Dental Materials PDF

Impression Materials According to Dr. McCracken: - used to form replicas or copies of teeth and Rigid/Inelastic – harden at time of removal other oral structures from mouth - the impr...

Impression Materials According to Dr. McCracken: - used to form replicas or copies of teeth and Rigid/Inelastic – harden at time of removal other oral structures from mouth - the impression is a negative reproduction - used on areas without undercuts, while the model or cast is the positive edentulous reproduction Example: Impression compound, - objective is to copy accurately the teeth and impression plaster, Zoe paste other structures in the oral cavity Elastic Setting Mechanism For dentate patients (with undercuts) Irreversible – reaction implies that Hydrocolloid chemical reaction has occurred, and o Reversible – agar that the material cannot revert to its o Irreversible – alginate present state. o Rubber impression material (elastomers) Example: Alginate, Zoe impression ▪ Polysulfides, polyether, paste, Impression plaster, and Elastomeric silicone: condensation impression materials. and addition Reversible – materials softened under heat and solidify when they are cooled, with no chemical change taking place Example: Reversible hydrocolloid, and Impression compound I. Primary Impression - alginate, impression compound, plaster II. Secondary/ Final/ Wash Impression - Corrective impression, the purpose of which is to construct a master cast or a working cast Types of Impression Tray for the fabrication of the prosthesis a. Stock tray b. Rim-locked tray c. Individual tray Classification of Impression Materials d. Perforated tray e. Water-cooled tray According to Manner of Hardening: Types of Impression Taking Thermoplastic – materials that set as a result Single Impression of change in temperature; soft when heated, Double Impression solidify when cooled; no chemical change o Preliminary Impression Example: Modelling compound or o Final Impression/Secondary impression compound “wash”  ▪ More accurate o Very brittle ▪ Corrects the defect of o Fractures easily preliminary impression o Reconstruct to form the completed impression Impression Plaster Other names: Type I Dental Gypsum; Soluble Impression Compound Plaster Other names: Modeling plastic, modeling Classification: Thermoset, Rigid, for Final or compound, dental impression compound Secondary Impression making Classification: Thermoplastic, rigid, Manner of Dispensing: Finely divided powder preliminary impression material added to water and sets as a result of hydration Manner of Dispensing: Cakes of different reaction; Color is light pink shapes and color; cones or stick forms Use: For final impression making of edentulous Colors: Pink, brown, maroon (cake forms) and arches green for the stick form Constituents/Composition Forms of Impression Compound 1. Calcium Sulfate Hemihydrate (Plaster) Cake form 2. Potato Starch = to render them soluble - Preliminary Impression 3. Potassium Sulfate (Accelerator); Sodium Stick Form Citrate (Retarder) - Border molding of individual tray 4. Alizarin Red (Coloring) - Copper tube impression technique 5. Peppermint (flavoring material) Cone Form Manipulation Impression Compound WP ratio:.50 -.75 Uses: Use plaster bowl and spatula a. For edentulous impression Type I/ Increase W/P ratio to reduce exothermic Impression Compound heat so as not to injure the soft tissue in b. In operative dentistry, to obtain impressions the mouth of single tooth Mix in a single rotary motion for 1 minute c. Tray compound used to form tray to be used Setting time is 3-5 minutes for other types of impression (IM) After mixing, pour on impression trays, tap a little to release air bubbles, then Types of Impression Compound seat the tray inside the patient’s mouth Type I Manner of withdrawal: Teasing True impression compound movement Low fusing compound, (55 - 65°C) Apply Cologuard- before pouring the Has high flow property gypsum Used to make a final impression of a tooth preparation Properties Type II Setting Expansion: 0.3% Tray compound Compressive Strength: 580+/-290 PSI High fusing compound (70°C) o Not popular in the market More rigid anymore For individual tray o Easy to break  Impression Compound: Components Disadvantage – if you fail to construct 1. Beeswax and Thermoplastic Resin the cast immediately after withdrawing Responsible for thermoplastic property the impression from the patient’s 2. Shellac, Gutta Percha, Stearic Acid mouth, the continuous flow property Act as plasticizer which can improve can be a source of error workability 3. French Chalk, Talc, Diatomaceous Earth Cast Construction and Separation Filler Wash in running water after withdrawal Hardening agents, Improve the strength No need for separating medium 4. Coloring pigments and Flavoring agent Mix Plaster of Paris to make a study cast Immerse in a hot water bath Manipulation: 2 Ways to Soften Impression o MC softens, if MC sticks to the Compound cast, soften a piece of MC and A. Dry Heat Method = heated over flame until allow it to come into contact with materials is softened; by direct flame (alcohol the melted MC lamp, Bunsen burner) or by oven B. Moist Heat Method = material is softened in Zoe Impression Paste hot water 50-70°C (Thermostatically controlled Is mixed to the consistency of a thin water bath) paste and is used in a custom-made compound or acrylic tray to record When a direct flame is used – do not allow impressions of completely or partially material to boil or ignite edentulous arches When large amount of compound is to be softened, moist heat method is best used Classification: Thermoset, Rigid (not used to record undercuts), Final/ Wash/ Disadvantages with the use of Moist Heat Corrective impression Method Manner of Dispensing: 2 – paste system in 1. Heated for an excessive period, it may collapsible tubes; base (white) & catalyst become brittle and grainy (brown, amber) 2. Chief Disadvantage – if water is incorporated plasticity is altered Types: Type I = Hard Set; 3-6 minutes IST / 10 min. FST Manner of Withdrawal: Teasing Method Type II = Soft Set; 3-6 minutes IST / 15 min. FST Properties of Impression Compound Zoe Impression Paste Poor thermal conductivity Uses: Dimensional change: Shrinks at 0.3- a. As final impression for an edentulous mouth 0.4% (soft set) With good flow property b. As a relining material for ill-fitting dentures Advantage – enables us to get a more c. For centric jaw registration detailed and accurate impression d. As a surgical dressing (periodontal surgery), The mixing of the two pastes is done on temporary filling material, cementing medium an oil-impervious paper or glass slab root canal filling material The proper proportion is 1:1 squeeze two ropes of paste of the same length Composition A flexible stainless-steel spatula is Base used for mixing a. Zinc Oxide = should be finely divided, The two ropes are combined with broad French processed and it should contain a very strokes in a sweeping motion, mixing is slight amount of water continued for 30-45 seconds to 1 b. Inert oil = mineral/vegetable oil; acts as a minute or until a uniform color is plasticizer, to make into a paste, and it also observed aids in masking the action of the eugenol as an irritant Setting time: 3-5 minutes c. Hydrogenated rosin = imparts Manner of Withdrawal: Teasing Method thermoplasticity to make zinc oxide more fluid Factors Controlling ST: Reactor/Catalyst = also called an accelerator 1. Presence of water, high humidity and a. Oil of cloves – contains 70-85% eugenol. Is increase in temperature (heat of the mouth) = easily identified by the characteristic odor of oil shortens or decreases the setting time cloves 2. Cool mixing slab or spatula = prolong setting b. Polymerized Rosin – facilitates speed of time reaction, and a smoother, more homogenous 3. Addition of chemical modifiers, zinc acetate product results; they prevent crystallization of or a small drop of water or alcohol to the base the paste or catalyst will decrease ST 4. Cool the spatula; addition of certain inert Composition (Catalyst) oils and waxes during mixing such as olive oil, c. Accelerators – of the setting time; calcium mineral oil to increase ST chloride, zinc acetate, primary alcohols, glacial 5. Altering the ratio of zinc oxide paste to the acetic acid. The accelerator can be eugenol paste; will result to poor consistency incorporated in one or both pastes and weak set material d. Olive oil, linseed oil, cotton seed oil – 6. Time of mixing – longer mixing time (within plasticizers, reduces burning sensation to limits) the shorter will be the ST tissues e. Canada Balsam, Peru Balsam = often used Construction of Casts to increase flow and mixing properties of the No separating medium needed paste After the stone has set, it can be f. Fillers = if the mixed paste is too thin or lacks separated from the impression by body before it sets; wax, or an inert powder immersion in hot water at 49C-60C for (kaolin, talc, diatomaceous earth, etc.) maybe 5-10 minutes added to one or both pastes The cast materials used with Zoe g. Coloring material impression materials are the gypsum h. Flavoring material type (Type II, III, IV)  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  ELASTIC IMPRESSION REVERSIBLE HYDROCOLLOID – AGAR MATERIALS CLASSIFICATION: Thermoplastic, Final/Wash Impression HYDROCOLLOID IMPRESSION MATERIALS MANNER DISPENSING: A. Reversible Hydrocolloid – AGAR GEL in a Collapsible Tube = Water B. Irreversible Hydrocolloid – ALGINATE Cooled Tray GEL in a Glass Jar = Syringe Type RUBBER IMPRESSION MATERIALS 1. Polysulfide Rim USES: 2. Silicone Rim a) To make impressions of dentulous & 3. Polyether Rim edentulous mouths b) As a duplicating material for casts duplication HYDROCOLLOID IMPRESSION MATERIAL HYDRO – water ADVANTAGES: COLLOID – mixture of 2 or more - Good surface detail substances in which one substance is - Reusable & easily sterilized suspended or dispersed within another surface DISADVANTAGES: A substance deforms when removed - Need special equipment (water bath) & from the mouth and springs back to its special technique original form – FLEXIBLE GEL. - Dimensional instability All colloids are termed as SOLS, (LIQUID LIKE) COMPOSITION: 1) AGAR – basic constituent SOL to GEL formation – Temperature - extracted from seaweed change - Tray material: 12-15% - Syring material: 6-8% HYDROPHILIC (Liquid Loving) sols is term for 2) WATER = principal ingredient by weight 80- hydrocolloid impression materials are solids 85% suspended in liquids. 3) BORAX = 0.2% - strength improver, increases viscosity The sol may be changed to a gel or jelly, of the sol, acts as retarder when the temperature is DECREASED. 4) POTASSIUM SULFATE = 1-2% ensures The temperature at which this change proper setting if the gypsum model and die occurs is known as the GELATION materials against the agar TEMPERATURE. 5) FILLERS = for the control of strength, viscosity and rigidity; diatomaceous earth, clay, TYPES: silica, wax, rubber and similar inert powders I. Reversible Hydrocolloids (SOL-GEL-SOL) 6) Coloring and flavoring materials II. Irreversible Hydrocolloids (SOL-GEL) 7) Plasticizer = Glycerin 8) ANTI-MICROBIAL AGENTS = Thymol (Bactericide) 9) Preservatives = 0.1% Benzoates E. DIMENSIONAL CHANGES - cast must be constructed within 15 minutes APPARATUS NEEDED Hydrocolloid conditioner Dehydrate = stiff and difficult to remove → Agar hydrocolloid fracture of cast Water cooled trays with tubing - Prolonged contact of agar with gypsum will MANIPULATION result in a rougher that normal surface on the Hydrocolloid conditioner (100°C for 10 model minutes) F. HYSTERESIS = - Gelation a solidification process, from so to MANNER OF WITHDRAWAL gel Impression is removed rapidly from the - The hydrocolloid gel does not return to the sol mouth with a SINGLE STROKE, at the same temperature it is solidified. SUDDEN JERK, SUDDEN PULL, NO - Liquefaction temperature: must be heated SIDE MOVEMENTS. at a high temperature Although the agar impression is flexible, - Hysteresis. The temperature lag between the it does not completely recover from gelation temperature and the liquefaction being deformed during removal from temperature of the gel undercut areas A slow removal is a common cause of Agar exhibits hysteresis, melting at 85°C inaccuracy (358K, 185°F) and solidifying from 32-40°C. (305-313K, 90-104°F) PROPERTIES: A. STRENGTH (TRAY) - Tear strength: 4 LB/IN2 (715 GM/CM2) IRREVERSIBLE HYDROCOLLOID - ALGINATE - Compressive strength: 116 LBS/IN2 (8000 GM/CM2) DESCRIPTION: ** The syringe material has POORER - From the “ALGIN” dental compound; derived mechanical properties from a brown seaweed (algae) that yields a B. CONSISTENCY AND RIGIDITY peculiar mucous extraction - Homogenous and free of lumps when used for - One of the most widely used dental impression impression material - Fluid enough to be easily transferred - Upon setting it becomes a little stiff ADVANTAGES: C. POOR MECHANICAL PROPERTIES 1. Easy of missing and manipulating - Increases stiffness, material becomes brittle 2. Minimum equipment necessary and fractures 3. Flexibility of the set impression D. SHELF LIFE = poor shelf life; storage of agar 4. Accuracy of handled properly impressions is to be avoided. After impression 5. Low cost making, if storage is unavoidable, it should be 6. Comfortable to the patient limited to 1 hour in 100% relative humidity. SYNERESIS: Dehydration CLASSIFICATION: Thermoset; Elastic, IMBITION: Storage in water causes swelling of Preliminary/Final Impression Material the impression MANNER OF DISPENSING: STAGES DURING GELATION: CHEMICAL Powder + Water = SOL → GEL EQUATION: Powder is placed in a pre-weighed 1. When alginate is mixed with water individual containers (pouch) 2NA3PO4 + 3CASO4= CA3(PO4)2 + 3NA2SO4 TYPES BASED ON SETTING TIME: Main ingredient must first react with 1. TYPE I – Fast set (Must gel in not less than 60 NA3PO4, a retarder, until the latter is seconds nor more than 120 seconds used up. 2. TYPE II – Normal set (Must gel between 2-4.5 2. When alginate is already in the patient’s minutes) mouth KNALG + NCASO4 = NK2SO4 + CANALG USES: SOLUBLE SOL INSOLUBLE SOL 1. For full mouth impressions – dentulous & Before it reacts with soluble sol to edentulous produce insoluble gel 2. For quadrant impressions 3. As a duplicating material MANIPULATION: W/P ratio = 15-18 gram: 40-50 CC water COMPOSITION: Water first before powder 1) NA or K Alginate – main ingredient, soluble Use horizontal figure 8 while swiping or salts of alginic acid; FUNCTION: to dissolve in stropping the mixture against the sides water to form sol of the bowl 2) CA SO4 – Reactor, Mixing time: 45 sec to 1 minute Dihydrate: Commonly used Result: Smooth, Creamy mixture Hemihydrate: Increases shelf life of the Tray material: The proper size of tray powder and increases dimensional should be selected before mixing, stability of the gel loading of the tray should be done 3) NA PO4 – Trisodium Phosphate quickly Retarder Material is added to the posterior 4) Diatomaceous Earth or Silicate Powder portion of the tray then pushed toward (Fillers) the anterior part Increases strength and stiffness Wait for 2-3 minutes after gelation Produces a smooth texture before withdrawing the Ensures a firm gel surface that is not IMPRESSION: Single firm motion, tacky sudden pull or sudden jerk Disperses the alginate powder particles in water FACTOR TO CONTROL GELATION TIME: 5) K TI Fluoride – accelerates setting of the W/P ratio stone; Plaster hardener effect the surface o More water: increased gelation finish time 6) Organic Glycol – makes alginate “dust-free” o More powder: decreased 7) Quaternary Ammonium Compounds – gelation time provide self-disinfection Mixing time 8) Flavoring and coloring materials o Shorter: increased gelation time o Longer: decreased gelation time  Temperature o Low: increased gelation time o High: decreased gelation time SHELF LIFE 2 Major Factors to consider: o Storage temperature o Moisture contamination from the air Store in cool, dry environment in containers with tight lids PROPERTIES: A. Dimensional Stability = is loss of accuracy with increased time of storage 1. SYNERESIS – water evaporates = SHRINKS 2. IMBIBITION – placed in water = SWELL/EXPANDS B. STRENGTH = alginate may be greater than that of agar materials. Tear strength: 2-4 LBS/IN (358-716 GM/CM) Compressive strength of 5000-7000 GM/CM2 C. FLOW = good flow property → Accuracy and detail D> ADHESIVE PROPERTY = or the property for alginate to be TACKY before setting  DENTAL WAXES AND INLAY Bite Registration Waxes Soft and very similar to casting waxes Softened under warm water Boxing Wax Patient is instructed to bite down, and Soft pliable wax with a smooth and the wax will form an imprint of the teeth. shiny appearance Supplied in long narrow strips Inlay Casting Wax measuring 1 to 1 ½ inches wide and 12 Hard brittle wax is made from paraffin to 18 inches long. wax, carnauba wax, resin, and beeswax. Used to form a wall or box around a Used to create a pattern of the indirect preliminary impression when pouring it restoration on a model. up. Poor thermal conductor and dark in color Sticky Wax Classified according to how they flow: Supplied in sticks or blocks 1. TYPE I: Medium Wax – Direct Main ingredients are beeswax and rosin technique Very brittle wax, but when heated, it 2. TYPE II: Soft Wax – Indirect becomes very tacky technique Useful when creating a wax pattern or joining acrylic resin together COMPOSITION OF INLAY WAX: Paraffin Wax – main ingredient, usually Utility Wax in concentration of 40 to 60 WT% Tacky at room temperature Gum Dammar – or dammar resin, Once applied, it will adhere without heat improves smoothness and toughness Ideal for build-up of impression trays render it more resistant to cracking and flaking Casting Wax Carnauba Wax – quite hard and has a Makeup of paraffin, ceresin, beeswax, relatively high melting point, it and resins. decreases the flow and contribute to the Supplied in sheets of various glossiness. thicknesses Candelilla Wax – replace the carnauba Used for single tooth indirect wax, same qualities but melting point is restorations, fixed bridges, and casting lower metal portions of a partial denture Coloring Pigments Baseplate Wax METHODS IN MANIPULATING THE INLAY Made from paraffin or ceresin with WAX beeswax and carnauba wax Dry Heat – for small amount Hard and brittle at room temperature o Heat (torch) Supplied in sheets Moist Heat – for big amount Three types: o Water bath 1. TYPE I – which is a softer wax ▪ Soften the wax, knead it used for denture construction until homogenous inside 2. TYPE II – a medium-hardness and out wax used in moderate ▪ Form the wax into a cone climates and press it into the 3. TYPE III – a harder wax for use prepared cavity in tropical climates ▪ Hold the wax until it solidifies  ▪ Carve the wax pattern to Sprue simulate normal anatomy o Made up of metal, resin and wax and contact areas o Do definite size Asbestos Sheet HOW TO PREVENT WAX DISTORTION o Act as shock absorber to prevent Avoid thermal change the sudden entrance or loss of Soften in homogenously heat during wax elimination Do not allow impurities Inlay Ring No droplets of water incorporated in o Metallic tube open on both ends wax pattern Investment Material o Spattering of wax upon flaming- ex frying with water INVESTING o Smearing of the surface of the To create a mold, use an investment wax compound because it can tolerate high temperature INLAY Is an indirect restoration (filling) WAX ELIMINATION consisting of a solid substance fitted to Remove crucible former and sprue a tooth and cemented into place. former Temperature: 700C-1,600C CASTING INVESTMENTS AND Continuous heating for 1 hour before PROCEDURES 700F should be reached Wax pattern construction Red hot color of inlay ring will assure Investing that wax elimination is complete Wax elimination Sprue space or the ingate Casting o Previously occupied by the Quenching sprue former Pickling o Passageway of the melted Polishing metal to the prepared mold space (Should have a parallel/diverging wall and wider base) (No undercuts for easy removal) QUENCHING Bring the inlay ring into the running WAX PATTERN CONSTRUCTION water to give an annealing (make metal Indirect Technique – done outside the softer) effect to the metal mouth with a die stone o Take impression of mouth and PICKLING construct with die stone Heating the metal in acid to remove the o Apple separating medium (water) surface discoloration of the metal o Soften the inlay wax until Uses pickling solution: HCL Acid homogenously soft then insert to Wash in sodium bicarbonate and water tooth cavity until it hardens to remove HCL acid then fit inside the prepared cavity ACCESSORIES FOR INVESTING AND CASTING POLISHING Crucible Former o Act as support for the sprue former as it cannot stand without a crucible o Made up of metal, resin, rubber, wax