Abrasive agents in dentistry

Dental Abrasives

1. Abrasives Presented By : Arpit Viradiya Guided By : Dr Sandeep Metgud Dr Deepali Agrawal

2. Contents Definition Abrasive action Types of abrasion Principles : Cutting Grinding & Polishing Desirable Characteristics Of An Abrasive Factors affecting rate of abrasion Abrasive instrument design Classification of abrasive agents Precautions Biological hazards of abrasive agents Recent Advances Summary & Conclusion

3. Craig has defined abrasion as: "A process of wear whereby a hard rough surface (like a sand paper disk) or hard irregular shaped practicles (like those in an abrasive slurry) plough grooves in a softer material and cause materials from these grooves to be removed from the surface".

4. Abrasive action Harder material comes into frictional contact with the substrate Contact generates tensile and shear stresses Break atomic bonds Substrate particles are removed

5. Types of abrasion 1. Two-body abrasion Abrasive bonded to instrument Eg - diamond bur abrading a tooth.  

6. Three-body abrasion Non bonded abrasives Abrasive particles are free Eg - dental prophylaxis paste

7. Erosion Wear caused by hard particles impacting a substrate surface, carried by a stream of liquid or stream of air. Eg . Sand blasting a surface Chemical erosion Acid etching Enhance bonding

8. Principles Cutting Use of any instrument in a bladelike fashion Regularly arranged blades that remove small shavings of the substrate Unidirectional cutting pattern

9. Grinding Removes small particles of a substrate through the action of bonded or coated abrasive instruments Predominantly unidirectional Innumerable unidirectional scratches Eg : a diamond coated rotary instrument

10. Polishing Most refined of the finishing processes Multidirectional in its course of action Acts on an extremely thin region of the substrate surface Progress - fine polishing media Final stage produces fine scratches - not visible unless greatly magnified

11. Desirable Characteristics Of An Abrasive It should be irregular in shape so that it presents a sharp edge. It should be harder than the surface it abrades . Abrasive point should always fracture rather than dull out so that always a sharp point or edge is available. Abrasive should possess attrition resistance so that it does not wear.

12. Factors affecting abrasion Hardness Shape Size Pressure Speed lubricants

13. Factors affecting rate of abrasion Hardness Relates to durability of an abrasive Measure of a material’s ability to resist indentation Abrasive particle must be harder than the surface to be abraded First ranking of hardness was published in 1820 by Friedrich Mohs Knoop and Vickers hardness tests

14. Material Moh’s Brinell Knoop Material Moh’s Brinell Knoop Talc 1 Alumnium oxide 9 1700 1900 Gypsum 2 Silicon carbide 9-10 3000 2500 Chalk 3 Boron carbide 9-10 2800 Rouge 5-6 Diamond 10 >3000 7000 Pumice 6 450 560 SUBSTRATES Tripoli 6-7 Acrylic 2-3 25 Garnet 6.5-7 550 Pure gold 2.5-3 30 Tin oxide 6-7 Porcelain 6-7 400 Sand 7 650 800 Amalgam 4-5 90 Cuttle 7 650 800 Dentin 3-4 Tool steel 800 Enamel 5-6 270 Zirconium silicate 7-7.5 Glass 5-6 Tungsten carbide 9 1200 2100 Resin composite 5-7 200

15. Shape Sharp, irregular particle produces deeper abrasion than rounder particle under equal applied force Numerous sharp edges - enhanced cutting efficiency Abrasion rate of an abrasive decreases with use

16. Size Larger particles size, abrade a surface more rapidly Particles based on their size: 1. Coarse -53 µm to 142 µm, 2. Medium -15 µm to 52 µm, 3. Fine - 7 to 14 µm. 4. Superfine – 2 to 6 um.

17. Pressure Greater force during finishing Abrasive cut deeper into the surface More rapid removal of material Raise in temperature within the substrate Distortion or physical changes within the substrate

18. Deeper and wider scratches are produced by increasing the applied force from F 1 and F 2

19. Speed Faster speed Faster cutting rates Temperature increases Greater danger of overcutting

20. Lubrication Minimize the heat buildup Facilitates removal of debris Cooling action and removal of debris enhances the abrasion process. Water is the most common lubricant Eg . Water, glycerin or silicone Excess lubrication – prevent abrasive contact

21. Abrasive Instrument Design Abrasive Grits. Bonded Abrasives. Coated abrasive disks and strips Non bonded abrasives

22. Abrasive grits Derived from materials that have been crushed and passed through a series of mesh screens Dental abrasive grits based on particle size are Coarse Medium coarse Medium Fine Superfine

23. Bonded abrasives Abrasive particles are incorporated through a binder to form grinding tool Particles are bonded by four general methods: Sintering Vitreous bonding Resinous bonding Rubber bonding (latex or silicon based)

24. Type of bonding and grinding behaviour 1. Bonded a brasives that tend to disintegrate rapidly against substrate are weak Increased abrasive cost - Reduced instrument life 2. Abrasives that tend to degrade too slowly clog with grinding debris Loss of abrasive efficiency, increased heat generation, and increased finishing time

25. Maintenance of the efficiency of abrasive Truing : abrasive instrument is run against a harder abrasive block until the abrasive instrument rotates in the hand piece without eccentricity or runout when placed on a substrate.

26. Dressing : 1)Reduces instrument to correct working size, shape 2)Removes clogged debris (abrasive blinding) - Restores grinding efficiency Truing

27. Coated Abrasive Disks and Strips supplied as disks and finishing strips. Fabricated by securing abrasive particles to a flexible backing material available in different diameters with thin and very thin backings. Moisture – resistant backings are advantageous

28. Abrasive discs : Gross reduction, contouring, finishing, and polishing of restoration surfaces Coated with aluminum oxide abrasive Abrasive strips : With plastic or metal backing are available for smoothening and polishing the interproximal surfaces of direct and indirect bonded restorations

29. Non bonded abrasives Polishing pastes - final polishing. Applied to substrate with a nonabrasive device - synthetic foam , rubber, felt, or chamois cloth. Dispersed in water soluble medium such as glycerin for dental applications. Aluminium oxide and diamond

30. Classification : Natura l abrasives Arkansas Stone Chalk Corundum Diamond Emery Garnet 7. Pumice 8. Quartz 9. Sand 10. Tripoli 11. Zirconium silicate 12. Cuttle 13. Kieselguhr

31. Silicon carbide Aluminium oxide Synthetic diamond Rouge Tin oxide Synthetic Abrasives

32. Arkansas stone Semi translucent , light gray, siliceous sedimentary rock. Contains microcrystalline quartz. Attached to metal shanks and trued to various shapes Fine grinding of tooth enamel and metal alloys

33. Chalk Mineral forms of calcite. White abrasive composed of calcium carbonate. Used as a mild abrasive paste to polish tooth enamel, gold foil, amalgam and plastic materials. 

34. Natural Diamond Transparent colorless mineral composed of carbon Superabrasive Supplied in several forms Bonded abrasive rotary instruments Flexible metal backed abrasive strips Diamond polishing pastes. Used on tooth structure; ceramic and resin based composite materials

35. Diamond abrasive instruments Introduced in the united states in 1942. Consists of 3 parts : metal blank powdered diamond abrasive metallic bonding material. Blank resembles a bur without blades. The diamonds are attached to the blank by electroplating a layer of metal on the blank while holding the diamonds in place against it. Diamond instruments are available in variety of sizes & shapes. More than 200 shapes & sizes are available. Lack of uniform nomenclature for diamond instruments.

36. Various Shapes of Diamond abrasive instruments

37. Diamond particle factors Particle size is categorized as: Coarse (125-150 um) medium (88-125 um) Fine (60-74 um) Very fine (38-44 um) Diamond finishing instruments use even finer diamonds (10-38 um) Only cause of failure of diamond instruments is loss of diamonds from critical areas which results from the use of excess pressure in attempt to increase the cutting rate.

38. Corundum Mineral form of aluminum oxide Physical properties are inferior to those of alpha aluminum oxide. Grinding metal alloys A bonded abrasive in several shapes. Used in instrument – White stone

39. Emery Natural form of an oxide of aluminium Grayish- black corundum Coated abrasive disks Finishing metal alloys or acrylic resin materials.

40. Garnet Dark red, very hard . Comprise - silicates of Al, Co, Mg, Fe, Mn Garnet is coated on paper or cloth with glue. Fractured during grinding  sharp, chisel-shaped plates Grinding metal alloys or acrylic resin materials.

41. Pumice Highly siliceous material of volcanic origin Powder-crushing pumice stone Abrasive action is not very high Polishing tooth enamel, gold foil, dental amalgam and acrylic resins    

42. Quartz Very hard, colorless, and transparent. Crystalline particles are pulverized to form sharp, angular particles - coated abrasive discs. Grinding tooth enamel and finishing metal alloys.

43. Sand Predominantly composed of silica. Particles represent a mixture of color. Making it distinct in appearance. Rounded to angular shape. Applied under air pressure to remove refractory investment materials Coated on to paper disks

44. Tripoli Derived from light weight, friable siliceous sedimentary rock. Rock is ground and made into bars with soft binders Color- white/grey/pink/red/yellow. Grey and red types Polishing for metal alloys and some acrylic resins.

45. Zirconium silicate / Zircon Off -white mineral. Ground to various particle sizes - coated abrasive disks and strips. Component of dental prophylaxis pastes

46. Cuttle Referred to as cuttle fish, cuttle bone, or cuttle . White calcareous powder Available as a coated abrasive Polishing of metal margins and amalgam restorations.

47. Kieselguhr Siliceous remains of minute aquatic plants - diatoms. Coarser form - diatomaceous earth Excellent mild abrasive Risk for respiratory silicosis caused by chronic exposure  

48. Synthetic Silicon C arbide Extremely hard abrasive and 1 st synthetic abrasive Highly effective cutting of metal alloys, ceramics and acrylic resin materials. Abrasive in coated disks and as vitreous - bonded and rubber instruments.

49. Aluminum oxide White powder used as bonded abrasives, coated abrasives and air propelled abrasives. Finishing metal alloys, resin based composites and ceramic materials. Pink and ruby variations- adding chromium compounds

50. Rouge Consists of iron oxide, which is the fine red abrasive component. Blended in to various soft binders in to a cake form. Used to polish high noble metal alloys.

51. Tin Oxide Extremely fine abrasive. Less abrasive than quartz. Polishing teeth and metallic restorations in the mouth. Produces excellent polish of enamel. Mixed with water or glycerin - abrasive paste.

52. Synthetic Diamond Controllable, consistent size and shape. Resin bonded diamonds have sharp edges Larger synthetic diamond particles – greenish Blocks with embedded diamond particles – truing other bonded abrasives Used primarily on tooth structure, ceramics and resin based composites.

53. Dentifrices Available as toothpaste, gels and powders. The abrasive concentrations in paste and gel dentrifices are 50% to 75% lower than those of powder dentrifices Function : Abrasive and detergent action Polish teeth Act as vehicles

54. Prophylaxis pastes removal of exogenous stains, pellicle, material alba, and oral debris. contain moderately abrasive materials : pumice Silcon dioxide and zirconium silicate are used Applied to teeth through rubber cup on a slow speed handpiece  

55. Precautions Heat generation during cutting and contouring , finishing and polishing procedures is a major concern. To avoid adverse effects to the pulp, cool the surface using air water spray and intermittent contact.

56. Biological hazards Aerosols – silica based materials (smaller than 5µm) Silicosis or grinders disease Precautions -adequate water spray, suction - eyeware ,facemasks -proper ventilation

57. Recent Advances

58. Air abrasive Technology Alternative to rotary instrument cutting. High pressure stream of 25-30µm Al 2 O 3 . ‘Air polishing’- controlled delivery of air, water and Sodium bicarbonate slurry.

59. Uses   Cavity preparation Removal of defective restorations Endodontic access through porcelain crowns Minimal preparation to repair crown margins Superficial removal of stains Roughening of internal surfaces of indirect porcelains or composite restorations

60. CVD diamond-coated burs Advantages such as less noise, less pain for the patient, precise cutting, conservative cavity, preparation, longer lifetime, less injury to the dental structures, no cutting of soft tissues and easier access of the carious lesion.

61. Gripped diamond Strips Diamond-coated stainless steel metal strips Features: used for smoothing, contouring, finishing and trimming proximal, incisal and interproximal areas two, color-coded working areas with different grit sizes handles help to pull through tight contact areas

62. Finishing and Polishing system designed to finish and polish all types of resin restoratives By incorporating a superior abrasive into a special resin. System uses a one-piece disc and mandrel - with no metal boss. So that, the possibility of discolouring the restoration has been completely eliminated. It completes intermediate and final finishing without the need to change discs.

63. Perforated Diamond Strips Designed for complete control during inter-proximal reduction, shaping, and contouring. The design assists in debris removal, provides improved visibility, control, and flexibility; made of stainless steel to resist breaking and stretching. They are color coded for grit identification: blue for medium, red for fine and yellow for super-fine.

64. single-gel diamond polishing system it can polish the surface of all restorative materials: composite, glass ionomer , compomer , amalgam, precious metal and enamel. Even porcelain achieves a lustrous surface in less time due to the optimal concentration of micron-sized diamond particles.

65. SUMMARY & CONCLUSION Though a varied range of abrasive and polishing agents have been described with relation to individual dental materials, an ideal abrasive or a polishing agent which would satisfy all polishing needs of the dental materials, one would say is yet to be developed.

66. Sturdevant’s Art and Science of Operative Dentistry, 5 th edition, Elsevier publications. Anusavice , Phillips Science of Dental Materials, 12th edition, Elsevier publications. Craig . Powers and Wataha , Dental Materials, Properties and manipulation, 8 th edition, Elsevier publications. Contemporary fixed prosthodontics . 2 nd Edition, Stephen F. Rosensteil . References

67. Thank You