BONDING

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BONDING
Dr. Raghuwar D Singh Associate Professor
Prosthodontic Department King Georges Medical
University UP, Lucknow
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ADHESION

1. Sound tooth structure must be conserved.
2. Optimal retention must be achieved.
3. Microleakage must be prevented.

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MECHANISM OF ADHESION

• Factors in achieving adhesive bonds
• Wetting
• Interpenetration (formation of a hybrid zone)
• Micromechanical Interlocking
• Chemical bonding

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ACID ETCHING TECHNIQUE

• Most effective ways of improving the marginal
  seal
• mechanical bonding b/w Resin and Enamel .
• Mode Of Action
• It creates micro-porosities by etching of the
  enamel .

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• Etching increase the surface area .
• Etched enamel has a high surface energy and
  allows a
• resin to wet the surface penetrate into
  micro-
• porosities.
• Resin Tags are approx 6microm in diameter and
  10-20micro m in length.

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• Acid Used
• 37 Phosphoric acid is most commonly used acid
  .
• Supplied in gel form .
• Brush or Syringe is used for application on the
  
• enamel .

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• Procedure
• Dry the enamel surface completely .
• Length of application 60 sec.
• but may be 15 sec.
• After etching , dried enamel shows white ,
  frosted
• appearance .
• If enamel surface is contaminated, re-etching
  for 10 sec .

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BONDING AGENTS

• Enamel bond agents
• Dentin bond agents

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ENAMEL BOND AGENTS

• Hydrophobic
• Unfilled resin
• Bis GMA
• TEGDMA

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DENTIN BOND AGENTS
Dentin
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Problems in bonding to dentin

• Dentin is a dynamic tissue that shows changes due
  to ageing, caries or restorative procedures.
• Dentinal tubules are filled with dentinal fluid
  which constantly flow outward from the pulp.
• Dentin has considerable amount of organic
  material water.
• Dentin is close to pulp, so different chemical
  used for bonding and etching may irritate the
  pulp.

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role of smear layer -

• Whenever tooth surface is cut with hand or rotary
  instruments, it causes small particles of the cut
  tooth surface to the tooth producing the smear
  layer.
• Smear layer is defined as any debris, calcific in
  nature produced by reduction or instrumentation
  of enamel of dentin or cementum.

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• Retention of smear layer-
• 1) lowers dentin permeability
• 2) prevent decrease in bond strength
• 3) lowers effect of pulpal pressure on bond
  strength
• Recent generations adhesives involves
  modification of smear layer to facilitate bonding.

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• It has two phases -
• Solid phase- made up of cutting debris, primarily
• denaturated collagen and
  mineral.
• Liquid phase- made up of tortuous fluid filled
  channels
• around the cutting
  debris.
• Bacteria entrapped in smear layer can survive and
  multiply beneath the restoration.

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Conditioning of dentin

• It is defined as an alteration of dentin surface
  including the smear layer with the objective of
  producing a substrate capable of micromechanical
  and possibly chemical bonding to dentin adhesive.
• Acid conditioners
• Phosphoric acid,
• Citric acid,
• Nitric acid,
• Oxalic acid, and
• Hydrochloric acid.

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• Chelators-
• Remove the smear layer without
  decalcification or significant physical changes
  on underlying dentin substrate.
• Best known chelator conditioner is EDTA.
• Thermal conditioning-
• Recent trend is to use lasers in conditioning
  of teeth.
• Studies have conformed increased bond strengths
  with lased dentin compared to those with unlased
  dentin.

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• The molecule designed for dentin bonding were
  represented by an M-R-X molecule.
• M- methacrylate group for bonding to resin matrix
  of composite resin
• R- spacer such as hydrocarbon chain
• X- functional group for bonding to organic or
  inorganic component of dentin.

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ETCHENTS / CONDITIONERS

• ORGANIC ACID- Maleic acid, EDTA, Citric acid,
• Tartaric acid.
• POLYMERIC ACID- Poly acrylic acid.
• INORGANIC ACID- Phosphoric acid, Nitric acid.

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• Hydrophilic

Primers/ Conditioners
Bonding liquid
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PRIMERS

• NTG-GMA
• PMDM
• BPDM
• PENTA
• HEMA

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ADHESIVE RESINS

• Hydrophobic monomers -
• BIS-GMA
• UDMA
• Diluent -
• TEGDMA
• Wetting agent -
• HEMA

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DENTIN BONDING AGENTS

• First generation
• Second generation
• Third generation
• Forth generation
• Fifth generation

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MCQs

• Most effective way of improving the marginal seal
  and bonding between restorative resin and Enamel
  is
• 1. Using adhesive
• 2. Acid etching
• 3. Using both adhesive and acid etching
• 4. None of the above

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• Most commonly used acid for acid etching
  technique
• 1. 35 Phosphoric acid
• 2. 37 Phosporic acid
• 3. 37 Hydrochoric acid
• 4. 35 Citric acid

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• Chelators most commonly used to remove the smear
  layer
• 1. EDTA
• 2. BIS GMA
• 3. HEMA
• 4. Oxalic acid

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• The nature of enamel bonding agents should be
• 1. Hydrophilic
• 2. Hydrophobic
• 3. Depending on the condition of enamel
• 4. Neutral

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• The length of application of acid in acid etching
  technique should be
• 1. 10 Second
• 2. 60 Second
• 3. 90 Second
• 4. 120 Second

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THANK YOU