Cast restorations

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

1. CAST RESTORATIONS- INTRODUCTION Deepthi P.R. 2 nd Year MDS Dept. of Conservative Dentistry & Endodontics

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

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 M any 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. 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. 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. 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. 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. 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. 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. Abutment teeth: accommodate the retainers for denture Better accommodation of forces Rest seats, guiding planes better controlled with indirect technique Partial & C omplete dentures- Removable & Fixed Color Atlas of Clinical Operative Dentistry

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. 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. Existing cast restorations Dissimilar metals

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. Properly finished and polished cast alloys: most compatible with periodontium Most practical for subgingival lesions Partially subgingival restorations

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. Strength Biocompatibility: Allergic patients Precise detail Corrosion resistance Instantaneous : casting procedure Maximum biological acceptance ADVANTAGES

18. Low wear: Castings withstand occlusal loads with minimal changes Control of contours and contacts: Indirect technique- large & complex restoration

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 N o layering effect Less internal defects Fairly even stress patterns of entire structure ADVANTAGES

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. Biological acceptance: Finished, polished, glazed outside the oral cavity No risk of heat & pressure to the P-D organ ADVANTAGES

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. Several interphases Extensive tooth preparation: hazardous to vital tissues Galvanic deterioration Abrasion differential DISADVANTAGES

24. Several interphases: Tooth- cement- casting junction: leakage Number of reproductions with different materials Microscopically ill fitting restoration Leakage pronounced gingivally DISADVANTAGES

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. 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. 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. Use Major elements Nobility Three principal elements Dominant phase system Revised classification by ADA in 2003 CAST DENTAL ALLOYS- Classification

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. 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. 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. 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. 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. 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. Au: Deformability, strength, hardness, characteristic yellow color & density – 19.3 g/cm 3 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. 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. “ 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. Mainly of Pd & Ag with In, Cu, Sn , Zn not >10% Pd : White color& density – 11g/cm 3, strength, hardness, plasticity & nobility Ag: Substitutional alloys with Pd ; more plastic, less strength & nobility with increased Ag CLASS III ALLOYS

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. Additions to the basic Ni-Cr combination Cr not >30% Both: Passivity, strength, density (8g/cm 3 ) , 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. Si & Fe: Increase the strength; not >2% C 2- : 0.2 to 0.4% - strengthening of alloy Complex carbides: Ni & Cr- MC, M 6 C, M 23 C 6 B: Reducing the solubility Of C & stabilizing carbides B & Si: Deoxidisers & flowing agents- improve castability CLASS IV ALLOYS

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. 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. 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. 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. Composite material with 4 components Solid ceramic body with crystalline material: Thermal processing

47. Spinel & other crystals & glasses: allotropic & dimensional changes Shrinkage compensate for expansion eliminating the need for investment shrinkage/ expansion Thermal processing

48. 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

49. Comparison of physical & mechanical properties

50. Class I: 15-16 gm /cm 3 Class II: 11-12 gm /cm 3 Class III: 10-11 gm /cm 3 Class IV: 8 gm /cm 3 Class V: 2.7 gm /cm 3 Lower density: more force in centrifugal casting machine; but more restorations per unit weight Density

51. 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

52. Cast ceramics : Transmitted / induced heat used Range of melting & firing temperatures Thermoplastic: casting Fusing: completion of thermal processing

53. 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

54. 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

55. 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

56. Class V: A bsolutely 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

57. 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

58. 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

59. 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

60. 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

61. 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

62. Class I & II : Au solders- predictable & without much failures Class III : Ag solders Reducing zone of the flame Solder melting temperature: 150 0c lower than mother alloy Proper timing & atmosphere Soldering

63. Class IV: Inert environment: Oven soldering S pecific 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

64. 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

65. 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

66. 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

67. 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

68. 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

69. 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

70. 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

71. References Marzouk MA, Simonton AL, Gross RD. Operative Dentistry- Modern Theory & Practice, 1 st Edition Roberson TM, Heymann HO, Swift EJ. Sturdevant’s Art & Science of Operative Dentistry, 5 th Edition Anusavice , Shen , Rawls. Phillips’ Science of Dental Materials, 12 th Edition Summit JB, Robbins JW, Schwartz RS. Fundamentals of Operative Dentistry. A Contemporary Approach. 2 nd edition Schluein TM. Significant events in the history of Operative dentistry. Journal of History of Dentistry. Vol 53. No 2.2005.63-72

72. Thank you!!