1. Adhesive technique I. Dentin adhesion Generations of adhesives

2. ADHESION
Def.: state, where two surfaces are held together by interfacial forces
Dentistry: anorganic tooth material replaced by bonding agent (resin)
Demineralization: removal of calcium-phosphates
Hibridization: infiltration of bonding agent
Basically 2 types:
1. micromechanical irregularities in the surface – anorganic tooth material changes place with bond (resin)
2. chemical
Range of indication: esthetic front tooth restorations, direct and indirect fillings:
ceramic veneers,
all- porcelain adhesive bridges and crowns,
preprothetical restorations,
orthodontic adhesives

3. ADHESIVE DENTISTRY
In operative dentistry this technique is commonly used in resin- based material restorations.
Filling materials used in adhesive dentistry:
composites,
glass- ionomers,
compomers,

4. PHYSICAL BACKGROUND OF ADHESIVE TECHNIQUES
The surface phenomena influence the employement and the adhesion of the adhesive filling materials.
Surface phenomena include:
Surface energy
Wetting
Capillary action
Adhesion

5. SURFACE ENERGY- SURFACE TENSION I.
Atoms and molecules at the surfaces of liquids and solids posses more energy than those in the interior.
Reason: assymmetrical forces. Molecules on the border surface of e.g. air-liquid are in contact with each other and the air molecules. However, in liquid, molecules in the inner parts are only in contact with each other which means a different energetic state.
In case of liquids this causes the formation of drops, because liquids tend to form in smallest surfaces ->surface tension.

6. SURFACE ENERGY- SURFACE TENSION II.
In general: 1. the higher the surface energy, the higher the bonding strength and 2. smaller the extension and penetration.
Importance: adhesive penetration to the etched tooth surface.

7. WETTING
Wetting is defined in terms of the degree of a spreading liquid drop on a solid surface.
0° degree contact angle indicates complete wetting.
above 90 degrees indicate poor wetting.
Good wetting promotes capillary penetration and adhesion.
This is important in the employment of adhesives.

8. CAPILLARY PENETRATION
The surface energy of a liquid creates pressure that drives the liquid into tubules.
A liquid with
low viscosity,
low surface energy and
low contact angle ( good wetting ) will penetrate faster than one with opposite combination of properties.

9. ADHESION
Adhesion is the attachement of materials in contact that resist the forces of separation.
Types of adhesion:
MECHANICAL: depends on mechanical interlocking of the two phases and may include microscopic attachements as in case of resin bonding to etched enamel (bonding agent- enamel)
CHEMICAL: relies on chemical bonding between two phases.

10. ADHESIVES
Bonding systems involve an unfilled or lightly filled, liquid acrylic monomer mixture placed onto an acid etched tooth surface.
Types: enamel, dentin ( or both ) bonding systems.
Employment depends on the type of the system.

11. Ideal adhesive Biocompatible, non-toxic, non-allergic
Proper sealing between interfaces, prevents microleakage
Good dimension stability
Consist of:
Etching material
Primer
Bonding agent

12. Conditioning on dentin surface
Aim: removal of smear layer and demineralization of dentin surface
Conditioning dentin surface with acids or chelating agents (EDTA)
Acids: phosphoric, polyacrylic, EDTA, maleinic etc. In different concentrations
Demineralization of intra- and intertubular dentin > collagen fibers exposition
Acid contrentration, etching time! > postoperative sensitivity

13. Adhesive technique on dentin - Primer
HEMA (hidroxietil methacrylate)+acetone/etanol/water
Primer: opens gaps that appear after acidic etching, rinsing and drying of dentin surface – collagen fiber collapse
Bifuncional monomer: bonding of the hidrophil group of HEMA to hidrophil dentin, and hidrophob methacrylate group of HEMA to hidrophob bonding agent
Hybrid layer: bonding agent+primer+collagen fibers

14. Adhesive technique on dentin – Bonding agent
Bonding agent, adhesive resin: consists of hydrophob monomers, such as:
Bis-GMA (bisphenol-A-glycidyl methacrylate)
UDMA (urethane-dimethacrylate): high viscosity, to decrease > difunctional monomer>
TEG-DMA (trietilén-glikol-dimetakrilát)
HEMA

15. Optimal bonding
Adhesive should cover the dentin surface evenly, in a thin layer >intertubular area
Intratubular area: resin tags
Near the pulp the density of dentinal tubules increases
Superficial dentin - the main bonding force is due to the penetration into intertubular dentin
Deeper cavities: intratubular penetration and bonding

16. Evolution of dentin adhesives no-etch-total-etch-self-etch
1st generation:
-1956 BUONOCORE: glicerophosphoric acid dimethacrylate bonds to dentin
-Bowen: surface active co-monomer: NPG-GMA (N-fenilglicin-glicidil-metakrilát)
-theoratically able to form chemical bonds with Ca ions of dentin
2-3 Mpa bond strength
 poor clinical results

17. 2nd generation dentin adhesives
Phosphate esters of BIS GMA, HEMA
mechanism based on polar interaction between phosphate groups in resin(Bis-GMA or HEMA) (negative) and Ca++ in smear layer
5-6 Mpa
 smear layer loosely attached

18. 3rd generation dentin adhesives
Late 80’s: Modification or removal of smear layer – open dentintubules
3-8MPa
Adhesive: un/partially filled resin
Conditioning+primer(HEMA)

19. 4th generation dentin adhesives
Total-etch technique/etch and rinse,early 90’s
Acid application on dentin surface
According to instructions
Applying bonding agent on dentin and enamel
Etching, rinse, dry with light air
Wet-bonding – aceton based primer
20-30MPa

20. 5th generation dentin adhesives
Make the procedure more simple
Etching, bonding
Primer+bond in one step – applying the adhesive agent in one or two layers

21. 6th generation dentin adhesives Self-etch adhesives
Self-etch primer (etch+primer in one bottle) + bonding agent
Contains carboxylate / phosphoric group monomers
Dentin adhesion is good, enamel inferior
No need for seperate etching and bonding
Self-etch adhesive: etch, primer, adhesive (bonding agent) in one
Need mixing

22. Resin modified glass ionomer adhesives
Glass ionomer is the only material that can bond to tooth structure without any pretreatment of the surface
Condiotioning with polyalken acid improves bonding forces significantly

23. Thank you for your attention!