- NEED HELP? CALL US NOW
- +919995411505
- [email protected]
Dentin Bonding Agents
Known as a "bonderizer" bonding agents (spelled dentin bonding agents in American English) are resin materials used to make a dental composite filling material adhere to both dentin and enamel.
THINKS TO BE KNOWN
Adhesion is derived from Latin meaning "a state in which two surfaces are held together by interfacial forces like valence forces or interlocking forces or both". (The American Society for Testing and Materials)
Process of adhesion to occur , we need to understand the role of following components:
- Adhesive
- Adherend
- Adhesive Strength
Adhesive is defined as a material , frequently a viscous fluid that joins two substrates together by solidifying , resisting separation & transferring a load from one surface to the other.
Adherend is defined the surface to which an adhesive adheres.
Adhesive Strength is the measure of the load-bearing capacity of an adhesive joint.
BONDING AGENTS
- Bonding agents are often methacrylates with some volatile carrier and solvent like acetone.
- They may also contain diluent monomers.
- For proper bonding of resin composite restorations, dentin should be conditioned with polyacrylic acids to remove the smear layer, created during mechanical treatment with dental bore, and expose some of the collagen network or organic matrix of dentin.
CHEMICAL PROCESSES INVOLVED IN BONDING TO DENTINE
- Mechanism of bonding- dentin
- Removal of the smear layer and etching of dentine
- Priming of the dentine surface
- Bonding of the primed dentine surface to the restorative material
CLASSIFICATION OF DENTIN BONDING AGENTS
The bonding agents are classified as follows:
- According to generations
- Based on mode of application
- Based on number of steps
- Based on etching pattern
CLASSIFICATION BASED ON GENERATIONS
First-Generation Adhesives (1960)
- Development of surface-active comonomer NPG-GMA
- Theoretically, this comonomer could chelate with calcium on the tooth surface to generate water-resistant chemical bonds of resins to dentinal calcium
- Bond strength 2 to 3 MPa.
Drawbacks
- It showed poor clinical results
- Example: Cervident (SS white), cosmic bond.1,2
Second-Generation Adhesives (Late 1970s)
- Phosphate ester dentin bonding agents were introduced containing phenyl P and HEMA in ethanol.
- Its mechanism of action was based on the polar interaction between negatively changed phosphate groups in resin and positively changed Ca++ in smear layer.
- The bond strength was 5 to 6 MPa.
Drawbacks
- Loosely attached smear layer and hydrophobic nature.
- Example: ScotchBond (3M dental), Clearfil bond system.
Third-Generation Adhesives (1980s)
- The third generation materials were designed not to remove the entire smear layer but rather to modify it and allow penetration of acidic monomers, such as phenyl-P and Penta.
- These introduced acid-etching to heavily alter or to remove the smear layer and demineralizing dentin and a separate primer (bifunctional monomer in a volatile solvent) designed to penetrate dentin by its own monomer and those of adhesive monomers.
- Adhesive is an unfilled or partially filled resin that may contain some component of primer (e.g. HEMA) in an attempt to promote increased bond strength.
- Bond strength is 3 to 8 MPa
- Examples: ScotchBond 2, Tenure, Universal bond 2, Coltene ART.
Fourth-Generation (Early 1990s)
- When primer and bonding resin are applied to etched dentin,they penetrate the intertubular dentin forming a resin dentin interdiffusion zone or hybrid layer.
- They have the ability to bond as strongly to dentin as to enamel (total etch).
- Ability to bond to moist dentin (wet bonding).
- Multiple substrate bonding to metal, amalgam, porcelain and indirect composite.
- Bond strength 13 to 30 MPa.
- Examples: All-Bond 2, OptiBond FL and ScotchBond multipurpose.
Fifth-Generation Adhesives
These are essentially distinguished by being ‘one-step’ or ‘onebottle’ system. This is a bit of a misnomer because these products are applied in two steps (etchant + primer and adhesive) in one bottle.
- Bond strength is 3 to 25 MPa.
Drawbacks
- They lack many of the components necessary to perform multisubstrate bonding
- Multiple coats of these agents are required
- Examples: Prime and bond, single bond, OptiBond Solo and OptiBond Solo Plus.1,2
Sixth-Generation Adhesives
It was introduced in late 1990 and early 2005:
- They dissolve the smear layer when applied and do not require rinsing.
- Minimize postoperative sensitivity as they do not exposedentinal tubules.
- Bond strength to enamel and superficial dentin are typically greater than deep dentin.
Seventh-Generation Adhesives
Introduced in Late 2002
- Self-etching adhesive
- Require no mixing
- Not compatible with self-cured composite cores or resin cements
- Single bottle containing acidic adhesive
- Examples—iBond
- Bond strengths and marginal sealing to be equal to the sixthgeneration system.
Eighth-Generation
- Dual-cured self-etch adhesive for direct and indirect restorations with self-, light- and dual-cured resin materials.
CLASSIFICATION-BASED MODE OF APPLICATION
1 .Adhesives which modify the smear layer and incorporate it into the bonding process.
|
One stepEg : Prime and Bond2.1 |
Two stepEg : Optec Universal Bond |
2. Adhesives which completely remove the smear layer are subdivided into two and three step application.
|
Multiple bottleEg : All-Bond 2, Scotchbond multipurpose |
One bottleEg : OptiBond SOLO |
3. Adhesives which dissolve the smear layer, rather than remove it.
|
||
| 4. Less postoperative sensitivity than total etch. |
CLASSIFICATION BASED ON NUMBER OF STEPS
CLASSIFICATION BASED ON ETCHING PATTERN
- Based on their application method,
- The bonding agents could either be total-etch or self-etch
