Adhesion in operative dentistry- Basic concepts Flashcards
Define Adhesion:
Adhesion or bonding is the attachment of one substance to another. Force of interatomic attraction, strong (ionic, covalent, metallic) or the attraction between unlike molecules, weak (Van der Waals forces, hydrogen bonds)
What is chemical adhesion?
Interatomic attractions: swap or share electrons (ionic, covalent or metallic bonding)
What is physical adhesion?
Intermolecular attraction (Van der Waals forces, hydrogen bonds)
What is mechanical adhesion?
Macroscopic or microscopic interlocking and cementation.
Chemical adhesion (primary or real adhesion)
- It does not have much clinical significance.
- The adhesive resins (VERY WEAK), GICs and polycarboxylate resins
have real adhesion to the tooth (E and D). - Their carboxylic radicals bind to the Ca of the hydroxyapatite and
collagen organic portion.
What means adhesion in dentistry?
The forces or energies between atoms or molecules at an interface that hold two surfaces together.
Physical, chemical and mostly micromechanical interaction between an adhesive (C) and the substrates (A & B)
What components does Adhesion include?
- composite resins
- adhesion interface
- Dental tissue: enamel and dentin
What do we need to create in order the adhesive can penetrate?
micro retentions
How is the process called when we form micro retention?
This process is called CONDITIONING.
Whats chemical etching?
Etching: process of increasing the surface reactivity by
demineralizing the superficial calcium layer and thus creating enamel tags (5-50 m).
Whats physical mechanical procedure?
Procedures to get rough surfaces using direct erosion or an abrasive agent:
- with rotary instruments
- with inorganic abrasive particles at high speed (sand blasting)
We divide micro retention in two:
- chemical etching
2. Physical mechanical procedure
Adhesion with rotary instruments:
To create micro-retention areas we will use tools of cutting and abrasion as: burs, laser, polishing discs, grit blasting with small aluminumoxide particles.
Adhesion with abrasive particles at high speed:
Sand blasting
What is MACROretention?
Just for retained restorative materials, not adhered.
What macroretentions do we have?
- Adhesive forces
- cohesive forces
What are adhesive forces?
intermolecular forces which cause a tendency to resist separation in liquids. Between molecules of the same substance.
What are adhesive forces?
attraction forces between unlike molecules.
What`s an adhesive failure?
The bonding fails at the interface between the two substrates.
What’s a cohesive failure?
The bonding fails within one of the substrates.
What consequence does an adhesive failure have?
Lack of proper isolation will produce contamination with saliva and blood,(Tooth surface-Adh, RC-Adh)
What consequences do cohesive failures have?
- tooth surface
- contamination by saliva and blood etc.
- adhesive
Cohesive failures by tooth surface causes:
contamination, excessive etching (time, very strong acids or high concentration) or self cariogenic process, trauma or due to the technique (excessive traction when composite polymerizes if enamel is weakened- demineralised it is likely to break)
What’s a cohesive failure by RC?
Contamination by saliva and blood, trauma, improper technique especially polymerizing layers too thick.