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Prosthodontic materials/prosthodontic courses

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Prosthodontic materials/prosthodontic courses

  1. 1. Prosthodontic Materials INDIAN DENTAL ACADEMY Leader in continuing Dental Education
  2. 2. Gypsum Products – Dental Plaster, Dental stone Impression Materials - Impression Compound, Zinc Oxide Eugenol, Hydrocolloids, Elastomers Restorative Materials – Dental Amalgam, Composite, Glass Ionomer Resins Waxes
  3. 3. The gypsum products used for different purposes such as: i) They are used to take imp of edentulous mouths. ii) To mount casts. iii) Used as dental stone to form a die that duplicates the oral anatomy when poured into any type of impressions. iv) As a binder for silica for Au casting investments, for soldering investment & investment for low melting Ni-Cr alloy.
  4. 4. Depending on the methods of calcination diff. forms of hemihydrates are formed such as : 1.)Dental plaster or beta hemihydrate 2.)dental stone or alpha hemihydrate 3.)improved stone or densite
  5. 5. 1.Dental plaster 2.Dental stone 3.Improved stone 4.Impression plaster 5.Dental casting investment
  6. 6. CLASSIFICATION ADA specification number 25 Type I – Impression plaster Type II – Dental plaster Type III – Dental stone of medium strength stone Type IV – Improved stone or high strength stone Type V – Dental stone, high strength, high expansion.
  7. 7. Impression materials Elastic Chemical reactions Irreversible Alginate Elastomers Polysulphides Polyethers Condensation silicon Addition silicon Temperature change Reversible Agar hydrocolloid Chemical reactions Irreversible Plaster of Paris ZnO Eugenol Temperature change Reversible Impression compound Waxes Rigid / Inelastic
  8. 8. ZINC OXIDE EUGENOL IMPRESSION PASTES Used for edentulous mouths is a rigid or inelastic impression materials that hardens by chemical reaction After chemical reaction a relatively hard mass is formed that possess certain medical advantages as well as mechanical usefulness in certain dental operations. Limitations Inability to accurately record undercuts Fracture when withdrawn from undercut Gross distortions due to plastic flow if used in undercut
  9. 9. Uses • Cementing medium • surgical dressing • Temporary filling materials • Root canal filling • Bite registration • Temporary relining materials for dentures • An impression materilas for edentulous mouths
  10. 10. IMPRESSIONS COMPOUND Also called as modelling plaster.It is a thermoplastic materials ,it is a rigid,reversible impression materials which sets by chemical change. Uses - making an impression of the edentulous ridge. -Stablizes matrix band. -For single tooth impression
  11. 11. WAX AS AN IMPRESSION MATERIAL wax is used in some corrective impression techniques in partial and complete denture prosthesis. Impression wax are available with variety of softening temperature. Used for functional impression and also in extending the border of the denture base when necessary .
  12. 12. ELASTIC Material susceptible to being stretched compressed or distorted and then tending to resume the original shape. Elastic impression materials are capable of accurately reproducing both the hard and the soft structures of the mouth including the undercut areas and interproximal spaces
  13. 13. ADVANTAGE OF ELASTIC IMPRESSION MATERIAL OVER RIGID IMPRESSION MATERIAL Elastic impression material can be used in both dentulous and edentulous cases with undercuts. The distortion of elastic impression material when removed from an undercut is minimal.
  14. 14. CLASSIFICATION OF ELASTIC IMPRESSION MATERIAL 1. REVERSIBLE HYDROCOLLOIDS # Agar 2. IRREVERSIBLE HYDROCOLLOIDS # Alginate 3. ELASTOMERIC IMPRESSION MATERIAL # Polysulphide # Condensation polymerizing silicon # Poly ether # Addition polymerizing silicon
  15. 15. AGAR Agar is a organic hydrophilic colloid (polysaccharide) extracted from a certain type of sea weed. It is a sulphuric ester of a linear polymer of galactose.
  16. 16. IRREVERSIBLE HYDROCOLLOID-ALGINATE The chief active ingredient is one of the soluble alginates such as sodium potassium or atriethonalamine alginate. When mixed with water they form a viscous sol. Calcium sulfate dihydrate is used as a reactor. It reacts with the soluble alginate to form a insoluble calcium alginate gel.
  17. 17. TYPES 1. Type I - fast setting 2. Type II - Normal setting
  18. 18. MODE OF SUPPLY It is supplied as a powder that is packed In bulk or in tins or in sachets. In pre-weighed individual containers A plastic scoop is supplied for dispensing the bulk powder and a plastic cylinder is supplied for measuring the water required for the bulk or the pre-weighed alginate powder.
  19. 19. Elastomers refers to a group of rubber polymers which are either chemically or physically crosslinked , easily stretched and rapidly recover to their original dimension when the applied stress is released. Chemically there are four kinds of elastomers Polysulfide Condensation silicon Polyether Addition silicon
  20. 20. ADVANTAGES AND DISADVANTAGES OF CONDENSATION SILICONES COMPARED WITH POLYSULFIDE MATERIALS ADVANTAGES Adequate working and setting time Pleasant odor and no staining Adequate tear strength Better elastic properties on removal Less distortion on removal DISADVANTAGES Adequate accuracy if poured immediately Poor dimensional stability Potential for significant distortion Putty-wash method is technique sensitive  Slightly more expensive Poor to adequate
  21. 21. Advantages and Disadvantages of Addition Silicones Compared with Polysulfide Materials ADVANTAGES DISADVANTAGES Shorter setting time Hydrogen gas evolution in some materials Easy to mix-automatic mixing devices need careful handling and a very dry field Adequate tear strength more expensive, especially with automatic mixing device Extremely high accuracy Undetectable distortion on removal Dimensionally
  22. 22. Advantages and Disadvantages of Polyethers Compared with Polysulfides Advantages Disadvantages Fast working and setting times Adequate accuracy if poured immediately Adequate tear strength Poor dimensional stability Less hydrophobic- better wetting Clean but tastes bad Less distortion on removal Stiffness requires blocking undercuts Long shelf life Slightly more expensive
  23. 23. Synthetic Resins
  24. 24.  Synthetic  resins  are  often  called  plastics.  A  plastic  material is  a  substance that a although  dimensionally stable in  normal use was plastic at some stage of manufacture. APPLICATIONS OF RESINS IN DENTISTRY Synthetic  resins  are  used  in  a  variety  of  dental  applications.  Typical uses include the following  •        Dentures (bases, liners, and artificial teeth) •        Cavity-filling materials ("composites") •        Sealants •        Impression materials •        Equipment (mixing bowls) •        Cements (resin-based)
  25. 25. CLASSIFICATION . Based on their thermal behaviour, they can be divided into   Thermoplastic    Thermosetting polymers  Depending on whether they soften when heated.A third group of  polymeric materials are the elastomers.
  26. 26. MMethyl Methacrylate MMethyl methacrylate is a transparent liquid at room temperature with  the following physical properties: •        Molecular weight = 100 •        Melting point = —48° C •        Boiling point = 100.8° C  •        Density = 0.945 g/mL at 20° C •        Heat of polymerization =12.9 kcal/mol MMethyl methacrylate exhibits a high vapor pressure and is an excellent  organic solvent. Although the polymerization of methyl methacrylate can  be  initiated  by  visible  light,  ultraviolet  light,  or  heat,  it  is  commonly  polymerized in dentistry by the use of a chemical initiator,  A A volume shrinkage of 21% occurs during the polymerization of the  pure methyl methacrylate monomer  .
  27. 27.                   Poly(methyl Methacrylate) Poly(methyl methacrylate) is a transparent resin of remarkable  clarity; it transmits light in the ultraviolet range to a wavelength of  250 nm. It is a hard resin with a Knoop hardness number of 18 to 20.  It has a tensile strength approx-imately 60 MPa, a density of 1.19   g/cm3 ,  and  a  modulus  of elasticity of approximately 2400 MPa. It is chemically stable to heat and softens at 125° C, and it can be  molded as a thermoplastic material. Between 125° and 200° C,  depolymerization takes place. At approximately 450° C, 90% of  the polymer depolymerizes to form the monomer
  28. 28. Amalgam: its an alloy of mercury with other metals. Silver amalgam has a silvery grey metallic appearance and mainly used for posterior restorations. Amalgam
  29. 29. Classification of amalgam alloys 1.According to particle shape a.Spherical shaped b.Irregular surface spheres (spheroidal shaped) c. Non-spherical – irregular shaped (Lathe cut) d.Dispersed (spherical + lathe cut) 1.According to particle size a.Micro cut (less than 25μ) b.Fine cut (less than 35μ) c. Coarse cut
  30. 30. 3.According to dispensing a.Powder mercury system b.Pellet mercury system c. Disposable capsules 3.According to composition a.Zinc containing alloys (Zn > 0.01%) b.Zinc free alloys (Zn < 0.01%) c. Pre-amalgamated alloy (Hg = 3%) 3.According to copper content a.Low copper (Cu 0 – 6%) b.High copper admixed (Cu 13%) c. High copper uni-composition (Cu 13-26%)
  31. 31. Manipulation Selection of materials Based on clinical requirement of restoration 1.Particle shape and size of the alloy 2.Presence or absence of Zinc 3.Composition as it is related to the elimination of Gamma II phase 4.Physical and mechanical properties 5.Manipulative characters 6.Dispensing system 7.Mercury and its purity
  32. 32. Structural component of dental resin based composite 1.Matrix- A plastic resin material that forms a continuous phase and binds the filler particles. 2. Filler- Reinforcing particles and/or fibers that are dispersed in the matrix 3. Coupling agent- Bonding agent that promotes the adhesion between filler and resin matrix 4. Activator-initiation system- required to convert resin paste from a soft moldable filling material to a hard durable restoration 5. Optical Modifiers- help to match colour of tooth structure
  33. 33. ACTIVATOR-INITIATOR SYSTEM Both monomethacrylate and dimethacrylate monomers polymerize by the addition polymerization mechanism initiated by free radicals. The free radicals can be generated by chemical activation or by external energy activation (heat, light or microwave). CHEMICALLY ACTIVATED RESINS supplied as two pastes Initiator – benzoyl peroxide Activator – N, N dimethyl –P-toluidine Both the activator and initiator mixed together to form free radicals and addition polymerization reaction is initiated.
  34. 34. LIGHT-ACTIVATED RESINS: Light-curable dental composites are supplied as a single paste contained in a light-proof syringe. It contains a photosensitizer and an amine initiator. As long as these two components are not exposed to light, they do not interact. However, exposure to light in the blue region (wavelength of ~468nm) produces an excited state of the photosensitizer, which then interacts with the amine to form free radicals that initiate addition polymerization. photosensitizer- Camphorquinone (CQ) Amine initiator-dimethylaminoethyl methacrylate (DMAEMA)
  35. 35. DUAL-CURE RESINS: One way to overcome limits on curing depth associated with light curing is to combine chemical curing and visible-light curing components in the same resin. So-called dual-cure resins are commercially available and consist of two light- curable pastes. light curing is promoted by the amine/CQ combination and chemical curing is promoted by the amine/BP interaction. Dual-cure materials are intended for any situation that does not allow sufficient light penetration to produce adequate monomer conversion, for example, cementation of bulky ceramic
  36. 36. CLASSIFICATION OF COMPOSITES: I. Classification given by Skinner: Traditional or conventional composites 8-12 µ.m Small particle filled composites 1-5 µ. m Microfilled composites 0-04 –0.9 µ. m. Hybrid composites 0.6-1 µ.
  37. 37. VI.GENERATIONS OF COMPOSITE RESTORATION (Marzouk) A. First Generation compositesA. First Generation composites Consist of macro-ceramic reinforcing phase. Has good mechanical properties. Highest surface roughness B. Second Generation compositesB. Second Generation composites Consists of colloidal and micro-ceramic silica. Low strength Unfavourable coefficient of thermal expansion Wear resistance better than first generation Best surface
  38. 38. C. Third Generation compositesC. Third Generation composites Hybrid composite [combination of macro and micro (colloidal) ceramics] Ratio of 75:25 Good surface smoothness and reasonable strength D. Fourth Generation compositesD. Fourth Generation composites Hybrid composite (heat-cured, irregularly shaped, highly reinforced composite macro- particles with micro (colloidal) ceramics]. Comparatively better surface characteristics and mechanical
  39. 39. E. Fifth Generation compositesE. Fifth Generation composites Hybrid composite (heat-cured, spherical, highly reinforced composite macro. particles with micro (colloidal) ceramics]. Improved workability Surface texture and wear is similar to second generation composites Physical and mechanical properties similar to fourth generation composites F. Sixth Generation compositesF. Sixth Generation composites Hybrid composite [agglomerates of sintered micro (colloidal) ceramics and micro-ceramics] Highest percentage of reinforcing particles Best mechanical properties Wear and surface texture similar to fourth generation Least polymerization shrinkage
  40. 40. VII. Classification according to Bayne and Heyman: CategoryCategory Particle sizeParticle size Megafill - 1-2 mm Macrofill - 10-100 µ.m Midifill - 1-10 µ.m Minifill - .01-.1µ. m. Microfill - 0.04-0.4 Nanofill - .005-.01 µ.m.
  41. 41.