rabin dry bonding and wet bonding 1.pptx

Dentistry , Endodontics

1. DRY BONDING vs WET BONDING Presented by Rabin Panthee

2. CONTENTS Adhesion and mechanism of adhesion Factor affecting adhesion Enamel vs Dentin in Structure and composition and bonding Problems during dentin bonding Dry vs wet dentin Role of water in Bonding

3. ADHESION/BONDING Is the force or intermolecular attraction that exists between molecules of 2 unlike substances when placed in intimate contact with each other.

4. ADHESIVE Is the substance that promote adhesion of one substance or material to one another. ADHEREND Is a material substrate that is bonded to another material by means of adhesive.

5. MECHANISM OF ADHESION

6. Mecanism of Adhesion MICRO-MECHANICAL ADHESION: -Here bonding occurs because of penetration of one materails into another at microscopic level. eg : Penetration of resin and formation of resin tag with tooth structure. ADSORPTION: -Chemical bonding to inorganic component (hydroxyapatite) or organic compound (mainly Type I collagen) of tooth structure.

7. Force involved may be : Primary: Ionic and covalent Secondary: Hydrogen Bond or Vanderwall force. DIFFUSION : Occurs as inter diffusion of adhesive and adherends at the interface, results in dissaperance of interface. -only possible when adhesive and adherends are polymers and polymers must be compatible and mobile.

8. COMBINATION ADHESION: -A substance can be bonded by combination of any one of above means.

9. FACTOR AFFECTING ADHESION Wettablity Contact Angle

10. Surface Energy

11. Surface contamination Water

12. FACTOR AFFECTING ADHESION/BONDING 1.Wettablity -is the relative affinity of a liquid for the surface of solid. -the ease with which liquid will flow onto the surface the more will be wettability.

13. Depends on : Surface energy: Increase surface energy, better wettability , decrease contact angle , better adhesion . Cleanliness of the adherend : Cleaner the surface greater the adhesion 2. Contact Angle : A angle formed between a surface of liquid drop and its adherend surface.

14. -Stronger the attraction between adhesive and adherend , smaller the contact angle -Zero contact angle is best to obtain wetting. 3. Surface energy : -Ability of adhesive to wet out over the surface of material is heated to surface energy. Harder the surface , Higher be surface energy , Increase the adhesive property of material.

15. 4. Surface contamination : -Cleaner the surface, better be the adhesion 5. Water : -Lesser the water content better be the adhesion.

16. ENAMEL BONDING

17. DENTIN BONDING

18. PROBLEMS DURING DENTIN BONDING In enamel, it is 95% inorganic hydroxyapatite by weight, in dentin it is 70% . Dentin contains more water and organic materails than does enamel. Hydroxyapatite crystals have a regular pattern in enamel whereas in dentin, hydroxyapatite crystals are randomly arranged in an organic matrix. Presence of smear layer makes wetting of the dentin by the adhesive more difficult. Dentin contains dentinal tubules which contain vital processes of the pulp, odontoblasts. This makes the dentin a sensitive structure.

19. Dentin is a dynamic tissue which shows changes due to aging ,caries or operative procedures. Fluid present in dentinal tubules constantly flows outwards which reduces the adhesion of the composite resin.

20. MOIST DENTIN vs DRY DENTIN

21. ROLE OF WATER IN BONDING

22. OVERWETTING PHENOMENON

23. ROLE OF WATER IN BONDING By etching dentin Smear layer and smear plug are removed Underlying 2-7 um of the dentin id demineralized Post-etching rinsing with water removes the dissolved enamel and leaves the demineralized dentin surface covered with water. About 70% of the demineralized dentin is occupied with water in areas from where minerals has been removed. This water is responsible for maintaining the collagen in expanded state and interfibrillar space are left open for penetration of resin. Clinically shiny hydrated surface is seen in the moist dentin. Pooled moisture should be remove by blotting or wiped of by slightly damped cotton pellet.

24. In other words ,water acts as plasticizer for collagen and keep it in a soft state. An appropriate amount of the water on the dentin surface promote the polymerization reaction of specific monomers. Reason for better bonding in moist dentin - Acetone trails water and improves penetration of monomer into the dentin for better micromechanical bonding. - Water keeps collagen fibris from collapsing, thus helping in better penetration and bonding between resin and dentin. IF DENTIN IS DRIED OR EXPOSED TO AIR WATER EVAPORATES LEAVING COLLAGEN IN A COLLAPSED STIFFENED STATE BECAUSE OF SURFACE TENSION FORCES This reduces the ability of subsequently applied agent to penetrate the collagen web.

25. Also when the collagen fibrils are brought closer ,secondary forces start becoming active between adjacent peptide chain in collagen triple helix. Which is not possible when water is present ,thereby increasing the stiffness or modulus of elasticity for collagen.

26. IF DENTIN SURFACE IS TOO WET (OVER WETTING PHENOMENON ) - One cannot check for the “frosted” etch appearance of the enamel. -There is reduction in bond strength because: – Presence of water droplets dilute resin primer thereby lowering the solublity of monomers, The monomers are present as a globules over the water layer which decreases bond strength. and compete with resin for sites in the collagen network which prevents hybridization .

27. ALCOHOL BASED AND WATER BASED PRIMER

28. On the other hand, when water based primer added to air dried , shrunken and demineralized dentin, two events may occur: i ) If water concentration of primer is low, water soluble resin monomer will stiffen the collagen meshwork faster than the water can plasticize the collagen and it willnot completely re-expand. ii) However water content of primer is large enough to plasticize the collagen faster than the resin/solvent stiffens it, The hydrophilic resin monomer infiltrates the network as it is gradually expanding

29. As a result more complete penetration can be expected. HOWEVER EXCESSIVE WATER IN THE PRIMER IS AVOIDED, AS IT DILUTES THE MONOMER CONCENTRATION DRASTICALLY. An effective wet bonding technique advocates the use of primer that contain hydrophilic resin monomer dissolved in organic solvent like acetone, ethanol.

30. On application of such primers on wet dentin This solvent aid in displacement of remaining water as well as carrying the polymerizable monomers into the open dentinal tubules and through the nanospheres of collagen web. Primer solvents gets evaporated , leaving the active primer monomer behind . These monomers have hydrophilic ends with an affinity for exposed collagen fibres and hydrophobic ends that forms a receptors for co-polymerization with adhesive resin. When water inside the collagen network is not completely displaced, the polymerization of resin inside the hybrid layer may be affected or the remaining water will compete for the space with resin inside the demineralized dentin.

31. -This excess water cause phase sepration of hydrophobic and hydrophilic monomer components resulting in blister and globule formation at resin-dentin interface. -Such interface deficiencies weaken the resin dentin bond and result in completely sealed tubules. -WET BONDING TECHNIQUE has following disadvantages i ) First acetone quickly evaporates from the primer bottle ii) Keeping the cavity wall wet after conditioning is that one cannot observe the white frosted appearance of enamel .

32. REFERENCE Fundamentals of operative Dentistry- A contemporary approach Textbook of Operative Dentistry- Vimal K. Sikri Sturdevent’s Art and science of operative Dentistry – 2 nd edition Textbook of operative Dentistry – Nisha Garg , Amit Garg Phillips science of Dental materials- 12 th Edition

33. THANK YOU !