DM Flashcards
(244 cards)
1
Q
Materials Categories
A
Metals
Ceramics
Polymers
Composites
2
Q
Polymer-Ceramic
A
Composite resin Glass-ionomer
3
Q
Metal-Ceramics
A
Metal-Ceramic Crowns
4
Q
Dental Materials characterize the______ of the material
A
Structure
5
Q
Dental materials ______ and ______ the Properties
A
Measure
Evaluate
6
Q
Dental materials some have…..
A
Many requirements for a given material
7
Q
Suboptimal Materials
A
Metals such as copper tin bronze and gold were used in the 3rd century
Egyptians used lead and papyrus for catheter devices
8
Q
What are Biomaterials
A
Materials used to construct artificial organs, rehabilitation devices, or prostheses and replace natural body tissues. Without causing ANY harm or negative reactions.
9
Q
Synthetic Biomaterials
A
Composites
Silicon impression materials
10
Q
Natural Biomaterials
A
Alginates
Hydrocolloids
11
Q
Tissues Engineered Biomaterials
A
Stem Cells
Replacement tissue —growing tissue
12
Q
Material Structure
A
Atomic Arrangments
Bonding
Composition
Defects
13
Q
Material Properties
A
Mechanical Physical Chemical Degradation Biologic
14
Q
Mechanical Concepts: Metals
A
Hard
Ductile-tough
Strong
15
Q
General Mechanical Concepts: Ceramics
A
Hard
Brittle
Strong
16
Q
General Mechanical Concepts: Polymers
A
Soft
Ductile -Tough
Weak
17
Q
_______ and ______ have high processing temperatures
A
Metals and ceramics
18
Q
________tend to have lower processing temperatures
A
Polymers
19
Q
________ tend to be used as direct processing materials
A
Polymers
20
Q
Metallic elements
A
Have 1,2,3 electrons in their outer shell
21
Q
Electrons in metals
A
Are key to metallic bonds
Loosely bound to nucleus
Have free mobility
- thermal and electrical conductivity
- ductility-bend without breaking
22
Q
Crystallization of Metal upon cooling
A
1) Molten-equally spaced
2) Nuclei begin grouping
3) crystal growth begins with more grouping
4) Formation of grains
23
Q
Metal Alloys
A
Mixture of 2 or more metals
- Cast metals for crowns
- Amalgams
Stronger less ductile
24
Q
Ductile
A
Atoms can slide
25
Strengthening Noble Metals
Must be made to resist deformation
Modified to impede dislocations
Au, Ag, Pd, Pt
26
Ceramic Bonds
Ionic and Covalent
| Both stronger than metallic
27
Ionic Bonds
Electron donor and electron acceptor
| Na+ Cl-
28
Covalent Bonds
Equally shared electrons
| Si-O
29
Covalent___Ionic
>
30
3 Most common Ceramics in Dentistry
3 Metallic Oxides
SiO2
Al2O3
K2O
31
Microstructure of Ceramics
Mixture of Metallic and non-metallic elements
| SiO4 (tetrahedron) is the building block
32
SiO4
Tetrahedron is the building block of ceramics
33
Most dental material ceramics are
Semicrystalline or polycrystalline
34
Crystalline
Long range order
| Crystalline silicate quartz or crystobilite
35
Noncrystalline
Short range order no long ranger
| Amorphous silicate glass
36
Dental Porcelain
SiO4 building block
Primarily a glass with some crystalline residuals
Processed by sintering or melting at high temps
37
Dental porcelain crystalline structure
Noncrystaline or amorphous silicate glass
Crystalline Silicates
-quartz or crystobilite
-Leucite (NOT lucite)
38
Polymer Bond Characteristics
```
Covalent Bonds
High molecular weight
Long molecules composed principally of nonmetallic elecments (CONH)
Polymers are entangled long chains
“Cooked spaghetti”
```
39
Where do polymer bonds derive strength and properties?
From the entanglement of “cooked spaghetti”
40
Polymerization Process (4 steps)
1 Light activation of initiator
2 Initiation of monomer
3 Propagation of Free Radical
4 Termination of Free Radical
41
4 Stages of Chain Reaction Polymerization
```
Activation
-free radical initiation
Initiation
-Free radical combination with monomer unit
-Double bond opening
Propagation
-Chain growth
-Volume decrease
-Shrinkage
```
42
Monomer Functional Groups
Monomethacrylates
| Dimethacrylates
43
Monomethacrylates
Linear Chains
44
Dimetharcylates
Branched and cross linked
45
Poylermization Reaction
Once reaction starts it can be very fast and generate lots of heat
MMA—
46
Why is Polymerization Important
Allows for in vivo processing-Direct placement
47
Direct Placement
```
Flowable material
Stable material
Trigger for setting
Rapid setting
Room temp setting reaction
```
48
Direct Vs Indirect Placement
Direct: Less prep, one visit. Don’t last
Indirect: Longevity of restorative. Multiple visits, expensive
49
Comparison of 3 Materials
Metals: Indirect
High processing temps
Except amalgam
Ceramics: Indirect
High processing temps
Except cements
Polymers: Direct
Low processing temps
Except Indirect composites
50
Uses of Polymers in Dentistry
Provisionals-Temporary Crowns-Linear
Adhesives-Crosslinked
Restorative-Crosslinked
Registration Materials-Impression Materials
51
Composites
Physical mixtures of metals ceramics and or polymers
Goal is to achieve some intermediate properties between the 2 material types. Rules of mixtures: dentin and enamel
52
Rules of MIxture
By knowing the phases present in the structure of any material and interfacial interactions. It is possible to predict the overall Properties fairly well
53
Dispersed phase
Glass Fillers
54
Matrix phase
Monomer resin
55
Dental Composite
Dispersed phase
Matrix phase
Fillers are chemically bonded to resin phase to improve properties
Photinitiators
56
Increase Filler Volume
Increases strenght modulus and viscosity
| Decreases shrinkage
57
Increase filler size
Increase surface roughness
58
Filler Types
```
Silicate glass (1-100 um)
Colloidal silica (.05 um)
```
75-80% wt
59
Material Properties
Physical (environment)
Chemical (bonding affected)
Biologic (Living tissue)
Mechanical(forces)
60
Materials Structure
```
Atomic Arrangement
-Crystalline (grains) vs non crystalline (glassy)
Bonding
-Primary(metallic, ionic, covalent)
-Secondary (hydrogen, van der Waals)
Composition
-Elements and phases
Defects
-Macroscopic (pores)
-Atomic Scale (microflaws)
```
61
Reversible Interactions with the Environment
```
Mass Properties
Thermal Properties
Electrical Properties
Optical Properties
Surface Properties
```
62
Density
= weight/ unit volume
Metals 6-18 g/cm3
Ceramics 2-6 g/cm3
Polymers .8-1.2 g/cm3
63
Specific Gravity
=relative density=density of material/density of water
Density of water = 1 g/cm3
Material with specific gravity of 1.2 has a density of 1.2 g/cm3
64
Thermal Expansion
Most things expand when heated contract when cooled
65
Heat Flow
Teeth are insulators due to high mineral content
Pulp can withstand small temp changes for short times. restricted circulation of pulp cannot dissipate heat and carry it away
Metals have high thermal conductivity so they need thermal insulator like base composites do not
66
Electrical Properites
Metallic restorations conduct electicity
Composites and ceramics are electrical insulators
Significance:
Corrosion of metal
Galvanic reactions
67
Optical Properites
Color
Translucency
Gloss
Surface texture
68
Color Has 3 Dimensions
Hue
Value
Chroma
69
Hue
wavelength
| Color ROY G BIV
70
Value
Intensity
| Brightness
71
Chroma
Purity
| Density or concentration
72
Metamerism
2 objects that appear the same color under one light source and different under another light source
73
Goals of Dental Material
Patient satisfaction
- Esthetics
- Functions
- Longevity
74
Limitations
All Models have limitations
- Cannot know everything about a given material or system
- Have to choose parameters
75
Contact Angle
Measures how a liquid interacts with a solid
Good wetting close to 0
Poor wetting close to 180
76
Good Wetting
Low contact angle close to 0
77
Poor wetting
High contact angle close to 180
78
Hydrophilic vs. Hydrophobic
Can help determine the wetting properties of a material
Molecules can have both components
79
Hydrophilic primers
Allow penetration into areas with with water
Have low viscosity
Allow for attachment to composite
80
Sealants
Unrolled diluted resins
Self or light cured
Clear or opaque
Radio Plaque
81
Wetting can be anticipated on the basis of______?
Hydrophobicity and hydrophilicty
82
Hydrophilic Primers are usually mixed with
A solvent usually alcohol or acetone
83
Hydrophilic chemicals will Wet _________surfaces
Hydrophilic
Like associates with like
84
Surface Wetting
Important anytime two different materials come into contact
Important in impression materials
Important in adhesives
Important in bacterial adhesion
85
Chemical Properties
Chemical properties of a material are those that involve changes in the primary and secondary bonding of the material
86
Primary bonding
Generally affected by chemical and electrochemical reactions
87
Secondary Bonding
Generally affected by processes such as adsorption and absorption
88
Corrosion
The spontaneous destructive oxidation of metals
All metals corroded in our atmosphere spontaneously except
89
All metals corroded in our atmosphere spontaneously except
Gold
Platinum
Palladium
90
Amalgam filling turn
Black over time
91
____ alloys designed to minimize corrosion
Gold
92
Metal Corrosion: Active
Lead to destruction
| Gamma 2
93
Metal Corrosion: Passive
Produce corrosion film that prevents further corrosion (titanium implants)
94
Metal Corrosion: Immune
Noble metals (gold)
95
Electrochemical Corrosion
Active
An anode-Corroding Metal
Cathode-Different metal
A conducting environment for ionic movement
An electrical connection between anode and cathode for the flow of electron current
In amalgam anode and cathode are the 2 phases
96
Types of Corrosion
Galvanic
crevice
Structure selective
Stress
97
Chemical Dissolution
Normally occurs through dissolution of oxides created by hydrogen bonding effects of water in local areas of high acidity
98
Absorption of water into polymers
Secondary bonds
| Dimensional changes
99
Hydrologic degration and relapses of componenents (polymers)
Water enzymes bacterial byproducts
Contributes to wear problem with composites
100
Biological properties
Are interrelated with degradation properties, polymerization process, and are dynamic
101
Mechanical Properites
Describe how a material responds to loads (forces)
102
Single Dimension Force
Compression
Tension
Shear
103
Combination forces
Torsion
Flexion
Diametric compression
104
Mechanical Events are
Time and temperature dependent
105
Hardness
Relative measure of plastic deformation.
Indent with a load and measure size of indentation
106
Fracture Toughness
Measures a materials resistance to crack propagation
Has high clinical correlation to clinical wear data (composites)
107
Creep
Deformation over time in response to low constant stress
108
Stress Relaxation
Deformation over time in response to low constant strain
109
Biomechanics of Tooth Structure
Teeth are not rigid
When teeth are subject to chewing forces they undergo subclinical movements
110
what leads to microfractures
Cyclic tension and compression of enamel rods
111
Abfractions usually associated with
Heavy wear facets
112
Single cycle overload
Unexpectedly bit on cherry pit or bone rare
113
Fatigue fracture
Cyclic loads well below breaking load
| I was eating something soft-more common
114
Amalgams
Easy to place
Excellent Clinical outcomes
Poor esthetics
115
Ceramics
Good esthetics
Excellent clinical outcomes
More difficult to process
116
Composite Resins
Esthetic Direct restorative
Cured by visible light
Primary benefit is the combination of esthetics and ease of placement
Moderate clinical outcomes
117
Composite
Hybrid material of an organic phase(resin) and an inorganic (filler) phase
118
Why use composites
Teeth are composites
And Anat ages of Both organic and inorganic components
Easily processed and handled allows for direct restorations
119
Galvanic Corrosion
One metal acts as an anode and another acts as cathode
120
Structure Selective Corrosion
One phase of an amalgam and another phase
121
Crevice Corrosion
The tip of a crack in a preparation; surface of prep
122
Stress corrosion
Stressed portion; unstressed regions
123
Ceramics Hydrolysis
Via Chemical dissolution-normally occurs through dissolution of oxides
Ex. Acid dissolves HA
124
Polymer Hydrolysis
Via absorption of water into polymers
Via Hydrolysic degradation and release of polymer components
125
Stress Strain Curve
(Know different regions of curve)
Elastic Region
Plastic Region
Ultimate Strenght
126
Elastic Region
Straight region of the curve
Strain is reversible
127
Plastic Region
Line starts to curve strain is permanent
128
Ultimate Strength Region
Highest point of the curve; point at which the material fail
129
Stiff and Brittle Curve
High modulus (steep slope)
Small plastic region
Small area under curve-absorbs a relatively small amount of energy
130
Stiff and Ductile
High modulus (steep slope)
Larger plastic region-can handle a fair amount of permanent deformation before failing
Large area under Curve-can absorb a fair amount of energy
131
Flexible and Ductile
Low modulus
Plastic Region that continues past ultimate strength pint-can deform past point of failure before failing completely
Large area under curve-can absorb a fair amount of energy
132
Modulus and toughness
Slope of the straight position of the modulus of elasticity
Steeper=stiffer
Gradual=more elastic
133
Reduce a materials modulus of elasticity; decreases_______ and increases __________
Stiffness
Flexibility
134
Fatigue
The weakening of a material caused by repeat early applied loads
135
Fracture Toughness
Measures a materials resistance to crack propagation
136
Abfractions
Non-curious tooth tissue loss around the gingival margin
137
Buccal-Lingual Stability
Want to prep tooth such that Buccal-Lingual cusps can all withstand required biting/chewing forces
138
BisGMA-TEGDMA
Most common system
| Allow for relative ease of processing-flows well when unpolymerized
139
BisGMA
Methacrylate
| Structural component-provides physical properties for polymer
140
TEGDMA
Dimethacrylate
Dilute the-used in 30-50% wt
Forms cross links between chains
141
Composite Fillers
Silica or zirconia based inorganics
142
Different composite filler sizes
Higher, Smaller, Micron, nano, Nano in polymer matrix
143
High Filler
Loading results in a higher modulus
144
Smaller Filler
Better
Matches tooth structure
Have better wear properties
Allow for better polishing and finishing
Better mechanical properties
145
Nano Filler
Microfine
Has a lower modulus but increased surface area results in better wear resistance
146
Nano filler in polymer matrix
Microfine fillers polymerized in matrix
Poorer filler to matrix bonding-no coupling agent
147
Coupling Agent
Adds methacrylate groups that can bond with polymer chains
Forms very strong bonds between filler and resin
148
Resin helps ______ and_____
Processing and handling
149
Filler helps______ and ______
Modulus and wear resistance
150
More filler will result in:
Increased Strenght & resistance
Reduce Shrinkage during curing
But will increase viscosity and brittleness
151
More resin will:
Increase toughness flow ability and improve processing
Decrease strength and wear resistance
152
What does Curing do?
Induces polymerization of resin
153
Visible Light Cure
Ease of use of resins. Allows for a longer working time
154
Cross linking
Formation of bonds between polymer chains within a resin
155
How crosslinking controls properties
Improves Strenght of material
More crosslinking leads to more resilient material
156
3 types of curing
Chemical Mixing
Heat
Light Cure
157
Chemical mixing cure
Working time is operator dependent
| Can be done chair side
158
Heat Curing
Consistent high temperature
| Not good in vivo
159
Light Cure
Cure ion command
| Good in vivo
160
What portion of composite will shrink upon polymerization?
Resin matrix portion
161
Consequences of shrinkage
Stress on tooth structure
| Can cause micro leaks and lead to secondary caries
162
Acidic polymer in aqueous solution
Poly acrylic acids
163
Basic glass (powder)
Aluminaflurosilicate glass
164
Glass ionomer curing reaction
Cured by acid base reaction
Not all glass is consumed by reaction
Salt bridges form crosslinage and are made from polyacid and glass
165
Water based restorative
Good adhesion to tooth structure (hydophilicyt)
Primarily bonds to tooth structure chemically
Bonds better with enamel than with dentin
166
Process of Application\
Place liner on dentin to clean the smear layer and leave smear plugs
Apply GI mix
Polyacid matrix dissolve periphery of glass
Glass release calcium alummninum fluroide
167
Resin modified glass ionomer
Hybrid of GI and composite resin
Both VLC and acid base curing
Increased mechanical properties of GI
168
Composite Initiation
Free Radicals initiate methacrylate polymerization
| -visble light initiator
169
Adhesives are based on the composite resin chemistry
Contains acidic groups to promote bonding
Dimethacrylate are visible light cured
170
_______ promote bonding
Hydrophilic modifiers
171
_______ and ______ are needed for bonding
Hydrophilic and hydrophobic Properites
172
Tooth structure are________, composites are________ and adhesive layers are both
Hydrophilic
Hydrophobic
173
Adhesive Failure
Failure between composite and adhesive
174
Cohesive Failure
Failure in the adhesive section only
175
Structural failure
Failure in the Dentin portion only
176
Smear Layer
Consisted of ground collagen and HA
177
Sealants
Designed to flow well and seal Noncavitated tooth surface to prevent decay
178
Etching
Necessary to create micro racks in the enamel to add surfaced area
179
Sealants have fillers
0-10%
180
Oxygen inhibition layer
Atmospheric layer of sealant does not solidify well due to oxygen
181
Impression Molds
Used to make a negative mold of dental structures
182
Hydrocolloid
Alginate
Agar-agar
Bot are hydrophilic and wets the tooth structure and gypsum
Immediate pouring of impression in stone should occur due to ability of hydrocolloids to gain or lose water
183
Alginate
Irreversible chemical reaction
Material is elastic and used in stock tray for primary impression and final impression for complete dentures
184
Factors that affect alginate setting time/rxn rate
Temperature
Liquid/powder ratio
Particle size
Mixing rate
185
Alginate is NOT used for
Crown and bridge impressions due to lack of accuracy
186
Agar-Agar
Reversible physical reaction -Temp
Material is elastic and used in special stock trays to make 2ry impressions for fixed restoration (inlay onlay crown and bridges)
Low tear strenght due to high water content(will tear easier)
187
Viscoelasticity
Upon placing impression tray with material on teeth the material will immediately strain and on removal of impression tray with material the material will be permanently strained and no recovery of original shape
188
Plain Elastic
Would deform under stress but return to shape following removal of stress
189
Plain Viscous
Would defor very gradually with stress and would provide resistance to initial stress and initial deformation
190
When taking impressions
- Let the material set
- Don’t exert over pressure on tray after insertion
- Use rapid snap removal of imporession with long axis of teeth to decrease unwanted deformation and prevent tearing
191
Classification of Impression materials 3 types by physical condition after setting
Rigid
- Zoe
- Plaster
Plastic
- Wax
- Compound
Visco(elastic)
- Hydrocolloids
- Elastomers
192
Alginate acid dissolved in ______
Water
193
Alginates are temperature controlled______and chemically controlled_______
Reversible
Irreversible
194
How can Alginates be manipulated
Water to powder ratio
195
Alginate lower water to powder ratio
Increases strenght tear resistance and consistency
Decreases working and setting time and flexibility
196
Alginates have ______ crosslinks
Calcium
197
Advantage of Alginate
Surface energy- wets tooth structure and gypsum stone well
Quick setting
Easy to use
198
Disadvantage of alginate
Poor dimensional stability
-Synereis
Imbition
199
Syneresis
In a dry environment will lose water over time leading to shrinkage and deformation
200
Imbibition
In wet environment will gain water and expand
201
Polysulfides: impression material
Conform well to a prepared tooth, resulting in good surface detail and are oxidize by lead dioxide or copper hydroxide to form a polysulfide rubber with a water condensate
202
Polysulfides :Low molecular weight_______ containing reactive _______groups
Oligmer
Metacarpan
203
Advantage of Polysulfidle impression
```
Low shrinkage
Very little expense
Good actuary and stability
Material retained well in tray well
Can add layers to old layers
```
204
Disadvantages of Polysulfides
Can stain brown
Odorous
Sets slows
Must be poured within 1 hour after impression
205
Polysiloxanes
Inherently hydrophobic
Excellent accuracy
Good chemical dimensional stability
206
Polysiloxanes advantages
```
More stable than alginate and polysulfides
Can repour
Greatly accuracy
No staining
No odor
Paste system easing mixing
Various viscosity
```
207
Polysiloxanes disadvantages
Difficult for operator to vary setting time
EXPENSIVE
Can produce bubbles in final cast due to hydrogen
208
Polyethers
Low molecular weight polyether oligomer with terminal ethylene I mine reactive ring groups will react with aromatic sulfonic ester by dual ring opening with resultant polymer being cross linked
209
Polyethers advantages
Great stability
Slightly hydrophilic
Adhesives work well
Fast setting time
210
Polyethers Disadvantages
Extremely stiff-tough to remove from undercuts
Low tear strenght-tears easy
Slightly hydrophobic
Bad taste
Can cause hypersensitivity in some patients
211
Gypsum
Dental plaster and stone to make casts
212
Mineral gypsum is the _____ form of _______
| Found in a compact mass in nature
Dehydrate
Calcium sulfate
213
Calcination
Part of the water is driven off to form calcium sulfate-hemihydrate
214
Water cured
When dental stone is mixed with water the reverse reaction takes place (calcination)
Hemihydrate coverted back to hydrate
Heat is released exothermic
215
Gypsum crystals grow and interlock during setting, why?
Interlocking contributes to Strength and dimensional change of gypsum
Properties can be altered by manipulating growth of dehydrate crystals
216
Types of Gypsum
Dental Plaster
Dental Stone
217
Dental Plaster: Type I
Impression plaster
218
Dental Plaster: Type II
Model plaster
219
Dental ______ is weaker than dental _____ due to porous particles that require more water and ______
Plaster
Ston
Irregular crystal shape
220
Dental Stone: Type III
Dental stone quickstone
221
Dental Stone: Type IV
High strenght dental stone (silky rocky)
Used for inlays crowns bridges casts
222
Dental Stone: Type V
High strenght high expansion stone
Used for polyethers or polyvinyl impressions
Composed of alpha form of hemidhyrdate crystals
223
Principal difference between plaster and stone
Shape and form of hemihydrate crystals
224
If gypsum is place in water
It can dissolve
225
Dental stone used for models not plaster
High crushing strength
| Better abrasion resistance
226
Denture base
Triad
Machine is a visble light curing machine that cures the triad material. Used to make custom accurate stable trays
227
Denture base need for difference in composition
Differences in composition provide differences in mechanical characteristics of the tray
Fillers provide hardness and rigidity to the tray
228
TRIAD and TRIM and JET use same baseline material
Polmethylmethacrylate
229
Which is strongest and why TRIAD TRIM JET
TRIAD due to dimethylmethylacrylate crosslinkage
230
Mouthguard
```
Designed to absorb impact
High toughness low rigidity
Thermoplastic materials (not thermoset)
```
231
Cements
Used to bind restorations or appliances to tooth structure
232
Requirements for cements
Low viscosity but good mechanical Properites
233
Water Based Cements
Glass ionomer
Resin modified glass ionomer
Zinc phosphate
Zinc polyarcylate
234
Resin Based cements
Composites
| Compomers
235
Oil Based Cements
Zinc oxide eugenol
236
Base and Liners functions
To protect pulp and minimize post op sensitivity
- Act as thermal and chemical barrier
- Control inflammation of pulp
- Control fluid movement
237
Bases
Provide thermal protection for pulp
| Supplement mechanical support for the restoration by distributing local stresses
238
Liners
Thin layer of material used to protect dentin
239
Calcium Hydroxide
Pulp capping
- insulator
- Stimulates reparative dentin
- Rleases hydroxide ions
- At low ion concentrations - stimulates odontoblasts
240
ZOE
Pain reduction
Dulls pulpal pain
Limits free radical formation-cannot put composite on top of ZOE because it will limits polymerization
241
Waxes
Should melt at lower temperatures
Should be carvable
Must be able to be burned off
Must be dimensionally stable
242
Hexane
Volatile liquid
243
Candle Wax
Typical semi-solid Wax
244
Poly-ethylene
Plastic
