7 Finishing and Polishing of Restorations.ppt.2 FINAL000

Finishing and PolishingIntroduction Benefits of finishing and polishing Basic armamentarium Principles - Cutting, Grinding, Bulk reduction process, Contouring Air dispersed Hazards during finishing process What is Abrasive & Erosive wear Abrasive Instrument Designs Types of Abrasives - Natural abrasives & Manufactured abrasives Abrasive motion Finishing of various restorations composite, amalgam, ceramic, GIC, and cast gold REFERENCES CONCLUSION Introduction  The finishing process usually removes material such that :    Surface blemishes & imperfections are removed Material is shaped to an ideal form Outermost surface of the material is developed to a desired state Benefits of Finishing and Polishing  Benefits : (a) Health (b) Function (c) Aesthetics High speed tungsten carbide burs steel burs  . finishing and polishing Cutting  Cutting refers to use of a bladed instrument or the use of any instrument in a bladelike fashion.There are distinct differences in function of cutting. Course of action – predominantly unidirectional  Cutting operation – may divide substrate into large separate pieces / produce deep notches or grooves  E. grinding.g. Grinding   It is a process that removes small particle of a substrate through the action of bonded or coated abrasive instruments .contain many randomly arranged abrasive particle . Course of action – predominantly unidirectional Grinding instrument . Eg Diamond coated rotary instrument disk & strips .   . Each particle may contain several sharp points that run along the substrate surface and remove particles of materials . Bulk reduction process  Instruments used   Diamond. . carbide and steel burs Abrasive coated disks or separating disks  Abrasive coated disks –  popular bulk reduction of resin based composite restorations  Clinician should choose 8 to 12 fluted carbide burs or abrasives with particle size of 100 micrometers or more with sufficient hardness. desired anatomy and margins should be established. Usually 12 to 16 fluted carbide burs or abrasives ranging in size from 30 to 100 micrometers provide the fine contouring action.Contouring  Though it can be achieved during bulk reduction. At the end of the process. in some cases it requires finer cutting instruments or abrasives to provide better control of contouring and surface details.   . 3 methods What is Abrasive Blinding ? . 2 .FINISHING AND POLISHING Provides blemish free & smooth surfaces Requires step wise approach 18-30 8-20 um particle size POLISHING : provide enamel like luster Speed of achieving polishing depend on 2 factor a) hardness & size of abrasive b) method of abrasion Polishing & luster can be judged by : 1 . AIR DISPERSED HAZARDS OF FINISHING PROCESS AEROSOL – HEALTH HAZARD 95% of generated aerosol particles .< 5µm in diameter – can readily reach pulmonary alveoli during normal respiration 75% of aerosol particles – potentially contaminated with infectious microorganisms Aerosols can remain airborne for >24hours – therefore capable of cross-contamination . (Fibrotic pulmonary disease) (major aerosol hazard) . swallowed or if it enters the eyes Diseases of the lungs .throat and eyes.If inhaled. Silica based materials if inhaled Silicosis or Grinders disease. Controlled at the source –  adequate infection control procedures  High – volume suction Personal protection –  Safety glasses  Disposable face masks Adequate ventilation system –  To remove any residual particulates from air 2. 3. .AEROSOL .CONTROL  3 ways : 1. WEAR  Wear – is a material removal process that can occur whenever surfaces slide against each other. 2 types a) Abrasive wear b) erosive wear . •Three body abrasion when abrasive particles are free to translate and rotate between two surfaces. Eg. Eg.. Diamond bur abrading a tooth.Three Body Abrasion The two processes are not mutually exclusive Two body abrasion occurs when the abrasive particles are firmly bonded to the surface of the abrasive instrument and no other abrasive particles are used. . . How to prevent it ?.Abrasive wear is divided into: .Two Body Abrasion .. Dental Prophylaxis Pastes.. Erosion  Erosive wear is caused by hard particles impacting a substrate surface. Eg. Air-driven grit-blasting units .employ hard particle erosion to remove surface material  . carried either by a stream of liquid or air. Smoother grinding action – when handpiece & bur are translated in a direction opposite to rotational direction of the bur. (Bur tends to “runaway” from the substrate)  . Rougher surface – when handpiece & bur are translated in the same direction as rotational direction of the bur.   Bur in high speed handpiece rotates in clockwise direction.The rotational direction of a rotary abrasive instrument important factor in controlling the instrument action on the substrate. ABRASIVE INSTRUMENT DESIGNS These are :  Abrasive grits  Bonded abrasives  Coated abrasive disks and strips  Non bonded abrasives . Classification according to particle size ranges:     Coarse Medium coarse Medium fine Super fine .Abrasive Grits Derived from crushed materials passed through a series of mesh screens to obtain different particle size ranges. Particles are bonded by four methods:     Sintering Vitreous bonding Resinoid bonding Rubber bonding .Bonded Abrasives Consist of abrasive particles incorporated through a binder to form grinding tools such as points. wheels etc. Coated Abrasive Disks And Strips  Fabricated by securing abrasive particles to a flexible backing material with a suitable adhesive material. Supplied as disks and finishing strips.  .  Abrasive particles are dispersed in a water soluble medium such as glycerin.  Most popular aluminium oxide and diamond . rubber felt etc.Non Bonded Abrasives  Polishing pastes are considered non bonded abrasives  Primarily for final polishing  Need to be applied to the substrate with a non abrasive device like synthetic foam. Aluminium oxide Synthetic diamond Rouge Tin oxide .Types of Abrasives NATURAL ABRASIVES:    MANUFACTURED ABRASIVES:           Arkansas stone Chalk Corundum Diamond Emery Garnet Pumice Quartz Sand Tripoli Zirconium silicate Cuttle Kieselguhr Synthesized material that are usually preferred – more predictable physical properties      Silicon carbide. Mineral form of calcite. . .Use : polish tooth enamel.Use : to grind tooth enamel & metal alloys CHALK: . light gray. . amalgam & plastic materials. .White abrasive .Semi translucent. mined in Arkansas. . . gold foil.ARKANSAS STONE: .Composed of calcium carbonate.Contains micro crystalline quartz .Can be made into various shapes. siliceous sedimentary rock. hard and uniformly textured.Dense. Usually white .various forms : Bonded rotary instruments Diamond polishing pastes Flexible metal-backed abrasive strips . .Composed of carbon .Most commonly used in instrument known as “white stone” NATURAL DIAMOND: .Hardest substance.Transparent colorless mineral .Use : on ceramic & resin-based composite materials Difference between natural & synthetic diamond . .CORUNDUM: .Mineral form of aluminium oxide .Use : grinding metal alloys. .Resin bonded diamonds sharp edge the sharp edge breaks down. Use cutting points. exposes new sharp edges. corners.Metal bonded diamonds regular. . .SYNTHETIC DIAMOND ABRASIVES: - Advantage: controllable consistent size and shape lower cost .Large synthetic diamond particles greenish. more consistent in size. Use : Grinding metal alloys and plastic materials .Use : Finishing metal alloys or plastic materials GARNET: . .Includes number of different minerals that possess similar physical properties & crystalline forms .Grayish .Extremely hard .black .EMERY: . .Used form of coated abrasive disks.Fine grain form .Usually dark red. dental amalgam QUARTZ:  Most commonly used is very hard colourless and transparent.Use :.Highly siliceous material .Gray .Light .  Use : .PUMICE: .grind dental enamel.gold foil . .polishing tooth enamel .finish metal alloys.2 form:-Grit -Rubber bonded abrasives . . .Rounded to angular shape .SAND: . .Mixture of small mineral particles .Use : Grinding metal alloys & plastic materials TRIPOLI: .grey and red coloured are the most commonly used .Use: Polishing metal alloys and some acrylic resins. .Predominantly composed of silica.Derived from a lightweight siliceous sedimentary rock. . KIESELGUHR: .Use : Mild abrasive .Significant risk of respiratory silicosis .Composed of siliceous remains of minute aquatic plants known as diatoms.Use: .To make coated abrasive disks & strips .As component of dental prophylaxis pastes.ZIRCONIUM SILICATE: .Supplied as an off white material . SILICON CARBIDE: .Use : polishing agent for polishing teeth and metallic restorations ALUMINIUM OXIDE: . coated abrasives and air propelled grit abrasives.Extremely fine abrasive .Use : To make bonded abrasives.Two types. .They are extremely hard and brittle ROUGE: . green and blue .Sintered aluminium dioxide is used to make white stone (popular for adjusting dental enamel and finishing metal alloys & ceramic materials) .Second synthetic abrasive developed .Iron oxide is a fine.Use : Polish high noble metal alloys TIN OXIDE: . . red abrasive component of rouge.First of synthetic abrasives . ABRASIVE MOTION Classified as    Rotary Planar Reciprocal Burs Disks Reciprocating hand pieces Note :Reciprocating hand pieces provide benefit of accessing interproximal and subgingival areas to remove overhangs. to finish subgingival margins without creating ditches and to create embrasures . Finishing and Polishing of Different Restorations . Composites  Armamentarium :       Fibro optic lighting and magnification (for visibility) Fine grit conventional diamonds (for gross reduction) Round tungsten carbide burs (finishing) Flame shaped fluted tungsten burs (finishing) Impregnated rubber wheels or points (finishing) Slurry of fine aluminium oxide (polishing) Composite finishing kit Composite finishing paste impregnated rubber wheels or points . . .Initial finishing by a sharp knife Final Finishing In DCNA 1998 study was done on finishing procedure ………. Amalgam   In the past a delay of 24 hrs had been suggested before finishing and polishing the newly inserted amalgam Armamentarium :           Rhein trimmers (Discrepancies in gingival area ) Bard parker knife number-12 (Bulky overhangs ) Narrow water resistant strip (19)(Cervical areas ) extra fine water proof disk (Buccal and lingual proximal margins ) small carrot shaped stone (20) (Occlusal margins ) plug finishing burs (21) (further adjustment ) Rubber cup (finish accessible proximal surfaces as well as occlusal contours) Abrasive impregnated silicon rubber points and cups tin oxide slurry (complete the finishing and polishing procedures) soft cut brush (complete the finishing and polishing procedures) . . Any sizeable reduction may be undertaken with a carborundum point.Finishing and polishing cannot be started until a future visit when the amalgam will have set hard. Ceramics  Adequate cooling is important in vivo when finishing and polishing ceramic restoration Using an air water spray and maintaining intermittent contact between restoration and rotary instruments are critical during operation   Continuous contact between restoration and rotary instruments should be avoided Heat less stone like silicon carbide provide heat reduction and can be used as an alternative  . diamond burs. cups and points Apply over glaze or natural glaze on ceramic if necessary  .Techniques  Contour with flexible diamond disc. heatless or polymer stones or greenstones  Finish with white stones or abrasives impregnated rubber disc. Glass Ionomer Cement . All the types are fast settig gic and so are resisting to water uptake within 5 to 6 mins from the beginning of mix.Diagramatic representation of water balance in glass ionomer. Type ii and I restorative aesthetic restorations remain succeptible to water uptake for at least one day after placement. . Problem of water loss continues for a longer period for both fast and slow set types and precautions should be taken to prevent dehydration.  The best surface attainable is that produced when the cement is allowed to set against the matrix. carving the cement external to the cavity margins with sharp knives or scalers after initial set is the best process of finishing. margins should be smoothed with hand instruments. Where access can be gained. Glass ionomer should never be finished under dry conditions. Finishing with rotary instruments and final polishing can be undertaken at a subsequent visit. a petroleum lubricant may be used to prevent desiccation.   .   Whenever possible. Finishing Of GIC Restoration Finishing with a bur Finished GIC Restoration . . Air should be blown continuously on the tooth to prevent overheating during all disking.CAST GOLD RESTORATION Use a 1/2 inch medium garnet disc in a straight handpiece to reduce gold and tooth to the same plane on all surfaces (use contra-angle with grit in to reduce mesial-lingual. where necessary. stripping and polishing procedures. for both maxillary and mandibular restorations). . Complete disking with fine cuttle discs until all scratches have been removed. extra-long cuttle strips to reduce the size of scratches.Finished cast gold restoration Use fine and extra-fine narrow. Do not use coarse pumice as it will destroy the finish achieved with the fine cuttle disc. Blow off excess tin oxide while utilizing a ribbed cup (webbed cup will throw powder away from tooth) at low speed to avoid heating the tooth. Use dry tin oxide powder over casting for final polish. Polish with flour of pumice.  . Mount  Allen D. Grundy .R. J.References  Phillips Science of Dental Materials.  Atlas of operative Dentistry  Atlas of G. Wilson  Charbenau  David Korson  Ratnadeep Patil  J. CONCLUSION •Fluted carbide finishing bur appear to be the optimal rotary contouring device •FINISHING DIAMOND preferred for GROSS FINISHING •COATED DISK & STRIPS provides access for interproximal & incisal area •RUBBERIZED BONDED provide great range of FINISHING •ALUMINIUM OXIDE & DIAMOND PASTE are highly effective against POLISHING . THANK YOU & HAVE A NICE DAY…………. .