Restorative dentistry 3rd year Lecture 2 L. Roubalíková Composite materials Chemically bonded mixture of organic matrix and inorganic fillers Coupling agent – binds organic matrix and the filler together Homogenous distribution of the filler particles in the material Excellent mechanical properties Binding of the coupling agents to glass particles CH2=C(CH3)-R CH2=C(CH3)-R CH2=C(CH3)-R H O-Si H O-Si H O-Si Double bond -polymerizable Glass particle Importance of the components • matrix – a transfer mechanical loading on inorganic fillers, protects the filler against moisture • filler - a support of the material, carries the loading • coupling agents - a homogenous distribution of the filler in matrix Filler – material• Milled quartz • Aluminimum silicate glass • Silicium dioxide • Prepolymer (composite material is polymerized with high pressure in fabrics, than milled – particles of the fiiler are made of cured composite) • Complexes of microfiller (aglomerates) – e-g-. siliciumdioxide or zirconiumoxide Filler acc to the size of particles • Macrofiller ( size of particles µm ot tenth of µm ) • Mikroplnivo (hundredths od µm) • Nanofiller (nm) • Combination– hybrid ➢Conventional (µm ) ➢Microhybrid (hundredths od µm, µm) ➢Nanohybrid (hundredths od µm, µm, nm) Macrofiller • Particles µm or tenths of µm • Good mechanical resistance , abrasion resistance, bad polishability. Microfiller • Silicium dioxide (pyrogenous) • Particles hundreths µm Less amount of filler due to big surface Lower mechanical resistence, good polishability. Microfiller in complex particles • Prepolymer • Aglomerates - Higher amount of filler, good mechanical resistance, good polishability Nanoparticles • Particles 10 nm and less Special technology, size, shape and binding to monomer Today • Microhybrid or nanohybrid composites: Good mechanical properties, good polishability, propagation of cracks is minimized. Matrix Bis GMA – Bowen´s monomer • (2,2-bis[4-(2hydroxy-3-metakryloyloxypropoxy) • fenyl]propan) • Bis DMA • UDMA • TEGMA /triethylenglykoldimethacrylate • EGMA ethylenglykoldimethacrylate • e Bis –GMA • HDMA hexandioldimethacrylate Dimethacrylates - mixture of materials with high and lower molecular weight Matrix - modification - Acid modified resins (compomers) - Polysiloxan chains with polymerizable groups (ormocers) - Silorans (ring opening monomers) Coupling agent • G -methacryloxypropyltrimetoxysilan (A 174) Other components • Activator and initiator • Pigments • Fluorescents • Absorbers of light • Inhibitors Selfcuring composites • Tertiary amine Dibenzolyperoxide • Activator Initiator Light curing composites • Initiator and sometimes also activator • Camphorchinon CQ • Phenylpropandion PPP • Trimetylbenzoylphosphino xid TPO Camphorchinon (CQ) - initiator • Yellow colour • Activator is present: etyl-4-(N,N’-dimetylamino)benzoát (4EDMAB), N,N’-dimetylaminoetylmetakrylat (DMAEMA) • Light shades of composites: combination of CQ and other initiators. Composite materials – basic characteristics Matrix Filler Compressive strength Elasticity Polymerization shrinkage Polymerization stress Water sorption Classification of composite filling materials ➢ Size of the filler particles Macrofilled, microfilled (homogenous, non homogenous, hybrid) ➢ Matrix (monomers) Dimethacrylate, acid modifies, ormocers, silorans ➢ Viskosity (flowable, thick) History Dimetacrylates Bowen 1960 – Bowen´s monomer Buoconore 1955 – acid etching History •Fusayama 1979 Adhesion to dentin Yoshida. Nakabaiashi Van Meerbeck 35% - 37% phosphoric acid silica particles blue dye Adhesion • Mechanical adhesion • Specific adhesion - Intermolecular forces - Chemical binding Acid on aprismatic enamel Acid on prismatic enamel Bonding agent Adhesive system connects resin to enamel and dentin • Bond is a hydrophobic resin principally of the same composition as composite filling material but without the filler or with a small amount of filler. It works in enamel. In dentin primer is necessary before bond. Why? Dentin – special composition • More water – always wett • Less minerals • Low surface energy • Smear layer Composite is hydrophobic, we need hydrofilic substance Adhesive systems contain resin monomers • Hydrophobic monomers - bond works in enamel it does not work in dentin without primer • Amphiphilic monomers – hydrophobic + hydrophilic part - in primer Primer is necesssary for dentin. The hydrophillic part flows into dentin (tubules, spaces in collagen network) and keep the collagen network open, the hydrophobic part of primer binds to hydrophobic bond that flows into dentin pretreated with primerIf primer applied on enamel – residual of water can be removed. Adhesive systems contain resin monomers Primer: 4-META • HEMA • TEGMA • PENTA P • 5-NMSA • Bis-GMA Bond: Bis-GMA ot other dimetacrylates. Hydrophpobic. Dissolving agents • Aceton • Alcohol • Water • Water/alcohol Acid etching Rinsing Priming Bonding Acod etchin Rinsing Priming a bonding Selfetching priming Bonding Selfetching bonding) Clinically oriented classification of the adhesive systems acc to number of steps Srelfetching bonding agents TE – Total etch, ERA SE – Self etching SEA Two steps selfetching agents • Acidic hydrophilic primer – evaporation of the solvant, penetration, dissolving of the smear layer • Hydrofobic bond – sealing of the surface One step selfetching agents • More vulnerable bonding, risk of hydrolysis FAKT !!! Source: Dudek M. Adhezivní spoj a adhezivní systémy I. LKS 11/2013 Smear layer layer Dentin tubules pH of the adhesive system thickness of the hybrid layer surface of dentin smear layer impregnated resin tag with the adhesive system very mild acidic sea mild acidic sea acidic sea strong acidic sea Colagen fibers with interfibrilar and Instrafibrilar crystals od hydroxyapatite Colagen fibers with intrafibrilas crystals of hydrpoxyapatite only Colagen fibers without crystals of hydroxyapatites Zdroj obrázku: Dudek M. Adhezivní spoj a adhezivní systémy I. LKS 11/2013 ̶ Protection of collagen against hydrolysis as well as enzymatic degradation of collagen (due to activation of matrix metaloproteinasis) - Strong mineral acid id dangereous for good long term bonding - Clorhexidin for one minute can stabilize collagen Importance of hydroxyapatite Enzymatic degradation of collagen Factors affecting quality of bonding • Structure and composition of hard dental tissues • Quality of their surface – esp. presence of smear layer, contamination with moisture, saliva and blood • Configuration factor – C- factor • Mechanical loading of the adhesive connection • Oral environment and external chemical materials (tooth pastes, asntiseptics, bleaching agent rtc.) Monomer Light Polymerization Polymer Pre –gel Gel Post -gel Three phases Phases - Pre-gel – material is soft - Gel-point – material became hard - Post –gel – material is not soft, postgel shrinkage Photocopomosite 3,2mm 57 mm 3mm 8,5mm Photocomposite 102mm 48mm Selfcuring composite 434343 43mm 42mm ̶ Quality of the material ̶ C- factor ̶ Mode of application ̶ Mode of polymerization Polymerization stress depends on ̶ Quality of the material ̶ C- factor ̶ Mode of application ̶ Mode of polymerization Polymerization stress depends on 0 10 20 40 80 plnivo% pnutí el.modul polym.kontrakce High content of filler increases the modulus of elasticity High modulus of elasticity increases the polymerization stress High content of filler decreases the polymerization shrinkage Polym. Stress Modulus of elasticity Polymerization shrinkage ̶ Quality of the material ̶ C- factor ̶ Mode of application ̶ Mode of polymerization Polymerization stress depends on 5 2 1 Bonded area : Free area 1:1 and less - optimal ̶ Quality of the material ̶ C- factor ̶ Mode of application ̶ Mode of polymerization Polymerization stress depends on Mode of application • Incremental technique Layer by layer with big free surface • Importance of flowables Thin layer of flowable first –big free surface Good marginal adaptation Compensation of the stress of the other layers Bulk fill materials do not solve the problem with polymerization stress 1 2 3 Placement of the material Placement of the material • Photocomposite - Thin layer with the maximal free surface (with respect of Cfactor of each layer) - Combination of materials of various viscosity - GIC + photocomposit (two visits better) - Increment of cured material into the soft non cured material Consequences of high C- factor White line around the filling Sealing of the filling . Acid etching around the cavosurface margin, application of the unfilled resin ̶ Quality of the material ̶ C- factor ̶ Mode of application ̶ Mode of polymerization Polymerization stress depends on Fotokompozit 102mm 48mm Selfcuring material 434343 43mm 42mm ̶ Longer pre-gel phase is better for releasing of polymerization stress - Soft start - Combination of materials (selfcuring composite materials have longer pre gel phase) Duration of pre-gel phase Factor that influence the quality of bonding • Configuration factor – C- factor +polymerization stress • Structure and composition of hard dental tissues • Quality of their surface – esp. presence of smear layer, contamination with moisture, saliva and blood • Mechanical loading of the adhesive connection • Oral environment and external chemical materials (tooth pastes, asntiseptics, bleaching agent rtc.) Cpontemporary possibilities polymerization • Quarz halogen units (halogen lamp) • Plasma units • LED units (diode – monocgromatic light, need of more diods) • Laser (strictly monochromatic light) Polymerization units – output energy Quarz halogen LED (3.generation) Plasma 600 -800 mW/cm2 1000 -1800 mW/cm2 blue 50 – 100 mW/cm2 purple 1500 - 2000mW/cm2 Output energy and time of polymerization • Recomended power is 12000 – 16000 mJ/cm2 12 000 mWs/cm2 measured intensity mW/cm2 Time in seconds Usually 20 s Radiometer ois recommended Photoinitiators • Kafrchinon CQ • Phenylpropandion PPP • Trimetylbenzoylphosphinoxid TPO Absorbtion spectrum of fotoiniciators Photoinitiator Absorbtion spectrum (nm) Maximum (nm) CQ 440 - 500 470 PPD 380 – 430 400 TPO 350 - 410 380 Light conductor Small area – higher concentration of output energy, but bigger dispersion The average distance is 4 mm – 10 mm. Standard light conductor – more reliable for daily is Standardní a kónický světlovod Mode of curing • Continuous curing at a constant intensity level: 40s of 500 mW/cm2 • Continuous two step curing • 10 s 150 W/cm2 then 750 mW/cm2 • for remaining time • Two step ramp – low intensity level gradually increases (5-10s) to achieve a final high intensity • Puls delay • Low intensity short time, 100 - 300 mW/cm2unit is turn off. 3 min pause • Final curing 600 mW/cm2 • Othe factors for consideration • Shade • Increments towards dentin walls • Pulse delay technique is dedicated to the layer that contacts enamel Flowables • – marginální adaptation (material flows) • - small polymerization stress – importance in incremental technique • - block out of undercuts • - small cavities, corrections Composite materials with high viscosity • Small polymerization shrinkage • Hihg polymerization stress • Worse marginal adaptation Bulk fill - Application and curing in one bulk - Higher amount of fotoinitiators - Higher translucency - The problem with polymerization stress is not comlpetely solved Group of various materials: 1. Flowables 2. Condensables 3. Sonic Fill (KaVo) Sonic Fill Big bulk up to 5mm (less – 4 mm is recommended) Sonic „activation“ – vibration decrease viscosity Internal dispersion of light Long term expeerience? Factors that influence the quality of bonding • Structure and composition of hard dental tissues • Quality of their surface – esp. presence of smear layer, contamination with moisture, saliva and blood • Configuration factor – C- factor • Mechanical loading of the adhesive connection • Oral environment and external chemical materials (tooth pastes, asntiseptics, bleaching agent rtc.) Working procedure and variables affecting the bonding What affects the quality of bonding? Variables that affect quality of bonding 1) Etching Etching too long can etch too deep, making it difficult for the resins to reach sound tooth structure. 1.9µm Variables that affect quality of bonding 2) Drying dentin Over drying the dentin after etching can be very destructive to bond values with some adhesives. Variables that affect quality of bonding 3) Application time Too short of application time may not allow for proper volatilization of the solvents or complete resin hybridization. This is critical with self etching systems. Variables that affect quality of bonding 4) Thinning / drying Too thin of adhesive layer doesn’t allow for proper curing due to oxygen inhibition. Too thick and the adhesive may still contain solvents. O2 O2 O2 O2O2 O2 Air thin / Dry TO TRANSLUCENCY Variables that affect quality of bonding 5) Light curing Too short or insufficient light cure equals partially polymerized resins. Variables that affect quality of bonding 6) Composite Placement Improper adaptation of the composite to the adhesive can create voids at the bonding interface. Condenser Variables that affect quality of bonding 7) Contamination • Blood • Sulcular fluid • Saliva • etc… Variables that affect quality of bonding 8) Deteriorated product • Expired • Volatilized Indication of composite materials • Filling of all classes: • I., II. class: small to moderate restorations • III. Class • IV. Class • V. Class • Other factors for consideration: • Level of oral hygiene • Occlusal loading • Quality of hard dental tissues Other indication • Splinting • Postendo treatment (post and core) • Cementation (special materials) – adhesive cementation • Fissure sealing • Venners – direct, indirect Contraindication of composite materials • Bad level of oral hygiene • Large cavities in posterior teeth (alternative is amalgam or inlay/onlay, • Heavy occlusal stress (deep bite , bruxis) • Cavities out of enamel (esp. cervical area) • Social aspects Postendo – post and core Postendo using flowable and onlay • Flowable at the bottom • Composite onlay • Onlay after 8 years lenka.roubalikova@tiscali.cz