Composites

a composite can be defined as…

a union or combination of two or more insoluble materials

dental resin-based composite (RBC) = ___________________ + ____________

organic resin matrix + inorganic filler particles (monomers)

application of dental composite uses the ________ technique, followed by…

layering; pigment staining and light-curing

evolution of resin-based composites

monomers → initiators → filler

unfilled resin (PMMA, polymethyl methacrylate) has inc properties of… (4)

• polymerization shrinkage

• coefficient of thermal expansion

• water absorption

• solubility

unfilled resin (PMMA, polymethyl methacrylate) has an dec properties of… (5)

• color stability

• surface texture

• wear resistance

• modulus of elasticity (flexible/softer)

• radiopacity

method of polymerization of unfilled resin

chemical cured

chemical formulas of ______________________ are commonly used in dental composites

di-functional monomers

what are the three difunctional monomers used in dental composites

• Bis-GMA (bisphenol-glycidyl dimethacrylate)

• UDMA (urethane dimethacrylate)

• TEGDMA (triethylene-glycol dimethacrylate)

what is special about the ends of the di-functional monomers

double bonds at the end

what are the inorganic filler systems that can be used in resin-based composite (7)

• silica (highly dispersed)

• barium glass

• Ba-Al-fluorosilicate glass

• mixed metallic oxide

• Yttrium fluoride

• zirconia

• hydroxyapatite

describe this particle of inorganic fillers

porous, friable nano-clusters

describe this particle of inorganic fillers

solid particles

in silane, the methacrylate group on the other end of the silane molecule can react via…

free radical addition polymerization w methacrylate groups in subsequently placed adhesives and methacrylate-based resin cements

the individual silane molecules have covalently bonded not just to the filler surface…

but to the adjacent silane molecules- essentially forming a polymer network on the filler surface

the coupling agent, silane, plays a critical role in the…

composite

what is the common coupling agent

silane

the coupling agent, silane, forms an interfacial bridge that strongly binds the…

filler to the resin matrix

the coupling agent silane enhances the mechanical properties of the ________________ and minimizes…

composite; minimizes plucking of the fillers from the matrix during clinical wear

the resulting interfacial phase of the coupling agent, silane, provides a medium for…

for stress distribution between adjacent particles and the polymer matrix

the coupling agent silane provides a ___________________ (hydrophobic/hydrophilic) environment that minimizes…

hydrophobic; minimizes water absorption of the composite

result of unfilled acrylic resin

crack

describe the structure of composite

is a set of interconnected elements that collaborate at runtime to achieve some properties; each element has some defined role in collaboration

resin-based composite biocompatibility

less resin content; delay the crack propagation through the system

evolution and classification of resin-based composites

macrofill (1960s) → microfill (1980s) → microhybrid (1990s) → nanohybrid (2000/present)

which classification of resin-based composites is multipurpose

microhybrid

classification of particle size

manufacturing of dental composite

macrofill filler size

10-50 microns

microfill filler size

0.04 - 0.06 microns

hybrid filler size

1 - 10 microns + 0.04 - 0.06 microns

the hybrid classification of resin-based composite is a _________ particle hybrid

small

composite resin (Bis-GMA + filler) was introduced in the late 1960s to replace unfilled resin, it has evolved in that now, it has dec properties: (6)

• polymerization shrinkage

• coefficient of thermal expansion

• water absorption

• solubility

  remained the same:

• color stability

• surface texture

  • POOR POLISHABILITY

composite resin (Bis-GMA + filler) was introduced in the late 1960s to replace unfilled resin, it has evolved in that now, it has inc properties: (3)

• wear resistance

• modules of elasticity

• radiopacity

the major takeaway properties of composite resin (2)

• improved mechanical properties

• poor polishability

surface texture differences between macrofill and nanofill

easier to smooth if it is a nanofill

controlled wear of nanoclusters prevents…

loss of large particles allowing improved glass retention

wear surface of conventional hybrid displays…

loss of large particles and poor retention

advantages of microhybrid composite

high strength and modules

advantages of nanocomposite

high polish, strength, modulus

advantages of microfilled composites

best polish and esthetics

disadvantages of microfilled

higher shrinkage

advantages of packable (macrofilled) composite

packable, less shrinkage, lower wear

advantages of flowable

syringeable, lower modulus

disadvantages of flowable composite

higher wear

regarding consistency,composites can be classified in three categories

• packable (high)

• universal (medium)

• flowable (low)

what is important to note of properties of various types of resin-based composites

there are only a few evidences in nano composites

what is the evolution of curing systems

self cured→ uv cured → VLC

what are the three methods of polymerization

• chemical cured

• UV cured

• visible light-cure

what does amine function as when thinking about methods of polymerization

funx as a proton donor and an accelerator of free-radical production

what are the two ingredients in base (universal) paste

• monomer

• treated inorganic particles (silica & alumina)

in base (universal) paste, the monomer acts as the…

primary ingredient

in base (universal) paste, the treated inorganic particles (silica and alumina) are added for what

to add glint and strength

what are the four ingredients in catalyst paste

• monomer

• treated inorganic particles

• barium compounds

• catalyst

in catalyst paste, what does the monomer act as

primary reacting ingredient

in catalyst paste, what does the treated inorganic particles act as

add glint and strength

in catalyst paste, what do the barium compounds act as

radiopacity

in catalyst paste, what does the catalyst act as

starts and accelerates polymerization

reaction of composites

visible light curing composite (photopolymerization) properties (3)

• no mixing, less porosity, better shade control

• less finishing time, contoured before curing

• more color stable and wear resistance

why is delivering sufficient energy to resin-based composites (RBC) important

based on many scientific publications, light-cured RBC must receive adequate light energy to achieve their intended physical, chemical, and optical properties

what are the two types of light-curing units (LCU)

• quartz tungsten-halogen (QTH)

• light emitting diode (LED)

LED graph

lower wavelength and still gives off high power

what are the 5 light considerations

• emission spectrum

• spectral radiant power

• radiant exitance

• irradiance

• radiant exposure

what is emission spectrum

wavelengths in nanometers of light emitted from the curing light

what is spectral radiant power

power at each nanometer of wavelength (power/wavelength = mW/nm)

what is radiant exitance

what comes out from the light source (power/area = mW/cm²)

what is irradiance

what is received from the light source (power/area = mW/cm²)

what is radiant exposure

radiant energy applied to a given surface area over exposure time (energy/area = J/cm²)

radiant flux or power =

watt = 1000 mW

most LED or laser LCU produce a very narrow spectral emission and are usually optimized to cure…

the commonly used camphorquinone photoinitiator that is most reactive to light at ~468 nm

some RBCs use alternative photoinitiators that require v different wavelengths, it is possible to use…

an LED or laser unit that is not ideally matched to the RBC and in some cases the RBC will not cure at all

when talking about the spectral radiant power, all LCU emit blue light but this does not mean…

the spectral ranges and spectral radiant powers are the same

when thinking about radiant exitance, you want to ensure your LCU is in good working order…

clinicians should monitor the output of their LCUs using a radiometer on a regular basis; helps ensure the unit is funx optimally (make sure to remove adherent resin from tip-end surfaces)

when thinking of irradiance, we are specifically thinking about…

distance over angulation

the proximity of curing light to the surface affects…

the depth and penetration of light into the surface

in irradiance, there is an inverse relationship between…

distance and light intensity (distance inc, light intensity dec)

when the curing light passes through the composite, the light is attenuated significantly depending on…

the filler type, filler loading, hue of the composite, refractive properties, opacity, and translucency

what is the total energy concept

light curing process depends on the energy, this is determined by the radiant exposure/energy density received by the restoration and is the mathematical product of the curing light irradiance and exposure time

how to calculate curing time

apply all traditional composites w a layer of thickness of 2 mm and w the light probe directly on the restoration

inadequate polymerization will ultimately lead to

dec degree of conversion, dec physical and mechanical properties

light-cured RBC materials require the correct ________ and _________ to achieve their intended…

correct type (wavelength) and amount of light energy to achieve their intended physical, chemical, and optical properties

important things to remember for an effective use of dental curing lights

• protect your eyes

• position the pt

tooth preparation conservative steps

moisture control → etch enamel and dentin properly → adhesive selection → polymerize correctly → proper insert and cure for composite

a general rule for composites and light curing

apply a layer of all traditional composites of 2mm thickness and w the light probe placed directly on the restoration

bulk-fill restorative composite characteristics (5)

• inc depth of cure (>/= 4 mm)

• lower polymerization shrinkage

• acceptable esthetics

• inc wear resistance (?)

• good handling and adaptability

advantages of bulk-fill restorative composite (3)

less technique sensitive, reduced chair time, fewer voids

disadvantages of bulk fill restorative composite

esthetics (sometimes can be too translucent), limited choice of shades

bulk fill composites are not all the same and it is important to understand how to use them accordingly, the differences can be seen in…

viscosity of the material and its delivery

why is the depth of cure greater in bulk-fill restorative composite

due to less filler content and a higher level of photo initiators

bulk-fill restorative composites are highly elastic, why is this important

it will mitigate polymerization shrinkage effects bc shrinkage effects are compensated by the elasticity of the material

it is recommended to place ________(high/low) viscosity bulk-fill composite to achieve better wear resistance when used on high-stress areas

high-viscosity

it is recommended to place __________(high/low) viscosity bulk-fill composites to achieve intimate adaptation to the gingival and pulpal floors

low-viscosity

high-viscosity restorative composites result in how many cured layers

two cured layers- although they are bulk fills

high-viscosity bulk fill composites have better wear resistance but do not adapt well to…

do not adapt well to the cavity walls

what are resin monomers made up of

Bis-GMA (bisphenol-glycidyl dimethacrylate)

bisphenol- A (BPA) is associated w the manufacture of some plastics- including composites, but there have been some safety concerns about BPA…

BPA is a chemical sometimes involved in making plastics and dental materials. In lab studies, BPA acts like estrogen which raised safety concerns. BUT, these effects have not been seen in humans.

There may be small amounts of BPA exposure from dental materials due to saliva breaking them down.

The ADA currently has no concerns about BPA exposure from dental materials.

when considering prepping a tooth it is important to think about the amount of tooth structure is left and the likely-hood that the restoration will benefit the pt more than doing a crown. what depth of the tooth is still okay to do a filling

if it is less than ½ depth into the tooth

when considering prepping a tooth it is important to think about the amount of tooth structure is left and the likely-hood that the restoration will benefit the pt more than doing a crown. what depth of the tooth would you consider doing a crown

½ - 2/3 depth

when considering prepping a tooth it is important to think about the amount of tooth structure is left and the likely-hood that the restoration will benefit the pt more than doing a crown. what depth of the tooth would you recommend doing a crown

2/3 or more