introduction to dental metallurgy
DESCRIPTION
Introduction to dental metallurgy. METALS: INTRODUCTION. Metals are one of the mainstays of dentistry They are a group of ‘structural materials’ and are best suited for stress bearing applications. INTRODUCTION. Esthetic restorations are ideal for single tooth restoration - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/1.jpg)
Introduction to dental metallurgy
![Page 2: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/2.jpg)
METALS: INTRODUCTION
• Metals are one of the mainstays of dentistry
• They are a group of ‘structural materials’ and are best suited for stress bearing applications
![Page 3: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/3.jpg)
INTRODUCTION
• Esthetic restorations are ideal for single tooth restoration
• Metals are ideal for more than one tooth replacement FPDs, RPDs
![Page 4: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/4.jpg)
Outline of the lecture
• Cast and wrought metals• Alloys
![Page 5: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/5.jpg)
STRUCTURE OF METAL
• In metals, atoms are tightly packed in a CRYSTAL STRUCTURE (GRAIN)(A regular arrangement of atoms that repeats itself many times)
• The repeating entity is called the UNIT CELL. The unit cell is the basic building block of a metal
• Collection of many crystals in a metal is termed polycrystalline
![Page 6: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/6.jpg)
STRUCTURE OF METAL
![Page 7: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/7.jpg)
STRUCTURE OF METAL
![Page 8: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/8.jpg)
STRUCTURE OF METAL
![Page 9: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/9.jpg)
• The structure of the GB is more non-crystalline
• GB is a higher-energy-region than the interior of the grain
• Impurities in metal may be found in greater concentrations at the GB
• GB is more readily attacked by chemicals
GRAIN BOUNDARIES (GB)
![Page 10: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/10.jpg)
Grains & Grain Boundaries
AK-Y02-04-DM-PP
![Page 11: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/11.jpg)
Solidification of metals
AK-Y02-04-DM-PP
![Page 12: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/12.jpg)
Solidification of metals
AK-Y02-04-DM-PP
![Page 13: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/13.jpg)
Solidification of metals
AK-Y02-04-DM-PP
![Page 14: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/14.jpg)
Mechanical properties of metals
AK-Y02-04-DM-PP
![Page 15: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/15.jpg)
SPACE LATTICE
• Lattice is a 3-dimensional array of points that coincides with the positions of atom in a unit cell
AK-Y02-04-DM-PP
Simple cubic structure
![Page 16: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/16.jpg)
SPACE LATTICE
AK-Y02-04-DM-PP
![Page 17: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/17.jpg)
LATTICE ARRANGEMENTS IN METAL
Different lattice arrangements are seen in different metals
• Body-centered cubic (BCC)• Face-centered cubic (FCC)• Hexagonal close-packed (HCP)
AK-Y02-04-DM-PP
![Page 18: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/18.jpg)
Lattice imperfections
AK-Y02-04-DM-PP
![Page 19: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/19.jpg)
Lattice imperfections
AK-Y02-04-DM-PP
![Page 20: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/20.jpg)
Dislocation and slip plane
AK-Y02-04-DM-PP
Dislocation
![Page 21: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/21.jpg)
SLIP PLANE
AK-Y02-04-DM-PP
![Page 22: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/22.jpg)
Dislocations
• Dislocation is crucial for the plastic, or permanent deformation of a materials
• Without dislocation very high amount of mechanical stress is required for deformation
AK-Y02-04-DM-PP
![Page 23: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/23.jpg)
Dislocations
AK-Y02-04-DM-PP
![Page 24: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/24.jpg)
CAST & WROUGHT METAL
• Cast metal is produced when molten metal is allowed to cool in a mold
• Wrought metal is produced by deforming (process of working) the cast metal
• Wrought alloy exhibits properties and micro-structure that is not associate with the same alloy when cast
![Page 25: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/25.jpg)
WROUGHT METAL
• Stainless steel (orthodontic wires, crowns, clasps, root canal reamers & surgical instruments)
• Cobalt-chromium nickel• Nickel titanium• Commercially pure (CP) titanium
![Page 26: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/26.jpg)
• Hot working (elevated temperature)
• Cold working (plastic deformation at room temp)rolling, drawing, pressing etc. Also called work hardening
WROUGHT METAL: 2 TYPES OF WORKING
![Page 27: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/27.jpg)
AK-Y02-04-DM-PP
![Page 28: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/28.jpg)
WROUGHT METAL
![Page 29: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/29.jpg)
COLD WORKING • Strengthening mechanism
• Cold working increases the physical properties such as yield strength, tensile strength, surface hardness, decreases ductility (% elongation at failure)
• Cold working takes place in metal by the motion of defects through the material (SLIP)
![Page 30: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/30.jpg)
• Compaction of direct filling gold (cohesive gold/ gold foil) is an example for clinical application of work hardening
CLINICAL APPLICATION OF WORK HARDENING
![Page 31: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/31.jpg)
Annealing refers to a heat treatment in which a material is exposed to an elevated temperature for an extended period of time and then slowly cooled (3 stages).
Annealing eliminates or reduces the effects off cold working
It relives stresses, increases ductility and toughness
Heat treatment of metals: ANNEALING
![Page 32: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/32.jpg)
1. Recovery2. Recrystallization3. Grain growth
STAGES IN ANNEALING
![Page 33: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/33.jpg)
The cold worked properties begin to disappear before any significant change is observed microscopically.ª Very little decrease in tensile strengthªVery little change in ductilityª Pronounced change in electrical
conductivity
RECOVERY: (STRESS-RELIEF ANNEAL)
![Page 34: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/34.jpg)
• This occurs when further heat is applied to the cold worked material.
• The previous grains are replaced by new, smaller, stress-free ones (refines grain structure)
• Decreases hardness & tensile strength
• Increases ductility, malleability & corrosion resistance
RECRYSTALLIZATION
![Page 35: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/35.jpg)
• It follows recrystallization when the metal is overheated
• This process causes migration of the grain boundary, whereby large grain replaces many small ones
• Grain growth occurs only in wrought metals
• Mechanical properties are lowered by grain growth
GRAIN GROWTH
![Page 36: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/36.jpg)
Effects of annealing on tensile strength and ductility
![Page 37: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/37.jpg)
Wires should NEVER BE RECRYSTALLIZED, ONLY RECOVERY This is to preserve the fibrous grain structure
PRECAUTION
![Page 38: Introduction to dental metallurgy](https://reader033.vdocuments.net/reader033/viewer/2022061604/56816759550346895ddc1cfa/html5/thumbnails/38.jpg)
SUMMARY-III
Cast metal and Wrought metal
Hot working & Cold working (work hardening)
Annealing
RecoveryRecrystallizationGrain growth