Dental Materials

same atomic composition and structure, same bonding

ex: graphite & diamonds

must be enclosed or thermal energy disperses, very low density and very weak bonding; easy to compress

needs a continer, much denser than gases and hard to compress, medium bonding

self-supporting, dense materials with strong bonding

a dispersion of one phase in another, clusters or clums of atoms or molecules, not much bigger than macromolecules, a lot of surface area

the amount of mass of a material in given volume

a measure of a liquid's tendency to evaporate and become a gas

the junction of 2 phases, may or may not have the same atomic bonding

• gas, liquid, solid
• --weakest to strongest molecular attraction

crystalline or amorphous

crystalline- long range order, crystal systems, lattice structure

amorphous- short range order but no long range order, order much like that of liquid, these materials are sometimes thoight of as supercooled liquids or very disorganized crystals

ceramic, polymer, metal, composite

ionic; covalent and secondary bonds, metallic bonds; 2 or the above phases

EM force causes positive charges to attract negative charges and negative charges to attract positive charges.

ionic: electrons are given up and received

covalent: electrons are shared between atoms

metallic: electrons are shared between atoms

ionic: strong and directional bonds between charged atoms

covalent: strong and undirectional

metallic: less strong and nondirectional, but add

Dipoles, partial charges, weak, in order of increasing strength: fluctuating dipole, permanent, and hydrogem bond

Ionic; covalent and secondary; metallic

• 1. ceramic: ionic-translucent insulators
• 2. polymer: covalent and 2nd translucent- insulators
• 3. metal: metallic very opagque-conductors

• 1. ceramic: very strong and brittle
• 2. polymer:  weak and stetch (some strong)
• 3. metal: strong and tough

columbic force= attractive force

electronic repulsive force= repulsive force

equilibrium distance= forces are equal and opposite and balance one another

1. stregth= depth

2. elasticity= slope

3. melting point and boiling point= depth

4. thermal expansion= asymmetry of slope

interlocking of two objects, as with a nut and bolt

molecular bonding at the atomic level of to dissimilar materials, must get the adhesive in intimate contact with the surface to get molecular bonding

molecular bonding of a material or two like materials

a material that can stick to a flat surface or bond 2 flat surfaces together (bonding material)

the surface

tooth/restoration junction

a surface with an adhesive material, such as a sealant, brings the material into intimate association with the surface so that chemical and micromechanical bonding can occur

low good wetting; high poor wetting

high surface energy of the solid= good wetting

failure can also be adhesive (at the interface) or cohesive (in the material)

surface energy= high- good wetting

surface roughness= rough- poor wetting

surface cleanliness= clean- good wetting

temperature at which melting occurs

amount of energy needed to melt a material

the rate of heat flow through a material

a combination of raising the temp and heat transferred

temp where material goes from glassy to rubbery material

nearly all things expad when heated

amount of energy needed to melt a material

measure of the amount of thermal energy that a material can hoard

the amount of energy needed to raise the temp of one unit of mass of that material by 1 C

mixtures do not have a specific melting temp, but have a range

change in temp may change energy

the amount of energy needed to iniate a reaction

diffusion

reaction products per time

greatly affected by temp

greatly affected by temp

a force

weight or load applied to object

the accompanying change in shape or deformation; change in length

atoms return to their original positions when the stress is removed, no permanent deformation, no change in shape or atomic position

atoms don not return to their original positions but recover only the elastic part of the strain when the stress is removed, change in shape, permanent deformation

change in shape, bend in a metal coat hanger

tells how stress and strain are related; stress and strain are proportional when there is only one elastic strain

when the stress exceeds the limit of only elastic strain, then plastic strain begins, the stress/strain plot is no longer linear

same as the yield point

same as the proportional limit * the difference of these is in the testing methods**

max strength a materical can withstand, the highest point on stress/strain curve, not necessarily the breaking, fracture, or failure point 

the plastic strain when fractured in tension

stress/strain

the proportionality constant between stress and strain or the slope of the linear portion of the stress strain curve

same as the modulus of elasticity, the stiffness of material

amount of energy absorbed up to the elastic limit

the ability of a material to resist fracture, energy to fracture

the ability of a material to resist fracture, energy to fracture

describes a mechanical property that is defined as the ratio of the strain in the direction of the stress to the strain in a direction perpendicular to the stress

a pushing or crushing or stress

a pulling stress

(slip) stress occurs when parts of an object slide by one another

stress is a twisting force

a common stres and is actually a combination of several types of stress

a test to determine tensile stress which is directly proportional to the compressive load applied

resistance to ripping or tearing/ energy absorbed from a sudden single blow

many things do not fail (break) immediately but after a period of time

the max stress a material can endure without breaking for an infinite lifetime

withstand permanent deformaton under tension

withstand permanent deformation under compression

ability of a material to resist indentation by a point

wear resistance

how thick a liquid is, how much is resists flow

study of viscosity.

viscosity is not dependent on the flow rate

shear thickening, gets thicker as flow rate increases, slurries

shear thinning, gets thinner as flow rate increases

at constant flow rate, viscosity DECREASES with time

at constant flow rate, viscosity INCREASES with time

flow and elastic together

the small change in shape that results when an object is under continous compression

decay of stress

measure of the energy it takes to fracture a material when a crack is present

related to the speed of light in that materal

a psychological response to electromagnetic radiation

general color; vividness/strength, brightness

the energy that a tooth absorbs is converted into light with longer wavelengths, in which case the tooth actually becomes a light source

affects the appearance of an object; can be seen through

also affects the appearance, cannot allow light to pass through

shade matching system of three dimensions

objects that appear to be color matched under one type of light may appear different under another light source

color is measured with a spectrophometer, and the data is mathematically manipulated to get 3 numbers on the 3 axes of a "more homogenous" color space

usually a mixture of the various wavelengths; it is selectively absorbed or scattered (or both) at certain wavelengths

reflection of light from an object onto the eye; the eye is most senstivie to light in the green-yellow region and least in the red or blue regions

light is focused on the retina and is converted into nerve impulses that are transmitted to the brain

personal perception of color, varis in humans

metals conduct electricity

resistance to electrical current

some materials absorb water

some materials dissolve in various aqueous fluids

dissolving

things degrade and separate after a period of time

Mixing time is the amount of time you have to mix something, working time is the time between the addition of powder to liquid and the loss of gloss, and the setting time is the time it takes to completely set. 

time: the older a material is, the less effective it will be

temperatue: temp and humidity will also effect the material

Electons absorb and scatter; some materials are radiolucent and are not seen on radiographs, other materials are radiopaque and are evident on radiographs

Gypsum was originally used for building products. It is mined in various parts of the country, or is a byproduct. It is used as positive casts or models and dies. There are different water to powder ratios depending on the results you are wanting. Mainly, the powder is mixed with water to form a slurry.

The reaction is a reversal of calcination. Mix to form a slurry or suspension to saturated to supersat to dehydrate precipitates out to heat liberated (exothermic).

1. Plaster is manufactores in an open kettle, gypsum ground and heated to 110- 120 C.

2. Stone is manufactrued in an autoclave.

3. Improved stone is manufactured by boiling CaCl solution.

They are all the same euqation they only differ in physical characteristics!

• 1. plaster: white, irregular crystals, porous spongy particles
• 2. stone: buff colored, regular, prismatic and non-porous particles, clevage fragments and crystals
• 3. Improved stone: non porous large particles, cuboidal, smooth, lower surface area

The water/powder ratio affects the setting time, thicker sets faster, thinner is weaker, and thick results in more expansion. A higher temperature usually causes it to set faster. Longer mixing results in a faster set frim more nucleui, more expansion. Accelerators decrease the setting time, while reatders including setting time, both reduce expansion.

Precipitation occurs from nuclei of precipitation. When the number of nuclei or the rate of their formation increases, it results in a faster set.

Setting expansion is due to crystal thrust.

The theoretical water/powder ratio is 18-19cc. Some produts need more water, but are weaker.

Colloidal systems reduce setting at surface. K2So4 accelerates the set rate, and borax retards setting.

Twice the normal expansion, add extra water before initial set; physical not chemical. Replace water used in hydration, get rid of contraction due to surface tension and get more effective and addititonal crystal thrust and crystal growth. 

Restorations, cements, denture bases and teeth, ortho appliance retainers, impression material, and others.

one unit, one link

two units

three units

long chains of repeating units usually identical, at least chemically similar, can be brached or crosslinked, mol wt of thousands to millions

2 kinds of units that are joined together that functon as a large monomer

addition of monomers to make a polymer

side groups bond to other chain

polymers that do not melt, flow, and be molded

can withstand a large amount of plastic deformation

glassy polymer, plexiglass, little deformation, brittle, these are usually called the "plastics"

can undergo a large amount of elastic deformation, stretch and return to original shape

free radical polymerization

first step in the induction reaction, usually a chemical, heat or radiation

what activates the initiator

a compound with an unpaired electron that is used to initiate polymerization

something that prohibits a reaction from occurring or completing

the reactions that produce step growth polymerization can progress by any of the chemical reaction mechanisms that join two or more molecules in producing a simple, macromolecular strucutre; get a biproduct

polymeric materials shrink when they react

used during step growth polmerization; type of monument that is used which are all simultaneously activated

one kind of unit, branched or straight

polymer made up of two or more monomer species but with no sequential order between the mer units along the polymer chain

a polymer made of two or more monomer species and identical monomer units occurring in relatively long sequences along the main polymer chain

a polymer in which sequences of one type of mer unit are attached as a graft (branched) onto the backbone of a second type of mer unit

a nonlinear polymer

several units that are joined together that function as a large monomer

a group on a monomer/polymer that can be used to react with another

The three means of activating addition polymerization are by chemicals, heat, or radiation (light). Chemical uses tertiary amine and BPO, and light activated systems use several chemicals and photons.

• advantages:
• -chemically stable in water, acids, and solvents
• -color stability
• -some can exhibit large amounts of elastic deformation
• -some can absorb large amounts of energy
• -insouluable in water

• disadvantages: 
• -shrinkage
• -large coeffficent of thermal expansion
• -not as strong as ceramics or metals
• -poor abrasion resistane
• -high creep and flow
• -some soluable inorganic liquids

size of side groups: larger side groups decrease slippage; can also result in less strength and a softer material because the chains are further apart

Resins are glossy polymer tht have little deformation and elastomers can undergo a large amoint of elastic deformation. Dental resins are used for denture bases, denture teeth, temporary crowns, and other things. Filled resins or composites are used for restorations and many other uses.

the monomer determines chain flexability, cahin to chain interaction, and crosslinking

increases toughness and impact strength

adds color

If it is  a heat cure system: the reaction starts when the mix is heated, so it will have time to work with the mix before it is heated and the reaction starts.

If it is a cold cure or chemically activated system, the reaction starts when the activators and iniatior react and produce free radicals. The first free radicals react with the inhibitor, destroying them, providing working time, after the inhibitor is used up then polymerization beigins forming chains.

Residual Carbon carbon double bonds can react with new material. As the monomer easily evaporates, residual carbon carbon double bonds are only present for a short time,

New material can be physically bonded to old materials by dissolving the set polymer in new polymer in new monomer, similar to the usual mixing monomer and polymer.

preventative materials, restorative/replacement materials, and auxillary materials

Nontoxic, biocompatible, esthetic, comparable physical and mechanical properties, usable, bond to tooth structure, stable properties over years

Dental materials need to bond well with dentin and enamel in order to prevent leakage.

• Gold was and is used for crowns, bridges, and partial dentures,
• Gold is strong and wear resilient so is therefore characteristic of IRM. 
• ZnO evolved as fillings and cements to "glue" the restoration of the tooth.

• Amalgam was widely accepted and frequently used in the 1800s.
• -Cast metals were used in the 20th century for crowns, bridges, and partial dentures. 
• -Acrylic resins started being used in 1940. 
• -Composites began being used in the 1960s, and are alternatives for many dental materials.

In 1919, a detnal research program at the National Bureau of Standards was organized, called NIST. In 1928, the ADA sponsored a Dental Research Fellowship at NIST, and a great deal of coroporation exists today.

• -ADA Specifications are material standards, they are generally laboratory tests of physical properties. If a product passes the tests in the ADA/ANSI specifications, it is given ADA acceptance. The manufactorer may then use the ADA Seal on packaaging and in advertising, but the advertising must be approved by the ADA. 
• -Also, for many products and materials, there are no ADA specs. If a products is shown to be safe and effective by meeting Acceptance Guidelines, certain laboratory tests or clinical trials, it is given ADA Acceptable and may use the Seal.

The American National Standards Institute, ANSI, works with the Council on Scientific Affairs, which determin the needed tests to form and review ADA/ANSI Specifications.

-ISO standards for many dental materials have been developed and continue to be developed under the guidance of the Federation Dentaire Internationale.

In 1976, the Medical Devices Amendments were passed. This legislation got the FDA involved. Dental materials and other products are subject to control by the FDA Center for Devices and Radiological Health. All dental materials are classified as devices.

class I = products are low risk items and have only general good manufactoring regulations

class II= products have more regulation including federal performance standards or others (such as ADA Acceptance)

• class III= products have the most regulation including premarket approval.
• Manufacturers must provide data demonstrating safety and efficiany before marketing.

Processing effects structure at all levels, and thus mixing and handling are important.

a. biting forces= average biting forces of a person with teeth is 170 lbs

b. temperature changes= things expand when heated, cracking can occur when things are rapidly heated or cooled

c. acidity= adds discolor and corrode metals, mouth is warm place for bacteria to produce acis and other metabolites, acids and salt promote corrosion

microleakage= the leakage of fluids, bacteria, and other debris can irriate the pilp and lead to recurrent decay

galvanism= a mini battery can be set up if 2 different metals are present in the mouth, get a small current

toxicitiy= can be harmful to the pulp and other oral tissues as well as the dental personnell

stability= properties need to be stable over a lifetime

permanent or temporarily permanent= 10-20 years of more not planning to replace

temporary or provisional= days to a few weeks or a month, planning to replace

interim= long term temporary, several months to years, planning to replace after a particular time period or treatment

direct restorative materials= placed and molded in the mouth

indirect materials and techniques= constructed outside of the mouth, need auxillary materials such as impression and model (cast) and cement materials

functions= restorative material, luting agent, impression material, model/cast material and auxillary materials; intermediate base and insulator or lining protective material used to protect the pulp from thermal, chemical , and electrical insult