DENTAL LUTING CEMENTS

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DENTAL LUTING CEMENTS

• Presented by
• Dr. Mohamed Abd-el Aziz
• Lecturer of fixed prosthodontics

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• Cement is a plastic paste of a fine powder and
  liquid which hardens to a solid mass. Cements are
  used to retain restorations and occupy marginal
  voids.
• Cementation should be a procedure which allows
  full seating of a crown with no damage to the
  tooth or restoration.

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• Requirements of an ideal luting cement
• Adhesion to tooth structure and restoration.
• Biological compatibility with the pulp.
• High mechanical properties in terms of tensile,
  compressive strength and modulus of elasticity.
• Insolubility in the oral fluids.
• Long working time.
• Low film thickness.
• Low viscosity and easy flow.
• Translucency. and radio-opacity
• Anticariogenic property.
• Easy removal of excess cement.

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• 1- Good Adhesion
• To the underlying abutment preparations, the
  surface of which may include enamel, dentin or
  core material (amalgam, composite resin, glass
  ionomer, ceramic or a cast core of precious or
  non-precious alloys).
• To the restoration material which may be
• - Metallic (precious or non-precious alloys).
• - Non-metallic (porcelain or resin).

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• Mechanism of Adhesion Mechanical bond, by
  mechanical interlocking into the surface
  roughness and irregularities present on the tooth
  and fitting surface of the restoration.
• True adhesion (chemical adhesion) which involves
  chemical reaction or attraction between the
  adhesive material and the surfaces to which it
  will bond. It does not need or involve mechanical
  interlocking with surface roughness.

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• 2- Biological compatibility with the pulp
• The luring cement should be nonirritant to the
  pulp.
• 3- High mechanical properties
• in terms of compressive, tensile strength and
  modulus of elasticity to resist the forces of
  mastication.
• 4- Insolubility
• A more important property of a luting cement is
  its resistant to solubility and disintegration in
  the oral cavity.

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• 5- Long work time
• It is an extremely important property. Working
  time is that time during which the viscosity or
  consistency of the mix is such that it flows
  readily under pressure to form a thin film. Short
  working time creates a problem when cementing a
  long span bridge (multiple units).

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• Factors governing the working time
• Powder/liquid ratio.
• Rate of addition of the powder to the mix
  (introduction of the powder into the liquid in
  small increments will increase the working time).
  
• Spatulation time
• The most effective method of controlling the
  working time is to regulate the temperature of
  the mixing slab. Frozen slab technique

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• 6- Low film thickness
• acceptable range (20-40 microns) to permit crown
  to seat adequately.
• To obtain the thinnest possible cement film
  between the tooth and restoration it is important
  to bring about the greatest cement flow during
  the initial stage of the cementation process.

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• Several variables affect the thickness of the
  cement film remaining between the prepared tooth
  surface and a restoration.
• Powder/Liquid ratio.
• Amount and duration of the pressure applied
  during seating of the restoration.
• The degree of taper of the preparation.
• The viscosity of the cementing medium.
• The internal relief by
• Enlargement of the interior of the casting by
  electrical or chemical stripping.
• Enlargement of the die, by a spacing material or
  by die relief before the wax build up.

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• The thinner the cement film the better the
  cementing and retentive action and the greater
  chance of permanence of the restoration because
  air spaces, voids and structure defects are
  minimized in a thin film

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• 7-Low viscosity and easy flow
• The luting cement should have a suitable
  viscosity to enable it to flow easily over the
  adherent surface. The initial viscosity of the
  cementing medium had a major effect on the
  seating of the crown.
• Cements that have a prolonged low viscosity phase
  should have benefits in crown seating.
• Low viscosity allows crowns to seat better than
  high viscosity fluids.

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• 8- Translucency
• The luring cement must be translucent and not
  opaque.
• 9- Anticariogenic property
• The luting cement should contain fluoride in its
  composition. Fluoride ions are released for
  prolonged periods and taken up by the underlying
  tooth structure leading to increased resistance
  to recurrent decay.
• 10- Easy removal of excess cement
• Interproximally and from the gingival sulcus,
  lack of thorough removal of excess cement leads
  to soft tissue irritation and serious periodontal
  problems.

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• Today there are five major categories of dental
  cements for luting purposes.
• They are
• Zinc phosphate.
• Zinc polycarboxylate.
• Zinc oxide and eugenol
• Conventional.
• Reinforced.
• IV. Glass ionomer
• Conventional.
• resin-modified glass ionomer.
• V. Composite resin
• Conventional.
• Adhesive.

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• I. Zinc phosphate cement
• Composition
• The powder is composed of about
• 90 percent zinc oxide
• and 10 percent magnesium oxide.
• The liquid is an aqueous solution of phosphoric
  acid containing about 30 to 40 percent water.

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• Manipulation
• Dispense the proper amount of powder and liquid
  on a cool, dry, clean and thick glass slab.
• The powder is divided into small quantities (each
  about one sixth of the total mix) and add them
  one at a time to the liquid.
• After the first increment of powder has been
  incorporated for 15 to 20 seconds, a second
  increment is added, and so on.
• During mixing, a large surface area (60010 of the
  slab) should be used so that the heat of the
  exothermic setting reaction will be dissipated.
• The mixing continues until all powder has been
  incorporated (about 90 seconds).
• The cement is of proper consistency if it pulls
  into a thread of about 20 mm in length before
  snapping back onto the slab.

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• Properties of zinc phosphate cement
• 1- Adhesion (onlv mechanical)
• It is not adhesive and do not form chemical bond
  with tooth structure and the restoration. The
  retention depends on the mechanical interlocking
  of the set material with surface roughness on the
  preparation and restoration.

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• 2- Biological compatibility
• It is irritant to the pulp due to the initial
  acidity .at the time of placement which leads to
  pulp irritation. Application of several
  successive thin layers of varnish will protect
  against pulpal irritation from infiltration of
  the phosphoric acid. Frozen slab technique have
  the' benefit of accelerating pH rise of the
  cement and decreasing the irritation to the pulp.

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• 3- Mechanical properties
• Has high mechanical properties particularly the
  compressive strength. The use of cool glass slab
  or frozen slab technique allows an additional
  powder to be incorporated in the liquid and
  improving the compressive strength of the cement.
  
• 4- Solubility
• It is a soluble cement, greater resistance to
  solubility is obtained by incorporating more
  powder into the liquid (cool glass slab and
  frozen slab technique).

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• 5- Working time
• It has a reasonable and long working time about
  5 minutes.
• 6- Film thickness
• has a thin film thickness. The film thickness
  is
• 25 µm.
• 7- Viscosity and flow
• Zinc phosphate cement is dilatant, i.e.
  viscosity increased with increase shear rate of
  mixing. The viscosity rise steadily during
  setting. The cement provides a good flow.

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• 8- Translucencv
• It is not translucent but the set cement is
  opaque
• 9- Anticariogenic property
• It has no Anticariogenic property.
• 10- Removal of excess cement
• Easy removal of excess cement because it develops
  brittle properties.

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• II. Zinc oxide-Euegenol cement
• Type I
• Unmodified zinc oxide eugenol cement which is
  designed for temporary cementation because of the
  palliative effect on the pulp and the low
  strength properties allowing non traumatic
  removal of the restoration.
• Type II
• Reinforced zinc oxide-eugenol for final
  cementation either by incorporation of a polymer
  or by the addition of alumina to the powder and
  EBA (orthoethoxy benzoic acid) to the eugenol
  liquid.

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• Composition of EBA
• The powder is composed of
• zinc oxide,
• fused quartz or alumina and .
• hydrogenated resin.
• The liquid is
• eugenol and
• orthoethoxy benzoic acid.
• Manipulation
• Rapid .,incorporation of the powder into the
  liquid and then continue to spatulate for 60
  seconds.

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• Properties of EBA
• 1. Adhesion (only mechanical)
• It is not adhesive and do not form chemical bond
  with tooth structure or the restoration.
• 2. Biological compatibility
• It is extremely biocompatible and provides a
  palliative and sedative effect on the pulp.
• 3. Mechanical properties
• It has limited strength properties. The
  mechanical properties are inferior to other
  cements.
• 4. Solubility
• It is a soluble cement mainly due to elution of
  eugenol.

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• 5. Working time
• It has a short working time.
• 6. Film thickness
• It has a high film thickness (50 µm).
• 7. Viscosity and flow
• It has a good flow.
• 8. Translucency
• It is not translucent, because the set cement
  is opaque.
• 9. Anticariogenic property
• It has no Anticariogenic property.
• 10. Removal of excess cement
• Difficult to remove excess cement.

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• III. Polycarboxylate cement
• Composition
• The powder is composed of
• zinc oxide
• containing less than 10 magnesium oxide.
• The liquid is a 40 aqueous solution polyacrylic
  acid.
• Water settable versions of this cement is
  available.

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• Manipulation
• All powder should be incorporated to the liquid
  quickly and at once, and the Spatulation should
  be completed within 30 seconds to provide the
  maximum lengths of working time.
• The proper consistency of the cement if follow
  the cement spatula about 20 mm in length when the
  spatula is rapidly moved Upward.

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• Prosperities of zinc Polycarboxylate cement
• Adhesion (chemical and mechanical)
• It is the first truly adhesive cement which is
  introduced by Smith in 1968. It adheres to enamel
  and in a lesser way to dentine due to chemical
  bond between the cement and the contained calcium
  of the tooth structure.
• To achieve good adhesion to tooth structure, a
  clean surface is necessary in order to attain
  intimate contact and interaction between the
  cement and the tooth.

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• A recommended procedure is to apply a 10 percent
  polyacrylic acid solution (conditioner) for 10 to
  15 seconds followed by rinsing with water to
  remove the smear layer.
• The mixed cement should be applied to the tooth
  as soon as possible and be used only as it still
  appears glossy on the surface otherwise poor
  adhesion may result. The cement does not adhere
  well to gold or porcelain.
• Techniques of tin plating of the fitting surface
  of the restorations have been developed to
  improve the adhesion. The cement provides strong
  adhesive bond to non-precious alloy.

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• 2- Biologic compatibility
• Excellent biocompatibility because the cement is
  not irritant and there is lack of post operative
  sensitivity
• There is rapid rise of pH to a value of 6 and 7.
• The large molecular size and low toxicity of the
  polyacrylic acid.
• Its ability to complex with proteins limits
  diffusion through the dentinal tubules.
• 3- Mechanical properties
• Lower compressive and modulus of elasticity but
  higher tensile strength compared to zinc
  phosphate.
• 4- Solubility
• It is a soluble cement.

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• 5- Working time
• It has an extremely short working time about 2.5
  minutes, which makes the seating of a long-span
  bridge difficult.
• 6- Film thickness
• it has a low film thickness (25 µm).
• 7- Viscosity and flow
• Polyacrylic acid solutions are viscous which
  affects the ease of mixing of the cement. The
  cement is pseudoplastic i.e. the viscosity
  decreased with increase shear rate of mixing.

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• 8- Translucency
• It is not transluencet but the set cement is
  very opaque because of the large quantity of
  un-reacted zinc oxide that is present.
• 9- Anticariogenic propertv
• It has no Anticariogenic property.

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• 10- Removal of excess cement
• It is difficult to remove excess cement because
  the cement does not develop brittle properties.
  During setting, the cement passes through a
  rubbery stage. The excess amount that has
  extruded at the margins should not be removed
  while the cement is in the rubbery stage since
  there is danger that some of the cement may be
  pulled out from ,beneath the margins, leaving a
  void, and leading to recurrent caries. Excess is
  not removed until the cement becomes hard.

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• IV. Glass ionomer cement
• Types of Glass Ionomer
• Type I
• For the cementation of metal restorations
• Type II
• Designed for restoring areas of erosion near the
  gingiva.
• Type III
• Used as liners and dentin bonding agents.

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• Composition
• A- Conventional glass ionomer
• The powder is a calcium fluoro-aluminosilicate
  glass.
• The liquid is polyacrylic or polymaleic acid.
• The glass ionomer cements are supplied as a
  powder and a liquid or as a powder- that is mixed
  with water. The polyacrylic acid is formulated in
  the powder.
• The liquids of these products may be water or a
  dilute solution of tartaric acid in water (water
  settable cement). Several products are
  encapsulated.

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• B- Resin-modified Glass ionomer cement
• They are glass ionomer cements with the addition
  of a small quantity of resin components such as
  (HEMA) or BIS-GMA some of the water . component
  of the conventional glass ionomer cement is
  replaced by a water /HEMA mixture.
• The amount of resin in the final set cement is
  between 4.5 to 6.

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• Manipulation
• The powder is divided into two equal parts and
  mixed with the liquid using the spatula. The
  first increment is rapidly incorporated in 10
  seconds and the second increment incorporated for
  a further 10 seconds.
• The proper consistency of the cement is reached
  if it follows the cement spatula about 20 mm in
  length when the spatula is rapidly moved upward.

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• Properties of glass ionomer cement
• 1- Adhesion (chemical mechanical)
• It is the second truly adhesive cement which is
  introduced by Wilson and Kent in 1972. It adheres
  to enamel and to a lesser way to dentin due to
  chemical bond between the cement and the
  contained calcium of the tooth structure.
• The cement does not adhere to gold or porcelain.
  It provide strong bond to non-precious alloys
  specifically after sandblasting with 50 µm
  alumina.

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• 2- Biological compatibility
• The cement is not irritant because the liquid is
  polyacrylic acid. It may cause prolonged
  postoperative sensitivity varying from mild to
  severe.
• To reduce the incidence of post operative
  sensitivity the following procedure is suggested
  
• Slight hydration of the tooth before cementation
  by placing a drop of water on the tooth during
  mixing, this is gently blown off just before
  placing restoration on the tooth.
• Allowing the cement to set hard to the touch,
  plus one minute before removing the excess.
• Placing a varnish on the margins of the
  restoration after removing the excess cement. .

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• 3- Mechanical properties
• High compressive and tensile strength but lower
  modulus of elasticity.
• A disadvantage of glass ionomer cement is the
  slowness with which the ultimate properties are
  developed.
• N.B. The resin modified glass ionomer cement
  provides rapid early development of strength.

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• 5- Working time
• It is not too long about 3.5 minutes.
• The use of water settable cement will improve and
  prolong the working time.
• N. B. The resin modified glass ionomer cement
  allows for longer working time.
• 6- Film thickness
• Low film thickness (20 µm).

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• 7- Viscosity and flow
• Glass ionomer showed an initial slow rise in
  viscosity with a subsequent increase. It has a
  high and excellent flow.
• 8-Translucency
• It is translucent due to the presence of glass.
  The refractive index of glass ionomer is similar
  to enamel and dentine and is an advantage when it
  is used with the porcelain labial margin
  technique.
• N.B. A disadvantage of the resin-modified glass
  ionomer cement is the decrease of translucency
  because of difference in refractive index between
  the polyacid matrix and polymerized monomer.

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• 9- Anticariogenic property
• It has an Anticariogenic property and is related
  to its fluoride content.
• 10- Removal of excess cement
• Easy removal of excess cement because it
  develops brittle properties.

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• v. Composite Resin Cement
• Composition
• (A) Conventional composite resin
• (powder/liquid or two paste systems)
• One major component is a diacrylate oligomer
  diluted with lower molecular weight
  dimethacrylate monomers.
• The other major component is silanated silica or
  glass.
• The initiator accelerator is peroxide-amine.

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• (B) The adhesive composite resin systems
• 1- Panavia
• the powder consists of 75 quartz filler and
  initiators. The liquid consists of aromatic
  methacrylates, aliphatic methacrylates, phosphate
  monomer activators and stabilizers.
• 2- 4-META cement
• Is formulated with methyl methacrylate monomer
  and acrylic resin filler and is catalyzed by
  tri-butyl-borone.

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• 3- Rely-X-Unicem
• Is a self adhesive dual-cure resin cement.
  Conditioning of the prepared tooth structure is
  not necessary with the Rely-X-Unicem (no
  etching-priming or bonding). This cement is
  distinguished by
• Its unique moisture tolerance.
• Little risk for postoperative hypersensitivity.
• Dimensional stability.
• Fluoride ions release.
• Available in several shades.

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• Composition
• Monomer Phosphorulated methacrylates, which can
  generate selfadhesion.
• The acidic nature of the monomer allows for
  demineralization of the tooth surface and then
  penetration of the cement into the tooth surface.
  Once polymerized micromechanical retention is
  achieved between the cement and the tooth
• Filler technology Inorganic alkaline fillers 72
  by weight.

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• Manipulation
• Chemical, light cured and dual..cured (chemical
  light cure) systems are available in composite
  resin cement.
• The chemically activated, is supplied as powder
  and liquid or two pastes systems. The two
  components are combined by mixing on a treated
  paper and for 20 to 30 seconds. For the adhesive
  composite resin (Panavia). The entire amount of
  powder "is rapidly wetted and incorporated with
  the liquid. Spatulate the mix for 60-90 seconds.
  The mix will appear very dry at first but will
  approach a smooth creamy consistency after about
  30 seconds. Once the cement has been thoroughly
  mixed, it should be spread out in a thin layer
  over the entire pad, this keeps Panavia exposed
  to oxygen thereby keeping it fluid.

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• Properties of composite resin cement
• 1 - Adhesion
• a) Conventional composite resin (only mechanical)
  
• it is not adhesive and do not form chemical bond
  with tooth structure and the restoration.
• The bond to acid-etched enamel has been far
  stronger than the dentine bond. Adhesion to
  dentine presents a more difficult problem
• Modern bonding agents have been developed to .
  adhere to dentine, via this smear layer, by
  modifying or totally removing it and infiltrating
  the exposed dentine.

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• B- Adhesive composite resin (chemical
  mechanical)
• Panavia bonds chemically as well as mechanically
  due to the addition of phosphate ester to the
  monomer.
• It is adhesive to tooth structure, silanated
  porcelain, composites and to the oxide layer on
  the metal surface.
• For non-precious alloys, such as nickel chromium
  and cobalt chromium should be sandblasted with 50
  µm alumina oxide powder .
• . For precious alloys, the gold alloys should be
  sandblasted and then tinplated (0.2-0.4 microns
  layer of tin). The cement bonds to the tin oxide
  layer which develops on the tin-plated surface.

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• 2- Biological compatibility
• Conventional and adhesive composite resin cements
  are irritant to the pulp.
• 3. Mechanical properties
• Excellent mechanical properties for the
  conventional and adhesive composite resin cement.
  
• 4. Solubility
• Composite resin cement is the' only insoluble
  cement in oral , fluids.

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• 5- working time
• Conventional Short working time.
• Adhesive (Panavia)
• Controlled working time. It has a unique
  anaerobic setting characteristic. The cement will
  not polymerize or cure as long as it is in
  contact with oxygen. This enables the clinician
  to control the working time before applying the
  oxygen-inhibiting gel (oxyguard).

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• 6- Film thickness
• Conventional High film thickness.
• Adhesive Low film thickness ( 19 microns).
• 7. Viscosity and flow
• the viscosity increases rapidly.
• 8. Translucency
• It is translucent.
• 9- Anticariogenic property
• It has no anticariogenic property except the
  most recent version that releases fluoride (e.g.
  Panavia F).

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• 10. Removal of excess cement
• Conventional Very difficult. The time of removal
  of excess cement is critical. It is best to
  remove the excess cement immediately after the
  restoration is seated. If it is done while the
  cement is in a rubbery state, cement may be
  pulled from beneath the margin of the restoration
  leaving a void and leading to secondary caries.
• Adhesive (panavia) Easy removal of excess cement
  before applying the oxygen-inhibiting gel
  oxyguard (polyethylene glycol gel).

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• Proper Selection of Luting Cements
• Currently there is no single and superior cement
  material that can perform well in all the luting
  requirements of all restorations.
• In other words, a universal utilization cement is
  not yet available. The different cements should
  be properly selected according to their merits
  for the particular cementation utilization.
• Each dentist must decide which cement to use
  based on clinical application and specific
  patient needs.

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• I- Cementation of long span bridge
• Cement requirements
• Long working time.
• High mechanical properties.
• Preferably to be adhesive.

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• Cement of choice
• Glass ionomer.
• Zinc phosphate
• Adhesive composite resin particularly Panavia in
  which we can control the working time due to its
  anaerobic setting characteristics.
• N.B. Poly carboxylate cement is not used in this
  case due to its extremely short working time and
  low strength properties. Reinforced zinc oxide
  eugenol is also not used due to its low strength
  properties and short working time.

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• II. Caries active patients (high caries index)
• Cement requirement
• Must have an anticariogenic property by releasing
  fluoride ions and inhibiting secondary caries.

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• Cement choice
• 1. Glass ionomer cement
• (conventional and resin-modified).
• 2. Composite resin that releases fluoride
  (recent version e.g. Panavia F).

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• III. Deep preparation
• Cement requirement
• Should be non irritant, palliative to the pulp.
• Cement of choice
• Polycarboxylate.
• Reinforced zinc oxide and eugenol.

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• IV. Cementation, of porcelain jacket crowns and
  porcelain laminates
• Cement requirements
• Translucency.
• Early high mechanical strength and fracture
  toughness.
• Adhesive to the treated porcelain and tooth
  surfaces.

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• Cement of choice
• Composite resin cement.
• N.B. Glass ionomer cement although it is
  translucent but has the disadvantage of slowness
  with which ultimate properties are developed. So
  when subjected to masticatory stress elastic
  deformation of the underlying cement could result
  in fracture of the brittle ceramic.

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• V- Cementation of a restoration to a core or
  crown base materials
• Cement requirement
• Adhesion to the core material.

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• Cement of choice
• according to the type of core material.
• Amalgam core
• All cements are used currently for cementation
  against amalgam core But, it is recommended to
  use high copper amalgam core With high tin
  concentration with Polycarboxylate cement since
  the high tin concentration enhances the bonding
  between amalgam cores and Polycarboxylate
  cements.

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• 2- Composite resin core
• We choose a composite resin cement because of
  the chemical similarity in composition and
  therefore it bonds chemically to the composite
  core.
• 3- Glass ionomer core
• We choose a glass ionomer cement because of the
  chemical similarity in composition leading to
  chemical bonding to the glass ionomer core.

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• 4- Cast core
• Precious cast core
• All cements used currently does not provide a
  good adhesion to gold alloys. But polycarboxylate
  cement showed a bond strength which is 4 times
  greater than that of zinc phosphate and is
  directly proportional with the percentage of
  copper present in the alloy. Adhesive composite
  resin cement has superior bonding to gold alloys.
  

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• Non precious cast core
• Adhesive composite resin, glass ionomer and
  Polycarboxylate cements provide good adhesion to
  non -precious alloys.
• Ceramic core
• We choose a composite resin cement after
  sandblasting of the ceramic core with aluminum
  oxide, followed by silane application.

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• VI. Cementation of post crowns
• Cement requirements
• High flow and ease of post cementation.
• High strength properties.
• Preferable to be adhesive.

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• Cement of choice
• Glass ionomer.
• Zinc phosphate.
• Adhesive composite resin is used for cementation
  of non-metallic posts such as zirconium oxide
  ceramic posts and carbon fiber epoxy posts.
• (N.B. Because of the lack of oxygen in the
  canal, Panavia tends to set more rapidly)

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• VII. Cementation of restoration to a Questionable
  preparation
• (Short, over convergence or to a continually
  dislodged restoration)
• Cement requirements
• Adhesive.
• Extremely strong cement (high mechanical
  properties).
• Insoluble.

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• Cement of choice
• Adhesive composite resin with pulp protection
  over deep dentinal areas.

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• VIII. Cementation of resin-bonded retainers
  (Maryland bridge)
• Cement requirements
• Adhesive to the treated metal surface and
  impregnation into etched enamel areas.
• High mechanical properties.
• Insoluble in the oral fluids.

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• Cement of choice
• The only cement of choice is the adhesive
  composite resin cement.

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• Thank You
• Dr. Mohamed Abd-el Aziz