Elastic Impression Materials and Denture Adhesives

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Elastomeric Impression Materials

• Dr Shujah A Khan
• MDS Resident, Dept. of Prosthodontics
• DIKIOHS, DUHS

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Elastic Impression Materials

• Hydrocolloids
• Reversible Hydrocolloids
• Irreversible Hydrocolloids
• Elastomers
• Polysulfides
• Polyethers
• Condensation Silicones
• Addition Silicones - Polyvinylsiloxanes

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Elastic Impression Materials

• HYDROCOLLOIDS
• water-based impression materials
• Colloid liquid suspension of particles
• Particles derived from seaweed kelp
• Liquid water
• GEL the rubber-like form of the material
• SOL the material in liquid solution
• Not dimensionally stable must be poured
  immediately

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Hydrocolloids

• Reversible Hydrocolloid
• Agar a gelatinous material water
• Thermoplastic NO chemical reaction
• Reversible
• Goes from gel, to sol, and back to gel,
• by raising and lowering temperature
• Dispensed in tubes syringes
• Very accurate final impression material

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Hydrocolloids

• Handling Reversible Hydrocolloid
• Special water baths with 3 chambers are used
• 1) Material is immersed in boiling tank (212F)
• for 10-20 minutes turns from gel to sol
• 2) Place in storage bath (150F)
• 10 minutes to few days remains sol
• 3) Load tray immerse in the tempering bath
  (110F) 5-10 minutes lowers temp for pt comfort

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Hydrocolloids

• Handling Reversible Hydrocolloid
• 4) Load syringe extrude onto prep site
• 5) Seat tray in mouth
• 6) Attach cooling hoses to tray
• 7) Hold firmly in pts mouth until cooled and
  transformed to gel state
• 8) Remove from pts mouth and pour immediately

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Reversible Hydrocolloid

• Advantages
• Very accurate
• Excellent compatibility with gypsum

• Disadvantages
• Labor-intensive
• Poor tear resistance
• Poor stability
• Need equipment space and very organized staff

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Hydrocolloids

• Irreversible Hydrocolloid
• ALGINATE impression material
• Formed by chemical reaction
• Powder water mixed
• NOT reversible SOL to GEL only
• Protect from inhalation
• Dispensed in cans or bulk packages
• Used when less detail is required

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Hydrocolloids

• What are indications for alginate impressions?
• Study models
• Opposing models of final casts
• Casts for mouthguards, whitening trays, custom
  trays, orthodontic appliances, provisional
  crowns, etc.
• To fabricate a direct provisional crown

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Hydrocolloids

• Handling Alginate
• Fluff powder and measure accurately
• Measure water temp!
• Mix in a flexible,
• rubber bowl
• Stir to wet powder
• Strop mixture against side of bowl to eliminate
  air bubbles
• Mix until creamy homogeneous 60 sec.

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Hydrocolloids

• Handling Alginate
• Load alginate into tray from posterior
• Press material into tray to eliminate voids
• Smooth indent alginate with wet finger
• Use extra alginate to wipe onto occlusal surfaces
  of teeth

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Taking an Alginate Impression

• Bead the tray as necessary
• Stand behind patient for maxillary (1100)
• Center tray above teeth and seat posterior
• Press tray down toward anterior and allow lip
  to cover tray material should fill vestibule
• Hold tray in patients mouth until set (2 - 3
  min)
• Loosen cheeks and lips with finger
• Remove occlusally with a firm snap

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Evaluating an Alginate Impression

• Full coverage, including retromolar area
• Tray centered
• Clear sharp impression
• No voids, air bubbles, or tears
• Has a peripheral roll (vestibular area)
• If all is OK, rinse disinfect impression,
• pour-up in stone/plaster, or store in humid bag.

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Irreversible Hydrocolloid

• Advantages
• Easy economical
• Many applications
• Patient comfort
• Excellent wetting by gypsum
• Disposable tray

• Disadvantages
• Not enough detail for final impression
• Must be poured immediately

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Hydrocolloids

• SYNERESIS shrinkage in impression due to loss
  of water from heat or exposure to air.
• IMBIBITION swelling of impression due to taking
  up moisture
• To avoid these conditions (dimensional
  distortion), pour-up immediately!

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Elastomers

• Two-paste systems
• Two tubes pastes mixed by hand
• Two putties mixed/kneaded by hand
• Cartridge Extruder Gun automix tips used
• Cartridge Motor-driven Mixer automix tips
  used
• Set by chemical reaction
• Warmth and moisture may slow setting
• Must use a tray adhesive (if tray not perforated)
• Latex may inhibit set of polyvinylsiloxanes

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Elastomers

• Elastomers are used in a two-step process
• Preliminary Impression - the material used to
  form the base or the tray material used in an
  impression usually more viscous or heavy-body
• Secondary or Wash Impression the material
  applied through a syringe around the prep site
  for detail usually less viscous
• light or medium -body.

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Elastomers

• POLYSULFIDE
• Oldest elastomeric used in dentistry
• Two pastes mix base with catalyst
• Liquid polymer with sulfhydryl group contains
  sulfur
• rubber-base impression material
• Used best with custom trays
• Other materials have replaced this one

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Elastomers

• Handling Polysulfides
• Equal lengths of pastes on pad
• Pastes are swirled together, then stropped
• Material placed in custom tray
• Take impression hold in place for up to 15 min.
• Remove from pts mouth slow steady force
• Rinse disinfect
• Pour-up impression within several hours

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Polysulfides

• Advantages
• Economical
• Good tear resistance
• Good compatibility with gypsum

• Disadvantages
• Malodor
• Stains clothing
• Long setting time
• Fair stability
• Less accurate

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Elastomers

• Condensation Silicones
• Similar to silicone rubber products (but
  non-toxic)
• Setting by-product of alcohol
• Hydrophobic results in voids in stone
• Shrinkage occurs as it sets
• Must be poured immediately
• Accurate, but slow setting time
• Replaced by improved products

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Elastomers

• POLYETHERS
• Developed in 1960s
• No reaction by-product produced
• Shorter working and setting time
• Only come in a single viscosity
• Stiff material can use a triple tray
• Very popular Impregum
• No need to pour-up immediately

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Elastomers

• Handling Polyether
• Mix equal lengths of paste or extrude through
  the automix cartridge tip
• Load syringe and apply to tooth thru tip
• Load tray and invert over area for impression
• Allow to set 4 5 minutes
• Remove from mouth
• Rinse disinfect

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Polyether Impregum
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Polyether

• Advantages
• Short setting time
• Single viscosity
• Good stability
• Good tear strength
• Clean easy to use

• Disadvantages
• Bad taste
• Most difficult to remove from mouth

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Elastomers

• ADDITION SILICONES
• Polyvinylsiloxanes silicone polymer
• Two pastes or two putties
• Hydrophobic by nature manufacturers adding
  components to increase wettability
• Very accurate fast setting
• Avoid contact with latex (gloves, rubber dams)
• Low setting shrinkage very stable

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Elastomers

• Handling Addition Silicone
• Mix equal lengths of pastes, or automix
• Apply light-body material to tooth thru syringe
• Load tray with heavy-body
• Set tray over prep site
• Set in 4 5 minutes
• Rinse disinfect

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Addition Silicone Polyvinylsiloxane

• Advantages
• Very stable
• Short setting time
• Good tear resistance
• Great accuracy
• No bad taste

• Disadvantages
• May have poor wettability
• Two pastes to mix

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DENTURE ADHESIVES
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• DENTURE ADHESIVES are materials used
• to adhere a denture to the oral mucosa.

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• MECHANISM OF ACTION
• Denture adhesives enhance retention through
  optimizing interfacial forces by
• Increasing the viscosity of the medium lying
  between the denture base and basal seal and
• Eliminating voids between the denture base and
  its basal seal.

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• Purpose of using denture adhesive
• Improved fit
• Comfort
• Improved chewing ability.

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REQUIREMENTS

• Neutral or slightly basic pH.
• Minimal toxicity to oral mucosa.
• Bond strength for 12 to 16 hours.
• Better taste and fit.
• Less expensive.

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MATERIALS USED IN DENTURE ADHESIVES

• VEGETABLE GUMS
• For example KARAYA, TRAGACANTH, XANTHAN
  and ACACIA.
• Highly water soluble in hot liquids.
• Short lived.
• Allergic reactions to reactions to karaya have
  been reported
• MODE OF ACTION
• Nonionic adhesion to both denture and mucosa.
• Very little cohesive strength.

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• SYNTHETIC MATERIALS
• For example SHORT- ACTING CARBOXY METHYL
• CELLULOSE, LONG ACTING POLY VINYL METHYL
  ETHER MALEATE and POLY VINYLPYROLIDONE.
• Washed out by saliva.
• MODE OF ACTION
• SHORT-ACTING CMC Ionic adhesion.( inc.
  viscosity) by eliminating voids.
• LONG ACTING Cohesion.

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• OTHER MATERIALS
• PETROLIUM, MINERAL OIL and POLYETHYLENE
  OXIDE are included in creams.
• SILICONE DIOXIDE and CALCIUM-STEARATE are
  included in powder to minimize clumping.
• MENTHOL and PEPERMINT OIL are used for
  flavoring, RED DYE for color.
• SODIUM BORATE and METHYLPARABEN or
  POLYPARABEN as preservatives.

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INDICATIONS

• Well made complete dentures do not satisfy
  patients perceived retention and stability
• expectations.
• Salivary dysfunction or neurological disorders.
• Xerostomia due to medication side effects.
• Head and neck resective surgery.
• Cerebrovascular accident (stroke).
• Orofacial dyskinesia.

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CONTRAINDICATION

• For the retention of improperly fabricated
  denture or poorly fitting prosthesis

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PATIENT EDUCATION

• Choice between cream and powder is highly
  subjective for individual.
• Least amount of material that is used should be
  0.5g to 1.5g/ denture unit (more for larger
  alveolar ridges, less for smaller ones).

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• POWDER FORM
• The prosthesis should be clean then moistened.
• Then a thin even coating of adhesive sprayed.
• If patient has inadequate or absence of saliva,
  sprayed denture should be moistened before being
  inserted.

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• PASTE FORM
• For pastes two approaches are possible
• THIN BEAD TECHNIQUE
• The prosthesis should be clean and dried.
• For maxilla thin beads of adhesive should be
  placed in the incisor, molar and mid-palate
  regions.
• For mandible a series of thin beads at the crest
  of ridge is recommended.

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• SPOT TECHNIQUE
• Small spots of cream are placed at 5-mm intervals
  throughout the fitting surface of the dried
  denture,

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DENTURE MAINTENANCE

• Daily removal of adhesive product from tissue
  surface.
• Prosthesis soaked in water over night, so
  readily rinsed off.
• Running hot water over tissue surface of denture
  while scrubbing with a hard toothbrush.
• Adhesive on ridge is removed by rinsing with
  warm water then firmly wiping the area with
  gauze.

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