Lecture 8 Flashcards
1
Q
Adhesive joint:
A
A layer of intermediate material (adhesive) with 2 surfaces (adherends) producing 2 adhesive interfaces
2
Q
Tooth structure is generally hydro–
A
hydrophilic
3
Q
composite is generally hydro–
A
hydrophobic
4
Q
2 adhesive interfaces:
A
adhesive and composite, adhesive and tooth structure
5
Q
Year acid etch was put into use, and by whom?
A
1955, Michael Buonocore
6
Q
Ray Bowen discovered what, in what year?
A
Bis-GMA 1962
7
Q
To understand the principles of adhesions we must talk about these parameters:
A
Substrate, adhesive system, mech of adhesion, clinical techniques
8
Q
Enamel is hydro (philic/phobic) compared to composite
A
hydrophilic, bc of the water content
9
Q
Enamel is hydro (philic/phobic) compared to dentin:
A
hydrophobic
10
Q
Enamel is __% mineral by weight, __ % organic, and ___ % water.
A
95, 4, 1
11
Q
What kind of shapes form enamel?
A
prisms
12
Q
How many hyrdoxyapetite crystal form a prism of approx. 5-7 microns?
A
10,000
13
Q
Comp of dentin:
A
70% inorganic, 20% organic (collagen), 10% water
14
Q
What type of substrate is dentin?
A
dynamic substrate, subject to constant physiologic and pathologic changes in composition and microstructure
15
Q
How does the dentin change with age?
A
the relative conc of organic vs. inorganic content, happens with repetitive trauma as well
16
Q
Characteristics of dentin as a substrate:
A
permeable, wet, heterogenous, tubular, mineralized, collagen reinforced with inter and intra-fibrillar apatite
17
Q
Dentinal tubules contain:
A
odontoblasts (1/3 into tubules), fluids, nerve fibers, other molecules in the intracellular matrix
18
Q
2 types of dentin:
A
peritubular and intertubular
19
Q
Peritubular dentin:
A
more mineralized than intertubular, lining of tubule, little organic matrix
20
Q
intertubular:
A
rich in collagen fibers, ideal for hybridization, bulk of dentin
21
Q
Adhesion to tooth structure is primarily:
A
micromechanical
22
Q
T or F? Current adhesive system only employ bonding to hydrophilic substrates.
A
F. both hydrophilic and phobic
23
Q
Adhesives used to be classified according to:
A
time of appearance into market: generation 1-7
24
Q
Current classification of adhesives:
A
steps and adhesive strategy (1,2, or 3 steps)/ (etch-and-rinse, self-etch)
25
2 types of adhesive strategies:
etch-and-rinse AND self-etch
26
3 steps of dentin/enamel bonding:
etch, primer, adhesive
27
etch step is aka:
conditioner (typically acid)
28
Fxn of etch step:
cleans/preps surface, removes smear layer and mineral
29
What is primer?
amphipathic monomers + solvent carrier (has both hydrophilic and phobic carriers), connects philic and phobic
30
Fxn of primer:
infiltrates exposed collagen network, displaces moisture and links to hydrophobic adhesives
31
Adhesives are:
hydrophobic resin monomers
32
Fxn of adhesive:
link to resin composite
33
Most resin systems are based on:
high molecular weight hydrophobic monomers (UDMA, Bis-GMA)
34
The only true chemical bonding occurs with:
glass ionomers
35
What is the base for self-etching adhesives?
phosphate based acidic primers
36
How many steps are etch-and-rinse systems applied in?
either 3 or 2 (2: conditioner, then primer + adhesive, i.e. optibond solo plus)
37
How many steps are self-etching systems applied in?
either 2 or 1 (2: etch + primer no rinse, then adhesive), (1: all 3 in one bottle, shelf life and sensitivity make it undesirable)
38
How many steps are glass ionomer systems applied in?
2
39
What is the smear layer?
mineralization
40
What are you left with when you remove the smear layer?
demineralized dentin
41
What are you bringing into the interface when you add the primer and adhesive?
monomers
42
What does the final hybrid layer consist of?
Collagen + adhesive monomers
43
Fxn of etching:
to achieve adhesion to the restorative resin (i.e. acids, lasers, air abrasion), remove smear layer and open dentinal tubules, increase surface area of the enamel and create micro-porosities
44
With what systems is etching required?
All
45
ideal etch enamel:
phosphoric aced
46
How long to leave etchant on tooth:
15-20 sec depending on the acid pH and the substrate
47
Who was the first to talk about etchant?
Buonocore
48
T or F? Phosphoric acid is an organic acid.
F. inorganic
49
2 types of inorganic acid etches:
nitric acid, phosphoric acid
50
2 types of organic acid etches:
citric acid, malice acid (10% for either)
51
Acid-etch technique is aka:
hypertonic acids
52
How do different acids differ in terms of how they etch?
Leave different pattern in the tooth structure (circular holes for 37% phosphoric acid)
53
Effect of acid etch procedure depend on:
type of acid, conc (32-37), pH, (0.8-1.2%), etching time (10 vs 20s), form of etchant (gel vs. aqueous delivery system), rinse time (slightly longer than instructions, past when blue is gone), method of application, whether the enamel is instrumented prior, chemical composition and condition of enamel
54
active application:
rubbing with microbrush
55
Why is rubbing with a micro brush required with gel etchants?
to achieve better etching patterns
56
Different methods of application of etchant:
rubbing, agitation, and/or repeated application of fresh acid
57
Examples of how the condition of enamel can vary:
primary or permanent teeth, prism-strucuture or prismless, fluoridated, demineralized
58
Enamel etching
remove orgainic matieral, inc s.a, high bond stength, predictable bonding, about 20 MPa
59
Dentin etching
remove smear later, open tubules, remove mineral, inc s.a., create loose collagen network (5-10 microns in depth), variable substrate, less predictable bonding
60
Why is it important not to leave etchant longer than 15 sec on dentin?
leads to greater depth of demineralization, worse adhesion, we want 5-10 microns in depth
61
Prevent application technique for etchant depends upon:
type of dentin, i.e. superficial vs. deep dentin, young vs. old (more tertiary and reparative dentin)
62
high bond strength
20 MPa+
63
T or F. In todays adhesive systems the bonding to dentin is less predictable than to enamel.
F. Not if you follow instructions
64
Appearance of etched enamel:
chalky (not true for dentin)
65
Deep vs superficial dentin:
Deep: large tubules, closer spaced, more peritubular dentin (66%) than interlobular (12%), lower bond strength
66
T or F? Peritubular is less ideal for bonding than intertubular dentin.
T
67
Superficial dentin:
small tubules, (0.8um at DEJ), space further apart, PD (3%)/ ID (96%), higher bond strength
68
Which is more ideal for bonding, peritubular or interlobular dentin?
intertubular
69
T or F? Primers are required in both dentin and enamel.
F. Dentin only
70
Fxn of primer:
adhesion promoter, increases surface tension of the collagen
71
Is adhesive resin hydrophobic or hydrophilic?
hydrophobic
72
What would happen if we accidentally used primer on enamel?
Nothing
73
What type of monomers does primer contain?
bifunctional monomer (HEMA) dissolve in solvents (acetone, ethanol, and/or water)
74
What solvents are primers dissolved in?
acetone, ethanol, and/or water
75
Are the solvents of primers volatile?
Yes
76
From where does the primer displace water?
the dentin surface and the moist collagen network
77
How does water displacement aid in adhesion?
promotes infiltration of monomers through the nano spaces of the exposed collagen network.
78
What does wetting the surface do?
increases the surface tension
79
What are bifunctional monomers:
HEMA dissolved in solvents
80
Is the adhesive filler or unfilled resin?
either
81
RBC aka:
resin composites
82
T or F? most adhesives are filled.
F. unfilled. those that are filled have very little
83
T or F? Bonding is chemical.
F. micromechanical
84
Fxn of adhesive resin;
stabilize hybrid layer and forms resin tags
85
What are formed when resin monomers penetrate micro-porosities created by etching?
tag-like resin extensions
86
How are the tag-like extension connected?
micro-mechanically interlocked with partially demineralized enamel (entangled w the enamel)
87
hydrophobic, more viscous adhesive resins:
Bis-GMA, UDMA
88
higher hydrophilicity, less viscosity adhesive resins:
TEG-DMA, HEMA (as a wetting agent)
89
2 types of monomer used to make adhesive resins:
hydrophobic and higher hydrophilicity monomers
90
What happens to the collagen fibers when they are dried?
they collapse
91
Why do the collagen fibers collapse when they are dried?
bc it is supported b inorganic material, demineralization causes the collapse
92
What type fo bonding in requried for adhesion to dentin?
wet bonding
93
Fxn of wetting:
to get the collagen fibers to raise again
94
Composition of demineralized dentin:
70% resin, 30% collagen
95
What forms the hybrid layer?
the infiltration of the demineralized dentin layer by resin monomer
96
Composition of dentin before etching:
50% inorganic mineral, 30% organic, 20% water
97
T or F. The mineral and water are pretty much gone after etching.
T
98
Layers of the hybrid layer:
composite resin, adhesive resin, dentin
99
What is the hybrid zone made of?
adhesive resin and collagen fibrils, and partially demineralized dentin
100
Resin tags are aka:
microtags (lateral branches) or macrotags (larger ones)
101
Fxn of acid:
remove inorganic phase and expose rods and collagen
102
What promotes the effective link bw hydrophilic substrate and hydrophobic resin?
bi-functional monomers
103
What raises collapsed dentin?
primer
104
What is responsible for wetting the collagen?
primers
105
The solvents in the primer acts as:
water chaser
106
Which is more hydrophilic, dentin or enamel?
dentin
107
Fxn of resin:
penetrates collagen matrix, interlocks collagen, forms hybrid layer
108
T or F? Etchant can be used on both enamel and dentin.
T
109
How far past the margins do we apply the etchant?
1mm beyond
110
Why do we apply etchant 1mm beyond the margins of the prep?
bc there is a bevel
111
Excess etching leads to:
further decalcification/ demineralization, area at bottom of hybrid layer that is weak, decreasing longevity of restoration
112
T or F? The over-etching of enamel would be critical.
F
113
After etching the surface should appear:
damp
114
Challenge when bonding:
working with 2 different tissues, enamel must be dry, dentin must be slightly damp
115
How to dampen detntin if we dried to much:
damp microbrush
116
T or F? Primer requires only 1 coat.
F. Multiple
117
The suface should appear ___ after solvent evaporation.
shiny
118
Goal of air-drying primer vs adhesive
evaporate solvent vs. thin, even layer
119
What are we doing if we over dry at the solvent evaporation stage:
collapsing the collagen mesh
120
When does the adhesive work best?
in thin, even layers
121
Which step do we go back to if contamination occurs at any step?
etching
122
What type of adhesive system do we use?
2 step etch and rinse system, ethanol solvent, 15% filled (adhesive a little more viscous) with 0=.4 icon barium glass filler (reinforces hybrid zone and penetrates dentin tubule), can be bottle or unidose
123
What do the 2 steps of Optioned Solo Plus consist of
etching + primer/adhesive
124
Ethanol based systems work best in:
fewer coatings
125
Acetone based systems work best in:
multiple layers
126
When should we use the less preferred, indirect vision?
when direct vision would result in improper operator positioning
127
The center of focus on the hand mirror should be:
the bur contacting the tooth
128
What should you do before using indirect vision?
check orientation of handpiece and bur relative to tooth with direct vision.
129
With which visual field should you be monitoring the positioning of the handpiece during the prep?
both central and peripheral
130
Pt of origin of Class III caries:
interproximal enamel, generally gingival to the contact pt
131
Acid etch allows for:
Selective demineralization of enamel
