by dr k r hassan head science of dental materials department r i h s islamabad n.
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FINISHING & POLISHING MATERIALS. By Dr K.R.Hassan Head Science of Dental Materials Department R.I.H.S Islamabad. FINISHING: Process of removing surface defects/scratches. POLISHING: Polishing is the process of providing luster or gloss on a material surface.

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by dr k r hassan head science of dental materials department r i h s islamabad

FINISHING & POLISHING MATERIALS

By

Dr K.R.Hassan

Head Science of Dental Materials Department

R.I.H.S

Islamabad

slide3
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.

goals
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.

benefits of finishing polishing
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.

factors affecting rate of abrasion
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

slide12
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.

slide14
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.

classification of abrasives
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

slide16
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.

types of abrasives
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.

slide20

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.

slide24
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.

slide27
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.

slide29
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.

slide31
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.

slide32
TRIPOLI

is derived from a light-weight, friablesiliceous 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.

slide33
ZIRCONIUM SILICATE

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

slide34
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.

slide35
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.

slide36
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.

slide38
ALUMINUM OXIDE

Fused aluminum oxide was the secondsynthetic 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.

slide40
ROUGE

Fe2O3is 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.

slide41
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.

slide42
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.

slide43
Abrasive pastes have several disadvantages like
  • they are relatively thick & so don’t 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.
dentifrices
DENTIFRICES

Dentifrices are available as toothpastes, gels & powder.

slide45
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

slide46
more than rough surfaces.
  • finally, dentifrices act as vehicles for delivery of therapeutic agents e.g. fluorides, tartar controlling agent, desensitizing agent etc.
slide47
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.

composition
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

slide49
Colorants e.g. Food colors

purpose appearance

Flavoring e.g. Oils of spearmint, peppermint or

cinnamon

purpose flavor

Humectant e.g. Sorbitol, glycerin

slide50
purpose maintains moisture content

Water e.g. Deionized water

purpose suspension agent

Binder e.g. Carrageenan

purpose thickener, prevents liquid-solid

separation

slide51
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

slide52
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.

toothbbrushes
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.

slide55
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.

slide56
Toothbrushing frequency & duration.
  • Patient’s coordination & mental status.

INTRAORAL FACTORS

  • Saliva consistency & quantity.
  • Xerostomia induced by drugs, gland pathology

or radiation therapy.

slide57
Dental deposits e.g. pellicle, plaque, calculus

their presence, quantity & quality.

  • Exposure of dental root surfaces.
  • Presence of restorative materials, dental

prostheses, & orthodontic appliances.