Current Adhesives and Composite Bonding Flashcards
What is cohesion?
attraction between similar molecules or atoms
What is adhesion?
attraction between unlike molecules, attraction between two contacting surfaces
What is the adherend?
material bonded to another material by means of an adhesive
What is adhesive?
substance that promotes adhesion
What is adhesive bonding?
joining two materials by means of an adhesive
Is a physical bond weak or strong?
very weak
Is a chemical bond strong or weak?
Very limited with dissimilar materials
How does a mechanical bond work?
◦ Interlocking
◦ Adhesive interlocks into surface irregularities
◦ THIS IS THE DENTAL ADHESION MECHANISM
What is the main dental adhesion mechanism?
mechanical
What does microscopic intimate interface do to interlocking?
improves interlocking
What is surface wetting?
the ability of a liquid to maintain intermolecular contact with a solid surface
What does improved surface wetting do to surface energy?
increases surface energy
How do you increase the surface area?
◦ INCREASE SURFACE AVAILABLE FOR BONDING
◦ BY ETCHING
◦ Roughened surface (diamond bur for bevels)
◦ Etching transforms smooth enamel into an IRREGULAR surface
What is the dental adhesion of enamel?
~25-30 MPa
- very predictable
What is the dental adhesion of dentin?
◦ Bond strengths vary
- more challenging
What is the type I enamel etching?
- “honeycomb”
- from dissolution of prism (enamel rod) CORES
What is the type II enamel etching?
- “cobblestone”
- from dissolution of prism (enamel rod) PERIPHERIES
Where are type I and type II enamel etching areas found?
occlusal and middle thirds of teeth
What areas of enamel etching are the best bonds?
TYPE I AND II
What is the type III enamel etching?
combination of I and II
What is the type IV enamel etching?
pitted
What is the type V enamel etching?
asprismatic (flat and smooth)
What is acid etching enamel?
- chemical “drilling”
- creates porous layer 5-50 microns deep
- called conditioner
___% phosphoric acid is most effective for enamel retention
30-40%
How much enamel does acid etching remove?
10 microns
How do you apply acid etching enamel?
RINSE with water for 10 seconds after etching
◦ To remove acid and leave enamel surface clean for bonding
Etching raises the surface free energy to _______ the surface tension of bonding material
EXCEED
Etching produces spaces where resin can penetrate to form…
resin tags
After etching you should apply bond agent resin why?
- low viscosity so it can flow into microporosities
- polymerizes to micromechanical bond
What is the etch-and-rinse (total etch) system?
- Etch separately
- Prime
- Bond
- Or Prime + Bond combined
What is the self-etch system?
- No phosphoric acid-etch step
- Acid part of the primer or primer/bond agent
What is the 3-step (2-bottle) total etch system?
a.Etchant
b.Primer
c.Bond agent
(scotch bond multipurpose)
What is the 2-step (1-bottle) total etch system?
a.Etchant
b.Primer and bond agent combined
(Prime and Bond NT, PQ 1, Peak,
Optibond Solo Plus)
What is the 2 step self-etching bonding system?
- acidic primer & bonding agent
◦ Acidic primer partially dissolves smear layer, allows penetration of bond resin
◦ Clearfil SE Bond; Clearfil Liner Bond 2V
What is the 1 step self-etching bonding system?
– most variable/ least predictable
◦ Acidic primer and bond resin, one solution (Many require mixing)
◦ Examples: Xeno, i-Bond, Bond Force (no mix)
What are the advantages of the rinse and etch system?
◦ More predictable, stronger bond
◦ Enamel adequately prepared
What are the disadvantages of the rinse and etch system?
◦ Collagen collapse is possible
◦ Etched zone is often deeper than hybrid layer
◦ Exposed demineralized, collagen fibrils
◦ Post-operative sensitivity
What are the advantages of self-etch systems?
◦ No separate etch: overdried, collapsed demineralized collagen not a problem
◦ Etched zone and hybrid layer comparable width; however, some exposed collagen
◦ Low post-operative sensitivity
◦ Time efficiency
What are the disadvantages of self-etch systems?
◦ Not compatible with self-cure, dual-cure composite
◦ Acidic monomers, low pH, “kills” the basic amine activator
◦ Will not etch unprepared enamel
◦ Self-etch primer systems
What are the disadvantages of the self-etch adhesives (all-in-one)?
◦ Lower bond strength
◦ Long-term breakdown?
◦ Collagen degradation over time
What can you use with universal adhesives?
Can be used in total etch, self-etch or selective-etch mode (etch
enamel only with phosphoric acid)
- we use at UMKC
What is the chemistry game changer of universal adhesives?
10-MDP
◦ Methacryloyoxy-decyl-dihydrogen-phosphate (10-MDP)
What is the mechanism of action of a universal adhesive?
A monomer that chemically interacts via ionic bonding to calcium in hydroxyapatite
What is the monomer for universal adhesives?
a phosphate ester
Should you directly etch the pulp?
nope