Coconote
AI notes
AI voice & video notes
Export note
Try for free
Dental Ceramics Overview
Jul 3, 2024
Dental Ceramics Basics
Introduction
Presenter
: Dr. Suresh Shenvi
Topic
: Dental Ceramics
Suggested by
: Gagan Yadhav
Difficulty
: Noted as challenging for undergraduates
Evolution of Dental Crowns
Types
:
Metal Crowns
Metal Ceramic Crowns
All Ceramic
Key Objective
: Achieve both strength and aesthetics
Composition and Methods
Ceramics/Porcelain
Used widely in many fields
Dental ceramics have additional components
Silica
Forms of Silica
Crystalline Form
Used in: investment materials, dental cements, composites
Example: Quartz
Advantage: Low melting temperature
Disadvantage: Low strength
Non-Crystalline Form
Used in dental ceramics
Example: Fused Silica
Advantage: High strength
Structure of Silica
Silica Tetrahydrate
Silica ion surrounded by oxygen
Strength from bonds between ions
Challenges with Fused Silica
High Fusion Temperature
: Not feasible for dental labs
Solution
: Adding Glass Modifiers (Carbonates of sodium, potassium, calcium)
Glass Modifiers
Function
: Reduce fusion temperature and viscosity
Limitations
: Can reduce strength and increase susceptibility to oral fluids
Effect
: Leads to devitrification (increased opacity)
Classification of Ceramics by Fusion Temperature
High Fusing
: > 1300°C
Medium Fusing
Low Fusing
Ultra Low Fusing
: < 850°C
Key Considerations
Use low fusing ceramics for high-force areas like bridges
Feldspar
Composition
: Potassium aluminum silicate
Functions
:
Forms a glass phase to allow silica particles to fuse
Undergoes incongruent melting (creates liquid and crystalline lucite)
Components Added to Ceramics
Boric oxide
: Acts as a glass modifier, facilitates silica movement
Pigments
: Provide different shades
Category
: Feldspathic ceramics
Challenges with Feldspathic Ceramics
Strength Issues
Good compressive strength
Low tensile strength (brittle)
SEM Image Observation
Presence of microscopic cracks
Bending forces propagate cracks leading to fractures
Metal-Ceramic Crowns
Benefits
Aesthetics from ceramic layer
Strength from metal core
Disadvantages
Requires more tooth reduction
Lacks translucency (opaque appearance)
Bonding
Chemical bonding: Between metal oxides and ceramic
Essential metals: Iron, indium, tin
Research Advances
Strengthening Techniques
Glazing
Types
: Self-glaze vs. Over-glaze
Preferred
: Self-glaze (longer-lasting)
Residual Compressive Stress
Generated by
: Ion exchange, thermal tempering, thermal expansion coefficient mismatch
Methods
:
Ion Exchange
: Sodium replaced by larger potassium
Thermal Tempering
: Differential cooling rates
Thermal Expansion Coefficient Mismatch
: Different shrink rates in core and surface materials
Interruption of Crack Propagation
Methods
: Dispersion of crystalline phase, transformation toughening
Alumina and Zirconia
: Interrupt crack propagation
Design Modifications
Avoid sharp margins and sudden thickness changes
Zirconia-based Ceramics
Advantages
Strong, allows metal-free crowns
Disadvantages
Opaque nature
High abrasion resistance
Summary
Evolution from metal to aesthetic ceramics
Various modifications to improve ceramic strength
Conclusion
Collaboration for more informative videos
Encouragement for feedback and shares
📄
Full transcript