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

1. CAST RESTORATIONS-
INTRODUCTION
Deepthi P.R.
2nd 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
 Many techniques: flowing solder into molds for gold
inlay fabrication
 Porcelain inlays : 1857; later replaced by the cast gold
inlays
HISTORY
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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 & Complete dentures-
Removable & Fixed
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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
•Galvanism
•Premature abrasion
•Anodic dissolution of metals
•Mechanical failure of
restorations

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
 No 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
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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
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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/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.  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/cm3, 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/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.  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.  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
Al2O3 Mg
Al2O4
AlSiO4

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

48. 5000c @
160/hr
* 16 hrsRoom
temperature
6500c8 hrs*
6000c
in 1 hr
13500c stop
13500c
@
420/hr

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. Comparison of physical & mechanical
properties

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

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. 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.  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.  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.  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.  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.  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.  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.  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
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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.  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.  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. 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.  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.  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.  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.  Premature occluding contacts: greater & long
standing disturbances in stomatognathic system
 No interfering/ premature contacts
 Pattern of reliable protective mechanism for
mandibular disclusion
Occlusal Equilibriation
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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. 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. 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. Thank you!!