Transcript 4th- Bonding of resin-based materials

Bonding of resin-based materials
Libyan International Medical University
• 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.
• 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.
• 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
(etching+primer+adhesive resin) still seems to
provide the most reliable bonding.
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.
Advantages of adhesive dentistry
1.
2.
3.
4.
5.
Less tooth structure removed
Reduce microleakage at margins
Better distribution of stresses
Possible reinforcement of tooth structure
Easy to repair filling with minimal tooth
preparation
6. Tooth colored restorative materials like
veneers may be added without preparation.
Enamel and dentine adhesion
• Tooth strength after restoration…amalgam vs
composite?
• Strength of uncut tooth = 100%
• MOD amalgam prep = 50%
• MOD prep + varnish + amalgam = 50%
• MOD prep + composite resin = 88%
Indications of adhesive dentistry
1.
2.
3.
4.
5.
6.
7.
Restoration of carious teeth
Abraded and eroded surfaces
Veneers
Re-contouring….e.g diastemas
Preventative sealants
Bonding orthodontic brackets
To treat dentinal hypersensitivity
Requirement for good adhesion/bonding
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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.
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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1.
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4.
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
Acids used to prepare tooth surfaces
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Citric acid
Nitric
Oxalic
Polyacrylic acid (10%)
Phosphoric acid (10-37%) most common
Micromechanical
Bonding
Technique
Enamel adhesion
The prismatic structure of enamel
Micro-mechanical interlocking only
Etched enamel
Micro-mechanical interlocking only
SEM micrograph of the enamel surface after etching for 40
seconds with 35% phosphoric acid
White frosted appearance
Dentine smear layer
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).
Primer (hydrophilic monomer HEMA) and
adhesive resin BisGMA
Hybrid layer
Resin tag
SEM of dentine surface after primer
(conditioner) application
The interface of a resin-enamel
bond….resin tags 25 micron
Failure or debonding surface
Testing of bond strength mpa
Micro-tensile bond strength
Shear bond strength
Background
 Resin composites are the most
common dental restorative materials
used in developed countries.
Sales of amalgam and composites in Germany
Amalgam
Composite
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Scientific Documentation Tetric EvoCeram®
03
20
02
20
01
20
00
20
99
19
98
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97
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96
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95
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94
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39
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92
0
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Sales (relative proportion)
3
Use of dental amalgam and composite as
posterior restoration
120
Amalgam
100
Composite
%
80
60
40
20
0
Sw e 1985 Sw e 2001 Ger 1985
Ger 1995 USA 1988 USA 1997
IADR 2006 Dublin, Hickel R (Munich University)
From Amalgam to Composite in Finland
659 dentists
80
%
60
40
20
0
Composite
Amalgam
6.322 restorations (97-01)
Acta Odontol Scand 2004; 62: 82-6.
GIC
The median ages of failed restorations
14
12
Years
10
8
6
4
2
0
Composite
Amalgam
Acta Odontol Scand 2004; 62: 82-6.
GIC
The longevity of composite resin
restorations
dentist
Failures:

secondary caries
Bulk fracture of the
restoration

wear

patient
material
Thank you