Alginate is an irreversible hydrocolloid impression material made from seaweed. It consists of gelatin particles suspended in water. When the powder and water are mixed, it forms a sol that transitions to a gel through a chemical reaction where soluble alginate reacts with calcium sulfate to form insoluble calcium alginate. This reaction is delayed by adding trisodium phosphate. Alginate has adequate working and setting times and is used for impressions where there are undercuts or excess saliva. It provides detailed impressions but is prone to dimensional changes with moisture changes.
The document discusses agar and alginate as hydrocolloid impression materials. It provides details on their composition, uses, types, preparation and properties. Agar is extracted from seaweed and forms a gel when cooled. It is used for full arch impressions and duplications. Alginate forms a gel through a chemical reaction with calcium sulfate. It is commonly used for complete dentures and orthodontic impressions due to its fast setting time. Both materials provide accurate impressions but alginate is more popular due to being easier to use.
Elastic impression materials include alginate, elastomers like polysulfides and polyethers, and addition and condensation silicone materials. They are capable of accurately reproducing both hard and soft oral structures. Elastic materials are advantageous over rigid materials for use in cases with undercuts. Elastic materials are classified as reversible or irreversible hydrocolloids and elastomeric materials. Agar is a reversible hydrocolloid extracted from seaweed that forms gels through secondary bonds that break and re-form with temperature changes. It requires specialized equipment and techniques for manipulation but provides accurate impressions.
This document discusses different types of dental waxes, including their definitions, classifications, components, properties and uses. The main types covered are modelling wax, inlay wax, casting wax, boxing wax and sticky wax. For each type, the document outlines their composition, melting range, properties and intended uses. Thermal properties like solid-solid transition temperature, coefficient of thermal expansion and melting range are discussed for dental waxes in general.
This document discusses hydrocolloids, which are gelatin particles suspended in water. There are two main types used for dental impressions: agar and alginate. Agar is a polysaccharide extracted from seaweed that is widely used for cast duplication. It can be reused but has low tear strength. Alginate is derived from seaweed and sets via a chemical reaction between soluble alginate and calcium sulfate to form insoluble calcium alginate. Alginate makes accurate impressions but cannot be reused or corrected. Both materials are inexpensive and easy to use but have limitations such as dimensional instability and low strength.
This document provides information about zinc oxide eugenol cement. It discusses the objectives, availability, types, composition, setting reaction, properties, and manipulation of zinc oxide eugenol cement. The key points are:
- Zinc oxide eugenol cement has been used since 1890 and is biocompatible but has low strength. It is available in bottles, tubes, and as paste/paste systems.
- It has various applications including temporary cementation, temporary fillings, cavity liners, and pulp capping. Types include those for temporary cementation, permanent cementation, temporary fillings, and cavity liners.
- Its composition involves a powder containing zinc oxide and a liquid containing e
PHYSICAL PROPERTIES OF DENTAL MATERIALSAswati Soman
The document discusses various physical properties of dental materials, including rheological, thermal, electrical, chemical, and optical properties. It describes properties such as viscosity, viscoelasticity, thermal conductivity, color, and fluorescence. Viscosity is defined as the resistance of a fluid to flow and is important for materials used in dentistry. The document also discusses various mechanical models that can be used to characterize the viscous and elastic behaviors of different materials. Thermal properties like conductivity are important because materials in the oral cavity are exposed to temperature changes. Optical properties such as color, transparency, and fluorescence also impact how materials appear in the mouth.
This document provides an overview of dental cements. It begins with definitions of dental cements and discusses their history. It describes ideal cement properties and classifications including based on ingredients/application, bonding mechanism, and setting reaction. Specific cement types are then outlined - silicate, zinc phosphate, zinc polycarboxylate, zinc oxide eugenol, calcium hydroxide, and their compositions, reactions, properties and uses. The document provides a detailed comparison of zinc phosphate and zinc polycarboxylate cements. In summary, it is a comprehensive review of different dental cement types, their characteristics and applications.
Glass-ionomer cement is used for various dental applications including final cementation, cavity bases, esthetic fillings, and orthodontic bracket cementation. It consists of a powder made of calcium-fluoro-alumino-silicate glass and a liquid containing polyacrylic acid. The acid-base setting reaction involves the glass dissolving in acid to release ions that crosslink the polyacrylic acid chains. Modifications include resin-modified glass-ionomer cement which incorporates resin monomers to form a protective matrix during the acid-base setting reaction.
The document discusses agar and alginate as hydrocolloid impression materials. It provides details on their composition, uses, types, preparation and properties. Agar is extracted from seaweed and forms a gel when cooled. It is used for full arch impressions and duplications. Alginate forms a gel through a chemical reaction with calcium sulfate. It is commonly used for complete dentures and orthodontic impressions due to its fast setting time. Both materials provide accurate impressions but alginate is more popular due to being easier to use.
Elastic impression materials include alginate, elastomers like polysulfides and polyethers, and addition and condensation silicone materials. They are capable of accurately reproducing both hard and soft oral structures. Elastic materials are advantageous over rigid materials for use in cases with undercuts. Elastic materials are classified as reversible or irreversible hydrocolloids and elastomeric materials. Agar is a reversible hydrocolloid extracted from seaweed that forms gels through secondary bonds that break and re-form with temperature changes. It requires specialized equipment and techniques for manipulation but provides accurate impressions.
This document discusses different types of dental waxes, including their definitions, classifications, components, properties and uses. The main types covered are modelling wax, inlay wax, casting wax, boxing wax and sticky wax. For each type, the document outlines their composition, melting range, properties and intended uses. Thermal properties like solid-solid transition temperature, coefficient of thermal expansion and melting range are discussed for dental waxes in general.
This document discusses hydrocolloids, which are gelatin particles suspended in water. There are two main types used for dental impressions: agar and alginate. Agar is a polysaccharide extracted from seaweed that is widely used for cast duplication. It can be reused but has low tear strength. Alginate is derived from seaweed and sets via a chemical reaction between soluble alginate and calcium sulfate to form insoluble calcium alginate. Alginate makes accurate impressions but cannot be reused or corrected. Both materials are inexpensive and easy to use but have limitations such as dimensional instability and low strength.
This document provides information about zinc oxide eugenol cement. It discusses the objectives, availability, types, composition, setting reaction, properties, and manipulation of zinc oxide eugenol cement. The key points are:
- Zinc oxide eugenol cement has been used since 1890 and is biocompatible but has low strength. It is available in bottles, tubes, and as paste/paste systems.
- It has various applications including temporary cementation, temporary fillings, cavity liners, and pulp capping. Types include those for temporary cementation, permanent cementation, temporary fillings, and cavity liners.
- Its composition involves a powder containing zinc oxide and a liquid containing e
PHYSICAL PROPERTIES OF DENTAL MATERIALSAswati Soman
The document discusses various physical properties of dental materials, including rheological, thermal, electrical, chemical, and optical properties. It describes properties such as viscosity, viscoelasticity, thermal conductivity, color, and fluorescence. Viscosity is defined as the resistance of a fluid to flow and is important for materials used in dentistry. The document also discusses various mechanical models that can be used to characterize the viscous and elastic behaviors of different materials. Thermal properties like conductivity are important because materials in the oral cavity are exposed to temperature changes. Optical properties such as color, transparency, and fluorescence also impact how materials appear in the mouth.
This document provides an overview of dental cements. It begins with definitions of dental cements and discusses their history. It describes ideal cement properties and classifications including based on ingredients/application, bonding mechanism, and setting reaction. Specific cement types are then outlined - silicate, zinc phosphate, zinc polycarboxylate, zinc oxide eugenol, calcium hydroxide, and their compositions, reactions, properties and uses. The document provides a detailed comparison of zinc phosphate and zinc polycarboxylate cements. In summary, it is a comprehensive review of different dental cement types, their characteristics and applications.
Glass-ionomer cement is used for various dental applications including final cementation, cavity bases, esthetic fillings, and orthodontic bracket cementation. It consists of a powder made of calcium-fluoro-alumino-silicate glass and a liquid containing polyacrylic acid. The acid-base setting reaction involves the glass dissolving in acid to release ions that crosslink the polyacrylic acid chains. Modifications include resin-modified glass-ionomer cement which incorporates resin monomers to form a protective matrix during the acid-base setting reaction.
Silicone impression materials were developed in 1954 as an alternative to polysulfide materials. They polymerize by an addition reaction and are available in various consistencies from heavy to light. Silicone impressions are hydrophobic but hydrophilic varieties were later introduced. They are accurate, dimensionally stable, and resistant to disinfection but are more expensive than other elastomers. Common brands of addition-cure silicone materials include Permalastic, Co-Flex, Affinis Micro, Affinis Putty, and President Putty.
Dental amalgam is an alloy used as a dental restorative material. It consists of mercury combined with other metals like silver, tin, and copper. Amalgam undergoes a setting reaction when mixed with liquid mercury to form a hard material. It is indicated for restoring cavities. While it has advantages like strength and cost-effectiveness, it lacks esthetics and can release low levels of mercury vapor. Modern amalgams have improved properties like reduced creep and shrinkage. Careful manipulation is required to achieve optimal physical properties and reduce risks.
This document discusses gypsum products used in dentistry. It describes the production of gypsum by calcining gypsum rock or synthetic methods. There are 5 types of gypsum products defined by the American Dental Association based on their properties and uses. The document outlines the setting reactions of gypsum when mixed with water and factors that influence the setting time such as temperature, water-powder ratio, and fineness of particles. It also discusses tests used to measure initial and final setting times of gypsum.
Non-elastic impression materials like impression compound and zinc oxide eugenol set via physical or chemical reactions and cannot record undercuts due to fracturing upon removal. Elastic impression materials like hydrocolloids (alginate and agar) and elastomers set viscoelastically, allowing compression in undercuts and subsequent recovery to accurately record details. Hydrocolloids exist as sols that gel upon temperature change via physical (agar) or chemical (alginate) reactions. They have high flow, flexibility, and compatibility with gypsum but shrink and are dimensionally unstable when dry.
This document discusses denture base materials, specifically acrylic resins. It begins by defining denture base and classifying denture base resins as non-metallic, metallic, temporary or permanent. Ideal requirements of dental resins are listed. Composition and differences between heat cure and self cure acrylic resins are provided. Processing techniques like compression molding and the curing cycle are described. Other resin types like light activated are also mentioned. Common processing errors in acrylic resins like porosity, crazing and warpage are listed.
Calcium hydroxide cements were introduced by Hermann in 1920 as an alternative to viewing exposed pulps as "doomed organs." Calcium hydroxide cements promote healing in clinical situations by creating an alkaline environment. They are formed through a reaction of calcium oxide with water to create calcium hydroxide. Typical calcium hydroxide cements are composed of calcium hydroxide, zinc oxide, zinc stearate, and ethyl toluene sulphonamide. They set through exothermic chemical reactions, have biocompatibility that can destroy bacteria and initiate reparative dentin formation, but have low strength and solubility in moisture.
This document provides an overview of the physical properties of dental materials. It discusses topics like the structure of matter, interatomic bonds, adhesion and bonding, concepts of stress and strain, and rheology. The document is intended to explain the underlying physics and chemistry that determine the mechanical, thermal, optical and other observable qualities of dental materials. It focuses on topics like crystalline structure, bonding forces, surface energy, wetting, and how stresses and strains impact materials at the atomic level. The overall aim is to describe the fundamental physical principles that govern the behavior and performance of different dental materials.
This document provides an overview of biocompatibility as it relates to dental materials. It defines biocompatibility and discusses the requirements dental materials must meet to be biocompatible. The document outlines various tests used to evaluate biocompatibility, including toxicity, inflammation, allergic reactions, and other potential adverse effects. It also discusses the relevance of biocompatibility to dentists and their patients and staff. Finally, it examines how biocompatibility of dental materials is measured through a series of in vivo and in vitro tests.
Zinc oxide eugenol impression paste sets via an irreversible chemical reaction between zinc oxide and eugenol to form zinc eugenolate. It has good detail reproduction and dimensional stability but can cause a burning sensation. It is mixed in equal volumes of zinc oxide paste and eugenol paste on a mixing slab until uniformly colored, and has a working time of about 1 minute before initial set. Variations include slower-setting surgical pastes and non-eugenol pastes that avoid the burning sensation.
Investment materials are used to form molds for dental casting. They are composed of refractory materials like quartz or cristobalite, a binder like gypsum or phosphate, and other chemicals. Gypsum-bonded investments are commonly used for gold alloy casting while phosphate-bonded investments can withstand higher temperatures for casting alloys like cobalt-chromium. Ethyl silicate investments are used for high-fusing base metal alloys. The investments require properties like stability at high temperatures, sufficient expansion to compensate for metal shrinkage, and ease of removal after casting.
This document provides an overview of dental amalgam, including its history, composition, manufacturing process, properties, and clinical use. Dental amalgam is an alloy made by mixing mercury with a silver-tin alloy. It has been used as a dental restorative material since the 1800s. The document discusses the various types of amalgam alloys, the chemical reactions involved in amalgam setting, and how properties like strength and creep vary between low-copper and high-copper amalgam formulations. It also outlines the indications and contraindications for using dental amalgam.
Biocompatibility of dental materials- kellyKelly Norton
The document discusses the biocompatibility of dental materials. It defines biocompatibility as the ability of a material to elicit an appropriate biological response. A number of factors determine the biocompatibility of a dental material, including its ability to avoid toxicity, immunotoxicity, allergic reactions, and other adverse effects. A variety of in vitro, animal, and human tests are used to measure the biocompatibility of dental materials before clinical use.
This document discusses elastic hydrocolloid impression materials, specifically agar and alginate. It provides details on their composition, setting reactions, properties and applications. Agar is a reversible hydrocolloid used for secondary impressions that sets physically through a sol-gel transition upon cooling. Alginate is an irreversible hydrocolloid used for primary impressions that sets chemically through a gelation reaction involving calcium ions. Both materials are hydrophilic and require immediate pouring to minimize dimensional changes from imbibition, synersis or dehydration.
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive functioning. Exercise causes chemical changes in the brain that may help protect against mental illness and improve symptoms.
Zinc phosphate cement is an older luting cement that serves as a standard for comparison. It has low hardness and high solubility. When mixed, the powder and liquid undergo an exothermic reaction where zinc ions are released and react with aluminum and phosphoric acid to form a zinc aluminophosphate gel. It has good compressive strength but no chemical adhesion and can cause pulp irritation due to its initial low pH. The powder contains mainly zinc oxide and magnesium oxide while the liquid contains phosphoric acid, water, and aluminum.
This document provides an overview of various types of dental cements. It begins with definitions and a brief history of dental cements. It then classifies cements based on their ingredients and discusses their ideal requirements. The document goes on to describe specific cement types in detail, including their characteristics, properties, and uses. It covers traditional cements like zinc phosphate, as well as contemporary materials like resin-modified glass ionomers. The document provides a comprehensive reference on the formulation and application of different dental cements.
The document discusses heat cure acrylic denture base resins. It provides background on the development of denture base materials over time. Polymethyl methacrylate (PMMA) was introduced in 1937 and remains the material of choice due to its superior esthetics, ease of processing, accurate fit, and use with inexpensive equipment. The document describes the composition, chemical basis of polymerization, manipulation techniques including compression molding and injection molding, and physical properties of heat cure acrylic resins. It also compares heat cure resins to self-cure resins and discusses requirements versus clinical performance as well as recent advances in the material.
This document provides an overview of different types of dental cements, including their composition, properties, and applications. It discusses zinc phosphate cement, the oldest cement still in use today. It also covers silicate cement, one of the first direct tooth-colored materials; zinc polycarboxylate cement, the first cement with adhesive properties; and zinc oxide eugenol cement, commonly used as a temporary cement. Modified versions of these traditional cements are also presented, along with other contemporary cements like glass ionomer cement and resin cements.
Alginate is a commonly used irreversible hydrocolloid impression material that is supplied as a powder. It is mixed with water to form a paste that sets into a gel via a chemical reaction between the sodium alginate and calcium sulfate. Alginate sets quickly and is flexible, making it suitable for dental impressions. However, it lacks dimensional stability and cannot be reused, so casts must be poured immediately after the impression is taken.
This document provides information on alginate impression material. It defines alginate as an irreversible hydrocolloid impression material made from seaweed. It discusses the composition, setting reaction, and physical phases of alginate. The document also outlines the manipulation, application, advantages and disadvantages of alginate impression material.
ALGINATE IMPRESSION MATERIAL-Dr MEENU MERRY C PAULMeenuMerryCPaul
Alginate is the most commonly used irreversible hydrocolloid impression material. It sets via a chemical reaction when the potassium alginate and calcium sulfate powders are mixed with water. Alginate has good accuracy but is dimensionally unstable if allowed to dry out or absorb water. It is inexpensive, easy to use, and well-tolerated by patients. An alginate impression should capture detailed anatomy and full extension to produce an acceptable gypsum cast.
Silicone impression materials were developed in 1954 as an alternative to polysulfide materials. They polymerize by an addition reaction and are available in various consistencies from heavy to light. Silicone impressions are hydrophobic but hydrophilic varieties were later introduced. They are accurate, dimensionally stable, and resistant to disinfection but are more expensive than other elastomers. Common brands of addition-cure silicone materials include Permalastic, Co-Flex, Affinis Micro, Affinis Putty, and President Putty.
Dental amalgam is an alloy used as a dental restorative material. It consists of mercury combined with other metals like silver, tin, and copper. Amalgam undergoes a setting reaction when mixed with liquid mercury to form a hard material. It is indicated for restoring cavities. While it has advantages like strength and cost-effectiveness, it lacks esthetics and can release low levels of mercury vapor. Modern amalgams have improved properties like reduced creep and shrinkage. Careful manipulation is required to achieve optimal physical properties and reduce risks.
This document discusses gypsum products used in dentistry. It describes the production of gypsum by calcining gypsum rock or synthetic methods. There are 5 types of gypsum products defined by the American Dental Association based on their properties and uses. The document outlines the setting reactions of gypsum when mixed with water and factors that influence the setting time such as temperature, water-powder ratio, and fineness of particles. It also discusses tests used to measure initial and final setting times of gypsum.
Non-elastic impression materials like impression compound and zinc oxide eugenol set via physical or chemical reactions and cannot record undercuts due to fracturing upon removal. Elastic impression materials like hydrocolloids (alginate and agar) and elastomers set viscoelastically, allowing compression in undercuts and subsequent recovery to accurately record details. Hydrocolloids exist as sols that gel upon temperature change via physical (agar) or chemical (alginate) reactions. They have high flow, flexibility, and compatibility with gypsum but shrink and are dimensionally unstable when dry.
This document discusses denture base materials, specifically acrylic resins. It begins by defining denture base and classifying denture base resins as non-metallic, metallic, temporary or permanent. Ideal requirements of dental resins are listed. Composition and differences between heat cure and self cure acrylic resins are provided. Processing techniques like compression molding and the curing cycle are described. Other resin types like light activated are also mentioned. Common processing errors in acrylic resins like porosity, crazing and warpage are listed.
Calcium hydroxide cements were introduced by Hermann in 1920 as an alternative to viewing exposed pulps as "doomed organs." Calcium hydroxide cements promote healing in clinical situations by creating an alkaline environment. They are formed through a reaction of calcium oxide with water to create calcium hydroxide. Typical calcium hydroxide cements are composed of calcium hydroxide, zinc oxide, zinc stearate, and ethyl toluene sulphonamide. They set through exothermic chemical reactions, have biocompatibility that can destroy bacteria and initiate reparative dentin formation, but have low strength and solubility in moisture.
This document provides an overview of the physical properties of dental materials. It discusses topics like the structure of matter, interatomic bonds, adhesion and bonding, concepts of stress and strain, and rheology. The document is intended to explain the underlying physics and chemistry that determine the mechanical, thermal, optical and other observable qualities of dental materials. It focuses on topics like crystalline structure, bonding forces, surface energy, wetting, and how stresses and strains impact materials at the atomic level. The overall aim is to describe the fundamental physical principles that govern the behavior and performance of different dental materials.
This document provides an overview of biocompatibility as it relates to dental materials. It defines biocompatibility and discusses the requirements dental materials must meet to be biocompatible. The document outlines various tests used to evaluate biocompatibility, including toxicity, inflammation, allergic reactions, and other potential adverse effects. It also discusses the relevance of biocompatibility to dentists and their patients and staff. Finally, it examines how biocompatibility of dental materials is measured through a series of in vivo and in vitro tests.
Zinc oxide eugenol impression paste sets via an irreversible chemical reaction between zinc oxide and eugenol to form zinc eugenolate. It has good detail reproduction and dimensional stability but can cause a burning sensation. It is mixed in equal volumes of zinc oxide paste and eugenol paste on a mixing slab until uniformly colored, and has a working time of about 1 minute before initial set. Variations include slower-setting surgical pastes and non-eugenol pastes that avoid the burning sensation.
Investment materials are used to form molds for dental casting. They are composed of refractory materials like quartz or cristobalite, a binder like gypsum or phosphate, and other chemicals. Gypsum-bonded investments are commonly used for gold alloy casting while phosphate-bonded investments can withstand higher temperatures for casting alloys like cobalt-chromium. Ethyl silicate investments are used for high-fusing base metal alloys. The investments require properties like stability at high temperatures, sufficient expansion to compensate for metal shrinkage, and ease of removal after casting.
This document provides an overview of dental amalgam, including its history, composition, manufacturing process, properties, and clinical use. Dental amalgam is an alloy made by mixing mercury with a silver-tin alloy. It has been used as a dental restorative material since the 1800s. The document discusses the various types of amalgam alloys, the chemical reactions involved in amalgam setting, and how properties like strength and creep vary between low-copper and high-copper amalgam formulations. It also outlines the indications and contraindications for using dental amalgam.
Biocompatibility of dental materials- kellyKelly Norton
The document discusses the biocompatibility of dental materials. It defines biocompatibility as the ability of a material to elicit an appropriate biological response. A number of factors determine the biocompatibility of a dental material, including its ability to avoid toxicity, immunotoxicity, allergic reactions, and other adverse effects. A variety of in vitro, animal, and human tests are used to measure the biocompatibility of dental materials before clinical use.
This document discusses elastic hydrocolloid impression materials, specifically agar and alginate. It provides details on their composition, setting reactions, properties and applications. Agar is a reversible hydrocolloid used for secondary impressions that sets physically through a sol-gel transition upon cooling. Alginate is an irreversible hydrocolloid used for primary impressions that sets chemically through a gelation reaction involving calcium ions. Both materials are hydrophilic and require immediate pouring to minimize dimensional changes from imbibition, synersis or dehydration.
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive functioning. Exercise causes chemical changes in the brain that may help protect against mental illness and improve symptoms.
Zinc phosphate cement is an older luting cement that serves as a standard for comparison. It has low hardness and high solubility. When mixed, the powder and liquid undergo an exothermic reaction where zinc ions are released and react with aluminum and phosphoric acid to form a zinc aluminophosphate gel. It has good compressive strength but no chemical adhesion and can cause pulp irritation due to its initial low pH. The powder contains mainly zinc oxide and magnesium oxide while the liquid contains phosphoric acid, water, and aluminum.
This document provides an overview of various types of dental cements. It begins with definitions and a brief history of dental cements. It then classifies cements based on their ingredients and discusses their ideal requirements. The document goes on to describe specific cement types in detail, including their characteristics, properties, and uses. It covers traditional cements like zinc phosphate, as well as contemporary materials like resin-modified glass ionomers. The document provides a comprehensive reference on the formulation and application of different dental cements.
The document discusses heat cure acrylic denture base resins. It provides background on the development of denture base materials over time. Polymethyl methacrylate (PMMA) was introduced in 1937 and remains the material of choice due to its superior esthetics, ease of processing, accurate fit, and use with inexpensive equipment. The document describes the composition, chemical basis of polymerization, manipulation techniques including compression molding and injection molding, and physical properties of heat cure acrylic resins. It also compares heat cure resins to self-cure resins and discusses requirements versus clinical performance as well as recent advances in the material.
This document provides an overview of different types of dental cements, including their composition, properties, and applications. It discusses zinc phosphate cement, the oldest cement still in use today. It also covers silicate cement, one of the first direct tooth-colored materials; zinc polycarboxylate cement, the first cement with adhesive properties; and zinc oxide eugenol cement, commonly used as a temporary cement. Modified versions of these traditional cements are also presented, along with other contemporary cements like glass ionomer cement and resin cements.
Alginate is a commonly used irreversible hydrocolloid impression material that is supplied as a powder. It is mixed with water to form a paste that sets into a gel via a chemical reaction between the sodium alginate and calcium sulfate. Alginate sets quickly and is flexible, making it suitable for dental impressions. However, it lacks dimensional stability and cannot be reused, so casts must be poured immediately after the impression is taken.
This document provides information on alginate impression material. It defines alginate as an irreversible hydrocolloid impression material made from seaweed. It discusses the composition, setting reaction, and physical phases of alginate. The document also outlines the manipulation, application, advantages and disadvantages of alginate impression material.
ALGINATE IMPRESSION MATERIAL-Dr MEENU MERRY C PAULMeenuMerryCPaul
Alginate is the most commonly used irreversible hydrocolloid impression material. It sets via a chemical reaction when the potassium alginate and calcium sulfate powders are mixed with water. Alginate has good accuracy but is dimensionally unstable if allowed to dry out or absorb water. It is inexpensive, easy to use, and well-tolerated by patients. An alginate impression should capture detailed anatomy and full extension to produce an acceptable gypsum cast.
The document provides information on irreversible hydrocolloids, specifically alginate impression materials. It discusses the classification, ideal requirements, and history of alginate. The composition of alginate includes sodium alginate, calcium sulfate, and other ingredients. Alginate sets via a sol-gel reaction as calcium ions crosslink the sodium alginate chains. Properties like working time and setting time are controlled by factors like water temperature. Dimensional changes can occur due to syneresis, imbibition or evaporation. Methods to avoid changes include quick pouring and storage in a humid environment. Strength depends on proper spatulation during mixing.
This document discusses the properties and chemistry of alginate impression materials. Alginate sets via a chemical reaction between sodium alginate and calcium sulfate to form insoluble calcium alginate. Additives like retarders and fillers are included to control consistency and setting time. Proper control of water:powder ratio, mixing time, and water temperature is needed to achieve optimal gelation time and avoid distortion of the impression. Alginate is a commonly used irreversible hydrocolloid impression material.
This document summarizes a seminar presentation on spherification in molecular gastronomy. Spherification is a technique introduced by Ferran Adria in 2003 to turn liquids into spheres using sodium alginate and calcium chloride. The presentation defines molecular gastronomy and discusses the basic chemistry behind spherification reactions. It also describes different spherification methods, factors that affect the process, equipment used like a spherificator, applications, examples like strawberry caviar, and the future scope of spherification.
Alginate is a commonly used impression material that is extracted from brown seaweed. It sets via a chemical reaction when its powder form is mixed with water. The powder contains soluble sodium alginate which reacts with calcium sulfate in the powder to form insoluble calcium alginate. Sodium phosphate is also included as a retarder to increase working time before the reaction occurs. Alginate has advantages of being easy to use, inexpensive, and comfortable for patients. However, it has disadvantages like poor dimensional stability, strength, and accuracy for complex impressions.
Alginate is an irreversible hydrocolloid commonly used for dental impressions. It exists as a sol or gel, changing from a flowable sol to a solid gel state when an adequate concentration of dispersed particles is achieved. Alginate is supplied as a powder mixed with water. It sets via a calcium sulfate and sodium phosphate reaction to form an insoluble calcium alginate gel. Various studies have evaluated the effectiveness of disinfecting alginate impressions to reduce microorganisms, as well as the impact of disinfection on dimensional stability. Recent advances include dust-free, high viscosity, and color changing alginate formulations.
Elastic impression materials like alginate and agar are able to reproduce undercuts accurately due to their elasticity. Alginate is an irreversible hydrocolloid that sets via a chemical reaction between soluble alginate and calcium sulfate. It forms a brush heap gel structure and has adequate strength and accuracy for dental impressions. Agar is a reversible hydrocolloid that transitions between sol and gel states based on temperature. Both require special equipment for manipulation but provide elastic impressions suitable for edentulous and dentulous arches.
This document provides information on irreversible hydrocolloid (alginate) impression materials. It discusses the composition, properties, manipulation and applications of alginate. The main points are:
- Alginate sets via a chemical reaction between sodium alginate and calcium sulfate to form calcium alginate gel. Retarders are added to provide adequate working time.
- It is used for impressions requiring detail in areas with undercuts or excess saliva. Alginate has adequate flexibility, elasticity and strength for preliminary impressions.
- Proper mixing, tray selection and technique are required as alginate has poor adhesion and dimensional stability. The impression must be removed quickly once set.
Effervescent tablets are uncoated tablets that generally contain acid substances and carbonates or bicarbonates, and that react rapidly in the presence of water by releasing carbon dioxide.
This document provides an overview of dental impression materials. It begins with a brief history of dental impressions and then discusses the ideal requirements and classifications of impression materials. The main types discussed are hydrocolloids like alginate and agar, as well as elastomeric materials like polysulfides, silicones, and polyethers. For each material, the document outlines their composition, setting reaction, properties, manipulation, and advantages/limitations. Causes for impression failure and alternative impression methods like oral scanners are also mentioned before concluding with references.
This document discusses impression materials used in dentistry. It defines impression materials as those that accurately record oral tissues to create a negative reproduction called an impression, from which a positive model or cast is made. It classifies impression materials based on use (single tooth, partial denture, complete denture) and setting behavior (elastic vs non-elastic). Specific hydrocolloid materials discussed include alginate and agar. Alginate sets via a chemical reaction with calcium ions to form a gel, while agar sets reversibly based on temperature. Both require proper manipulation to ensure accurate impressions.
This document provides information about hydrocolloids used for dental impressions. It discusses the history of impression materials, ideal requirements, classification systems, and specific hydrocolloids - alginate and agar. Alginate is an irreversible hydrocolloid that sets via a chemical reaction with calcium ions. It is easy to use but has low accuracy and dimensional stability. Agar is a reversible hydrocolloid that changes between sol and gel states with temperature changes, but it has been replaced by other materials. The document provides details on the composition, setting reactions, properties and uses of these hydrocolloid impression materials.
The document discusses dental impression materials. It provides details on the classification, composition, properties, manipulation and applications of various impression materials including alginate, agar, impression compound, zinc oxide eugenol and silicone impressions materials. Impression materials are classified based on their setting mechanism and elasticity into rigid or elastic materials that set via a chemical reaction or temperature change. The document describes the key ingredients, setting reactions, advantages and disadvantages of different impression materials.
The document discusses dental impression materials. It provides details on the classification, composition, properties, manipulation and applications of various impression materials including alginate, agar, impression compound, zinc oxide eugenol and silicone impressions materials. Impression materials are classified based on their setting mechanism and elasticity into rigid or elastic materials that set via a chemical reaction or temperature change. The document outlines the characteristics required of impression materials and provides formulations and setting reactions for several common materials.
The document discusses elastic impression materials, specifically focusing on hydrocolloids like agar and alginate. It defines hydrocolloids as colloids containing water as the dispersion phase. Agar is derived from seaweed and forms reversible hydrocolloid impressions using a sol-gel transition dependent on temperature. Alginate is derived from seaweed as well and forms irreversible hydrocolloid impressions through a chemical reaction between sodium alginate and calcium sulfate. The document reviews the history, composition, manipulation and properties of these hydrocolloid impression materials.
This document discusses impression materials used in dentistry. It defines impression materials as those that accurately record oral tissues to create a negative reproduction called an impression, from which a positive model is made. It classifies impression materials based on use (single tooth, partial denture, complete denture) and setting behavior (elastic vs non-elastic). Specific hydrocolloid materials discussed include agar and alginate. Agar and alginate compositions, manipulations, properties, and applications are summarized.
Hydrocolloids /certified fixed orthodontic courses by Indian dental academy Indian dental academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.
Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078
The document discusses elastic impression materials, specifically hydrocolloids like agar and alginate. It provides details on their composition, properties, uses and advantages/disadvantages. Agar is extracted from seaweed and sets via chemical reaction. Alginate is also derived from seaweed and sets via reaction with calcium sulfate. Both materials are inexpensive, easy to use and comfortable for patients, though they lack the accuracy of elastomers for crown and bridge work.
Emotional and Behavioural Problems in Children - Counselling and Family Thera...PsychoTech Services
A proprietary approach developed by bringing together the best of learning theories from Psychology, design principles from the world of visualization, and pedagogical methods from over a decade of training experience, that enables you to: Learn better, faster!
Joker Wigs has been a one-stop-shop for hair products for over 26 years. We provide high-quality hair wigs, hair extensions, hair toppers, hair patch, and more for both men and women.
Hypertension and it's role of physiotherapy in it.Vishal kr Thakur
This particular slides consist of- what is hypertension,what are it's causes and it's effect on body, risk factors, symptoms,complications, diagnosis and role of physiotherapy in it.
This slide is very helpful for physiotherapy students and also for other medical and healthcare students.
Here is summary of hypertension -
Hypertension, also known as high blood pressure, is a serious medical condition that occurs when blood pressure in the body's arteries is consistently too high. Blood pressure is the force of blood pushing against the walls of blood vessels as the heart pumps it. Hypertension can increase the risk of heart disease, brain disease, kidney disease, and premature death.
R3 Stem Cell Therapy: A New Hope for Women with Ovarian FailureR3 Stem Cell
Discover the groundbreaking advancements in stem cell therapy by R3 Stem Cell, offering new hope for women with ovarian failure. This innovative treatment aims to restore ovarian function, improve fertility, and enhance overall well-being, revolutionizing reproductive health for women worldwide.
Mental Health and well-being Presentation. Exploring innovative approaches and strategies for enhancing mental well-being. Discover cutting-edge research, effective strategies, and practical methods for fostering mental well-being.
CHAPTER 1 SEMESTER V COMMUNICATION TECHNIQUES FOR CHILDREN.pdfSachin Sharma
Here are some key objectives of communication with children:
Build Trust and Security:
Establish a safe and supportive environment where children feel comfortable expressing themselves.
Encourage Expression:
Enable children to articulate their thoughts, feelings, and experiences.
Promote Emotional Understanding:
Help children identify and understand their own emotions and the emotions of others.
Enhance Listening Skills:
Develop children’s ability to listen attentively and respond appropriately.
Foster Positive Relationships:
Strengthen the bond between children and caregivers, peers, and other adults.
Support Learning and Development:
Aid cognitive and language development through engaging and meaningful conversations.
Teach Social Skills:
Encourage polite, respectful, and empathetic interactions with others.
Resolve Conflicts:
Provide tools and guidance for children to handle disagreements constructively.
Encourage Independence:
Support children in making decisions and solving problems on their own.
Provide Reassurance and Comfort:
Offer comfort and understanding during times of distress or uncertainty.
Reinforce Positive Behavior:
Acknowledge and encourage positive actions and behaviors.
Guide and Educate:
Offer clear instructions and explanations to help children understand expectations and learn new concepts.
By focusing on these objectives, communication with children can be both effective and nurturing, supporting their overall growth and well-being.
Get Covid Testing at Fit to Fly PCR TestNX Healthcare
A Fit-to-Fly PCR Test is a crucial service for travelers needing to meet the entry requirements of various countries or airlines. This test involves a polymerase chain reaction (PCR) test for COVID-19, which is considered the gold standard for detecting active infections. At our travel clinic in Leeds, we offer fast and reliable Fit to Fly PCR testing, providing you with an official certificate verifying your negative COVID-19 status. Our process is designed for convenience and accuracy, with quick turnaround times to ensure you receive your results and certificate in time for your departure. Trust our professional and experienced medical team to help you travel safely and compliantly, giving you peace of mind for your journey.www.nxhealthcare.co.uk
Digital Health in India_Health Informatics Trained Manpower _DrDevTaneja_15.0...DrDevTaneja1
Digital India will need a big trained army of Health Informatics educated & trained manpower in India.
Presently, generalist IT manpower does most of the work in the healthcare industry in India. Academic Health Informatics education is not readily available at school & health university level or IT education institutions in India.
We look into the evolution of health informatics and its applications in the healthcare industry.
HIMMS TIGER resources are available to assist Health Informatics education.
Indian Health universities, IT Education institutions, and the healthcare industry must proactively collaborate to start health informatics courses on a big scale. An advocacy push from various stakeholders is also needed for this goal.
Health informatics has huge employment potential and provides a big business opportunity for the healthcare industry. A big pool of trained health informatics manpower can lead to product & service innovations on a global scale in India.
Michigan HealthTech Market Map 2024. Includes 7 categories: Policy Makers, Academic Innovation Centers, Digital Health Providers, Healthcare Providers, Payers / Insurance, Device Companies, Life Science Companies, Innovation Accelerators. Developed by the Michigan-Israel Business Accelerator
Sectional dentures for microstomia patients.pptxSatvikaPrasad
Microstomia, characterized by an abnormally small oral aperture, presents significant challenges in prosthodontic treatment, including limited access for examination, difficulties in impression making, and challenges with prosthesis insertion and removal. To manage these issues, customized impression techniques using sectional trays and elastomeric materials are employed. Prostheses may be designed in segments or with flexible materials to facilitate handling. Minimally invasive procedures and the use of digital technologies can enhance patient comfort. Education and training for patients on prosthesis care and maintenance are crucial for compliance. Regular follow-up and a multidisciplinary approach, involving collaboration with other specialists, ensure comprehensive care and improved quality of life for microstomia patients.
The facial nerve, also known as cranial nerve VII, is one of the 12 cranial nerves originating from the brain. It's a mixed nerve, meaning it contains both sensory and motor fibres, and it plays a crucial role in controlling various facial muscles, as well as conveying sensory information from the taste buds on the anterior two-thirds of the tongue.
NURSING MANAGEMENT OF PATIENT WITH EMPHYSEMA .PPTblessyjannu21
Prepared by Prof. BLESSY THOMAS, VICE PRINCIPAL, FNCON, SPN.
Emphysema is a disease condition of respiratory system.
Emphysema is an abnormal permanent enlargement of the air spaces distal to terminal bronchioles, accompanied by destruction of their walls and without obvious fibrosis.
Emphysema of lung is defined as hyper inflation of the lung ais spaces due to obstruction of non respiratory bronchioles as due to loss of elasticity of alveoli.
It is a type of chronic obstructive
pulmonary disease.
It is a progressive disease of lungs.
English Drug and Alcohol Commissioners June 2024.pptxMatSouthwell1
Presentation made by Mat Southwell to the Harm Reduction Working Group of the English Drug and Alcohol Commissioners. Discuss stimulants, OAMT, NSP coverage and community-led approach to DCRs. Focussing on active drug user perspectives and interests
4. ALGINATE
🞭 Alginate is classified as irreversible hydrocolloid.
🞭 Hydrocolloid because it consists of particles of a gelatinous
(colloidal) state in water (hydro) and irreversible because once
it has jelled it cannot be returned to a liquid solution.
They consist of gelatin particles suspended in water (Lyosol). Since
water is the dispersion medium it is known as hydrocolloid.
5. IRREVERSIBLE HYDROCOLLOID—ALGINATE
The word alginate comes from ‘alginic acid’ (anhydro-β-d-
mannuronic acid) which is a mucous extract yielded by
species of brown seaweed (Phaeophyceae)
Type I — Fast setting.
Type II — Normal setting
6. 🞭 The Word Alginate comes from the term
“ALGIN”.
🞭 It is a peculiar mucous extract yielded by
certain brown seaweed ( algae ) .
🞭 The term „ALGIN‟ was coined by chemist
from scotland @ the end of 19th century.
7. TYPES -
Type I – Fast setting.
Type II – Normal settin g.
8. MODES OF SUPPL
Y
🞭 It is supplied as a powder that is packed:
a) In bulk or in tins or in sackets (or)
b) In preweighed individual containers.
A plastic scoop is supplied for dispensing the bulk
powder, & a plastic cylinder is supplied for measuring
the water .
9.
10. APPLICATIONS
1) Used In impression making :
a) when there are undercuts
b)In mouth with excessive flow of saliva
c)For partial dentures with clasps.
2) Making preliminary/Primary impressions for complete
denture.
3) For orthodontic and study models.
4) For duplicating models.
11. COMPOSITION :
🞭 Potassium alginate(15%)
🞭 Comes from seaweed; is used as a thickening agent.
🞭 Calcium sulfate(16%)
🞭 Reacts with the potassium alginate to form the gel.
🞭 Trisodium phosphate (2%)
🞭 Added to slow down the reaction time for mixing.
12. 🞭 Diatomaceous earth( 60 %)
🞭 A filler that adds bulk to the material.
🞭 Zinc oxide (4%)
🞭 Adds bulk to the material.
🞭 Potassium titanium fluoride(3%)
🞭 Added so as not to interfere with the setting and
surface strength.
13. PHYSICAL PHASES OF ALGINATE
🞭 The first phase is a sol (as in solution). In the sol phase,
the material is in a liquid or semiliquid form.
🞭 The second phase is a gel. In the gel phase, the
material is semisolid, similar to a gelatin dessert.
14. Setting reaction
When alginate powder is mixed with water a sol is formed which later sets to a gel by a chemical
reaction.
The final gel, i.e. insoluble calcium alginate is produced when soluble sodium alginate reacts
with calcium sulfate (reactor). However, this reaction proceeds too fast. There is not enough
working time. So the reaction is delayed by addition of a retarder (trisodium phosphate) by the
manufacturer.
Initially the sodium phosphate reacts with the calcium sulfate to provide adequate working
time.
Reaction 1 2Na3 PO4 + 3CaSO4 Ca3 (PO4 ) 2 + 3Na2 SO4
15. Next after the sodium phosphate is used up, the remaining calcium sulfate reacts with sodium
alginate to form insoluble calcium alginate which forms a gel with water.
Reaction 2 Sodium alginate + CaSO4 + H2 O Ca alginate + Na2 SO4
(Powder) (Gel)
16. SETTING REACTION
🞭 Reaction occurs by a chemical reaction.
🞭 Soluble alginate reacts with calcium sulphate to produce
insoluble calcium alginate as a gel.
🞭 The production of calcium alginate is delayed by the addition of
a third soluble salt to the solution,with which the calcium
sulphate will react in preference to the soluble alginate to form
an insoluble calcium salt.
17. Setting reaction
Chemical reaction named gelation
Calcium sulfate Sodium phosphate
Calcium phosphate + Sodium sulfate (1)
Calcium sulfate Sodium alginate
Insoluble calcium alginate (2)
The speed of the reaction is affected by;
2. Temperature
4. powder particle size
1. L/P ratio
3. Mixing rate
5. Additives
18. In a nutshell , when powder is mixed with water to obtain a paste
,two main reaction occur during setting :
1) 2Na3P04 + 3CaSo4---> Ca3(Po4)2+3 Na2SO4
• First , sodium phosphate reacts with the calcium sulphate to provide adequate
working time.
2) sodium alginate + -------- > Ca alginate +
CaSO4 + H2O
Na2SO4
(Powder )
(Gel)
• Second ,after the sodium phosphate has reacted, the remaining calcium
sulphate reacts with sodium alginate to form an insoluble calcium alginate which
forms a gel with water.
19. WATER-TO-POWDER RATIO
🞭 An adult mandibular impression generally requires two
scoops of powder and two measures of water.
🞭 An adult maxillary impression generally requires three
scoops of powder and three measures of water.
20. Manipulation of Alginate
🞭 Fluff or shake the powder to distribute the powder particles
evenly
🞭 Use the specific measuring devices (water & powder) provided
by the manufacturer for mixing
🞭 Follow the manufacturer‟s direction regarding the ratio of water
to powder.
🞭 Use exact measurements
21. 🞭 After the water and powder have been measured, place the water in
a clean dry bowl.
Sift the powder into the water.
Adding the powder to the water ensures the powder particles are wet
evenly.
If mixed in reverse (the water is added to the powder) the chemical
reaction will start early with some particles setting faster than
others.
22. 🞭 Mix the alginate for the specific amount of time and using a stiff
spatula “swipe” the alginate mass against the sides of the bowl to
avoid entrapment of air in the mix.
figure of
“8”
motion
1. Remove most of the
air bubbles.
2. Wipe dissolved
algin from the surface
of the yet undissolved
algin thereby
promoting complete
dissolution
23. Alginate
Mixing Time
For fast set alginate—45 seconds.
For normal set alginate—60 seconds.
Working Time
Fast set alginate—1¼ minutes.
Normal set alginate—2 minutes.
24.
25. SETTING TIME OF ALGINATE
Since alginate reacts or gels chemically, temperature is a
major factor in the setting time.
The colder the temperature of the water the longer it takes
to set; conversely, the higher the water temperature the
faster it sets.
Ideal water temperature is 68 degrees or room temperature.
26. LOADING OF TRAY
🞭 A perforated tray is used so that the
material is forced out slightly through
the holes in the tray during loading,
thereby locking itself mechanically
into the tray.
🞭 The surface of the alginate in the tray
may be smoothened out by
moistening the finger with water and
running it over the surface of the
alginate.
27. SEATING THE TRAY
🞭 Before making the upper impression, saliva should be wiped off
from the palatal region.
🞭 In order to prevent the material from flowing along the throat and
causing nausea to the patient, the posterior portion may be seated
first and then the anterior portion seated properly.
🞭 Since the material sets from tissues towards periphery,any
movement during gelation may result in distortion.
🞭 So once the tray is seated ,it must be held in place firmly without
any movemnets.
28.
29. REMOVAL OF THE IMPRESSION
🞭 An alginate impression when set develops a very effective
peripheral seal.
🞭 This seal should be freed by running the finger around the
periphery.
🞭 The impression must be removed suddenly
with a jerk.or a snap
🞭 After removal from the mouth,
- washed with water to remove saliva.
-cast should be poured as soon as possible.
30. ALGINATE SETTINGS
🞭 Normal set alginate
Working time of 2 minutes and a setting time of up to 41/2
minutes after mixing.
🞭 Fast set alginate
Working time of 11/4 minutes and a setting time of 1 to
2 minutes.
Working time
The time allowed for mixing the alginate, loading the tray, and
positioning the tray in the patient's mouth.
Setting time
🞭 The time required for the chemical action to be completed.
31. MAKING AN ALGINATE IMPRESSION
🞭 Explain the procedure to the patient:
🞭 The material will feel cold, there is no unpleasant taste,
and the material will set quickly.
🞭 Breathe deeply through your nose to help you relax
and be more comfortable.
🞭 Use hand signals to communicate any
discomfort.
32. AN ACCEPTABLE ALGINATE IMPRESSION
🞭 There is a complete "peripheral roll," which includes
all of the vestibular areas.
🞭 The tray is not "overseated," which would result in
exposure of areas of the impression tray.
🞭 The impression is free from tears or voids.
🞭 There is sharp anatomic detail of all teeth and soft
tissues.
🞭 The retromolar area, lingual frenum, tongue
space, and mylohyoid ridge are reproduced in the
mandibular impression.
🞭 The hard palate and tuberosities are recorded in the
maxillary impression.
33.
34. CAUSES FOR DISTORTION AND DIMENSIONAL
CHANGE OF ALGINATE
🞭 If an alginate impression is stored in water or
in a very wet paper towel, the alginate will
absorb additional water and expand. This
condition is called IMBIBITION.
🞭 If an alginate impression remains in the open
air, moisture will evaporate from the material,
causing it to shrink and distort. This condition
is called SYNERESIS.
35. RECENT ADVANCES IN ALGINATES
Dust free alginates-
De-dusting agent (glycerin or glycol)
Siliconized alginates-
silicon polymers are added to strengthen the material
Alginates containing disinfectants-
eg quaternary ammonium salts or chlorohexamine are added
to alginate powder.
Hard and soft set alginates-
by adjusting the amount of fillers
36. PROPERTIES
1)FLEXIBILITY
It is about 14% at a stress of 1000g/cm2.
Lower w/p ratio results in lower flexibility.
2)ELASTICITY AND ELASTIC RECOVERY
alginate are highly elastic but less when
compared to the agar.
97.3% elastic recovery occurs.
Permanent deformation is less if the impression is
removed from the mouth quickly.
37. 3) STRENGTH
The compressive strengths of alginate gels
range from 5000 to 8000 g/cm2.
The tear strengths vary from 350 to 700 g/cm2.
Both of these properties are time dependent
with higher values being obtained if the time
of removal is delayed.
38. 4) DIMENSIONAL STABILITY :
Alginate impression loses water by
evaporation and shrinks on standing in air.
If it is placed in water it absorbs water and
swells.
Therefore ,cast should be poured immediately
after making the impression.
39. 5)SHELF LIFE
Alginate impression material have a short shelf
life.
They deteriorate rapidly when stored at
elevated temperatures in a humid
environment.
Therefore ,it is better not to stock more than 1
year supply .
40. ADVANTAGES OF ALGINATE
🞭 It makes an accurate impression
🞭 It allows for undercuts
🞭 The process is not time consuming
🞭 It is easy to work with, has good viscosity &
is low in adhesive qualities
🞭 It is comfortable to the patient
🞭 Inexpensive to the dentist
🞭 Requires little armamentarium
41. DISADVANTAGES
1) Can‟t be corrected.
2) Cannot be used alone for compressing the
tissues.
3) It is not accurate enough for crown and
bridge impressions.
42.
43. Definition
A dental impression is a negative record of the tissues of the mouth
It is used to reproduce the form of teeth and surrounding tissues
44. PROPERTIES OF IMPRESSION MATERIAL
Nontoxic and Nonirritant
Acceptable to the patient – pleasant taste, odor,
consistency & color.
Should record accurate surface detail, elastic properties
with no deformation & dimensionally stable
Adequate shelf life for storage and distribution
45. PROPERTIES OF IMPRESSION MATERIAL
Economical
Handling properties- sufficient working time, set quickly in
mouth & minimum equipment.
Have adequate strength so that it will not break or tear
while removing from mouth.
Should be compatible with die and cast material .
46. CLASSIFICATION OF IMPRESSION MATERIAL
A. According to mode of setting and elasticity.
B. According to tissue displacement during impression .
C. According to uses in dentistry.
47. According to mode of setting and elasticity
MODE OF
….SETTING
RIGID ELASTIC
Set by chemical reaction
Irreversible / Thermoset
Impression plaster Zinc oxide
eugenol
Alginate hydrocolloid
Nonaqueous elastomers -e.g.
polysulfide, silicone
Set by temperature change
Reversible/Thermostatic
Compound, Waxes Agar hydrocolloid
48. ACCORDING TO TISSUE DISPLACEMENT
1. Mucostatic
2. Mucocompressive (Mucodisplacive)
49. Mucostatic materials produce minimal displacement of the tissue during
impression, e.g. plaster, zinc oxide eugenol, low viscosity alginates, low
viscosity elastomeric materials, etc.
Mucocompressive materials are more viscous and displace the tissues
while recording them, e.g. compound, high viscosity alginates, high
viscosity elastomers, etc
50. ACCORDING TO THEIR USES IN DENTISTRY
1. Impression materials used for complete denture
prosthesis.
2. Impression materials used for dentulous mouths .
51. Impression materials used for complete denture
prosthesis Impression plaster, impression compound and
impression paste set to a hard rigid mass, and hence cannot
be removed from undercuts without the impression being
fractured or distorted. Therefore these materials are best
suited for edentulous mouth.
52. Impression materials used for dentulous mouths
On the other hand alginates and rubber base impressions
are sufficiently elastic to be withdrawn from undercut areas.
Such elastic impression materials are suitable for
impressions for fabrication of removable and fixed partial
denture prostheses, where the impressions of the ridge and
teeth are required.
53. RIGID IMPRESSION MATERIALS
1. IMPRESSION COMPOUND- rigid, reversible impression material which sets by
physical change. On applying heat, it softens and on cooling it hardens. It is
mainly used for making impressions of edentulous ridges.
CLASSIFICATION
Type I - Impression compound
Type II - Tray compound
54. APPLICATIONS
1. For making a preliminary impression in an edentulous
mouth (mouth without teeth).
2. For impressions of full crown preparations where gingival
tissues must be displaced.
3. Peripheral tracing or border molding.
4. To check undercuts in inlay preparation.
5. To make a special tray
55. REQUIREMENTS OF IMPRESSION COMPOUND
1. Harden at or little above mouth temperature.
2. Be plastic at a temperature not injurious or harmful to oral tissues.
3. Not contain irritating or toxic ingredients.
4. Harden uniformly when cooled without distortion.
5. Have a consistency when softened which will allow it to reproduce
fine details.
6. Be cohesive but not adhesive.
56. ZINC OXIDE EUGENOL IMPRESSION PASTE
Zinc oxide and eugenol based products are widely used in dentistry.
ADA specification No. 16
Available as
In paste form in two tubes
1.Base paste (white in color)
2.Accelerator or reactor or catalyst paste (red in color)
CLASSIFICATION
Type I or Hard
Type II or Soft
57. COMPOSITION
Base paste:
Zinc Oxide 87%
Vegetable or mineral oil:13%
Accelerator paste:
Oil of cloves or eugenol: 12%
Gum or polymerized rosin 50%
Filler 20%
Lanolin 3%
Calcium chloride and color 5%
58. SETTING REACTION
SETTING REACTION The setting reaction is a typical acid-base reaction to form a
chelate. This reaction is also known as chelation and the product is called zinc
eugenolate.
1. ZnO + H2O Zn(OH)2
2. Zn(OH)2 + 2HE ZnE2 + 2H2O
59. ELASTIC IMPRESSION MATERIALS
Two systems are used
1. Hydrocolloids
2. Elastomeric materials
Hydrocolloids :
They consist of gelatin particles suspended in water
(Lyosol). Since water is the dispersion medium it is
known as hydrocolloid.
60. Based on the mode of gelation
Reversible hydrocolloids They are called reversible because their physical state can be reversed.
This makes them reusable.
Irreversible hydrocolloids Once these set, it is usually permanent, and so are known as
irreversible.
Reversible hydrocolloids—Agar
Classification BASED ON VISCOSITY
Type 1 — Heavy bodied (for use as tray material)
Type 2 — Medium bodied (for use as tray or syringe material)
Type 3 — Light bodied (for syringe use only)
Type 3A — Light bodied for agar-alginate combination technique
61. AGAR
SUPPLIED AS
Gel in collapsible tubes (for impressions)
As cartridges or gel sticks (syringe material)
In bulk containers (for duplication)
62. AGAR
INGREDIENT FUNCTIONS
AGAR 13-17% Basic constituent
BORATES 0.2-0.5% Improves strength and retards setting of
plaster
Potassium sulphate 1–2% It counters retarding effect of borates
Wax, hard 0.5–1% It acts as a filler
Thixotropic materials 0.3–0.5% It acts as plasticizer
Alkylbenzoates 0.1 % It acts as preservative.
Coloring and flavoring agents Traces For patient comfort and acceptance
Water B alance (around 84%) It acts as the dispersion medium
63. Gelation or setting of agar
Agar changes from the sol to the gel state (and vice versa) by a
physical process.
As the agar sol cools the dispersed phase groups to form fibrils
called micelles.
The fibrils branch and intermesh together to form a brush-heap
structure.
64.
65. AGAR
The fibrils form weak covalent bonds with each other which break easily at
higher temperatures resulting in gel turning to sol.
The process of converting gel to sol is known as liquefaction which occurs at a
temperature between 70 and 100 °C.
On cooling agar reverses to the gel state and the process is called gelation.
Gelation occurs at or near mouth temperature which is necessary to avoid
injury to oral tissue.
66. PROPERTIES OF AGAR HYDROCOLLOIDS
Gelation, liquefaction and hysteresis
Syneresis and imbibition (dimensional stability)
Flexibility
Elasticity and elastic recovery
Gel strength including tear and compressive strengths
67. ADVANTAGES
1. Accurate dies can be prepared, if the material is properly
handled.
2. Good elastic properties help reproduce most undercut
areas.
3. It has good recovery from distortion.
4. Hydrophilic, moist mouth not a problem. It also gives a
good model surface.
68. Disadvantages of agar
1. Does not flow well when compared to newly available
materials.
2. It cannot be electroplated.
3. During insertion or gelation the patient may experience
thermal discomfort.
4. Tears relatively easily. Greater gingival retraction is
required for providing adequate thickness of the material.
69. IRREVERSIBLE HYDROCOLLOID—ALGINATE
The word alginate comes from ‘alginic acid’ (anhydro-β-d-
mannuronic acid) which is a mucous extract yielded by
species of brown seaweed (Phaeophyceae)
Type I — Fast setting.
Type II — Normal setting
70. ALGINATE
As a two paste system One contains the alginate sol, while the second contains
the calcium reactor.
One product is supplied in low density for use with syringe
Dust free alginates Concern over the inhalation of alginate dust have prompted
manufacturers to introduce ‘dust free alginates’
Chromatic alginates Alginates which change color on setting
Commercial names: Zelgan (DPI), Jeltrate (Dentsply), Hydrogum (Zhermack),
etc.`
71. APPLICATIONS
1. It is used for impression making – When there are undercuts. – In
mouths with excessive flow of saliva. – For partial dentures with
clasps.
2. For making preliminary impressions for complete dentures.
3. For impressions to make study models and working casts. 4. For
duplicating models.
72. COMPOSITION -AGAR
Ingredients % wt Function
Sodium or potassium alginate Dissolves in water and reacts with
calcium ions
Calcium sulfate (reactor) Reacts with potassium alginate and
forms insoluble calcium alginate
Zinc oxide Acts as a filler
Potassium titanium fluoride Gypsum hardener
Diatomaceous earth Acts as a filler
Sodium phosphate (retarder) Reacts preferentially with calcium sulfate
Coloring and flavoring agent e.g. wintergreen, peppermint
73. Setting reaction
When alginate powder is mixed with water a sol is formed which later sets to a gel by a chemical
reaction.
The final gel, i.e. insoluble calcium alginate is produced when soluble sodium alginate reacts
with calcium sulfate (reactor). However, this reaction proceeds too fast. There is not enough
working time. So the reaction is delayed by addition of a retarder (trisodium phosphate) by the
manufacturer.
Initially the sodium phosphate reacts with the calcium sulfate to provide adequate working
time.
Reaction 1 2Na3 PO4 + 3CaSO4 Ca3 (PO4 ) 2 + 3Na2 SO4
74. Next after the sodium phosphate is used up, the remaining calcium sulfate reacts with sodium
alginate to form insoluble calcium alginate which forms a gel with water.
Reaction 2 Sodium alginate + CaSO4 + H2 O Ca alginate + Na2 SO4
(Powder) (Gel)
75. PROPERTIES OF ALGINATE HYDROCOLLOID
1. Pleasant Taste and Odor
2. Flexibility
3. Elasticity and Elastic Recovery
4. Reproduction of Tissue Detail
5. Strength -Compressive strengths •
Ranges from 0.5 to 0.9
MPa.
6. Syneresis and Imbibition
76. Manipulation of Alginate
Fluff or aerate the powder by inverting the can several times. This ensures
uniform distribution of the filler before mixing.
The proper W/P ratio as specified by the manufacturer should be used (usually
one measure water with two level scoops of powder.
The water is taken first. The powder is sprinkled in to the water in the rubber
mixing bowl and the lid of the metal can is replaced immediately.
The mixing is started with a stirring motion to wet the powder with water.
77. Once the powder has been moistened, rapid spatulation by swiping or stropping
against the side of the bowl is done.
A vigorous figure-eight motion can also be used.
This helps
1. Remove most of the air bubbles.
2. Wipe dissolved algin from the surface of the yet undissolved algin thereby
promoting complete dissolution.
78. Alginate
Mixing Time
For fast set alginate—45 seconds.
For normal set alginate—60 seconds.
Working Time
Fast set alginate—1¼ minutes.
Normal set alginate—2 minutes.
79. ELASTOMERIC IMPRESSION MATERIALS
Elastomers are essentially polymers with elastic or rubber-like properties.
They contain large molecules with weak interaction between them. They are
tied together at certain points to form a three-dimensional network.
On stretching, the chains uncoil, and on removal of the stress they snap back
to their relaxed entangled state
They are amorphous polymers existing above their glass transition
temperature, so that considerable segmental motion is possible.
80. Types of polymerization reactions:
In elastomers 3 types of polymerization reactions are seen:
1. Addition polymerization
2. Condensation polymerization
3. Ring opening polymerization
81. Classification :
According to their chemistry,
1. Polysulfide
2. Condensation polymerizing silicones
3. Addition polymerizing silicones
4. Polyether
82. According to viscosity (ISO 4823:2015) they are further divided
based on consistencies determined immediately after completion of
mixing,
Type 0—Putty consistency (very heavy)
Type 1—Heavy-bodied consistency (tray consistency)
Type 2—Medium-bodied consistency (regular bodied)
Type 3—Light-bodied (syringe consistency)
83. According to wetting ability or contact angle,
1. Hydrophilic, if their contact angle is from 80 to 105°.
2. Hydrophobic, if their contact angle is from 40 to 70°
84. Uses:
1. In fixed partial dentures for impressions of prepared teeth.
2. Impressions of dentulous mouths for removable partial dentures.
3. Impressions of edentulous mouths for complete dentures.
4. Polyether is used for border molding of edentulous custom trays.
5. For bite registration.
6. Silicone duplicating material is used for making refractory casts
during cast partial denture construction
85. Supplied as :
1. Two component (base and catalyst) systems,
2. Cartridges—light and regular body material are also supplied in
cartridges to be used with static mixing tips and
dispensers
3.Putty consistency is supplied in jars