Presentation on theme: "Direct Polymeric Restorative Materials"— Presentation transcript:
1 Direct Polymeric Restorative Materials DHYG 113Restorative Dentistry I
2 ObjectivesDiscuss properties of restorative resins: polymerization shrinkage, coefficient of thermal expansion, and abrasion resistanceSummarize filler particle, matrix, and the coupling agent of a composite restorative materialExplain proper eye protection when using light-cured materialsExplain the meaning of ‘addition’ in addition polymerizationDescribe : depth of cure, addition of material in increments, inhibition by air, unreacted C=C bonds, shades, shortcomings of the matrixExplain the fillers found in dental composites: composition, size, amount, abrasion resistance, refractive index, clinical detection
3 Explain the difference between flowable and condensable composites Discuss the role of the dental hygienist in the placement and maintenance of pit and fissure sealantsDiscuss the use of a primer with pit and fissure sealantsDescribe preventive resin restoration and composite cementsAssess the positive and negative characteristics of light-cure and chemical-cure glass ionomer cementsDiscuss similarities between compomers, glass ionomers, and composites
4 MonomersFunctional group participates in polymerization (chemical) reactionCarbon-Carbon double bond (C=C)Free Radical – unpaired electronAddition polymerization – one monomer at a time is added to the chainInitiation – first step (formation of free radical)Heat activated -- Light activatedChemically activated -- Dual cure materials
6 Thermoplastic – can be heated and shaped PropagationSecond step in addition polymerizationTerminationFree radicals at ends of chain react (stops process)Exothermic reactionReleases heatThermoplastic – can be heated and shapedThermoset polymers – most dental resins
7 Working Time Polymerization can happen quickly Reaction must occur when desiredLight cured materialDelayed with inhibitor for chemical-curedHydroquinone (ex.) destroys first free radicalsWithout delay, the material would set up too fast
8 Shelf LifeLiquid components of acrylic resins are almost entirely monomersFree radical could polymerize entire containerManufacturers add inhibitor to monomer materials to prevent them from becoming a solid mass
9 Problems with Resins Polymerization shrinkage Coefficient of Thermal ExpansionHigh (can be 2-10 times greater than tooth)Problem with percolationLack strength & abrasion resistance
10 De-bonding Once desiccated, the de-bonding becomes very apparent Bouschlicher,Vargas,Boyer. Effect of composite type, light intensity,configuration factor and laser polymerisation on polymerisation contraction forces. Am J Dent 1997 Apr,10(2)88-96
11 Color Hue – dominant color of the object Red, blue, yellow (teeth are yellow to yellow-red)Value – refers to lightness of a colorScale of 1 – 10 (1=black, 10=white)Chroma – refers to intensity of colorScale of 1 – 10 (rich or pale)
12 Appearance Translucency – enamel at incisal edges Opacity – dentin affects light passing throughGingiva affects color at marginRubber damMatch shade before placing to get best results
13 Composites Dr. Raphael Bowen, 1960’s Fillers and Silane Coupling AgentsIndustrial: fiberglassFillers typically ceramic (silica) particlesSilane Coupling agents: work like soap to react with silicon and oxygen on the surface of the ceramic fillerComposite strength increases, polymerization shrinkage decreases, limits thermal expansion
14 Composite Components Matrix Monomer Diluent – added to control viscosityPolymerizes by Addition PolymerizationChemical cure – two paste systemLight cure – single paste material
15 Composite Polymer Dr. Bowen developed – for dental composites Combination of several monomersOligomer: Bifunctional since each C=C group can participate in formation of growing chainCross-linking = improved strengthBis-GMAMethyl methacrolate (most common)Triethelene glycol dimethacrylate
16 Fillers Originally quartz materials (sand) Engineered glass materials Size determines surface smoothnessMacrofill – largest size particles, rough textureMicrofill – 1970’s, polish smooth, appear similar to enamel, useful for Class III & V restorations due to modulus of elasticitySmall particle – 1980’s, 80-85% filledHybrid – late 1980’s, strong & abrasion resistant (Class I & III)
18 Composite restorations Composite restorations are shown in centric occlusion from the lingual aspect on the laboratory models.Laboratory models
19 Flowable Composites Class V restorations Micro preparations Extended fissure sealingAdhesive cementation of ceramic restorationsBlocking out cavity undercutsInitial (base) layer in any classificationResin coating technique
20 Self-Curing & Light Curing Resins Paste APaste BPasteMonomersInitiatorActivatorAcceleratorMixing A and B, or light curing the paste causes:Initiator + activator (acclerator) reactive initiatorReactive initiator + monomers reactive monomersReactive monomers + monomers polymers
21 Adhesives Dentin bonding systems Scotch Bond Multi Purpose EBS-Multi solvent-free adhesive system for the "Total-Etch" technique
22 Depth of Cure The thickness of composite cured by typical light source Penetration of curing light – only several mmDepends on time of light exposure, product, shade, and the lightIf material nearest to pulp is not cured, can result in sensitivityComposites placed in layers to prevent uncured material
23 Incremental Addition Placing composites in layers: Assures polymerizationAllows for shrinkage (normally about 2%)
24 Condensable Composites Filler particle inhibits sliding of filler particles by one anotherResults in “thicker, stiffer feel”
25 Placement of Composite Restoration Diagnose lesionDetermine shade neededIsolate areaCut cavity preparationPlace cavity liner if necessaryEtch, prime, and place adhesivePlace composite incrementally; cureFinish
26 Check proximal contacts Examine for voids and marginal defectsPolishRemove rubber damCheck occlusion
27 Sealant & Preventive Resins Sealants reduce caries in pits and fissuresEtch, then bond (light or chemical cured)Preventive resins: combination of sealant and composite restorationSuspicious pit is opened with a bur or air abrasionTooth is etched, primed, and adhesive placedPrepared pit is filled with hybrid compositeOther pits and fissures filled with sealantConservative – not a Class I preparation
28 Glass Ionomer Chemical cure – first adhesive restorative material Light-cure, late 1980’sPowder-liquid systems (acid-base setting reaction)Placed directly into cavity preparationAdvantages:Fluoride releasing – good for high caries risk, Class VAdhesiveLuting cements
29 Glass-ionomers Postoperative Sensitivity Reduced or Eliminated MasticatorypressureSecondarycariesShrinkageExpansionGLASS IONOMER CEMENTSFinely ground aluminosilicate glassLiquid is a polycarboxylate copolymerThe chemical reaction gives rise to a cross-linked gel matrixBonding to tooth tissue occurs between the polycarboxylate molecules and calcium on the surface of the tooth.There are other cements like:Zinc oxide eugenol cementsZinc polycarboxylate cementsForCementation of inlays, veneers, orthodontic bands and brackets, resin-bonded bridges etc.Postoperative Sensitivity Reduced or EliminatedChemically and Mechanically Bonds to Tooth StructureFlexes with Tooth, Cushions Occlusal ForcesOutstanding Fluoride Release Protects restoration from secondary decayConsistent results, Easy to Use
30 CompomersCombination of Glass Ionomer and Composite/Dentinal bonding materialsBond and set like compositesRelease fluoride like glass ionomersExample:3M F2000 tooth structure both react to temperature changes to the same degree and shows an elasticity comparable to microfill restoratives(following slides from 3M conference in South Africa)
31 Compomers "Dyract® AP etch cavities adhesive compomer placed setting
32 Class V CompomerFigure 1 - Class V defect in lower right central incisor. Incisal enamel abrasion points to abfraction as possible contributing cause.
33 Figure 2 - After cleaning, shade taking and preparation, the compomer primer is directly dispensed from the 3M Clicker system into the mixing well.
34 Figure 3 - After shortly mixing the liquids in the well with a brush, the same brush is used to apply the primer to the entire cavity.
35 Figure 4 - After 30 seconds the primer is gently air dried for 5-10 seconds
36 Figure 5 - The primeris light cured for 10 seconds
37 Figure 6 - After light curing the primer, the compomer can be applied Figure 6 - After light curing the primer, the compomer can be applied. Capsules are preferred because the material can be applied directly into the cavity
38 Figure 7 - A preformed matrix is put on the restorative prior to a 40 seconds light cure to facilitate contouring and finishing of the restoration.
39 Figure 8 - After the use of Sof-Lex finishing and polishing discs the end result shows a good color match and marginal adaptation.
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