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 - nonme...

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. Poly (Methyl Methacrylate) – polymer, is the TYPES OF RESINS principal component, and is present as small Acrylic Resins – derivatives of ethylene spheres called beads or pearls. and contain a vinyl group; two of dental 2. Benzoyl Peroxide – as initiator interest (acrylic acid and methacrylic 3. Ti Dioxide – controls translucency of the acid) polymer; increase the opacity until the material Methyl Methacrylate – liquid monomer has the approximate translucency of the oral type mixed with a polymer mucosa Poly (methyl methacrylate) – 4. Inorganic pigments – commonly mercuric transparent resin, stable, does not sulfide (red), cadmium sulfide (yellow) or ferric discolor in UV light oxide (brown); added to match the shade of DB Multifunctional methacrylates and to the soft tissues. acrylate resins – Bowen’s resin (or BIS- 5. Dyed Synthetic Fiber – for esthetics, to GMA) bisphenol glycidyl methacrylate, stimulate the minute blood vessels underlying TEGDMA, UDMA, PENTA-P the oral mucosa 6. Dibutyl Phthalate – plasticizer STAGES OF POLYMERIZATION (SEEN IN 7. Talc or gelatin – prevent cohesion of beads ACRYLIC RESIN USED FOR DB) or pearls during storage 8. Inorganic materials – zirconium, silicone, or I. Sandy Stage/Damp Stage alumina II. Sticky Stage - Controls the coefficient of thermal expansion; III. Dough Stage = Packing Stage of Resin increases stiffness of resin IV. Rubbery Stage V. Stiff Stage COMPONENTS OF LIQUID (MONOMER) 1. Methyl methacrylate – monomers, highly DENTURE BASE RESINS volatile 2. Hydroquinone – an organic inhibitor, less 3 types of Acrylic Resin than 0.1%, prolong storage; reaction can be 1. Heat-Cured Resin initiated by ultraviolet light 2. Chemically Cured Resin 3. Glycol Dimethacrylate – a cross-linking 3. Light-Cured Resin agent, resistance to surface cracks or crazing Manner of Dispensing: Powder 4. Organic Amine – organic accelerator to (polymer) and liquid (monomer) decompose peroxide at room temperature o Monomer (methyl methacrylate) – is a clear STEPS OF DENTURE BASE CONSTRUCTION transparent liquid at room USING THE DOUBLE-PRESSING TECHNIQUE temperature; highly volatile; light 1. Impression making sensitive; boiling pt. at 100.8°C 2. Construction of master/working cast 3. Construction of wax pattern for denture base 4. Investing 5. Place the upper half of the metal flask (MF), 5. Wax elimination then fill with POP up to the brim. Put on cover 6. Preparation of the mold space and place MF in a pressor to remove excess PP 7. Packing of resin into the mold space which will ooze out of the holes in the cover (compression and injection molding technique) 6. Allow the POP to set 8. Trial closure 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 over the resin and the mold space. The to produce a plastic mass which can be purpose: To prevent the adhesion of packed into the mold resin to the lower mold surface when the two halves of the flask are pressed 5 Stages: together. Stage 1. Damp Sand Stage – the polymer Pressure should be applied slowly so gradually settles into the monomer that the dough will be spread evenly Stage 2. Sticky Stage – the monomer attacks throughout the mold space. the polymer If too much material has been placed in - stringiness and adhesiveness if the mixture is the mold, it will be seen as excess touched or pulled apart material that overflowed onto the land Stage 3. Dough Stage – the mass becomes surrounding the mold space. The is more saturated with polymer in solution called the flash. If no flash occurs, it is - it becomes smooth and no longer tacky possible that there was insufficient - it is packed into the mold space dough in the mold Stage 4. Rubbery Stage Trial closure is done 2x, and after the - monomer evaporates and by further second time, the polyethylene sheet is penetration into the polymer removed, the flask closed properly with - the mass becomes more cohesive and a metal-to-metal contact and placed rubber-like in the presser. - cannot be molded and should not be packed The whole assembly is placed in the into the mold water bath for processing or curing of Stage 5. Stiff Stage – dough has completely the resin hardened; cannot be packed into the mold space Bench Curing - the flask is kept at a room temperature for 30- Dough Forming Time: Stage 3 60 minutes according to ADA SPEC. #12, must be -Equalization of pressure throughout the mold attained in at least 20 minutes from the space start of mixing at a temperature of 23°C Working Time: Is defined as the time CURING/PROCESSING PROCEDURE that elapses between stage 2 and the Heating process of the resin to arrive to beginning of Stage 4, the time the the polymerization of the resin materials remain in the dough form. Two methods in curing also known as According to ADA SPEC. #12, the dough the CURING CYCLE: should be moldable for at least 5 1. Rapid Curing minutes - Water: Slowly temperature increased until boiling TRIAL CLOSURE - Assembly on the bath for 1-1.5 During the dough stage, the resin is hours until it boils rolled into a ropelike form, bent into a - it will remain there for another horseshoes shape and placed in the 30 minutes, then the fire is upper half of the flask. A polyethylene turned off. sheet submerged in water is placed 2. Slow Curing - ideal curing cycle  - the assembly is placed in a E. Heating rate of resin was too high resulting to water bath at around 74C boiling of monomer - 6-8 hours (frequently overnight) External Porosities – found on the surface of PROCESSING the denture base; same causes as internal After processing it should be cooled porosities slowly to a water bath with room Result to difficulty in cleaning of temperature. If the flask is placed denture, porosities will trap food debris directly in tap water → WARPAGE which could give rise to foul odor Cause irritation to tongue or soft tissues - due to the differential thermal Will result to discoloration contraction of the resin and gypsum mold my result 2. Crazing – linear cracks, white or hazy appearance on the surface of the finished Ideally, removing the flask from the denture, usually small cracks. May be due water bath, bench cooling for 30 to too much pressure during curing; too minutes or more and then placing rapid heating under tap water is satisfactory 3. Fracture – breakage of the denture if it Deflasking was accidentally dropped while polishing; - open metal flask and remove too much pressure during separation from processed denture bases from the the working cast; excessive grinding and investment plaster polishing; inadequate curing time resulting to lower rigidity and strength Trimming and Polishing Trimming: To remove excess resin from 4. Warpage or Distortion – due to the sides of the processed denture base production of stress during processing; to avoid injury to the soft tissues production of heat during polishing Polishing: do not allow production of heat, could cause distortion, warpage of MISCELLANEOUS RESINS AND denture base TECHNIQUES 1. Repair Resins – usually with the use of the self-curing acrylic resin FAILURES OF DENTURE BASE RESINS 2. Rebasing/Relining of Dentures – it is Will result to a weakened denture base. often necessary to change the tissue 1. Porosities surface of the denture to conform to the Internal Porosities – found within the denture new tissue contours and occlusal base; usually in the thick portions relationships 3. Soft liners – soft cushion-like liner used CAUSES: - severe undercuts of the ridge A. Result of the vaporization of the monomer - sore residual ridges B. May also be due to too rapid curing - tissue treatment after oral surgery and in C. Packing resin before the dough stage obturators for congenital or acquired D. Insufficient pressure during packing defects of the palate  4. Resin Impression Trays – made of self- curing acrylic resins 5. Tissue Conditioners – provide a cushioning effect and massaging of the 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