Polishing Materials and Abrasion PDF

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Professor Sherry Frey ...

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Polishing Materials and Abrasion Cutting - removing material by a shearing off process (results in a somewhat smooth surface) - examples are milling, machining, or drilling, scalers too - cutting is done with metal burs and hand instruments to create cavity and crown preparations - cutting process affected by design and sharpness of burs - lifetime of a dental bur depends on the material from which it is made. - usually made of carbon steel or tungsten carbide. - tungsten carbide burs are harder and maintain a sharper cutting edge than carbon-steel burs (lasting, $) A. B. C. D. E. F. G. H. I. J. K.

Egg or football diamond (cut) Needle diamond (cut) Flame diamond (cut) Round Pear Inverted cone Straight-fissure plain Tapered-fissure plain Tapered-fissure crosscut Needle finishing Egg or football finishing

- finishing have multi fluted burs (serrations are close) - Diamonds for crowns and bridges, gross reduction ($5) - D to I are cutting burs ($2) Hand-Cutting Dental Instruments (Left to Right) 1. 2. 3. 4. 5.

Wedelstadt chisel Spoon excavator Gingival margin trimmer Hoe Hatchet

Abrasion - wearing away of a surface (grinding) - irregular grooves or scratches are produced on a surface as the result of abrasion Finishing - producing the final shape and contour of a restoration - examples used in finishing would be burs and stones Polishing - abrading a surface to reduce the size of the scratches until the surface appears shiny - applies to dentistry in regard to tooth structure and restorative materials (diff than shoes or furniture) Abrasive - material doing the “wearing” (particles may be bound together on burs, disks, stones, wheels, or strips) - may be used with liquids to form a paste or slurry

Tribology - science of interacting surfaces in motion - incorporates the study and application of the principles of friction, lubrication, and wear. - abrasive agent creates friction and wear when it comes in contact with the surface being polished - abrasive agent can be found embedded in a surface such as a polishing wheel or in a moist paste - moist ingredients in the paste serve as the lubricant - polishing can be considered as two body abrasion or three body abrasion Chalk - mineral form of calcite is called chalk (also called whiting or calcium carbonate) - mild abrasive and is used to polish teeth, gold and amalgam restorations, and plastic materials. Pumice - silica like, volcanic glass that is used as a polishing agent on enamel, gold foil, and dental amalgam - for finishing acrylic denture bases in the laboratory - abrasive agent in “lava” hand cleaner and is used to remove dried or callused skin - most common abrasive used in commercially prepared prophylaxis polishing pastes Sand - form of quartz and may be seen in various colors (particles are rounded or angular in shape) - typically bonded to paper disks for grinding metals and plastics Cuttle - a fine grade of quartz (these particles are also bonded to paper disks) - available in coarse, medium, and fine grits Garnet - usually dark red in color, hard, effective abrasive - found on coated disks and is used for grinding plastics and metal alloys. - minerals with similar properties are silicates of manganese, magnesium, iron, cobalt, and aluminum Emery (Corundum) - used to file our fingernails - natural form of aluminum oxide, and it looks like greyish–black sand. - found on arbor bands that attach to a dental lathe for grinding custom trays and acrylic appliances Silex - a commercial product, is a silica-like material such as quartz and is used as an abrasive agent in mouth - supplied as a powder and is mixed with various liquids to form a paste or slurry Tin Oxide - extremely fine abrasive - white powder and is used as a final polishing agent for teeth and metallic restorations - used as a paste or slurry in the same manner as Silex Aluminum Oxide - common abrasive used in dentistry - essentially replaced emery and is widely used in the form of disks and strips - also impregnated into rubber wheels and points - abrasive used in “white stones” to adjust enamel or to finish metal alloys and ceramic materials

Bonded and Coated Abrasives - to use abrasives previously discussed, they must be attached to devices that permit an abrasive action - usually rotary-powered, but in the case of finishing strips, it is accomplished by hand. - examples of these items include the following… A. Diamond Burs - very small diamond chips that are bonded to a shaft - diamonds are hard materials and make very good abrasives - depending on the size of the chips, diamond burs can be used in many procedures B. Stones - available in various shapes, sizes, and grits and they are made from a variety of materials - used in clinical and laboratory procedures C. Rubber Wheels or Points - molded rubber is impregnated with an abrasive into a wheel or point shape - rubber acts as the matrix (or binder) of the abrasive agent - designed for both clinical and laboratory procedures D. Rubber Cups - abrasive agents are embedded in rubber cups intended for polishing - available on disposable prophylaxis angles for use in polishing procedures during an oral prophylaxis - rubber cups with embedded abrasives are not intended to be used with prophylaxis polishing pastes E. Disks and Strips Abrasive particles are bonded to a paper, metal, or plastic backing to form disks or strips. Examples of coated disks and strips can be seen in Figure 16.9. They are used for intraoral and laboratory procedures. F. Powders - used in conjunction with other agents and devices. These agents and devices include… - “vehicles,” such as water, alcohol, glycerin, fluoride or mouthwash, to make pastes or slurries - brushes, rubber cups, felt cones and wheels, and cloth wheels. - some powders are used for lab and clinical procedures, whereas others are used only in the laboratory Factors Affecting the Rate of Abrasion - each student polishes differently - how much paste is put into the cup - size and type of cup - amount of pressure used against the tooth - how fast the cup is rotating and what type of abrasive is in the cup, - the surface being polished (technically abraded) will be significantly affected A. Hardness - abrasive particle must be harder than surface being abraded if an acceptable rate of abrasion is to occur - otherwise, abrasive will be worn, and the surface will not be greatly affected - abrasion rate can be “temperature depen- dent” (the abrasive heats up during use) - object being abraded could become heated, which may make it softer and affect the rate of abrasion - abrasives are usually made of very hard, ceramic materials B. Size - larger abrasive particles will produce deeper scratches than smaller particles

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deeper scratches result in a greater amount of surface material removed. grit describes the size of the abrasive particle finer abrasives such as powders or flours are graded F, FF, and FFF as the fineness increases. when particles bonded to paper, grit is designated as O, OO, and OOO in order of increasing fineness. when a prophy paste is labeled “coarse” or “fine,” label is referring to the grit of the abrasive no standardization in the definition of fine, medium, and coarse grit in prophy pastes “fine” grit paste of one manufacturer may be equal to the “coarse” grit paste of another

C. Shape - spherically shaped particles are less abrasive than irregularly shaped particles - sharp edges on irregularly shaped dig into the surface rather than roll across (increasing abrasion) - cleaning agents have very soft particles or flat particles and do not abrade D. Pressure - excess pressure during finishing and polishing causes a higher abrasion rate - abrasive particle cuts deeper into the surface - Increased pressure may also result in an increased temperature of the material being polished - using heavy pressure on amalgam increases temp, brings mercury to surface, marginal breakdown E. Speed - rate at which the polishing device is rotating (higher speed = more abrasion and higher temp - control the speed of the polishing cup or brush during polishing F. Lubrication - most frequently used lubricant in dentistry is water - used with hand pieces and burs to cool the tooth when cavity preparations are being made - during finishing and polishing, lubrication is also recommended to diminish heat - mix lubricating agents (water, mouthwash, fluoride, glycerin, or alcohol) with abrasive agent (powder) - resulting mixture is “paste” or “slurry” depending on the liquid content The Polishing Process (Why Polish?) - to reduce adhesion, to make surface smooth, for aesthetics, to reduce corrosion - amalgam, a smooth surface inhibits adhesion (plaque, stain, calculus less likely to adhere to smooth) - removes the acquired pellicle on teeth and restoratives (provides medium for adherence for plaque) - patients expect a smooth surface on any restoration that is placed in their mouths (like and value it) - unpolished amalgam or gold crown is not as attractive as the one that appears smooth - aesthetics play a very important role in dentistry, and polishing helps to create an attractive dentition - stain removal for smokers an opportunity to approach smoking cessation for the dental hygienist - when metallic restorations are polished, it reduces tarnish and corrosion (lasts longer) Preparation for Polishing - health history should be completed first to confirm there are no contraindications for polishing. - completion and review of the patient’s chart of existing oral conditions and restorations. - some esthetic restorations are so perfectly matched that detection is almost impossible. - current radiographs should be reviewed and matched with the patient’s chart - confirms the presence or absence of esthetic restorations or any conditions not previously charted! What Happens During Polishing - finer abrasives make smaller scratches, which makes the surface look shiny - if stains are heavy, use a coarse abrasive and follow with a different finer grit and rubber cup - can also use the same abrasive in larger to smaller grits to produce smaller scratches - technique is used commonly in finishing and polishing restorations

Polishing Dilemma Resolved (Selective Polishing) - some people think only stained teeth need to be polished at every appointment (removes fluoride layer) - not therapeutic, and clients can remove plaque themselves - places dental hygienists in an ethical dilemma because clients want and expect it - no scientific proof of how much enamel is removed during polishing procedures, if at all - with the use of cleaning agents all teeth can be polished without abrading teeth or restoratives - heavy stains= coarse med fine, restorations= NO, esthetics= special, no stains= clean, no abrasives - essential selective polishing approach solves all dilemmas related to polishing - eliminates “one polishing paste for all polishing procedures” approach. - unethical to use coarse grits for no stain because restoratives can be compromised and damaged - if a microscopic layer of enamel is removed, it will remineralize in time with salivary minerals - exposure to fluorides will remineralize - goal of polishing is to create a smooth surface on teeth and restorations with the least abrasive agent to Technique - prophy cups and brushes must be changed before the less abrasive agent is used - surfaces being polished should be thoroughly rinsed before the next agent is applied. - if fine and coarse abrasives used on tooth coloured or cast restorations, coarse 1st - avoid restorative materials with coarse abrasive, patient rinse, change cup, and polish with finer agent - slow speed with light, intermittent pressure. - prophy cups for most surfaces, brushes for occlusal surfaces. - demineralized tooth surfaces are weak tooth structure and - polishing may remove surface structure on demineralized teeth compared to intact enamel - gold, composite, amalgam, and glass ionomer could be roughened, margins may be damaged - nonabrasive pastes available for polishing the abutments and pontics of implants - scratched and uneven surfaces are susceptible to adhesion of plaque, stain, and calculus (more rapid) - most pastes supplied in unit-dose cups in a variety of colours, textures, flavours, grits, and pricesA. Prophy Paste Polishing Ability - should not create deep scratches and grooves, but fine, shallow scratches and grooves - Sheet-shaped particles,“Perlite,” convert from coarse to fine with 15 seconds of use. - all abrasives used in pastes break down into smaller and smaller particles during polishing procedures. Abrasive Properties - should not produce a detrimental effect on the surface but it needs to remove the stain - acceptable prophy paste will possess properties of both a high-polish rate and a low-abrasion - a few pastes that exhibit these qualities, as well as some that produce low polish and high abrasion rate. - dentin will abrade 25x faster than enamel, cementum is 35x because they're thin and soft - abrasive polishing agents be contraindicated in recessed areas. “Specialty” Prophylaxis Pastes - some contain therapeutic agents - some transform from coarse to fine (Clinpro) - some have fluoride (D-Lish, Topex, Enamel Pro) - some reduce sensitivity (Nucare, Proclude) - some contain additives, such as amorphous calcium phosphate or bioglass - these claim to strengthen enamel or reduce hypersensitivity Prophy Pastes for Aesthetic Restorations - typical are microfills, hybrids, and compomers (perlite, aluminum oxide, diamond powder abrasives) - traditional pastes shouldn't be used (may roughen) instead use very fine abrasives - available in pastes in unit doses and dispensing syringes, cups, points, and disks.

Air Powder Polishing - traditional utilizes air, water, and a specially formulated polishing powder - original air polishing powder and “gold standard of the air polishing powders” sodium bicarbonate - combines compressed air, water, and sodium bicarbonate into spray - uses kinetic energy to propel the powder polishing particles to the tooth surface - before using powder look at unit warranty (if not approved it may void warranty) 1. Sodium Bicarbonate - original powder used in air-powder polishing - specially formulated with scant amounts of calcium phosphate and silica to keep it free flowing - not the same as over- the-counter-sodium bicarbonate (clogs air powder polishing units) - average 74 µm in size - available in flavours (patient will taste the salt and smell the flavouring) - specially processed types can be safely used on enamel, especially for removal of heavy stains - safe for use on amalgam, gold, porcelain, implants, ortho brackets, bands, and preparing for sealants - contraindicated for use on seal- ants, tooth coloured restorative materials (composites, glass ionomers) 2. Aluminum Trihydroxide - first alternative air polishing powder developed for patients that cannot tolerate sodium bicarbonate - physician directed sodium restricted diet or patients with high blood pressure or renal disease - indicated for patients who have heavily stained enamel. - contraindications are dentin, cementum, amalgam, gold, composites, glass ionomers, and implants - does not cause surface disruption to porcelain - luting agents used for placement of porcelain restorations are removed by aluminum trihydroxide - causes a compromise in the margin (caries develop) 3. Glycine Powder - amino acid, when used in powders, crystals are grown using a solvent of water and sodium salt 4. Calcium Carbonate - naturally occurring substance that can be found in rocks - main ingredient in antacids, and is also used as filler for pharmaceutical drugs 5. Calcium Sodium Phosphosilicate (Novamin) - bioactive glass that is the hardest air polishing par- ticle used in air powder polishing powders. - lack of research, indications and contraindications for use have not been confirmed - air powder polishing should not be confused with air abrasion systems - Air abrasion involves polishing the tooth with a high velocity stream of air - carries a very hard abrasive particle (aluminum oxide) as part of a restorative procedure Contraindications for Air Powder Polishing - physician directed sodium-restricted diet - respiratory disease - conditions that limit swallowing or breathing (COPD) - communicable infections - immunocompromised patients - patients taking potassium, antidiuretics, steroids Air Powder Polishing Technique! - hand piece angled 60 degrees to anteriors, 90 degrees to posteriors and occlusal - high speed evacuation should be used at all times and patients should wear eye protection - hand piece nozzle should kept moving in a constant circular motion and 4 mm to 5 mm from the tooth

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correct angulation is the single best method of controlling excess aerosol production. facial emphysema occurs when the hand piece is angled incorrectly nozzle should never be directed into pockets, extraction sites, traumatic lacerations or surgical wounds facial emphysema occurs when air is entrapped in the soft tissues of the head and neck normally treated with antibiotics area feels “hard to the touch” or patients experience a “crackling” noise in affected area can develop into more serious conditions such as thrombosis and embolism, among others!

Implants - cleaned with air powder polishing units using sodium bicarbonate powder or with a rubber cup - incompatibility of titanium with other metals and some chemicals must be taken into consideration - true polishing agents are contraindicated for dental implants - goal is not to alter (abrade) the surface integrity of the titanium - to remove hard deposits from implants, special plastic hand instruments have been developed Denture Cleansers - dentures will accumulate plaque, stain, and calculus in the same manner as natural teeth. - hygienist’s responsibility to examine the condition of removable appliances - return them to the patient in a deposit-free condition at the end of the appointment. - goal in cleaning and polishing dentures is to remove deposits in a manner too not damage the surface. - care must be taken so that abrasives, rotary devices, or caustic ultrasonic solutions do not damage Dentifrices - the most important constituent in a dentifrice is the abrasive agent - one of several types of abrasives may be added to the dentifrice formulation. - those recommended for smokers used to be very abrasive - ADA evaluates dentifrices in their acceptance program if it meets the specific requirements - based on safety and efficacy, and scientific data - dentifrice must be safe and effective - abrasivity could not exceed a value of 250 - currently, the FDA regulates dentifrices and their abrasivity - manufacturer provides data to ADA to support claims in advertisements and on packaging Abrasives Used in Dentifrices 1. Phosphates - contribute to a whiter look and cleaner “feel” to the teeth - phosphates used in dentifrices are dicalcium phosphate dihydrate and calcium pyrophosphate 2. Carbonates - to make products and environments smell better, in addition to abrasive properties - sodium bicarbonate also called baking soda - has been used to clean silver, deodorize fridges, laundry detergent, dentifrice abrasive - compatible with fluoride, bactericidal against periodontal pathogens, safe, low in abrasivity and cost - the consummate dentifrice ingredient - calcium carbonate is chalk and is one of the most economical mechanical abrasives available - used with calcium carbonate. 3. Silicas - largely nonreactive with other toothpaste ingredients, most frequently used abrasive in recent years - compatible with soluble fluorides

Factors Affecting Abrasion Rate by Dentifrices

- intraoral factors include xerostomia, saliva consistency and quantity, exposed root surfaces, quality and quantity of deposits, and presence of certain restorative materials

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extraoral factors include type, size, and amount of abrasive as well as the quantity of dentifrice used type of toothbrush, method, amount of force, and frequency of brushing are other extraoral factors. abrasive index for toothpastes called Relative Dentin Abrasivity Index, RDA Index, or Radioactive Dentin A...