This document discusses the history and development of dentin bonding agents across 7 generations from the 1950s to 2000s. It describes the ideal requirements for bonding agents and challenges bonding to dentin like the smear layer. The roles of conditioners, primers, and adhesives are explained. Critical factors for bonding like moisture control and the hybrid layer formation are also summarized.

2.  DEFINITION
 IDEAL REQUIREMENTS
 PROBLEMS IN BONDING OF DENTIN
 CHRONOLOGY OF DEVOLPMENT
 BONDING TO DENTIN
 ROLE OF SMEAR LAYER IN DENTIN BONNDING
 CONDITIONING OF DENTIN
 DENTIN BONDING AGENTS AND GENERATIONS
 COMPONENTS OF BONDING AGENTS
 INDICATIONS FOR CLINICAL EXAMINATION
 CRITICAL STEPS IN BONDING

4.  Biocompatible
 Non toxic, Non irritant, Non poisonous
 Low film thickness, Low viscosity
 Form strong permanent bond
 Good dimensional stability
 Similar C.O.T.E as tooth
 Low thermal conductivity
 Good shelf life
 Prevent micro leakage

5. GENERATION
GENERATION TIME
PERIOD
DEVELOPMENT
1950-1970 Experimentation with mineral acids for bonding acrylic to
enamel, concern about etching of dentin, bonding agents
not utilized with composites.
Early 1970s
Late 1970s
Acid etching of enamel, enamel bonding agents
Hydrophobic enamel bonding agents, hydrophilic dentin
bonding agents, light cured components.
4 Mid to late
1980s
Removal of dentin smear layer, acidic monomers and
acidic pretreatments,, reduction of steps in bonding
technique, multiuse bonding agents.
5 Early 1990s Etching to achieve hybrid layer in dentin, hydrophilic
agents for both enamel and dentin, bonding to moist
tooth structure, single bottle primer adhesives.
6 Mid to late
1990s
Self etching primers and primer adhesives, light and dual
cured options
7 Early 2000s No mix, self etching adhesives.

6.  ETCHENTS / CONDITIONERS
 PRIMERS
 ADHESIVES

7.  ORGANIC ACID:- Maleic acid ,EDTA ,citric acid,
tartaric acid.
 POLYMERIC ACID:- poly acrylic acid
 INORGANIC ACID:- phosphoric acid, nitric acid.

8.  NTG-GMA
 PMDM
 BPDM
 PENTA
 HEMA

9.  Hydrophobic monomers
 BIS-GMA
 UDMA
 Diluent
 TEGDMA
 Wetting agent
 HEMA

10.  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 a considerable amount of organic
material and water
 Dentin is close to pulp, so different chemical
used for bonding and etching may irritate the
pulp.

11.  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.

12.  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

13.  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

14.  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

15.  Conditioning of dentin 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
 1.Acid conditioners ;-several acids like
phosphoric acid, maleic acid citric acid ,nitric
acid, oxalic acid and hydrochloric acid

16.  2.chelators- remove the smear layer without
decalcification or significant physical changes
on underlying dentin substrate
 Chelates refers to a compound with a central
metal ion surrounded by covalently bonded
atoms ,legands which posses additional bonds
for chemical reaction
 Best known chelator conditioner is EDTA
 3.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

17.  Water act as a plasticizer for collagen and keep
it in soft state
 If dentin is excessively dried it will leads to
collapse of dentin
 If critical water concentration exists, that
prevents collapse of collagen network and
allows expansion of dried dentin.
 Critical amount of water is essential for
bonding but an over wet condition decreases
bond strength and formation of blister like
structures at the interface

18.  This is the zone where the adhesive resin of the
dentin bonding agent micromechanically
interlocks within the inter tubular dentin and
surrounding collagen fibers
 Hybrid layer is formed in following manner:-
 1.etching removes smear layer and exposes
collagen fibers
 It also removes hydroxy apetite with in the
intertubular dentin

19.  2. Primers penetrate the collagen network.
 3.Adhesive resins along with the primers form
resin microtags within the intertubular dentin
 Hybrid layer also called resin-dentin
interpenetration/ interdiffusion zone

20.  Development of NPG-GMA, a surface active co-monomer was
the basis of first commercially available dentin bonding agent.
 Theoretically NPG-GMA was supposed to chelate with calcium
in dentin to form water resistant chemical bond to dentin
 In this M -un saturated methyl methacrylate group
 X -acidic phosphate group to react with calcium of dentin
 But bond strength produced by this agent very low (2-3 mpa).
 Clinically this agent did not successfully bond composite resin
to dentin.

21.  Introduced in 1970s and attempted to bond chemically
to either inorganic or organic components of dentin
 But they produced only limited bond strength (5-6 mpa).
 Materials tried were:- halogen phosphoric acid esters of
Bis-GMA, NPG-GMA, PHENYL-P
 Examples:-
 Clear fill bonds system F
 scotch bond
 bond lite.

22.  Third generation attempted to deal with smear
layer and dentinal fluid
 They employed two approaches:-
 Modification of smear layer to improve its property
Or
 Removal of smear layer without disturbing smear
plugs that occlude the dentinal tubules.
 The idea was to avoid aggressive etching of dentin
because it cause pulpitis

23.  2% nitric acid
 2.5% maleic acid with HEMA
 10% citric acid with 3% ferric chloride
 10% phosphoric acid
 Eg:- Tenure, Scotch bond, Gluma C&B metabond

24.  Developed in 1990s
 Multiple bottles
 Etching with phosphoric acid required
 Rinsing required
 Light and dual cured formulations available.
 ETCHANT:- Phosphoric acid, citric acid/ calcium chloride,
oxalic acid/ aluminum nitrate.
 PRIMER:- NTG-GMA/BPDM,HEMA/GPDM,4META
 ADHESIVES:- Bis-GMA,TEGMA
 SOLVENT:- acetone, ethanol/water.
 Eg:- all bond 2 ,panavia 21.

25.  This are simplified version of fourth generation
 In fifth generation bonding agents primer and
adhesives are in same bottle.
 Etching and rinsing required
 ETCHANT:- Phosphoric acid,
 PRIMER:- PENTA, Methacrylated phosphonates
 SOLVENT:- acetone, ethanol/water.
 These agents are inferior to fourth generation
bonding agents in terms of bond strength.
 Eg:- single bond3,Gluma comfort bond.

26.  These includes self etching primers where the etchant
and primer are in one bottle and adhesive resin in
another bottle.
 Manipulation is easy , show good bond strength to
dentin but not to enamel
 Etching and rinsing not required
 Primer applied first then adhesive.
 ACIDIC PRIMER ADHESIVE:- Methacrylated phosphates
 SOLVENT:- Water
 Eg:- clear fill SE bond,XENO

27.  One bottle- no mixing required.
 Etching and rinsing not required
 Light cured formulation
 Useful for direct applications with light cured
restorative material.
 ACIDIC PRIMER ADHESIVE:- Methacrylated
phosphates
 SOLVENT:- Water

28.  All direct composite resin restoration,both
anterior& posterior
 For bonding indirect composite resin inlays, onlays
and veneers.
 For bonding indirect ceramic veneers , inlays and
onlays.
 Bonded amalgam restorations
 Management of dentin hypersensitivity
 Luting post and core restorations

29.  Proper isolation:- by using rubberdam , saliva
contamination can block mechanical bonding.
 Pulp protection:- by using calcium hydroxide liner.
 Acid etching of enamel and dentin:- by using 37%
phosphoric acid for 15 sec. then wash
 Dentin surface must be kept moist. If dentin is
over dried it would result in collapse of exposed
collagen fibers.
 Careful application and curing of bonding agents.
 Placing the composite resin.

30. CLINICAL OPERATIVE DENTISTRY- PRINCIPLES
AND PRACTICE – RAMYA RAGHU
CRAIG’S RESTORATIVE DENTAL MATERIALS
OPERATIVE DENTISTRY – VIMAL.K.SIKRI
SCIENCE OF DENTAL MATERIALS – V .SHAMA
BHUTT