Dental Materials - Chapter 16 PDF

**POLISHING** - involves the *abrasion of a surface by an abrasive agent* that is harder than the surface to be abraded, or polished. **CLEANING AGENT** - is *not abrasive and will not alter the surface* characterization of enamel or esthetic restorative materials I. **[DEFINITIONS]...

**POLISHING** - involves the *abrasion of a surface by an abrasive agent* that is harder than the surface to be abraded, or polished. **CLEANING AGENT** - is *not abrasive and will not alter the surface* characterization of enamel or esthetic restorative materials I. **[DEFINITIONS]** A. **CUTTING** - refers to removing material by a shearing-off process. When dental burs are used, the cutting process is affected by: 1. Design of the Bur 2. Sharpness of the Bur - Usually, cutting burs are made of carbon steel or tungsten carbide. - **Tungsten carbide burs** are made by packing powdered metal constituents into a mold and then sintering at high temperatures. B. **ABRASION** - it is the *wearing away of a surface*. - It may also be referred to as grinding. - Irregular grooves or scratches are produced on a surface as the result of abrasion. C. **FINISHING** - The process of producing the *final shape and contour of a restoration*. D. **POLISHING** - the *process of abrading a surface* to eventually reduce the size of the scratches *until the surface appears shiny*. E. **ABRASIVE** - The material doing the "wearing" (abrading). F. **TRIBOLOGY** - the science of interacting surfaces in motion Within the science of tribology, polishing can be considered as two-body abrasion or three-body abrasion. 1. **TWO-BODY ABRASION POLISHING** - the abrasive agent particles are *solidly fixed to a substrate*, such as a dental bur, disk, wheel, strips, or in rubber cups impregnated with abrasive agents that *do not require polishing paste* 2. **THREE-BODY ABRASION** - occurs when *abrasive particles move in a space* between the surface being polished and the application device II. **[TYPES OF ABRASIVES]** A. **CHALK** - A mineral form of calcite - It is also called *whiting or calcium carbonate.* - a *mild abrasive* and is used to polish teeth, gold and amalgam restorations, and plastic materials. B. **PUMICE** - a silica-like, volcanic glass that is used as a polishing agent on enamel, gold foil, and dental amalgam and for finishing acrylic denture bases in the laboratory. - also found in clay, is the *most common abrasive* used in commercially prepared prophylaxis polishing pastes. C. **SAND** - a *form of quartz* and may be *seen in various colors*. - Sand particles are *rounded or angular* in shape. - They are typically *bonded to paper disks for grinding metals* and plastics. D. **CUTTLE** - a fine grade of quartz. - These particles are also *bonded to paper disks* and are *beige in color*. E. **GARNET** - usually, *dark red in color*. Because it is *very hard*, garnet is a highly effective abrasive - refers to *several different minerals that have similar properties.* F. **EMERY** - sometimes also called "corundum." - a natural form of aluminum oxide, and it looks like grayish-black sand. G. **SILEX** - a commercial product, is a *silica-like material such as quartz* and is *used as an abrasive agent* in the mouth. - It is supplied as a powder and is mixed with various liquids to form a paste or slurry. H. **TIN OXIDE** - An *extremely fine abrasive,* tin oxide is supplied as a white powder and is *used as a final polishing agent* for teeth and metallic restorations I. **ALUMINUM OXIDE** - a common abrasive used in dentistry, and it has essentially replaced emery for several uses. - widely used in the form of disks and strips - It is the abrasive used in the popular "white stones" to adjust enamel or to finish metal alloys and ceramic materials. III. **BONDED** **AND COATED ABRASIVES** A. **DIAMOND BURS** - are actually very small diamond chips that are bonded to a shaft. B. **STONES** - are available in various shapes, sizes, and grits, and they are made from a variety of materials. C. **RUBBER WHEELS/ POINTS** - Molded rubber is impregnated with an abrasive into a wheel or point shape. - The rubber acts as the matrix (or binder) of the abrasive agent. D. **RUBBER CUPS** - Abrasive agents are embedded in rubber cups intended for polishing. E. **DISKS AND STRIPS** - Abrasive particles are bonded to a paper, metal, or plastic backing to form disks or strips. F. **POLISHING POWDERS** - used in conjunction with other agents and devices - These agents and devices include the following: - "Vehicles," such as water, alcohol, glycerin, fluoride, or mouthwash, are used to make pastes or slurries for polishing. - Brushes, rubber cups, felt cones and wheels, and cloth wheels are used to move an abrasive or polishing agent over the surface to be polished. IV. **FACTORS AFFECTING THE RATE OF ABRASION** A. **HARDNESS** - The abrasive particle must be harder than the surface being abraded if an acceptable rate of abrasion is to occur - B. **SIZE** - **Grit** is a term that is used to describe the size of the abrasive particle. - Finer abrasives such as powders or flours are graded F, FF, and FFF as the fineness increases. - When the particles are bonded to paper, the grit is designated as O, OO, and OOO in the order of increasing fineness. - When a prophy paste is labeled "coarse" or "fine," the label is referring to the grit (or particle size) of the abrasive C. **SHAPE** - Spherically shaped particles would be less abrasive than irregularly shaped particles D. **PRESSURE** - excess pressure during finishing and polishing causes a higher abrasion rate because the abrasive particle cuts deeper into the surface. E. **SPEED** - refers to the *rate at which the polishing device is rotating* F. **LUBRICATION** - The most frequently used lubricant in dentistry is **water**. V. **[THE POLISHING PROCESS]** A. WHY WE POLISH 1. To Reduce Adhesion 2. To Make the Surface Feel Smooth 3. To Increase Esthetics 4. To Reduce Corrosion B. PREPARATION FOR POLISHING 1. **Health History:** Before any dental treatment, the patient\'s health history must be reviewed to ensure there are no issues that would prevent polishing. 2. **Review of Oral Conditions:** The patient's chart, including existing oral conditions and restorations, should be checked to understand their dental situation and identify any esthetic restorations. 3. **Review of Radiographs:** Current X-rays should be checked alongside the patient's chart to confirm the presence of restorations and ensure no conditions were missed. C. WHAT HAPPENS DURING POLISHING - Polishing is done in steps, using abrasives that get finer each time. This makes the scratches smaller until they are too small to see, making the surface shiny. For cleaning teeth, we start with a rough abrasive for heavy stains, then use a finer one to smooth it out. Another method uses a range of abrasives, from coarse to fine, to reduce scratches, which is often done when polishing dental restorations. D. A POLISHING DILEMMA RESOLVED 1. **Selective Polishing Theory:**\ It was once suggested that only stained teeth need polishing, not all surfaces. The idea was based on the fact that plaque removal can be done by the patient and stain removal is not a therapeutic procedure. 2. **Ethical Dilemma for Hygienists:**\ The selective polishing approach created an ethical dilemma. Patients expect all their teeth to be polished for a smooth, clean feel, and some felt they weren\'t getting value for their money if not all teeth were polished. 3. **Concerns about Enamel Removal:**\ Hygienists were concerned that selective polishing could lead to the removal of the fluoride-rich outer enamel layer, especially when polishing only heavily stained teeth. 4. **No Clear Proof on Enamel Removal:**\ There\'s no scientific evidence proving that polishing removes significant amounts of enamel. New cleaning agents like ProCare allow polishing without damaging teeth or restorations. 5. **Essential Selective Polishing:**\ This method emphasizes selecting the right polishing agent based on the patient\'s needs. For stained teeth, coarser pastes should be used, while for unstained teeth, non-abrasive cleaning agents should be used. 6. **Avoid Polishing Esthetic Restorations with Regular Pastes:**\ Esthetic restorations (e.g., crowns, veneers) should not be polished with regular prophylaxis pastes. Special pastes for such materials should be used to avoid damaging them. 7. **Unethical Polishing Methods:**\ Using a one-size-fits-all polishing paste or always using coarse pastes for all teeth is considered unethical because it ignores individual patient needs and can damage restorative materials. 8. **Enamel Remineralization:**\ Even if a small amount of enamel is removed during polishing, it will naturally remineralize over time with the help of salivary minerals and fluoride treatments. E. POLISHING TECHNIQUE 1. **Preventing Abrasive Contamination:**\ To avoid contamination, change prophy cups or brushes before using a less abrasive agent. Thoroughly rinse the surfaces before applying the next agent. 2. **Polishing Teeth and Restorations:**\ When using both coarse and fine abrasives, start with the coarse abrasive on the tooth structure, avoid using it on restorations, have the patient rinse, change the prophy cup, and then polish with the fine abrasive on restorations. 3. **Recommended Technique:**\ Use slow speed with light, intermittent pressure. Prophy brushes are best for occlusal surfaces but may cause gingival trauma. 4. **Demineralized Teeth:**\ Demineralized teeth are weaker, and rubber cup polishing can remove more surface structure compared to healthy enamel. 5. **Effect on Restorations:**\ Polishing can roughen restorative materials (like gold, composite, or amalgam) and may damage the margins of restorations. Nonabrasive pastes are available for polishing implants. 6. **Purpose of Polishing:**\ The goal is to create the smoothest surface possible. Coarse abrasives create scratches that make the surface more prone to plaque, stain, and calculus buildup, which defeats the purpose of polishing. VI. **[PROPHYLAXIS PASTE]** A. POLISHING ABILITY B. ABRASIVE PROPERTIES - The abrasive particle used in the paste should not produce a detrimental effect on the surface. It must, however, remove the stain. - It must be remembered that dentin will abrade 25 times faster than enamel. Cementum, which is only temporarily present in areas of gingival recession, will abrade 35 times faster than enamel because of its thin layer and "softness. C. "SPECIALTY" PROPHYLAXIS PASTES 1. **Prophy Pastes with Additional Benefits:**\ Manufacturers have created prophy pastes that not only clean and polish but also offer additional therapeutic benefits, such as fluoride, sensitivity reduction, or enamel strengthening. 2. **Coarse to Fine Transition Pastes:**\ Some pastes, like **Clinpro** (3M/ESPE), change from coarse to fine as you polish the tooth. This allows for a more efficient polishing process as the abrasive particles become smaller with each step. 3. **Fluoride-Containing Pastes:**\ Pastes like **D-Lish**, **Topex**, and **Enamel Pro** contain different types and amounts of fluoride. These can help protect and strengthen enamel during the polishing process. 4. **Sensitivity-Reducing Pastes:**\ Some pastes, like **NuCare** and **ProClude**, are designed to help reduce tooth sensitivity. 5. **Lack of Research on Additives:**\ While some prophy pastes contain additives like **amorphous calcium phosphate** or **bioglass**, which claim to strengthen enamel or reduce sensitivity, there is limited research proving their effectiveness. D. PROPHY PASTES FOR ESTHETIC RESTORATIONS - **Demand for Esthetic Restorations:**\ There has been an increased demand for esthetic restorations like microfills, hybrids, and compomers. - **Avoid Traditional Prophy Pastes on Esthetic Restorations:**\ Many traditional prophy pastes should not be used on esthetic restorations due to their softer composition, as they may create rough surfaces or damage the resin coating. - **Use Special Pastes for Esthetic Restorations:**\ Prophylaxis pastes specifically formulated for esthetic restorations contain abrasives like perlite, aluminum oxide, or diamond powder. - **Use Non-Abrasive Cleaning Agents if Uncertain:**\ If unsure, it is safer to use a cleaning agent that won\'t abrade esthetic restorative materials. - **Follow Manufacturer's Recommendations:**\ If the brand of restorative material is known, follow the manufacturer's guidelines for polishing, as they may recommend their own product for the job. - **Polishing Agents from Manufacturers:**\ Manufacturer-recommended polishing agents typically contain very fine abrasives and come in various forms like pastes, unit doses, syringes, cups, points, and disks. VII. **[AIR POWDER POLISHING]** A. **Traditional Air Powder Polishing:** - **Uses air, water, and polishing powder** (originally sodium bicarbonate) to clean teeth. - **Sodium bicarbonate** is the \"gold standard\" and is combined with air and water to remove stains and polish teeth. B. **Air Polishing Powders:** - **Important to use the right powder** for your polishing unit, or it could void the warranty. - Some powders, like **glycine** and **erythritol**, are used subgingivally and help improve inflammation in periodontal diseases and peri-implantitis. **Types of Air Polishing Powders:** 1. **Sodium Bicarbonate:** - **Original powder** for air polishing, safe for enamel, and good for stain removal, especially from tobacco or chlorhexidine. - **Not for sealants or tooth-colored materials** (composites, glass ionomers). - **Safe for various materials** like amalgam, gold, porcelain, and implants. - 2. **Aluminum Trihydroxide:** - Alternative for patients who can't tolerate sodium (e.g., on sodium-restricted diets). - **Contraindicated** for dentin, cementum, composites, glass ionomers, and implants. - **Safe for porcelain**, but may damage the luting agent around porcelain restorations. - The Mohs hardness number for aluminum trihydroxide is 4 and the particles range in mesh size from 80 to 325 μm 3. **Glycine Powder:** - **Least abrasive** powder with a Mohs hardness of 2. - **Safe for enamel and soft tissues**, often used for periodontal cleaning. - Glycine particles for use in air polishing are 18 to 22 μm in size 4. **Calcium Carbonate:** - Found in **antacids** and naturally occurring in rocks. - **Moderately abrasive** with a Mohs hardness of 3, used for stain removal but less commonly than other powders. - The size of the calcium carbonate particle is 60 to 70 μm - also called chalk or whiting. 5. **Calcium Sodium Phosphosilicate (Novamin):** - **Hardest air polishing powder** with a Mohs hardness of 6. - **Highly abrasive** and **not recommended** for enamel, composites, or glass ionomers. - a bioactive glass and has a Mohs hardness number of 6, and particle sizes range from 20 to 120 μm 6. **Erythritol:** - **Softest powder** available, good for use **subgingivally** to reduce inflammation. - **Compatible with enamel, composites**, and periodontal tissues. - Still under research and **not yet available in the U.S.** at the time of writing. - Erythritol is the softest of all air polishing powders C. Contraindications for Air Powder Polishing Air powder polishing should not be used on: D. Air Powder Polishing Technique VIII. **[IMPLANTS]** - **Polishing Units with Sodium Bicarbonate Powder or Rubber Cup:** - When polishing, **sodium bicarbonate powder** or a **rubber cup** with an appropriate cleaning agent is commonly used. - **Titanium compatibility** must be considered, as it does not react well with some metals or chemicals during polishing. - **Titanium and Dental Implants:** - **True polishing agents** should not be used on **dental implants** (especially titanium) to avoid altering or abrading the surface integrity. - **ProCare Cleaning Agent:** - **ProCare** is a cleaning agent with **low abrasion** and **high polishing properties**, ideal for removing soft debris. - It features round, softer, flat particles that are **not gritty** and are effective in polishing without harming surfaces. - **Special Tools for Hard Deposits:** - To remove **hard deposits** from implants, **special plastic hand instruments** and **plastic sheaths for ultrasonic scaling instruments** are used to protect the titanium surface. IX. **[DENTURE CLEANSERS]** - **Plaque, Stain, and Calculus on Dentures:** - **Full and partial dentures** can accumulate plaque, stain, and calculus similar to natural teeth. - The dental hygienist is responsible for examining the condition of removable appliances and ensuring they are returned to the patient **deposit-free**. - **Denture Base Materials and Teeth:** - **Denture base materials** and **denture teeth** are considered dental materials, and hygienists provide professional care for them. - **Cleaning and Polishing Dentures:** - Dentures can be cleaned and polished in several ways, as discussed in dental hygiene textbooks. - The goal is to remove **deposits without damaging** the denture surface. - **Caution with Cleaning Techniques:** - Care must be taken to avoid damage to the denture. **Abrasives**, rotary devices, and **caustic ultrasonic solutions** should be used carefully to prevent harm to the surface of the denture. X. **[DENTRIFICES]** - **Abrasive Additives in Dentifrices:** - **Various abrasives** are added to dentifrices to clean teeth. Past dentifrices were considered too abrasive, especially those marketed for smokers. - The **American Dental Association (ADA)** evaluates dentifrices through its Acceptance Program to ensure they meet specific safety and efficacy standards. - **ADA Requirements for Dentifrices:** - **Safety and Efficacy:** Dentifrices must be both **safe** and **effective**. The **FDA** regulates dentifrices for abrasivity, and **ADA** and **ISO** have their own standards. - **Scientific Data:** Dentifrice manufacturers must provide **scientific evidence** to support any claims, often gathered from clinical trials. **Abrasives Used in Dentifrices:** 1. **Phosphates:** - **Phosphates** like **dicalcium phosphate dihydrate** and **calcium pyrophosphate** are used in dentifrices to help **whiten** and give a **cleaner feel** to the teeth. 2. **Carbonates:** - **Sodium Bicarbonate (Baking Soda):** - Used since the 1920s for cleaning silver and later as a **deodorizer**. It is now used in dentifrices due to its **low abrasivity** and **compatibility with fluoride**. - Studies show it's **bactericidal** against periodontal pathogens and **cost-effective**. - **Calcium Carbonate (Chalk):** - Known as **chalk**, it's an **affordable abrasive** used in dentifrices and is typically used with **sodium monofluorophosphate** for added fluoride benefits. 3. **Silica:** - **Silica** provides cleaning and abrasivity and is available in various sizes. - It's commonly used in **whitening** dentifrices because it can be manufactured to be **translucent** for gel-type pastes. - **Nonreactive** with most toothpaste ingredients, making it a safe and popular choice in modern dentifrices. **Factors Affecting Abrasion Rate of Dentifrices:** 1. **Intraoral Factors:** - Factors like **xerostomia (dry mouth)**, **saliva consistency and quantity**, **exposed root surfaces**, and the **amount/quality of deposits** affect how abrasively a dentifrice will work. - The presence of **restorative materials** (like fillings) also plays a role. 2. **Extraoral Factors:** - The **abrasive type**, **particle size**, and **amount of dentifrice** used are all important. - The type of **toothbrush** used, brushing **method**, **force applied**, and **brushing frequency** also impact abrasion. **Relative Dentin Abrasivity (RDA) Index:** - The **RDA Index** measures the abrasivity of dentifrices and is used to compare different toothpaste products. - **Method of testing:** - Human teeth are made **radioactive** and stripped of enamel. - **Brushing machines** with the test dentifrice are used to measure how much dentin is abraded. - Results are compared with a **reference material** to calculate the abrasivity score. - **RDA Score:** - An RDA score **over 100** indicates abrasiveness. - The ADA and **ISO** require a score between **200 to 250** or less for a dentifrice to be considered safe. - **FDA limit** is set at **200** to ensure it doesn\'t abrade dentin too quickly. - **Limitations of Testing:** - The RDA test is performed in a **lab** and may not fully represent **real-world (in vivo)** conditions during everyday brushing. **[SUMMARY:]** - **Basic Terms in Cleaning and Polishing:** - **Cutting**: Removing material by shearing-off. - **Abrasion**: Wearing away of a surface. - **Finishing**: Creating the final shape and contour of a restoration. - **Polishing**: Reducing the size of scratches to make a surface shiny. - **Abrasive**: Material used for wearing or abrading surfaces. - **Devices for Abrasive Action:** - Abrasives are attached to devices like **diamond burs**, **stones**, **rubber wheels**, **disks**, **strips**, and **powders** for use in dental procedures. - **Factors Affecting Abrasion:** - **Hardness**, **size**, **shape**, **pressure**, **speed**, and **lubrication** influence the rate of abrasion. - Excessive abrasion can occur with **dry abrasive**, **hard-bristle prophy brushes**, and **high pressure/speed**. - A **wet fine-grit paste** with **gentle pressure** and **slow speed** produces a smooth, shiny surface with low abrasion. - **Reasons for Polishing:** - **Reduce adhesion** to prevent plaque and deposit buildup. - **Create a smooth surface** for improved esthetics and reduced corrosion. - **Selective polishing** protocols are recommended to avoid over-polishing. - **Prophylaxis Pastes:** - Pastes come in various **colors**, **textures**, **flavors**, and **grits**. - Recommended pastes should have **high polish** and **low abrasion**. - Some pastes contain **fluoride**, **desensitizing agents**, or transition from **coarse to fine abrasives**. - **Denture Care:** - Denture base materials and teeth must be cleaned without causing harm to the prosthesis. - Plaque and calculus should be removed carefully during dental hygiene appointments. - **Dentifrices and Abrasive Agents:** - **FDA-approved** and **ADA-accepted** dentifrices must meet specific abrasivity levels and have supporting scientific data. - Abrasives in dentifrices include: - **Phosphates** (whitening and cleaning). - **Carbonates** (e.g., **sodium bicarbonate**), which is safe, low in abrasivity, and compatible with fluoride. - **Silica**, the most commonly used abrasive in modern dentifrices. - **Air Powder Polishing:** - **Air powder polishing** uses **air**, **water**, and an **abrasive** to clean teeth, orthodontic bands, and implants. - **Selective powders** can be used subgingivally and may help reduce inflammation in peri-implantitis and periodontally involved teeth. - **Titanium implants** require **cleaning agents**, not abrasives, to prevent surface alteration. REVIEW QUESTIONS: 1. Which type of abrasive looks like a grayish-black sand and is sometimes called "corundum"? a. Emery 2. Which type of abrasive is produced from volcanoes and is used in the laboratory and on restorative materials, such as gold, amalgam, and gold foil? b. Pumice 3. Which abrasive is used as a slurry to polish amalgam restorations and is also called calcium carbonate? c. Whiting 4. When an abrasive on a dental restorative material is used, the abrasive action must be\_\_\_\_\_the surface you are abrading. d. Harder than 5. All of the following factors affect the rate of abrasion except one. Which one is the EXCEPTION? e. Bonded and coated abrasives 6. The process of producing the final shape and contour of a restoration is termed: f. Finishing 7. An example of a "vehicle" to be used with powders would be: g. Glycerin 8. Polishing involves using a series of finer and finer abrasives. It can also be accomplished by using the same abrasive material in a progression of larger to smaller grit. h. Both statements are true. 9. During routine polishing with pumice,\_\_\_\_\_μm of the fluoride-rich layer can be removed. i. 3 to 4 10. The recommended prophylaxis pastes possess the properties of: j. High polish and low abrasion 11. Which of the following is harder than enamel? k. Pumice 12. Air powder polishing is designed to remove: l. Biofilm and stain 13. The most frequently used abrasive in dentifrices is: m. Silica 14. Which of the following abrasives would most likely be found in a polishing agent for esthetic restorations? n.. Diamond powder 15. Mrs. Smith presents for her prophylaxis appointment after a year, rather than the 6-month prescribed time. She has tobacco stain on the lingual surfaces of her natural teeth, two gold alloy crowns, and several esthetic restorations. Which combination of cleaning/polishing agents should be chosen? o. Traditional prophy paste, tin oxide, and a polishing agent for esthetic restorations