Quiz 2 Flashcards
1
Q
What are caries?
A
infectious microbial disease that results in localized destruction of calcified structures of teeth
2
Q
What are the three primary etiologic factors of caries?
A
-
Agent
- Acid producing bacteria - pH 5.5
-
Environment
- Carbohydrate rich diet
-
Host
- Susceptible tooth structure
3
Q
Besides Agent, Environment and host etiological factors for caries. What are other additional etiologic factors?
A
-
Time:
- Demineralization (and subsequent cavitation) and remineralization
- can be stopped or reversed
-
Fluoride:
- In solution - can facilitate the arrest of lesion or aid in remineralization (“repair”
-
Saliva:
- Protective mechanism
- Promote bacterial clearance
- Direct antimicrobial activity
- Capacity as a buffer
- Remineralization
- Saliva can dramatically alter the oral ecosystem
- Lower salivary quality and or quantity (xerostomia=dry mouth) typically have increased caries rate
- Protective mechanism
- Social and demographic factors
4
Q
Explain the salivary protective mechanisms against caries
A
Protective mechanism
- Promote bacterial clearance
- Direct antimicrobial activity
- Capacity as a buffer
- Remineralization
Saliva can dramatically alter the oral ecosystem
Lower salivary quality and or quantity (xerostomia=dry mouth) typically have increased caries rate
5
Q
What is the primary organism in caries initiation for enamel lesions and operates in concert with Actinomyces to initiate root surface lesions
**Also this organism is still regarded as the primary organism in root caries initiation
A
Streptococcus Mutans
Because they produce substances with which they can readily adhere to the tooth
6
Q
What organism flourishes in a carious environment and contributes to caries progression
A
Lactobacillus Acidophilus
Because they are good acid producers and are acid loving
7
Q
What are the common sites of origin for caries?
A
-
Pit and Fissure enamel surfaces
- Most likely to exhibit signs caries due to surface irregularities
- Area can harbor plaque
- Most likely to exhibit signs caries due to surface irregularities
-
Smooth enamel surfaces
-
Proximal surfaces have a higher incidence than other smooth surfaces
- Nonself-cleaning areas
-
Proximal surfaces have a higher incidence than other smooth surfaces
-
Root surfaces
- Most susceptible surface to the carious process
- Typically requires recession of gingival tissue (surface exposure)
8
Q
What are the common methods for overall Caries detection?
A
Teeth must (should) be both clean and dry for clinical detection
(Remove saliva and improved visibility of incipient lesion)
Radiographs: Proximal, Occlusal and Secondary/recurrent
9
Q
What are the best ways for pit and fissure lesion caries detection?
A
visual inspection (best method)
BW radiographs
Tactile examination (explorer)
10
Q
What are the best ways for Proximal surface lesion caries detection?
A
Bw radiograph (most accurate in posterior teeth)
Anterior teeth (periapical radiograph, fiber optic transilumination)
11
Q
What are the best ways forSmooth surface lesion caries detection?
A
Generally can be visually inspected
12
Q
What are other detection methods for caries other than visual inspection, radiographs and exploring?
A
Optical
Using a light to determine tooth structure destruction
Can get “false positives” due to stain or calculus
13
Q
Who was the father of modern dentistry that developed a caries classification system based on anatomical areas involved and associated type of treatment that we still use today?
A
G.V. Black
14
Q
What classification regards caries that affects the pit and fissure, on occlusal, buccal, and lingual surfaces of posterior teeth and lingual of anterior teeth?
A
Class I
15
Q
What is the classification regarding caries that affect proximal surfaces of molars and premolars (posterior only)
A
Class II
16
Q
What is the classification regarding caries that affect proximal surfaces of central incisors, lateral incisors and cuspids not involving the incisal edge
A
Class III
17
Q
What is the classification regarding caries that affects the proximal including incisal edge of anterior teeth
A
Class IV
18
Q
What is the classification regarding caries that affect gingival 1/3 of facial or lingual surfaces of anterior and posterior teeth
A
Class V
19
Q
What is the classification regarding caries that affect cusp tips of molars, premolars and cuspids (posterior or anterior canines)
A
Class VI
Infrequent, but do see it sometimes
20
Q
What is the classification system regarding the number of surfaces involved?
A
simple = 1 surface
Compound = 2 surfaces
Complex = > 3 surfaces
21
Q
What are the type of surfaces involved classification system
A
smooth surface = sides of teeth
Pit and fissure = occlusal surfaced, grooves and pits
22
Q
What is the definition of tooth preparation
A
The mechanical alteration of a tooth to receive a restorative material which will return the tooth to proper form, function, and esthetics
Achieving proper outline form for any tooth preparation significantly increases restoration longevity
23
Q
What are the types of walls in cavity preparation and where are they located
A
- external = outer tooth surface
- internal = inside cavity prep
24
Q
What a mesial, buccal, distal or lingual wall is missing what replaces it?
A
When a mesial, buccal, distal or lingual wall is missing, a gingival wall (floor or seat) replaces it
25
When would the terminology "FLOOR OR SEAT" be used in a cavity preparation
In a horizontal plane
**Pulpal** (floor) - class I usually
**gingival** - class II, III, IV, V only
26
What type of class preparation is the following?
Class I preparation
pit/fissure prep
27
What type of class preparation is this cavity restoration?
Class V
gingival 1/3
28
Explain the types of external walls in a cavity preparation
***_Buccal_***
***_Distal_***
***_Mesial_***
***_Lingual_***
_***\*\*Gingival***_ (if one of the above walls is missing - same as the floor)
29
Explain the types of internal walls in a cavity preparation
***_Axial_*** - parallels long axis, vertical plane of tooth adjacent to pulp
***_Pulpal_*** - perpendicular to the long axis of the tooth closest to the pulp in horizontal plane
30
What is the junction of two walls called?
Line angle
31
What is the junction of three walls called?
point angle
32
What is the junction of a cavity wall and the external tooth surface called?
Margin
33
What is the angle of the tooth structure formed by the junction of a prepared wall and the external surface of the tooth called (alternate name)
cavosurface angle
34
What is the process of placing the cavity margins (cavosurface) in the position on a tooth they will occupy in the completed preparation
***_Outline form_***
Should be visualized before any tooth reduction occurs
"measure twice, cut once"
35
What are the major factors that influence outline form
1. ***_Location of the carious lesion_***
2. ***_Size of the carious lesion_***
1. Primary determinant = lateral spread to dentin layer occurs very quickly
3. ***_Tooth anatomy_***
1. ex. pit, fissures, developmental defects, decalcified areas
4. ***_Type of restorative material_***
5. ***_Esthetics_***
6. ***_Positioning of adjacent structures_*** (teeth, gingiva)
7. ***_Functional requirements_***
8. ***_Retentive factors_*** (ex. dovetails)
36
What is the name for the shape and placement of the preparation walls that best enable both the restoration and the tooth to withstand, without fracture, masticatory forces delivered principally in the long axis of the tooth
***_RESISTANCE FORM_***
Helps maintain function and to last
37
What are the descriptions that relate to resistance form of a cavity preparation
1. ***_Flat floors/walls that are perpendicular to masticatory forces_***
1. Pulpal and/or gingival floors
2. ***_Restriction of preparation extension to allow strong cuspal or marginal ridges_***
1. Ex. conservation of unaffected tooth structure
3. ***_Inclusion_*** ***_of weakened tooth structure in the preparation design to prevent tooth fracture_***
1. ex. capping a compromised cusp
4. ***_Proper consideration of restorative materials_***
1. Ex. amalgam should have 90 deg cavosurface angles, rounded internal line angles, adequate pulpal depth
38
What is the terminology for the shape or form of the preparation that resists displacement or removal of the restoration form tipping/lifting forces
Retention form
39
What are the main features of retention form that help strengthen the design
1. ***_Dovetails_***
1. Proper positioning maintains width and strength of marginal ridges
2. ***_Convergent walls_***
3. ***_Grooves_***
4. ***_Pins_*** (only used in preparations that are larger than idea)
5. ***_Frictional resistance of walls_*** (nearly parallel, vertical or minimally tapered)
6. ***_Acid etch with bonding system_***
7. ***_Mutually divergent rounded areas_*** (composite resin)
40
Explain the idea of Dovetails retention form
Proper positioning maintains width and strength of marginal ridges
Provides retention to the restoration
(little C shape up thingy)
41
Explain the idea of convergent walls in retention form
occlusal convergence = "convergence"
Whereas you go from pulpal floor to cavosurface margin, walls become closer together
42
What type of cavity preparation is this?
Class II
Proximal surfaces preparation
43
Explain grooves retention form technique
44
Explain the terminology for the shape or form of the preparation that provides for adequate observation, accessibility, and ease of operation in preparing and restoring the tooth
Convenience form
45
What are the factors that influence convenience form?
Factors that influence:
1. **Extension of the preparation**
2. **Changing the direction of approach**
3. **Changing the instrumentation utilized**
Inadequate convenience form prevents properly instrumentation
\*\* want to be as conservative as possible
46
What is the terminology for the excavation of any infectious structure still remaining after the basic cavity design has been completed
Removal of remaining carious dentin
47
What is it called when dentin penetration by carious process 0.5 mm or less?
incipient lesion
48
What is it called when \>0.5 mm of dentin penetration by the carious process
extensive lesion
49
Explain the "ideal preparation"
Depth is 0.5 mm inside the DEJ after sets I, II, and III have been completed
* With inception lesion, Black's step IV does not apply
* With Extensive lesions where steps I, II, and III have been performed to 0.5 mm inside the DEJ and caries remains in the deeper aspects of the tooth
50
What is the step/terminology that involves smoothing and refining the walls of the cavity preparation as well as the cavosurface angle?
V. Finishing enamel walls
51
What is the purpose of finishing preparation walls?
* To effect a **good marginal seal** between the restorative material and the tooth
* To affect a **good marginal junction**
* Less noticeable to the patient
* Facilitate cleaning (less plaque retentive)
* To provide **maximum strength** to restorative material and tooth at the margin
52
What are the factors to consider during wall finishing
* Direction fo enamel rods
* Dentinal support for enamel rods
* Restorative material to be used
* Location of preparation margins on tooth
53
Explain the location of the enamel rods in the fissured surfaces (ie. occlusal)
* Rods converge from DEJ to surface in areas of pits and groves
* Rods diverge from DEJ to surfaces in areas of cusps and ridges
54
Explain the location of the enamel rods on smooth surfaces (proximal, facial, and lingual surfaces)
* Roughly perpendicular to long axis of the tooth in the middle 1/3
* Incline occlusally in the occlusal 1/3
* Incline gingivally in the gingival 1/3
55
Explain the idea of finishing enamel walls - enamel support
* Rods that form the cavosurface have their inner ends resting on sound dentin.
* Full-length rods from DEJ to cavosurface are preferred
* Full-length rods receive support form:
* DEJ
* By shorter rods that were cut, yet whose inner ends are resting on dentin
56
Which of the following is the correct method of finishing enamel walls and which one is not
57
Explain the final step in cavity preparation
VI. Cleansing and preparation
* Removing all debris from the cavity prepartion
* Followed by drying and inspecting for any remaining weakened structure (both carious dentin and unsupported enamel
58
What is force and how is it defined?
Force = generated by one body pushing or pulling on another
* Defined by:
* Point of application
* Magnitude
* Direction of application
59
Explain the details of occlusal forces as well as the loads during chewing
Biting force decreases from the molar region to the incisors
Normal chewing =\> usually \< 10 N
Axial and horizontal loads are produced during chewing Axial \> horizontal
60
Explain the details of a stress-strain curve
Stress (force/area)
---------------------------------------
Change in length
\*\*\*NOTE: INDEPENDENT OF GEOMETRY\*\*\*
Stress = newton/meter ^2 = Pa
61
Explain the types of stress that can occur
* **Axial (tensile)** = elongation
* **Axial (compression)** = shrinkage
* **Shear** = opposing shear forces over plane
* **Twisting moment** = torsion
* **Bending moment** = bending
62
Explain where stresses are experienced in the mouth, for example in a bridge
63
Explain the details of strain
Change in length per unit length of body when subjected to a stress
64
Explain the details of a stress-strain curve
**Elastic** = bounces back (straight line)
**Plastic** = permentent deformation
65
Explain the concept of the **_elastic limit_** in a stress-strain curve
What is another name for this?
Maximum stress that a material will withstand without permanent deformation (looks specifically at the material to determine change)
PROPORTIONAL LIMIT (looks at the graph to determine change)
66
Explain the concept of yield strength (such as a 0.2% offset)
The stress value at which a material exhibits a specified permanent strain
67
Explain the concept of ultimate tensile strength
The maximum stress that a material can withstand before failure in tension
(strongest = cobalt-chrome alloys
Weakest = porcelains (strong in compression though)
68
Explain fracture strength
the stress at which a material fractures
Not necessarily equal to ultimate strength
69
Explain the elastic modulus of a material
Represents the stiffness within the elastic range
E = stress/strain
More verticle = stiffer (cobalt - chrome partial denture)
More horizontal = more flexible (silicone rubber = impression material)
70
What are examples of brittle dental materials (in general)
Amalgam
Composites
Cements
Ceramics
71
What is the ability of a material to be plastically deformed?
Ductility
Gold = more ductile
Lead = more brittle
72
What is it when there is closing the metal margin of a metal crown
Recovery of elastic strain but not of plastic strain
Burnishing
\*\*always have elastic deformation then go over to plastic to permanently deform
73
What is the term describing the resistance of a material to permanent deformation
Important in orthodontic wire
***_Resiliency_***
Area under the straight portion of the curve
Maybe thought of as energy absorbed per volume of material
74
What is the term for the resistance of a material to fracture?
***_toughness_***
area under entire curve
Also thought of as energy absorbed per volume of material
75
Describe the following curves
76
Describe the following curves
77
What is the term for the maximum stress that a material can withstand before failure in compression?
Ultimate compressive strength
Amalgam = high compressive strength (posterior use)
Glass Ionomer (Fuji II - temporary fillings) = Low compressive strength, fill closer to gum line
78
What is the impact strength
The energy required to fracture a material under an impact force
Popular for comparison of denture base material
\*\*Charpy Impact Tester
79
What test is used for testing brittle materials to obtain a tensile strength. AKA indirect tensile test
Diametral compression test
Not valid if the material deforms significantly before failure
80
What is shear strength?
The maximum stress that a material can withstand before failure in shear mode.
Used frequently in bond strength testing
* Porcelain/metal interface
* Interface between tooth and orthodontic brackets, composed resins and adhesives
81
What is the test commonly used for testing adhesives?
Microtensile bond strength
Alternative to shear bond test
Very small sample testing
82
Explain the concept of bending and the types of bending
-\> compression \<-
----------------------------
Neutral axis
----------------------------
\<- Tensile -\>
***_Pure bending_*** = direct (perpendicular force)
***_Transverse bending_*** = force directly from top
83
Explain the concept of bending moment
Bending Moment = Force x Length = F x L = FL
\*\*DEPENDANT ON SHAPE!!\*\*
Not divided by L/Lo
84
Explain Flexural strength
Also called transverse strength
3 point bending test
Dental relevance:
* Denture base materials
* Long bridge spans
85
Describe the process of torsion
***_Twisting_***
Maximum shear stress on the outside
**Torsional moment = shear force x radius**
\*\*Not normalized for area
* Dental application
* Endodontic files
* Reamers
86
What is a progressive fracture under repeated loading
**Fatigue**
Failure occurs below the single load strength (static)
Failure typically due to crack propagation
S/N Plot show stress vs. cycles to failure
87
What are the factors affecting fatigue?
* ***_Environmental agents_***
* ***_Surface features_***
* Smooth (higher failure stress) vs. rough
* ***_Material history_***
88
What is a measure of a material's resistance to brittle fracture when a crack is present?
***_Fracture Toughness (_******_Kic_******_)_***
Useful for brittle material because failure is frequently flaw dependent (crack propagation)
Metals = highest Kic
GI cements = low Kic
89
What is the definition of viscoelasticity
Having appreciable and conjoint viscous and elastic properties
Behavior is intermediate between that of elastic solid and a viscous liquid
\*\*Silly Puddy\*\*
Important in impression material and other polymer-based materials (dependant on time)
90
What is a time-dependent plastic strain of a material under a static load or constant stress (even if below elastic limit)
**CREEP**
Occurs in materials at temperatures above 1/2 melting temperature
91
What is the reduction in stress in a material subjected to constant strain?
Stress relaxation
Useful in evaluating orthodontic modules or chains
92
What is the resistance to permanent surface indentation?
What are the tests for this, name and describe
***_Hardness_***
Dental Importance:
* Some (not direct) relation to wear
* Affects ability to finish or polish a material
* Gives indication to resistance to in-service scratches (decreasing fatigue strength)
Tests:
* **Brinell**
* Metals Only. Micro test = ball indenter
* **Rockwell**
* Metals and plastics. Ball or cone indenter. find depth
* **Vickers**
* Metals and plastics. Micro test. Pyramid indenter
* **Knoop**
* Variety of materials. Rhombic-based pyramid diamond
* **Barcol**
* Dental materials app. measuring resin composites
* **Shore**
* Used for rubber (denture liners and mouth protectors)
93
What is a loss of material resulting from removal and relocation of material through the contract of two or more materials?
***_Wear_***
Grinding teeth
94
What is it when two body surfaces rub together called
***_Abrasive wear_***
***_Two-body_***
Harder surface = indents
Softer material = cut away
Tooth/tooth contact
95
What is it when two body surfaces rub together and there is another object between them called
Abrasive wear
Three-body
Food or toothpaste between teeth
96
What is it when wear coupled with a chemical attack called?
***_CORROSIVE WEAR_***
* Issue especially in posterior restorations
* Hydrolytic breakdown of the resin
* Breakdown of the resin/filler interface
* Erosion of the surface from acids
97
Explain the study of the flow of matter
***_Rheology_***
***_Viscosity: Fluid's resistance to flow_***
Units: poise = pascal x second
High viscosity = flows slowly
98
For liquids that do not set, how does their viscosity relate?
Viscosity decreases with increasing temperature and is independent of time
99
For liquids that do set, how does their viscosity relate?
Viscosity increases with increasing temperature and also increases with time
100
Explain viscosity on a shear stress vs. shear strain rate graph
***_Slope = visocisity_***
101
Explain a Newtonian fluid viscosity curve
constant straight line
water
some dental cement and impression materials
102
Explain a plastic fluid viscosity curve
No flow until a certain shear stress is reached (ex. tooth paste)
103
Explain a pseudoplastic fluid viscosity curve
Decreasing viscosity as shear rate increases
104
Explain a Dilatant fluid viscosity curve
Viscosity increases with shear rate
Corn starch and water
105
Explain a Thixotropic fluid viscosity curve
1. time dependence decrease in viscosity
2. Yield point similar to plastic
3. Not reversible shear stress/strain rate
Example = ketchup bottle
