Dentin boning agents /certified fixed orthodontic courses by Indian dental academy

DENTIN BONDING AGENTS

INDIAN DENTAL ACADEMY
Leader in Continuing Dental Education

www.indiandentalacademy.com

 ADHESION- The mechanism that bonds two materials in intimate contact
across an interface - Davidson (1996).

 Types of adhesion

 1. Physical Bonding
 2. Chemical Bonding
 3. Mechanical Bonding

 1. PHYSICAL BONDING
Physical bonding involves Vander walls forces or other electrostatic
interactions that are relatively weak. It may be the only type of bonding if
surfaces are smooth and chemically dissimilar.
 2. CHEMICAL BONDING
Chemical bonding involves bonds between atoms formed across the interface
from the adhesive to the adherend. Because the materials are often
dissimilar, the extent to which this bonding is possible is limited and the
overall contribution to bond strength is normally quite low.

 3. MECHANICAL BONDING
Mechanical bonding is the result of an interface that involves undercuts and
other irregularities that produce interlocking of the materials.

 CHEMICAL ADHESION
 Primary atomic bonds may be of three different
types: 1) Ionic, 2) Covalent, and 3) Metallic.

Ionic Bonds
 These primary bonds are of simple chemical type, resulting from
the mutual attraction of positive and negative charges. The
classic example being sodium chloride (Na+Cl-). Because the
sodium atom contains one valance electron in its outer shell
and the chlorine atom has 7 electrons in its outer shell, the
transfer of the sodium valance electron to the chlorine atom
results in the stable compound Νa+Cl−.
 Covalent Bonds
 In many chemical compounds, adjacent atoms share two
valance electrons. The hydrogen molecule, H 2 is an example of
covalent bonding. The single valence electron in each hydrogen
atom is shared with the other combining atom, and the valence
shells become stable.

 Metallic Bonds
 Certain atoms of a few crystals like gold can easily donate
electrons from their shell and form a gas of free electrons. The
contribution of free electrons to this could results in the
formation www.indiandentalacademy.com
of positive ions that can be neutralized by acquiring
new valence electrons from adjacent atoms.

 Inter atomic Secondary Bonds
 In contrast with primary bonds, secondary bonds do not
share electrons. Instead, variation among molecules or atomic
groups induces polar forces that attract these molecules.
 a. Hydrogen Bonding
 In water molecule one oxygen atom is attached to two hydrogen
atoms. These bonds are covalent because the oxygen and
hydrogen atom share their electrons. As a consequence,
electrons do not shield the protons of the hydrogen atoms
pointing away from the oxygen atom efficiently. Thus the proton
side of the water molecule becomes positively charged. On the
opposite side of the water molecule, the electrons that fill the
outer orbit of the oxygen provide a negative charge. When water
molecule mingles with other molecules the hydrogen portion of
one molecule is attracted to the oxygen portion of its
neighboring molecule, and hydrogen bridges are formed.

 Vander Walls Forces
 Normally the electrons of the atoms are distributed equally
around the nucleus and produce an electrostatic field around
the atom. However this field may fluctuate so that its charge
becomes momentarily positive and negative. A fluctuating dipole
is thus created that will attract other similar dipoles. Such inter
atomic forces are quite weak.


ENAMEL ADHESION

 Buonocore- first proposed chemically treating enamel with acid solutions in
1955. -H3PO4 creates micro-porosities in the enamel surface and enables
bonding of resin to this surface via micro mechanical retention.

 Application time- 15 seconds

 The first bonding agents marketed for this technique were unfilled
BISPHENOL A GLYCIDYL DIMETHACRYLATE (BIS GMA) resins.

 Enamel etching results in three different micro morphologic patterns.

 Type 1: The most common type involves preferential removal of the enamel
prism cores, the prism peripheries remaining intact.
 Type 2: Etching pattern is the opposite of type 1 involving preferential
removal of the peripheries with the cores being left intact.
 Type 3: Etching pattern contains areas, which resembles both type 1 and type
2 along with some distinct areas where the pattern of etching appears to be
unrelated to the enamel prism morphology.

 Gwinnett and Buonocore -use of lower acid
concentrations to prevent the formation of precipitates
that could interfere with adhesion.
 Application of 50% phosphoric acid for 60 seconds
-monocalcium phosphate monohydrate precipitate that
can be rinsed off.
 concentrations below 27% may create a dicalcium
phosphate monohydrate precipitate that cannot be easily
removed and, consequently, may interface with adhesion.
 Other acids -maleic acid, citric acid, nitric acid and
oxalic acid


HYBRID LAYER
 HYBRID LAYER: (“adhesion interface”,
“resin-dentin inter-diffusion zone”, inter
penetration zone). is a “transitional zone of
resin reinforced dentin sandwiched
between cured resin and the unaltered
dentinal substrate” (Nakabayashi 1982).

 essential mechanism of adhesion -micro-
mechanical & generated by monomer
impregnation of the exposed collagen of
demineralized superficial dentin.


REQUIREMENTS OF A DENTIN BONDING AGENT

Bond strength:
Biocompatibility of the material:
Long-term durability of the bond:.
Polymerization’s shrinkage:


 Adhesive forces operating across an interface depends on several
factors.

Clinical factors affecting adhesion
Factors affecting adhesion to mineralized tissue

. Clinical Factors Affecting Adhesion

Salivary and or blood contamination

Moisture Contamination From Hand-piece.

Oil contamination of hand piece of Air Syringe

Surface roughness of tooth surfaces

Mechanical undercuts in tooth preparations

Fluoride contents of teeth


 Presence of plaque, calculus, extrinsic stains / debris

 Presence of bases or liners on prepared teeth

 Tooth dehydration.

 Constituents of temporary cements


FACTORS AFFECTING ADHESION TO MINERALIZED
 I. Factors related to theTISSUES
adherent
 1. Physicochemical properties of dentin that complicate dentin
adhesion
 2. The dentin smear layer and dentin permeability.
 3. Transformed dentin surface structure due to physiological
and pathological processes.

 II. Factors Related to The Restorative Resins
 i. Physical properties of adhesives.
 ii. Polymerization contraction of restorative resins.
 iii. Young’s modulus of elasticity.
 iv. Initial polymerization site
 v. The relaxation of contraction stress by hygroscopic
 expansion.
 vi. Thermal expansion coefficient and thermal
conductivity.
 vii. Transmission of stress across the composite dentin
interface.

CLASSIFICATION ACCORDING TO GENERATIONS
 FIRST GENERATION DENTIN BONDING AGENTS

 -Buonocore 1956
 a glycerophosphoric acid dimethacrylate – containing resin would
bond to acid etched dentin.
 bond -due to the interaction of this bifunctional resin molecule
with the calcium ions of hydroxyapatitie, but immersion in water
would greatly reduce this bond. Nine years later Bowen tried
using N-Phenyl glycine and glycidyl methacrylate (NPG-GMA),
which is a bifunctional molecule or coupling agent. This molecule
had one end bonding to the dentin while the other bonds to the
composite resin. The bond strengths of these system was however
1-3 Mpa. The NPG-GMA also bonded to the dentin by chelation
with calcium on the tooth surface.


Materials
1.Glycerophosphoricacid dimethacrylate.
 2. Cyanocrylate
 3. N-Phenyl Glycine – Glycidyl Methacrylate Eg., CERVIDENT

 No commercial products are available from this generation. Intraoral hydrolysis
of GPDM, polymerization problems of Cyanocrylate and instability of NPG-
GMA precluded their use.

 DISADVANTAGES:
 1. Poor bond to dentin familiar amalgam type retentive cavities
 2. Used only for small class III and class V restorations where there was
adequate enamel to which to bond.
 3. Postoperative sensitivity in attempted posterior occlusal restorations.


SECOND GENERATION DENTIN BONDING AGENTS

 1970- halo phosphorous esters of unfilled resins
 bisphenol-A glycidyl methacrylate (Bis-GMA),
 hydroxyethyl methacrylate (HEMA).
 bonded to dentin by an ionic bond to calcium by chloro
phosphate groups.

 These were weak bonds but were an improvement over the first
generation systems.



 MATERIALS
 a. Clearfil – A reaction product of 2 – HEMA and a phenyl
phosphate ester. (Phenyl – p) was utilized. 1 – 3 Mpa.
 b. Scotch Bond – Halo phosphorous ester of BIS – GMA. 1 –3
Mpa.
 c. Prisma Universal Bond – 6.5 to 7.0 Mpa.
 d,. Dentin Adhesit – An adhesive system that utilizes a isocyanate onomer
and 5% NaOcl as a conditioner – solubilize the dentin collagen.

 DISADVANTAGES
 1. Weak bond to dentin
 2. Mechanical retention form was still necessary since bond strength alone
was inadequate.
 3. Margins on dentin were problematic since the low dentinal bond
strengths permitted extensive marginal microleakage.
 4.Restoration failure occurred most commonly due to hydrolytic
decomposition.


THIRD GENERATION DENTIN BONDING AGENTS
 Acid etching of the dentin partially removes or modifies the smear layer

 Acid opens the dentin tubules partially and increases their permeability

 acid must be rinsed completely before application of the primer.
 The primer -hydrophilic resin monomers like hydroxyethyl trimellitate anhydride
and bisphenol dimethacrylate (BDPM).

 The primers contain a hydrophilic group that infiltrates the dentin and the
hydrophobic group that adheres to the resin.

 The dentin primers usually used in these third generation systems may be 6%
phosphate penta-acrylate (PENTA); 30 percent HEMA and 64% ethanol. After the
application of the primer the unfilled resin adhesive is applied.

 In most of these systems, the phosphate primer modifies the smear layer by
softening it after penetration and it cures forming a hard surface. The adhesive is
then applied attaching the cured primer to the composite resin. However bonding
was not very successful because the resins did not penetrate the smear layer and
the smear layer was very weak.

- XR bonding system
 - Gluma bonding system
 - Tenure dentin bonding system
 - 4 META
 - Phenyl-P
 - Mirage bond
 Super bond


FOURTH GENERATION DENTIN BONDING AGENTS
 complete removal of the smear layer


FIFTH GENERATION DENTIN BONDING AGENTS
 reducing the bonding steps

 The fifth generation consists of two different types of adhesive
materials.
 - The so called “one bottle system”.
 - Self etching primer bonding systems.
 Indications:
 • Direct composite restoration.
 • Indirect bonding.
 • Root desensitization



 Chemistry:
 • HEMA, BisGMA, dimethacrylates, and patented polyalkenoic
acid copolymer.
 • Technique:
 • Etch enamel and dentin for 15 seconds.
 • Using a fully saturated brush tip, apply 2 consecutive coats of
Single Bond.
 • Dry for 2-5 seconds.
 Light-Cure for 10 seconds
 Water and ethanol


SIXTH GENERATION DENTIN BONDING
AGENTS
 proper bond to enamel and dentin
used only one solution.
 1. Compartment 1 : Containing
methacrylate phosphoric acid esters,
photo initiators and stabilizers.
 2. Compartment 2 : contains water,
complex fluoride and stabilizers.
 3. Compartment 3 has a micro
brush.


CLASSIFICATIONS OF
MODERN ADHESIVES

 Classified based on number of clinical application steps and
interaction with tooth substrate.

1. Total etch adhesives
 [E + P,A] a) Two step etch adhesives
 [E + P + A] b) Three step etch adhesives
2. Self etch adhesives
 [E + P, A] a) Two step self etch
adhesives
 [E + P + A] = [C,P,A] b) One Step self etch adhesives



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Dentin boning agents /certified fixed orthodontic courses by Indian dental academy

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