Dental Waxes PDF

Dental wax Marketing Department Mon. Feb. 21. 2018 Dental wax Dental wax Dental wax Dental wax  Dental L tier waxes are thermoplastic materials which are in normally solids at room temperature but melt, without ___ decomp...

Dental wax Marketing Department Mon. Feb. 21. 2018 Dental wax Dental wax Dental wax Dental wax  Dental L tier waxes are thermoplastic materials which are in normally solids at room temperature but melt, without ___ decomposition, to form mobile liquids. They are essentially soft substances with poor mechanical properties and their primary use in dentistry is to form patterns of appliances prior to casting. Dental wax Natural waxes are produced from: III Plants :carnauba wax Insects :bees wax Minerals :paraffin wax Natural waxes are combined or mixed with synthetic waxes, gums, fats, oils, resins and coloring agents to form dental waxes. Dental wax Fetal Classification of dental waxes Processing Pattern Impression Boxing & Inlay Corrective Beading casting Bite Sticky RPD casting registration Utility Base plate Carding Shellac Dental wax E Dental wax Physical properties tested 1. Melting Range Dental waxes have melting range rather than melting point because they are mixture of more than one type f of wax and other additives; each has its own melting point. Melting range is a range of temperatures at which each component of the wax will start to soften and then flow. 2. Flow Flow is dependent on temperature (flow of wax is greatly increased as the melting range is III approached). For the direct inlay wax, the material must have a relatively high flow a few Eee degrees above mouth temperature (workable but comfortable). Dental wax At mouth temperature, no flow is required to ILLICIT minimize the possibility of distortion of the pattern during removal from the tooth Insufficient flow lead to lack of details and increased internal stresses. Dental wax 3. Residual stresses Waxes have low thermal conductivity making it f difficult to achieve uniform heating. Adaptation of wax to a certain shape with non free homogenous softening will result in stress set up in the material and relief of stresses lead to free distortion of the wax pattern. Dental wax 4. Dimensional Change The coefficient of thermal expansion and contraction of dental waxes is greater than any other dental material. Fester Waxes expand when heated and contract when cooled. Temperature changes due to great coefficient of thermal e expansion and contraction of the pattern wax may be a major contributing factor in the inaccuracy of the finished restoration Dental wax 5. Mechanical properties Elastic modulus, proportional limit and compressive strength of dental waxes are lower e than any other dental materials. These properties depend on temperature. e 6. Ductility Ductility of waxes1increases as the temperature f oct increases. I III Waxes with low melting point have greater ductility. Ductility of mixed waxes with wide melting range Israel is greater than those of narrow melting range Dental wax I. Pattern waxes Pattern waxes are used in the construction of metal castings and bases for dentures. 7 1. Inlay waxes These waxes are supplied in blue or green form. e Used to prepare wax patterns of inlays, crowns, & e bridges Dental wax ITE Dental wax Tette Desirable Properties 1. Not sticky to touch. 2. Low thermal expansion. 3. Completely burnt out without leaving any residue. 4. Appropriate melting ranges. 5. Soften without flaking. 6. Adequate flow to record the cavity details. Dental wax The Type I : medium wax, used in direct technique It is used directly in the mouth where it is softened and insects placed into the prepared tooth in the direct waxing technique. It has a lower melting range for the comfort of the patient for and the accuracy of the wax on removal. Has a softening point slightly higher than the mouth IIe temperature. Dental wax F Type II : soft wax, used in indirect technique It is more frequently used, where wax is melted e onto a die outside the mouth. Most dentists prefer to use this and have a dental laboratory technician to produce the wax pattern and casting. Dental wax FIffffety Manipulation inlay pattern wax 1. Direct technique Wax should be passed over flame & then remove. sets__ Process repeated until wax is uniform throughout. c e Kneaded together & shaped to prepared cavity. see Pressure applied. Carefully removed Dental wax 2. Indirect technique 1. Die lubricated 5 2. Melted wax is added in layers. 3. Cavity is overfilled & carved those 4. Final finishing with fine cloth toward the margins. Dental wax Their Wax Distortion Causes: 1. Non-uniform heating of the wax when inserted in the cavity. 2. If wax is not held under uniform pressure during cooling. 3. During carving. Dental wax To avoid: ▪ Minimal carving & change in temperature. same ▪ Invest immediately. ▪ Use warm instruments for carving. ▪ Store in fridge if necessary. 2. Casting Wax CASTING PROCEDURE 28 Dental wax They come in the form of sheets and preformed shapes, used to e construct the metal framework of partial and complete dentures. 7 Physical properties 1 1 1. They have little flow at mouth temperature and high degree of flow at higher temperature since they are used in laboratory procedures. 2. Slight degree of tackiness to maintain their position on the cast during the assembly of the pattern.  Get a a desirer Dental wax 3 3. Base plate wax Dental wax They are sheets of wax generally pink in color to simulate the color of the gingival. cesetff Physical properties f 1. The wax must not distort at mouth temperatures. face__ 2. If heated or washed up with hot water, no residue remains. 5 3. Easy to mould without flaking or tearing. 1. These sheets are layered to produce the form on which e more denture teeth are set. 2. Occlusal bite registration. 3. Spacer in custom trays. e 4. Waxing up (producing the desired contour) of the trial e denture after setting of teeth Dental wax Dental wax 6 Sept Dental wax II. Processing waxes These waxes are used primarily to aid in dental e procedures both clinically and in laboratory. 7 1. Boxing wax it willsurroundtheimpression It is supplied in the form of green or black sheets e with smooth glossy surface. Dental wax Dental wax K Physical ett properties It is easily manipulated. Slightly tacky at room temperature, allowing it to adhered to itself to secure the boxed form. Retain its shape with minimum flow. IIE Use It is used to form a gypsum model with its base in one step. Ter Technique The 1.5 inch wide, red strip of boxing wax is wrapped around the impression to produce a form into which the gypsum is poured. Dental wax 2 2. Utility wax It is also called periphery wax. It comes in orange or dark red ropes and sheets. 1Physical 77 oct properties 1. Adaptable and workable at room temp. 2. Adhesive and tacky at room temperature. Dental wax Ñ_ USES To adapt the periphery of the impression and aid in patient comfort. Dental wax 3 3. Sticky wax It comes in yellow or orange sticks. Uses IT 1. Used for alignment of fractured pieces of dentures or casts temporarily during repair. 2. Used to fix the soldered components (e.g. bridge parts during their soldering together Dental wax E e 0 Dental wax Fees Physical properties 1. It is hard and brittle at room temperature, but f when heated under flame, it becomes soft and sticky. 2. Free from tackiness at room temperature  Dental wax 4- 4 fed forrecordbase Ifetterforrecordbase Dental wax Dental wax 5 5- Carding wax Dental wax III. Impression waxes It is used to obtain impressions of the oral structures so they e exhibit high flow 100% at mouth temperature. Dental wax 7 1. Corrective impression wax It is used as a wax veneer over the original Ifip impression materials in the process of taking edentulous impressions. This wax flows at mouth temperature and is used within another (original) impression material to engaged record soft tissue fine details in a functional state. They are replaced by elastomeric impression materials.  Stra MS is ineden ma contain Dental wax Dental wax 2. Bite registration wax f It is supplied in the form of preformed horseshoe shapes. It is used to produce wax bite registrations for articulation of models. It is susceptible to distortion at temperature slightly higher than mouth temperature. Dental wax Dental wax Thank You Non Metallic Denture Base one  foot Definition The denture base is that part of the denture which rests on the tissues and carries the artificial teeth. Functions Support & retain denture teeth. Stress distribution. Improve esthetics. Requirements of denture bases o_ 1. Strength and durability. 2. Satisfactory thermal properties. 3. Processing accuracy and dimensional stability 4. Chemical stability. 5. Insolubility in oral fluids. 6. Absence of taste and odor. 7. Biocompatible. 1 7 Advantages of non metallic denture base 1. Color matches gingival tissues. 2. Easy constructed & repaired. 3. Easy to be finished & polished. 4. Easy to reline. 5. Light in weight. 6. Not expensive  tests Disadvantages of non metallic denture base. 1. Moderate mechanical properties. 2. Be scratched. 3. Do not transmit heat. 4. May cause allergy to the patient. 5. Crazing& bleaching may occur. 6. Bacterial & fungal colonization may occur.  o Types of Acrylic Resin 1. Heat cured acrylic resin 2. Chemical cured acrylic resin 3. Light cured acrylic resin  poet reaction Steps of the polymerization Dlbcl 1. Initiation: activation of the initiator by heat, light or chemical producing 2 free radicals. 2. Propagation: each free radical react with monomer converting it to new free radical, with repetition. Hesayjustread itisn'timportant 3. Termination: reaction with 2 growing chains to form the polymer.  _i 1. HEAT CURED ACRYLIC DENTURE BASE I Powder 1. Pre-polymerized poly-methyl methacrylate. 2. Initiator: benzoyl peroxide. 3. Plasticizers: make the material to be resilient. my__ 4. Pigments: give various tissues like shades. 5. Acrylic fibers: simulate the minute blood vessels. 6. Glass fibers: increase stiffness.  7 1 Liquid (present in dark glass bottle) 1. Monomer: methyl methacrylate. 2. Inhibitor: to prevent premature polymerization.  4 2. Chemical-Cured Acrylic Denture Plastics 51 (Self-curing, cold-curing or autopolymerizing resins) Is The liquid contains a chemical activator which is responsible for starting the polymerization reaction at room temperature is called tertiary amine that reacts with the peroxide initiator and sufficient free radicals are produced to initiate the polymerization reaction. Uses oh 1. Denture bases. 2. Repair of broken dentures. 3. Special trays. Advantage Denture base fabrication in short time. Disadvantages c 1. Lower mechanical properties as stiffness. 2. Higher porosity. 7L 3. Color instability due to tertiary amine.. 4.The unreacted monomer cause 2 major difficulties: Eat - It acts as plasticizer –decreased strength - Residual monomer irritate the patient’s soft tissues.  toffees 3. Light-Activated Acrylic Resin Composition UDMA (Urethane dimethacrylat) and PMMA. A photo initiator as Comphro-quinon is also added. When the material is subjected to the blue visible so light, free radicals will be released. Properties A sheet of the material is adapted to the working cast and cured for 5 min in a light-curing unit. The rope IF material is adapted as horse shoe over the cured base and the artificial teeth are arranged over it. Curing for another 5 min occur. Applications Denture bases, repair of broken dentures and special trays. Advantages 1. No MMA monomer found → reducing the possibility of allergic reaction. 2. Lower rate of polymerization reaction→ better fitness of denture base. 3. Short processing time with no need for flasking. Disadvantages It has lower mechanical and physical properties  Denture processing use two techniques IT 1. Compression molding, most common one. 2. Injection molding. Denture base construction using compression molding technique 1. Flasking procedure. 2. Wax elimination. 3. Proportioning and mixing. 4. Packing. 5. Curing. 6. Cooling &De-flasking. finishing. 7. Finishing&Polishing.  1. Flasking Is the process of investing the cast with the waxed denture in a flask so to make a mold that is used to form the acrylic resin denture base. The Inner surface of the flask is coated with Vaseline, while the base of the cast is painted with separating medium, to prevent the investment material (plaster of Paris) from attaching to the cast. c  The first layer of gypsum investment is poured I in the lower half and the cast is placed on top of the investment. After set of the first gypsum investment layer, Fell a separating medium is painted on it, to prevent the sticking of the second layer of aside gypsum investment to the first layer.  The body of the flask is put in place, then the second mix of gypsum investment is placed on the first layer and covers the wax, denture base and teeth, to fill the body. _Eeeoe Then the lid is placed on the body. staffs  2. Wax Elimination Dewaxing is done to remove the wax in the fine wax pattern, so that a mold space is created for acrylic to fill in. The flask is immersed in boiling water (100 C ) for 5 min.  Separating medium is applied to dewaxed ore mold space prior to packing the acrylic resin. E Roles of separation medium to prevent the passage of water from gypsum to resin, to minimize the passage of monomer to the plaster and to facilitate separation of the flasks.  3. Proportioning and mixing The proportion of polymer to monomer is 3:1. The powder and liquid are mixed with e stainless steel spatula and kept in a sealed glass jar during the initial stages of reaction to toe avoid the loss of the monomer by Toe evaporation. Plastic mass is produced after mixing. tot o 7 Workable mass pass through five stages; felIlfchL 1. Sandy stage: The polymer gradually settles into the monomer and grainy incoherent mass is formed. 2. Stringy or sticky stage: This stage is characterized by It a stringiness and adhesiveness if the mixture is touched or pulled apart. 3. Dough stag. The mix becomes smooth and dough like. It is no longer tacky and does not adhere to the wall of the mixing jar. stage of mix sense 4. Rubbery stage. The monomer disappears by evaporation and the mass ooh becomes more cohesive and rubber like. Non workable mass _a 5. Stiff stage. Evaporation of free monomer occurs.  During the various stages, the reaction is physical in nature and includes solution of polymer in monomer and some absorption of monomer by the polymer as well as wetting of too the polymer particles, so no polymerization reaction takes place. a  4. PACKING Packing is introduction of denture base resin into the mold cavity at the dough stage. Over-packing (placement of too much material) give excessive thickness & mal-positioning of teeth Under-packing (use of too little material)- leads to denture base porosity.  Filtered To Minimize Over-paking & Under-paking: 1. Performed in dough-like stage. 2. Shaped and adapted over the teeth. 3. Polyethylene sheet placed over the resin. 4. Designed pressed, until flask is closed. 5. Open the flask and remove the excess, then closed again. 6. Repeat this procedure untill there is no excess and obtaining metal-metal contact.  5. Curing The curing cycle described the heating processes employed to control polymerization reaction of the dough, to transform methyl methacrylate to Poly- offsets methyl methacrylate. 7  6. Cooling & Deflasking The flask should be cooled slowly ( Bench _o e cooled ), then placing under tap water for 15 Teese min, then remove the denture from the flask with care.  7. Finshing and Polishing Polishing wheel and suspension of fine pumice in water is used. so Water cooling is important to avoid excessive It heat production, so avoid warpage of the denture  I Defects during processing A. Porosity Small voids which may III be present internally or externally on the surface of the denture. Causes. 1. Excessive or elevated curing temperature which lead to boiling of the monomer. 2. Decrease the powder/ monomer ratio. 3. Lack of pressure during packing and curing. 4. Under packing (small amount of dough is used in the mold). 5. Increase powder/monomer ratio. 6. Packing in sandy stage. 2Typeof porosity b. Warpage Warpage or distortion is the change of the final shape of the upper or lower denture due to dimensional changes and release of internal stresses. 1. Too rapid cooling of the flask in tap water. 2. Excessive heating release during polishing. c. Crazing Crazing is small linear cracks that appear to originate at dentureꞌs surface. Causes 1. Alternative drying and wetting of the denture. 2. Thermal stresses as a result of differences in so coefficient of thermal expansion between acrylic denture base and porcelain teeth.  rooms Properties of acrylic denture bases 1. Mechanical properties Conventional heat-accelerated acrylic resins are still the predominant denture base materials in use, as its mechanical properties are higher than chemical cured resins.  But in general, acrylic resins are low in strength, brittle on impact if droppedone on hard surface. And fairly resistant to fatigue during repeated bending in service. Strengthening of acrylic denture base could be done for by incorporation of fibers as carbon and glass fibers. 2. Thermal properties Dental plastics are poor thermal and electrical conductors. Low thermal conductivity allows plastic denture bases to serve as an insulator between the oral tissues E and hot or cold materials placed in the mouth.  Plastics have relatively high thermal coefficients of expansion. This leads to cracking of denture base attached to porcelain teeth, due to large differences of coefficients of expansion so of acrylic and porcelain. The result is loosening of artificial teeth. 3. Water Sorption The sorption of water increases weight of the resin causing expansion. This expansion compensates for polymerization E shrinkage of the resin. Drying out of the resin is associated with shrinkage, so denture should be kept wet when not in service 4. Tissue Compatibility Completely polymerized poly methy-meth- acrylate rarely cause allergic reactions but that soooo methyl methacrylate monomer or other trace components in the monomer may produce an allergic reaction. The allergic reaction tends sooooooo to be immediate and is more likely to occur with chemically -cure resin. 5. Residual monomer Even in properly cured acrylic, 0.2 to 0.5 % of the e monomer remains unreacted. Processing at too low temperature or for too short time gives higher residual E monomer values, this should be avoided because: 1. Free monomer irritates the oral tissues. 2. Residual monomer act as a plasticizer making the resin weaker and more flexible.  if I  to ILIE sat c life  _e_ For a pot EE  4-Microwave 1  Polymerization shrinkage Heat cured acrylic resin has higher polymerization shrinkage than chemical cured one. The lower shrinkage of chemically cured type results because less stress is induced in the denture during processing. NATURE OF METAL AND ALLOY DR.WAYEL MOHAMMED HURAIB  1 oct Metal Definition A solid material which is typically hard, shiny, malleable, fusible, and ductile, with good electrical and thermal conductivity (e.g. iron, gold, silver, and aluminium)  NOBLE METALS F Hesaywedon'thavetoknowthese Noble metals have been used for inlays, crowns and FDPs because so of their resistance to corrosion in the mouth. Gold, platinum, palladium, rhodium, ruthenium, iridium, osmium, and silver are the eight noble metals. However, in the oral cavity, silver can so tarnish and therefore is not considered a noble metal. one  BASE METALS These are non-noble metals. They are important components of dental casting alloys because of their influence on physical properties, control of the amount and type of oxidation and their strengthening effect. Examples: Chromium, cobalt, nickel, iron, copper, manganese.  Metal Restorations Metal restorations and prostheses are an integral part of dentistry. Metals are among soon the strongest materials and provide strength and durability to any structure.  Metal Restorations There are two ways of constructing a metal restoration: I- Direct : have been used in modern dentistry since the introduction of direct filling gold and amalgam in the 19th century. TIIIIgp II- Indirect : were introduced into the dental profession with the patenting of the centrifugal casting machine and the lost wax technique by William H. Taggart in 1907. __e  Alloy Definition Defined as a metal containing two or more elements, at least one of which is metal and all of which are mutually soluble in the molten state.  What is the meaning of Alloys ? Noble metal content is associated with greater corrosion.  CLASSIFICATION OF DENTAL CASTING ALLOYS the not ACCORDING TO USE A. Alloys for all metal and resin veneer restorations (e.g. inlays, posts, resin and composite veneered crowns and FDPs). B. Alloys for metal-ceramics restorations (e.g. PFM crowns and FDPs). C. Alloys for removable dentures (e.g. RPD frames and complete denture bases).  CLASSIFICATION Proper OF DENTAL CASTING Custom Impression ALLOYS Tray Extension CLASSIFICATION OF DENTAL CASTING ALLOYS street BASED ON YIELD STRENGTH AND PERCENT ELONGATION Type I Soft Type II Medium Type III Hard Type IV Extra-hard  CLASSIFICATION OF DENTAL CASTING ALLOYS eat ACCORDING TO NOBILITY (ADA 1984) High noble metal alloys (HN) Contains > 40 wt% Au and > 60 wt% noble metals Noble metal alloys (N) Contains > 25 wt% of noble metals Base metal alloys Contains < 25 wt% of noble metals  CLASSIFICATION OF DENTAL CASTING ALLOYS off CLASSIFICATION ACCORDING TO HARDNESS II Small inlays, Class III and Class V cavities which are not subjected to great TYPE I SOFT stress. TYPE II MEDIUM Abutments, pontics, full crowns. Inlays, crowns and bridges, situations where there may be great stresses TYPE III HARD soooo involved. They usually can be age hardened. Inlays subjected to very high stresses, partial denture frameworks and long TYPE IV EXTRA-HARD span bridges. They can be age hardened.  CLASSIFICATION OF DENTAL CASTING ALLOYS 1 ACCORDING TO MAJOR ELEMENTS A. Gold alloys B. Silver alloys C. Palladium alloys D. Nickel alloys E. Cobalt alloys F. Titanium alloys  Want FUNCTIONS OF CONSTITUENTS The lost wax casting technique has been used since ancient times to convert wax patterns to cast metal.  preteens GENERAL REQUIREMENTS OF CASTING ALLOYS 1. They must not tarnish and corrode in the mouth. 2. They must be sufficiently strong for the intended purpose. 3. They must be biocompatible (nontoxic and nonallergenic). 4. They must be easy to melt, cast, cut and grind (easy to fabricate).  GENERAL REQUIREMENTS OF CASTING ALLOYS 5. They must flow well and duplicate fine details during casting. 6. They must have minimal shrinkage on cooling after casting. 7. They must be easy to solder.onlyonecaseofbridge  te To GOLD ALLOYS (FOR ALL-METAL RESTORATIONS) etter Pure gold is a soft and ductile metal and so is not used for casting dental restorations and appliances in its pure state. It is alloyed commonly with copper, silver, platinum, nickel and zinc. Alloying gold with these metals not only improves its physical and mechanical properties but also reduces its cost.  FUNCTIONS OF CONSTITUENTS e Gold It provides tarnish and corrosion resistance and has a desirable appearance. It also provides ductility and malleability.  FUNCTIONS OF CONSTITUENTS Copper It is the principal hardener. It reduces the melting point and density of gold. It gives the alloy a reddish color. It also helps to age harden gold alloys. Problem soweusesilvertomodifythecolor  Proper FUNCTIONS Custom Impression OF CONSTITUENTS Tray Extension Silver It whitens the alloy, thus helping to counteract the reddish color of copper. It increases strength and hardness slightly.  FUNCTIONS OF CONSTITUENTS Platinum It increases strength and corrosion resistance. It also increases melting point and has a whitening effect on the alloy. It helps reduce the grain size.  FUNCTIONS OF CONSTITUENTS Palladium It is similar to platinum in its effect. It hardens and whitens the alloy. It also raises the fusion temperature and provides tarnish resistance. It is less expensive than platinum.  T PROPERTIES OF GOLD ALLOYS to COLOR Traditionally, the gold alloys were gold colored. The color of modern gold alloys can vary from gold to white. It depends on the amount of whitening elements (silver, platinum, palladium, etc.) f present in the alloy.  PROPERTIES OF GOLD ALLOYS MELTING RANGE Ranges between 920–960 °C. The melting range of an alloy is important. It indicates the type of investment required and the type of heating source needed to melt the alloy.  PROPERTIES OF GOLD ALLOYS YIELD STRENGTH The yield strength for : X Type III — 207 MPa Type IV — 275 MPa  PROPERTIES OF GOLD ALLOYS HARDNESS The hardness indicates the ease with which these alloys can be cut, ground or polished. Gold alloys are generally more user rottt friendly than the base metal alloys which are extremely hard. The hardness values Type III — 121 MPa Type IV — 149 MPa  PROPERTIES OF GOLD ALLOYS ELONGATION It indicates the ductility of the alloy. A reasonable amount is required especially if the alloy is to be deformed during clinical use, e.g. clasp adjustment for removable partial dentures, margin adjustment and burnishing of crowns and inlays. Type I alloys are easily furnished. seems Alloys with low elongation are very brittle. Type III—30–40% Type IV—30–35%.  PROPERTIES OF GOLD ALLOYS MODULUS OF ELASTICITY This indicates the stiffness/flexibility of the metal. Gold alloys are more flexible than base metal alloys  PROPERTIES OF GOLD ALLOYS TARNISH AND CORROSION RESISTANCE Gold alloys are resistant to tarnish and corrosion under normal oral conditions. This is due to their high noble content.  PROPERTIES OF GOLD ALLOYS CASTING SHRINKAGE All alloys shrink when they change from liquid to solid. The oo casting shrinkage in gold alloys is less (1.25–1.65%) when compared to base metal alloys.  PROPERTIES OF GOLD ALLOYS CASTING SHRINKAGE The shrinkage occurs in three stages: so 1. Thermal contraction of the liquid metal. 2. Contraction of the metal while changing from liquid to solid state. 3. Thermal contraction of solid metal as it cools to room temperature. T Shrinkage affects the fit of the restoration.  PROPERTIES OF GOLD ALLOYS BIOCOMPATIBILITY Gold alloys are relatively biocompatible.  PROPERTIES OF GOLD ALLOYS CASTING INVESTMENT Gypsum-bonded investments can be used for low fusing gold alloys. see