DENTURE BASE RESINSDENTURE BASE RESINS
INDIAN DENTAL ACADEMYINDIAN DENTAL ACADEMY
Leader in continuing dental educationLea...
CONTENTSCONTENTS
• IntroductionIntroduction
• HistoryHistory
• ClassificationClassification
• RequirementsRequirements
• A...
• Resin impression trays and tray materialsResin impression trays and tray materials
• Resin teeth for prosthetic applicat...
IntroductionIntroduction
Synthetic polymers often termed as plastics are usedSynthetic polymers often termed as plastics a...
• Resins today occupy a prominent place in the spectrum ofResins today occupy a prominent place in the spectrum of
materia...
HistoryHistory
• Before 1880 AD dentures were fabricated from hard wood;Before 1880 AD dentures were fabricated from hard ...
• In 1909 Dr Leo Bakland discovered Phenol formaldehydeIn 1909 Dr Leo Bakland discovered Phenol formaldehyde
resin known a...
Classification of resinsClassification of resins
• Based on thermal behavior:Based on thermal behavior:
– Thermoplastic:Th...
– BranchedBranched
• Branched homopolymerBranched homopolymer  consist of same mer unitsconsist of same mer units
• Graf...
Spatial structure:Spatial structure:
There are 3 basic types of structures – linear, branched, and cross-linked.There are ...
The linearThe linear homopolymer has mer units of the same type.homopolymer has mer units of the same type.
And theAnd the...
• TheThe branched homopolymerbranched homopolymer consists of the same mer units,consists of the same mer units,
• whereas...
Chemistry of polymersChemistry of polymers
• Polymers are prepared by a process called polymerization,Polymers are prepare...
Addition polymerizationAddition polymerization
• Most dental resins are polymerized by a mechanism in whichMost dental res...
Stages in addition polymerizationStages in addition polymerization::
• InductionInduction:: For an addition polymerization...
• The polymerization process for dental resins is activated byThe polymerization process for dental resins is activated by...
• Light activatedLight activated:: In this system photons from a light sourceIn this system photons from a light source
ac...
• Chain transferChain transfer:: In this process, the active free radical ofIn this process, the active free radical of
gr...
Inhibition of addition polymerizationInhibition of addition polymerization
• The polymerization reactions are not likely t...
Step growth polymerizationStep growth polymerization
- It is a process in which polymerization is accompanied by- It is a ...
CopolymersCopolymers
• Polymer chains, which contain two or more different type ofPolymer chains, which contain two or mor...
Heat Activated Denture base resins:Heat Activated Denture base resins:
CompositionComposition
PowderPowder
Polymethyl meth...
Physical stagesPhysical stages;;
1.1.Sandy stageSandy stage: Little or no interaction occurs on a molecular: Little or no ...
Technical considerationsTechnical considerations
Compression molding techniquesCompression molding techniques
Injection mo...
Polymerization cyclesPolymerization cycles
• The recommended curing cycles are: -The recommended curing cycles are: -
– On...
Polymerization Via microwave energy:-Polymerization Via microwave energy:-
Poly methyl methacrylate resin can also be poly...
Chemically activated denture base resinsChemically activated denture base resins
compositioncomposition
LIQUIDLIQUID
• Met...
• The degree of polymerization achieved using chemicallyThe degree of polymerization achieved using chemically
activated r...
Technical considerations:Technical considerations:
• Chemically activated denture base resins are most often moldedChemica...
Processing considerationsProcessing considerations
• Following final closure of the denture flask, pressure must beFollowi...
Fluid resin techniques:-Fluid resin techniques:-
• These technique employees a pourable, chemically activatedThese techniq...
AdvantagesAdvantages
• Improved adaptation to underlying soft tissuesImproved adaptation to underlying soft tissues
• Decr...
Light activated denture base resins:Light activated denture base resins:
• This denture base materials consists of urethan...
Properties of denture resins:Properties of denture resins:
A.A. Methyl Methacrylate monomer:Methyl Methacrylate monomer:
I...
B.B. Poly (methyl methacrylate)Poly (methyl methacrylate)
1.1. Taste and odorTaste and odor::
Completely polymerized acryl...
4)4) Impact strength:Impact strength:
The impact strength of polyvinyl acrylic is about twice that ofThe impact strength o...
7) Modulus of elasticity:7) Modulus of elasticity:
Acrylic resins have sufficient stiffness (modulus of elasticityAcrylic ...
Porosity may be:Porosity may be:
• Internal porosityInternal porosity
• External porosityExternal porosity
Internal porosi...
SolubilitySolubility
The denture base resins are soluble in a variety of solvents.The denture base resins are soluble in a...
Crazing:Crazing:
Crazing is formation of surface cracks on the denture baseCrazing is formation of surface cracks on the d...
Creep:Creep:
Denture resins display viscoelastic behavior. In otherDenture resins display viscoelastic behavior. In other
...
Repair resins:Repair resins:
Repair materials are usually acrylic plastics of powder liquidRepair materials are usually ac...
RELININGRELINING
For relining a low polymerization temperature is desirable toFor relining a low polymerization temperatur...
Rebasing resin dentures:Rebasing resin dentures:
The steps required in denture rebasing are very similar to thoseThe steps...
Soft lining materials:Soft lining materials:
A soft (resilient) lining material may be defined as a softA soft (resilient)...
Resins as Maxillofacial materialsResins as Maxillofacial materials
Poly (methyl methacrylate) was once commonly used forPo...
Temporary crown and bridge resins:-Temporary crown and bridge resins:-
Are used to provide temporary coverage following to...
Occlusal splintsOcclusal splints
Occlusal splints are used in the treatment of patients withOcclusal splints are used in t...
Inlay patternsInlay patterns
Chemically accelerated acrylic is used to fabricate inlayChemically accelerated acrylic is us...
Polymers used as ImplantsPolymers used as Implants
Polymeric implants in the form of poly methyl methacrylate andPolymeric...
The use of polymers for osseointegrated implants is nowThe use of polymers for osseointegrated implants is now
confined to...
Resin CementsResin Cements
The composition of most current resin cements is similar to that ofThe composition of most curr...
The dual cure cements are two component systems andThe dual cure cements are two component systems and
require mixing in a...
Resin SealantsResin Sealants
The most common sealants are based on BIS-GMA resinThe most common sealants are based on BIS-...
Light cured sealants:Light cured sealants:
most sealants used today are light cured activated by amost sealants used today...
Self cured sealantsSelf cured sealants
The material is supplied as two component system; oneThe material is supplied as tw...
Athletic Mouth protectorAthletic Mouth protector
The use of athletic mouth protector in contact sports hasThe use of athle...
Review of literatureReview of literature
Re-enforcement of denturesRe-enforcement of dentures::
Journal of oral Rehabilita...
Chemical modifications of PMMA: The addition of rubberChemical modifications of PMMA: The addition of rubber
produces a re...
Reinforcement of PMMA resins by carbon fibers increasesReinforcement of PMMA resins by carbon fibers increases
its transve...
Mechanical properties of new denture resins polymerizedMechanical properties of new denture resins polymerized
by visible ...
ConclusionConclusion
Resins have been used extensively asResins have been used extensively as
restorative materials in pro...
ReferencesReferences
1.Science of dental materials-11th edition1.Science of dental materials-11th edition
2.Dental materia...
Thank youThank you
For more details please visitFor more details please visit
www.indiandentalacademy.comwww.indiandentala...
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Denture base resins /orthodontics website

  1. 1. DENTURE BASE RESINSDENTURE BASE RESINS INDIAN DENTAL ACADEMYINDIAN DENTAL ACADEMY Leader in continuing dental educationLeader in continuing dental education www.indiandentalacademy.comwww.indiandentalacademy.com www.indiandentalacademy.comwww.indiandentalacademy.com
  2. 2. CONTENTSCONTENTS • IntroductionIntroduction • HistoryHistory • ClassificationClassification • RequirementsRequirements • Application of resins in DentistryApplication of resins in Dentistry • Chemistry of polymersChemistry of polymers • Denture base acrylic resins • Properties of denture base resins • Repair resins • Reling and rebasing denture resins • Short term and long term soft denture www.indiandentalacademy.comwww.indiandentalacademy.com
  3. 3. • Resin impression trays and tray materialsResin impression trays and tray materials • Resin teeth for prosthetic applicationResin teeth for prosthetic application • Resin as Maxillofacial materialResin as Maxillofacial material • Temporary crown and bridge resinsTemporary crown and bridge resins • Occlusal splintsOcclusal splints • Inlay patternsInlay patterns • Resins used as implantsResins used as implants • Resin cementsResin cements • Resin sealantsResin sealants • Athletic mouth protectorAthletic mouth protector • ReviewReview • ConclusionConclusion www.indiandentalacademy.comwww.indiandentalacademy.com
  4. 4. IntroductionIntroduction Synthetic polymers often termed as plastics are usedSynthetic polymers often termed as plastics are used extensively in prosthetic dentistry. Before the introductionextensively in prosthetic dentistry. Before the introduction of acrylic polymers to dentistry in 1937, the principalof acrylic polymers to dentistry in 1937, the principal polymer used was vulcanized rubber for denture bases.polymer used was vulcanized rubber for denture bases. Polymers introduce since then have included vinyl acrylics,Polymers introduce since then have included vinyl acrylics, polystyrene, epoxies, polycarbonates, polyvinyl acetatepolystyrene, epoxies, polycarbonates, polyvinyl acetate polyethylene, cis and trans-poly isoprene, polysulfides,polyethylene, cis and trans-poly isoprene, polysulfides, silicones, polyethers, and poly acrylic acids.silicones, polyethers, and poly acrylic acids. www.indiandentalacademy.comwww.indiandentalacademy.com
  5. 5. • Resins today occupy a prominent place in the spectrum ofResins today occupy a prominent place in the spectrum of materials used in dental profession. They have earned thismaterials used in dental profession. They have earned this place on the basis of performance, plus the apparentlyplace on the basis of performance, plus the apparently unlimited ability of dental researchers, educators andunlimited ability of dental researchers, educators and clinicians to develop new techniques and materials to meetclinicians to develop new techniques and materials to meet specific needsspecific needs www.indiandentalacademy.comwww.indiandentalacademy.com
  6. 6. HistoryHistory • Before 1880 AD dentures were fabricated from hard wood;Before 1880 AD dentures were fabricated from hard wood; ivory and bone with natural teeth held by screws or otherivory and bone with natural teeth held by screws or other means.means. • In about 1855 vulcanite rubber was introduced as denture baseIn about 1855 vulcanite rubber was introduced as denture base material with porcelain mounted on them the vulcanite basematerial with porcelain mounted on them the vulcanite base material ruled the field of prosthetics for denture base materialmaterial ruled the field of prosthetics for denture base material nearly about 75yers.nearly about 75yers. • In 1868 Werley Hyatt prepared 1st organic plastic moldingIn 1868 Werley Hyatt prepared 1st organic plastic molding compound which was cellulose nitrate and popularly known ascompound which was cellulose nitrate and popularly known as “Celluloid”.“Celluloid”. www.indiandentalacademy.comwww.indiandentalacademy.com
  7. 7. • In 1909 Dr Leo Bakland discovered Phenol formaldehydeIn 1909 Dr Leo Bakland discovered Phenol formaldehyde resin known as “Bakelite”resin known as “Bakelite” • In 1924 Dr Stryker used Phenol formaldehyde for the purposeIn 1924 Dr Stryker used Phenol formaldehyde for the purpose of dentures.of dentures. • After 1932 mixtures of polymerized vinyl chloride and vinylAfter 1932 mixtures of polymerized vinyl chloride and vinyl acetate were also used as denture base.acetate were also used as denture base. • In 1937 Dr. Walter Wright introduce more satisfactory plasticIn 1937 Dr. Walter Wright introduce more satisfactory plastic denture base materials called methyl methacrylate resins.denture base materials called methyl methacrylate resins. • By 1965-1970 polymers of vinyl styrenes, polycarbonates,By 1965-1970 polymers of vinyl styrenes, polycarbonates, nylons, polyurethane and other have been investigated butnylons, polyurethane and other have been investigated but found suitable only for limited applicationfound suitable only for limited application www.indiandentalacademy.comwww.indiandentalacademy.com
  8. 8. Classification of resinsClassification of resins • Based on thermal behavior:Based on thermal behavior: – Thermoplastic:Thermoplastic: Polymers that may be softened byPolymers that may be softened by heating and solidified by cooling, the process beingheating and solidified by cooling, the process being repeatable.repeatable. – Thermosetting:Thermosetting: refers to plastics that solidify duringrefers to plastics that solidify during fabrication but cannot be softened by reheating.fabrication but cannot be softened by reheating. • Based on spatial structureBased on spatial structure:: – LinearLinear • Linear homopolymerLinear homopolymer  has mer units of same typehas mer units of same type • Random copolymer of linear typeRandom copolymer of linear type  has two merhas two mer units randomly distributed along the chainunits randomly distributed along the chain • Linear block copolymerLinear block copolymer  has segments or blockshas segments or blocks align the chain where the mer units are the samealign the chain where the mer units are the same www.indiandentalacademy.comwww.indiandentalacademy.com
  9. 9. – BranchedBranched • Branched homopolymerBranched homopolymer  consist of same mer unitsconsist of same mer units • Graft branched copolymerGraft branched copolymer  has one type mer unitshas one type mer units on the main chain and another mer for brancheson the main chain and another mer for branches – Cross linkedCross linked • Is made up of homopolymer cross-linked with aIs made up of homopolymer cross-linked with a single cross linking agent.single cross linking agent. • The spatial structure of polymers affects their flowThe spatial structure of polymers affects their flow propertiesproperties • In general cross-linked polymers flow at a higherIn general cross-linked polymers flow at a higher temperature than linear (or) branched polymers.temperature than linear (or) branched polymers. Another distinguishing feature of some cross-linkedAnother distinguishing feature of some cross-linked polymers is that they do not absorb liquids as readilypolymers is that they do not absorb liquids as readily as linear (or) branched.as linear (or) branched. www.indiandentalacademy.comwww.indiandentalacademy.com
  10. 10. Spatial structure:Spatial structure: There are 3 basic types of structures – linear, branched, and cross-linked.There are 3 basic types of structures – linear, branched, and cross-linked. www.indiandentalacademy.comwww.indiandentalacademy.com
  11. 11. The linearThe linear homopolymer has mer units of the same type.homopolymer has mer units of the same type. And theAnd the random polymerrandom polymer of the linear type has the two mer units randomlyof the linear type has the two mer units randomly distributed along the chain.distributed along the chain. TheThe linear block copolymerlinear block copolymer has segments or blocks along the chain where thehas segments or blocks along the chain where the mer units are the same.mer units are the same. www.indiandentalacademy.comwww.indiandentalacademy.com
  12. 12. • TheThe branched homopolymerbranched homopolymer consists of the same mer units,consists of the same mer units, • whereas thewhereas the graft branched copolymergraft branched copolymer consists of one type of mer unit onconsists of one type of mer unit on the main chain and another mer for the branches.the main chain and another mer for the branches. www.indiandentalacademy.comwww.indiandentalacademy.com
  13. 13. Chemistry of polymersChemistry of polymers • Polymers are prepared by a process called polymerization,Polymers are prepared by a process called polymerization, which consist of momeric units becoming chemically linkedwhich consist of momeric units becoming chemically linked together to form high molecular weight molecules.together to form high molecular weight molecules. • Most polymerization reactions fall in two basic typesMost polymerization reactions fall in two basic types – Addition polymerizationAddition polymerization – Condensation polymerization (step growth polymerization)Condensation polymerization (step growth polymerization) www.indiandentalacademy.comwww.indiandentalacademy.com
  14. 14. Addition polymerizationAddition polymerization • Most dental resins are polymerized by a mechanism in whichMost dental resins are polymerized by a mechanism in which monomers are added sequentially to end of growing chain.monomers are added sequentially to end of growing chain. Addition polymerization starts from as active center addingAddition polymerization starts from as active center adding one monomer at a time to rapidly form a chain.one monomer at a time to rapidly form a chain. www.indiandentalacademy.comwww.indiandentalacademy.com
  15. 15. Stages in addition polymerizationStages in addition polymerization:: • InductionInduction:: For an addition polymerization process to begin aFor an addition polymerization process to begin a source of free radical is required. Free radicals can be generatedsource of free radical is required. Free radicals can be generated by activation of radical producing molecules using a secondby activation of radical producing molecules using a second chemical, heat, visible light, U.V light or energy transfer fromchemical, heat, visible light, U.V light or energy transfer from another compound that acts like a free radical.another compound that acts like a free radical. • The most commonly employed initiator (for methyl methacrylateThe most commonly employed initiator (for methyl methacrylate resin) is benzoyl peroxide, which is activated rapidly between 50resin) is benzoyl peroxide, which is activated rapidly between 50 to 1000 C.to 1000 C. • Induction is the period during which initiator molecule becomesInduction is the period during which initiator molecule becomes energized and breaks down into free radicals followed by theseenergized and breaks down into free radicals followed by these radicals reacting with monomer molecule to initiate chain growth.radicals reacting with monomer molecule to initiate chain growth. This period is greatly influenced by purity of monomer molecule.This period is greatly influenced by purity of monomer molecule. Any impurity increases the length of the period by consuming theAny impurity increases the length of the period by consuming the activated initiator molecules higher the temperature, the moreactivated initiator molecules higher the temperature, the more rapid the formation of free radicals and consequently shorter therapid the formation of free radicals and consequently shorter the induction period.induction period. www.indiandentalacademy.comwww.indiandentalacademy.com
  16. 16. • The polymerization process for dental resins is activated byThe polymerization process for dental resins is activated by one of the three energy sources.one of the three energy sources. • HeatHeat • ChemicalsChemicals • LightLight • Heat activationHeat activation:: the free radicals liberated by heating benzylthe free radicals liberated by heating benzyl peroxide will initiate polymerization of methyl methacrylateperoxide will initiate polymerization of methyl methacrylate monomer.monomer. • Chemical ActivationChemical Activation:: system consists of two reactants.system consists of two reactants. • That when mixed together undergo a chemical reaction thatThat when mixed together undergo a chemical reaction that generates free radicals.generates free radicals. • Eg. Tertiary amine activator and benzyl peroxide initiator,Eg. Tertiary amine activator and benzyl peroxide initiator, which are mixed together to initiate polymerization of sowhich are mixed together to initiate polymerization of so called self, cured resins.called self, cured resins. www.indiandentalacademy.comwww.indiandentalacademy.com
  17. 17. • Light activatedLight activated:: In this system photons from a light sourceIn this system photons from a light source activate the initiator to generate free radicals that in turn canactivate the initiator to generate free radicals that in turn can initiate polymerization process. When this system wasinitiate polymerization process. When this system was introduced in dentistry U.V light was used. However becauseintroduced in dentistry U.V light was used. However because of concerns about the effect of U.V light on retina andof concerns about the effect of U.V light on retina and unpigmented oral tissues, its limited penetration depth, andunpigmented oral tissues, its limited penetration depth, and loss of intensity of U.V light source over time, initiatorloss of intensity of U.V light source over time, initiator systems where subsequently developed that are activated bysystems where subsequently developed that are activated by visible light.visible light. • PropagationPropagation: The resultant free radical-monomer complex: The resultant free radical-monomer complex than acts as a new free radical center when it approachesthan acts as a new free radical center when it approaches another monomer to form a dimer, which also becomes a freeanother monomer to form a dimer, which also becomes a free radical.radical. Theoretically the propagation reaction should continue withTheoretically the propagation reaction should continue with evolution of heat until all monomer has been changed toevolution of heat until all monomer has been changed to polymer. Actually the polymerization is never completepolymer. Actually the polymerization is never complete www.indiandentalacademy.comwww.indiandentalacademy.com
  18. 18. • Chain transferChain transfer:: In this process, the active free radical ofIn this process, the active free radical of growing chain is transferred to another molecule (Eg: Agrowing chain is transferred to another molecule (Eg: A monomer or inactive polymer chain) and a new free radical formonomer or inactive polymer chain) and a new free radical for further growth is created.further growth is created. • TerminationTermination: Addition polymerization reactions are most: Addition polymerization reactions are most often terminated by direct coupling of two free radical chainoften terminated by direct coupling of two free radical chain ends or by exchange of hydrogen atom from one growingends or by exchange of hydrogen atom from one growing chain to another. Chain termination can also result from chainchain to another. Chain termination can also result from chain transfer .transfer . www.indiandentalacademy.comwww.indiandentalacademy.com
  19. 19. Inhibition of addition polymerizationInhibition of addition polymerization • The polymerization reactions are not likely to result in aThe polymerization reactions are not likely to result in a complete exhaustion of the monomer, nor do they always formcomplete exhaustion of the monomer, nor do they always form polymer of high molecular weight. Such reactions arepolymer of high molecular weight. Such reactions are inhibited by:inhibited by: ImpuritiesImpurities: - an impurity can react with the activated initiator: - an impurity can react with the activated initiator or with an activated growing chain to prevent furtheror with an activated growing chain to prevent further growth.growth. • For example: the addition of small amount of commonFor example: the addition of small amount of common inhibitor such as hydroquinone to monomer inhibitsinhibitor such as hydroquinone to monomer inhibits spontaneous polymerization if no initiator is present, andspontaneous polymerization if no initiator is present, and retards the polymerization in the presence of an initiator.retards the polymerization in the presence of an initiator. – Oxygen: reacts rapidly with free radicals, and its presenceOxygen: reacts rapidly with free radicals, and its presence retards the polymerization reaction.retards the polymerization reaction. www.indiandentalacademy.comwww.indiandentalacademy.com
  20. 20. Step growth polymerizationStep growth polymerization - It is a process in which polymerization is accompanied by- It is a process in which polymerization is accompanied by repeated elimination of small molecules. The primaryrepeated elimination of small molecules. The primary compounds react often with the formation of by products suchcompounds react often with the formation of by products such as water, alcohols, halogen acids and ammonia. The formationas water, alcohols, halogen acids and ammonia. The formation of these by products is the reason step growth polymerizationof these by products is the reason step growth polymerization is called condensation polymerization.is called condensation polymerization. - In step growth polymerization, a linear chain- In step growth polymerization, a linear chain of repeated mer units is obtained by the step wise interof repeated mer units is obtained by the step wise inter molecular condensation or addition of reactive groups inmolecular condensation or addition of reactive groups in which bi functional or tri functional monomers are allwhich bi functional or tri functional monomers are all simultaneously activated, as opposed the activation of onesimultaneously activated, as opposed the activation of one monomer at a time in chain growth addition polymerization.monomer at a time in chain growth addition polymerization. www.indiandentalacademy.comwww.indiandentalacademy.com
  21. 21. CopolymersCopolymers • Polymer chains, which contain two or more different type ofPolymer chains, which contain two or more different type of monomeric units, are called copolymers. In order to improvemonomeric units, are called copolymers. In order to improve physical properties it is often advantageous to use two or morephysical properties it is often advantageous to use two or more chemically different monomers as starting materials. Thus thechemically different monomers as starting materials. Thus the polymer found may contain units of all the monomerspolymer found may contain units of all the monomers originally present.originally present. Types:-Types:- • Alternating copolymers:Alternating copolymers: In alternating copolymers differentIn alternating copolymers different mers are alternatively distributed along the polymer chain.mers are alternatively distributed along the polymer chain. • Random:Random: type of copolymer the different mers are randomlytype of copolymer the different mers are randomly distributed along the chain such as.distributed along the chain such as. • Block typeBlock type: Here identical monomeric units occur in relatively: Here identical monomeric units occur in relatively long sequences along main polymer chain.long sequences along main polymer chain. • Graft typeGraft type: Here sequences of one of the monomers area: Here sequences of one of the monomers area grafted onto the backbone of second monomer species.grafted onto the backbone of second monomer species. www.indiandentalacademy.comwww.indiandentalacademy.com
  22. 22. Heat Activated Denture base resins:Heat Activated Denture base resins: CompositionComposition PowderPowder Polymethyl methacrylatePolymethyl methacrylate Benzyl peroxide (initiator)Benzyl peroxide (initiator) Zinc or titanium oxide (opacifier)Zinc or titanium oxide (opacifier) Dibutyl phthalate (plasticizer)Dibutyl phthalate (plasticizer) Compounds of mercury sulfide, cadmium sulfide (Dyes)Compounds of mercury sulfide, cadmium sulfide (Dyes) LiquidLiquid Non-polymerized methyl methacrylateNon-polymerized methyl methacrylate Hydroquinone (inhibitor)Hydroquinone (inhibitor) Glycol dimethacrylate (Cross linking agent)Glycol dimethacrylate (Cross linking agent) Dibutyl phthalate (plasticizer)Dibutyl phthalate (plasticizer) The accepted polymer – monomer ratio is 3:1 by volume (or) 2:1 byThe accepted polymer – monomer ratio is 3:1 by volume (or) 2:1 by weight.weight. www.indiandentalacademy.comwww.indiandentalacademy.com
  23. 23. Physical stagesPhysical stages;; 1.1.Sandy stageSandy stage: Little or no interaction occurs on a molecular: Little or no interaction occurs on a molecular level. Consistency of mixture may be described as “course” orlevel. Consistency of mixture may be described as “course” or “grainy”.“grainy”. 2.2.Stringy stageStringy stage: During this stage monomer attacks the surface: During this stage monomer attacks the surface of individual polymer beads.of individual polymer beads. This stage is characterized by stringiness or stickiness when theThis stage is characterized by stringiness or stickiness when the material is touched or drawn apart.material is touched or drawn apart. 3.3.Dough like stageDough like stage: At molecular level increased no. of polymer: At molecular level increased no. of polymer chains enter solution. Hence a sea of monomer and dissolvedchains enter solution. Hence a sea of monomer and dissolved polymer. Clinically the mass behaves as pliable dough. It is nopolymer. Clinically the mass behaves as pliable dough. It is no longer tacky and does not adhere to surface of mixing vessellonger tacky and does not adhere to surface of mixing vessel or spatula. The mass is packed into mold at their stage.or spatula. The mass is packed into mold at their stage. 4.4.Rubbery stageRubbery stage: The monomer disappears by further: The monomer disappears by further penetration into the polymer and evaporation. The mass ispenetration into the polymer and evaporation. The mass is cohesive rubber like non-plastic and cannot be molded.cohesive rubber like non-plastic and cannot be molded. 5.5. Stiff stageStiff stage: upon standing for an extended period, the mixture: upon standing for an extended period, the mixture becomes stiff. This may be attributed to the evaporation ofbecomes stiff. This may be attributed to the evaporation of monomer.monomer. www.indiandentalacademy.comwww.indiandentalacademy.com
  24. 24. Technical considerationsTechnical considerations Compression molding techniquesCompression molding techniques Injection molding techniquesInjection molding techniques www.indiandentalacademy.comwww.indiandentalacademy.com
  25. 25. Polymerization cyclesPolymerization cycles • The recommended curing cycles are: -The recommended curing cycles are: - – One technique involves processing the denture bone resinOne technique involves processing the denture bone resin in a constant temperature water bath at 740C for 8 hrs orin a constant temperature water bath at 740C for 8 hrs or longer with not terminal boiling temperature.longer with not terminal boiling temperature. – A second technique consists of processing in a 740C waterA second technique consists of processing in a 740C water bath for 8 hrs and then increasing the temperature to 1000Cbath for 8 hrs and then increasing the temperature to 1000C for 1 hr.for 1 hr. – A third technique involves processing the resin at 740C forA third technique involves processing the resin at 740C for 2 hrs and then increasing temperature of water bath to2 hrs and then increasing temperature of water bath to 1000C and processing for 1 hr.1000C and processing for 1 hr. www.indiandentalacademy.comwww.indiandentalacademy.com
  26. 26. Polymerization Via microwave energy:-Polymerization Via microwave energy:- Poly methyl methacrylate resin can also be polymerizedPoly methyl methacrylate resin can also be polymerized using microwave energy. This technique employs a speciallyusing microwave energy. This technique employs a specially formulated resin and a non metallic flask. A conventionalformulated resin and a non metallic flask. A conventional microwave oven is used to supply the thermal energy requiredmicrowave oven is used to supply the thermal energy required for polymerization.for polymerization. Major advantage of this technique is speed with whichMajor advantage of this technique is speed with which polymerization is accomplished.polymerization is accomplished. The physical properties and fit of microwave resins areThe physical properties and fit of microwave resins are comparable to conventional resins.comparable to conventional resins. www.indiandentalacademy.comwww.indiandentalacademy.com
  27. 27. Chemically activated denture base resinsChemically activated denture base resins compositioncomposition LIQUIDLIQUID • Methyl metha acrylateMethyl metha acrylate • Dimethyl-p-toulidineDimethyl-p-toulidine • Dibutyl phthalateDibutyl phthalate • Glycol dimethaacrylateGlycol dimethaacrylate • hydroquinonehydroquinone POWDERPOWDER • Poly methyl metha acrylatePoly methyl metha acrylate • Other co polymersOther co polymers • Benzoyl peroxideBenzoyl peroxide • Mercury sulfateMercury sulfate • Cadmium sulfateCadmium sulfate • Dyed organic fillers andDyed organic fillers and inorganic particles.inorganic particles. www.indiandentalacademy.comwww.indiandentalacademy.com
  28. 28. • The degree of polymerization achieved using chemicallyThe degree of polymerization achieved using chemically activated resins is not as complete as that achieved using heatactivated resins is not as complete as that achieved using heat activated systems. This indicates that there is great amount ofactivated systems. This indicates that there is great amount of unreacted monomer in denture bases fabricated via chemicalunreacted monomer in denture bases fabricated via chemical activation. This unreacted monomer creates two majoractivation. This unreacted monomer creates two major difficulties. First it acts as a plasticizer those results indifficulties. First it acts as a plasticizer those results in decreased transverse strength of denture resin. Second thedecreased transverse strength of denture resin. Second the residual monomer serves as a potential tissue irritant therebyresidual monomer serves as a potential tissue irritant thereby compromising biocompatibility of denture bases. Fromcompromising biocompatibility of denture bases. From physical standpoint, chemically activated resins displayphysical standpoint, chemically activated resins display slightly less shrinkage than heat activated counter parts. Thisslightly less shrinkage than heat activated counter parts. This imparts greater dimensional accuracy to chemically activatedimparts greater dimensional accuracy to chemically activated resins. The color stability of chemically activated resinsresins. The color stability of chemically activated resins generally is inferior to the color stability of heat-activatedgenerally is inferior to the color stability of heat-activated resins. This property is related to presence of tertiary aminesresins. This property is related to presence of tertiary amines within the chemically activated resins.within the chemically activated resins. www.indiandentalacademy.comwww.indiandentalacademy.com
  29. 29. Technical considerations:Technical considerations: • Chemically activated denture base resins are most often moldedChemically activated denture base resins are most often molded using compression techniques. Therefore the mold preparation andusing compression techniques. Therefore the mold preparation and resin packing are essentially the same as for heat activated dentureresin packing are essentially the same as for heat activated denture resins.resins. • Polymer and monomer are mixed according to manufacturesPolymer and monomer are mixed according to manufactures directions and permitted to attain dough like consistency. Thedirections and permitted to attain dough like consistency. The working time for chemically activated resins is shorter than forworking time for chemically activated resins is shorter than for heat-activated materials. Therefore special attention must be paidheat-activated materials. Therefore special attention must be paid for consistency of material and rate of polymerization.for consistency of material and rate of polymerization. • A lengthy initiation period is desirable, since this providesA lengthy initiation period is desirable, since this provides adequate time for trial closure. One method form prolongingadequate time for trial closure. One method form prolonging initiation period is to decreases the temperature of resin mass.initiation period is to decreases the temperature of resin mass. This may be accomplished by refrigerating the liquid componentThis may be accomplished by refrigerating the liquid component and/ or mixing vessel before the mixing process. When theand/ or mixing vessel before the mixing process. When the powder and liquid are mixed the rate of polymerization processpowder and liquid are mixed the rate of polymerization process decreases. As a result the resin mass remains in dough stage for adecreases. As a result the resin mass remains in dough stage for a extended period and the working tune is increased.extended period and the working tune is increased. • Mold preparation and resin packing are accomplished in the sameMold preparation and resin packing are accomplished in the same manner as described for heat-activated resins.manner as described for heat-activated resins. www.indiandentalacademy.comwww.indiandentalacademy.com
  30. 30. Processing considerationsProcessing considerations • Following final closure of the denture flask, pressure must beFollowing final closure of the denture flask, pressure must be maintained throughout the polymerization process. Initialmaintained throughout the polymerization process. Initial hardening of resin will occur within 30 min of final flaskhardening of resin will occur within 30 min of final flask closure. However it is doubtful that polymerization isclosure. However it is doubtful that polymerization is complete at this point. To ensure complete polymerization thecomplete at this point. To ensure complete polymerization the flask should be held under pressure for a min of 3 hrs.flask should be held under pressure for a min of 3 hrs. • Resins polymerized via chemically activation generallyResins polymerized via chemically activation generally display 3% to 5% free monomer, whereas heat activated resinsdisplay 3% to 5% free monomer, whereas heat activated resins exhibit 0.2% to 0.5% free monomer.exhibit 0.2% to 0.5% free monomer. www.indiandentalacademy.comwww.indiandentalacademy.com
  31. 31. Fluid resin techniques:-Fluid resin techniques:- • These technique employees a pourable, chemically activatedThese technique employees a pourable, chemically activated resin for the fabrication of denture bases. The chemicalresin for the fabrication of denture bases. The chemical composition is similar to auto polymerized resins. Thecomposition is similar to auto polymerized resins. The principal difference is that the pour type of denture base resinsprincipal difference is that the pour type of denture base resins has higher molecular weight powder particles that are muchhas higher molecular weight powder particles that are much smaller and when they are mixed with monomer the resultantsmaller and when they are mixed with monomer the resultant mix is very fluid. Therefore referred to as fluid resins. Theymix is very fluid. Therefore referred to as fluid resins. They are used with a significantly lower powder-liquid ratio, whichare used with a significantly lower powder-liquid ratio, which ranges from 2:1 to 2:5:1.ranges from 2:1 to 2:5:1. www.indiandentalacademy.comwww.indiandentalacademy.com
  32. 32. AdvantagesAdvantages • Improved adaptation to underlying soft tissuesImproved adaptation to underlying soft tissues • Decreased probability of damage to prosthetic teeth andDecreased probability of damage to prosthetic teeth and denture bases during deflaskingdenture bases during deflasking • Reduced material costReduced material cost • Simplification of flasking, deflasking and finishing proceduresSimplification of flasking, deflasking and finishing procedures • DisadvantagesDisadvantages • Noticeable shift of prosthetic teeth during processingNoticeable shift of prosthetic teeth during processing • Air entrapment within the denture base materialAir entrapment within the denture base material • Poor bonding between denture base material and acrylic resinPoor bonding between denture base material and acrylic resin teethteeth • Technique sensitiveTechnique sensitive www.indiandentalacademy.comwww.indiandentalacademy.com
  33. 33. Light activated denture base resins:Light activated denture base resins: • This denture base materials consists of urethane dimethacrylateThis denture base materials consists of urethane dimethacrylate matrix, microfine silica, and higher molecular weight acrylicmatrix, microfine silica, and higher molecular weight acrylic monomers. Acrylic resin beads are included as organic fillers.monomers. Acrylic resin beads are included as organic fillers. Visible light is activator whereas camphoroquinone serves as theVisible light is activator whereas camphoroquinone serves as the initiator of polymerization.initiator of polymerization. • The single component denture base resin is supplied in sheet andThe single component denture base resin is supplied in sheet and rope forms and is packed in lightproof pouches to preventrope forms and is packed in lightproof pouches to prevent inadvertent polymerization. Denture base fabrication using a lightinadvertent polymerization. Denture base fabrication using a light activated resin in significantly different opaque investing mediaactivated resin in significantly different opaque investing media prevent the passage of light; therefore light activated resins cannotprevent the passage of light; therefore light activated resins cannot be fabricated in conventional manner. Instead teeth are arranged,be fabricated in conventional manner. Instead teeth are arranged, and the denture base is molded on an accurate cast. Subsequently,and the denture base is molded on an accurate cast. Subsequently, the denture base is exposed to high intensity visible light source forthe denture base is exposed to high intensity visible light source for an appropriate period. Following polymerization the denture base isan appropriate period. Following polymerization the denture base is removed from cast, finished and polished in conventional manner.removed from cast, finished and polished in conventional manner. www.indiandentalacademy.comwww.indiandentalacademy.com
  34. 34. Properties of denture resins:Properties of denture resins: A.A. Methyl Methacrylate monomer:Methyl Methacrylate monomer: It is clear, transparent, volatile liquid at roomIt is clear, transparent, volatile liquid at room temperature. It has a characteristic sweetish odor: -temperature. It has a characteristic sweetish odor: - The physical properties of monomer areThe physical properties of monomer are • Melting pointMelting point  480C480C • Boiling pointBoiling point  100.80C100.80C • DensityDensity  0.945gm/ ml at 200C0.945gm/ ml at 200C • Heat of polymerizationHeat of polymerization  12.9 K cal / mol12.9 K cal / mol • Volume shrinkage during polymerizationVolume shrinkage during polymerization  21%21% www.indiandentalacademy.comwww.indiandentalacademy.com
  35. 35. B.B. Poly (methyl methacrylate)Poly (methyl methacrylate) 1.1. Taste and odorTaste and odor:: Completely polymerized acrylic resin is tasteless and odorlessCompletely polymerized acrylic resin is tasteless and odorless 2.2. EstheticsEsthetics:: It is a clear transparent resin, which can be pigmented easily toIt is a clear transparent resin, which can be pigmented easily to duplicate oral tissues. It is also compatible with dyed synthetic fillers.duplicate oral tissues. It is also compatible with dyed synthetic fillers. 3.3. DensityDensity:: Polymer has a density of 1.19 gm/cm3.Polymer has a density of 1.19 gm/cm3. 2.2. Compressive and tensile strengthCompressive and tensile strength:: These materials are typically low in strength. However they haveThese materials are typically low in strength. However they have adequate compressive and tensile strength for complete or partialadequate compressive and tensile strength for complete or partial denture application.denture application. 3.3. Transverse strengthTransverse strength:: Measurements are used to a greater extent than either tensile (or)Measurements are used to a greater extent than either tensile (or) compressive strength, because the test more closely represents thecompressive strength, because the test more closely represents the type of loading in vivo. Under clinical conditions, heat curetype of loading in vivo. Under clinical conditions, heat cure polymethyl methacrylate is stiff enough not to flex unduly duringpolymethyl methacrylate is stiff enough not to flex unduly during function and recovers well from this degree of bending.function and recovers well from this degree of bending.www.indiandentalacademy.comwww.indiandentalacademy.com
  36. 36. 4)4) Impact strength:Impact strength: The impact strength of polyvinyl acrylic is about twice that ofThe impact strength of polyvinyl acrylic is about twice that of poly (methyl methacrylate). Addition of plasticizers may increase thepoly (methyl methacrylate). Addition of plasticizers may increase the impact of plastics.impact of plastics. 5)5) Hardness and abrasion resistance:Hardness and abrasion resistance: Heat cured acrylic resin: 18-20 KHNHeat cured acrylic resin: 18-20 KHN Self cured resin: 16-18 KHNSelf cured resin: 16-18 KHN Cross-linked poly (methyl methacrylate) is only slightly harderCross-linked poly (methyl methacrylate) is only slightly harder than regular poly (methyl methacrylate). The incorporation of fillersthan regular poly (methyl methacrylate). The incorporation of fillers may alter resistance to abrasion but the hardness of plastic matrixmay alter resistance to abrasion but the hardness of plastic matrix remains unchanged.remains unchanged. 6)6) Fatigue strength and fracture toughness:Fatigue strength and fracture toughness: Acrylic polymers show sensitivity. Over stressing of dentures onAcrylic polymers show sensitivity. Over stressing of dentures on deflasking must be avoided. Otherwise a small crack may be produceddeflasking must be avoided. Otherwise a small crack may be produced which will later propagate through the material. Similarly surface of awhich will later propagate through the material. Similarly surface of a denture must be smoothly polished. In an upper denture stressdenture must be smoothly polished. In an upper denture stress accumulation during chewing may occur at a point between centralaccumulation during chewing may occur at a point between central incisors. Here a notch to accommodate labial frenum frequentlyincisors. Here a notch to accommodate labial frenum frequently weakens the facial flange. Fatigue or midline fracture may occur if theweakens the facial flange. Fatigue or midline fracture may occur if the masticatory forces are relatively large. Fatigue strength increases withmasticatory forces are relatively large. Fatigue strength increases with a higher molecular weight and an increase in the plasticizer content.a higher molecular weight and an increase in the plasticizer content.www.indiandentalacademy.comwww.indiandentalacademy.com
  37. 37. 7) Modulus of elasticity:7) Modulus of elasticity: Acrylic resins have sufficient stiffness (modulus of elasticityAcrylic resins have sufficient stiffness (modulus of elasticity 2400 MPa) for use in complete and partial dentures. However when2400 MPa) for use in complete and partial dentures. However when compared with metal denture bases it is low.compared with metal denture bases it is low. 8) Polymerization shrinkage:8) Polymerization shrinkage: When methyl methacrylate monomer is polymerized to formWhen methyl methacrylate monomer is polymerized to form polymethyl methacrylate the density of the mass changes from 0.94 topolymethyl methacrylate the density of the mass changes from 0.94 to 1.19g/cm3. This change in density results in volumetric shrinkage of1.19g/cm3. This change in density results in volumetric shrinkage of 21% when a conventional heat activates resin is mixed at a suggested21% when a conventional heat activates resin is mixed at a suggested powder: liquid ratio about 1/3rd of resultant mass is liquid.powder: liquid ratio about 1/3rd of resultant mass is liquid. Consequently the volumetric shrinkage exhibited by polymerizedConsequently the volumetric shrinkage exhibited by polymerized mass should be approximately 7%.mass should be approximately 7%. In addition to volumetric shrinkage, linear shrinkage occurs.In addition to volumetric shrinkage, linear shrinkage occurs. Greater the linear shrinkage greater is the discrepancy observed in theGreater the linear shrinkage greater is the discrepancy observed in the initial set of dentures. Based on a projected volumetric shrinkage ofinitial set of dentures. Based on a projected volumetric shrinkage of 7% the linear shrinkage exhibited should be 2%. But the observed7% the linear shrinkage exhibited should be 2%. But the observed linear shrinkage is less then 1%linear shrinkage is less then 1% Processing shrinkage has been measured as 0.26% for aProcessing shrinkage has been measured as 0.26% for a representative chemically activated resin, compared with 0.53% for arepresentative chemically activated resin, compared with 0.53% for a representative heat activated resins.representative heat activated resins.www.indiandentalacademy.comwww.indiandentalacademy.com
  38. 38. Porosity may be:Porosity may be: • Internal porosityInternal porosity • External porosityExternal porosity Internal porosity:Internal porosity: is in the form of void or bubbles within the massis in the form of void or bubbles within the mass of polymerized acrylic. It is confined to thicker portion of theof polymerized acrylic. It is confined to thicker portion of the denture. Such porosity results from vaporization of unreacteddenture. Such porosity results from vaporization of unreacted monomers and low molecular wt polymers, when the temperature ofmonomers and low molecular wt polymers, when the temperature of a resin surpasses the boiling point of these species. In the center ofa resin surpasses the boiling point of these species. In the center of the thick portion the heat cannot be conducted away therefore thethe thick portion the heat cannot be conducted away therefore the temperature on the thicker portions may rise above the boiling pointtemperature on the thicker portions may rise above the boiling point of monomer.of monomer. Internal porosity can be avoided by using long and low temperatureInternal porosity can be avoided by using long and low temperature occurring cycles.occurring cycles. External porosity:External porosity: can occur due to two reasons:can occur due to two reasons: • Lack of homogeneityLack of homogeneity • Lack of adequate pressureLack of adequate pressure It can be avoided by using proper powder liquid ratio and mixingIt can be avoided by using proper powder liquid ratio and mixing it well. The mix is more homogenous in dough stage so packingit well. The mix is more homogenous in dough stage so packing should be done in dough stage.should be done in dough stage. www.indiandentalacademy.comwww.indiandentalacademy.com
  39. 39. SolubilitySolubility The denture base resins are soluble in a variety of solvents.The denture base resins are soluble in a variety of solvents. They are soluble in ketones, esters and aromatic chlorinatedThey are soluble in ketones, esters and aromatic chlorinated hydrocarbons. Alcohol causes crazing in some resins. A smallhydrocarbons. Alcohol causes crazing in some resins. A small amount of monomer may be leached out when stored in water.amount of monomer may be leached out when stored in water. The acrylic resins are virtually insoluble in fluids commonlyThe acrylic resins are virtually insoluble in fluids commonly encountered in oral cavity. The solubility of resins is low. Theencountered in oral cavity. The solubility of resins is low. The degree of solubility did not seem to affect the clinicaldegree of solubility did not seem to affect the clinical performance of dentures.performance of dentures. www.indiandentalacademy.comwww.indiandentalacademy.com
  40. 40. Crazing:Crazing: Crazing is formation of surface cracks on the denture baseCrazing is formation of surface cracks on the denture base resins. These cracks may be microscopic or macroscopic inresins. These cracks may be microscopic or macroscopic in size. In some cases it has a hazy (or) foggy appearance rathersize. In some cases it has a hazy (or) foggy appearance rather than cracks. In tinted resin, crazing imparts a whitishthan cracks. In tinted resin, crazing imparts a whitish appearance. In addition surface cracks predispose a dentureappearance. In addition surface cracks predispose a denture resin to fracture.resin to fracture. From physical standpoint, crazing may result from stressFrom physical standpoint, crazing may result from stress application or partial dissolution of a resin, for example attackapplication or partial dissolution of a resin, for example attack by a solvent. Tensile stresses are most often responsible forby a solvent. Tensile stresses are most often responsible for crazing in denture application. It is believed that crazing iscrazing in denture application. It is believed that crazing is produced by mechanical separation of individual polymerproduced by mechanical separation of individual polymer chains that occur on application of tensile stresses. Crazingchains that occur on application of tensile stresses. Crazing generally begins on the surface of a resin and is oriented atgenerally begins on the surface of a resin and is oriented at right angles to tensile forces. Micro cracks formed in thisright angles to tensile forces. Micro cracks formed in this manner subsequently progress internally.manner subsequently progress internally. Micro cracks or grazing produced as a result of solventMicro cracks or grazing produced as a result of solvent action are oriented randomly. Solvent induced crazingaction are oriented randomly. Solvent induced crazing generally results from prolonged contact with liquids such asgenerally results from prolonged contact with liquids such as ethyl alcohol.ethyl alcohol. www.indiandentalacademy.comwww.indiandentalacademy.com
  41. 41. Creep:Creep: Denture resins display viscoelastic behavior. In otherDenture resins display viscoelastic behavior. In other words, these materials act as rubbery solids that recover elasticwords, these materials act as rubbery solids that recover elastic deformation over time once the stresses induced in the resindeformation over time once the stresses induced in the resin have been eliminated. When a denture base resin is subjectedhave been eliminated. When a denture base resin is subjected to a sustained load the material exhibits an initial deflection orto a sustained load the material exhibits an initial deflection or deformation. If this load is not removed, additional plasticdeformation. If this load is not removed, additional plastic deformation may occur over time. This additional deformationdeformation may occur over time. This additional deformation is termed creep. The rate at which this progressiveis termed creep. The rate at which this progressive deformation occurs is termed creep rate. This rate may bedeformation occurs is termed creep rate. This rate may be elevated by increasing in temperature, applied load, residualelevated by increasing in temperature, applied load, residual monomer, and presence of plasticizer. Although creep rates formonomer, and presence of plasticizer. Although creep rates for heat activated and chemically activated resins are similar atheat activated and chemically activated resins are similar at low stresses, creep rates for chemically activated resinslow stresses, creep rates for chemically activated resins increases more rapidly as stress are raised.increases more rapidly as stress are raised. www.indiandentalacademy.comwww.indiandentalacademy.com
  42. 42. Repair resins:Repair resins: Repair materials are usually acrylic plastics of powder liquidRepair materials are usually acrylic plastics of powder liquid types similar to those used for denture base, and are usually eithertypes similar to those used for denture base, and are usually either heat cured (or) chemically cured. Light activated acrylic has alsoheat cured (or) chemically cured. Light activated acrylic has also been shown to be fast and effected repair materials.been shown to be fast and effected repair materials. One technique for making a repair requires holding orOne technique for making a repair requires holding or luting the broken pieces together with sticky wax, pouring theluting the broken pieces together with sticky wax, pouring the stone model on inside of the denture and investing the model andstone model on inside of the denture and investing the model and denture in flask.denture in flask. If a heat activated acrylic is used, the denture should beIf a heat activated acrylic is used, the denture should be completely flasked and curing should be carried out at acompletely flasked and curing should be carried out at a temperature no greater then 740c to 770c for 8hrs or longer.temperature no greater then 740c to 770c for 8hrs or longer. The use of chemically activated and light activated resinsThe use of chemically activated and light activated resins for repair does not require flasking. The procedure is rapid. Thefor repair does not require flasking. The procedure is rapid. The dimensional accuracy is maintained because not enough heat isdimensional accuracy is maintained because not enough heat is present during polymerization to cause warpage from release ofpresent during polymerization to cause warpage from release of stresses. The chemically activated resins however have astresses. The chemically activated resins however have a disadvantage of having a lower transverse strength.disadvantage of having a lower transverse strength.www.indiandentalacademy.comwww.indiandentalacademy.com
  43. 43. RELININGRELINING For relining a low polymerization temperature is desirable toFor relining a low polymerization temperature is desirable to minimize distortion of the remaining denture base. Hence, aminimize distortion of the remaining denture base. Hence, a chemically activated resin is usually chosen. The selected material ischemically activated resin is usually chosen. The selected material is mixed according to manufacturer’s recommendation, placed in themixed according to manufacturer’s recommendation, placed in the mould, compressed, and permitted to polymerize. In turn, the denturemould, compressed, and permitted to polymerize. In turn, the denture is recovered, finished and polished.is recovered, finished and polished. Relining also may be accomplished using resins that areRelining also may be accomplished using resins that are activated by heat, light and microwave energy. In all these instancesactivated by heat, light and microwave energy. In all these instances significant heat may be generated, and distortions of existing denturesignificant heat may be generated, and distortions of existing denture base is more likely.base is more likely. Some relining materials are marketed for home use.Some relining materials are marketed for home use. Unfortunately majority of patients do not posses adequate knowledgeUnfortunately majority of patients do not posses adequate knowledge to manipulate these materials adequately and correctly. As a result theto manipulate these materials adequately and correctly. As a result the use of such products may result in irreparable damage to oral tissues.use of such products may result in irreparable damage to oral tissues. The purchase and use of such products should be discouraged.The purchase and use of such products should be discouraged. www.indiandentalacademy.comwww.indiandentalacademy.com
  44. 44. Rebasing resin dentures:Rebasing resin dentures: The steps required in denture rebasing are very similar to thoseThe steps required in denture rebasing are very similar to those described for relining. An accurate impression of soft tissue isdescribed for relining. An accurate impression of soft tissue is obtained using existing dentures as custom tray. Subsequently aobtained using existing dentures as custom tray. Subsequently a stone cast is fabricated in the impression. The cast and the denturesstone cast is fabricated in the impression. The cast and the dentures are mounted in a device designed to maintain the correct verticalare mounted in a device designed to maintain the correct vertical and horizontal relationship between stone cast and the surface ofand horizontal relationship between stone cast and the surface of prosthetic teeth. The resultant assembly provides indices for theprosthetic teeth. The resultant assembly provides indices for the occlusal surface of prosthetic teeth after the indices have beenocclusal surface of prosthetic teeth after the indices have been established, the denture is removed and the teeth are separated formestablished, the denture is removed and the teeth are separated form the existing denture base. The teeth are repositioned in theirthe existing denture base. The teeth are repositioned in their respective indices and held in their original relationship to the castrespective indices and held in their original relationship to the cast while they are waxed to the desired formed. The completed toothwhile they are waxed to the desired formed. The completed tooth arrangement is sealed to the cast, and assembly is invested asarrangement is sealed to the cast, and assembly is invested as previously described. . Following elimination of the wax andpreviously described. . Following elimination of the wax and removal of the base plate resins is introduced into the mould cavity.removal of the base plate resins is introduced into the mould cavity. The material is subsequently processed. Consequently theThe material is subsequently processed. Consequently the prostheses consist of a new denture base in conjuncture with teethprostheses consist of a new denture base in conjuncture with teeth from patient’s previous denture.from patient’s previous denture.www.indiandentalacademy.comwww.indiandentalacademy.com
  45. 45. Soft lining materials:Soft lining materials: A soft (resilient) lining material may be defined as a softA soft (resilient) lining material may be defined as a soft elastic and resilient material forming all or part of the fittingelastic and resilient material forming all or part of the fitting (impression) surface of a denture. It usually acts as a cushion(impression) surface of a denture. It usually acts as a cushion between the hard denture base and tissues to reduce the masticatorybetween the hard denture base and tissues to reduce the masticatory forces transmitted by prosthesis to underlying tissues.forces transmitted by prosthesis to underlying tissues. The earliest soft lining material recorded (soft rubber) wasThe earliest soft lining material recorded (soft rubber) was used by Twitchell in 1869.No others are mentioned until 1940,whenused by Twitchell in 1869.No others are mentioned until 1940,when a soft natural rubber known as “velum” was used with vulcanite.a soft natural rubber known as “velum” was used with vulcanite. However this material had high water absorption, and it became foulHowever this material had high water absorption, and it became foul and ill fitting after a period of time. One of the first synthetic resinsand ill fitting after a period of time. One of the first synthetic resins used as soft lining material was poly (vinyl chloride), with which aused as soft lining material was poly (vinyl chloride), with which a plasticizer was necessary. In 1945 Mathews used poly (vinylplasticizer was necessary. In 1945 Mathews used poly (vinyl chloride), powder with a liquid di-n-butyl phthalate plasticizer as achloride), powder with a liquid di-n-butyl phthalate plasticizer as a soft liner. This material hardened in a short period of time becausesoft liner. This material hardened in a short period of time because the plasticizer leached out. Dioctyl phthalate was considered a betterthe plasticizer leached out. Dioctyl phthalate was considered a better plasticizer for poly (vinyl chloride) because the lining remained softplasticizer for poly (vinyl chloride) because the lining remained soft longer.Silicone rubber materials based on poly (dimethyl siloxane)longer.Silicone rubber materials based on poly (dimethyl siloxane) have been used as soft liners since 1958.have been used as soft liners since 1958. www.indiandentalacademy.comwww.indiandentalacademy.com
  46. 46. Resins as Maxillofacial materialsResins as Maxillofacial materials Poly (methyl methacrylate) was once commonly used forPoly (methyl methacrylate) was once commonly used for maxillofacial prostheses, and is still used occasionally to makemaxillofacial prostheses, and is still used occasionally to make artificial facial parts. The main disadvantages are that the acrylic isartificial facial parts. The main disadvantages are that the acrylic is hard and heavy and does not have the feel of skin.hard and heavy and does not have the feel of skin. Vinyl plastisols (plasticized vinyl resins) sometimes are used inVinyl plastisols (plasticized vinyl resins) sometimes are used in maxillofacial applications. Plastisols are thick liquids composed ofmaxillofacial applications. Plastisols are thick liquids composed of small vinyl particles dispersed in plasticizers. Colorants are added tosmall vinyl particles dispersed in plasticizers. Colorants are added to these materials to match individual skin tones. Major disadvantage ofthese materials to match individual skin tones. Major disadvantage of these materials is that they harden with age as a resultant of plasticizerthese materials is that they harden with age as a resultant of plasticizer migration U.V light also has as adverse effect on these materials. Formigration U.V light also has as adverse effect on these materials. For these reasons use of vinyl plastisols is limited.these reasons use of vinyl plastisols is limited. Polyurethane polymers are the most recent addition to materialsPolyurethane polymers are the most recent addition to materials used in maxillofacial prosthesis. The material is placed in stone orused in maxillofacial prosthesis. The material is placed in stone or metal mold and allowed to polymerize at room temperature althoughmetal mold and allowed to polymerize at room temperature although polyurethane prosthesis has a natural feel and appearance it ispolyurethane prosthesis has a natural feel and appearance it is susceptible to rapid deteriorationsusceptible to rapid deterioration www.indiandentalacademy.comwww.indiandentalacademy.com
  47. 47. Temporary crown and bridge resins:-Temporary crown and bridge resins:- Are used to provide temporary coverage following toothAre used to provide temporary coverage following tooth preparation for crown and bridges. Chemically activated plastics havepreparation for crown and bridges. Chemically activated plastics have become popular as temporary restorations. They have decreased thebecome popular as temporary restorations. They have decreased the use of polycarbonate crowns and aluminum shell.use of polycarbonate crowns and aluminum shell. Disadvantages of Resins used as temporary crown and bridgeDisadvantages of Resins used as temporary crown and bridge material;material; Heat generated during polymerization is harmful to the teethHeat generated during polymerization is harmful to the teeth Marginal opening can be caused by polymerization shrinkageMarginal opening can be caused by polymerization shrinkage Allergic reaction seen may be due to monomer componentAllergic reaction seen may be due to monomer component www.indiandentalacademy.comwww.indiandentalacademy.com
  48. 48. Occlusal splintsOcclusal splints Occlusal splints are used in the treatment of patients withOcclusal splints are used in the treatment of patients with temporomandibular joint pain or excessive bruxism. Thesetemporomandibular joint pain or excessive bruxism. These splints are made by the same technique used for dentures. Thesplints are made by the same technique used for dentures. The splint is waxed on a model of the patient’s teeth, usually thesplint is waxed on a model of the patient’s teeth, usually the maxilla. The model and wax pattern are invested in a denturemaxilla. The model and wax pattern are invested in a denture flask and the wax is boiled out. After cooling separating mediaflask and the wax is boiled out. After cooling separating media is painted on the mold and allowed to dry. A clear heatis painted on the mold and allowed to dry. A clear heat accelerated (activated) acrylic resin is packed into the moldaccelerated (activated) acrylic resin is packed into the mold and processed. Chemically activated acrylic resin is also usedand processed. Chemically activated acrylic resin is also used but less often. The properties of acrylic splints are similar tobut less often. The properties of acrylic splints are similar to those of heat activated acrylic materials .those of heat activated acrylic materials . www.indiandentalacademy.comwww.indiandentalacademy.com
  49. 49. Inlay patternsInlay patterns Chemically accelerated acrylic is used to fabricate inlayChemically accelerated acrylic is used to fabricate inlay patterns are direct post and cores. Commercial products arepatterns are direct post and cores. Commercial products are brightly pigmented and have good dimensional stability. Thebrightly pigmented and have good dimensional stability. The pattern is made by painting the powder – liquid onto the die orpattern is made by painting the powder – liquid onto the die or tooth in layers and allowing it to polymerized. Aftertooth in layers and allowing it to polymerized. After polymerization the pattern can be modified with stones andpolymerization the pattern can be modified with stones and burs. If necessary inlay wax may be added to complete theburs. If necessary inlay wax may be added to complete the patterns. Considerably larger burnout times must be used withpatterns. Considerably larger burnout times must be used with acrylic pattern.acrylic pattern. www.indiandentalacademy.comwww.indiandentalacademy.com
  50. 50. Polymers used as ImplantsPolymers used as Implants Polymeric implants in the form of poly methyl methacrylate andPolymeric implants in the form of poly methyl methacrylate and polytetra fluoro ethylene were first used in 1930s. The lowpolytetra fluoro ethylene were first used in 1930s. The low mechanical strength of the polymers has precluded their use asmechanical strength of the polymers has precluded their use as implant materials because of their susceptibility for mechanicalimplant materials because of their susceptibility for mechanical fracture during function. Also the physical properties of thefracture during function. Also the physical properties of the polymers are greatly influenced by changes in temperature,polymers are greatly influenced by changes in temperature, environment and composition and their sterilization can beenvironment and composition and their sterilization can be accomplished only by gamma irradiation or exposure to ethyleneaccomplished only by gamma irradiation or exposure to ethylene oxide gas. Contamination of these polymers is another disadvantage,oxide gas. Contamination of these polymers is another disadvantage, because electrostatic charges often attract dust and other impuritiesbecause electrostatic charges often attract dust and other impurities from the environment.from the environment. During the mid 1940’s methyl methacrylate was used forDuring the mid 1940’s methyl methacrylate was used for temporary acrylic implants to preserve the dissected space to receivetemporary acrylic implants to preserve the dissected space to receive a co-cr implant at a later time.a co-cr implant at a later time. www.indiandentalacademy.comwww.indiandentalacademy.com
  51. 51. The use of polymers for osseointegrated implants is nowThe use of polymers for osseointegrated implants is now confined to components. The intra mobile zirconia (IMZ)confined to components. The intra mobile zirconia (IMZ) implants are either titanium plasma sprayed or HA – coatedimplants are either titanium plasma sprayed or HA – coated (hydroxyapatite) and incorporate a polyoxymethylene (POM)(hydroxyapatite) and incorporate a polyoxymethylene (POM) intra mobile element. The IME is placed between prosthesisintra mobile element. The IME is placed between prosthesis and implant body to initiate mobility, stress relief, and shockand implant body to initiate mobility, stress relief, and shock absorption capability to mimic that of natural tooth. Whenabsorption capability to mimic that of natural tooth. When incorporated into the IMZ implant, the IME initiates theincorporated into the IMZ implant, the IME initiates the biomechanical function of the natural tooth unit, periodontalbiomechanical function of the natural tooth unit, periodontal ligament and alveolar bone.ligament and alveolar bone. www.indiandentalacademy.comwww.indiandentalacademy.com
  52. 52. Resin CementsResin Cements The composition of most current resin cements is similar to that ofThe composition of most current resin cements is similar to that of resin-based composite filling materials that is a resin matrix withresin-based composite filling materials that is a resin matrix with silane treated inorganic fillers. The fillers are those used insilane treated inorganic fillers. The fillers are those used in composites, that is silica or glass particles and / or colloidal silicacomposites, that is silica or glass particles and / or colloidal silica used in micro filled resins.used in micro filled resins. Resins cements have become attractive as a luting agent because ofResins cements have become attractive as a luting agent because of the development of direct filling resins with improved properties.the development of direct filling resins with improved properties. Chemically activated resin cements are supplied as two componentChemically activated resin cements are supplied as two component systems, consisting of either powder and liquid or two paste systems..systems, consisting of either powder and liquid or two paste systems.. Light curable cements are single composition systems just as areLight curable cements are single composition systems just as are the light curable resin based composites. They are indicated forthe light curable resin based composites. They are indicated for cementation of thin ceramic prosthesis, resin based prosthesis, andcementation of thin ceramic prosthesis, resin based prosthesis, and direct bonding of ceramic and plastic orthodontic brackets.direct bonding of ceramic and plastic orthodontic brackets. www.indiandentalacademy.comwww.indiandentalacademy.com
  53. 53. The dual cure cements are two component systems andThe dual cure cements are two component systems and require mixing in a manner similar to that used for chemicallyrequire mixing in a manner similar to that used for chemically activated systems. Chemical activation is very slow andactivated systems. Chemical activation is very slow and provides extended working time until the cement is exposed toprovides extended working time until the cement is exposed to curing light, at which point the cement hardens rapidly. It thencuring light, at which point the cement hardens rapidly. It then continues to gain strength over an extended period because ofcontinues to gain strength over an extended period because of chemically activated polymerization process. These dual curechemically activated polymerization process. These dual cure cements should not be used with light transmitting prosthesiscements should not be used with light transmitting prosthesis thicker than 2.5mm; any thing thicker than 2.5 mm should bethicker than 2.5mm; any thing thicker than 2.5 mm should be bonded with chemically curable cements.bonded with chemically curable cements. www.indiandentalacademy.comwww.indiandentalacademy.com
  54. 54. Resin SealantsResin Sealants The most common sealants are based on BIS-GMA resinThe most common sealants are based on BIS-GMA resin and are mainly light cured although some self-cured productsand are mainly light cured although some self-cured products are still available. The chemistry of BIS-GMA sealants isare still available. The chemistry of BIS-GMA sealants is same as that of composites. The principle difference is that thesame as that of composites. The principle difference is that the BIS-GMA sealants must be much more fluid to penetrate intoBIS-GMA sealants must be much more fluid to penetrate into pits, fissures, and etched areas produced on enamel, whichpits, fissures, and etched areas produced on enamel, which provide for retention of sealant. Three parts of viscous BIS-provide for retention of sealant. Three parts of viscous BIS- GMA are mixed with one part of diluent such as methylGMA are mixed with one part of diluent such as methyl methacrylate or triethylene glycol dimethacrylate to obtain amethacrylate or triethylene glycol dimethacrylate to obtain a reasonable low viscosity sealant. To provide stiffness to thereasonable low viscosity sealant. To provide stiffness to the material and improve wear resistance filler particles of fumedmaterial and improve wear resistance filler particles of fumed silica or silinated inorganic glasses can be added to form lowsilica or silinated inorganic glasses can be added to form low viscosity composites .viscosity composites . www.indiandentalacademy.comwww.indiandentalacademy.com
  55. 55. Light cured sealants:Light cured sealants: most sealants used today are light cured activated by amost sealants used today are light cured activated by a diaketone and an aliphatic amine. The sealant is applied to thediaketone and an aliphatic amine. The sealant is applied to the pit and fissure area with an appropriate applicator andpit and fissure area with an appropriate applicator and polymerization is accomplished by holding the light source 1polymerization is accomplished by holding the light source 1 to 2 mm from the surface and the sealant is exposed to lightto 2 mm from the surface and the sealant is exposed to light for 20 seconds. Sealants are applied in then sections such thatfor 20 seconds. Sealants are applied in then sections such that depth of cure is adequate. The advantage of using light curvedepth of cure is adequate. The advantage of using light curve sealant is that working time can be completely controlled bysealant is that working time can be completely controlled by the operator.the operator. www.indiandentalacademy.comwww.indiandentalacademy.com
  56. 56. Self cured sealantsSelf cured sealants The material is supplied as two component system; oneThe material is supplied as two component system; one component containing BIS-GMA resin and benzoyl peroxidecomponent containing BIS-GMA resin and benzoyl peroxide initiator and other containing BISGMA resin with 5% organicinitiator and other containing BISGMA resin with 5% organic amine accelerator. The two components are dispensed onto aamine accelerator. The two components are dispensed onto a suitable mixing surface and after adequate mixing are appliedsuitable mixing surface and after adequate mixing are applied directly to the tooth surface.directly to the tooth surface. The reaction (i.e polymerization reaction) is exothermicThe reaction (i.e polymerization reaction) is exothermic but the clinical effect is minimal because the material is placebut the clinical effect is minimal because the material is place in limited bulk. Air inclusion during mixing and insertion canin limited bulk. Air inclusion during mixing and insertion can be manifested clinically as surface voids, which can discolorbe manifested clinically as surface voids, which can discolor and retain plaque. To ensure optimum penetration, apply selfand retain plaque. To ensure optimum penetration, apply self cured sealant quickly after mixing.cured sealant quickly after mixing. www.indiandentalacademy.comwww.indiandentalacademy.com
  57. 57. Athletic Mouth protectorAthletic Mouth protector The use of athletic mouth protector in contact sports hasThe use of athletic mouth protector in contact sports has increased rapidly; they are routinely used in football, soccer, iceincreased rapidly; they are routinely used in football, soccer, ice hockey, basketball, wrestling, field hockey, softball and other sports.hockey, basketball, wrestling, field hockey, softball and other sports. This increase in use is justified by studies that showed that 38% ofThis increase in use is justified by studies that showed that 38% of participants in sports sustained orofacial injuries and only 15% ofparticipants in sports sustained orofacial injuries and only 15% of those injured were wearing a mouth protector at the time of injury.those injured were wearing a mouth protector at the time of injury. Injuries to teeth from trauma caused by athletic activity have involvedInjuries to teeth from trauma caused by athletic activity have involved pulpits, pulpal necrosis, replacement resorption, internal hemorrhage,pulpits, pulpal necrosis, replacement resorption, internal hemorrhage, pulp canal obliteration and inflammatory resorption.pulp canal obliteration and inflammatory resorption. Stock, mouth formed and custom mouth protector are three typesStock, mouth formed and custom mouth protector are three types available. Custom made mouth protectors are usually vacuum formedavailable. Custom made mouth protectors are usually vacuum formed from sheets of thermoplastic polymer (vinyl acetate – ethylenefrom sheets of thermoplastic polymer (vinyl acetate – ethylene copolymers). The advantage of custom made mouth protectors arecopolymers). The advantage of custom made mouth protectors are ;Excellent fit, Comfortable, Ease of speaking, Durability.;Excellent fit, Comfortable, Ease of speaking, Durability. These qualities are poor for stock protectors and poor to good forThese qualities are poor for stock protectors and poor to good for mouth formed protector. Inspite of the advantages of custom mademouth formed protector. Inspite of the advantages of custom made protectors they are not as common as stock or mouth formedprotectors they are not as common as stock or mouth formed protectors because of high cost.protectors because of high cost.www.indiandentalacademy.comwww.indiandentalacademy.com
  58. 58. Review of literatureReview of literature Re-enforcement of denturesRe-enforcement of dentures:: Journal of oral Rehabilitation 1999 (26)Journal of oral Rehabilitation 1999 (26) The material most commonly used for fabrication of completeThe material most commonly used for fabrication of complete dentures is poly (methylmethacrylate). Despite its popularity indentures is poly (methylmethacrylate). Despite its popularity in meeting esthetic demands it is still far from ideal in fulfillingmeeting esthetic demands it is still far from ideal in fulfilling mechanical requirements of prosthesis. The fracture of dentures maymechanical requirements of prosthesis. The fracture of dentures may be due to mechanical properties of acrylic resin or may be due tobe due to mechanical properties of acrylic resin or may be due to multiplicity of factors leading to failure of denture base material.multiplicity of factors leading to failure of denture base material. Generally, there are three routes, which have been investigated toGenerally, there are three routes, which have been investigated to improve the impact properties of PMMA.improve the impact properties of PMMA. 1. Development of alternative of an alternative material1. Development of alternative of an alternative material Chemical modification of PMMA such as addition of a rubber graftChemical modification of PMMA such as addition of a rubber graft copolymercopolymer Reinforcement of PMMA with carbon fibers, glass fibers and ultraReinforcement of PMMA with carbon fibers, glass fibers and ultra high modulus polyethylene.high modulus polyethylene. The various alternatives developed where: polyamides, epoxyThe various alternatives developed where: polyamides, epoxy reins, polystyrene, vinyl acrylic, rubber graft copolymers andreins, polystyrene, vinyl acrylic, rubber graft copolymers and polycarbonates and nylon.polycarbonates and nylon. www.indiandentalacademy.comwww.indiandentalacademy.com
  59. 59. Chemical modifications of PMMA: The addition of rubberChemical modifications of PMMA: The addition of rubber produces a resin that consists of a matrix of PMMA within which isproduces a resin that consists of a matrix of PMMA within which is dispersed interpenetrating network of rubber and PMMA. Adispersed interpenetrating network of rubber and PMMA. A developed crack will propagate through the PMMA but willdeveloped crack will propagate through the PMMA but will decelerate at rubber base interface. The objective of rubberdecelerate at rubber base interface. The objective of rubber reinforced or high impact resin is that they absorb greater amountreinforced or high impact resin is that they absorb greater amount of energy at a higher strain rate before fracture than the standardof energy at a higher strain rate before fracture than the standard resins. A problem is that the impact strength is often improved atresins. A problem is that the impact strength is often improved at the expense of the Young’s modulus producing a denture base withthe expense of the Young’s modulus producing a denture base with increased impact strength but which is too flexible.increased impact strength but which is too flexible. The addition of rubber to PMMA as a method of re-The addition of rubber to PMMA as a method of re- enforcement is to date the most successful and widely accepted andenforcement is to date the most successful and widely accepted and is alternative to the conventional PMMA resin. However, the highis alternative to the conventional PMMA resin. However, the high cost of upto 20 times that of conventional resins, restricts by iscost of upto 20 times that of conventional resins, restricts by is routine use.routine use. www.indiandentalacademy.comwww.indiandentalacademy.com
  60. 60. Reinforcement of PMMA resins by carbon fibers increasesReinforcement of PMMA resins by carbon fibers increases its transverse strength 50% compared to un-reinforced acrylicits transverse strength 50% compared to un-reinforced acrylic resin specimen. But this method is rarely used due to difficultyresin specimen. But this method is rarely used due to difficulty in handling characteristics of the fibers and their precisein handling characteristics of the fibers and their precise placement in resin, problems in polishing, poor esthetics dueplacement in resin, problems in polishing, poor esthetics due to black color the fibers impart on dentures, potential toxicityto black color the fibers impart on dentures, potential toxicity of carbon and development of alternative methods ofof carbon and development of alternative methods of reinforcement.reinforcement. The incorporation of glass fibers produced an increase inThe incorporation of glass fibers produced an increase in strength and decrease in fatigue weakening of PMMA resin. Itstrength and decrease in fatigue weakening of PMMA resin. It decreases density and impact strength.decreases density and impact strength. The reinforcement of PMMA resin with polyethylene in formThe reinforcement of PMMA resin with polyethylene in form of woven mat is satisfactory however the fabrication ofof woven mat is satisfactory however the fabrication of denture by this method is time consuming and prohibits isdenture by this method is time consuming and prohibits is routine use in dental laboratory.routine use in dental laboratory. www.indiandentalacademy.comwww.indiandentalacademy.com
  61. 61. Mechanical properties of new denture resins polymerizedMechanical properties of new denture resins polymerized by visible light, heat and microwaveby visible light, heat and microwave:: The International Journal of Prosthodontics 1992The International Journal of Prosthodontics 1992 Properties of resins polymerized by visible light, microwaveProperties of resins polymerized by visible light, microwave energy, using a water bathenergy, using a water bath Were measured, the new resins were harder and less flexibleWere measured, the new resins were harder and less flexible and had lower impact strength then did the heat –polymerizedand had lower impact strength then did the heat –polymerized resin. The light activated urethane dimethacrylate resin wasresin. The light activated urethane dimethacrylate resin was least flexible. Microwave polymerization improved theleast flexible. Microwave polymerization improved the modulus of elasticity, decreases the impact strength. Themodulus of elasticity, decreases the impact strength. The rubber modified resin luconite had the greatest impactrubber modified resin luconite had the greatest impact strength.strength. www.indiandentalacademy.comwww.indiandentalacademy.com
  62. 62. ConclusionConclusion Resins have been used extensively asResins have been used extensively as restorative materials in prosthodontics,restorative materials in prosthodontics, especially the polymethyl methacrylate resinsespecially the polymethyl methacrylate resins which is used in fabrication of completewhich is used in fabrication of complete dentures. Though the material is far from idealdentures. Though the material is far from ideal in fulfilling the mechanical requirements ofin fulfilling the mechanical requirements of prosthesis, it is the combination of virtues ratherprosthesis, it is the combination of virtues rather than single desirable property that accounts forthan single desirable property that accounts for its popularity and usageits popularity and usage www.indiandentalacademy.comwww.indiandentalacademy.com
  63. 63. ReferencesReferences 1.Science of dental materials-11th edition1.Science of dental materials-11th edition 2.Dental materials properties and manipulation-11th edition2.Dental materials properties and manipulation-11th edition 3.Anderson’s applied dental materials-John F.McCabe, 6th3.Anderson’s applied dental materials-John F.McCabe, 6th editionedition 4.Notes on dental materials-E.C.Combe, 6th edition4.Notes on dental materials-E.C.Combe, 6th edition 5. The International Journal of Prosthodontics - Review-Soft5. The International Journal of Prosthodontics - Review-Soft lining materials in prosthetic dentistrylining materials in prosthetic dentistry 6.Journal of oral rehabilitation- review- The reinforcement of6.Journal of oral rehabilitation- review- The reinforcement of dentures.dentures. 7. The International Journal of Prosthodontics – Review-7. The International Journal of Prosthodontics – Review- Mechanical properties of new denture resins polymerizedMechanical properties of new denture resins polymerized by visible light, heat and microwaveby visible light, heat and microwave www.indiandentalacademy.comwww.indiandentalacademy.com
  64. 64. Thank youThank you For more details please visitFor more details please visit www.indiandentalacademy.comwww.indiandentalacademy.com www.indiandentalacademy.comwww.indiandentalacademy.com

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