composite
a mixture of 2 or more materials that has properties superior to any single component
composite resins
are tooth colored and can be placed in both ant. and post. teeth. Composed mainly of organic resin matrix and inorganic fillers joined together by a silane coupling agent.
most commonly used resin for the matrix of composites
bis-GMA
another type of resin for composites
urethane dimethacrylate
fillers
fillers are made up of inorganic particles such as qurtz, silica, and glass
fillers particles added in organic resins
to make them stronger, control handling characteristics, and help reduce shrinkage.
size of filler particles affect the composite resin material
particle size will affect the wear resistance and polish ability of the material. Also the higher the filler content, the stronger the material will be.
larger filler particles affect resin matrix
larger filler particles tend to get plucked from the resin matrix at the surface when the restoration is under function. also cause the finished restoration to appear dull or rough. (like cookie dough with lots of chocolate chips.)
smaller filler particles affect resin matrix
are not as easily pulled from the resin and therefore cause fewer voids that contribute to wear. also packed more closely together, exposing less of the resin matrix to wear. the smaller the particles, the smoother the surface.
what is a coupling agent and why are they used?
to provide a stronger bond between the organic fillers and the resin matrix. this agent is a silane, which reacts with the surface of the inorganic filler. Necessary to minimize loss of filler particles and reduce wear.
polymerization
the chemical reaction that occurs when low molecular weight molecules called monomers join together to form long-chain, high molecular weight molecules called polymers. (Process in which the material changes from plastic (mold-able) to a hard material fro
3 types for composite materials used in dentistry
chemical cure, light cure, and dual cure
a chemical cured composite material
is a self cured composite resin, represent a two paste system. base and catalyst. even mixture is important. disadvantage: limited working time.
a light cure composite material
Most commonly used. material is set with the use of a curing light with a blue wavelength. this allow ample working time to manipulate the material to desired form.
a dual cure composite material
utilizes both visible light and chemical reactions to cure the material. available in a two paste system or dispensed from a syringe. initial set is made by the curing light, then chemical reaction finishes the process.
3 classifications of fillers
macrofilled, microfilled, and hybrid
macrofilled materials
first generation of composite resin material. contains the largest filler particles. provides great strength but finishes with a duller, rougher surface and absorbs stains more easily.
microfilled materials
developed to overcome the problems associated with the larger particle size. contain much smaller particles, not as strong as macrofilled materials, polished to a glossy finish and does not stain easily.
hybrid materials
contain both macro and micro particles. easily polished, greater strength than micro, high wear resistance, and is a microhybrid- combination of small particles and microfine particles, are considered the newest generation.
flowable composites
low viscosity, light cured resins that are lightly filled. typically used in conservative procedures.
sealants
low viscosity resins that vary in filler size. used to prevent caries. contain little or no filler.
physical properties of composites
bio compatibility, strength, wear, polymerization, shrinkage, thermal conductivity, water absorption, radiopacity.
physical properties of biocompatibility
Newly placed composite resins can release chemicals that, in deep cavity preparations, could pass through the dentinal tubules into the pulp, causing inflammation.
When the tubules are sealed by dentin bonding agents and/or a base is placed, sensitivity i
physical property of wear
composites wear faster than amalgams.
physical property of polymerization shrinkage
shrinkage that occurs when the composite resin is cured. usually shrinks away from cavity walls.this is why small increments (1 to 2 mm) is important to decrease shrinkage.
physical property of thermal conductivity
composite resin has a thermal conductivity similar to natural tooth structure. (which is much lower in metal.) it is a biologically protective material for the pulp.
physical property of water absorption
The resin matrix absorbs water from the oral cavity.
The greater the resin content, the more water is absorbed.
Microfills and flowables have greater water absorption.
Water softens the resin matrix, which gradually degrades the material
physical property of radiopacity
metal such as lithium, barium, or strontium are added to the filler to make the restoration more opaque (light/whiter) when viewed in radiograph.
glass ionomers
self cure or light cured, tooth colored fluoride releasing cements that bonds to tooth structures. used to cement crowns bridges veneers and ortho appliances. also used as a liner, base or core.
Physical Properties of Glass Ionomers
Biocompatible
Bond to tooth structure
Release fluoride ion
High water solubility in the first 24 hours
Thermal expansion similar to that of natural teeth
Good insulators
Moderate compressive and tensile strength
Wear faster
Radiopaque
hybrid ionomers
These resins have some properties of composites and some properties of glass ionomers.
They are stronger than regular glass ionomers, are easier to polish, and are more wear resistant.
Indirect Restorations
Indirect restorations are fabricated outside of the mouth.
They include
Inlays
Onlays
Veneers
Crowns with porcelain or ceramic facings
initiators and accelerators
They are added to composite resin to help the material set.
Elastic Modulus
E-modulus or Young's modulus is the stiffness of the composite, which is determined by the amount of filler.The greater the volume of filler the stiffer and the more wear resistant the restoration.
compomers
Newer composite resins that have been modified with POLY-ACID (combined with composite and glass ionomers).
Releases fluoride but are not like glass ionomers.
Good color matching ability
polish well
medium wear rate