DENTAL-RESINS-notes.pdf

DENTAL RESINS/SYNTHETIC RESIN 8. Restorative materials, adhesives, and root canal sealers (temporary and permanent) Synthetic Resin 9. Athletic mouth protectors, splints, and -...

DENTAL RESINS/SYNTHETIC RESIN 8. Restorative materials, adhesives, and root canal sealers (temporary and permanent) Synthetic Resin 9. Athletic mouth protectors, splints, and - nonmetallic materials, synthetically from obturators organic compounds 10. Orthodontic appliances - be molded into various forms 11. Maxillo-facial prosthetics - “Plastics” - (fibrous, rubber-like and resinous or DEFINITION OF TERMS hard-rigid) substances Polymerization – is the conversion of - composed of polymers, complex low molecular weight compounds molecules of high molecular weight called monomers to high molecular - frequently termed a polymers weight compounds called polymers. (acrylic and rubber-reinforced acrylic Monomer – means one unit polymers) Polymer – means many units A. ACCORDING TO THERMAL BEHAVIOR Free Radical – is a molecular fragment 1. Thermoplastic – molded without chemical with an unpaired electron change by softening it under heat Cross-linked polymer – is a high o Become liquid under great heat molecular network polymer o Soluble in organic solvents Copolymers – consist of two or more 2. Thermoset – chemical reaction takes place different monomers during the molding process Plasticize – means to soften o Chemically different from the original substance POLYMERIZATION o Are generally infusible and insoluble Macromolecule, or Polymer, is formed from large numbers of single molecules B. ACCORDING TO MANNER OF CURING OR known as monomer (meaning one POLYMERIZATION PROCESS mer/molecule) 1. Heat-cured Resin – by heating the process to form a single large molecule of high that takes hours molecular weight 2. Self-cured Resin – a.k.a auto-polymerizing is a repetitive intermolecular reaction resin, chemically activated resin that will cure that is functionally capable of at room temperature proceeding indefinitely. 3. Light-cured Resin – polymerization by halogen light 2 TYPES OF POLYMERIZATIONS 1. Condensation Polymerization USES OF DENTAL RESINS 2. Addition Polymerization 1. Elastomeric Impression Materials 2. Individual Trays 1. Condensation Polymerization 3. Denture Base - knowns as step-growth polymerization 4. Artificial Teeth/Pontics - atoms joins with other atoms to form new 5. Relining and Rebasing materials for denture - by-products such as water, halogen acids, bases and ammonia 6. Soft liners or tissue conditioners 7. Crowns or esthetic facings i.e. veneers 2. Addition Polymerization - by addition reaction - commonly used in dentistry o Polymer Poly (methyl - macromolecules are formed from smaller methacrylate) – transparent or units, or monomers without change in pink resin or remarkable clarity, composition stability, and does not discolor in - no formation of by-products ultraviolet light - requisite is the presence of a double bond and a free radical COMPONENTS OF POWDER (POLYMER) 1. TYPES OF RESINS 2. Acrylic Resins – derivatives of ethylene 3. and contain a vinyl group; two of dental 4. interest (acrylic acid and methacrylic 5. Dyed Synthetic Fiber – for esthetics, to acid) stimulate the minute blood vessels underlying Methyl Methacrylate – liquid monomer the oral mucosa type mixed with a polymer 6. Dibutyl Phthalate – plasticizer Poly (methyl methacrylate) – 7. Talc or gelatin – prevent cohesion of beads transparent resin, stable, does not or pearls during storage discolor in UV light 8. Inorganic materials – zirconium, silicone, or Multifunctional methacrylates and alumina acrylate resins – Bowen’s resin (or BIS- - Controls the coefficient of thermal expansion; GMA) bisphenol glycidyl methacrylate, increases stiffness of resin TEGDMA, UDMA, PENTA-P COMPONENTS OF LIQUID (MONOMER) STAGES OF POLYMERIZATION (SEEN IN 1. Methyl methacrylate – monomers, highly ACRYLIC RESIN USED FOR DB) volatile 2. Hydroquinone – an organic inhibitor, less I. Sandy Stage/Damp Stage than 0.1%, prolong storage; reaction can be II. Sticky Stage initiated by ultraviolet light III. Dough Stage = Packing Stage of Resin 3. Glycol Dimethacrylate – a cross-linking IV. Rubbery Stage agent, resistance to surface cracks or crazing V. Stiff Stage 4. Organic Amine – organic accelerator to decompose peroxide at room temperature DENTURE BASE RESINS STEPS OF DENTURE BASE CONSTRUCTION 3 types of Acrylic Resin USING THE DOUBLE-PRESSING TECHNIQUE 1. Heat-Cured Resin 1. Impression making 2. Chemically Cured Resin 2. Construction of master/working cast 3. Light-Cured Resin 3. Construction of wax pattern for denture base Manner of Dispensing: Powder 4. Investing (polymer) and liquid (monomer) 5. Wax elimination o Monomer (methyl 6. Preparation of the mold space methacrylate) – is a clear 7. Packing of resin into the mold space transparent liquid at room (compression and injection molding technique) temperature; highly volatile; light 8. Trial closure sensitive; boiling pt. at 100.8°C 9. Curing 10. Deflasking WAX ELIMINATION 11. Trimming/Polishing 1. Place the assembly (MF + presser) into a big STEPS IN DENTURE BASE CONSTRUCTION pan with boiling water for 5-10 minutes, to soften the wax. Do not melt the wax inside Impression Making the MF 1. Preliminary impression 2. Separate U & L half of the MF 2. Construct the study cast Remove softened wax, Pour hot water to create 3. Individual tray (for final impression) the mold space 4. Master/Working cast 3. Clean the mold space and prepare for packing resin Construction of DB wax pattern - while still warm, apply 2 layers of colorgard: 1. 1-2 layers of high fusing pink wax 1. To prevent penetration of monomer into the 2. Adapt it on the master cast investing medium; 3. Seal the edges with wax 2. To prevent water from entering the resin 3. To easily separated the processed DB from Investing – with the use of a metal flask the cast Metal flask has 4 parts: 1. Base PACKING OF RESIN 2. Lower half I. Dough-molding technique/Compression 3. Upper half molding 4. Cover Polymer: Monomer Ratio By volume = 3 – 3.5:1 HOW TO INVEST By weight = 2 – 2.5:1 1. Make deep scratches at the base of the master cast for retention II. Injection-Molding technique 2. Pour a mixture of Powder of Paris (POP) into the lower half of the metal flask Injection Molding Technique 3. Clean the created land area with wet finger A vent in the flask permits the to flatten the area and remove excess POP on attachment of an outside injector the cast The soft resin is contained in the 4. Allow the POP to set. While still warm, paint injector and forced into the mold space 2 layers of colorgard. Advantage: 1. No trial closure is necessary Colorgard – separating medium to prevent the 2. Mold is properly filled union between investing medium and U&L halves of the metal flask Monomer-Polymer Reaction: - the function of the monomer to the polymer is 5. Place the upper half of the metal flask (MF), to produce a plastic mass which can be then fill with POP up to the brim. Put on cover packed into the mold and place MF in a pressor to remove excess PP which will ooze out of the holes in the cover 5 Stages: 6. Allow the POP to set Stage 1. Damp Sand Stage – the polymer gradually settles into the monomer Stage 2. Sticky Stage – the monomer attacks If too much material has been placed in the polymer the mold, it will be seen as excess - stringiness and adhesiveness if the mixture is material that overflowed onto the land touched or pulled apart surrounding the mold space. The is Stage 3. Dough Stage – the mass becomes called the flash. If no flash occurs, it is more saturated with polymer in solution possible that there was insufficient - it becomes smooth and no longer tacky dough in the mold - it is packed into the mold space Trial closure is done 2x, and after the Stage 4. Rubbery Stage second time, the polyethylene sheet is - monomer evaporates and by further removed, the flask closed properly with penetration into the polymer a metal-to-metal contact and placed - the mass becomes more cohesive and in the presser. rubber-like The whole assembly is placed in the - cannot be molded and should not be packed water bath for processing or curing of into the mold the resin Stage 5. Stiff Stage – dough has completely hardened; cannot be packed into the mold Bench Curing space - the flask is kept at a room temperature for 30- 60 minutes Dough Forming Time: Stage 3 -Equalization of pressure throughout the mold according to ADA SPEC. #12, must be space attained in at least 20 minutes from the start of mixing at a temperature of 23°C CURING/PROCESSING PROCEDURE Working Time: Is defined as the time Heating process of the resin to arrive to that elapses between stage 2 and the the polymerization of the resin beginning of Stage 4, the time the Two methods in curing also known as materials remain in the dough form. the CURING CYCLE: According to ADA SPEC. #12, the dough 1. Rapid Curing should be moldable for at least 5 - Water: Slowly temperature minutes increased until boiling - Assembly on the bath for 1-1.5 TRIAL CLOSURE hours until it boils During the dough stage, the resin is - it will remain there for another rolled into a ropelike form, bent into a 30 minutes, then the fire is horseshoes shape and placed in the turned off. upper half of the flask. A polyethylene 2. Slow Curing sheet submerged in water is placed - ideal curing cycle over the resin and the mold space. The - the assembly is placed in a purpose: To prevent the adhesion of water bath at around 74C resin to the lower mold surface when - 6-8 hours (frequently overnight) the two halves of the flask are pressed together. PROCESSING Pressure should be applied slowly so After processing it should be cooled that the dough will be spread evenly slowly to a water bath with room throughout the mold space.  temperature. If the flask is placed Result to difficulty in cleaning of directly in tap water → WARPAGE denture, porosities will trap food debris which could give rise to foul odor - due to the differential thermal Cause irritation to tongue or soft tissues contraction of the resin and gypsum Will result to discoloration mold my result 2. Crazing – linear cracks, white or hazy Ideally, removing the flask from the appearance on the surface of the finished water bath, bench cooling for 30 denture, usually small cracks. May be due minutes or more and then placing to too much pressure during curing; too under tap water is satisfactory rapid heating Deflasking 3. Fracture – breakage of the denture if it - open metal flask and remove was accidentally dropped while polishing; processed denture bases from the too much pressure during separation from investment plaster the working cast; excessive grinding and polishing; inadequate curing time resulting Trimming and Polishing to lower rigidity and strength Trimming: To remove excess resin from the sides of the processed denture base 4. Warpage or Distortion – due to to avoid injury to the soft tissues production of stress during processing; Polishing: do not allow production of production of heat during polishing heat, could cause distortion, warpage of denture base MISCELLANEOUS RESINS AND TECHNIQUES 1. Repair Resins – usually with the use of FAILURES OF DENTURE BASE RESINS the self-curing acrylic resin Will result to a weakened denture base. 2. Rebasing/Relining of Dentures – it is 1. Porosities often necessary to change the tissue Internal Porosities – found within the denture surface of the denture to conform to the base; usually in the thick portions new tissue contours and occlusal relationships CAUSES: 3. Soft liners – soft cushion-like liner used A. Result of the vaporization of the monomer - severe undercuts of the ridge B. May also be due to too rapid curing - sore residual ridges C. Packing resin before the dough stage - tissue treatment after oral surgery and in D. Insufficient pressure during packing obturators for congenital or acquired E. Heating rate of resin was too high resulting to defects of the palate boiling of monomer 4. Resin Impression Trays – made of self- curing acrylic resins External Porosities – found on the surface of 5. Tissue Conditioners – provide a the denture base; same causes as internal cushioning effect and massaging of the porosities affected tissues - inflamed oral tissues are inflamed  6. Acrylic Resin Teeth/Pontics – acrylic and modified acrylic polymers are used in the manufacture of plastic teeth. The principal difference in the composition of plastic teeth and denture base materials is that different pigments are used to produce the various tooth shades. DENTURE CLEANSERS Dentures collect deposits in the same manner as do natural teeth. Deposits, stains, calculus can accumulate on dentures 2 methods are commonly used to remove stains and calculus 1. Professional repolishing of the denture 2. Soaking or brushing of the denture on a daily basis at home Requirements of an ideal denture cleaner: 1. Nontoxic and easy to remove (leaves no traces or irritant material 2. Able to attack or dissolve both the organic and inorganic portions of denture deposits 3. Harmless to all denture’s materials 4. Not harmful to eyes, skin, clothing if accidentally spilled or splashed 5. Stable during storage 6. Preferably bactericidal and fungicidal