Dental pt1 Flashcards
Surface phenomena include
Surface tension
Wetting
Adhesion
Adsorption
Capillary action
(draw pic to memorize)
Surface energy
atoms, molecules surfaces liquids, solids > E interior
(E extrovert > introvert)
Surface E of liquid aka
surface tension
effect surface tension
form drops
Def wetting
degree spreading liquid drop on solid surface
Good wetting promotes, indicates
capillary penetration
adhesion
strong attraction liquid, solid
Degrees wetting
0: complete wetting
low: good wetting
>90: poor wetting
Example wetting
Hg NO spreads on glass -> poor wetting
H2O spreads on glass -> good wetting
bonding agent spreads on tooth surface - good wetting -> penetration, adhesion composite
Degree wetting etched enamel - bond
0
complete wetting
Degree wetting acrylic - H20
75
Degree wetting amalgam - H2O
80
Degree wetting teflon - H2O
110
Adsorption def
to reduce surface energy -> atoms, molecules mobile will concentrate at high energy surfaces
(pic at high level ->mobile conc at high E surface)
Example adsoprtion
charcoal dust - absorb quantities gas
soap molecules concentrate at surface H2O -> reduction surface E
Adsorption effect strongest
strongest - large E saving -> surface covered -> slows down
Capillary penetration formula
h=2ycosO/rdg
h: capillary elevation
y: surface tension
O: contact angle
r: tube radius
d: liquid’s density
g: gravitational constant
Penetration coeff (cm/s)
PC= ycosO/2n
y: surface tension
O: contact angle
n: viscosity
Def penetration coeff
rate movement liquid into capillary space
Penetration coeff PC depends on
surface tension
contact angle
viscosity
(formula)
PC fluoride gel
0.05 cm/s
(fluoride lowest -> 0.05 (like the movie) -> photopol. 1.72 -> chem. 4.9
PC fissure sealant/ photopol.
1.72 cm/s
PC fissure sealant/ chem.
4.9 cm/s
Def adhesion
attachment material in contact that resists forces separation
Example adhesion in dental
porcelains - metals
resins - tooth
denture base - mucosa
Retentive force def
capillary space btw denture, mucosa
Retentive force formula
F=2CA/a
F: retentive force
C: surface tension
A: extent surface
a: thickness fluid film
Classification bonding adhesive bonding
- Mech adhesion
a. Microscopic penetration
b. Stresses - Diffusion -1 phase diffusion -> penetrates surface 2nd phase -> hybrid layer (composite 2 materials)
- Chem adhesion
a. 1st valence forces: ionic, covalent, metallic
b. 2nd valence forces (van der waals)
Mech adhesion depends on
interlocking 2 phases
include microscopic attachments (penetration)
Ex mech adhesion dental
resin bonding to etched enamel
stresses of porc around metal core
Mech adhesion model (size surface irregularities)
macromech retention (sandstone)
micromech retention (HF etching, sand blasting)
Def diffusion bonding
1 phase diffusion -> penetrates surface 2nd phase -> hybrid layer (composite 2 materials)
Factors affects strength adhesive bonding
cleanliness
corrosive envi
PC
chem rxn
shrinkage adhesive (poly shrinkage stress)
thermal stress
(strength bonding - outside, within
-> outside - cleanliness ; corrosive envi ; how interxs w/ ppl (chem rxn)
-> within - how i penetrates (PC) ; hot tempered stress (thermal stress) ; polyadhesive stress)
enamel charac
highly mineralized
steps adhesion to enamel
35-50% phosphoric acid - selective demin -> hydroPHOBIC resins/adhesives penetrates -> form tags -> bond strength thru mech interlocking (20-22MPa)
Ad adhesion to enamels steps
restorative/ min invasive cavity prep
>< amalgam fillings (box form prep)
steps adhesion to dentin
- conditioning/ acid etching
a. dissolves smear layer
b. partially declc dentin to 5um
c. opens dentinal tubules - resin impregnation
a. hydroPHILIC primer/ coupling agent (HEMA) + glutaraldehyde penetrates both tubules -> declc peritubular dentin
b. primer stabilizes collagen -> penetration bonding resins (bisGMA, UDMA)
(dentin - 2 syllables -> 2 steps -> 1. conditioning, etching ; 2. resin impreg)
Func primer
hydroPHILIC primer avoid collapse collagen in hybrid zone 3-7um
(face primer - avoid collapse collagen)
H2O vs denture fixing adhesion on glass
denture fixing > adhesion
How to change hydroPHILIC -> phobic
glass + oil -> bad wetting
How to change hydroPHOBIC -> philic
gold based alloy as solid surface
(No likes -> likes -> bribing w/ gold based alloy)
good wetting aka
capillary penetration
bad wetting aka
capillary depression
Ad amalgams
easy manipulation
low cost
long lasting
use amalgams
restoration pos teeth
core build up
class 5 restoration (molars)
Types amalgams
traditional: lathe cut, admixed, spherical
high copper (contemporary)
gallium alloys (replace Hg)
Steps form traditional lathe cut (minor component almalgam)
ingot (bar) -> cut by lathe cut machine -> particle
Composition ingot
mixture gamme + epsilon
gamma Ag3Sn - best physical properties
epsilon Cu3Sn
(gAmma -> Ag3Sn)
(ep ->. Cu -> Cu3Sn)
Traditional lathe cut particle size
> 30um
Traditional spherical amalgam steps formation
atomizing process: spray tiny drops molten ingot -> solidify innert gasseous (Ar)/ liquid envi (H2O)
Traditional spherical particle size
40-50um
(sphere > slice aka spherical > lathe cut)
Ad formation spherical almagam
less Hg need
less condensation pressure
High copper almagam composition
blend alloys - mech mixture (2/3 lathe cut + 1/3 spherical)
(high Cu aka high quality -> blend -> 2/3 lath + 1/3 spherical)
Chem background non gamma2 alma.
traditional
high Cu -> NO y2 phase (HIGH -> 2 -> NO y2)
Gallium alloy -> NO epsilon phase (ae - gAllium - Epsilon)
Cu + Sn»_space;> Sn+Hg
Effect almagam rxn high Cu
NO Sn2Hg (y2) -> NO weak link -> NO forms Sn-Hg rxn product -> form Cu6Sn5 (epsilon) at surface particles -> form rxn zone -> more stable
source Cu to form Cu6Sn5 from epsilon phase in single composition alloys
How to increase amount high Cu amalgam
adding Cu
How to make single composition
melt blend -> atomizing process (spherical)/ lathe cut alloy
Cu content of high Cu almalgam
30% by weight
Ad high Cu amalgam
less Hg
better marginal intergrity than traditional
(if have high Cu amalgam
-> less Hg
-> more honest -> integrity -> marginal integrity)
Admixed alloys improve to
increase clinical handling properties
Additives almagam
Palladium Pa -
economic reasons
improve corrosion Gallium alloy
Selenium Se-
improve biocompatibility
Indium In
admixed in large conc (10% by weight) -> reduce Hg vapor during mastication
(amalgam - imma add PaSeIn - Pa -> Ga -> gallium corrosion; Se: in crash landing on u -> biocompatibility ; In -> indeed a lot (large conc) -> reduce Hg vapor)
Gallium alloy comp
Ga + In + Sn
gallium + indium + tin (GalInTin)
Charac Gallium alloy
decrease melt temp Gallium < room temp
replace Hg from system
Contents powder Gallium
Ag
Sn
Cu
Pa
trace elements
(PASC - Gallium Powder -> GA -> PA -> PASC -> Pa, Ag, Sn, Cu + trace elements)
Components liquid Gallium
Ga
In
Sn - Tin
trace elements
(GaInTin - same as gallium component + trace element)
Setting rxn amalgam
Ag3Sn (y) + Hg -> Ag3Sn (y) + Ag2Hg3 (y1) + Sn2Hg (y2)
Which phase setting rxn amal. responsible for bad properties
y2 Sn2Hg
Effect setting rxn amalgam
Sn2Hg (y2) weak link -> corrosion ->
+ Cu (epsilon Cu6Sn5) -> improve physical properties (deform under static load)
+ Zn -> extend working time -> increase plasticity
(Cu - physical prop; Zn - last in alphabet -> plasticity)
Physical prop amalgam rules
(compress 80- creep 3- expansion, shrinkage 20)
ANSI/ADA rules:
1hr compressive strength 80MPA - highly early strength need to withstand dental finishing procedure, occlusal surfaces
min creep - <3% -> maintain marginal integrity
expansion/ shrinkage <20um -> prevent excessive marginal leakage
aka Knoop hardness, tensile strength
(compress 80- creep 3- expansion, shrinkage 20)
Physical prop compressive strength change
increase 1%Hg -> decrease 1% compressive strength
(more mercury less compressive)
Physical prop compressive strength amalgam
brittle (comp strength > tensile strength)
amal. unsupported/ Hg conc > (condensation process) -> tensile failure
Physical prop creep, flow def
constant load -> deform
creep charac
in oral temp b/c close to melting temp amal.
-> easy atomic diffusion -> deform under static load
wear resistance almal.
same magnitude tooth enamel (> pos composites)
Corrosion rxn
Cl attacks y2 phase
Sn7Hg + Cl + O2 +H2O-> Sn4(OH)6Cl2 + Hg
Corrosion rxn details
y2 Sn2Hg weak link ->
-weakens almal. aka tensile strength
- liberate Hg -> + uncreates y -> add. rxn products (y1+y2) -> Mercuroscopic expansion
Composite filler
inorg particles
Chem: quartz/ Silica (Ba,Al,Li) glass particles (Ba,Yb, Sr, Zr)
(Silical - SI - BaLi -> Ba, Al, Li)
(glass particles: BYSZ - Ba, Yb, Sr, Zr)
Shape composite
(synthetic) spherical
(grounded) irregular
fiber reinforced
Coupling agent def
bond btw filler particles - resin matrix
Resin matrix rxn explain
olygomers have common rxtive double bonds each end molecule -> add. poly with free radicals
TEGMA def
diluent molecule -> decrease viscosity
Types polymerization
Self cured
Light activated
Dual curing system
Product poly.
highly cross linked poly network
Def self cured type
benzoyl peroxide + 3rd amine
Def light activated
visible light appropriate wavelength + amine acceleartor -> (+) camphoroquinone
(camp - camphoroquinone - needs light)
Composite comp
2 paste system - jars (chem, dual cured poly.)
single paste system (light poly.)
initiator, acceleartor separated with chem activated system until mixing
etching jelly (phosphoric acid fro enamel)
bonding agents (increase adhesion composite-tooth)
name 2 pastes composite auto curing
universal
catalyst
Setting time chem activated
3-5min
Setting time chem activated depends on
conc. initiator, accelerator
Effect setting time chem activated
poly. -> 24h -> 25-45% double bonds uncreated
Setting time, depth cure (max 2mm/layer) light initiated depends on
intensity
penetration light beam
Effect setting time light initiated
poly. -> 10min -> 75% comlpete -> 24h -> 305 double bonds uncreated
disad photocuring - light initated process
poly. shrinkage
effect poly. shrinkage
stress on cavity walls ->
marginal gaps
2nd caries
failure restoration
postoperative pain
fracture tooth
microleakage (b/c opening restoration margins) - increment
recurrent carries (b/c opening restoration margins) - inlay
Resolution to opening restoration margins
inlay (fill cavity)
increment (fill microleakage)
Effect poly. shrinkage + hygroscopic expansion
cusp deflection
Shrinkage composite -> shrinkage stress -> post operative sensitivity
Thermal properties composite
low thermal conductivity - match enamel, dentin
thermal cycling -> poly shrinkage -> strain bond tooth-composite -> marginal gaps
Water sorption poly matrix effect
absorb H2O -> swelling composite
CAN’T counteract poly. shrinkage -> decrease hardness, wear resistance
uneven discoloration
incomplete poly -> increase solubility (uncreated HEMA, degrade products)
largest part dissolution occurs within first few hrs placement
Types colour stability
internal discoloration
external discoloration
Internal discoloration
in self curing system (b/c amine accelerators - brown) (camphoroquinone - yellow)
darkening, color shift -> yellow/ gray
External discoloration
coloring agents food
Mech properties composite
brittle (comp strength»_space;> tensile)
mech prop comp increase effect
increase filler content -> increase mech prop (comp strength)
Mech prop comp elasticity
< tooth structures
Modulus elasticity composite, dentin, enamel
composite: smallest
dentin: 19 GPa
enamel: 94 GPa
(elasticity CDE)
Types composites
- macrofiller (grinded glasses)
macrofillied composite
hybrid composite - microfiller (pyrogenic silica)
hybrid composite
homogenous microfilled composite
heterogenous microfilled composite - microfiller based complexes
heterogenous microfilled composite - nanofiller based
hybrid composite - nano hybrid composite
nanofilled composite
Steps apply composite
ready cavity -> acid etching -> H2O rinse -> dry -> + bond -> dry -> poly. bond -> apply material in small increments -> poly./ light cured -> final shaping, finishing, polishing
Main component resin based dental composite
inorg filler
resin matrix
coupling agent
Setting time range auto curing vs light curing
auto: min range 5min
light: sec range 10s
Colour, type setting rxn, ad, disad, comp, bonding amalgam
metallic/ grey
amalgamation
high compressive strength
long lasting
easy manipulation
discolour
Hg toxicity
ZACHS- Zn, Ag, Cu, Hg, Sn (Amalgam - A -> ZACHS)
NO bond, box form prep
Colour, type setting rxn, ad, disad, comp, bonding autocuring composite
tooth colour
free radical
aethetics
cheaper than light curing
air bubble inclusion -> porosity - O2 inhibition (auto -> I do it myself -> clumpsy -> air bubble inclusion)
shrinkage
2 pastes: base paste: co-initiator, resin, filler ; catalyst paste: initiator, resin, filler (au to -> 2 syllables 2 pastes)
chem bond
Colour, type setting rxn, ad, disad, comp, bonding light curing
add. poly
aesthetics
time saving
shrinkage
tooth sensitivity
expensive
need separate poly. unit
resin
filler (coupling agent)
photoinitiator
chem bond
what does dual cured composite mean
both self, auto curing
materials need for adhesive tech
bonding agent, etching jelly phosphoric
