The document discusses the acid etching process used for bonding resin-based materials to tooth enamel, highlighting its role in creating micro-mechanical adhesion. Key factors for successful bonding include etching time, washing, and drying stages, while the presence of the smear layer on freshly cut dentine affects bonding efficacy. Dentine conditioning with acid helps remove the smear layer and facilitate the formation of a hybrid layer critical for effective bonding.

1. Bonding Of Resin Based
Materials

2. Acid etch systems for bonding to enamel
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.

12. Micromechanical Bonding
Technique

13. Etched enamel

14. Etched enamel (white frosted appearance)

15. Major factors for success or failure of acid etch
bonding systems.
• 1. Etching time
• 2.Washing stage
• 3. Drying stage

19. Dentin smear layer

20. 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. 3 - 15µm thick.
• 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).

21. Dentine conditioning
• Conditioners (37% phosphoric acid)
• Dissolve not only smear layer and smear plug but also decalcify inter-tubular
dentine to a depth of few microns.
• A three dimensional collagenous network formed which is infiltrated by
primer and resin to form resin infiltrated/reinforced layer or hybrid layer

22. PRIMING
• Done to overcome the normal repulsion between the hydrophilic dentine
and hydrophobic resin.
• Most commonly used primer is HEMA (hydroxylethylmethacrylate)
• Hydroxyl group of HEMA being hydrophyllic in nature is responsible for its
effective priming nature

23. DENTINE BONDING AGENT
• Fluid resin able to flow over and wet the primed surface to complete the
formation of an effective bond.
• Light cured, chemically cured or dual cured

30. Hybrid layer
Resin tag