8/26: Lecture 2 - Adhesives and Bonding Flashcards
What is the purpose of beveling?
reduce microleakage at cervical and ascending walls in class 2
What does beveling expose?
ENDS of enamel rods = reveals prismatic enamel = etches better
What is the purpose of bevelling for axiopulpal?
Resistance by distributing stress
Where do you bevel?
in ENAMEL, NOT in deep preps where a bevel would remove all enamel or where gingival floor is on cementum/dentin
When should you NOT bevel?
in class 3 if heavy centric contact to margin
Where is a flare in a class 2 composite prep?
- Buccal flared > 100
- Lingual Flared > 90
Buccal contact can remain in many cases
Slight flare occlusal of prep
Where is a flare in a class 2 amalgam prep?
both exit angles are 90 degrees (need S curve on buccal to achieve)
- NEED to break buccal contact
Should you have a gingival bevel for amalgam?
NO
Where is a flare in a class 3 composite prep?
- Internal Labial flare
- Gingival flare to exit at 90 degrees
- Labial wall flare of 100 degrees at cavosurface = exposes ends of enamel rods
What is the purpose of etch?
Increases surface wetting by increasing surface area available for bonding
What is surface wetting?
ability of liquid to maintain intermolecular contact with a solid surface
Etching
__________ free energy to _______ the surface tension of bonding material
raises; exceed
What spaces does etching produce?
Spaces where bond agent resin can penetrate and form resin tags
What layer does etching remove?
Smear layer
What is a smear layer?
Mixture of tooth debris, saliva, blood cells, bacteria and does NOT accept bond well
How do you use etch?
Place for 15 seconds, rinse for 10
What is primer?
hydrophilic (allows for binding to moist dentin and wetting of surface) monomers (like ethanol/water, acetone) to draw bond agent in
Is bond hydrophobic or hydrophilic?
Hydrophobic
What kind of binding does bond use?
micro-mechanical binding to interlock into surface irregularities
How does bond bind to enamel?
interlocking with enamel rods
How does bond bind to dentin?
interlocking with dentin collagen, which depends on MMPs
What is bond more predictable with?
Predictable with enamel (especially incisal and middle 3rd) but less with dentin as the bond strengths vary due to heterogeneity (very organic)
What system is etch separate frmo bond agent?
Etch and rinse (total etch)
What are the types of etch and rinse systems?
Primer and bond can be separate (3 step) or together (2 step)
What are pros of the etch and rinse system?
larger hybrid layer, adhesive can penetrate further, more predictable, stronger bond because enamel is adequately prepared
What is the hybrid layer?
micromechanical interlocking of demineralized intertubular collagen and resin, good for bonding to dentin
How is the hybrid layer formed?
by etching, washing, primer, adhesive (resin), light cure
What does overetching lead to?
Unprotected layer = underfilled restoration
What does overdrying lead to?
Collagen collapse = lower bond strength
What does underdrying lead to?
collagen is too wet = blister spaces where primer and adhesive separate
What etch doesn’t have a separate etch step?
Self-etch
Describe the self etch system
Acid is apart of the primer (2 step) or primer/bond (1 step: all-in-one)
What is a con of self etch?
will NOT etch unprepared enamel, collagen degradation over time, lower bond strength
What layer of the tooth does selective etch etch?
only etch the enamel NOT the dentin
What layer of the tooth does complete etch etch?
enamel AND dentin
What etch systems can universal adhesives be used with?
can be used with total etch, self-etch, and selective-etch
We use!!!!
What is the game changer for universal adhesives?
10-MDP
What does 10-MDP allow for?
Bonding to many surfaces
Describe the chemical reaction of universal adhesives
Monomer (phosphate ester) chemically interacts via ionic bonding to calcium in hydroxyapatite
What is the function of adhesive?
resin tags (macro and micro) interlock into surface irregularities
What are the steps of a composite restoration?
- Etch for 20 seconds to enamel and 15 to dentin or selective etch
- Wash for 10 seconds and dry enamel and dentin lightly (moist)
- Apply primer (not with adhesive universal)
- Apply adhesive
- Light cure (470 nm) = initiate
- Place composite
When should you re-etch?
if tooth gets contaminated with saliva, re-etch for 10 seconds, rinse and dry, until frosted ename
Should you etch longer for fluoridated teeth?
YES because more resistant to acids
How do you repair old composites?
roughen old composite with diamond bur, etch, wash, dry, bond, thin, cure, and add new composite
What is the shape of type 1 enamel rods? from dissolution of what?
honeycomb; enamel rod cores
What is the shape of type 2 enamel rods? from dissolution of what?
cobblestone; enamel rod peripheries
Where are type I and type II enamel found?
In occlusal and middle thirds of teeth
What enamel gives the BEST bond?
Type 1 and 2
What kind of enamel tags does cervical enamel have?
Shorter and fewer
What do shorter and fewer enamel tags create?
Less prism delineation
What MPa does using adhesive result in?
20-25MPa
What kind of MPa bond strength does perpendicular enamel have?
25 MPa
Where is perpendicular enamel found?
ENDS of rods
- at cavosurface margin of class 1 prep and bevels of class 2 preps
What kind of MPa bond strength does parallel enamel have?
7-10 MPa bond strength
Where is parallel enamel found?
SIDES of rods
- in internal walls of occlusal preps and in gingival floor of box in Class 2 prep
Is dentin more/less predictable with bonding?
LESS because its heterogenous
Where do odontoblastic processes extend to?
Tubules
Where is peritubular dentin?
Directly around tubule
Is peritubular dentin organic or inorganic?
INorganic
Where is intertubular dentin?
Between tubules
Is intertubular dentin organic or inorganic?
ORGANIC
What is intertubular dentin rich with?
Collagen = allows for bonding
What are factors affecting bond to dentin?
Cavity depth, caries, moist/dry
