Dental Materials 3 Flashcards

Terms Definitions
Elastic modulous
stiffness of material
Colloidal silica filler particles, approximately 0.04 µm in size, which reinforce resin materials and form a composite that can be polished to a highly smooth surface.
Diffusion coefficient
Proportionality constant representing the amount of a substance diffusing through a unit area and a unit thickness under the influence of a unit concentration gradient at a given temperature.
Ability of certain nickel-titanium alloys to undergo extensive deformation resulting from a stress-assisted phase transformation, with the reverse transformation occurring on unloading; called pseudoelasticity in engineering materials science.
a mixture of polymeric resins
a versitile irreversible hydrocolloid impression that is the most-used impression material in the dental office. Although it lacks accuracy and ease of use
______________ hydrocolloid is a irreversible hydrocolloid
___ prevent microleakage, kill residual microogranisms, stimulate reparative dentin formation, provide a sedative or palliative effect.
Relative interfacial tension between a liquid and a solid substrate that results in a contact angle of less than 90°.
Wetting agent
A surface-active substance that reduces the surface tension of a liquid to promote wetting or adhesion.
Force of molecular attraction between molecules or atoms of the same
Compound applied to metal surfaces that dissolves or prevents the formation of oxides and other undesirable substances that may reduce the quality or strength of a soldered or brazed area.
Structural appearance of a metal revealed by microscopic imaging of the chemically or electrolytically etched surface of a flat, polished specimen.
Time-dependent plastic strain of a material under a static load or constant stress.
thixotropic behavior
viscosity dependent on previous deformation
the three types of forces/loads applied to a solid
a rubber impression material with ether functional groups. it has high accuracy and is popular for crown and bridge procedures.
too much water __________- setting time
too little water ________ setting time
8 recognized specialties:
periodontics, endodontics, dental public health, oral and maxillofacial surgery, pathology, orthodontics, pediatric dentistry, prosthodontics
Mercury is a silver-white, poisonous, metallic element that is liquid at room temperature (symbol Hg).
Cold working
Process of plastically deforming a metal (usually at room temperature) that is accompanied by strain hardening.
Stress relief
Reduction or elimination of residual stresses by heat treatment.
Recrystallization temperature
Lowest temperature at which total recrystallization of a work-hardened structure occurs within a specific period (usually 1 hr).
Process of building up a localized area with a filler metal or joining two or more metal components by heating them to a temperature below their solidus temperature and filling the gap between them using a molten metal with a liquidus temperature below 450° C (840° F). In comparison with welding, fusion of the joined alloy part(s) does not usually occur during this process. Bonding of the molten solder to the metal parts results from flow by capillary attraction between the parts without appreciably affecting the dimensions of the joined structure. In dentistry, many metals are joined by brazing, although the term soldering is commonly used.
The process of heating closely packed particles to a specified temperature (below the melting point of the main component) to densify and strengthen a structure as a result of bonding, diffusion, and flow phenomena.
Interstitial atom
Imperfection in a crystal lattice consisting of an extra atom located between the adjacent atoms in normal lattice sites.
Stress relaxation
leads to distortion of elastomeric impressions.
Fracture toughness
The critical stress intensity factor at the beginning of rapid crack propagation in a solid containing a crack of known shape and size.
Unoccupied atom lattice site in a crystalline solid.
Dominant color of an object, for example, red, green, or blue.
The relative amount of elastic energy per unit volume released on unloading of a test specimen.
which has a higher modulus of resilience, dentin or enamel
All periodontal dressings are kept in place ____________ by interlocking in interdental spaces and by joining the lingual and facial portions of the pack
When mixing non-eugenol dressings, the set can be accelerated by placing the mixture in:
hot water
- performing dentistry in the seated position uses ________% less energy to do the same task standing
- may be straight, monoangled, biangled, or triple angled to accomodate the specific area of the mouth
instrument shank
hydration is the result of heating gypeum and driving off the water of crystallization
t or f
used to cauve occlusal anatomy
- ________ end is pointed
- ______________- end is disc shaped
originally used as a cutting instrument
cleoid discoid
When mixed with water, plaster or stone forms _________, a naturally occurring mineral that is mined in many parts of the world.
- motion conservation class that consrns only movement of the fingers
class I
class of motion conservation that involves movement of the entire arm from the shoulder
class IV
the act of absorbing moisture - material gets bigger
plaster requires ________ water for wetting than stone.
the ratio for plaster is _____/100g
more, 50g
Plaster and stone are chemically ______, but physically ______________ forms of the compound calcium sulfate
same, different
stone requires _________ water for wetting
the ratio is ___/100g
less, 30
a semisolid phase of a colloid
a gel
Compression strength
Sufficient strength to resist fracture is an important requirement for any restorative material. At a 50 percent mercury content, the compression strength is approximately 52,000 pounds per square inch (psi). In comparison, the compressive strength of dentin and enamel is 30,000 psi and 100,000 psi, respectively. The strength of an amalgam is determined primarily by the composition of the alloy, the amount of residual mercury remaining after condensation, and the degree of porosity in the amalgam restoration.
4 years
Ideally, sealants should be placed within ___ years of eruption of tooth.
Force per unit area within a structure subjected to an external force or pressure (See Pressure).
Percent elongation
Maximum amount of plastic strain a tensile test specimen can sustain before it fractures (See Ductility).
The ability of a material to sustain considerable permanent deformation without rupture under compression, as in hammering or rolling into a sheet,
Packable composite
A hybrid resin composite designed for use in posterior areas, where a stiffer consistency facilitates condensation in posterior teeth.
The process of cutting or grinding a structure using a device that traces the surface of a master metal, ceramic, or polymer pattern and transfers the traced spatial positions to a cutting station where a blank is cut or ground in a manner similar to a key-cutting procedure.
Amount of elastic strain that a metal can recover when loaded to and unloaded from its yield strength (important for orthodontic wires).
Point defect
Lattice imperfection of atomic size in three dimensions, such as a vacancy, divacancy, trivacancy, or interstitial atom
increase in force leads to a small increase in velocity
Change in dimensions of a material as result of applied force
Slope of linear portion of stress/strain
Modulus of Elasticity
holds hemostatic agents in place (i.e. sockets)
figure 8
- used to replace missing proximal wall(s) of cavity preparation for condensation of restoritive material
- variety of sizes shapes and thickness
matrix bands
an instrument that is designed or utilized to pick up materials from a source and carry it to the oral cavity
carrier instrument
if gypsum (calcium sulfate di-hydrate) is heated under pressure to high temperatures, the di-hydrate is transformed into a ______________ known as _________.
hemi-hydrate, dental stone
the assistant is usually positioned at what time on the clock?
3 o'clock
the branch of dental art and science pertaining to the restoration and maintenance of oral function
If this progressed into the attachment apparatus causing destruction of connective tissue, apical migration of the junctional epithelium, attachment and loss of bone surrounding the tooth /teeth. if it is left untreated, ultimately the tooth /teeth will l
periodontal disease
- a field of practice calling for intensive study and experience beyond graduation from dental school
Dimensional change
An amalgam can expand or contract depending upon its usage. Dimensional change can be minimized by proper usage of alloy and mercury.
The polymer in mouth guards is ____ meaning that is softens when heated and hardens when cooled.
luting cements
____ cements have low solubility in oral fluids, high sheer and tensile strengths, neutral acidity, adhesion to dentin and metal.
type II
Type ___ PRR, incipient carious lesion into dentin that is small and confisd, minimal prep of grooves removing caries/decalcification at DEJ, restored by using filled posterior composite resin in prep and adjacent p/f with sealant material, local anesthesia required
When curing, hold the light __mm from the sealant surface.
Inlay wax
A specialized dental wax that can be applied to dies to form direct or indirect patterns for the lost-wax technique used for casting metals or hot pressing of ceramics.
Stable cluster of atoms of a new phase that forms within a parent phase, such as during the solidification of a metal.
True stress
Ratio of applied force to the actual cross-sectional area; however, for convenience stress is often calculated as the ratio of applied force to the initial cross-sectional area.
Natural glaze
A vitrified layer that forms on the surface of a dental ceramic containing a glass phase when the ceramic is heated to a glazing temperature for a specified time.
Shoulder porcelain
A ceramic that is formulated to be sintered at the cervical area of a metal-ceramic crown to produce an aesthetic and fracture-resistant butt-joint margin.
Glass transition temperature
.Temperature at which a sharp increase in the thermal expansion coefficient occurs, indicating increased molecular mobility.
Strain rate
Change in strain per unit time during loading of a structure.
CAD-CAM ceramic
A ceramic that is formulated for the production of the whole or part of an all-ceramic prosthesis through the use of a computer-aided design and computer-aided manufacturing process.
viscosity (formula, units)
shear stress / shear strain ratecentipose or mPa-sec (NOT mega, but milli)
a small increase in force leads to a large increase in velocity
Who was issued the first licence (DH) in the state of Connecticut?
Irene Newman
guy who designed a numbering system utilizing the metric system for instrument identification
Dr. G.V. Black
When one of the metals in an alloy mixture is mercury, an amalgam is formed. A dental amalgam is a combination of mercury with a specially prepared silver alloy, which is used as a restorative material.
Fatigue is the property of a metal to tire and to fracture after repeated stressing at loads below its proportional limit.
T/F: The smaller the number of a bur, the smaller the size.
Stress intensity factor
A measure of the relative amount of increased stress at the tip of a crack of a given shape and size when the crack surfaces are displaced in the opening mode (See also Fracture toughness).
Indirect wax technique
Method by which a wax pattern is prepared on a die.
Flexural strength
Force per unit area at the point of fracture of a test specimen subjected to flexural loading.
measure of the tensile properties of a brittle material
diametral tensile strength
gut sutures need to be removed 5-14 days after being placed. gut sutures are made of prepared beef and sheep intestines.
both are flase
- this can be changed from a liquid solutionor sol into a rubber like gel simply by raising or lowering its temperatur.
- the transformation is a physical change and is not accompanied by a chemical reaction therefore it is reversable
"physical change
reversible hydrocolloid
right angled handpiece
the ____ handpiece is a low speed attachment for a straight handpiece which holds brushes or rubber cups.
glass ionomer cements
___ ___ cements have a chemical bond with the tooth structure, used as permanent luting agents, restorative materials, bases and core build-ups, made of calcium fluoralumionsilicate glass with barium glass added for radiopacity, polyacrylic acid copolymer in water.
Tensile strength (Ultimate tensile strength)
Tensile stress (in a tensile test specimen) at the point of fracture.
a dislocation line at the edge of a crystal can cause a...
unit of slip
how many years ago did injury plus evidance of dental disease was thought to be caused by bacterial invasion
100 million years ago
The Ideal Periodontal Dressing should be:
slowly setting to allow adequate manipulation, firm enough to maintain required shape, smooth and nonirratating, non-allergenic, acceptable taste, maintain flexability, hold its deminsional stability to prevent leakage/accumulation of debris, and prevent bacterial growth
Two types of Periodontal Dressings:
- Zinc Oxide and Eugenol containing
- Non-eugenol containing
Former: caries are simple, uncontrollable linear progression from acid demineralization to frank clinical lesion. Whereas the current idea states that caries progression is dynamic and involved demineralization and remineralization.
Explain the former idea of the progression of caries vs. the current idea.
A flaw is more dramatic when undergoing tensile force in a brittle or ductile material?
brittle, as a crack will developductile materials will 'even out' the flaw when pulled
having a high ratio of specular to diffuse reflection would have a ...
higher gloss(specular, like direct beamdiffuse, indirect)
some instructions to give the patient after placing their periodontal dressings include:
- avoid unnecessary manipulation of the dressing or he surgical site
- dont try to look and see the surgical site, you may crack and dislodge the dressing and open wounds are very painful
- dont brush the dressing
Composition and Effects of Amalgam: Combining desirable properties
Each metal incorporated into a dental silver alloy has specific properties when combined with mercury. Some properties are desirable and some are undesirable. An acceptable alloy is balanced. The combined effects of the properties of its ingredients should provide the most satisfactory restorative material.
shaft, shank, head
the ____ is the part of the bur that is inserted into the handpiece. The ___ is the neck. The ___ is the part of the bur that cuts, polishes or finishes.
what are some of the advantages and disadvantages for silk sutures?
advantages: inexpensive, easy to tie and soft to the tongue
Disadvantage: wicks, allows bacteria to be sucked near wound, not resoubed by the body, some what inflammatory
Composition and Effects of Amalgam: Quantity of mercury
Too little mercury in the mix results in a grainy, weak, readily tarnished, and corroded amalgam. Too much mercury will cause excessive expansion and weakened amalgam.
60 sec perm, 90 sec primary
Allow etching agent to remain on teeth for ___ seconds for permanent teeth and ___ seconds for primary teeth.
the most recent addition to the ADA list of gypsums, produced due to the need for dies with increased expansion to compensate for the greater shrinkage that occurs in the newer higher melting alloys used for dental casts.
W/P ration is 0.18-0.22 reslu
Type V: high strength expansion die stone
all of the above!! Also - cuttlefish bones- silica- crocus
Which of the following is commonly used in discs:- sand- garnet- carborundum- all of the above
what are the upper and lower lines on a phase diagram
upper is the liquiduslower is the solidus
false! only very deep, 0.5mm or less from pulp
T/F: Calcium hydroxide is only to be used in very shallow preparations.
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