Surface and Interfaces Flashcards
Adhesive principles are used in which dental specialties?
ALMOST ALL Operative prosth peds ortho endo
adhesion
when 2 unlike substances join together on being brought into contact because of forces of attraction between them
cohesion
attraction between like molecules
adhesive
material used to produce adhesion
adherend
subtance to which an adhesive is applied
application of adhesive technology is very critically dependent on…
practical technique
knowledge of physics and chemistry of surfaces is ___
essential
surfaces have ______ from the bulk of the material
different properties
Adhesion critically depends on _____
surface properties
What are the requirements of adhesion?
- fluid adhesive
- reactive adherend/solid surface
- interaction bc adhesive and adherend
- creation of a stable interface
surface tension
force of attraction exterted on surface mols of a LIQUID by the mols beneath the surface
Surface free energy
atoms on SOLID surfaces may have higher energy than the atoms in the bulk of the material
The atoms on the surface are not surrounded by atoms of its own nature, so:
- surface atoms interact more strongly with eachother
- May attract atoms/mols = more reactive
Adsorption
adhesion of atoms/ions/biomolecules/molecules of gas/liquid/dissolved solids on a SURFACE
Absorption
absorbed substance is incorporated into the BULK of material
what are they types of adsorption
cemisorption
physical adsorption
chemisorption
type of adsorption chemical rxn (usually irreversible) has taken place DESIRED FOR ADHESIVES
physical adsorption
establishment of Van der Walls forces
Weak/secondary bonds
More readily reversible
contact angle
angle of contact made by a drop of liquid on a surface
Measures ability of liquid to wet a surface - determines reactivity of surface
The more reactive the surface, more water is going to interact w it = lower contact angle
hydrophobic surfaces have ____ contact angles
Large
poor wetting hydrophobic surface
hydrophilic surfaces have ____ contact angles
small/0
excellent wetting hydrophilic surface
What 2 factors determine the reactivity of a solid surface and adhesion
- chemical and physical-chemical reactivity between surface and adhesive
- Physical form
- roughness - mechanical interaction
- porosity - hybridization
How does contact angle relate to reactivity of a subtance
More reactive surface = more water will interact with it = drop will spread more = LOW CONTACT ANGLE
What are the three mechanisms for adhesion? (1 or more can contribute to bond strength)
- chemical bonding
- micromechanical adhesion
- hybridization bonding
If a surface is very reactive to an adhesive, adhesion between the two will be ______
IMPROVED
