Enamel bonding Flashcards
what is adhesion
force that binds two dissimilar materials together when they are brought into intimate contact
what does the ability of adhesive depend on to contact a substrate
the wet ability of the adhesive on that particular substrate
what is non wetting
hydrophobic
what is wetting classes as
hydrophilic
what is wetting measured by
the contact angle
smaller contact angle more wettable
enamel
hardest and most mineralised substance the body
once formed no blood vessels r nerves
composition of enamle
96% hydroxyapitite 1% inorganic protiens 3% water hexagonal rods of minerals prismatic arrangement perpendicular to tooth surface
what can composite bonded to enamel do
improve appearance of teeth
mask further discolouration
prevent further wear and tear
what 2 things does acid etching do
increase surface roughness
raises surface energy
how does etching increase surface roughtness
- acid base reaction prompts partial dissolution of hydroxyapatite
- structural changes: loss of enamel prism periphery and prism core constituents
- increase the roughness/bonding area
how does etching raise surface energy
- Acid removes pellicle and exposes underlining surface of enamel
- Raises surface tension encouraging wetting (resin/applicant needs to have a lower surface energy than enamel, therefore acid etching increases probability of adhesion)
- Acid removes surface contaminates
what is needed to enhance addition/wetting
surface energy of the solid should be greater than the liquid to enhance addition/wetting
summary of what etching does
makes a retentive surface
micro mechanical bonding
increase surface area and energy
3 things to consider to prevent clinical probelsm
patent selection
enamel prophylaxis
application of etchant
what are resins and what does this mean
non polar
- prevents resin adapting to enamel so poor bond
