Die materials/ dental implant courses
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The document discusses various die materials used in dental applications, detailing their properties, manufacturing processes, advantages, and disadvantages. It covers materials such as gypsum, electroplated dies, epoxy resins, and amalgam, highlighting their ideal requirements and suitability for different tasks. The conclusion emphasizes that high-strength stones (types IV and V) are among the most successful die materials, while also noting that resin or metal dies may be preferable for metal-ceramic restorations.
Die materials/ dental implant courses
- 1. DIE MATERIALS INDIAN DENTAL ACADEMY Leader in continuing Dental Education
- 2. CONTENTS • Introduction • Ideal requirements of die materials • Types of die materials - Material Science - Advantages - Disadvantages - Indications and contraindication ● Summary and conclusion ● References
- 3. DEFINITION A die is working replica of a single tooth, sveral teeth or tissue surface.
- 4. MATERIALS USED FOR FABRICATION OF DIES • Gypsum products • Electroformed dies • Epoxy resins i.c silica filled and aluminium filled • Amalgam dies • Metal sprayed dies • Ceramic dies • Divestments • Polyester and acrylic
- 5. IDEAL REQUIREMENTS 1. It should be accurate 2. It should be dimensionally stable under normal conditions of use and storage 3. Setting expansion and contraction, variations in response to change in temperature need to be minimum 4. It should reproduce the fine details such as prepared and unprepared tooth satisfactorily
- 6. 5. It should be strong and durable and be able to withstand the subsequent manipulative procedures without abrasion or fracture 6. They should withstand the carving and finishing procedures 7. The color should contrast that of the wax to ease the manipulation 8. Economical 9. Easy to use
- 7. GYPSUM • Gypsum is a mineral mined in various parts of the world • The mineral which is used for dental purposes is nearly pure calcium sulphate dihydrate (CaSo4 . 2H2O) • The most commonly used die materials are Gypsum type IV (dental stone, high strength), Gypsum type V (dental stone, high strength, high expansion )
- 8. Manufacture • Gypsum is the dihydrate form of calcium sulphate CaSo4.2H2O • It is ground and subjected to temperature of 110 to 120o C to drive off the water of crystallisation • CaSo4.2H2O (CaSO4)2 + H2O
- 9. • The improved stone is made by removal of the water of crystallization which is achieved by addition of another chemical such as boiling in 30% calcium chloride solution, after which the chloride ions are washed away and the calcium sulphate hemihydrate is dried and ground to the desired fineness • The improved stone consists of α hemihydrate • These crystals are prismatic and more regular in shape than those of plaster
- 10. DENTAL STONE, HIGH STRENGHT (TYPE IV) • ADVANTAGES • It has good strength , hardness (aprroximately 92 RHN) • The surface hardness increases more rapidly than the compressive strength (as the surface dries quickly) which is an advantage as the surface resists abrasion while the core of the die is tough and is less subject to accidental breakage
- 11. • DISADVANTAGES • Poor resistance to abrasion. In order to overcome this gypsum hardeners have been used (colloidal silica) this does not improve the strength but improves the abrasion resistance by as much as 100% • Certain low viscosity resins such as cyanoacrlates can also be used to improve the strength
- 12. • Resin strengthened gypsum products such as Resin Rock have high strength and low expansion • Other material which can be added are gum arabic, calcium hydroxide mixture etc • But it is easier to use a die spacer with dental stone . • The die spacers which can be used are resins, model paint, certain paint on liquids, coloured nail polish or thermoplastic ploymers dissolved in volatile solvents
- 13. DENTAL STONE, HIGH STRENGTH, HIGH EXPANSION (TYPE V) • ADVANTAGES • Higher compressive strength than the Type IV • Setting expansion has increased from 0.1to 0.3% (the higher expansion compensates for the alloy solidification shrinkage )
- 15. • Impression materials which can be used with gypsum are impression compound, Zinc oxide eugenol, Agar, alginate hydrocolloid, silicones and polyether rubber based material • Increase in hardness of stone dies poured against impressions varies from - 2% for silicones - 110% for polyether - 70% for agar - 20% for polysulphide • The lubricants or die separators which can be used to prevent wax from adhering to stone are oils, liquid soap, detergents and a number of commercially available preparations
- 16. • If less setting expansion is desired , potassium sulphate (accelerator )or borax (retarder) are added to the gauging water , which limits the setting expansion to 0.01% • If a die slightly larger than the prepared tooth is required then colloidal silica can be added to the gauging water or the surface can be coated with resins
- 17. • Stone dies may be from 0.02% to 0.05% larger than the master to 0.04% to 0.25% smaller than the master depending on the location of the measurement and the impression material used • In general occluso- gingival changes are greater than bucco-lingual or mesio-distal
- 18. DIVESTMENT • A commercial gypsum bonded material called divestment is mixed with colloidal silical liquid. • The die is made from this mix , wax pattern is constructed on it, and then the entire assembly (die+ pattern) is invested in a mixture of divestment and water, thereby eliminating the possibility of distortion of pattern on removal from the die or during setting of the investment • Setting expansion is 0.9% • Thermal expansion is 0.6% when heated to 677o C • It is highly accurate for conventional gold alloys • It is not recommended for high fusing alloys like metal ceramic restorations .
- 19. 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’s
- 20. • ADVANTAGES • No dimensional changes occur during electro deposition of a metal • It reproduces the impression accurately • The die is tough and has good strength characteristics
- 21. Apparatus • A transformer and rectifier to reduce the voltage of the domestic supply and to convert the AC current to DC current • The low voltage direct current passes through a variable resistor, which is used to regulate the current and modify the rate at which the metal is deposited • A milliammeter that indicates the current passing through the bath
- 22. 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 - 1000ml
- 23. • 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)
- 24. • Points to be noted • If too high a current is used the copper deposit will be friable and granular in nature • High current densities also produce a heavier deposit on those areas of the impression that are nearest to the anode • Rapid plating can result in a failure to cover adequately the deeper areas of the impression
- 25. • The quality of deposit obtained with a freshly made solution is not as good as that obtained with a solution that has been in use for some time • Loss of water from evaporation should be replaced from time to time to maintain correct concentration of the solution • The sulphuric acid decomposes when the solution is in use and a few ml of the acid should be added after few weeks use
- 26. • In copper plating the distance between the anode and the impression to be coated affects the quality of the plating; the greater is the anode to impression distance , the more even is the quantity of copper deposited over the impression • 6 inches is considered to be suitable distance , if the distance is reduced then more copper is deposited on the more superficial areas of the impression leaving the deeper areas inadequately plated
- 27. SILVERPLATED DIES • Silver plating is done over rubber based impression materials • Though it is possible to copper plate rubber based dies the results are not always consistent • 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 • A pure silver anode and a silver cyanide plating solution is required • COMPOSITION OF THE SOLUTION Silver cyanide - 36gm Potassium cyanide - 60gm Potassium carbonate - 45gm Water (distilled) -1000ml
- 28. • 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 hours
- 29. • Points to be noted • The solution used is poisonous and extreme care should be taken that the hands, working area and clothes do not get contaminated • Accidental contact of the solution with acid will produce hydrogen cyanide which is an extremely poisonous gas • The plating bath should have a cover to control evaporation and dissipation of fumes
- 31. • Problems in silverplating 1. Faulty conduction – the ammeter may show current flowing but the impression does not plate or plates irregularly or slowly. This difficulty is due to a short circuit through the electrolyte usually due to the exposure of the conducting wire to the solution 2. Exhausted solution- plating is very slow and the deposit is discoloured. The solution should be discarded and replaced with a fresh one
- 32. 3. Over concentrated solution- sometimes the ammeter reading drops rapidly to zero after the impression is placed in the bath. Resetting of the current regulator is followed by another drop to zero, this is due to too concentrated solution. Adding distilled water and rinsing the silver anode in distilled water will solve the problem An over concentrated solution will also cause softening of the rubber and discoloration of the stone areas of the cast 4. Silver anode too small- an anode that is smaller than the impression will lead to slow and irregular plating
- 33. RESINS • Two types of die materials are available 1. Epoxy resin 2. Polyurethane • Of the two epoxy resin is more commonly used these are self curing acrylic materials with fillers either metallic or ceramics
- 34. EPOXY RESINS • They are used effectively with rubber based impression materials • They cannot be used with water based agar and alginate impression materials because the water retards the polymerisation of the resin • It is 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 toxic
- 35. PROPERTIES • Working time -15min • Setting time 1 to 12 hours depending on the products • Knoop hardness no is 25 KHN+/-15 less than that of high strength stone 77 KHN • 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 occur
- 36. • Advantages 1. It is more resistant to abrasion and is less stronger than dental stone 2. It is reasonably 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 expensive
- 38. 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 compound
- 39. • 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 stone
- 40. 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 removal
- 41. METAL SPRAYED DIES • A bismuth – tin alloy which melts at 138o Ccan 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 die
- 42. CERAMIC DIE MATERIALS • A material for the production of die on which porcelain restorations are to be fabricated with out the use of a platinum foil matrix to form the dies heating to over 1000o C is necessary this can be used for all ceramic crowns and veneers • A ceramic materials supplied as a powder and liquid and mixed to a putty like consistency after 1 hour the material is removed form the impression and fired at 600c C for 8 min to produce a hard stone die
- 43. REVIEW OF LITERATURE • Gerald T Nomura et al evaluated the accuracy, fit, detail registration and Knoop hardness of 3 commercially available resin die systems • The control used was improved stone • Impressions were made of each MOD and complete crown preparation • A total of 80 dies were obtained • 40 die registrations were also made , 10 of each material • 4 dentists were selected to see the master castings on each die and to evaluate it as fit or non fit
- 44. • The fit of each casting was confirmed by seating it on the die upon which the wax pattern was made • The author concluded that 1. Complete crown epoxy resin dies are undersized 2. MOD onlay epoxy resin dies are accurate 3. Detail duplication of epoxy resin dies is comparable to die stone 4. Hardness values of epoxy resin are less than those of stone
- 45. • James Stackhouse (1970) conducted a study concerning the accuracy of stone dies affected by the dimensional changes in rubber impressions • Material used were three silicone rubber impression materials • Impression techniques used were 1. Heavy body with wash syringe material 2. Perforated tray and the heavy body impression material was also perforated 3. Simultaneous double mix technique • 10 stone dies were made of each material/ technique/ time period groups • More than 500 dies were made
- 46. • The author concluded that 1. More uniform dies were produced from silicon 2. One silicone material was more significant than the others 3. Perforated tray technique caused the dies to be undersized in diameter 4. The first and third technique were not significantly different from the other 5. Bench setting caused the stone dies to be shorter in length and thicker in diameter
- 47. • B. J. Crispan et al conducted a study of the marginal accuracy of cast restorations • The impression materials used were Permlastic, Impregum, Xantoprene and Reprosil • 3 silver plated dies and 3 stone dies were fabricated from each of the 4 impression materials • The author concluded that 1. The marginal accuracy of crowns fabricated on silver plated dies is as accurate as crowns fabricated on stone dies 2. Silver plated dies fabricated from Reprosil produced more accurate crowns than other dies tested 3. Silver plated dies can be used without compromising crown margin accuracy.
- 48. • In a study conducted in our department under Prof N.P.PATIL - the critical evaluation of dimensional behaviour of 3 different die materials was evaluated • The die materials studied were Type IV Gypsum, Type IV synthetic Gypsum and epoxy resin • The impression material used was poly vinyl silicon • A total of 90 dies were fabricated from 3 different die materials and 3 different combination impression techniques were used
- 49. • The conclusion drawn was 1. All the dies obtained differed in interabutment distance at the occlusal level 2. All the dies showed decrease in bucco lingual width 3. All the dies showed decrease in height of molar and premolar abutments 4. Epoxy dies were undersized and are acceptable alternatives to gypsum when PVS is the impression material 5. Putty and light body impression using stock trays are more reliable when compared with impressions made using custom acrylic trays
- 50. Comparison • If a release agent is not needed on the surface of the impression ,epoxy dies reproduce detail the best(10µm) • Followed by silver plated dies (30µm) • Then the stone dies (170µm) • However a polysulphide impression requires the use of a release agent with epoxy dies and their reproduction of detail is comparable to that of the stone die • Silver plated dies have superior resistance to abrasion , epoxy dies have good resistance and stone dies have the least
- 53. CONCLUSION • All factors considered the high strength stones (Type IV and V) appear to be the most successful die materials available, with care , abrasion during carving of the wax pattern can be avoided . In case of metal ceramic restoration gypsum dies can be damaged and a resin or metal die can be prepared.
- 54. REFRENCES • Craig Restorative dental materials sixth edition Mosby • Philips (1992) Science of dental materials 9th edition W.B Saunders • Rosensteil (2001) Contemporary Fixed Prosthodontics 3rd edition Mosby • Shillenberg (1981) Fundamentals of fixed prosthodontics 2nd edition Quintessence • Silver plated dies marginal accuracy of cast restorations J Prosth Dent 51;1984: 768-772 • Comparision of surface detail reproduction of flexible die materials J Prosth Dent 1998; 80:485-9 • An investigation of epoxy resin dies J Prosth Dent 1980;44:45-9 • The accuracy of stone dies made from rubber impression materials J Prosth Dent 1970;24:377-85
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