Resin composites
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Transcript of Resin composites
Resin compositesBy Dr. Dida Boru
April, 2014
A composite: a combination of two or more chemically different materials with distinct interface between them and having properties better than those of the components acting alone.
Resin composite: a restorative dental material containing ◦ Organic resin matrix◦ Inorganic filler particles◦ Coupling agent◦ Other components
Resin composite
Are high molecular weight monomers◦ Bisphenol A glycidyl methacrylate (bis-GMA)◦ Urethane dimethacrylate
Terminal methacrylate groups provide sites for free radical polymerization
Disadvantages of bis-GMA ◦ Color instability◦ High viscouscity ( decreased by adding TEGDMA
or EGDMA)
1. Organic resin particles
May be Colloidal silica: inert
◦ Low cofficient of thermal expansion◦ Improved condensability and polishibality
Barium silicate:medium hardness◦ Is very radiopaque
Quartz: most widely used filler material throughout 1970’s◦ Very stable and inert◦ Disadvantages lack of radiopacity
Abrasiveness High cofficient of thermal expansion Wear opposing tooth
Zinc silicate Lithium aluminium silicate
2. Inorganic fillers
The greater percentage of the filler content, the better the physical properties
Classification of filler particle size◦ Macro fillers: 10-100 microns◦ Midi fillers: 1-10 microns◦ Mini fillers: 0.1-1 microns◦ Micro fillers: 0.01-0.1 microns◦ Nano fillers: 0.005-0.01 microns
Generally the smaller the average particle size, the easier it will be to polish
Cont…
Its primary purpose is to bond filler particles to organic resin matrix
Improve physical properties of resin composite.
Most commonly used coupling agent are organosilanes (Gamma methacryloxy propyltrimethoxy silane)
3. Coupling agent
Polymerization initiators◦ For chemically activated: benzoilperoxide and
tertiary amines◦ For light activated: diketone photoactivators
(camphoroquinone) are used Polymerization inhibitors: monomethyl ether
of hydroquinone◦ to prevent spontaneous polymerization under
normal storage condition Uv radiation absorbers:
◦ added to improve color stabilty by absorbing electro magnetic radiation.
4. Other ingredients
Based on filler particles size: ◦ Traditional (convectional)◦ Small particle macrofilled resin composite (fine
particles)◦ Microfilled resin composites◦ Hybrid resin composites (blend)
Based on polymerization method◦ Chemically activated◦ Light activated
Types of direct filling resin composites
Filler : 70-80%◦ 20-50 micron size
Disadvantages: ◦ Roughness ◦ Staining and discoloration
Traditional (convectional)
Filler: 70-80%◦ 1-5 micron size
Good compressive and tensile strength (fracture resistant)
Polished nicely Recommended for large (2mm or larger)
diastema closure and for class IV cavity
Small particle macrofilled resin composite (fine particles)
Filler: 35-50%◦ 0.02-0.04 microns
Polish to high luster and produce excellent esthetic result
Should not be used in high stress bearing area
Physical properties are generally inferior to those of small particles macro filled resin composites
Good choice for class V cavity
Microfilled resin composites
The most commonly used nowdays Filler: 70-80%
◦ 0.04 and 1-5 microns sized Are usually radiopaque Physical properties are intermediate to that
of Traditional and Small particle macro filled resin composite
Fracture resistant
Hybrid resin composites (blend)
Two paste system Base: contain benzoyl peroxide Activator (catalyst): Contain tertiary amine Disadvantage
◦ Contain porosity
Chemically activated (self cured)
Ultraviolet light activated: ◦ contain benzoin methyl ether and tertiary amines
which when activated by UV light produce free radicals
Visible light activated: ◦ contain camphoroquinone (0.25%) photo initiator
and tertiary amines in single paste
Light activated (light cured)
Advantages of visible light resin composites over self cured composites◦ Longer working time◦ Shorter chair time◦ Greater degree of polymerization◦ Reduced porosity◦ Greater color stability
Cont…
Disadvantages◦ Non uniform polymerization secondary to limited
depth of penetration by the curing light Following light activation resin composites
continue to undergo polymerization for up to 24 hours
Cont…
I. Incremental addition of resin composite• Ensures completeness of polymerization• Reduces polymerization shrinkage stress
II. Resin layer should not exceed 2mm in depth
III. Minimum of 40 seconds exposure timeThe most desirable finish surface for a
composite resin can be provided by aluminum oxide disks
Contraindications for composite include varnish and zinc oxide-eugenol
Principles of proper polymerization technique
Dr. michael Bounocore developed acid etching technique using 85% phosphoric acid in 1955
Purposes◦ Increases surface energy◦ Chemically cleans tooth structure◦ Creates micropores for micromechanical retention
Standard acid etching of enamel is application of 37% phosphoric acid for 15 seconds with 15 seconds rinsing and 15 seconds drying
Acid etching technique
Other acids used ◦ Pyruvic acid ◦ Nitric acid
Depth of enamel caused by enamel etchin is approximately 10-15 microns
Bonding agent is used instead of acid etchant to open dentinal tubule ◦ EDTA
Cont…
Resin composite undergo volumetric shrinkage of 1.6-5.7% during polymerization due to monomer shrinkage
Most detrimental effect of shrinkage is microgap formation which results in ◦ Sensetivity ◦ Secondary caries◦ Staining ◦ Pulpitis and necrosis
Polymerizatin shrinkage
Indications◦ Class III cavity (except distal cavity on canines)◦ Class IV cavity◦ Cavity V cavity ◦ Filling gaps (diastemas) between teeth◦ Veneering ◦ Minor reshaping of teeth
◦ Partial crowns on single teeth ◦ As Pit and fissure sealant◦ Cementation of crowns
Indication and contraindications of resin composite
Contraindications ◦ Class II cavity ◦ Class I cavity ( only indicated if requirements
fulfilled)◦ Cavity on distal surface of canines
Resin composite is indicated for posterior tooth restoration if:◦ Restoration is not in occlusal contact◦ Isthmus is less than 1/3 of buccolingual
intercuspal dimension◦ Cusps are not involved◦ Margins are not involved
Treatment area must isolated well
Requirement for succesfull posterior resin composite
Esthetics Low thermal conductivity No mercury or galvanism Conserves tooth structure Easily shaped prior to polymerization
Advantages when compared to amalgam filling
Time consuming to place Micro leakage Post treatment sensitivity Excessive wear Low strength Highly sensitive to moisture
Disadvantages