Dental Materials PDF

DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE SHOULD BE: INTRODUCTION: DENTAL MATERIALS 1. Be biocompatible...

DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE SHOULD BE: INTRODUCTION: DENTAL MATERIALS 1. Be biocompatible 2. Bond permanently to tooth structure or TOPIC OVERVIEW bone 1. DENTAL MATERIALS 3. Match the natural appearance of tooth a. What are dental materials? structure and other visible tissues b. Ideal restorative materials 4. Exhibit properties similar to those of should be tooth enamel, dentin, and other tissues 2. CLASSIFICATION OF DENTAL 5. Be capable of initiating tissue repair or MATERIALS the regeneration of missing or damaged a. Preventive materials tissues b. Restorative materials c. Auxiliary materials B CLASSIFICATION OF DENTAL 3. HISTORY MATERIALS a. The 1700s b. The 1800s c. The 20th Century 1. Preventive materials 4. AGENCIES RESPONSIBLE FOR 2. Restorative materials STANDARDS 3. Auxiliary materials 5. FOOD AND DRUG ACT OF 1975 a. Categories of medical devices PREVENTIVE DENTAL MATERIALS 6. INTERNATIONAL STANDARDS Pit and fissure sealants A DENTAL MATERIALS CEMENTS a. As lusting agents - holds the crown into the tooth and fills in Is a science which deals with the study of the microscopic gaps between the physical and chemical properties, the tooth and the crown application, uses and manipulations of b. As bases and liners - protects the various materials in the practice of pulp from irritating materials dentistry. RESTORATIVE MATERIALS WHAT ARE DENTAL MATERIALS? 1. Restorations - use to replace lost tooth Dental materials may fall into any of structure the following classes: ANTERIOR TEETH 1. Metals Composite materials - shaded to match 2. Ceramic the appearance 3. Polymers Weaker than metals 4. Composites strength is secondary since anterior Ceramic, polymers, and composites are teeth are not subject to high biting used for preventive and restorative forces applications POSTERIOR TEETH Preferably metallic restoration because of IDEAL RESTORATIVE MATERIAL strength considerations PAGE 1 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE Dental silver amalgam and gold inlays c. Indirect Restorative Polymers - are used pink “gingival portion of the 2. Crowns - used to restore teeth when a denture” substantial amount of tooth structure is missing CLASSIFICATION BY 3. Fixed Partial denture (Fixed Bridge) - LONGEVITY OF USE replaces a lost tooth or teeth. Each end is supported by abutment - Gold or nickel-chromium alloys 1. Permanent restorations - restorations for dental bridgework because of that are not planned to be replaced in a their strength, tarnish, resistance, particular time period and ease of casting 2. Temporary restorations - planned to be - Cements are used to hold the replaced in a short time bridge in place 3. Interim restorations - requires 4. Complete and Partial Dentures “long-term” temporary restorations Prosthesis - artificial device that replaces a lost organ or tissues AUXILIARY DENTAL MATERIALS Denture - replaces the missing teeth, bone and gingiva after the teeth have been lost or extracted Impressions, casts, and models Complete denture - a prosthesis that Impressions - negative copy replaced all the teeth that are missing Casts and models - are the replica of the Removable partial denture - replaces patient’s oral tissue few teeth that is placed and removed by Polishing materials - remove plaque and the patient debris from tooth and surfaces 5. Veneers - used to cover unsightly areas Implants - are typically screws or posts of anterior teeth that are severely that are anchored into the alveolar bone discolored, malformed and eroded and the root portion of the lost teeth 6. Resin-bonded fixed partial denture or Specialty materials: sutures, elastics Maryland - if the abutment are healthy and free of major restorations TEMPORARY MATERIALS a. Temporary crowns b. Temporary restorations 1. Follow the MANUFACTURERS DIRECTION Read and understand the procedures CLASSIFICATION BY LOCATION OF Save and file copies in case of loss FABRICATION When new material is purchased, practice at least once before using 1. Direct Restorative Materials - 2. Use dock that has a second hand or constructed directly in the oral cavity displays seconds a. Amalgam The mouth is a warm b. Composites environment. Materials sat faster c. Glass ionomers in the mouth 2. Indirect restorative Materials The setting of some materials is a. Gold also accelerated by the humidity b. Ceramic metals of the mouth 3. DISPENSING MATERIALS PAGE 2 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE Dispense properly as directed GOLD BANDS AND WIRES were used by Dispense equal lengths, not equal the Phoenicians (after 2500 BC) and the volumes, of pastes Etruscan (after 700 BC) for the Dispense consistent drops construction of partial dentures Fluff powders if recommended. Alginate should be tumbled Etruscans documented the first tooth periodically to fluff the powder implant materials as early as 700 BC but not necessarily for every impression Hammered gold inlays and stone or 4. MIXING mineral inlays were placed for esthetic Mixed dental materials purposes or traditional ornamentation by aggressively the Mayans and later the Aztecs The setting rate of some materials is affected by the mixing GOLD FOIL for dental restorative technique purposes. When mixing cements, force the powder into the liquid Its initial use is attributed to Johannes 5. LIGHT ACTIVATED MATERIALS Arcelanus of the University of Bologna You can undercure, but you (Italy) in 1498 cannot overcure, light activated materials As dentistry developed throughout the Maintain the tip of the curing ages, more and more materials were light and the oral tissues used. Light activated materials will begin to set in ambient room Pierre Fauchard (1678-1761) light. Cover materials if not - father of modern dentistry immediately used - used tin foil or lead cylinders to fill 6. CONTAMINATION tooth cavities Bad for all materials - - published a book describing many types of dental restorations, including a method for the construction of artificial dentures C HISTORY made from ivory. Porcelain — was fired eb tooth shapes. THE 1700s - in 1792, de Chemant patented a process for the construction of porcelain teeth Ancient times to the 1700s - much has been learned Wax and gypsum - in 1756, Plaff throughout history by trial and error described a method for making impressions of the mouth in wax, from Gold was used not only for its corrosion which he constructed a model with resistance but also for its "workability" or Plaster of Paris. ease of processing. They have attempted to improve their appearance with adornments, such as jewelries and make-up. Also the replacement of the lost teeth, not for function but esthetics PAGE 3 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE h. 1983 - Horn introduces the resin-bonded THE 1800s ceramic veneer i. 1985 - development of dentine bonding The pace of development of new dental agents materials quickened j. 1988 - introduction of resin-modified 1826 - Taveau of Paris suggests the use of glass ionomer cements silver and mercury to make paste for k. 1994 - first compomer appears on the filling teeth. market 1839 - the first dental journal, called the American Journal of Dental Science, is D AGENCIES RESPONSIBLE FOR published STANDARDS 1840 - "Amalgam War" - disagreement over the value and safety of amalgam 1839 - Charles Goodyear invented of a National Institute of Standards and low-cost vulcanized rubber allowed Technology (NIST) - First to establish dentures to be molded accurately to fit evaluation and selection of dental the mouth. material 1907 -Taggert developed a more refined American Dental Association (ADA) method for producing cast inlays -assumed the continued dental research 1879 - zinc-oxide eugenol and zinc of NIST (1928) phosphate, which evolved as fillings and Council on Scientific Affairs (CSA) 1966- cements to "glue" the restoration to the assumed responsibility for standards tooth development and initiated the 1880 - silicate cements are develop se certification of products that meet the 1895 - G.V. Black (Greene Vardiman requirements of these specifications Black) develop an acceptable amalgam ADA Standards Committee for Dental formula Products (SCDP) -develops Porcelain was also used for inlays and specifications for all dental mate- rials, crowns instruments, and equipment with the Fluoridation by Dr. Frederick McKay for exception of drugs and x-ray films. preventive dentistry in 1944 After formulation of the specifications by the ADA, it is submitted to the ANSI. On THE 20th CENTURY approval it becomes a national standard. a. New materials and techniques are constantly being developed. ADA'S Seal of Acceptance b. 1907 - WH. Taggart of Chicago invents a practical method of casting gold inlays c. 1950 - introduction of acrylic resin for Symbol of safety and effectiveness fillings and dentures Toothpaste, toothbrushes, mouth rinses, d. 1955 - Buonacore discovers the acid - floss and other interdental cleaners, etch technique for bonding to enamel sugar-free chewing gums, denture e. 1970 - Composites begin to replace adherents and cleansers. silicates cements. ADAs Seal of Acceptance for successful f. 1976 - Glass ionomer cements are evaluation is given for a period of 5 years invented by Wilson and after which the applicant must g. 1978 - Light activated composites resubmit the product appear on the market PAGE 4 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE Seen in: Many dental product carry the CE 1. Toothpaste marking symbol of the European Union, 2. 2. Toothbrushes CE stands for Conformite Europeene 3. Mouth rinses CE indicates compliance with ISO and 4. Floss European Union requirements for dental 5. Interdental cleaners products 6. Sugar free chewing gums 7. Denture adherents WHEN DOES A RESTORATIVE 8. Denture cleansers MATERIAL BECOME OBSOLETE? The Acceptance Program of the ADA IS voluntary (1) their drawbacks overall far outweighed their known advantages (2) material degradation led unacceptable E FOOD and DRUG ACT OF 1975 margin adaptation, (3) material degradation led to unacceptable Oldest consumer protection agencies esthetics, protects the public by ensuring that (4) metallic appearance was generally products meet certain standards of unacceptable to patients, safety and efficacy (5) alternative restoratives exhibited superior performance, (6) alternative materials were less technique- sensitive, CATEGORIES OF MEDICAL DEVICES (7) and alternative materials led to less cos: ly patient treatment. 1. Class I - least regulated. Only grod manufacturing devices are required Ex. Prophy paste brushes 2. Class II - Must meet certain performance standards such those of ADA'S Seal Program Ex. composite, amalgam 3. Class Ill - most regulated; Require premarket approval clinical data must be submitted to the US FDA for evaluation before being sold. If the device is supported by data, the US FDA then gives approval to market the product Ex. Dental implants F INTERNATIONAL STANDARDS Fédération Dentaire Internationale (FDI) and the International Organization for Standardization (ISO) are working toward the establishment of specifications for dental materials on an international level. PAGE 5 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE ○ from the cooling of wax patterns or gold restorations during PROPERTIES OF DENTAL MATERIALS fabrication TOPIC OVERVIEW A THERMAL DIMENSION CHANGE 1. IMPORTANCE Temperature changes in the mouth 2. DIMENSIONAL CHANGE result in the dimensional changes in the a. THERMAL DIMENSION materials as well as in the neighboring CHANGE tooth structures that may cause leakage 3. THERMAL CONDUCTIVITY of oral fluids between the restoration and 4. ELECTRICAL PROPERTIES the tooth 5. ABSORPTION AND ADSORPTION Restoration will shrink with cold and 6. WETTABILITY expand with heat a. EXAMPLES OF WETTABILITY Gap - may cause recurrent caries OF SOLIDS BY LIQUID To make a comparison between 7. MECHANICAL PROPERTIES materials easier, the linear thermal a. STRESS expansion is expressed as a b. STRAIN COEFFICIENT OF THERMAL EXPANSION c. STRESS-STRAIN CURVES Percolation - Penetration and forcing d. ELASTIC MODULUS out of oral fluids between the dental e. PROPORTIONAL LIMIT AND restoration and the tooth because of YIELD STRENGTH differences in thermal coefficient of f. ULTIMATE STRENGTH expansion of the materials g. RESILIENCE AND TOUGHNESS h. HARDNESS 3 THERMAL CONDUCTIVITY 1 IMPORTANCE Used as a measure of heat transferred and to the rate of heat flow through a 1. Materials used to replace missing material portions of teeth are exposed to oral Enamel and dentin are poor thermal fluids and subjected to biting forces. conductors compared with gold alloys 2. basis for the selection of materials. and dental amalgam 3. the establishment of critical physical Glass ionomer cement bases is used as properties of various dental material has insulating agent because they closely led to the development of minimum replace lost tooth structure standards and specifications Cavity varnishes and liners have low thermal conductivities, but they are used in layers so thin that become ineffective 2 DIMENSIONAL CHANGE as thermal insulators Is the percent shrinkage or expansion of a material Occur during setting as a result of a chemical reaction, such as with ○ rubber impression materials ○ resin composite restorative materials PAGE 1 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE 4 ELECTRICAL PROPERTIES 6 WETTABILITY 1. GALVANISM Is a measure of the affinity of a liquid for is the generation of electrical a solid as indicated by spreading of a currents that the patient can feel. drop Results from the presence of two dissimilar metals in the mouth Ex. Aluminum and gold 2. CORROSION Can result from this same condition when adjacent restorations are of dissimilar metals As a result of the galvanic action, material goes into solution, and roughness and pitting occur. A EXAMPLE OF WETTABILITY OF Corrosion also may result from SOLIDS BY LIQUID chemical attack of metals by components in food or saliva. The wetting of denture base acrylic by TARNISH - is a surface reaction of saliva metals in the mouth from The wetting of tooth enamel by pits and components in saliva or foods fissure sealants 5 ABSORPTION and ADSORPTION The wetting of elastomeric impressions by water mixes of gypsum materials The wetting of wax patterns by dental ABSORPTION - refers to the uptake of investments fluid by bulk (internal) ○ Ex. absorption of water by acrylic polymers 7 MECHANICAL PROPERTIES ADSORPTION - indicates concentration of molecules at the surface of a liquid or solid STRESS ○ Ex. Detergent adsorbed on the STRAIN surface of the wax pattern ELASTIC MODULUS PROPORTIONAL LIMIT AND YIELD STRENGTH Why is solubility and sorption of the ULTIMATE STRENGTH restoration material important to consider? ELONGATION AND COMPRESSION Solubility and sorption are important RESILIENCE AND TOUGHNESS to consider because the materials in HARDNESS the mouth are covered with plaque and therefore are exposed to various acids and organic materials. A STRESS The force per unit area ○ Ex. Unsharpened pencil is placed against palm of the hand, a force is applied by placing a book on PAGE 2 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE the end of the eraser and any pain A load that tends to resist the is noted sliding/ twisting/torsional action ○ Sharpened pencil; the procedure on a material is repeated; and the increased Eg: Debonding of orthodontic pain is noted as a result of the bracket increase in stress TYPES OF STRESS 1. Compressive - material is squeezed together or compressed 2. Tensile - material is pulled apart 3. Shear- when one portion of the material is forced to slide by another portion 4. twisting movement 5. bending moment (flexure) B STRAIN TENSILE STRESS When two sets of forces are Is the change in length, or deformation directed away from each other per unit length, when a material is A load that tends to stretch or subjected to forced elongate a body. Ex. If a rubber band 2.54 cm. long is E.g.: crown removal by means of stretched 1.27 cm., the strain is as follows tensile force. elastomeric impression materials, exhibit considerable strain when a stress is applied; gold alloys or human enamel, show low strain under stress. COMPRESSIVE STRESS When two sets of forces are directed towards each other C STRESS-STRAIN CURVES A load that tends to compress or shorten a body. The convenient means of Eg. Masticatory force acting on comparing the mechanical restorations or prostheses. properties of materials is to apply various forces to a material and to determine the corresponding values of stress and strain SHEAR STRESS When two sets of forces are directed parallel to each other but not along the same line PAGE 3 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE D ELASTIC MODULUS G RESILIENCE AND TOUGHNESS Is equal to the ratio of the stress to the Resilience is energy required to deform a strain in a linear or elastic portion of the material permanently stress strain curve Toughness is the energy necessary to represents the relative stiffness or rigidity fracture a material of the material within the elastic range. e.g. if a wire is difficult to bend, considerable stress must be placed before a notable strain or deformation results. The metal frame of a metal-ceramic bridge should have a high stiffness. If the metal flexes, the porcelain veneer on it might crack or separate. E PROPORTIONAL LIMIT AND YIELD STRENGTH Proportional limit and yield strength indicate the stress at which the material no longer functions as an elastic solid. proportional limit is the stress on the stress-strain curve when it ceases to be linear or when the ratio of the stress to Resilience and Toughness - Resilience the strain is no longer proportional. and toughness indicate the energy The yield strength is the stress at some absorbed up to the proportional limit arbitrarily selected value of permanent and the ultimate strength, respectively, strain, such as 0.001, and thus is always and relate to the resistance to slightly higher than the proportional deformation and fracture under impact. limit. Two materials may have the same resilience, with one having high yield strength and low corresponding strain F ULTIMATE STRENGTH and the other having lower yield strength and higher corresponding strain The stress at which fracture occurs H HARDNESS If fracture occurs from tensile stress, it is called tensile strength If fracture occurs from compression, it is the resistance of the material to called compressive strength indentation If fracture occurs from shear, it is called Measured by Knoop Hardness shear strength ○ the larger the indentation, the smaller the value PAGE 4 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE MODEL AND DIE CAST 1 TWO COMMON MATERIALS USED TO POUR IMPRESSIONS TOPIC OVERVIEW 1. Gypsum materials 2. Epoxy materials A. DESIRABLE PROPERTIES a. Two common materials used to pour impressions COMPATIBILITY OF DIE MATERIALS WITH B. GYPSUM PRODUCTS IMPRESSION MATERIALS a. Chemical and physical form b. Chemical reaction and excess GYPSUM Agar water PRODUCTS Alginate* c. Accelerators Condensation silicones d. Retarders Addition silicones (PVS) e. Water/Powder ratio Polysulfides f. Temperature Polyethers* g. Humidity h. Hardening solutions EPOXY RESIN Condensation silicones (some C. PROPERTIES OF GYPSUM PRODUCTS require separator)* MATERIALS Addition silicones (PVS) (some a. Spatulation/mixing require separator)* b. Measurement of setting time Polyethers* D. STRENGTH Polysulfides (with separator) a. Factors affecting the strength b. Two types of strength c. Surface hardness B GYPSUM PRODUCTS d. Dimensional stability E. TECHNIQUE OF USE F. MIXING/SPATULATION ADA/ANSI Specification No.25/ISO 6873:1998 G. POURING THE MODEL H. DISINFECTION Type 1 - Impression plaster Type 2 - Model plaster MODEL AND DIE MATERIALS Type 3 - Dental stone are used to make replica for diagnosis Type 4- High-strength/low-expansion and treatment of oral diseases diseases dental stone (die stone) Type 5 - High strength/high expansion dental stone A DESIRABLE PROPERTIES 1 CHEMICAL AND PHYSICAL FORM Accuracy Dimensional stability Ability to produce fine detail The physical forms are DIFFERENT BUT Strength and resistance abrasion the chemical forms are the same: Compatibility with impression material ○ calcium sulfate hemihydrate Color (CaSO4 '½ H0) Biological safety Ease of use Cost PAGE 1 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE All are manufactured from the mineral Plaster of Paris should not be confused gypsum which is with orthodontic plaster which is a ○ calcium sulfate dihydrate mixture of plaster and dental stone (CaSO4 2H20) DIFFERENCE -> Physical forms of the DENTAL STONE hemihydrate form when the water is METHOD OF CALCINATION: Produced driven out by heating the gypsum under steam pressure in a closed container at 125°C IMPRESSION PLASTER POWDER PARTICLES: larger, denser, Type I more regular crystals and more original impression material rigid, expensive than plaster fractures and breaks easily used for COLOR: yellow edentulous models OTHER NAME: Often referred to as Sets shorter of 3 to 5 minutes from model ○ a hemihydrate plaster ○ Type Ill stone Dimensional change on setting reduced STRENGTH: stronger and more resistant to 0.06% to abrasion USES: MODEL PLASTER/ PLASTER OF PARIS 1. for forming mouth protectors Name obtained from burning the 2. For working castHydrocal gypsum from deposits near Paris, France METHOD OF CALCINATION: Produced HIGH-STRENGTH/LOW EXPANSION DENTAL when the gypsum mineral is heated in STONE an open kettle at a temperature of about METHOD OF CALCINATION: Made from 115°C gypsum by boiling the gypsum in 30% OTHER NAME: Sometimes referred to as calcium chloride solution B hemihydrate or Type II STRENGTH: Strongest, highest abrasion POWDER PARTICLES: porous, Small resistant irregular crystals, least expensive POWDER PARTICLES: least porous, most regular and largest of all hemihydrates; most expensive OTHER NAME: ○ Type IV stone ○ die stone ○ Densite ○ modified alpha hemihydrate COLOR: Blue, green, yellow USES: 1. for making cast or dies for crown, bridge and inlay fabrication HIGH STRENGTH/ HIGH EXPANSION DENTAL STRENGTH : weakest STONE COLOR: white Type IV USES: It is the most recent gypsum product 1. For making study casts and having a higher compressive strength models. than Type 4 stone. 2. To make molds for curing Improved strength is attained by making dentures. it possible to lower the w/p ratio even 3. For mounting casts on articulator. further. PAGE 2 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE Setting expansion has been increased Colloidal particles such as blood, saliva, from a maximum of 0.10 to 0.30% to agar, or unset alginate, retard the setting compensate for the shrinkage of base reaction. metal alloys, during solidification ○ Impressions should be rinsed Examples: Hard Rock, Jade Rock and thoroughly in cold water to Resinrock XL5 (by Whipmix) and remove traces of blood and saliva Denflo-HX before the impression is poured. USE: To prepare dies with increased expansion. 5 WATER/POWDER RATIO 2 CHEMICAL REACTION AND EXCESS Defined as the amount of water in WATER milliliters added to 100 mg of powder ○ expressed in fraction Excess water is needed to produce a Higher W/P ratio-soupy workable mass ○ Lengthens setting time and the larger and denser the crystal size of reduces the strength the hemihydrate, the LESS excess water ○ creates thinner mix - weaker cast is required ○ Greater porosity of the cast Excess water evaporates, leaves voids = reduce density /most porous PROPER WATER/POWDER RATIO High-strength stone, with its large, dense crystals, requires the least excess water. PLASTER 45-50 ml/100g (0.45-0.50) Dental stone requires somewhat more water STONE 28-30 ml/100g (0.23-0.30) Plaster requires the most excess water IMPROVE 19-24 ml/100g (0.19-0.24) 3 ACCELERATORS STONE - for average mix Accelerators are chemicals that increase the rate of setting; decreases setting 6 TEMPERATURE time ○ A 2% water solution of potassium sulfate (K,SO,)reduces the setting If the room temperature (20°C to 25°C) is time of model plaster from 10 raised up to body temperature (37°C), the minutes to 4 minutes. setting time decreases (SHORTER) ○ 2% sodium chloride If water temperature is raised above ○ terra alba 37.5°C, the setting time will increase because the dihydrate becomes more soluble in the water. (LONGER) 4 RETARDERS Hemihydrate will not set at all as the mixing reaches 100°C Retarders decrease the rate of setting increase setting time 7 HUMIDITY ○ A concentration of 2% Borax WHEN added to the powder will extend the setting time of some Gypsum are HYGROSCOPIC (absorbs gypsum products to several hours moisture from air) PAGE 3 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE If left in an open container, it absorbs EFFECT OF WP RATIO ON ST AND water in the air, surface of the particles COMPRESSIVE STRENGTH OF MODEL will convert to dihydrate and will increase PLASTER W/ HAND SPATULATION setting time. (LONGER) WP RATIO INITIAL ST 1-HR COMPRESSIVE 8 HARDENING SOLUTIONS (ml/g) (min) STRENGTH (MPa megapascal) harden the gypsum and also increase its 0.45 8 12.5 abrasion resistance when mixed with gypsum materials in place of water 0.50 11 11.0 C PROPERTIES OF GYPSUM MATERIALS 0.55 14 9.0 SETTING - is the time elapsing from the beginning of mixing until the material 2 MEASUREMENT OF SETTING TIME hardens MIXING TIME - is the time from the addition of the powder to the water until 1. Loss of surface gloss - use to indicate mixing is complete initial set ○ 1 minute 2. Exothermic reaction - temperature rise WORKING TIME - time available to work 3. Penetration tests with the mix a. Vicat needle ○ at the end of the working period b. Gilmore needle the material thickens and no ¼ Ib needle - initial longer workable setting time ○ 3 minutes 1 lb needle - final setting INITIAL SETTING TIME - The initial time setting time is the interval between the time the water and powder are mixed SUMMARY OF EFFECT OF MANIPULATIVE and the time that the mix can no longer VARIABLES ON PROPERTIES OF GYPSUM be poured into a mold or impression PRODUCTS viscosity is increase and can no longer be poured, rigid (but not hard) FINAL SETTING TIME - material can be separated from the impression 1 SPATULATION/MIXING The longer and faster the plaster is mixed, the faster it will set because nuclei of crystallization is broken and well distributed within the mass PAGE 4 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE The dry strength may be 2 or more times 3 DIMENSIONAL ACCURACY the wet strength Overnight in a dry environment Setting Expansion ○ Gypsum slightly expand on 3 SURFACE HARDNESS setting Plaster 0.2% to 0.3% Stone 0.08% to 0.10% The surface hardness is related to the High strength stone 0.05% to 0.07% compressive strength Thicker mix and increase spatulation Casts and dies should be allowed to set ○ will increase expansion for 1 to 2 hours or preferably longer Thinner mix and decrease spatulation before beginning laboratory procedures ○ will decrease expansion 4 DIMENSIONAL STABILITY D STRENGTH Gypsum is slightly soluble in water Strength is an indicative of the ability of Soaked in water saturated with gypsum the material to resist fracture to prevent erosion of the surface Plaster - weakest in strength Improve stone - strongest E TECHNIQUE OF USE 1 FACTORS AFFECTING THE STRENGTH A. Measuring the Water The water is usually dispensed by volume W/P RATIO in a graduated cylinder ○ thicker mix - increase strength B. Measuring the Powder ○ thinner mix - decrease strength Powder can be weighed in grams with COMPRESSIVE STRENGTH - contributes simple balance or scale to the hardness and abrasion resistance Air are present in powder. Powder should of the material be sifted TENSILE STRENGTH - ability of the C. Adding Powder and Water material to resist fracture during bending Water first before powder forces F MIXING/SPATULATION 2 TWO TYPES OF STRENGTH 1. Hand Mixing A. WET STRENGTH Done in a flexible plastic or rubber Is the strength that is measured when bowl with a stiff-bladed spatula to the sample contains some or all of the combine the water and powder water in excess of the theoretical amount Mixing is usually accomplished required for hydration with a wiping motion against the This is the typical condition after setting side of the bowl (to eliminate Cast feels wet to touch for many hours lumps and air bubbles) Mixing is 1 minute B. DRY STRENGTH 2. Mechanical mixer Is the strength that is measured when power driven and rotate at a high the excess water is not present in the speed sample PAGE 5 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE Ideal mix must be: ○ Smooth ○ Homogenous ○ Workable ○ Free of air bubbles G POURING THE MODEL Methods for pouring a model or cast 1. Boxing method 2. Pour the impression, wait to set before doing the base H DISINFECTION Models, casts and dies - spray with iodophor Ethylene oxide Immerse in 1:10 dilution of a 5% SODIUM HYPOCHLORITE FOR 30 MINS PAGE 6 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE 1 DENTAL IMPRESSION IMPRESSION MATERIALS TOPIC OVERVIEW A. IMPRESSION MATERIALS a. Dental impression b. Cast c. Properties of ideal material d. Kinds of impression taking e. Kinds of impression tray B. CLASSIFICATION OF IMPRESSION MATERIALS a. According to the manner of hardening or mode of setting b. According to use in dentistry c. According to elasticity 2 CAST A IMPRESSION MATERIALS Is the positive reproduction of the object Materials which are used to copy the impressed, made by pouring plaster or exact size of the teeth and the similar material into the impression surrounding structures; duplicate of the In indirect techniques the cast is often oral structures (teeth and its surrounding referred to as die. The wax pattern is structures) fabricated on this die ADVANTAGES OF USING A CAST OR MODEL 1. Models provide a three-dimensional view of the oral structures, thus aiding in diagnosis and treatment planning. 2. Many restorations or appliances are best constructed on casts. It may be inconvenient to both dentist and patient if these have to be made directly in the patient's mouth. 3. Models can be used to educate the patient. 4. They serve as treatment records. 5. By using casts, technical work can be passed on to technicians, saving valuable clinical time. PAGE 1 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE 2. Individual tray 3 PROPERTIES OF IDEAL MATERIAL - Own tray which is fitted in the mouth 1. Ease of manipulation and reasonable - Constructed from your study cast cost. - Used for secondary impression 2. Adequate flow properties taking 3. Appropriate setting time and - More accurate than stock tray characteristics 4. Sufficient mechanical strength not to tear or permanently deform during removal 5. Good dimensional accuracy 6. Acceptability to the patient 7. Safety 8. No significant degradation of properties 3. Perforated tray as a result of disinfection - Ready made tray made up of 9. Compatibility with all die and cast metal or plastic materials - Perforated 10. Good keeping qualities (shelf-life) - Partial or full - Used for preliminary and final impression taking 4 KINDS OF IMPRESSION TAKING 4. Water cooled tray - With small metal tubing around the tray extending to the outside 1. Preliminary impression - Use for reversible hydrocolloid taking the initial survey of the oral - May be partial or full cavity. 5. Rim locked tray Study cast is produced which is - Same used and made up of Plaster of Paris materials for perforate tray 2. Secondary, Final, Wash or Corrective - Perforated or non perforated impression - Partial or full correct the defects found on the primary impression. Cast B CLASSIFICATION OF IMPRESSION produced is working cast made MATERIALS up of dental stone 5 KINDS OF IMPRESSION TRAY 1 ACCORDING TO THE MANNER OF HARDENING OR MODE OF SETTING 1. Stock tray - ready made tray, non-perforated (without holes) 1. Thermoplastic - those that set as a result - For modeling compound of a change in temperature (materials - Used in taking preliminary that becomes soft when heated and impression hardens upon cooling) - Come in different sizes EX. Reversible hydrocolloid, waxes, Dental Compound 2. Thermoset - those that set as a result of a chemical reaction Ex. ZOE impression paste, alginate, impression plaster, rubber impression material PAGE 2 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE 2 ACCORDING TO USE IN DENTISTRY 1. Impression materials used for complete denture prosthesis - Impression plaster, impression compound and impression paste - rigid 2. Impression materials used for dentulous mouths alginates and rubber base impressions - elastics 3 ACCORDING TO ELASTICITY 1. Elastic - flexible after setting a. Reversible (agar base) and irreversible (alginate base) hydrocolloid b. b. Elastomeric (rubber base) 2. Inelastic or rigid - hard after setting (for no undercuts exist) a. Impression or modeling compound b. Impression Plasters c. Zinc Oxide and Eugenol impression paste d. impression waxes PAGE 3 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE 2 CONSISTENCIES ELASTOMERIC IMPRESSION MATERIALS Extra low - available for condensation and addition silicones Low - polysulfide TOPIC OVERVIEW Medium Heavy - polysulfide A. ELASTOMERIC IMPRESSION Putty - available for condensation and MATERIALS addition silicones a. Kinds of elastomers b. Consistencies B. POLYSULFIDE IMPRESSION B POLYSULFIDE IMPRESSION MATERIALS MATERIALS a. Composition b. Setting reaction first elastomeric impression material to c. Manipulation be introduced (1950). C. SILICONE IMPRESSION MATERIALS also known as Mercaptan or Thiokol. a. Condensation silicone b. Addition silicone D. POLYETHER IMPRESSION 1 COMPOSITION MATERIALS a. Composition and setting Base material contains reaction ○ mercaptan groups (-SH) called b. Properties polysulfide polymer c. Manipulation ○ Filler such as titanium dioxide or E. DISINFECTION OF ELASTOMERIC lithopone to provide strength IMPRESSION MATERIALS ○ Plasticizer - dibuthyl phthalate to F. ELASTOMERIC MATERIALS FOR BITE confer viscosity REGISTRATION ○ Sulfur - as accelerator Accelerator (catalyst) ○ Contains lead dioxide, filler and A ELASTOMERIC IMPRESSION plasticizer filler MATERIALS ○ lead dioxide - results in the paste being dark brown to dark gray. 'elastomer' is derived from the words ○ Oleic or stearic acid - retarder to elastic polymers control the rate of setting reaction rubber-like properties 2 SETTING REACTION 1 KINDS OF ELASTOMERS Reaction starts at the beginning of 1. Polysulfide mixing and reaches its maximum rate 2. Condensation polymerizing silicones soon after spatulation 3. Addition polymerizing silicones At this stage, a resilient network has 4. Polyether started to form During the final set, a material of adequate elasticity and strength is formed that can be removed past undercuts quite readily PAGE 1 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE COMPOSITION 3 MANIPULATION Supplied as base and an accelerator Two-paste type ○ Base contains a moderately ○ Equal lengths of base and low-molecular-weight silicone accelerator are extruded on a liquid called a dimethylsiloxane. paper pad. ○ The accelerator consists of a tin ○ A tapered, stiff-bladed spatula is organic ester suspension and an recommended. alkyl silicate such as ortho-ethyl ○ Mix for 5 to 10 seconds with the silicate. end of the spatula and then continue mixing with a wide 2 ADDITION SILICONES sweeping motion until the mix is free from streaks and uniform in color. Often called Polyvinyl Siloxane PVS If the material is medium or high Base contains of viscosity, it is placed in a tray. polymethylhydrosiloxane as well as ○ The tray is constructed to provide polymethylhydrosiloxane a uniform space of about 2 mm Catalyst or accelerator contains for the impression material. divinylpolysiloxane and platinum salt Custom acrylic trays are generally used. Both contains filler ○ The inside is painted with a Supplied as rubber cement adhesive. 1. Tubes- The base and catalyst pastes come in equal sized tubes (unlike condensation silicones). C SILICONE IMPRESSION MATERIALS The different viscosities usually come in different colors like Two types of silicones are used as orange, blue, green, etc. impression materials. 2. Cartridge - form with static ○ Condensation silicone mixing tips For use with a ○ Addition (sometimes called vinyl dispensing gun. silicone) 3. Putty jars - Two equal sized The names identify the type of plastic jars-containing the base polymerization reaction. and catalyst. 4. A larger electric driven auto dispenser and mixing device is 1 CONDENSATION SILICONE also available (Pentamix— ESPE). This machine stores larger Supplied as quantities. At the press of the ○ Base paste and low viscosity button, it dispenses and mixes the liquid catalyst (or paste catalyst) material. ○ Two-paste system ○ Two-putty system VISCOSITIES The putty can be used as a tray material in conjunction with a low viscosity silicone. This is called putty-wash Light bodied technique Medium bodied Heavy bodied Putty PAGE 2 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE Less dimensional change than MANIPULATION condensation silicones Hydrophilic Addition type high stiffness ○ A static mixing tip is placed on Pleasant odor and taste the end of the cartridge. Setting time is around 6-8 minutes. ○ The trigger is used to extrude and Mixing should be done quickly that is 30 mix base and catalyst through the seconds. Heat decreases the setting time mixing tip. Base and catalyst putties in jars are dispensed and mixed by hand until free 3 MANIPULATION from streaks. ○ Putties should not be mixed with Supplied in three mixing systems latex gloves. ○ Two tubes ○ Components in the rubber gloves ○ An automatic cartridge and will retard or prevent setting. mixing gun ○ A mechanical mixer with dynamic D POLYETHER IMPRESSION MATERIALS mixing tip Use of a tray that allows for a thickness of at least 4 mm of impression material 1 COMPOSITION AND SETTING helps in removal. REACTION ○ An adhesive should be used in the tray. Supplied as a base and catalyst Manipulation ○ Base contains polyether polymer, 1. Hand mixing colloidal silica as filler and 2. Static mixing plasticizer such as glycol ether or 3. Static mixing syringe ○ Accelerator or Catalyst contains 4. Dynamic mechanical mixing alkyl-aromatic sulfonate, filler and plasticizer Two-stage Putty-wash technique. a. Equal quantities of base and 2 PROPERTIES catalyst is dispensed. b. Mixing by kneading until uniform Working time is the shortest of any color is achieved. rubber impression material. c. A plastic sheet spacer is placed to Viscosity is high compared with that of provide space for the final other medium-viscosity impression impression material. materials. d. Making the preliminary Permanent deformation is less than impression. polysulfides but not as low as silicones. e. The completed preliminary High stiffness is indicated by the low impression. flexibility. f. The final impression material Dimensional change is lower than any dispensed in to the preliminary other rubber impression material, except impression. addition silicones. g. Simultaneously some material is Better mechanical properties than loaded in to the syringe. polysulfides h. The syringe material is injected around the prepared tooth/teeth. PAGE 3 CHESKA ALAY – DDM 3B  DENTAL MATERIALS PPT BASED 1ST SEMESTER – DOCTOR OF DENTAL MEDICINE i. The loaded tray is seated in the mouth j. The completed impression E DISINFECTION OF ELASTOMERIC IMPRESSIONS Disinfectants include neutral glutaraldehyde, acidified glutaraldehyde, neutral phenolated glutaraldehyde, phenol, iodophor, and chlorine dioxide. ○ Impressions are immersed for 10 minutes, except for chlorine dioxide for only 3 minutes. ○ Disinfection of polyether by immersion is not recommended, except for very short times in chlorine compound disinfectants. F ELASTOMERIC MATERIALS FOR BITE REGISTRATION Polyether and addition silicone have been used to take bite registrations. ○ Most of the products are addition silicones. Elastomeric bite registration materials are superior to waxes for taking bite registrations. PAGE 4 CHESKA ALAY – DDM 3B