Biomaterials 2 Flashcards

Terms Definitions
Compact Bone
Cortical Bone
Examples of natural polymers:
Elastic Modulus
Stiffness, interatomic bonding
Define biomaterials
Synthetic mateirials for use in the body
Microfilled resin
filler: fumed silica(.02-.04 microns). paste has large particles due to method of fabrication. compared to conventional: brittle, low elastic moduus, high coeff of thermal expansion, H20 absroption ofset by shrinkage, high strength:compression, tension , transverse.
Stiffness vs Strength
Stiffness /= Strength
Smallest repeating unit in polymer chain
Aquesous corrosion is an [blank] phenomenon
List the five types of stress:
EBA cements properties(ethobenzoic acid- 50 to 66%, little ZnO)
USES:Cementing inlays,crwons,bridges; as a base or lining mat; temp filling. Strength: 8000 to 1000psi (similar to ZnPO4) by increasing powder/liq ratio; tensile strength: lower about 500 to 800psi. Solubility similar to ZOE. Thickness: 40 to 70microns. Setting time: 7 to 13mins.
Suppress or kill T-cells- increased risk of infection & cancer
Allografts - pros/cons
PRO:- functioning heart, adaptableCON:- no innervated, surgical injury, infection/rejection
"Heart Transplant"- Brain dead source- Cold Static Storage transportation- Sternotomy - cut open sternum- Patient on immunosuppresents
Polymer Leeching
- Unreacted Mer- Colorants- Manufacturing reminents
Define metalloid
Material that exhibits both metallic and non-metallic behavior
Define plasticizer
Liquid capable of penetrating between the randomly oriented chains of a polymer
Yield point:
Point where plastic strain becomes very pronounced; rapid inc. in strain without accompanying stress
Advantages/disadvantages of Polycarboxylate
Advan: strength, solubilty, film thickness comprable to ZnPO4, easy mixing, little pulpal rxn. Dis: accurate proportioning req for optimum properties, moderate compressive strength, clean surfaces required for proper bonding and short working time.
dry, crumbles. It has a low compressive strength, excessive expansion.
Disadvantages of ZnPO4
Brittleness, solubility in organic acids and oral fluids, pulpal irritation(liner must be used in deep cavities), lack of adhesion to tooth structure which leads to leakage.
filler size: .5-5 microns, matrix has fumed resin, it controls resin- toughness and handling viscosity.
ZnO-Eugenol properties
USES: Temp cementation of rest, cavity lining , temp fillinfmat.low compressive strength: 100 to 1000 psi. Tensile strenght is very low. High solubility, 1.5% by weight in distilled water in 24hours. Film thickness si about 40 micros.
CorCap Fabrication
"Atlas Knit"- intertwined fibers of multi-filament yarn in diamond patterns- Seams facing out- Low Profile
Heart Failure Causes
1) Work overload, mechanical abnormalities2) Myocardial abnormalities3) Abnormal cardiac rythym
Endurance limit
A material won't break below this limit
Three types of grain structure
Equiaxed coarse
Equiaxed fine
Fibrous grain
metal modified GI
adding amalgam->set quickly but bonds less. silver particles has better physical properties. Bonds well to dentin but is too weak for core mat for crowns. Has increased wear resistance compared to normal GI.
Static creep
Constant load 360 kg/cm^2 for 24 hours
Role of filler particle
strength, reduce shrinkage, increase wear strength, reduce coeeficient of thermal enamel 12,resin 70-100, composite 20-40ppm. interract w/ matrix resin, bonding the particle to the resin. Filler is 65-85% wt
Advantages/disadvantages of ZnO eug
advan: minimal biological effetcs, good initial sealing properties, adequate strength for final cemetaion of restos.Disad: lower strength, higher solubility and disintegration than zinc phos cements, hydrolytic instability, softening and discoloration of some resin restorative materials.
Ultimate Tensile Strength
Resistance to necking (large localized strain in specific area)
Alloimmune Response
- Critical determinant of any immune response are antigens- Major Histocompatibility Complex (MHC) is primary diff. between people
Types of acrylic
1- Acrylic fabric (not relevant to dental biomaterials)
2 - Acrylic resin (aka PMMA) used for dentures
3 - Acrylic acid - water soluble polymer for adhesive dental cements
Modulus of resistance:
 Amount of energy a material can abosrob without permanently deforming; Area under the graph up to the proportional limit; has units of energy J/m3
Effect of mecanical history on alloy:
Cold working
Deformation of structure
Hinders movement of dislocations
Material less easy to deform
Composite resin
it is compromised of a continuous or matrix phase of resin in which there is discontinuous or dispersed phase of another material. eg fiberglass is a type of com resin , glass fib embedded in a matrix of fibers. The dispersed phase help reinforce the matrix phase.
Electrical insulation of cements
under metallic restoraion to minimize galvanic effects.
Advanatages of ZnPO4
handles easily, has good record of clinical durability. High compressive strength, low film thickness values.
Complex Syndrome of HF
- Pathology at gene/tissue level- Hemodynamic alterations- Breathlessness, fatigue, chest pain
Coronary Arteries
Branch off aorta to supply blood to heart
Effect of cold working on metal
Leads to a fibrous structure
Because biomaterials are not as durable as sound tooth tissue it is important to recognize the importance of:
1. Prevention of caries
2. Conservative treatments
3. Durability of treatments
Effect of recrystallization on metal
Further heating cuases reformation of equiaxed structure
Glass Ionomers cements properties
USES: luting cement, filling mat for erosion cavities, pit n fissure sealant, liner underneath other rest mat. Strength: 20,000psi, diametral strength is lower about 1600psi. Solubility: depending on powder/liq ration around .3 to 3%.
Compressive strength and marginal breakdown
the higher the slow compressive strength the less the observed rate of marginal breakdown.
Increased powder/liq mixture for ZnPO4
gives more viscous mix, shorter setting time, higher strength, lower solubility and less free acidity.
Molecular Weight for Polymers
- Number Average (Mn)- Weight Average (Mw)
What happens in a viscoelastic material?
There is breaking of intermolecular bonds (plastic behavior) and uncoiling of polymer molecules (elastic behavior)
Effect of molecular weight on polymer
Higher molecular weight = higher strength and rigidity
Single Cu admixed alloy
high Cu lathe cut and high Cu sperical.
Effect of grain growth on metal
Even more heating causes large grains to form
The hardness of an alloy depends on:
1 - chemical composition
2 - mechanical history
3 - thermal history
Biological effets of ploycarboxylate compounds
bland effetc on pulp similar to ZOE. Related to rapid rise of pH towards neutrality, min movement of fluid in dentin tubules in response to cement.
List 4 steps in addition polymerization:
1 - activator reacts with initiator to give free radicals
2 - Free radicals react with monomers to give larger free radical
3 - Propagation
4- termination
Biological effects of reinforced ZnO eug.
bland and obtudent on the pulp, some inflammatory rxn in connective tissue,
Effect of chemical composition on an alloy:
An alloy is harder than any of the individual metals from which it has been prepared
Hardness depends on:
number of different compounds 
relative amount of each component 
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