occlusion the reduction of roughness,
  gouges scratches that are produced during the
  making of the prosthesis.

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BENEFITS OF FINISHING POLISHING

• Finished polished restorations
  provide 3 major benefits of dental care
• Oral health
• A well contoured polished
  restoration resists the accumulation of food
  debris pathogens.
• Tarnish corrosion activity of
  the restorations is reduced.
• Polished restoration surfaces
  minimizes the wear rates of opposing adjacent
  teeth.

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• Function
• Rough surfaces causes development
  of high-contact stresses which hinder functions
  stabilizing contacts b/w the teeth.
• Aesthetics
• Finally, to achieve the goal of
  patients demands of a polished restoration, as
  aesthetics play a major role in dentistry.

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• Most finishing polishing in
  dentistry are performed by ABRASION.
• ABRASION
• Is the process of wear of a
  material by another material through scratching,
  chiseling or other mechanical means.

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• ABRASIVE
• Is a hard substance used for
  grinding, finishing or polishing of a less hard
  surface, or the material that causes wear is
  called abrasive.
• SUBSTRATE
• The material being abraded is
  called a substrate.
• P.S ABRASIVE IS HARDER THAN THE
  SUBATRATE.

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• EROSION
• Is caused by hard particles impacting
  a substrate surface, carried by a stream of
  either liquid or air e.g. sandblasting.
• BULK REDUCTION
• Is the process of removing excess
  material by cutting or grinding by a rotary
  instrument.

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• GRINDING
• Is the process of removing material
  by abrasion with relatively coarse particles.
  CONTOURING
• Is the process of
  producing a desired anatomical form
  by cutting or grinding.

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FACTORS AFFECTING RATE OF ABRASION

• The following factors causes changes in
  the rate of abrasion of an abrasive
• HARDNESS
• Hardness of an abrasive is
  directly proportional to the rate of its abrasion
  i.e. the harder the abrasive than the substrate
  the more abrasion will be produced.
• PARTICLE SIZE
• The particle size of a
  material is

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• Expressed in MICROMETRES.
• By convention, particles are
  classified as
• FINE 0 - 10µm
• MEDIUM 10 - 100µm
  
• COARSE 100 - 1000µm
• Larger, coarse abrasive particles will
  abrade a surface more readily than smaller
  particles , but they tend to leave more coarser
  scratches in the substrate.

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• PARTICLE SHAPE
• Sharp, irregular shaped
  particles will abrade a surface more rapidly than
  will rounded particles having dull cutting
  angles. However the former will produce deeper
  scratches than later.
• SPEED PRESSURE
• Both speed pressure are
  directly proportional to the rate of abrasion.
• At higher speed greater friction is produced,
  which tends to produce higher temperatures.
  Similarly, greater pressure causes higher
  temperatures possibly patient discomfort.

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• LUBRICATION
• Lubricants are used during
  abrasion for two purposes
• to reduce heat buildup
• to wash away debris to prevent clogging
• but too much lubrication can reduce the abrasion
  rate by preventing the abrasive from coming in
  contact with the substrate.

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CLASSIFICATION OF ABRASIVES

• Abrasives used in dentistry can be
  classified into the following three types
• FINISHING ABRASIVES
• are generally hard, coarse
  used primarily to produce the desired contours
  of a restoration or tooth preparation.
• POLISHING ABRASIVES
• have finer particle sizes
  are less hard than the finishing abrasives,
  they are used

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• to smooth surfaces roughened by finishing
  abrasives.
• CLEANSING ABRASIVES
• are generally soft materials with
  small particle sizes are intended to remove
  softer materials that adhere to the enamel or
  restorations.

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TYPES OF ABRASIVES

• A variety of abrasives are available but
  the types listed below are widely used in
  dentistry.
• NATURAL abrasives include
  
  
• ARKANSAS STONE
• is a semi translucent, light gray
  sedimentary rock mined in Arkansas. It is dense,
  hard contains uniformly textured
  microcrystalline quartz. It is used for fine
  grinding of tooth enamel metal alloys.
  

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• CHALK
• Is a white abrasive composed of
  CaCO3. Chalk is used as a mild abrasive paste to
  polish tooth enamel, gold foil, amalgam plastic
  materials.

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CORUNDUM is a
white mineral form of Al2O3. It is largely
replaced by synthetic Al2O3 in dental

applications due to its inferior physical
properties. It is used primarily for grinding
metal alloys.
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• DIAMOND
• is a transparent, colorless mineral
  composed of carbon. It is the hardest known
  substance is called a super abrasive because of
  its ability to abrade any other known substance.

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• Synthetic diamond abrasives are used far more
  commonly than natural diamond due to its
  consistent shape size low cost.
• Diamonds are mostly used on tooth structure,
  ceramics resin-based composite materials.

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• EMERY
• is a fine-grain grayish black
  corundum, used for finishing metal alloys
  acrylic resin materials.

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• GARNET
• consists of a group of different
  minerals that have the same physical properties
  crystalline forms. Minerals included in this
  group are silicates of Al, Co, Fe, Mg Mn. The
  type of garnet used in dentistry is usually dark
  red. It is used in grinding metal alloys
  acrylic resin materials.

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• PUMICE
• is a light gray volcanic rock
  derivative, used in polishing tooth enamel, gold
  foil, dental amalgam acrylic resins.

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• QUARTZ
• is a hard, colorless, transparent
  most abundant mineral. It is used mainly to
  finish metal alloys but can be used to grind
  dental enamel.

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• SAND
• is a mixture of mineral particles,
  predominantly composed of silica. The particles
  represent a mixture of colors, making it distinct
  in appearance. They are coated onto paper disks
  for grinding of metal alloys acrylic resin
  materials.

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• TRIPOLI
• is derived from a light-weight, friable
  siliceous sedimentary rock. Tripoli can be white,
  gray, pink, red or yellow. The gray red types
  are mostly used in dentistry. It is used for
  polishing metal alloys some acrylic resin
  materials.

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• ZIRCONIUM SILICATE
• or zircon is an off-white mineral.
  It is frequently used as a component of dental
  prophylactic pastes.

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• CUTTLE
• commonly referred to as cuttlefish or
  cuttle bone, is a white calcareous powder made
  from the internal shell of a Mediterranean marine
  mollusk. It is available as coated abrasive
  used for polishing metal margins dental amalgam
  restorations.

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• KIESELGUHR
• is composed of the remains of
  minute aquatic plants known as diatoms. Its
  coarser form is called diatomaceous earth is
  used as a filler in many dental materials, such
  as hydrocolloid impression materials.

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• SYNTHETIC abrasives include
• SILICON CARBIDE
• It was the first of the synthetic
  abrasives to be produced. It is available in
  green blue-black types, having equivalent
  physical properties. Silicon carbide is extremely
  hard brittle results in highly efficient
  cutting of materials, including metal alloys,
  ceramics acrylic resins.

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• It is available as an abrasive in coated discs,
  bonded instruments.

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• ALUMINUM OXIDE
• Fused aluminum oxide was the second
  synthetic abrasive to be developed. Aluminum
  oxide (alumina) is much harder than corundum
  (natural alumina) due to its purity. Several
  grain sizes are available has largely replaced
  emery for several abrasive uses. Alumina is
  largely used in dentistry to make bonded, coated
  air propelled grit abrasives. It is popular for
  adjusting dental enamel for finishing metal
  alloys, resin-based composites ceramic
  materials.

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• ROUGE
• Fe2O3 is the fine, red abrasive
  component of rouge. Like tripoli, rouge is
  blended with various soft binders into a cake
  form. It is used to polish high noble metal
  alloys.

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• TIN OXIDE
• SnO is an extremely fine abrasive used
  extensively as a polishing agent for polishing
  teeth metallic restorations. It is mixed with
  water, alcohol or glycerin to form a mildly
  abrasive pastes.

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• ABRASIVE PASTES
• The most commonly used abrasive
  pastes contain either alumina or diamond
  particles.
• Alumina pastes should be used with a rotary
  instrument increasing amounts of water.
• Diamond abrasive pastes are used in dry
  conditions.

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• Abrasive pastes have several disadvantages like
• they are relatively thick so dont readily
  gain access to embrasures.
• they tend to splatter off of the instruments.
• heat is generated when insufficient coolant is
  used or when an intermittent polishing technique
  is not used.

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DENTIFRICES

• Dentifrices are available as toothpastes, gels
  powder.

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• They are used for three important functions
• their abrasive actions provide more efficient
  removal of debris, plaque stained pellicle
  compared with toothbrush alone.
• they polish teeth to provide increased light
  reflectance superior aesthetic appearance.
• the high polish enables
  teeth to resist accumulation of microorganism
  stains

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• more than rough surfaces.
• finally, dentifrices act as vehicles for
  delivery of therapeutic agents e.g. fluorides,
  tartar controlling agent, desensitizing agent
  etc.

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• The products advertised as whitening tooth pastes
  may contain an abrasive agent alone or along with
  a chemical agent.
• The former additive acts through a
  surface stain removal mechanism, whereas the
  latter acts through a combined action of abrasion
  bleaching.

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COMPOSITION

• A typical dentifrice comprises of the following
  components
• Abrasive e.g. CaCo3, hydrated alumina/ silica
• soda bicarb or a
  mixture of these.
• purpose removal of plaque/stain
  polish
• Detergent e.g. Sodium lauryl sulfate
• purpose aids in debris removal

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• Colorants e.g. Food colors
• purpose appearance
• Flavoring e.g. Oils of spearmint, peppermint
  or
• cinnamon
• purpose flavor
• Humectant e.g. Sorbitol, glycerin

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• purpose maintains moisture content
• Water e.g. Deionized water
• purpose suspension agent
• Binder e.g. Carrageenan
• purpose thickener, prevents
  liquid-solid
• separation

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• Fluoride e.g. Sodium monofluorophosphate
• purpose prevents dental caries
• Tartar control e.g. Disodium pyrophosphate
• purpose inhibits formation of
  calculus
• above gingival margin
• Desensitizing e.g. Potassium nitrate
• purpose promotes occlusion of
  dentinal

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• tubules.
• The abrasive concentrations in paste gel
  dentifrices are 50 75 lower than those of
  powder dentifrices. So powders should be used
  more sparingly with greater caution to avoid
  excessive dentinal abrasion pulpal sensitivity.

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TOOTHBBRUSHES

• Toothbrush bristle stiffness alone have no effect
  on abrasion of hard dental tissues. However, with
  the use of a dentifrice, there is evidence that
  brush bristles bend more readily bring more
  abrasive particles into contact with the tooth
  structure. This interaction produces more
  effective abrasion cleaning action.

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• Factors Affecting Dentifrice Abrasiveness
• EXTRAORAL FACTORS
• Abrasive particle type, size, quantity in the
  
• dentifrice.
• Amount of dentifrice used.
• Toothbrush type.
• Toothbrush method force applied during
• brushing.

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• Toothbrushing frequency duration.
• Patients coordination mental status.
• INTRAORAL FACTORS
• Saliva consistency quantity.
• Xerostomia induced by drugs, gland pathology
• or radiation therapy.

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• Dental deposits e.g. pellicle, plaque, calculus
• their presence, quantity quality.
• Exposure of dental root surfaces.
• Presence of restorative materials, dental
• prostheses, orthodontic appliances.

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THANKYOU