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Model and die material

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Model and die material Model and die material Presentation Transcript

  • PREPARED BY:DR.RAHUL PATEL M.D.S. PART 1
  • CONTENTS Introduction Review of literature Definition Requirements of cast Requirements of die preparation Ideal requirements of die material Materials Methods Bibliography
  • INTRODUCTION Direct fabrication of patterns for extracoronal restorations in the mouth is inconvenient, difficult, time consuming, and virtually impossible. A cast and die system captures the necessary information so that it can be transferred to the laboratory.Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
  • REVIEW OF LITERATURE James Stackhouse (1970) conducted a study concerning the accuracy of stone dies affected by the dimensional changes in rubber impressions They concluded that1. More uniform dies were produced from silicon2. One silicone material was more significant than the others3. Perforated tray technique caused the dies to be undersized in diameter4. Bench setting caused the stone dies to be shorter in length and thicker in diameter
  •  Gerald T Nomura et al(1980) evaluated the accuracy, fit, detail registration and Knoop hardness of 3 commercially available resin die systemsThey concluded :1. Complete crown epoxy resin dies are undersized2. MOD onlay epoxy resin dies are accurate3. Detail duplication of epoxy resin dies is comparable to die stone4. Hardness values of epoxy resin are less than those of stone
  •  Myers M., Hembree J.H.(1982) – conducted a study on the relative accuracy of four removable die systems. 4 die systems were studied i.e. the brass dowel pin, the Plastipin, the J-pin, & Logix Model System & they determined the vertical shift & the horizontal shift of the dies. They concluded that Plastipin exhibited least amount of horizontal shift & the brass dowel pin exhibited greatest shift in both directions.
  • DEFINITION MODEL : “A MODEL IS A REPLICA OF A TEETH AND THE ASSOCIATED SUPPORTING BONY TISSUE OF A JAW,WHICH IS PREPARED FROM AN IMPRESSION.” DIE : “A POSITIVE REPRODUCTION OF PREPARED TEETH AND CONSISTS OF A SUITABLE HARD SUBSTANCE OF A SUFFICIENT ACCURACY.”
  • REQUIREMENTS OF THE CAST  Accurate surface detail  Free of voids.  Precise articulation.  Soft tissue should be reproducedRosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
  • REQUIREMENTS FOR THE DIE PREPARATION  Reproduce the prepared tooth exactly.  No bubbles or void  The remaining unprepared tooth structure immediately cervical to the finish line should be 0.5 to 1mm visible.  Adequate access to the margin is imperative.Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
  • IDEAL REQUIREMENTS FOR DIE MATERIAL  Accurate  Dimensionally stable  Setting expansion and contraction, variations in response to change in temperature need to be minimum  It should reproduce the fine detailsRosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
  •  Strong and durable  Withstand the carving and finishing procedures  The color should contrast that of the wax to ease the manipulation  Economical  Easy to useRosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
  • MATERIALS  It includes :  Gypsum  Type1-Impression Plaster  Type2-Model Plaster  Type3-Dental Stone  Type4-Dental Stone(High strength)  Type5 –Dental Stone(High strength and high expansion)  Resin  Epoxy Resin  Polyurathane  Electroplated Dies  Copper plated  Silver plated  Flexible Die Materials  Amalgam used die material  Metal sprayed dieRosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
  • GYPSUM  Gypsum(CaSO4.2H2O) is a mineral mined product used extensively in dentistry to make dental models.  In its unrefined state, gypsum is the dihydrate form of calcium sulfate.  Model plaster  Commonly called plaster of Paris, is used primarily for pouring preliminary impressions and the making of diagnostic models.  Dental stone  For use as a working model when a more durable diagnostic cast is required.Philips (1992) Science of dental materials 11th edition W.B Saunders
  • - Die Stone, High Strength (Type IV): •α-hemihydrate of the “Densite” type. •Cuboidal shaped particles & reduced surface area produce such properties without undue thickening of mix. •W/P ratio – 0.22 – 0.24 •Setting time - 12±4min. •2hr Setting Expansion – Maxi. 0.10% •1hr compressive strength – 5000psi.Philips (1992) Science of dental materials 11th edition W.B Saunders
  • Die Stone, High Strength, High Expansion (Type V)  Higher compressive strength than Type IV.  Setting Expansion – 0.10% - 0.30%.  W/P ratio – 0.18 – 0.22  Setting time - 12±4min.  1hr compressive strength – 7000psi. GYPSUM HARDENERPhilips (1992) Science of dental materials 11th edition W.B Saunders
  • RESINS EPOXY RESIN  Used effectively with rubber based impression materials  available in the form of a paste to which an activator is added to initiate hardening  Care should be taken that the activator not come in contact with the skin as it is toxicPhilips (1992) Science of dental materials 11th edition W.B Saunders
  • PROPERTIES  Working time -15min  Setting time 1 to 12 hours depending on the products  Compressive strength after 7days is 16,000psi  Abrasion resistance is superior to stone dies  Dimensional change due to shrinkage during polymerization is between 0.03% to 0.3% and continues to occur for up to 3 days  Epoxy resin are very viscous when pored hence porosity can occurPhilips (1992) Science of dental materials 11th edition W.B Saunders
  •  Advantages 1. More resistant to abrasion 2. Dimensionally stable  Disadvantage 1. The epoxy resin cannot be readily introduced into the details of a large impression as dental stone and requires a centrifugal machine for the same 2. It shrinks by about 0.1to 0.2% in about 24 hours 3. It is expensivePhilips (1992) Science of dental materials 11th edition W.B Saunders
  • ELECTROPLATED DIES  Electroplated dies are the ones that are produced when an impression material is electroplated  When a die is made in this manner this process is known as electroforming  The impression materials which can be electroplated are impression compound and elastomeric materials  The types of dies are- - Copper plated dies - Silver plated dies  The popularity of copper plated dies began in the early 1930’sPhilips (1992) Science of dental materials 11th edition W.B Saunders
  • ADVANTAGES  No dimensional changes occur during electro deposition of a metal  It reproduces the impression accurately  The die is tough and has good strength characteristicsPhilips (1992) Science of dental materials 11th edition W.B Saunders
  • COPPER PLATED DIES  Impression compound is usually copper plated  The impression material is the cathode and it is connected to the anode which is made of electrolytically pure copper and is immersed in the plating solution so that the area of copper immersed is approximately equal to that of the impression to be plated  COMPOSITION OF SOLUTION FOR COPPERPLATING BATHS Copper Sulphate (crystals) - 200gms H2SO4 (conc) - 30ml Phenol Sulfonic Acid - 2ml Water Distilled - 1000mlPhilips (1992) Science of dental materials 11th edition W.B Saunders
  • TECHNIQUE The surface of the impression is coated with a conductor of electricity such as graphite, copper powder, silver before it is attached to the cathode lead wire. This process is known as “metalizing”. This determines the surface character of the finished die The copper sulphate is the source of copper, the sulphuric acid increases the conductivity and phenol sulfonic acid helps to assist the penetration of the copper crystals into the deeper parts of the impression Initially 15 ma current is given which can later be increased to 2 to 3 times the initial current The plating is allowed to proceed for 12 to 15 hours (usually overnight)Philips (1992) Science of dental materials 11th edition W.B Saunders
  • SILVERPLATED DIES  Silver plating is done over rubber based impression materials  Silver plated dies show more vertical change than stone dies, the difference being between 0.25% to 0.45% depending on the impression material , while the horizontal changes are not significant  COMPOSITION OF THE SOLUTION Silver cyanide - 36gm Potassium cyanide - 60gm Potassium carbonate - 45gm Water (distilled) -1000mlSilver plated dies marginal accuracy of cast restorations J Prosth Dent 51;1984: 768-772
  • Technique  The impression is first made conductive by brushing the surface with powdered silver  A current of 5ma is suitable to start plating a single tooth impression and 10 ma for larger areas  Once a layer of silver is deposited the current can be doubled or trebled  Time period is usually 12 to 15 hoursSilver plated dies marginal accuracy of cast restorations J Prosth Dent 51;1984: 768-772
  • FLEXIBLE DIE MATERIALS  They are similar to heavy bodied silicone or polyether impression materials  Selection of a compatible die and impression material is very important in case of flexible dies  Advantages over die stone  Rapid setting  Ease to removalComparision of surface detail reproduction of flexible die materials J Prosth Dent 1998; 80:485-9
  • AMALGAM DIES  Model amalgam is similar to silver amalgam which is used for fillings  It is used to make hard metal dies which reproduce fine details and sharp margins from impression compound of prepared teeth  They cannot be made in hydrocolloid impressions as they cannot withstand condensation pressure  After packing the impression with amalgam the die can be removed after a minimum of 12 hours, by gently warming the compoundPhilips (1992) Science of dental materials 11th edition W.B Saunders
  •  As amalgam is a good conductor of heat , softened wax applied to them cools rapidly  This may produce internal stresses which may distort the wax pattern after removal from the die  Sudden cooling of the wax may also result in contraction of the wax away from the die  A separating agent is needed as with die stonePhilips (1992) Science of dental materials 11th edition W.B Saunders
  • METAL SPRAYED DIES  A bismuth – tin alloy which melts at 138oCcan be sprayed directly on to an impression to form a metal shell which can than be filled with dental stone  A metal coated die can be obtained rapidly from elastomeric impression material  Disadvantage the alloy is soft care is needed to prevent abrasion of the diePhilips (1992) Science of dental materials 11th edition W.B Saunders
  • CAST & DIE SYSTEMS 1) Working cast with removable die i. Straight dowel pin ii. Curved dowel pin iii. Di-lok tray iv. Pindex system 2) Working cast with separate die 3) DVA model system 4) Zeiser model systemShillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • STRAIGHT DOWEL PIN  The brass dowel pin is one of the most accurate dowel types in terms of resisting horizontal displacement and the second lowest in vertical deviation of four types of removable dies.  A dowel pin is positioned over each prepared tooth in the impression.  Place a dowel between the arms of a bobby.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  •  Push a straight pin between the arms of the bobby pin and into the impression material on both the buccal and the lingual surfaces of each tooth to have a dowel pin placed over it.  Stabilize the dowel in the bobby pin.  Pour die stone into the impression, filling the impressions of the teeth and covering the knurled end of the dowel pin.  The pin should parallel the long axis of the preparation.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  •  When the stone is hard and dry, use a saw frame with a thin blade There should be a cut on the mesial and distal side of each die, and the cuts should taper toward each other slightly from occlusal to gingival.  Take the die form the cast and trim away excess stone gingival to the finish line.  Complete the trimming of the die with a no.25 blade in the laboratory knife and then mark the finish line with the red pencil.  Repeat the procedure for each die on the cast.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • CURVED DOWEL PIN  To install pin before pouring the impression, use finger pressure to insert tip of dowel into large opening of position bar.  Hold the bar faciolingually, so that head of the dowel is 1-2mm into the proposed area of impression.  The tail of dowel extends facially; however if the tooth is linguoversion, turn it towards lingual side for easy removal.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  •  Insert a straight pin into one of 3 holes into the facial aspect of bar and into the facial flange of impression and another pin into lingual flange through lingual holes of bar.  The dowel should not touch the impression and its head should be parallel to long axis of prepared tooth or teeth.  This procedure is repeated for all abutments and pontic areas.  One pin is placed near the center of each segment of unprepared teeth, this wall help in removal of segment for better access of gingival wax pattern.  Impression is poured with die stone until it covers heads of dowel. This will fill the impression about 4 mm above gingival finish line.  The straight pins and positioning bar are removed as soon as stone is set.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • To assist in orienting each large segments of unprepared teeth, cut a 2mm deep hole on either side of each dowel with a large acrylic bur. Petrolatum is applied on stone and also an exposed part of dowel for easy separation from the base.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • •Impression is boxed, allowing the tails of the dowels to extend slightly through the heat softened wax.•Fill the boxed impression with dental stone. The dowel should be covered by atleast 2mm of stone. •After the stone has hardened, make vertical saw cuts on either side of each die. •A die is removed by pressing the dowelShillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • TO PLACE THE DOWELS AFTER THE CAST HAS BEEN MADE. •Pour the impression with die stone to form a horseshoe shaped working cast. •Trim the bottom of cast flat to level 10mm from the necks of teeth.This is done because thin cast are easy to saw and short dowels are more stable than larger ones. •Drill a 5mm deep hole in the bottom of the cast directly under the center of each prepared tooth, pontic area, and segment containing unprepared teeth. •This can be made with 2mm diameter drill in hand piece or drill press.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • •Clean the dowel holes, insert the curved dowel pin properly and then adjusted for proper fit. •Cement the dowels into holes one at time with placing a drop of cyanoacrylate cement into each hole. •The head of a curved dowel is seated into the holes.•Seat the heads completely with tail pointing facially.•Then same procedure of pouring base and preparing diesis repeatedShillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • PINDEX SYSTEM(Coltene/Whaledent,Mahwah,NJ)  In the pindex system a reverse drill press is used to create a master cast with dies that can be removed and replaced repeatedly with great precision.  The impression is poured without positioning and attaching dowel pins beforehand.  The machine accurately drills parallel holes from the underside of trimmed cast.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • PINDEX SYSTEM Diagram showing the pindex machineShillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • •Pour the impression, adding approximately 20mm of stone. •Wet the cast prior to trimming •Then trim the bottom of the cast, resting the heels on the table of the trimmer. •It should sit perfectly flat on a tabletop, and its thickness must be a minimum of 15mm.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • •Periphery of the cast should be trimmed. •Remove any excess stone in the palate/tongue area with an arbor band on a lathe. •The lingual border of the cast should taper slightly toward the base to facilitate removal of the dies from the cast later. •The faciolingual width -20mm. •Use a pencil mark the desired location of the pins on the occlusal surfaces of the teeth or preparations.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • •Place the prepared cast on the worktable and align the first pencil mark with the illuminated dot from the light beam director. •Using both hands, exert firm downwards pressure on the cast with thumbs. •Raise the handle bar with slow, even pressure and the drill assembly moves upwards cutting the pinholes. •When proper depth is achieved, red light goes off. •Same procedure is repeated with each mark. •For better results, cast is made slightly damp to prevent dust formation.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • •Compressed air and brush is used to remove debris from holes. The pin holes are refined with hand reamer. •Cyanoacrylate cement is placed on the pins prior to cementing the pin tips. •Shorter pins are placed before the long pins in lingual or palatal holes and long pins in the facial holes.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • •White sleeves are placed on the long pins and gray sleeves on the short pins. •The bottom of the cast is lightly coated with the petrolatum. •Gray sleeves are blocked with small amount of molten wax to prevent the sleeve from filling with stone when secondary base is added. •Strip of utility wax along the ends of the long pins to facilitate removal of the dies later.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • •A palatal or tongue filler is made of boxing wax. •The filler is seated to the cast. •Boxing wax is applied aaround the cast. •Base is poured with the die stone.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • •When stone becomes hard, the cast is seated in the base former. •Saw cuts are premarked with the pencil. •Then dies are sectioned from the underside. •It may also be sectioned from the occlusal aspect.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  •  After the die are sectioned, trim them in a conventional manner.  Mark the finish line with red pencil.  Apply die hardener and die spacer.  Then place the completed cast on the articulator and then cast is ready for fabrication of the wax pattern.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • DI-LOK TRAY SYSTEM  A snap apart plastic tray with internal orienting grooves and notches is used to reassemble working cast and dies.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • TECHNIQUE  The cast should be poured in a U shape, with no stone in the center building it up to 2.5cm. (1.0 inch)  A lingual side of the cast base is trimmed with an arbor band.  Horizontal grooves are cut in the base to for retention.  When stone has set for 1 hr, separate it from impression.  Cast is trimmed in horseshoe configuration to fit in Di-lok tray and the buccal border is tapered towards base with arbor band.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  •  Soak the base of cast with water for 5 min. Pour the base in tray, until ¾ of its is filled Seat the cast on tray; in such a way that cervical line of the prepared teeth should be approximately 4mm above the level of base. Wipe off the excess stone. Allow the stone to set until it is hard and dry . To complete the dies, the cast must be removed from the tray.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • •Disassemble the tray by lifting the back up, and then slide the buccal segment forward. •Then with a saw frame and a thin saw blade, cut between the prepared tooth and the adjacent tooth. •The saw cut should start in the interdental papilla area and extend downward on a very slight taper. •The occlusal saw cut should extend three- quarters of the way through the stone base. •Use finger pressure to break the die and attached teeth from the cast.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • •Remove excess stone gingival to the finish line with a pear-shaped acrylic bur. •Then cast and dies are reassembled in the tray. •Then the cast and tray mounted on the articulator. •When the stone has set, the articulated cast in the Di-lok tray is ready for the fabrication of the wax pattern.Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence
  • WORKING CAST WITH SEPARATE DIE(MULTI-POUR TECHNIQUE)  ADVANTAGES  Simple  Slightly more accurate.  Minimum trimming.  DISADVANTAGES  Difficult to transfer complex or fragile wax patterns from cast to die.  Seating the pattern on the cast may be problematic.  Technique can be used with elastomeric impression materials.Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
  •  The area of preparation is poured with the stones in small increments.  When set,it is separated.A second pour is then made of the entire arch. •The first pour which is more accurate is trimmed into a die with a handle. •A properly trimmed die handle is slightly larger in diameter than the preparationRosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
  • •Improperly trimmed die with a handle that meets the preparation at an angle •Handle should be 1 inch long •The die is trimmed with an acrylic bur•Shaping of the handle near the finish line is completed with ascalpel •The die is smoothened below the finish line with the discoid end of a tanner carver•The prepared finish line on the die should be outlined with a redpencil. •Die relief agent is painted on the preparation-20 to 40 mmRosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
  • DVA Model System:- Trimmed impression on Marking dowel pin locations alignment fixture. on clear plate Drilling holes for dowel pins Inserting dowels in the as marked baseplateRosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
  • Impression is poured, stone placed around dowel pins & alignment fixture replaced over poured impression Set cast is removed from baseplateRosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
  • Cast is trimmed Cast is sectioned Trimmed working casts using the DVA Model SystemRosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
  • ZEISER MODEL SYSTEM Zeiser Model System Impression is leveled, blocked out with silicone putty,& positioned over baseplate Pin locations are determined & the pinholes drilled in the base.Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
  • Pins are inserted into the Impression is poured base. Base is inverted into the stoneRosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
  • Cast is separated from the impression when set & then separated from the base. Sectioned cast Precision saw aidssectioning Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby
  • BIBLIOGRAPHY1. Philips (1992) Science of dental materials 11th edition W.B Saunders2. Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby3. Shillenberg (1981) Fundamentals of fixed prosthodontics 3rd edition Quintessence4. Silver plated dies marginal accuracy of cast restorations J Prosth Dent 51;1984: 768-7725. Comparision of surface detail reproduction of flexible die materials J Prosth Dent 1998; 80:485-96. An investigation of epoxy resin dies J Prosth Dent 1980;44:45-9
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