lecture 2 Flashcards
attraction between similar molecules or atoms
cohesion
cohesive failure
attraction between unlike molecules, attraction between two contracting surfaces
adhesion
adhesion failure
material bonded to another material by means of an adhesive
adherend
substance that promotes adhesion
adhesive
joining two materials by means of an adhesive
adhesive bonding
adhesion classifaction
physical bonding- very weak
chemical bonding- very limited with dissimilar materials
mechanical- interlocking; adhesive interlocks into surface irregularities (THIS IS THE DENTAL ADHESION MECH)
what is the dental adhesion mech
mechanical
(micro-mechanical bond want)
microscopically intimate interface= improve _____
improve interlocking
the ability of a liquid to maintain intermolecular contact with a solid surface
surface wetting
adhesion requirments:
- microscopically intimate interface= improve interlocking
- good surface wetting
improved surface wetting = increased
increased surface energy by an increase in surface available for bonding (by etching; roughened surface)
etching transforms smooth enamel into
an irregular surface
enamel bonding=
dentin bonding=
enamel bonding= very predictable (~25-30 MPa)
dentin bonding= more challenging (bond strength varies)
enamel etching
type I
type II
type III
type IV
type V
type I- honeycomb= from dissolution of prism(enamel rod) CORES
type II- cobblestone=from dissolution of prism(enamel rod) PERIPHERIES
type III- combo of I and II
type IV- pitted
type V- Aprismatic (flat and smooth)
what enamel etching types are found in occlusal and middle thirds of teeth which are the best bonds to acheive
type I and II
chemical “drilling”
acid etching enamel
what is most effective for enamel retention
30-40% phosphoric acid
place acid etching ____seconds prior to rinsing and it removes about ____microns of enamel
15 seconds prior to rinsing
removes 10 microns of enamel
acid etching creates porous layer ____microns deep
5-50
rinse with water ____seconds after etching. why?
10 seconds
to remove acid and leave enamel surface clean for bonding
etching increases:
wettability and surface area of the enamel
etching raises the surface of FREE ENERGY to exceed:
the surface tension of bonding material
this is the mechanical interlocking that we are trying to achieve by producing spaces where resin can penetrate to form resin tags
etching enamel
after etching is complete:
apply bond agent resin (low viscosity)
bond flows into microporosities and polymerizes to
micromechanical bond
what are the bonding systems
- etch-and-rinse (total etch)
- self-etch
explain etch and rinse
(total etch)
-etch seperately
-prime
-bond
-or prime + bond combo
explain self-etch
-no phosphoric acid-etch step
-acid part of primer or primer/bond agent
if you dont use this step, then you arent getting the smear layer off
etching
what bonding system do we use at umkc
etch-and-rinse (total etch) with prime+bond combined
what are the two options for etch-and-rinse (total etch) bonding system
- 3 step(2 bottle) total etch
- 2 step(1 bottle) total etch
explain the 3 step(2 bottle) etch-and-rinse bonding system
a. etchant
b. primer
c. bonding agent (scotch bond multi-purpose)
explain the 2 step(1 bottle) etch-and-rinse bonding system
a. etchant
b. primer and bond agent combined
(like prime and bond NT, PQ1, peak, optibond solo plus)
explain the self-etch 2 step bonding system
self-etch primer
a. 2-step: acidic primer and bonding agent
b. acidic primer partially dissolves smear layer, allows penetration of bond resin
(clearfil SE bond example)
explain the self-etch 1 step bonding system
self-etching adhesive (all-in-one)
a. 1-step- most variable/least predictable
b. acidic primer and bone resin are one solution
(i-bond; some require mixing)
what are the advantages of rinse and etch systm
more predictable, STRONGER BOND, enamel adequately prepared
what are the disadvantages of rinse and etch system
*collagen collapse is possible (by user error)
-etch zone is often deeper than hybrid layer
(exposed demineralized, collagen fibrils)
(post operative sensitivity)
self etch advantages
-no seperate etch: overdried, collapsed demineralized collagen not a problem
-etched zone and hybrid layer comparable width
-low post-operative sensitivity
-time efficiency
self-etch disadvantages
-not compatible with self-cure, dual-cure composite
-acidic monomers, low pH, kills the basic amine activator
-will not etch unprepared enamel
universal adhesives can be used in:
total etch
self etch
selective etch
(etch enamel only with phosphoric acid)
{used at umkc: etch-and-rinse enamel and bond dentin}
what allows the universal adhesive to be universal
10-MDP
mechanism of action for universal adhesive:
a monomer that chemically interacts via ionic bonding to calcium in hydroxyapatite
(monomer is a phosphate ester)
bond to dentin collagen is influenced by
matrix metalloproteinases (MMPs)
-which are collagen enzymes that metabolize unhybridized collagen
MMPs are present on ____
collagen fibrils
this inhibits MMP activation
chlorhexidine (cleans up area)
adverse pulp rxn comes primarily from
bacteria remaining in or penetrating the preparation
what are the 5 bonding clinical success requirements
- knowledge of substrate
dentin vs. enamel
deep vs superficial dentin
caries-affected dentin - good cavity prep and margins
mechanical retention - rubber dam and matrix wedges
- correct use of the bonding agent
wet/moist bonding, total etch, self-etch - bond agent compatible with resin composite
how do bond strengths to dentin vary
- region of tooth (superficial higher bond strength than deeper)
- flat surfaces higher than box cavities
- c factor
- thickness of increment of comp. resin
1mm better than 2 mm increments - adhesive system used
- operator
- intrinsic wetness of tooth
- dryness vs wetness
the location of adhesion matters
- incisal third and middle third enamel
-strong - cervical enamel
-shorter and fewer enamel tags (compared to incisal and middle third)
-less prism delineation
(due to presence of prismless enamel;
found in cervical third of 70% of teeth)
doing these will reduce microleakage at cervical and ascending walls in class II preps
bevels and adhesive dentistry
bevel what of prep which is necessary when in enamel
bevel gingival floor
enamel prepared with bur (beveled) etches better because
- exposes ends of enamel rods
- reveals prismatic enamel
when do we not bevel
deep preps
-when gingival floor is on cementum or dentin
this is the goal of adhesive dentistry with composite resin:
in enamel-
in dentin-
micromechanical bond
in enamel- interlocking with enamel rods
in dentin- interlocking with dentin collagen
enamel make up
95-98% inorganic matter by weight
90-92% hydroxyapatite by vol
1-2% organic matter by weight
4% water
enamel
perpendicular oriented enamel
parallel oriented enamel
perpendicular oriented enamel:
-cavosurface margins of class I preps
-bevels of class II preps
-ends of enamel rods
parallel oriented enamel:
-internal walls of occlusal preps
-gingival floor of box of class II preps
-sides of enamel rods
this increases surface area and surface energy by allowing wetting of tooth
etch surface
by etching, this allows wetting the tooth with
hydrophobic adhesive resin (remember enamel has minimum water)
what interlock?
resin tags
-micro and macro tags into surface irregularities
dentin characteristics
55% mineral by volume
30% collagen
15 % water
dentin is very heterogenous
dentin anatomy review.
tubules are:
very inorganic:
very organic and collagen rich:
tubules are: fluid filled
very inorganic: peritubular dentin
very organic and collagen rich: intertubular dentin
dentin tubule diameters
near DEJ:
near pulp:
near DEJ: .5 um
near pulp: 2.5 um
(larger near pulp
deeper you go into dentin, the
more and wider the tubules are= more fluid and less intertubular dentin
mix of tooth debris, often contaminated with saliva, blood, cells, and bacteria
smear layer
do you bond to smear layer?
NO
remove smear layer with
acid etch
intermingled layer of collagen and resin
hybrid layer
this layer is what we want to form when bonding to dentin
hybrid layer
problems forming the hybrid layer
must be the perf balance
-avoid over etching
-overdrying
-under drying
steps of forming hybrid layer properly
- acid etch 15 seconds on dentin (less time than enamel)
- wash and LIGHTLY dry
=*hydroxyapatite removed, water remains to support collagen fibers - apply primer
- apply adhesive
- light cure
hybrid layer forms!
over-etching=
results in underfilled restorations
-means acid etched too long
-demineralized zone too thick
-primer cant infiltrate far enough
-leaves unprotected layer
over-drying =
results in lower bond strengths
-collagen collapses=lower bond strength
under-drying=
excess water
-poor hybrid layer formed
-resin unable to infiltrate intertubular dentin
-“blister spaces” where primer and adhesive seperate
what are the disadvantages of bonding systems
-too many steps= operator errors
-dont remove smear layer
-delicate treatment of dentin necessary
phosphoric acid gel (30-40%)
etchant
HYDROPHILIC monomers in HEMA solvent
-acetone, ethanol/water, water
primer
HYDROPHOBIC dimethacrylate monomers
-initiators and activators
adhesive bonding resin/agent
polymerization process (setting up process)
adhesive/primer is a chemical rxn that takes monomers to->
polymers
this concerts initiator(chemical) into a free radical
-free radial starts polymerization rxn
-light or chemical
activator
(part of polymerization process)
light as an activator explained
light: (blue light 570nm for composite)
camphorquinone-> free radical-> polymerization reaction
chemical as an activator explained
chemical (tertiary amine)
benzoyl peroxide(initiator)-> free radial -> polymerization reaction
bonding procedure steps
- acid etch
20s enamel
15s dentin , if doing so - rinse
10s
gently dry- enamel should be dry, dentin slightly moist - apply primer (not if using adhese universal )
- bond
- cure
initiate polymerization for 20s - place composite
dentin bonding mechanism
1. this demineralizes collagen fibrils=
2. this supports collagen network=
3. this this applied to polymerized=
- acid-etched
- water
- dentin bond agent
primary dentin bond mechanism is from
hybrid layer
there is better bond strength in ___dentin
lower bond strength in ___dentin
superficial dentin
carious dentin
moist vs. dry dentin?
moist is better
