DENTAL MATERIALS I Unit I Dental Materials A. Introduction B. History 1. Phoencians/Egyptians - 2150 B.C. 2. Chinese - 2700 B.C. 3. Romans/Etruscans - 166-201 A.D. 4. Italy - Marco Polo -1295 A.D. 5. France - Pierre Fauchard - 1728 6. France - M. Taveau 7. United States - 1750-1810 Paul Revere John Greenwood 8. United States - G.V. Black 1895 9. National Bureau of Standards - 1919 Today: National Institute for Standards and Technology C. Importance to Auxiliaries Properties measured in the laboratory, when properly related and corroborated by the clinical evaluation, form the selection criteria that should be part of the professional knowledge of the dentist and auxiliary. 1. Chairside Assistant RDA/CDA 2. EFDA
3. RDH D. Terminology Begin Looking Up Terms E. Specifications 1. American Dental Association ADA -1928 a. A manufacturer can submit their new materials to the ADA for certification. At this point the seal of acceptance of the ADA can be placed on the material. b. Once the requirements for the mechanical /physical/chemical properties have been researched the specifications and standards are set. The ADA Seal of Certification is then awarded. 2. ISO - (International Standards Organization) is the foreign equivalent for specifications for 51 countries. Australia uses FDI (Federation Dentaire International). 3. FDA - The Food and Drug Administration - The food and drug act of 1906 (amended in 1976) gave the FDA regulatory jurisdiction over the safety and efficacy(competence) of medical and dental materials and devices. Including all OTC s a. Safety of Materials b. Recent Conditions c. Dental Personnel 4. EPA - Environmental Protection Agency is an agency that regulates the disposal of waste materials from medical and dental offices.
5. OSHA - Occupational Safety and Health Association a. Employee Safety b. MSDS - Material safety data sheets Unit II Dental Materials and the Oral Environment A. Physical Considerations The dentist is like an engineer. He/she must build a restoration with considerations that begin with a good foundation. The restoration or replacement of tooth structure is never simple. The dentist is restricted in the design of the restoration or appliance that can be placed on the tooth or in the mouth. Only a small amount of tooth structure can be removed safely without injuring vital tooth. The following characteristics constitute the physical demands on tooth structure and the materials used in its replacement. It is extremely difficult to formulate restorative materials that resist fracture, temperature changes, alterations in ph, and discoloration while matching the appearance of nature tooth structure. The conditions in the oral cavity, especially limitations of each materials must be understood when selecting and using dental materials. The following must be taken into account when determining the treatment plan. 1. Limitations Access and visibility are sometimes the most important factor in consideration of which restoration or material will be most suitable. 2. Design Restrictions Physical and biological considerations in the oral cavity often prevent the dentist from using the most ideal restoration or appliance. The dentist may not be able to provide the bulk of material required to make the restoration or appliance string enough to withstand the masticatory forces so bulk and physical properties are a big consideration.
3. Health Considerations The oral cavity is ideally suited for destruction, not only of enamel but of restorative materials too. Many materials with superior physical properties may not be able to be used because of harm or injury to the oral mucosa, they may not be esthetically pleasing or too hard to manipulate. 3. Health Considerations a. Appearance b. Chemical Elements c. Allergies 4. Biting Forces 5. Temperature Changes 6. Acidity B. Biological Considerations Local or systemic injury to oral or other tissues is extremely important just as the physical considerations are. Strength and resistance to corrosion are unimportant if the material damages the pulp or soft tissues. The oral cavity is the beginning of the gastrointestinal system. 1. Microleakage 2. Temperature Effects
3. Galvanism 4. Chemical Irritation C. Classification of Restorative Materials Methods of classification are based on either composition (metal, plastic, resin) or the intended use. 1. Permanent Restorations 2. Temporary Restorations 3. Intermediary Bases a. Calcium Hydroxide b. Zinc Oxide Eugenol 4. Other Materials a. Varnishes b. Bonding Adhesives c. Bonding Resins 5. Selection of Materials The dentist will consider a number of factors when selecting the material best suited for a particular patient. a. Pulp Considerations b. Esthetics c. Biting Forces d. History of Success
Unit III Dental Materials Structure and Properties To understand the proper use of dental materials, it is important to understand its physical and chemical properties. The mechanical and physical properties of any material depends on its internal structure. There are 3 states of matter: solids, liquids, and gases. Dentistry uses mostly solids. Many were liquids at one point but changed to solids when cooled. A. Solids A solid is a state of matter that occupies a definite volume of space whose shape does not depend on a container. 3. Amorphine Molecules arranged at random are called amorphous, or without form such as a liquid. They are shapeless molecules that are spread at random. It has no pattern and molecules bounce off each other. Flow characteristics cause it to bend. 2. Crystalline If a solid is a state of matter that occupies a definite volume of space whose shape does not depend on a container. It feels hard and unyielding, it is solid. If it is rigid it described as crystalline. Atoms and molecules arranged in a regular pattern in respect to each other is a space lattice. Gold is an example of repeated patterns within a space lattice. Most crystalline materials in dentistry for a cubic type of lattice. Page 16. Atoms in a space lattice maintain their position relative to each other, this is their interatomic distance.
B. Bonding and Adhesion There are two ways of attaching solids together 1. Mechanical Bonding Mechanical bonding in dentistry is when a material penetrates the irregularities of the tooth surface and hardens with projections within the surface irregularities. 2. Adhesion A force that causes unlike molecules to attach to each other. There is no interaction between the molecules of resin and enamel in a restorative situation - they are held by a tenacious bonding. 3. Adhesion and Tooth Structure Conditions that effect adhesion and the tooth structure: 1. The differences between enamel and dentin in composition. 2. Surface imperfections in the prepared cavity. 3. Scratches created by dental instruments. 4. Debris and microscopic moisture (Always present on the tooth surface. This is impossible to remove by dehydration 5. If a low contact angle is formed with the water it is referred to as hydrophilic behavior. G. Cohesion Cohesion is the attraction of like molecules and the strength is governed by the cohesive forces of attraction between the molecules. 1. Primary bonds are chemical bonds known as chemisorption. 2. Secondary bonds are the most common and involve a
physical bonds called the van der Waals forces. 3. Wetting Characteristics For either the chemical or physical adhesion to occur, the adhesive (plaque) and adherend (tooth) must be in intimate contact. This point of contact is called the interface. To achieve this, the adhesive must be liquid and more apt to flow easily over the adherend, this enables it to come in contact with all the surface irregularities and roughnesses. This phenomenon is called wetting. Factors that influence wetting are: High contact angle- undesirable Surface irregularities Low contact angle- desirable Surface energy - it the atoms on the surface are eager to attract other atoms they have high energy and easily bonded too. D. Force, Stress and Strain Force The push and pull on an object and is measured in units of newtons or pounds. This is important in selecting the material to be used. Stress is the reaction with which an object resists external force. Strain is the amount of deformation that occurred to change the shape of the object. The load or external force that produces stress on a
structure also produces strain. strain. Stress cannot exist without 1. Types of Stress and Strain E. Elasticity a. Tensile Stress- Opposes the load and tends to elongate a structure. b. Compressive Stress- Opposed the load and tends to compress the structure. c. Shear Stress- Induced when a structure is twisted, rotated or deformed by sliding one part parallel to another. Elasticity is the ability to elongate under stress then return to its natural shape when the load is removed The elastic limit is the maximum amount of stress without permanent deformation. The ultimate strength or strength is the greatest amount of stress a structure can withstand without rupture. F. Malleability The ability is a metal to withstand permanent deformation under compressive stress without rupture, it spreads out but does not break. G. Ductility The ability of a metal to withstand permanent deformation under tensile stress and does not fracture. H. Flow and Creep 1. Flow
The ability of an object to change shape under compressive strength. 2. Creep I. Toughness The tendency of a material to deform under constant pressure such as amalgam. The property of a material to resist fracture J. Hardness The ability of a material to withstand abrasion and attrition. Materials that are relatively hard are used to replace lost tooth structures. K. Relaxation In time the stress is released to some extent. It depends on temperature increase. Temperature speeds up relaxation and causes distortion a change in the molded shape. 1. Rheology is the science of the study of the flow of liquids. 2. Viscosity is the resistance to stiring. 3. Thixotropic materials are thick upon standing but thin out when stirring. L. Thermal Properties Thermal conductivity is the ability of a material to transmit heat.
Dentures are a poor conductor and prevents heat exchange between soft tissues of the mouth - metal base is better. Burns the soft palate? Crown - the thermal conductivity should be as low as possible from 32F for ice cream to 140F for coffee- these extremes could cause permanent injury or pain. The pulp should be insulated against thermal shock. Tooth structure is an excellent conductor - low thermal conductivity. Metal is a high conductor so a thin layer of dentin will not insulate the pulp well enough. M. Aesthetic or cosmetic dentistry is assuming an ever growing priority. 1. Color is described in terms of three components: a) Hue- Characteristics associated with color b) Chroma- Strength of a particular hue- the higher the chroma the more vivid the color c) Value- Luminance of an object- how bright or dark it is (brightness 2. Shade Guide - color matching uses paint chips most commonly known as the Vita shades. 3. Translucence - the ability of light to show through a material. 4. Metamerism- Selecting a shade under fluorescent light then finding it doesn't match at all ( department store clothing) 5. Fluorescence - Blue-white wavelengths that contributes to the vital appearance of natural teeth.
Unit IV Gypsum Products A. Dental Plaster 1. Physical Properties 2. Uses 3. Care 4. Composition 5. Mixing 6. Setting Time 7. Heat Involvement 8. Strength B. Dental Stone 1. Classes of Stone/Types 2. Uses a. Yellow Stone b. Velmix c. Die Stone 3. Properties 4. Composition 5. Mixing 6. Setting Time
a. Setting Factors b. Setting Influences 7. Heat Involvement 8. Strength C. Infection Control Unit V Aqueous Elastomeric Impression Materials I. Irreversible Hydrocolloids - Alginate A. Uses B. Physical Characteristics C. Types 1. Normal/Regular Set 2. Fast Set 3. Extra Fast Set 4. Chromochon D. Composition 1. Potassium Alginate =15% 2. Calcium Sulfate =16% 3. Trisodium Phosphate =02% 4. Zinc Oxide =04%
5. Diatomaceous Earth =60% 6. Potassium Titanium Fluoride =03% E. Packaging and Storing F. Manipulation G. Mixing - Bowl vs Baggie H. Infection Control/Disinfection I. Common Difficulties II. Reversible Hydrocolloids - Agar agar A. History/Outdated? B. Indications/Use C. Physical Characteristics D. Physical Phases 1. Sol Stage 2. Gel Stage 3. Gel Strength E. Preparation/Storage F. Common Difficulties Unit VI Nonaqueous Elastomeric Impression Materials Elastomers are a soft synthetic rubber, not a gel. An elastomeric solid impression is formed by a chemical reaction between
the various chemicals. The chemical reaction that changes the elastomeric base - called a liquid polymer - into the final rubber-like material, goes through a curing process called polymerization. A. Curing Methods 1. Self Curing 2. Light Cure-Caulk/Genesis A fairly new type of material called polyether urethane dimethacrylate. Light/Heavy Viscosity Light cured materials have some great advantages: standard curing light. Use the A clear plastic tray must be used to light can reach all areas and acts as the catalyst to bring about the curing process. B. General Forms 1. Light Body 2. Medium Body 3. Heavy Body 4. Putty C. Methods of Mixing 1. Single Mix 2. Multiple Mix D. Impression Techniques 1. Two-step
a. Preliminary/Final b. Syringe/Tray c. Extruder 2. All in One 3. Syringe/Extruder Gun E. Infection Control 1. Polyether 2. Polysulfide 3. Addition Silicone F. Pouring Time - Dimensional Stability 1. Polyether 2. Polysulfide/Condensation Silicone 3. Addition Silicone G. Curing Stages 1. Initial Set 2. Final Set 3. Final Cure H. Shelf Life I. Types of Elastomerics
1. Polysulfide a. Characteristics b. Uses c. Consistency/Viscosity d. Mixing Technique e. Controlling the setting time 2. Polyether a. Characteristics b. Uses c. Consistency/Viscosity d. Mixing Technique e. Setting Time 3. Condensation Silicone/Polysiloxane a. Characteristics b. Uses c. Consistency/Viscosity d. Mixing Technique e. Setting Time 4. Addition Silicone/Polyvinyl Siloxane a. Characteristics
b. Uses c. Consistency/Viscosity d. Mixing Technique e. Controlling the Setting Time 5. Polyether Dimethacrylate - Visible Light-cured J. Common Difficulties 1. Rough or uneven surfaces 2. Bubbles 3. Irregular shaped voids 4. Rough chalky casts 5. Distortion L. Clean Up M. Disinfection/Lab prep Unit VIII Waxes and Compounds A. Compounds 1. Indications 2. Uses B. Waxes 3. Composition 4. Techniques 1. General Properties Smooth, shiny, firm yet not rigid in most cases.
2. Thermal Expansion None 3. Cooling Time Very quick but can relax 4. Types and Purposes a. Casting Waxes The fit of the casting depends initially on the accuracy of the wax pattern. The wax lacks rigidity and flows under stress at room temperature. Its structure is a combination of crystalline and amorphous and does not solidify with a definite space lattice like metals. 1) Usually supplied in s sheet of wax 2) Used to cast framework for metallic portion of partials 3) Must be kept at a uniform thickness over the mouth 4) Heat uniformly as in water Wax comes in 3" sticks and is supplied in a variety of colors - blue - green - red Wax has a low thermal conductivity unlike metals (in copper if one end is heated it will get hot at the other end) It should be softened over dry heat, never put in water, the chemicals could be washed out. The exact ingredients are unknown or at least
unpublished, It is as least 40-60 % paraffin. When heating over the open flame, do not heat it so much that it becomes shiny or thin and runny. It can be melted into a metal container and kept in a liquid form, but don't let it smoke when melting 1) Inlay Wax - Type I Medium wax that is used in the direct technique. It had a melting temperature and will flow slightly above 98.6. It is paraffin with other waxes added to proved smoothness, firmness, carvability and toughness Materials added are: Carnauba waxes, to increase the melting range and reduce flow in the mouth. Synthetic waxes such as gum to increase toughness and enhance surface smoothness. 2) Inlay Wax - Type II Soft wax that is used in the indirect method, on study models in a lab. Flow is about 86 and is mostly paraffin. b. Baseplate Wax - Utility Wax c. Aluwax Wax d. Sticky Wax
e. Boxing Wax or Strips f. Boxing Sticks g. Periphery Wax h. Impression Wax i. Block Out Wax j. Preformed Bite Rims k. Wax Bite Strips/Metallic Bite Wafers Unit IX Abrasives and Polishing Agents What are abrasives and polishing agents? The EFDA will intraorally even the margination, finish and polish restorations One form of abrasion constitutes the physical grinding away tooth structure. Diamonds are the most abrasive rotary bur - especially the very coarse grits. Paper discs have various materials impregnated on the surface as a method of carrying the abrasive product Prophy pastes, pumice, cavijets or cavitrons have an abrasive action Factors that affect abrasion: 1. The size of the abrasive particle 2. The pressure exerted against the surface 3. The speed in which the abrasive is moved across the surface. A. Indications
An area that is rough or organic material that has tenaciously attached to the tooth must be removed. Removable appliances that must be cleaned B. Purpose To smooth, polish, shine and remove foreign matter. Abrasive materials should be able to remove excess or intrinsic stain without damage to the tooth or the appliance. C. Technique and Preparation The dentist prepares tooth structure with rotary instruments (the bur) or hand cutting instruments. The dental hygienist cleans, abrades and polishes during the prophylaxis, but removable appliances must be cleaned as well. Unbound particle abrasives and polishing agents can with water to produce a slurry. This slurry is used by: be mixed 1) The hygienist to polish the teeth 2) The hygienist to remove tenacious tartar 3) The assistant to polish dentures, partials, custom trays or guards in the lab 4) The dentist to smooth and refine margination or restorations directly in the mouth of the patient D. Types of Abrasives 1. Emery A natural oxide of aluminum. 2. Aluminum Oxide A pure form of emery. 3. Garnet A number of minerals impregnated on a paper or plastic discs 4. Pumice Abrasive in different grits or particle size. 5. Zirconium Silicate High luster prophy polish
6. Diatomaceous Earth An abrasive for polishing and a filler for other pastes and materials. Also known as kieselguhr (it is mined). 7. Tripoli A mild abrasive action and polishing agent. 8. Rouge Fine red powder composed of iron oxide. 9. Tin Oxide Amalgam polishing agent or putty powder. 10. Sand A form of quartz. 11. Carbides Both silicon carbide and boron carbide. l2. Aluminum Carbide - 13. Diamond Chips are impregnated on burs or discs. 14. Carborundum - E. Polishing Agents - Pastes and Powders The most common materials used in paste, form or impregnated onto discs or into points. Included are: lightening strips, polishing strips, finishing strips, greenie and brownie points, and tooth polishing pastes. The purpose is to provide a material that will smooth rough and uneven surfaces so the pellicle has a harder time attaching to the tooth. The typical paste contains: 1) 20/30 % water for consistency 2) Humectant to retard drying out 3) Detergents to remove stains and deposits 4) Binders to prevents ingredients from separating 5) Coloring and flavoring agents for the feeling of freshness and oral cleanliness. 6) Fluoride to strengthen the tooth and reduce sensitivity of exposed dentin or cementum 7) Crystal growth inhibitors to retard the mineralization of dental plaque and reduce supragingival calculus accretions.
Cervical abrasion data F. Microabrasion Enamel microabrasion is a new concept that has emerged with cosmetic dentistry. It is a technique useful in eliminating the superficial discolorations and textural aberrations in enamel. An 18% slurry of hydrochloric acid in a slurry of pumice is slowly rubbed onto the enamel - both a chemical and abrasive erosion occurs. This is called abrosion. G. Toothbrushes Filaments on toothbrushes are composed mainly of nylon bristles whose tips lie on a flat plane and may be multitufted or end-rounded. The brushes are graded hard, medium, soft and refers to the stiffness of the bristles not the hardness of the nylon. The stiffness is controlled by the size of the bristle, the larger the bristle the stiffer the brush. Softer brushes are best suited due to the nature of the human animal and the effects of cervical abrasion on tooth structure. H. Mediums/Methods of Placement 1. Paper Discs 2. Strips 3. Stones 4. Silicone Points 5. Pastes Unit X Metal Products XIV. Indirect Metals - Gold A. Advantages B. Disadvantages
C. Composition D. Properties II. Direct Technique E. Types of Gold 1. Cohesive 2. Noncohesive F. Classifications of Gold and Casting Metals 1. Class I 2. Class II 3. Class III 4. Class IV G. Gold for Direct Restorations 1. Foil 2. Mat 3. Powder 4. Placement 5. Technique a. Annealing 6. Condensation
7. Finish a. Pneumatic b. Automatic c. Mallet\Condenser 8. Prognosis H. Functions of the Commercial Dental Laboratory 1. Steps in Crown and Bridge Construction 2. Principles of Preparing Cases for the Commercial Dental Laboratory a. Recording b. Controlling Case Load c. Checking Rx Completeness d. Disinfection/Packaging G:\groups\ahteam\dent\DM1-Student Outline 11-12