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Dr K.R.Hassan

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TIN OXIDE SnO is an extremely fine abrasive used extensively as a polishing agent for polishing teeth & metallic ... action of abrasion & bleaching. – PowerPoint PPT presentation

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Title: Dr K.R.Hassan


1
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.

4
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.

15
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.

30
  • 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.

33
  • ZIRCONIUM SILICATE
  • or zircon is an off-white mineral.
    It is frequently used as a component of dental
    prophylactic pastes.

34
  • 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.

35
  • 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.

36
  • 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.

37
  • It is available as an abrasive in coated discs,
    bonded instruments.

38
  • 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.

41
  • 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.

42
  • 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.

43
  • 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.

44
DENTIFRICES
  • Dentifrices are available as toothpastes, gels
    powder.

45
  • 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

46
  • more than rough surfaces.
  • finally, dentifrices act as vehicles for
    delivery of therapeutic agents e.g. fluorides,
    tartar controlling agent, desensitizing agent
    etc.

47
  • 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.

48
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

51
  • 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.

56
  • Toothbrushing frequency duration.
  • Patients coordination mental status.
  • INTRAORAL FACTORS
  • Saliva consistency quantity.
  • Xerostomia induced by drugs, gland pathology
  • or radiation therapy.

57
  • Dental deposits e.g. pellicle, plaque, calculus
  • their presence, quantity quality.
  • Exposure of dental root surfaces.
  • Presence of restorative materials, dental
  • prostheses, orthodontic appliances.

58
THANKYOU
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