composition of 6th generation dentin bonding agent according to Vimal K Sikari
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Vimal K Sikri 6th generation dentin bonding agent composition
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6th generation dentin bonding agent composition Sikri
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Sikri "operative dentistry" "6th generation" dentin bonding composition HEMA BisGMA
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6th generation dentin bonding agent composition Sikri
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Vimal Sikri "textbook of operative dentistry" bonding agent generation classification composition self-etching
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6th generation dentin bonding agent composition self-etching primer
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Sikri "sixth generation" dentin bonding "type I" "type II" composition HEMA phosphate ester
Based on the research gathered (including a reference PDF that cites Sikri's Textbook of Operative Dentistry directly), here is the comprehensive answer:
6th Generation Dentin Bonding Agents - As per Vimal K Sikri
Vimal K Sikri's Textbook of Operative Dentistry classifies 6th generation bonding agents as self-etching systems introduced in the late 1990s, where the primer and etchant are combined, eliminating a separate acid-etching step. They are divided into two types:
Type I - Two-Step / Self-Etching Primer Systems (Non-Rinsing Conditioner)
These involve two separate bottles - a self-etching primer (bottle 1) and an adhesive resin (bottle 2). No separate rinsing step is needed.
Composition of the Self-Etching Primer (Bottle 1):
| Component | Role |
|---|---|
| Acidic functional monomers (e.g., 10-MDP, Phenyl-P, methacrylate phosphoric esters) | Act simultaneously as etchant and primer; demineralize smear layer and dentin |
| HEMA (2-Hydroxyethyl methacrylate) | Hydrophilic monomer; promotes wetting and adhesion to dentin |
| Water | Acts as a reaction medium for the acidic monomers |
| Acetone or ethanol | Solvent carrier |
Composition of the Adhesive Resin (Bottle 2):
| Component | Role |
|---|---|
| Bis-GMA (Bisphenol-A diglycidyl methacrylate) | Hydrophobic cross-linking resin base |
| HEMA | Bridges hydrophilic-hydrophobic interface |
| Acetone/ethanol | Solvent |
| Photoinitiator (camphorquinone) | Light-curing initiator |
Examples: Clearfil SE Bond (Kuraray), Clearfil Liner Bond IIV, AdheSE (Ivoclar Vivadent), NRC followed by Prime and Bond NT (Dentsply)
Type II - One-Step / Self-Etching Adhesive Systems ("All-in-One")
An attempt to incorporate etchant, primer, and adhesive all into a single container. In practice, many of these require premixing of components just before use (e.g., Prompt-L-Pop) or use chemically activating pellets/brushes.
Composition (All-in-One):
| Component | Role |
|---|---|
| Acidic methacrylate monomers (e.g., methacrylate phosphoric esters, maleic acid derivatives) | Simultaneous etching and priming |
| HEMA | Wetting and adhesion |
| Bis-GMA or UDMA | Resin matrix |
| Water | Ionization of acidic monomers |
| Acetone/ethanol | Solvent |
| Photoinitiator | Curing |
| Fluoride (in some formulations) | Anti-caries benefit |
Examples: Prompt-L-Pop (3M ESPE) - contains HEMA, Bis-GMA, methacrylate phosphoric esters, 1,6-hexanediol dimethacrylate, and methacrylate-functionalized polyalkenoic acid; Touch & Bond, Brush & Bond, OneCoat Self-Etching Bond (Coltene), Xeno III
Key Features (per Sikri's classification)
- No separate acid-etching or rinsing required
- Smear layer is incorporated (modified/dissolved but not washed away) into the hybrid layer
- Lower bond strength compared to 4th and 5th generation systems
- Reduced post-operative sensitivity versus total-etch systems
- Reduced technique sensitivity (no wet-dry bonding dilemma)
Note: Sikri's textbook (Textbook of Operative Dentistry, CBS Publishers) classifies bonding agents in a generational framework consistent with the Vargas classification. The 6th generation's defining chemical feature is the acidic functional monomer (like 10-MDP or phenyl-P) which simultaneously etches and primes the dentin surface, making a separate phosphoric acid etch step unnecessary.
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