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Cast restorations

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History
Indications
Contraindications
Advantages
Disadvantages
Materials for cast restorations
Mouth preparation prior to cast restorations

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Cast restorations

  1. 1. CAST RESTORATIONS- INTRODUCTION Deepthi P.R. 2nd Year MDS Dept. of Conservative Dentistry & Endodontics
  2. 2.  History  Indications  Contraindications  Advantages  Disadvantages  Materials for cast restorations  Mouth preparation prior to cast restorations CONTENTS
  3. 3.  Metal casting : Lost wax/ “Cire perdue” method  Agiulhon de Saran in 1844: Inlay in investment mold with molten Gold  B.F. Philbrook: simplified version of casting process in 1897  Many techniques: flowing solder into molds for gold inlay fabrication  Porcelain inlays : 1857; later replaced by the cast gold inlays HISTORY www.lost-wax-casting.com
  4. 4.  William Taggart in 1907: Technique of fabrication of gold castings  Paralleling systems: 1890s  Centrifugal casting machine : Jamieson in 1907  1985: first ceramic inlay CAD/CAM
  5. 5.  Extensive tooth involvement  Adjunct to successful periodontal therapy  Correction of occlusion/ Diastema closure  Endodontically treated teeth  Support for and preparatory to partial or complete dentures  Retainers for fixed prostheses INDICATIONS
  6. 6.  Partially subgingival restorations  Low incidences of plaque accumulation or decay  Functionally sound stomatognathic system with complete freedom of the mandible to move without any premature contacts  Cracked teeth  Esthetics  Dissimilar metals INDICATIONS
  7. 7.  Efficiently replace lost tooth structure  Support remaining tooth structure  Higher strength & superior control of contacts and contours  Cast metal onlay: withstand & distribute occlusal loads  Amalgam: foundation Extensive tooth involvement
  8. 8.  Contacts & contours, marginal ridges, embrasures: physiologically restored & permanently maintained  Splinting of periodontally weakened teeth by cast restorations  Preserve intact facial and lingual enamel/ cementum Adjunct to successful periodontal therapy Dental Update 2000;27:278-285 Linked crowns Gold copings for telescopic crowns
  9. 9. Endodontically treated teeth  Reinforcement of the clinical crown portion  Onlay : distribute occlusal loads to reduce chances of tooth fracture  Changes in occlusal table or occlusal parts of a tooth  Inlay/ onlay for extension of mesiodistal dimension  Slightly tilted teeth Correction of occlusion
  10. 10.  Abutment teeth: accommodate the retainers for denture  Better accommodation of forces  Rest seats, guiding planes better controlled with indirect technique Partial & Complete dentures- Removable & Fixed Color Atlas of Clinical Operative Dentistry
  11. 11. Functionally sound stomatognathic system  Free of any pathology  Pathology: diagnosed and treated  If not expected to be corrected by cast restorations- correction prior to restoration  Tooth – cement- cast restoration complex: break down avoided  Rigid control of plaque accumulation Low incidence of plaque accumulation/ decay
  12. 12.  Cracks: cleavage planes for possible future fracture  Cast onlays with skirting & crowns: braces tooth against fracture injury  Restoration & splinting of cracked, separated segments of teeth  Healing of some cracks Cracked teeth
  13. 13. Existing cast restorations Dissimilar metals •Galvanism •Premature abrasion •Anodic dissolution of metals •Mechanical failure of restorations
  14. 14.  Approximating dissimilar metal: diffusion of restorative materials to the cast alloy  Vacancy porosities in the material  Alloying of the cast alloy – weaken them
  15. 15.  Properly finished and polished cast alloys: most compatible with periodontium  Most practical for subgingival lesions Partially subgingival restorations
  16. 16.  Large pulp chambers & incompletely mineralized dentin  Developing and deciduous teeth: Growth / Resorption affected by traumatic nature of the procedure  High plaque/ caries indices: Recurrent decay & acceleration of periodontal deterioration  Occlusal disharmony  Dissimilar metals CONTRAINDICATIONS
  17. 17.  Strength  Biocompatibility: Allergic patients  Precise detail  Corrosion resistance  Instantaneous : casting procedure  Maximum biological acceptance ADVANTAGES
  18. 18.  Low wear: Castings withstand occlusal loads with minimal changes  Control of contours and contacts: Indirect technique- large & complex restoration
  19. 19. Strength:  Yield, Compressive, Tensile & Shear strengths: greater  Replace areas of stress concentration & reinforce weakened tooth structure  Material imparts resistance to the tooth Instantaneous building:  Fewer voids  No layering effect  Less internal defects  Fairly even stress patterns of entire structure ADVANTAGES
  20. 20. Reproduction:  Precise form & minute detail maintained  Details maintained under functional stresses Corrosion Resistance:  Noble/ passivated metal  Not affected by oral environment  Cast ceramics: completely inert  Improved longevity, esthetics & biologic qualities ADVANTAGES
  21. 21. Biological acceptance:  Finished, polished, glazed outside the oral cavity  No risk of heat & pressure to the P-D organ ADVANTAGES
  22. 22.  Number of appointments & higher chair time: Two appointments & more time than direct restoration  Temporary: Loosen or break occasionally  Cost: Material costs, laboratory bills & time involved  Technique sensitive: Error in multistep process – suboptimal fit  Splitting forces: Small inlays- wedging effect DISADVANTAGES
  23. 23.  Several interphases  Extensive tooth preparation: hazardous to vital tissues  Galvanic deterioration  Abrasion differential DISADVANTAGES
  24. 24. Several interphases:  Tooth- cement- casting junction: leakage  Number of reproductions with different materials  Microscopically ill fitting restoration  Leakage pronounced gingivally DISADVANTAGES
  25. 25. Galvanic deterioration:  Cathodic nature of alloys to other metals  Rapid deterioration of amalgam & failure  Cast alloy contamination by free mercury  Undesirable effects: vital tissues DISADVANTAGES
  26. 26. Abrasion Potential:  Alloys & ceramics: high abrasive resistance than enamel  Teeth abraded more easily: abrasion differential  Imbalance in occlusion: teeth shifting, tilting or rotating  Occlusal interferences  Periodic occlusal equilibriation needed DISADVANTAGES www.cdeworld.com
  27. 27.  ADA#5: 75% Au & Pt based alloys  Other castable materials available MATERIALS USED FOR CAST RESTORATIONS Types I, II , III, IV Gold alloys Low gold alloys: Au <50% Non gold Pd based alloys Ni- Cr based alloys Castable moldabe ceramics
  28. 28.  Use  Major elements  Nobility  Three principal elements  Dominant phase system  Revised classification by ADA in 2003 CAST DENTAL ALLOYS- Classification
  29. 29. Classification Use  All- metal inlays  Crowns & bridges  Metal- ceramic prostheses  Posts & cores  Removable partial dentures  Implants Major elements  Au based  Pd based  Ag based  Ni based  Co based  Ti based
  30. 30. Classification Three principal elements  Au-Pd-Ag  Pd-Ag-Sn  Ni-Cr-Be  Co-Cr-Mo  Ti-Al-V  Fe-Ni-Cr Nobility  High- noble  Noble  Predominantly base metal Dominant phase system  Single phase  Eutectic  Peritectic  Intermetallic
  31. 31. Revised classification ADA-2003  High Noble (HN)  Ti & Ti alloys  Noble (N)  Predominantly base metal (PB)  High Noble (HN)  Noble (N)  Titanium (TI)  Predominantly base alloys (PB)  Cobalt- base alloys (cobalt base PB) IdentAlloy system
  32. 32.  Baseline of casting alloys  70-75% Au or Pt group substitutes: Pt, Pd, Rh, Os, Ir, Ru  25-30% : Ag & Cu (hardening)  Traces : Zn &/or In  4 types COMPOSITION & EFFECTS- CLASS I ALLOYS www.umiyadentalcare.blogspot.com
  33. 33.  Type I: most plastic & highest gold content  Type IV: least deformable & the lowest content of gold  Single tooth restoration: Type III/ II  Properties: % composition, alloying nature & environment of fabricating & casting
  34. 34.  Au: Alloy in different fashions with each metal  Pd & Pt: Disordered alloying with Au & several ordered alloys with Cu  Ag: Substitutional & ordered alloying with Au ; readily alloy with copper- ordered to eutectic alloys & solid solution with Pd  Cu: Solid solution with Au, Pd, Pt & Ag  Zn, In: Alloy with gold
  35. 35.  Au: Deformability, strength, hardness, characteristic yellow color & density – 19.3 g/cm3  Pt, Pd: Rigidity, nobility, strength, hardness & whitening of the alloy  Ag: Mimics Au in deformability effect, but adversely affects nobility. Precipitated Ag-Au intermetallic compound: hardening process  Cu: Increases hardness & strength, decreases the nobility Effects on Properties
  36. 36.  Zn: Essential deoxidizer during casting & replaced if the alloy is to be recast  In: refines the grains of the final alloy; scavenger for the alloy during the casting procedure
  37. 37.  “ Economy gold alloys”  Gold content much lower than Class I  Pd: gold substitute  60% Pd & 5% Au; Cu, Ag, Zn: 25-30%  Au: same properties but limited  Pd: most desirable physical properties  Cu: reacts with Pd- strengthening-hardening-brittling effect  Ag: continuous substitutional solid solution alloy with Pd CLASS II ALLOYS
  38. 38.  Mainly of Pd & Ag with In, Cu, Sn, Zn not >10%  Pd: White color& density – 11g/cm3, strength, hardness, plasticity & nobility  Ag: Substitutional alloys with Pd ; more plastic, less strength & nobility with increased Ag CLASS III ALLOYS
  39. 39.  Cu: Reacts with Pd & Au; lowers fusing temperature & increased resistance to tarnish & corrosion  Zn: Deoxidizer  In: Scavenger during melting , to increase resistance to tarnish & corrosion
  40. 40.  Additions to the basic Ni-Cr combination  Cr not >30%  Both: Passivity, strength, density (8g/cm3 ) , plasticity, hardness & color  W, Mo, Al: increase strength & hardness- ppt intermetallic compounds with Cr & Ni  Be: lower the fusion temperature & improve castability- hazards. Ga- substitute CLASS IV ALLOYS
  41. 41.  Si & Fe: Increase the strength; not >2%  C 2- : 0.2 to 0.4% - strengthening of alloy  Complex carbides: Ni & Cr- MC, M6 C, M23 C6  B: Reducing the solubility Of C & stabilizing carbides  B & Si: Deoxidisers & flowing agents- improve castability CLASS IV ALLOYS
  42. 42.  Properties: techniques used in fabrication; carbides incorporated in different stages of casting  Nb: Open air melting of the alloys  Sn & rare earth elements : Control oxidation of alloy during porcelain firing  Ti & Co: strength
  43. 43.  Complex ceramic monolithic structure: 70-90% crystalline material- Mg aluminate spinel & Alumina  Al2O3 (50%) : MgO (15%) in 7:1 ratio  5-25% glass frit compounded to react with silica- Silicate glasses  Si polymer: workable mass  0.5% stearate/ wax- lubricant CLASS V ALLOYS
  44. 44.  Heated to & above the GTT of polymer binder: 30° to 150 °- plastic, deformable & moldable into Gypsum mold space  Cooling to room temperature: restores the rigidity  Thermal treatment: 10-18 hours- alumina reacts with magnesia forming Mg aluminate spinel – MgAl2O4- expansion
  45. 45.  Cations from glass frit & Al2O3- Ionic bonding: metal silicate glasses  Si polymer: R ---O---Si—O—Si-- R  60% SiO group- change to SiO4 with classical tetrahedron unit cells
  46. 46. Composite material with 4 components Solid ceramic body with crystalline material: Thermal processing Al2O3 Mg Al2O4 AlSiO4
  47. 47.  Spinel & other crystals & glasses: allotropic & dimensional changes  Shrinkage compensate for expansion eliminating the need for investment shrinkage/ expansion Thermal processing
  48. 48. 5000c @ 160/hr * 16 hrsRoom temperature 6500c8 hrs* 6000c in 1 hr 13500c stop 13500c @ 420/hr
  49. 49. PHYSICAL & MECHANICAL PROPERTIES  Density  Range of melting & firing temperatures  Ultimate strength  Modulus of elasticity  Elongation & yield strength  Hardness  Tarnish & corrosion  Castability- moldability  Finishing & polishing  Soldering
  50. 50. Comparison of physical & mechanical properties
  51. 51.  Class I: 15-16 gm/cm3  Class II: 11-12 gm/cm3  Class III: 10-11 gm/cm3  Class IV: 8 gm/cm3  Class V: 2.7 gm/cm3  Lower density: more force in centrifugal casting machine; but more restorations per unit weight Density
  52. 52.  Class IV- Highest melting range  Class I- Lowest  Class I & II: Regular gas-air fuel, calcium sulfate dihydrate bonded investments, low heat technique  Class IV & Class III: phosphate & silicate bonded investments, acetylene-oxygen, gas-oxygen, electric resistance or induction melting  Casting environment – carefully controlled for III & IV Range of melting & firing temperatures
  53. 53. Cast ceramics : Transmitted / induced heat used Range of melting & firing temperatures Thermoplastic: casting Fusing: completion of thermal processing
  54. 54.  Mechanical failure: rare  Metallic alloys- far superior to cast ceramics: Tensile & Shear- ductile/ plastic failure  Ceramics: Stronger under compression- Brittle fracture  Tensile strength s from Class I to IV Ultimate strength
  55. 55. Modulus of elasticity  Class V materials : 6 times as rigid as Class I  Factor in abrasion resistance  All materials: exceed enamel’s  Maximum: class V  High abrasive resistance Hardness
  56. 56.  Measures of forces needed to achieve deformability/ burnishability  Class I alloys: least yield strength & greatest elongation- highest deformability under the least amount of forces  Class IV alloys: needs special equipment for designing  Class V: Zero elongation & yield strength coinciding with brittle fracture Elongation & Yield strength
  57. 57.  Class V: Absolutely chemically inert  Class I: Nobility  Class IV: Passivity  Class III:  least resistant to corrosion  greater Ag content: especially in sulfurous environment  Class II: low Au content- surface &marginal deterioration Tarnish & Corrosion
  58. 58.  Class II & III alloys: contraindicated – high sulfur diets and areas of stagnation of plaque & food substrates  Alloy with highest Pd content in Class II & III chosen- questionable cases Tarnish & Corrosion
  59. 59.  Class III & IV alloys: rough surface of castings  Pd: H2 & Ag: O2  Incorporated & released during solidification- porosities & rough surface  Class II, III, IV: closed furnaces & electric conduction melting  Class I: Maximum density & good surface detail  Overcome the gas pressure within the mold Castability-moldability
  60. 60.  Metallic alloys: solidification shrinkage- investment expansion  Class IV alloys except the Be containing ones: reproduce least details  Modifications in cavity & tooth preps. Needed Castability-moldability
  61. 61.  Reproduction of wax pattern: single process with alloys & in two stages with ceramics- one done on the die  High density: ceramic can wet all the details of the mold & reproduce the pattern  No shrinkage- no expansion of investment required
  62. 62.  Class I & II: Easiest among the alloys  Class III: more time & effort required  Class IV: high speed equipment, more abrasive tools, more time compared others  Cast ceramics: finished after retrieval prior to thermal processing ; glazed during & after thermal processing Finishing & Polishing www.ivocarvivadent.com
  63. 63.  Class I & II: Au solders- predictable & without much failures  Class III:  Ag solders  Reducing zone of the flame Solder melting temperature: 1500c lower than mother alloy Proper timing & atmosphere Soldering
  64. 64.  Class IV: Inert environment: Oven soldering Specific solder: each alloy Risks: solder failure & change in composition of mother alloy  Cast ceramics: multiple attached units: cast together  Contact & contour modifications: baking on aluminous porcelain
  65. 65.  Plaque control  Caries control  Control of periodontal problems  Proper foundation  Control of the pulpal condition of the tooth  Occlusal equilibriation  Diagnostic wax-ups & temporary restoration MOUTH PREPARATION PRIOR TO CAST RESTORATIONS
  66. 66. Plaque Control  Cast/ cement/ tooth structure: vulnerability  Plaque control measures  Plaque index < 10%  Rampant uncontrolled carious processes halted  Indirect pulp capping, amalgam/ composite resin restorations  Little or no evidence of recurrent decay Caries Control
  67. 67.  Ideal to start therapy with a sound periodontium, unless it is indicated as part of periodontal therapy & maintenance  Periodontal therapy: under control Control of Periodontal problems Pockets eradicated Bone resorption arrested Defects corrected Exposed roots & crown surfaces free from deposits Gingival tissues healed Apparent clinical crown dimensions stable
  68. 68.  Badly broken down teeth: Substructure/ foundation  Before tooth preparation for cast restoration: the need diagnosed & implemented  Foundation building for tooth after unsuccessful attempt for cast restoration - frustrating Proper Foundation
  69. 69.  Proper preop evaluation of the pulp- dentin- root canal system  Extensive defects/ one or more previous restorations  Irreversible pathological changes: cast restoration procedures  Endodontic therapy- part of mouth preparation Control of pulpal condition of the tooth
  70. 70.  Premature occluding contacts: greater & long standing disturbances in stomatognathic system  No interfering/ premature contacts  Pattern of reliable protective mechanism for mandibular disclusion Occlusal Equilibriation www.dentalaegis.com
  71. 71.  Full arch study models: mounted on semi or fully adjustable articulator  Involved teeth reduced & diagnostic wax-up made in the desired occlusal shape & relationship  Duplicate stone models: temporary & final restorations  Teeth roughly prepared Diagnostic wax-ups & Temporary Restorations
  72. 72. Teeth roughly prepared Restored with temporary restorations Worn by patient & periodically examined Changes made in temporaries Utmost compatibility between stomatognathic system Achieved & verified Cast restorations fabricated Replicas of temporaries Physiologic & therapeutic to stomatognathic system
  73. 73. References  Marzouk MA, Simonton AL, Gross RD. Operative Dentistry- Modern Theory & Practice, 1st Edition  Roberson TM, Heymann HO, Swift EJ. Sturdevant’s Art & Science of Operative Dentistry, 5th Edition  Anusavice, Shen, Rawls. Phillips’ Science of Dental Materials, 12th Edition  Summit JB, Robbins JW, Schwartz RS. Fundamentals of Operative Dentistry. A Contemporary Approach. 2nd edition  Schluein TM. Significant events in the history of Operative dentistry. Journal of History of Dentistry. Vol 53. No 2.2005.63-72
  74. 74. Thank you!!

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