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

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

GENERATIOGENERATIONN

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.

ETCHENTS / CONDITIONERS

PRIMERS

ADHESIVES

ORGANIC ACID:- Maleic acid ,EDTA ,citric acid, tartaric acid.

POLYMERIC ACID:- poly acrylic acid

INORGANIC ACID:- phosphoric acid, nitric acid.

NTG-GMA

PMDM

BPDM

PENTA

HEMA

Hydrophobic monomers BIS-GMA UDMA

Diluent TEGDMA

Wetting agent HEMA

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.

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.

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

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

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

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

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

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

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

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

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.

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.

Third generation attempted to deal with smear layer and dentinal fluid

They employed two approaches:- Modification of smear layer to improve its

propertyOr 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

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

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.

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.

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

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

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

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.

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