rpd alloys ppt

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Unless otherwise noted, the content of this course material is licensed under a Creative Commons Attribution 3.0 License. Copyright 2008, Dr. Stephen Bayne. The following information is intended to inform and educate and is not a tool for self-diagnosis or a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional. You should speak to your physician or make an appointment to be seen if you have questions or concerns about this information or your medical condition. You assume all responsibility for use and potential liability associated with any use of the material. Material contains copyrighted content, used in accordance with U.S. law. Copyright holders of content included in this material should contact [email protected] with any questions, corrections, or clarifications regarding the use of content. The Regents of the University of Michigan do not license the use of third party content posted to this site unless such a license is specifically granted in connection with particular content objects. Users of content are responsible for their compliance with applicable law. See http://www.dent.umich.edu/license/ for more information. Mention of specific products in this recording solely represents the opinion of the speaker and does not represent an endorsement by the University of Michigan. Viewer discretion advised: Material may contain medical images that may be disturbing to some viewers.

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Page 1: Rpd Alloys Ppt

Unless otherwise noted, the content of this course material is licensed under a Creative Commons Attribution 3.0 License.

Copyright 2008, Dr. Stephen Bayne.

The following information is intended to inform and educate and is not a tool for self-diagnosis or a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional. You should speak to your physician or make an appointment to be seen if you have questions or concerns about this information or your medical condition. You assume all responsibility for use and potential liability associated with any use of the material. Material contains copyrighted content, used in accordance with U.S. law. Copyright holders of content included in this material should contact [email protected] with any questions, corrections, or clarifications regarding the use of content. The Regents of the University of Michigan do not license the use of third party content posted to this site unless such a license is specifically granted in connection with particular content objects. Users of content are responsible for their compliance with applicable law. See http://www.dent.umich.edu/license/ for more information.

Mention of specific products in this recording solely represents the opinion of the speaker and does not represent an endorsement by the University of Michigan.

Viewer discretion advised: Material may contain medical images that may be disturbing to some viewers.

Page 2: Rpd Alloys Ppt

Stephen C. BayneStephen C. BayneUniversity of MichiganSchool of DentistryAnn Arbor, [email protected]

RPDRPDCASTING ALLOYSCASTING ALLOYS

Page 3: Rpd Alloys Ppt

HISTORICAL BACKGROUNDHISTORICAL BACKGROUND1.1. Cr-alloysCr-alloys used in dentistry since 1930s -- widely used since 1970s used in dentistry since 1930s -- widely used since 1970s2.2. Corrosion resistance; high strength and E; low density; low $$$Corrosion resistance; high strength and E; low density; low $$$3.3. Compositions similar to ones for C&B, MF, and orthopedic implants Compositions similar to ones for C&B, MF, and orthopedic implants

RPD ALLOYS CLASSIFICATION1.1. Classification by RPD components:Classification by RPD components:

a.a. Frameworks (major and minor connectors)Frameworks (major and minor connectors)b.b. Clasps; Wrought retention wiresClasps; Wrought retention wiresc.c. RestsRestsd.d. SoldersSolders

2.2. Framework casting alloys:Framework casting alloys:a.a. (Gold Alloys, Type IV)(Gold Alloys, Type IV)b.b. Co-CrCo-Cr Vitallium (60Co-31.5Cr-6Mo)Vitallium (60Co-31.5Cr-6Mo); Nobillium; Nobilliumc.c. Co-Cr-Ni Co-Cr-Ni d.d. Ni-CrNi-Cr (and Ni-Cr-Be) (and Ni-Cr-Be) Ticoncium (74Ni-15Cr)Ticoncium (74Ni-15Cr); Howmedica II; Howmedica IIe.e. (Fe-Cr)(Fe-Cr) Dentillium P-DDentillium P-Dg.g. (Ti-6Al-4V) (cp-Ti)(Ti-6Al-4V) (cp-Ti)h.h. (Ni-Ti)(Ni-Ti)

Page 4: Rpd Alloys Ppt

RPD ALLOYRPD ALLOY PROPERTIESPROPERTIES

1.1. Physical PropertiesPhysical Properties::a.a. Typical fusion temperatures = 1400 to 1454 Typical fusion temperatures = 1400 to 1454 CCb.b. Color = lustrous silvery whiteColor = lustrous silvery whitec.c. Density (lighter weight than gold counterparts) = typically 8-9 gm/cm3Density (lighter weight than gold counterparts) = typically 8-9 gm/cm3d.d. Linear casting shrinkage = 2.05 to 2.33% (vs 1.4 to 1.7% for gold alloys)Linear casting shrinkage = 2.05 to 2.33% (vs 1.4 to 1.7% for gold alloys)e.e. Thermal conductivity = highThermal conductivity = high

2.2. Chemical PropertiesChemical Properties::a.a. Electrochemical corrosion = good passivation by CrElectrochemical corrosion = good passivation by Cr22OO33 if Ni-Cr-Co >85% if Ni-Cr-Co >85%b.b. Passive film attacked vigorously by chlorine -- do not use household bleachPassive film attacked vigorously by chlorine -- do not use household bleach

Image source: Steve Bayne, University of Michigan, 2008

Page 5: Rpd Alloys Ppt

3.3. Mechanical PropertiesMechanical Properties::a.a. E = 200-240 GPa (about 2X that of comparable cast dental gold) E = 200-240 GPa (about 2X that of comparable cast dental gold) b.b. Hardness (typically 30% harder than Type IV golds) = R30N (or VHN) = 370;Hardness (typically 30% harder than Type IV golds) = R30N (or VHN) = 370;

YS = 414-621 MPa, YS = 414-621 MPa, c.c. UTS = 621-828 MPaUTS = 621-828 MPad.d. % Elongation (Cr alloys are quite brittle) = 1-2%% Elongation (Cr alloys are quite brittle) = 1-2%e.e. Co-Cr alloys not affected by HT; Ni-Cr alloys can be affected by high temp HTCo-Cr alloys not affected by HT; Ni-Cr alloys can be affected by high temp HT

Co-Crx

STRAIN

ST

RE

SS

x Ni-Cr

x Au Alloy

RPD ALLOYRPD ALLOY PROPERTIESPROPERTIES

Moduli

Rigidity:(1) geometry of component(2) thickness(3) modulus

Image and graph source: Steve Bayne, University of Michigan, 2008

Page 6: Rpd Alloys Ppt

ClaspStrain

FatigueResistance

Log CYCLES

ST

RE

SS

Co-Cr

x

STRAIN

x

x

ST

RE

SS

Ni-Cr

Au Alloy

Moduli

3.3. Mechanical PropertiesMechanical Properties: (continued): (continued)…………f.f. Fatigue much more important for clasps than connectorsFatigue much more important for clasps than connectors

RPD ALLOYRPD ALLOY PROPERTIESPROPERTIES

Graph source: Steve Bayne, University of Michigan, 2008

Page 7: Rpd Alloys Ppt

4.4. Laboratory ManipulationLaboratory Manipulation::a.a. InvestmentInvestment (requires high temperature investments) = PBI or SBI (requires high temperature investments) = PBI or SBIb.b. SpruingSpruing (entrapped gases may produce voids) = careful venting (entrapped gases may produce voids) = careful ventingc.c. Melting methodsMelting methods = oxyacetylene, oxygen-gas, or electric induction = oxyacetylene, oxygen-gas, or electric inductiond.d. CastingCasting (broken-arm casting machines not recommended) = (broken-arm casting machines not recommended) =

use vacuum and/or pressure castinguse vacuum and/or pressure castinge.e. Sprue removal and finishing/polishing = special lab equipment due to high HSprue removal and finishing/polishing = special lab equipment due to high Hf.f. SolderingSoldering = use care in fluxing, soldering, and = use care in fluxing, soldering, and

heat control (electric soldering)heat control (electric soldering)g.g. Solders = usually >800 fine Ag-solders (good corrosion resistance)Solders = usually >800 fine Ag-solders (good corrosion resistance)f.f. SterilizationSterilization = dilute bleach solutions = dilute bleach solutions

5.5. Clinical propertiesClinical properties::a.a. AdjustmentsAdjustments (casts, etc.) = difficult due to high hardness and E (casts, etc.) = difficult due to high hardness and Eb.b. Ni sensitivity = sometimes but probably due to misfit or improper designNi sensitivity = sometimes but probably due to misfit or improper designc.c. Wear = low (but may contribute to excessive wear of teeth or restorations)Wear = low (but may contribute to excessive wear of teeth or restorations)d.d. HygieneHygiene = clean with soap and water or very dilute solutions = clean with soap and water or very dilute solutions

avoiding chlorine (Use stiff bristle brush; Avoid abrasive dentifrices)avoiding chlorine (Use stiff bristle brush; Avoid abrasive dentifrices)

RPD ALLOYRPD ALLOY PROPERTIESPROPERTIES

Page 8: Rpd Alloys Ppt

Alloy TypeAlloy Type YieldYieldStrengthStrength(MPa)(MPa)

TensileTensileStrength Strength (MPa)(MPa)

Percent (%)Percent (%)ElongationElongation

HardnessHardness(VHN)(VHN)

ModulusModulus(GPa)(GPa)

ADA Spec #14, Min 500 ----- 1.5 ----- 172

Type IV Gold AlloyType IV Gold Alloy 493493 776776 7.7. 264264 9090

Fe-CrFe-Cr 703703 841841 9.9. 309309 202202

Co-Cr-NiCo-Cr-Ni 470470 685685 8.8. 264264 198198

Co-CrCo-Cr 710710 870870 1.61.6 432432 224224

Ni-CrNi-Cr 690690 800800 3.83.8 300300 182182

Ti-6Al-4VTi-6Al-4V ---------- 930930 5.5. 320320 117117

Others (cp-Ti, Ni-Ti)Others (cp-Ti, Ni-Ti)

COMPARISON OF ALLOYCOMPARISON OF ALLOYMECHANICAL PROPERTIESMECHANICAL PROPERTIES

Page 9: Rpd Alloys Ppt

BIOMECHANICAL ANALYSISBIOMECHANICAL ANALYSISClinical Lifetime of RPDs (5-8 years)Clinical Lifetime of RPDs (5-8 years)

RPD must resist 4 degrees of freedom = x, y, z, rotationRPD must resist 4 degrees of freedom = x, y, z, rotation

General categories of failure:General categories of failure:(1)(1) Biologic = bone resorption; tooth mobility; tissue irritationBiologic = bone resorption; tooth mobility; tissue irritation(2) (2) Physiologic = PDL overload; toth wearPhysiologic = PDL overload; toth wear(3)(3) Materials = materials defects; lab problems; adjustmentsMaterials = materials defects; lab problems; adjustments

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Image source: Steve Bayne, University of Michigan, 2008

Page 10: Rpd Alloys Ppt