intro to biomaterials-amalgam Flashcards by Madyson Flax

mixture and alloys(mix with metal):

porcelains and ceramics
polymers

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two types of polymers:

elastomeric (impression material)
plastics (denture base, sealants)

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composites are:

polymers with fillers

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performance of all dental materials depends on their

atomic structure

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atomic structure determines ____ and ____ properties of materials

mechanical and physical

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2 types of interatomic bonds:

primary and secondary

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ionic, covalent, metallic

primary

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hydrogen bond, van der waals forces

secondary

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primary bonds: ionic
electrostatic attraction of _____ and ______ charges

positive and negative

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involves electron transer between ions

primary bonds: ions
(one becomes + and one becomes -)

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examples of primary bonds:ionic

ceramics and gypsum

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properies are non-directional , strong bonds
and no free electrons with GOOD THERMAL and electrical insulators

primary bonds: ionic

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2 atoms share electron

covalent

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properties:
directional bonds
low electrical and thermal conductivity
water INSOLUBLE

primary bonds: covalent

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examples are water, glass, polymers, composite

primary covalent bond

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cluster of positive metal ions surrounded by a gas of electrons
non-directional bonds, high electrical and thermal

primary bonds: metallic

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examples of metallic primary bond

amalgam and gold alloy

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4 classifications of material properities

biological
surface
physical
mechanical

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biological response to material when in contact with human body
(ex. gingivitis from plaque)

biological

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unique properties of material associated with its surface
(dental retention and adhesive bonding)

surface

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depend on TYPE OF ATOMS and the bonding present in material; size or shape have NO AFFECT
(optic color or gloss, thermal conductive)

physical

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with physical classification, what is it dependent on and what has no affect

dependent on type of atoms
size and shape no affect

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reaction of a material to the application of external force, size and shape of specimen affect properties
(structure sens and applied force is load)

mechanical

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what affects properties in mechanical classification?

size and shape and rxn of external force (load)

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structure insensitive : sensitive:

insensitive physical sens mechanical

when does stress develop

when load (force) applied to material, stress develops

stress =

load per unit area

how much stress a material can withstand before it breaks

fracture strength

type of strength measured is dependent on

type of force applied

pushing- pulling- sliding- twisting- bending-

pushing- compressive pulling- tensile sliding- shear twisting- torsion bending- flexure

highest strength measure for most materials

compressive strength

compressive strength measure of the stress necessary to

fracture material by 2 opposing forced directed toward each other

lowest strength for most materials

pulling/tensile strength

measure of stress necessary to fracture material by 2 opposing forces directed away from each other

tensile/pulling force

usually requires high loads to cause failure: failure occurs at lower loads:

usually requires high loads to cause failure: compressive failure occurs at lower loads: tensile

intermediate strength between compressive and tensile

shear strength/sliding

clinical situation with shear force:

implant-bone interface

not relevant to direct or indirect dental restorations used to place dental implants fatigue of endodontic rotary files

torsion strength

what force is measured using a 3 point bend test

flexural strength

compressive load and combination of compressive and tensile stress

3 point bend test

what is vital due to occlusal load on direct restorations such as amalgam and composite? indirect (everything getting chewed on)?

flexural strength (3 point bend test)

examples of dental stress:

protrusive movements (ant teeth or flexure load on incisors) and posterior occlusion (chewing=compressive load) at marginal ridge contact areas and at fossa areas

occlusal stress =

load(force)/occlusal contact

allows distrubution of occlusal load acorss max area = minimum stress known as

tripodized occlusal contacts

this results in decreased AREA patient's occlusal force stays the same but occlusal stress is increased!

premature contact

deformation that occurs in a material when force is applied to the material

strains

strain=

change in length (deformation)/unit original length

stress and what are related if you have one you will have other

stress and strain

temporary distortion of material by applied force STRAIN IS BELOW ELASTIC LIMIT when force removed, materials revert back to original form

elastic strain

permanent distortion of material STRAIN IS BEYOND ELASTIC LIMIT when force removed, shape remains changed

plastic strain

effective barrier against recurrent caries

amalgam

amalgam alloy composition: 1 2 3 4

1. Ag 70% 2. Sn 16% expansion 3. Cu 13% strength 4. 1% deoxidizer

high copper amalgam is superior to conventional amalgam. presence of copper nearly eliminates ______ resulting in stronger restoration

gamm-2-phase

what amalgam shapes: 1. lathe type particles mixed with small spheres -requires more condensation force -most commonly used type of amalgam -low early strength 2. outdated and particles formed by cutting blocks- large irregular 3. higher early strength and 24 hour strength -requires less condensation force

1. admixed 2. lathe 3. sperhical

less what in final restoration of amalgam is superior

less mercury

most critical variable with almagam manipulation? most common error made by dentists

condensation

what are the 4 variables of amalgam manipulation

mercury to alloy ratio trituration condensation carving and finishing

amalgam: high ____ strength low ____strength

high compressive strength low tensile strength

amalgam brittle in small bulk _____mm pulpal depth _____isthmus

pulpal depth: 1.5-2mm isthmus: 1 mini

what element is added to prevent amalgam expansion

zinc

the order of needed compression force for amalgams from high to low is:

lathe>admixed>spherical

what will increase the strength of amalgam

high copper content

does premature occlusal contact increase or decrease stress on the tooth? why?

increase because the surface area contact is smaller (decreased area)

energy absorbed during elastic strain: energy absorbed during plastic strain:

elastic: resilence, temporary plastic, permanent distortion

T/F. elastic limit delineates the transition from elastic strain to plastic strain. T/F: brittleness a property caused by lack of elastic deformation

first T second F

which of the following describes amalgam restorations compared to composite restorations? a. less recurrent decay b. moisture sens c. lasts for a longer time d. a and c

less recurrent decay lasts for a longest time

amalgam is sensitive to moisture contamination during

placement but still better choice if moisture control is difficult

___ are formed which expands and fill tiny voids, preventing microleakage. no other dental restorative material does this (in amalgam)

oxides

liner is placed in ____ layer over dentin base is placed in _____layer on floor of prepared cavity

liner thin layer over dentin base thick layer on floor of prepared cavity

stimulates reparative dentin formation:

calcium hydroxide LINER

light cure and releases fluoride over time

glass ionomer LINER/BASE

what is true about both liners and bases? a. stimulate reparative dentin b. can only be placed in center of prep c. release fluoride d. used in preps of any depth

a. wrong- only liner b. true- keep away from margins c. wrong- only base d. wrong- deeper areas only

what are 4 causes of bulk fracture in an amalgam restoration?

1. premature occlusal contact 2. improper condensation 3. fatigue of the material 4. improper trituration

true or false tarnishing and corrosion of amalgam changes the amount of material in a preparation

true

1. copal resin 2. bonding agents 3. gluteraldehyde (gluma)

types of desensitizers

surface of dentin when it is cut

smear layer

the cutting edge of a cutting instrument is similar to the face of a non-cutting instrument just as the blade of a cutting instrument is similar to the ____ of a non-cutting instrument

nib