Bonding of resin-based materials

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Bonding of resin-based materials
Libyan International Medical University
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• All modern composite restorations are based on
  effective adhesive procedures using dental
  adhesives. Dental adhesive systems are complex
  mixtures containing hydrophilic and hydrophobic
  monomers, solvents (including water), sometimes
  fillers and polymerization initiators and
  co-initiators.
• Their challenge is firstly to completely
  penetrate a hydrophilic etched tooth surface
  (enamel or dentine) to obtain an acceptable
• mechanical retention.

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• Secondly to achieve a strong bond through the
  reaction of co-polymerization (hybrid layer) with
  the hydrophobic matrix of composites or luting
  resins. This process can be performed clinically
  in different ways according to the presentation
  of the adhesive system. Enamel adhesion through
  the acid-etching has been shown to be effective
  whereas the development of dentine adhesion
  techniques is in constant progress.

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• The generation of adhesive systems developed in
  the early 1990s according to the total-etch
  concept are applied using a multi-step procedure.
  More recently further types of adhesive systems
  have been developed in order to simplify and
  reduce the stages of application (etch and rinse
  adhesive in two steps or self-etching systems in
  either two or one steps, according to the
  classification of Van Meerbeek et al. 2003).
  However, the three-step system (etchingprimeradh
  esive resin) still seems to provide the most
  reliable bonding.

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Enamel and dentine adhesion

• The acid-etching of a tooth surface allows for
  the micro-mechanical adhesion of resin to the
  tooth.
• Etching with acid remove a portion of the
  superficial mineral component of enamel and
  dentine.
• Micro porosities or open dentinal tubules
  produced in which resin will penetrate and
  mechanically grip the tooth providing retention
  for an overlying restoration.

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Advantages of adhesive dentistry

1. Less tooth structure removed
2. Reduce microleakage at margins
3. Better distribution of stresses
4. Possible reinforcement of tooth structure
5. Easy to repair filling with minimal tooth
   preparation
6. Tooth colored restorative materials like veneers
   may be added without preparation.

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Enamel and dentine adhesion

• Tooth strength after restorationamalgam vs
  composite?
• Strength of uncut tooth 100
• MOD amalgam prep 50
• MOD prep varnish amalgam 50
• MOD prep composite resin 88

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Indications of adhesive dentistry

• Restoration of carious teeth
• Abraded and eroded surfaces
• Veneers
• Re-contouring.e.g diastemas
• Preventative sealants
• Bonding orthodontic brackets
• To treat dentinal hypersensitivity

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Requirement for good adhesion/bonding

• Materials must be in contact.
• Wetting of the tooth surface must occur.
• Enamel is high surface-free energy.
• Dentine is low surface-free energy.
• Tooth surface must be clean to provide high
  surface-free energy.

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Factors affecting adhesion to tooth structure

1. Physical and chemical properties of adhesive
   resin.
2. Surface contamination (saliva, blood).
3. External stresses.
4. The way loads are applied to the bond joint.
5. Degree of resin cure.

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• BECAUSE the composition of enamel and dentine are
  different (organic, inorganic, water), adhesion
  to the two tooth tissues is also different.
• Problems with bonding to dentine!
• High organic content
• Smear layer
• Variability of dentine
• Vitality of the pulp

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Acids used to prepare tooth surfaces

• Citric acid
• Nitric
• Oxalic
• Polyacrylic acid (10)
• Phosphoric acid (10-37) most common

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Micromechanical Bonding Technique
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Enamel adhesion
The prismatic structure of enamel
Micro-mechanical interlocking only
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Etched enamel
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Micro-mechanical interlocking only
SEM micrograph of the enamel surface after
etching for 40 seconds with 35 phosphoric acid
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White frosted appearance
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Dentine smear layer
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Smear layer

• Is present on the surface of freshly cut dentine.
  Its loosely bonded layer of cutting debris
  including dentine chips, micro-organisms,
  salivary proteins and collagen from dentine.
• The smear layer is formed by process of cavity
  preparation and extended over the whole prepared
  surface of dentine and into dentinal tubules
  (smear plug).

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Primer (hydrophilic monomer HEMA) and adhesive
resin BisGMA
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Hybrid layer
Resin tag
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SEM of dentine surface after primer (conditioner)
application
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The interface of a resin-enamel bond.resin tags
25 micron
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Failure or debonding surface
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Testing of bond strength mpa
Micro-tensile bond strength
Shear bond strength
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Background

• Resin composites are the most common dental
  restorative materials used in developed
  countries.

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Sales of amalgam and composites in Germany
Scientific Documentation Tetric EvoCeram
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Use of dental amalgam and composite as posterior
restoration
IADR 2006 Dublin, Hickel R (Munich University)
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From Amalgam to Composite in Finland
Acta Odontol Scand 2004 62 82-6.
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The median ages of failed restorations
Acta Odontol Scand 2004 62 82-6.
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The longevity of composite resin restorations

• Failures
• secondary caries
• Bulk fracture of the restoration
• wear

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Thank you