1provided by:A.radanipour & E.ahmadi. What is adhesion? The force that binds two dissimilar materials together when they are brought into intimate contact

Etching in dentistry

1provided by:A.radanipour & E.ahmadi

What is adhesion?

The force that binds two dissimilar materials together when they are brought into intimate contact

In dentistry, bonding refers to the process of attaching a restorative material to tooth structure by adhesion


Basic principles in the bonding process

Surface preparation to remove plaque & debris

Acid etching with phosphoric acid, to remove mineral, create porosity, wettability

Bonding agent applied and flows to fill the porosities and create resin tags (micromechanical retention)

Resin applied and bonds chemically to underlying bonding agent (primary bonding)


Adhesion For proper adhesion to occur, intimate

contact between the adhesive and the substrate is needed. This intimate contact is affected by:

Wettability of the substrate surfaceThe viscosity of adhesiveThe morphology or surface roughness,



Etching

Preparation of TOOTH surfaces and DENTAL MATERIALS with etching agents, usually phosphoric acid, to roughen the surface to increase adhesion or osteointegration.

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Enamel etching Introduced by Michael Buonocore in 1950sEtching time: 10-30 seconds (around 15

seconds)Primary teeth and fluoride treated teeth

require more timeEtched enamel looks frosty white when driedEtching produces a rough surface (pits) into

which resin flows and forms resin tags = micromechanical retention


Enamel etchingResin tags may penetrate to a depth of 10-20

microns in etched enamelThe depth of penetration depends on:

Etching timeRinsing time

These two actors determine how effective etching was, and how well debris were removed from enamel surface


Enamel etchingLiquid or gel (the

gel is made by adding colloidal silica to the acid) phosphoric acid 30-50% (usually 37%).


Procedure Acid etch is applied, how ?Etchant is applied for 15 seconds, or longer

as mentioned previouslyRinsing for 20 seconds then drying.

Appearance of enamel?Enamel should be kept clean and

contaminant free (saliva, blood, etc)If contamination occurs? Re-etch.


Enamel bondingIn the past, etching and bonding involved

only enamel. Currently, total etch technique is done, and bonding agents are applied to both enamel and dentine.

Bonding agents used for enamel bonding were made from resin combined with diluents to lower viscosity. (Bis-GMA + TEGDMA)


Dentine etching and bondingWhat makes dentine a challenge when it

comes to adhesive bonding:Dentine is a living tissue (50% HA, 30%

collagen, 20% fluid)Tubular nature of dentine (dentinal fluid)Branching patterns in tubules, may enhance

retentionPossible side effects on the pulp


Dentine etching 1979 etching was done for dentine as well as

enamel using 37% phosphoric acid. Research proved enhanced bonding

Over etching, effects on dentine structure and pulp?

Over etching dentine leads to weaker bond and sensitivity

Over drying should be avoided to prevent collapse of collagen and occluding tubules





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1provided by:A.radanipour & E.ahmadi. What is adhesion? The force that binds two dissimilar materials together when they are brought into intimate contact