Abrasives and polishing agents in dentistry

ABRASIVES AND POLISHINGS AGENTS USED PREDOMINANTLY IN PROSTHODONTICS

1. ABRASIVES AND POLISHING AGENTS IN DENTISTRY Presented by – D r.Madhushree patil 1 st year postgraduate ( dept of prosthodontics ) 11/23/2019

2. INTRODUCTION DEFINITION. CONSIDERATION OF ABRASTION AND EROSION DESIGN OF ABRASIVE INSTRUMENTS TYPES OF ABRASIVES POLISHING FINISHING AND POLISHING OF COMMONLY EMPLOYED RESTORATIONS SUMMARY AND CONCLUSION REFRENCES content 11/23/2019

3. INTRODUCTION HISTORY Stones ,spear ,shield and daggers were produced by abrading against a cylindrical stone. Chinese introduced first coated abrasives. In 1900s alumina grains , diamond particles and silicon carbide were used . 8/15/2019

4. ABRASION –The wear away of substances or structure through some unusual or abnormal mechanical process. ABRASIVE AGENTS –Substances used for abrading ,smoothing or polishing. DEFINATION 11/23/2019

5. POLISHING –The act or process of making a denture or casting smooth , glossy and to give lustre . POLISHING AGENTS-Any material used to impart lustre to a surface. 11/23/2019

6. CUTTING It is done using bladed instrument It divides substrate into large separate segments or may sustain deep notches and grooves by cutting operation Eg – carbide bur and diamond burs 11/23/2019 PRINciPLE OF CUTTING,GRINDING AND POLISHING

7. GRINDING Removes small particles of substances through action of bonded or coated abrasive instruments Grinding instruments contains many randomly arranged abrasive particles 11/23/2019

8. FINISHING AND POLISHING – The most refined of finishing processes, remove the finest surface particles . Each type of polishing abrasive acts on an extremely thin region of the substrate surface . 11/23/2019

9. CONSIDERATION OF ABRATION AND EROSION ABRASIVE WEAR Craig has defined abrasion as : “ A process of wear where by a hard rough surface or hard irregular shaped particle plough grooves in a softer material and cause materials from these grooves to be removed from the surface ”. 11/23/2019

10. ACCORDING TO SKINNER :- 1.Wear – Is a material removal process that can occur whenever surfaces slide against each other . In dentistry the outermost particle or the surface material of an abrading instrument is referred to as Abrasive. The material being finished is termed as a SUBSTRATE. 11/23/2019

11. 2. ABRASIVE WEAR Two body wear – occurs when abrasive particles are firmly bonded to the surface of the abrasive instrument and no other and abrasive particles are used eg , a diamond bur abrading a teeth . Three body wear – when the abrasive particles are free to translate and rotate between two surfaces Eg , dental prophylaxis pastes (between tooth and rubber cup). 11/23/2019

12. EROSIVE WEAR Erosive wear – This is caused by hard particles impacting a substrate surface, carried by either a stream of air or a stream of liquid. 11/23/2019

13. The abrasives employed could be one of the three types which are:- A . Abrasive Grits. B. Bonded Abrasives. C. Coated Abrasive Disks and Strips 11/23/2019 DESIGN OF ABRASIVE INSTRUMENTS

14. A. ABRASIVE GRITS Abrasive grits are derived from (abrasive) materials that have been crushed and passed through series of mesh screens to obtain different particle size ranges. The grits are classified as – COARSE, MEDIUM COARSE, MEDIUM FINE and SUPER FINE according to the particle size ranges 11/23/2019

15. B. BONDED ABRASIVE These consists of abrasive particles incorporated through a binder to form grinding tools. The abrasive particles are bonded by 4 general methods : 1. Sintering. 2. Vitreous bonding 3. Resin bonding 4. Rubber bonding. 11/23/2019

16. 1 . Sintering – Sintered abrasives are the strongest variety since the abrasive particles are fused together. 2. Vitreous Bonded – Are mixed with a glassy or ceramic matrix material, cold pressed to the instrument shape and fired to fuse with the binder. 3. Resin Bonded – are cold or hot pressed and then heated to cure the resin. 4. Rubber Bonded – made in a manner which is similar to resin bonded. 11/23/2019

17. C. COATED ABRASIVE DISK OR STRIPES These abrasives are supplied as disks and finishing strips. They are fabricated by securing abrasive particles to a flexible backing material (heavy weight paper or Mylar) 11/23/2019

18. These factors are as follows: 1. The hardness of the abrasive particle . 2. The Shape of the abrasive particle . 3. Particle size of the abrasive . 4. Mechanical properties of the abrasive . 5. Rate of movement of the abrasive particles. 6. Pressure applied 7. Properties of material that is being abraded 11/23/2019 FACTORS INFLUNCING EFFICENCY OF ABRASIVES

19. According to Craig : A. Finishing Abrasives These are hard, coarse abrasives used initially to develop desired contours and remove off gross irregularities. B. Polishing Abrasives These have a smaller particle size and are less hard than abrasives used for finishing. They are used for smoothening surfaces that are typically roughened by finishing abrasives. C. Cleansing Abrasives These are soft abrasives with small particle size and are intended to remove softer materials that adhere to enamel or a restoration. 11/23/2019 TYPES OF ABRASIVES

20. 1. Arkansas Stone 2. Chalk 3. Corundum 4. Diamond 5. Emery 6. Garnet 7. Pumice 8. Quartz 9.Sand 10. Tripoli 11. Zirconium silicate 12. Cuttle 13. Kleselguhr Are generally preferred because of their more predictable physical properties. 1. Silicon carbide 2. Aluminium oxide 3. Synthetic diamond 4. Rouge 5. Tin oxide A . Natural Abrasives B. Manufactured Abrasives Secondly Skinner’s has grouped the abrasives employed in dentistry as follows : 11/23/2019

21. 1 . Arkansas stone Semitranslucent , light gray, siliceous sedimentary rock, mined in Arkansas. It contains microcrystalline quartz. USES- fine grinding of tooth enamel and metal alloys . 2 . Chalk Mineral form of calcite. Contains calcium carbonate. USES - as mild abrasive paste to polish teeth enamel, gold foil , amalgam and plastic materials. 11/23/2019

22. Corundum I s largely replaced by – Aluminium oxide due to its superior physical properties. USES for grinding metal alloys. DIAMOND I s a transparent mineral composed of carbon called super abrasive because of its ability to abrade any other known substance. It is the hardest substance known. USES - ceramic and resin based composite materials. 11/23/2019

23. EMERY This abrasive is a grayish black corundum that is prepared in a fine grain form. USES for finishing metal alloys or plastic materials GARNET T he term garnet includes several minerals which possess similar physical properties like Silicates of Al, Co, Fe, Mg and Mn . Garnet is dark red, extremely hard and when fractured during abrasive activity forms sharp chisel shaped plates . USES in grinding metal alloys and acrylic resin materials. 11/23/2019

24. Pumice Volcanic activity produces light gray Siliceous material. Flour of pumice is an extremely fine grinded volcanic rock derivative from Italy . USES in polishing teeth enamel, gold foil, dental amalgam and acrylic resins . Quartz The particles are pulverized to form sharp angular particles which are useful in making coated abrasive disk. USES to finish metal alloys and may be used to grind dental enamel. 11/23/2019

25. SANDS Is a mixture of small mineral particles predominantly silica. Particles have rounded to angular shape. USES- to remove refractory investment material from base metal castings and is also used for grinding of metal alloys and dentures. TRIPOLI Derived from a lightweight, siliceous sedimentary rock Could be white, gray, pink, red , yellow USES- for polishing metal alloys And dentures 11/23/2019

26. Zirconium silicate Off white mineral, ground to various sizes used to make coated disks and strips . USES as a component of dental prophylaxis pastes. Cuttle Made from the pulverized internal shell of a Mediterranean marine mollusk, this abrasive is obtained as a white calcareous powder. USES for delicate operations like polishing of metal margins and dental amalgam restorations . 11/23/2019

27. Kleselguhr This abrasive is obtained from the silaceous remains of minute aquatic plants known as diatoms . The coarser variety is known as DIATOMACEOUS EARTH May cause respiratory silicosis . USES as a filler for dental materials such as agar. 11/23/2019

28. 1.Smoothen the work with a coarse abrasive to produce large scratches. 2.Remove large scratches with a finer abrasive 3.Continue using the fine abrasive until scratches are no longer visible 4.Primary polishing with pumice flour with a canvas buff wheel 5.Then the work is cleaned to remove all abrasive particles and then pumice and water paste of a muddy consistency is applied and buffing done till a bright and well polished surface is obtained. 6.Clean the work with soap water and change to a buff wheel. Polishing cake with grease is held against buff wheel to impregnate with the agent. 11/23/2019 POLISHING

29. FINISHING AND POLISHING OF COMMONLY EMPLOYED RESTORATIVES Amalgam After initial carving, restoration is left undistributed for an appropriate period . Polishing is done through the sequential use of finishing fine stone and disks or strips. Final polish is done by the application of extra fine silen ; followed by a thin slurry of tin oxide with a rotating soft brush. During final polishing restoration should be kept moist. 11/23/2019

30. Composites: The smoothest surface on a freshly inserted composite can be obtained by allowing polymerization to occur against an inserted Mylar matrix. Use of green/carbide stones 12 - blade carbide burs is also accepted for removal of excess near enamel margins of macro filled resins. This is followed by use of: Aluminium oxide disks – for accessible areas finishing. White source stones of suitable shapes – inaccessible areas. Fine and micro fine diamonds – finishing of micro filled resins. 11/23/2019

31. Rescent advances in polishing agents A zirconia based ceramics crowns are difficult to polish due to its brittleness, polishing pressure, pad wear, subsurface damage, and microcracks arising during conventional polishing processes. A new polishing technology using magnetorheological (MR) fluids was intoduced MR fluids are suspensions of very small magnetic additives, such as carbonyl iron , and nonmagnetic fluids such as mineral oils or water. Hong, K.-P., (2012).  Magnetorheological (MR) Polishing of Zirconia Ceramics Using Diamond Abrasives for Dental Application. Materials and Manufacturing Processes, 27(10), 1135–11 11/23/2019

32. RESULT A very fine surface roughness of 1.960 nm was obtained when the electric current was 0.5 A and the wheel rotational speed was 300 rpm after 60 minutes of MR polishing. From the results of this study it can be seen that the applied MR polishing method provides a suitable polishing technique to obtain ultraprecision surface qualities of ceramics . 11/23/2019

33. 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. 11/23/2019 SUMMARY AND CONCLUSION

34. REFERENCES 1.Kenneth J. Anusavice “Philips Science of Dental Materials”. 10th edition, 1998 ; W.B. Saunders Publications. 2.Ralph W. Phiips “Skinner’s Science of Dental Materials”. 9th edition, 1992 ; W.B. Saunders Publications. 3.Combe E.C. “Notes on Dental Materials”. 6th edition, Churchill, Livingstone Publications. 4.Subbarao V. “Notes on Dental Materials”. 3rd edition, 1997 ; V.K.S. Publications. 5.Robert G. Craig, William O’Brien and John M. Powers “Dental Materials – Properties and Manipulation”. 5th edition, 1992; Mosby Publications. 11/23/2019