AMALGAMS DENTMAT F1 PPT
Page 1: Introduction
Title: Materials and Processes for Cutting, Grinding, Finishing, and Polishing
Author: Zanyar Mohammed Kareem B. D. S., M. Sc
Page 2: Content Overview
Major Topics Covered:
A Brief History
Applications of Abrasives in Dentistry
Abrasive Instrument Design
Benefits of Finishing and Polishing
Principles of Cutting, Grinding, Finishing, and Polishing
Biological Hazards
Abrasion and Erosion
Finishing and Polishing Procedures
Dentifrices
Page 3: A Brief History of Abrasives
Historical Development:
Over 10,000 years ago: Early instruments shaped by chipping and abrading.
4,000 years ago: Primitive grinding wheels created from cylindrical stones.
13th Century: Introduction of coated abrasives by the Chinese (seashell fragments in gums).
Early 1900s: Advancements in abrasive technology (alumina, diamond particles, silicon carbide).
Page 4: Advances in Restoration Dentistry
Significant improvements in:
Dental handpieces
Air or abrasive technology
Methods for bonding abrasives to binders
Impact: Enhanced quality of restorative treatments in contemporary practice.
Page 5: Applications of Abrasives in Dentistry
Definition of Abrasives: Sharp, hard substances used for grinding or polishing softer materials.
Requirements for Smooth Surfaces:
Essential procedures for contouring every restoration through grinding, finishing, and polishing.
Types of Materials Used:
Ceramics, Metals, and Resin-Based Composites.
Specific Abrasives:
Silicon carbide discs for metal cutting.
Diamond burs for zirconia framework finishing.
Page 6: Forms of Polishing Instruments
Impact on Material Removal:
Sof-Lex discs available in four abrasiveness grades (coarse to superfine).
Astropol system designations: Finish (F), Polish (P), High-Gloss Polish (HP).
Page 7: Functions of Dental Abrasives
Uses include:
Tooth cleaning, occlusal adjustments, contouring surfaces, finishing, debris removal, fine polishing.
Forms of Abrasives:
Powders, pastes, diamond burs, abrasive stones, discs, wheels, points, and cups.
Page 8: Hardness of Abrasives
Hardness Measurement:
Resistance of material to deformation via scratching.
Abrasives must maintain hardness to effectively remove substrate material.
Historical Ranking:
Mohs hardness scale established in 1820.
Use of Knoop and Vickers tests for quantifying hardness.
Comparison of Materials:
Silicon carbide, and diamond abrasives are more effective than garnet on dental porcelain.
Page 9: Abrasive Instrument Design
Production of Abrasive Grits:
Derived from crushed materials sorted by particle size using mesh screens.
Classifications: coarse, medium coarse, medium, fine, superfine.
Page 10: Particle Sizes and Grit Classification
Table detailing average particle sizes and grades for various abrasives, including Aluminum Oxide and Diamond Burs:
Coarse (120um) to Superfine (2000um).
Variability among manufacturers noted.
Page 11: Bonded Abrasives
Definition: Consist of abrasive particles bound together to form grinding tools.
Methods of Bonding:
Sintering
Vitreous bonding
Resinous bonding
Rubber bonding
Page 12: Preparation of Bonded Abrasive Instruments
Procedures before use:
Truing: Aligns abrasive instruments with precision.
Dressing: Adjusts instrument size and shapes, clears debris (clogging).
Clumping referred to as abrasive blinding.
Page 15: Coated Abrasive Discs and Strips
Composition: Abrasive particles on a flexible backing material.
Advantages: Use of moisture-resistant backings enhances durability during use.
Page 17: Nonbonded Abrasives
Definition: Polishing pastes with abrasive particles in a water-soluble medium.
Common Materials: Aluminum oxide and synthetic diamond.
Page 18: Types of Abrasive Motion
Classification:
Rotary instruments: Burs
Planar instruments: Discs
Reciprocating instruments: Handpieces allowing for directional versatility.
Page 19: Types of Abrasives
Common Materials:
Aluminum Oxide: Used for various applications.
Arkansas Stone: Used for fine grinding.
Chalk: Mild abrasive for polishing.
Cuttle: Delicate polishing of metal margins.
Natural & Synthetic Diamonds: Superabrasives.
Page 21: Benefits of Finishing and Polishing
Goals:
Achieve desired anatomy, aid in gingival health, enhance chewing efficiency, improve esthetics, and durability.
Sensitivity to Surface Roughness:
Patients can detect changes as small as 1 um.
Proper polishing reduces tarnish and wear on dental restorations.
Page 23: Principles of Cutting, Grinding, Finishing, and Polishing
Mechanism: Removal of particles through frictional contact with harder materials.
Operations: Cut or grind surfaces producing distinct patterns.
Page 24: Grinding Operations
Mechanics of Grinding:
Removal of small particles using bonded or coated instruments.
Randomly arranged particles deliver various surface patterns.
Page 25: High-Speed Burs
Types of Burs:
16-fluted burs for smooth finishes vs. 8-fluted for rapid material removal.
Page 27: Diamond Burs
Performance Characteristics:
Coarser burs remove material faster but provide rougher surfaces.
Uses for specific applications include grinding through materials efficiently.
Page 28: Bulk-Reduction Process
Definition: Removal of excess material (tooth or restoration) for anatomical form using various burs and abrasive wheels.
Page 30: Contouring Process
Producing anatomical form by precisely removing excess material through finer instruments.
Page 31: Finishing Process
Removal of surface defects post-contouring requires multiple steps for smoothness.
Page 32: Polishing Process
Purpose: To provide gloss, depend on abrasive size and methods of abrasion.
Avoid skipping any steps between finishing and polishing stages to ensure quality.
Page 34: Heat Management
Important during processes to prevent tissue damage;
Use cooling agents like air-water sprays.
Page 35: Biological Hazards
Risks from aerosol dispersal during procedures.
Concerns: Long-term health effects like silicosis.
Page 36: Aerosol Control
Strategies include source control, personal protective equipment (PPE), and adequate facility ventilation.
Page 37: Abrasion Types
Two-Body Wear: Abrasive bonded directly to instrument.
Three-Body Wear: Free particles between two surfaces.
Page 41: Erosion
Caused by impacting particles, typically seen in sandblasting processes.
Page 42: Finishing and Polishing of Resin-Based Composites
Challenges due to soft resin matrix and hard fillers.
Recommended steps for post-curing finishing and polishing.
Page 53: Summary
Effective finishing and polishing for restoration play a significant role in clinical outcomes.
Important to choose appropriate abrasive systems.
Regular surface rinsing to prevent debris interference.