Casting procedures are the backbone of indirect restorations. No casting can be fabricated with their casting defects. It is necessary to have the knowledge of casting defects , how they occure, and how to prevent them.
This document provides an overview of dental ceramics. It defines ceramics as inorganic compounds formed from metallic, semi-metallic, and nonmetallic elements that are subjected to high heat. Dental ceramics are commonly used for crowns, bridges, inlays and other restorations. They are composed mainly of feldspars, quartz, and kaolin that undergo firing and produce a vitreous glassy phase and crystalline phase. Dental ceramics are strengthened through various techniques to increase their durability for use in load-bearing applications in the mouth.
This document discusses dental investment materials and procedures used for lost wax casting. It begins with an introduction and history of lost wax casting. It then defines dental investment and discusses the requirements, material science, and types of investments including composition, setting reactions, and properties. The document outlines the investing procedure and potential defects. It concludes with an overview of dental investment materials for lost wax casting.
Ceramics have many applications in dentistry due to their esthetic qualities, strength, and biocompatibility. Ceramics are used in crowns, bridges, veneers, dentures, and more. There are several types of ceramics including metal-ceramics, which combine a ceramic material fused to a metal framework for strength, and all-ceramic options made of materials like alumina and zirconia. Ceramic materials are fabricated through processes like sintering, heat pressing, slip-casting, and CAD/CAM milling. Ceramics provide natural-looking and long-lasting restorations but also have limitations like brittleness which new materials continue to address
The document discusses the process of casting in dentistry. It begins with an introduction defining casting and its objective in dentistry. It then covers the history of casting in dentistry from ancient times through modern developments. The basic steps of casting are outlined, including spruing, investing, burnout, casting, recovery and cleaning. Different materials used for sprue formers, crucible formers, casting rings and liners are described. The document provides details on investing, burnout, and high and low heat techniques for casting gold and other alloys.
This document provides information on dental casting procedures. It discusses the history of casting, steps in the casting process such as wax pattern fabrication and sprue attachment, types of investments and burnout procedures. The key points are: casting has been used since ancient times to produce jewelry and was introduced to dentistry by Taggart in 1907; the process involves fabricating a wax pattern, investing it, then burning out the wax and casting dental alloys into the mold.
This document outlines the steps in the lost wax casting procedure for dental restorations. It begins by introducing lost wax casting and describing the key steps: 1) Wax pattern removal, 2) Spruing, 3) Investing, 4) Burnout, 5) Casting. It then provides details on wax patterns, sprue formers, crucible formers, casting rings, and the investing procedure. Important considerations for each step are highlighted to produce an accurate casting.
This document discusses dental porcelain, including its composition, manufacturing process, strengthening methods, and applications in ceramic and metal-ceramic restorations. Dental porcelain is a type of ceramic composed of kaolin, silica, and feldspar that is fired at high temperatures. It is used for ceramic crowns, veneers, and metal-ceramic restorations due to its biocompatibility, esthetics, and thermal properties matching enamel and dentin. However, porcelain is also brittle with low tensile strength, so various strengthening techniques are used. Metal-ceramic restorations bond porcelain to metal frameworks, requiring thermal and chemical compatibility between the materials.
This document provides an overview of dental casting procedures and defects. It defines casting and describes the main steps which include making a wax pattern, spruing, investing, burnout of the wax, casting with different methods, cleaning the casting, and finishing and polishing. It also discusses common casting defects such as distortion, surface roughness, porosity, and missing details. The document is intended to educate dental students and professionals about casting techniques and potential defects.
This document provides an overview of dental ceramics. It defines ceramics as inorganic compounds formed from metallic, semi-metallic, and nonmetallic elements that are subjected to high heat. Dental ceramics are commonly used for crowns, bridges, inlays and other restorations. They are composed mainly of feldspars, quartz, and kaolin that undergo firing and produce a vitreous glassy phase and crystalline phase. Dental ceramics are strengthened through various techniques to increase their durability for use in load-bearing applications in the mouth.
This document discusses dental investment materials and procedures used for lost wax casting. It begins with an introduction and history of lost wax casting. It then defines dental investment and discusses the requirements, material science, and types of investments including composition, setting reactions, and properties. The document outlines the investing procedure and potential defects. It concludes with an overview of dental investment materials for lost wax casting.
Ceramics have many applications in dentistry due to their esthetic qualities, strength, and biocompatibility. Ceramics are used in crowns, bridges, veneers, dentures, and more. There are several types of ceramics including metal-ceramics, which combine a ceramic material fused to a metal framework for strength, and all-ceramic options made of materials like alumina and zirconia. Ceramic materials are fabricated through processes like sintering, heat pressing, slip-casting, and CAD/CAM milling. Ceramics provide natural-looking and long-lasting restorations but also have limitations like brittleness which new materials continue to address
The document discusses the process of casting in dentistry. It begins with an introduction defining casting and its objective in dentistry. It then covers the history of casting in dentistry from ancient times through modern developments. The basic steps of casting are outlined, including spruing, investing, burnout, casting, recovery and cleaning. Different materials used for sprue formers, crucible formers, casting rings and liners are described. The document provides details on investing, burnout, and high and low heat techniques for casting gold and other alloys.
This document provides information on dental casting procedures. It discusses the history of casting, steps in the casting process such as wax pattern fabrication and sprue attachment, types of investments and burnout procedures. The key points are: casting has been used since ancient times to produce jewelry and was introduced to dentistry by Taggart in 1907; the process involves fabricating a wax pattern, investing it, then burning out the wax and casting dental alloys into the mold.
This document outlines the steps in the lost wax casting procedure for dental restorations. It begins by introducing lost wax casting and describing the key steps: 1) Wax pattern removal, 2) Spruing, 3) Investing, 4) Burnout, 5) Casting. It then provides details on wax patterns, sprue formers, crucible formers, casting rings, and the investing procedure. Important considerations for each step are highlighted to produce an accurate casting.
This document discusses dental porcelain, including its composition, manufacturing process, strengthening methods, and applications in ceramic and metal-ceramic restorations. Dental porcelain is a type of ceramic composed of kaolin, silica, and feldspar that is fired at high temperatures. It is used for ceramic crowns, veneers, and metal-ceramic restorations due to its biocompatibility, esthetics, and thermal properties matching enamel and dentin. However, porcelain is also brittle with low tensile strength, so various strengthening techniques are used. Metal-ceramic restorations bond porcelain to metal frameworks, requiring thermal and chemical compatibility between the materials.
This document provides an overview of dental casting procedures and defects. It defines casting and describes the main steps which include making a wax pattern, spruing, investing, burnout of the wax, casting with different methods, cleaning the casting, and finishing and polishing. It also discusses common casting defects such as distortion, surface roughness, porosity, and missing details. The document is intended to educate dental students and professionals about casting techniques and potential defects.
The document discusses different types of investment materials used to create molds for dental restorations and appliances. It describes the requirements for investment materials including refractory and binding properties. Three common types are discussed - gypsum-bonded, phosphate-bonded, and silica-bonded - along with their compositions, setting reactions, properties and limitations. Gypsum is suitable for gold alloys but not high-temperature alloys. Phosphate-bonded materials withstand higher temperatures. Silica-bonded provides high thermal expansion to compensate for casting shrinkage. The proper selection of investment material depends on the alloy and desired mold properties.
This document discusses casting procedures and defects. It covers topics like the history of casting, wax patterns, spruing wax patterns, investing wax patterns, burning out wax, casting dental alloys, defects, and more. The lost wax technique involves surrounding a wax pattern with investment material, burning out the wax, and introducing molten metal into the mold. Proper spruing, investing, burnout, and casting are important to produce successful dental castings.
This document discusses abrasives used in dentistry. It defines abrasion and describes the different types including two-body, three-body, and erosion abrasion. The principles of cutting, grinding, and polishing are explained. Desirable characteristics of abrasives and factors affecting abrasion rates are outlined. Various natural and synthetic abrasives are classified and their uses described, including diamond, aluminum oxide, silicon carbide, and others. Recent advances in abrasives like air abrasion technology and CVD diamond coated burs are also mentioned.
The document discusses direct gold restorations, including different types of direct filling golds such as gold foil, electrolytically precipitated gold, and powdered gold. It covers the properties, advantages, and disadvantages of direct gold, as well as indications and contraindications for its use. Guidelines are provided on cavity preparation and the general steps for placing direct gold restorations.
Casting Procedures & Casting Defects in DentistryJehan Dordi
This document provides information on casting procedures used in dentistry. It discusses various topics related to casting including sprue and spruing, crucible formers, investing, burnout procedures, casting machines, fluxes, heat treatment, divesting, finishing, defects, and literature reviews. The key steps in casting procedures are outlined, including tooth preparation, impression, die preparation, wax pattern fabrication, spruing, investing, burnout, casting, divesting, cleaning, and finishing the casting. Detailed information is provided on sprue types, materials, length, diameter, direction, location, and techniques for spruing patterns of different types and sizes.
This document discusses the process of dental casting. It begins by defining casting and listing the main steps: preparing the wax pattern, spruing, investing, burnout, casting, recovery, and finishing. It then provides details on each step, including preparing the wax pattern, sprue design and materials, investing techniques, burnout methods, and common casting defects like porosity and distortion. The document is intended as an overview and guide for the dental casting procedure.
One of the oldest filling material among all restorative materials available. Nobel metal filling, which do not undergo Tarnish & Corrosion & having good Biocompatibility.
Classification
foil, electrolytic precipitate & powder gold.
cohesive &non-cohesive form
manipulation
annealing / degassing
Compaction
indication
contraindicatioin
advantage
disadvantages.
Dental Ceramics and Porcelain fused to metal isabel
This document discusses ceramics and porcelain fused to metal restorations. It describes the composition and properties of dental ceramics and porcelains, including feldspathic and aluminous porcelains. The applications and parts of porcelain fused to metal restorations are outlined. The benefits and drawbacks of metal-ceramic restorations are summarized. Requirements for the metal coping and bonding of porcelain to the coping are also summarized.
The document provides an overview of denture base resins including their definition, history, classification, key ingredients, and properties. It discusses the early use of materials like ivory, bone, and porcelain for dentures and the later development of vulcanite in the 1840s as the first affordable and workable material. Polymethyl methacrylate (PMMA) was introduced in the 1930s and became the standard material by 1946, providing improved properties over previous materials. The document outlines the polymerization process and ideal requirements for denture base resins based on biocompatibility, durability, and other factors. Heat-cured PMMA denture base resin is currently the most widely used material.
The document discusses the process of investing and casting in fixed prosthodontics. Key steps include:
1. Attaching a wax pattern to a sprue former and investing it in dental stone.
2. Eliminating the wax pattern by heating the stone mold to burn out the wax.
3. Pouring molten dental alloy into the mold cavity using a centrifugal casting machine to produce a dental casting.
4. Finishing the casting by removing the sprue and investing material and polishing the surfaces.
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.
The document provides information on dental casting investments. It discusses the lost wax technique for metal casting, which involves making a wax pattern, investing it with dental casting material, and burning out the wax to leave a mold for molten metal. Gypsum-bonded investments are commonly used for casting gold alloys. They consist of silica refractory material bound with calcium sulfate. The investments undergo setting expansion during hardening and thermal expansion during heating to compensate for metal shrinkage. Factors like water-to-powder ratio, silica content, heating temperature, and cooling affect the investments' expansion and strength properties.
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.
The document provides an overview of the process of spruing, investing, and casting. It discusses constructing a wax pattern, creating a sprue to allow molten metal to flow into the mold, using a casting ring and liner to contain the investment material. It also covers investing materials, the investing process, burnout to eliminate wax, casting including melting alloys and techniques, quenching, pickling, divesting, and finishing processes like polishing. The overall process involves surrounding a wax pattern with a refractory investment material, heating to remove wax, and introducing molten metal to create a dental restoration.
Dental waxes are used to create patterns for dental restorations and appliances, with the main types being pattern waxes like inlay wax for dental restorations, processing waxes for tasks like boxing impressions, and impression waxes for corrections or bite registration. Inlay wax is a common pattern wax that comes in different types for direct or indirect use and has properties like thermal expansion and potential for distortion that make it suitable for creating wax patterns.
The document discusses various casting defects that can occur in dental castings including distortion, surface roughness, porosity, incomplete casting, and discoloration. It provides detailed explanations of different types of porosity defects such as localized shrinkage porosity, microporosity, pinhole porosity, gas inclusions, subsurface porosity, and back pressure porosity. Causes and methods for prevention of each type of defect are described. Surface roughness can result from factors like air bubbles in the wax pattern, water films, temperature variations during casting, foreign bodies in the mold, and composition or application of the investment material.
This document discusses dental casting investments, which are materials used to form molds for casting dental restorations like crowns and bridges. It describes the components of investments, including refractory materials like silica, binders like gypsum or phosphate, and modifiers. It explains the properties investments must have like strength, expansion to compensate for shrinkage, and smooth surfaces. It covers the different types of investments including gypsum-bonded, phosphate-bonded, and silica-bonded and their appropriate uses and temperature ranges. It also discusses factors that affect the investments' setting expansion to help compensate for casting shrinkage.
This document provides an overview of dental ceramics. It discusses the history, structure, composition, properties, classification, and fabrication of dental ceramics. The key points are: Dental ceramics can be crystalline or non-crystalline. Common components include feldspar, silica, alumina, and color pigments. Ceramics are classified based on firing temperature, microstructure, and indications. Metal-ceramic systems involve a cast metal framework with ceramic layers bonded to it. The fabrication process involves building and firing layers of ceramic powder to form the final restoration.
The document discusses definitive casts and dies used in fixed prosthodontics. It defines a definitive cast as a positive replica of the prepared teeth and surrounding structures. A die is the positive reproduction of the prepared tooth. There are several techniques for creating dies that can be removed from the definitive cast, including the dowel pin technique, Pindex system, and Di-Lock tray technique. The document also discusses requirements and various materials used for dies, such as gypsum, resin, electroplated metals, and ceramics. Virtual definitive casts and dies created using CAD/CAM systems are also introduced.
The document discusses different types of investment materials used to create molds for dental restorations and appliances. It describes the requirements for investment materials including refractory and binding properties. Three common types are discussed - gypsum-bonded, phosphate-bonded, and silica-bonded - along with their compositions, setting reactions, properties and limitations. Gypsum is suitable for gold alloys but not high-temperature alloys. Phosphate-bonded materials withstand higher temperatures. Silica-bonded provides high thermal expansion to compensate for casting shrinkage. The proper selection of investment material depends on the alloy and desired mold properties.
This document discusses casting procedures and defects. It covers topics like the history of casting, wax patterns, spruing wax patterns, investing wax patterns, burning out wax, casting dental alloys, defects, and more. The lost wax technique involves surrounding a wax pattern with investment material, burning out the wax, and introducing molten metal into the mold. Proper spruing, investing, burnout, and casting are important to produce successful dental castings.
This document discusses abrasives used in dentistry. It defines abrasion and describes the different types including two-body, three-body, and erosion abrasion. The principles of cutting, grinding, and polishing are explained. Desirable characteristics of abrasives and factors affecting abrasion rates are outlined. Various natural and synthetic abrasives are classified and their uses described, including diamond, aluminum oxide, silicon carbide, and others. Recent advances in abrasives like air abrasion technology and CVD diamond coated burs are also mentioned.
The document discusses direct gold restorations, including different types of direct filling golds such as gold foil, electrolytically precipitated gold, and powdered gold. It covers the properties, advantages, and disadvantages of direct gold, as well as indications and contraindications for its use. Guidelines are provided on cavity preparation and the general steps for placing direct gold restorations.
Casting Procedures & Casting Defects in DentistryJehan Dordi
This document provides information on casting procedures used in dentistry. It discusses various topics related to casting including sprue and spruing, crucible formers, investing, burnout procedures, casting machines, fluxes, heat treatment, divesting, finishing, defects, and literature reviews. The key steps in casting procedures are outlined, including tooth preparation, impression, die preparation, wax pattern fabrication, spruing, investing, burnout, casting, divesting, cleaning, and finishing the casting. Detailed information is provided on sprue types, materials, length, diameter, direction, location, and techniques for spruing patterns of different types and sizes.
This document discusses the process of dental casting. It begins by defining casting and listing the main steps: preparing the wax pattern, spruing, investing, burnout, casting, recovery, and finishing. It then provides details on each step, including preparing the wax pattern, sprue design and materials, investing techniques, burnout methods, and common casting defects like porosity and distortion. The document is intended as an overview and guide for the dental casting procedure.
One of the oldest filling material among all restorative materials available. Nobel metal filling, which do not undergo Tarnish & Corrosion & having good Biocompatibility.
Classification
foil, electrolytic precipitate & powder gold.
cohesive &non-cohesive form
manipulation
annealing / degassing
Compaction
indication
contraindicatioin
advantage
disadvantages.
Dental Ceramics and Porcelain fused to metal isabel
This document discusses ceramics and porcelain fused to metal restorations. It describes the composition and properties of dental ceramics and porcelains, including feldspathic and aluminous porcelains. The applications and parts of porcelain fused to metal restorations are outlined. The benefits and drawbacks of metal-ceramic restorations are summarized. Requirements for the metal coping and bonding of porcelain to the coping are also summarized.
The document provides an overview of denture base resins including their definition, history, classification, key ingredients, and properties. It discusses the early use of materials like ivory, bone, and porcelain for dentures and the later development of vulcanite in the 1840s as the first affordable and workable material. Polymethyl methacrylate (PMMA) was introduced in the 1930s and became the standard material by 1946, providing improved properties over previous materials. The document outlines the polymerization process and ideal requirements for denture base resins based on biocompatibility, durability, and other factors. Heat-cured PMMA denture base resin is currently the most widely used material.
The document discusses the process of investing and casting in fixed prosthodontics. Key steps include:
1. Attaching a wax pattern to a sprue former and investing it in dental stone.
2. Eliminating the wax pattern by heating the stone mold to burn out the wax.
3. Pouring molten dental alloy into the mold cavity using a centrifugal casting machine to produce a dental casting.
4. Finishing the casting by removing the sprue and investing material and polishing the surfaces.
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.
The document provides information on dental casting investments. It discusses the lost wax technique for metal casting, which involves making a wax pattern, investing it with dental casting material, and burning out the wax to leave a mold for molten metal. Gypsum-bonded investments are commonly used for casting gold alloys. They consist of silica refractory material bound with calcium sulfate. The investments undergo setting expansion during hardening and thermal expansion during heating to compensate for metal shrinkage. Factors like water-to-powder ratio, silica content, heating temperature, and cooling affect the investments' expansion and strength properties.
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.
The document provides an overview of the process of spruing, investing, and casting. It discusses constructing a wax pattern, creating a sprue to allow molten metal to flow into the mold, using a casting ring and liner to contain the investment material. It also covers investing materials, the investing process, burnout to eliminate wax, casting including melting alloys and techniques, quenching, pickling, divesting, and finishing processes like polishing. The overall process involves surrounding a wax pattern with a refractory investment material, heating to remove wax, and introducing molten metal to create a dental restoration.
Dental waxes are used to create patterns for dental restorations and appliances, with the main types being pattern waxes like inlay wax for dental restorations, processing waxes for tasks like boxing impressions, and impression waxes for corrections or bite registration. Inlay wax is a common pattern wax that comes in different types for direct or indirect use and has properties like thermal expansion and potential for distortion that make it suitable for creating wax patterns.
The document discusses various casting defects that can occur in dental castings including distortion, surface roughness, porosity, incomplete casting, and discoloration. It provides detailed explanations of different types of porosity defects such as localized shrinkage porosity, microporosity, pinhole porosity, gas inclusions, subsurface porosity, and back pressure porosity. Causes and methods for prevention of each type of defect are described. Surface roughness can result from factors like air bubbles in the wax pattern, water films, temperature variations during casting, foreign bodies in the mold, and composition or application of the investment material.
This document discusses dental casting investments, which are materials used to form molds for casting dental restorations like crowns and bridges. It describes the components of investments, including refractory materials like silica, binders like gypsum or phosphate, and modifiers. It explains the properties investments must have like strength, expansion to compensate for shrinkage, and smooth surfaces. It covers the different types of investments including gypsum-bonded, phosphate-bonded, and silica-bonded and their appropriate uses and temperature ranges. It also discusses factors that affect the investments' setting expansion to help compensate for casting shrinkage.
This document provides an overview of dental ceramics. It discusses the history, structure, composition, properties, classification, and fabrication of dental ceramics. The key points are: Dental ceramics can be crystalline or non-crystalline. Common components include feldspar, silica, alumina, and color pigments. Ceramics are classified based on firing temperature, microstructure, and indications. Metal-ceramic systems involve a cast metal framework with ceramic layers bonded to it. The fabrication process involves building and firing layers of ceramic powder to form the final restoration.
The document discusses definitive casts and dies used in fixed prosthodontics. It defines a definitive cast as a positive replica of the prepared teeth and surrounding structures. A die is the positive reproduction of the prepared tooth. There are several techniques for creating dies that can be removed from the definitive cast, including the dowel pin technique, Pindex system, and Di-Lock tray technique. The document also discusses requirements and various materials used for dies, such as gypsum, resin, electroplated metals, and ceramics. Virtual definitive casts and dies created using CAD/CAM systems are also introduced.
This document describes the laboratory procedures for fabricating a cast partial denture (CPD). It discusses making an accurate cast from the dental impression, including pouring, trimming, and correcting the cast. It also covers surveying the cast to determine the denture design, blocking out undercuts, duplicating the cast in refractory material, and waxing up the denture framework on the duplicated cast. The goal is to produce an accurate cast from which a well-fitting CPD can be fabricated following standardized laboratory techniques.
The document discusses different techniques for creating working casts with removable dies, including straight and curved dowel pins, pindex systems, and Di-Lok trays. Removable dies allow the fabrication of wax patterns on individual teeth and must return to their exact positions to ensure accurate articulation. Proper die preparation, such as trimming without reducing access or altering contours, is important for producing casts that facilitate wax pattern fabrication.
Wax patterns fabrication for fixed partial denturesShebin Abraham
This document provides information on the principles and techniques for fabricating wax patterns for crowns and fixed dental prostheses using the lost wax technique. It discusses the prerequisites for wax patterns including correcting defects on dies, providing cement space, and marking margins. Details are given on materials used for wax patterns and different waxing techniques. The sequence of wax pattern fabrication is outlined including coping formation, evaluation, shaping proximal, axial, and occlusal surfaces, and finishing margins. Occlusal schemes and developing cusp-fossa and cusp-marginal ridge relationships during waxing are also described. The goal is to produce highly accurate wax patterns to result in well-fitting cast restorations.
This document discusses dies and die systems used for indirect dental restorations. It begins by defining a die as a positive reproduction of the prepared tooth used to make dental restorations. It then classifies die materials as metallic or non-metallic and discusses their properties. Different die systems are described that use techniques like separate dies, removable dies with dowel pins, tray systems, and baseplate systems to accurately reproduce the prepared teeth and allow for fabrication of restorations. The document provides details on the procedures, advantages and disadvantages of various die materials and systems.
Impression Techniques in Fixed partial dentureDr.Richa Sahai
This document provides information on dental impressions, including:
- Criteria for an ideal impression include accurately recording all tooth structure and contours.
- Definitions of impression, impression material, and cast.
- Overview of different impression techniques discussed in literature such as stock tray, custom tray, copper band, and hydrocolloid impressions.
- Key steps for making impressions including use of retraction cords, evaluating the final impression, and pouring the stone cast.
- The document is intended to inform dentists on selecting appropriate impression materials and techniques.
INTRODUCTION- Removable partial denture: the replacement of missing teeth and supporting tissues with a prosthesis designed to be removed by the wearer-GPT.
Cast partial denture is a type of partial denture comprising a cast metal framework with acrylic resin prosthetic teeth.
Traditional acrylic partial dentures are less durable, retentive, and stronger than cast partial dentures.
This document discusses the process of fabricating custom trays for dental impressions. It begins by defining a custom tray and listing criteria for their construction. There are two main methods described - constructing a resin tray using a finger adaptation or sprinkle-on technique, or a shellac tray. For resin trays, the process involves outlining features on the preliminary cast like sulci and borders, adapting a wax spacer, and then applying resin to the cast. For shellac trays, a preformed base is softened and adapted to the cast, with borders rolled and excess trimmed. The document compares advantages of resin versus shellac trays.
This document discusses different die and die systems used in fabricating fixed partial dentures. It describes the ideal properties and requirements of die materials, as well as the main types of die systems including separate die systems, removable die systems using dowel pins, di-lok trays, or pindex drilling. The advantages and disadvantages of each system are provided. Removable die systems allow dies to be easily removed and replaced in the working cast for wax pattern fabrication.
Lab procedures in complete denture prosthodontics/prosthodontic coursesIndian 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.for more details please visit
www.indiandentalacademy.com
Lab procedures in complete denture prosthodontics/ dental education in indiaIndian dental academy
Indian Dental Academy: will be one of the most relevant and exciting training
center with best faculty and flexible training programs for dental
professionals who wish to advance in their dental practice,Offers certified
courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry,
Prosthetic Dentistry, Periodontics and General Dentistry.
Indian Dental Academy: will be one of the most relevant and exciting training
center with best faculty and flexible training programs for dental
professionals who wish to advance in their dental practice,Offers certified
courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry,
Prosthetic Dentistry, Periodontics and General Dentistry.
Indian Dental Academy: will be one of the most relevant and exciting training
center with best faculty and flexible training programs for dental
professionals who wish to advance in their dental practice,Offers certified
courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry,
Prosthetic Dentistry, Periodontics and General Dentistry.
Working cast and dies /certified fixed orthodontic courses by Indian dental a...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.for more details please visit
www.indiandentalacademy.com
This document discusses complex amalgam restorations used to replace missing tooth structure from teeth with fractures or caries. It covers indications, contraindications, types including pin-retained, slot-retained, and amalgam foundations. Details are provided on pin selection, placement techniques to maximize retention, and potential procedural problems. The document aims to guide dentists on best practices for complex amalgam restorations.
Easy way to read dental record base,Details information of re dental cord base, theory of record base
Dental record base notes,
Record base notes Slideshow,
Online notes on record base
Enotes record base,
Dental students all notes
- Record bases help transfer accurate jaw relationships to an articulator to enable setting artificial teeth for a trial denture. They can be temporary or permanent.
- Temporary record bases include shellac, reinforced shellac, cold cure acrylic, and vacuum formed bases. Permanent bases are not discarded and become part of the final denture base, like heat cure acrylic, gold, or cobalt-chromium alloys.
- Occlusion rims are built on record bases to make jaw relation records and arrange teeth. They must be in the anticipated tooth position, securely attached to the base, and have a smooth, flat occlusal surface that supports lips and cheeks.
The document summarizes laboratory procedures for fabricating a metal partial denture framework. It discusses preparing the master cast, duplicating the cast, wax pattern and spruing, investing and burnout, casting the framework, and finishing. Key steps include:
1) Preparing the master cast by beading the major connector, spraying with sealant, blocking out undercuts, and providing relief.
2) Duplicating the master cast using reversible hydrocolloid in a flask.
3) Creating the wax pattern by adapting pre-made plastic patterns to the refractory cast and joining them with wax, then spruing the pattern.
4) Investing involves using gypsum, phosphate, or sil
Main Java[All of the Base Concepts}.docxadhitya5119
This is part 1 of my Java Learning Journey. This Contains Custom methods, classes, constructors, packages, multithreading , try- catch block, finally block and more.
Philippine Edukasyong Pantahanan at Pangkabuhayan (EPP) CurriculumMJDuyan
(𝐓𝐋𝐄 𝟏𝟎𝟎) (𝐋𝐞𝐬𝐬𝐨𝐧 𝟏)-𝐏𝐫𝐞𝐥𝐢𝐦𝐬
𝐃𝐢𝐬𝐜𝐮𝐬𝐬 𝐭𝐡𝐞 𝐄𝐏𝐏 𝐂𝐮𝐫𝐫𝐢𝐜𝐮𝐥𝐮𝐦 𝐢𝐧 𝐭𝐡𝐞 𝐏𝐡𝐢𝐥𝐢𝐩𝐩𝐢𝐧𝐞𝐬:
- Understand the goals and objectives of the Edukasyong Pantahanan at Pangkabuhayan (EPP) curriculum, recognizing its importance in fostering practical life skills and values among students. Students will also be able to identify the key components and subjects covered, such as agriculture, home economics, industrial arts, and information and communication technology.
𝐄𝐱𝐩𝐥𝐚𝐢𝐧 𝐭𝐡𝐞 𝐍𝐚𝐭𝐮𝐫𝐞 𝐚𝐧𝐝 𝐒𝐜𝐨𝐩𝐞 𝐨𝐟 𝐚𝐧 𝐄𝐧𝐭𝐫𝐞𝐩𝐫𝐞𝐧𝐞𝐮𝐫:
-Define entrepreneurship, distinguishing it from general business activities by emphasizing its focus on innovation, risk-taking, and value creation. Students will describe the characteristics and traits of successful entrepreneurs, including their roles and responsibilities, and discuss the broader economic and social impacts of entrepreneurial activities on both local and global scales.
How to Setup Warehouse & Location in Odoo 17 InventoryCeline George
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LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UPRAHUL
This Dissertation explores the particular circumstances of Mirzapur, a region located in the
core of India. Mirzapur, with its varied terrains and abundant biodiversity, offers an optimal
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advanced technologies such as GIS (Geographic Information Systems) and Remote sensing to
analyze the transformations that have taken place over the course of a decade.
The complex relationship between human activities and the environment has been the focus
of extensive research and worry. As the global community grapples with swift urbanization,
population expansion, and economic progress, the effects on natural ecosystems are becoming
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significant role in maintaining the ecological equilibrium of our planet.Land serves as the foundation for all human activities and provides the necessary materials for
these activities. As the most crucial natural resource, its utilization by humans results in different
'Land uses,' which are determined by both human activities and the physical characteristics of the
land.
The utilization of land is impacted by human needs and environmental factors. In countries
like India, rapid population growth and the emphasis on extensive resource exploitation can lead
to significant land degradation, adversely affecting the region's land cover.
Therefore, human intervention has significantly influenced land use patterns over many
centuries, evolving its structure over time and space. In the present era, these changes have
accelerated due to factors such as agriculture and urbanization. Information regarding land use and
cover is essential for various planning and management tasks related to the Earth's surface,
providing crucial environmental data for scientific, resource management, policy purposes, and
diverse human activities.
Accurate understanding of land use and cover is imperative for the development planning
of any area. Consequently, a wide range of professionals, including earth system scientists, land
and water managers, and urban planners, are interested in obtaining data on land use and cover
changes, conversion trends, and other related patterns. The spatial dimensions of land use and
cover support policymakers and scientists in making well-informed decisions, as alterations in
these patterns indicate shifts in economic and social conditions. Monitoring such changes with the
help of Advanced technologies like Remote Sensing and Geographic Information Systems is
crucial for coordinated efforts across different administrative levels. Advanced technologies like
Remote Sensing and Geographic Information Systems
9
Changes in vegetation cover refer to variations in the distribution, composition, and overall
structure of plant communities across different temporal and spatial scales. These changes can
occur natural.
Strategies for Effective Upskilling is a presentation by Chinwendu Peace in a Your Skill Boost Masterclass organisation by the Excellence Foundation for South Sudan on 08th and 09th June 2024 from 1 PM to 3 PM on each day.
Beyond Degrees - Empowering the Workforce in the Context of Skills-First.pptxEduSkills OECD
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This document provides an overview of wound healing, its functions, stages, mechanisms, factors affecting it, and complications.
A wound is a break in the integrity of the skin or tissues, which may be associated with disruption of the structure and function.
Healing is the body’s response to injury in an attempt to restore normal structure and functions.
Healing can occur in two ways: Regeneration and Repair
There are 4 phases of wound healing: hemostasis, inflammation, proliferation, and remodeling. This document also describes the mechanism of wound healing. Factors that affect healing include infection, uncontrolled diabetes, poor nutrition, age, anemia, the presence of foreign bodies, etc.
Complications of wound healing like infection, hyperpigmentation of scar, contractures, and keloid formation.
বাংলাদেশের অর্থনৈতিক সমীক্ষা ২০২৪ [Bangladesh Economic Review 2024 Bangla.pdf] কম্পিউটার , ট্যাব ও স্মার্ট ফোন ভার্সন সহ সম্পূর্ণ বাংলা ই-বুক বা pdf বই " সুচিপত্র ...বুকমার্ক মেনু 🔖 ও হাইপার লিংক মেনু 📝👆 যুক্ত ..
আমাদের সবার জন্য খুব খুব গুরুত্বপূর্ণ একটি বই ..বিসিএস, ব্যাংক, ইউনিভার্সিটি ভর্তি ও যে কোন প্রতিযোগিতা মূলক পরীক্ষার জন্য এর খুব ইম্পরট্যান্ট একটি বিষয় ...তাছাড়া বাংলাদেশের সাম্প্রতিক যে কোন ডাটা বা তথ্য এই বইতে পাবেন ...
তাই একজন নাগরিক হিসাবে এই তথ্য গুলো আপনার জানা প্রয়োজন ...।
বিসিএস ও ব্যাংক এর লিখিত পরীক্ষা ...+এছাড়া মাধ্যমিক ও উচ্চমাধ্যমিকের স্টুডেন্টদের জন্য অনেক কাজে আসবে ...
it describes the bony anatomy including the femoral head , acetabulum, labrum . also discusses the capsule , ligaments . muscle that act on the hip joint and the range of motion are outlined. factors affecting hip joint stability and weight transmission through the joint are summarized.
5. Definition
- Casting is defined as forming an object from the mold.
- GPT 8th Edn.
- Something that has been cast in a mold , an object formed by
the solidification of a fluid that has been cast into a refrectory
mold.
- GPT 9th Edn.
6. History
1891 – Martins Technique
- Filled the cavity with wax, removed and invested.
- After burn out poured the molten gold into mold.
-Asgar et al, 1988
1869 – Philbrook introduced the pressure casting method.
- Wax pattern formed directly into mouth and mounted on sprue
- Invested in metal ring and burnout and than alloy melted
Philips Science of Dental Materials- 12th Edn
7. 1907 – Taggart’s presentation in the New York on fabrication of cast inlay
- First reported application of Lost-Wax Technique.
- Soon led to the casting Inlays, onlays, crowns, FPDs and framework of RPDs.
1932 – Classification of gold based alloys.
- Dental material group at the National Bureau of Standards surveyed the alloys
being used and classified as
Type- I (Soft)
Type- II (Medium)
Type- III (Hard)
Type- IV (Extra hard)
1950 – Abrahm Weinstein first produced commercially successful dental gold alloy
Philips Science of Dental Materials- 12th Edn
8. Steps in Casting
1) Preparation of working cast and dies-
Cast : Working cast is a cast that is mounted on an articulator.
Die : It is a model of the individual tooth on which the margins of the wax
pattern are finished.
- Requirements of good casts-
1. Must be free of bubbles
2. Must be free of distortion
3. Must be trimmed
Fundamentals of fixed Prosthodontics – Shillinberg 4th Edn.
9. Two basic working cast and die systems:-
1) Working cast with a separate die
2) Working cast with a removable die
1) Working cast with a separate die:
- Simple means of fabricating a working cast.
- No procedure required to create a die other than making a sectional
cast and full arch cast.
Fundamentals of fixed Prosthodontics – Shillinberg 4th Edn.
10. - Two pour technique is followed
Die is prepared from the first pour
Model is prepared by impression or the second pour of same
impression
Disadvantage:
- Stress during transfer of the was pattern from die to model
- Distortion of impression during removal of first cast
11. Technique:
-Type IV or Type V stone should be used for
fabrication of die
- Impression is washed under running water.
- Measured amount of water is placed in the bowl
- Die impression poured with 50 to 70 g of stone.
- 200 g for full arch impression
- Stone is added in the increments and vibrated.
12. - The tray is tilted to fill the preparation
with stone and reach the stone to the
bottom of the preparation.
- If the large amount of stone is added,
air can be entrapped and creates voids.
- The stone is built up to a height of
approximately 1 inch.
- Allowed to set for 1 hour.
- Cast is separated from the impression.
13. - Super-SeP (Kerr) is applied to protect the
prepared teeth to guard against the erosion when
cast is trimmed.
- There should be no stone duplicating soft tissue in
the periphery beyond the gingiva on cast.
- The cast is held by a base while it is cut down to
form a handle on the die.
- If held by preparation portion chances to get it
chipped.
14. - The handle should be larger in diameter and
octagonal in a cross section.
- The handle should be parallel to the long axis of
the tooth.
- It should approximately 1 inch long in the length to
facilitate a proper hold of the die.
- A pear shaped acrylic bur is used to trim the die
apical to the finish line.
- The apical area should be smooth and free of
ridges.
15. - The contour of the die apical to the finish line should
approximate the root.
- The wax pattern contacts, contours and occlusal morphology
is built up on working casts.
- Dies reserved for the final margination, detail adjustments ,
surface treatments and spruing.
16. 2) Working cast with a removable die:
- Dies that can be removed form the cast.
- Convinient because wax patterns or copings need not be removed from
their respective dies.
Advantages
1. Saves time and effort by using one cast.
2. Eliminates dimentional disvrepencies.
3. Less distortion because not transferred.
Textbook of Operative Dentistry by Vimal Sikri-4th Edn.
17. Disadvantages:
1. Necessity for additional tools and equipments.
It should satisfy three requirments:
1. Must return to their original position.
2. Must remain stable.
3. Must be easy to mount on an articulator.
Two techniques for removable dies
1. Dowel pins
2. Strip technique
18. Dowel pins
- Methods to allow the repositioning of the die in the working cast.
- Most of these oriented in the impression before it is poured or
attached to the underside of the cast.
- Two systems are presented here
1) Straight dowel pins.
2) Pindex system.
Fundamentals of fixed Prosthodontics – Shillinberg 4th Edn.
19. 1) Straight dowel pins:
- Dowel pins is positioned over each prepared tooth in the impression.
- Desired location of the pin can be marked and pins placed after
pouring with stone.
- Most accurate placement can be done by prepositioning the pins
before pouring the stone.
- There are devices made for precise positioning of dowels before
pouring.
- One such device utilizes putty on a movable table to hold an
impression in repeatable.
20. - Wire clips that can be stuck into the periphery of the
impression can be purchased or fashioned from the
orthodontic wire.
- Aneasthetic needles, bobby pins, paper clips, and paper
matches used to orient the dowel pins
21. Technique
- Dowel is placed between the arms of
bobby pin.
- Round side of the dowel in corrugations
and flat side against the flat arm of bobby
pins.
- Bobby pins positioned faciolingually
across the impression so that dowel is
centered over the preparation.
- Straight pin is pushed between the arms
of bobby pins and into the impression on
facial and lingual side.
22. - Dies stone is poured till the knurled end
of the pin.
- Paper clips added to stone and let it set ,
provide retention for base.
- After setting pins removed from the
impression.
- Small ball of utility was is placed on the
tip of dowel.
- 1-inch length and 0.5 inch diameter
plastic tube can be placed to identify after
base pour.
23. - ‘V’ shaped facio-lingual orientation groove
can be cut.
- Stone is then lubricated around each
dowel with petrolatum.
- A wet paper towel is placed into the open
lingual space.
- This will create a complete base for the
cast to be poured.
- After stone is set the cast is removed from
the impression.
24. - Wax at the end is located and removed
- A saw frame with a thin blade is used to
cut through the layer of die stone.
- An instrument handle is used to gently
tap on the end of the dowel to loosen the
die.
25. Pindex System
- Reverse drill press is used to create a
master cast with dies that can be removed
and replaced.
- Impression is poured without positioning
dowel pins.
- Machine accurately drills parallel holes
from the underside of a trimmed cast.
- Impression is poured mm of stone
beyond the edge of the tray.
26. - The bottom of cast trimmed on cast trimmer.
- The facio lingual width of cast should be approx.
20mm
- Pencil used to mark pins on occlusal surface of
teeth.
- Pencil marks are placed under illuminated dot.
27. - Thumbs used to stabilize the cast on work
tooth
- Debris removed from the pinholes with
brush.
- Cynoacrylates cemet is used to lute the pins
in their places.
- Short pin on palatal side and long pin on
buccal side.
28. - Sleeves placed over the pins.
- White on short pins and grey on long pins
- Long pins blocked with utility wax.
- Boxing wax is applied around the cast.
- Poured with stone.
- After setting of stone wax removed from the
pins.
- Pencil marks are made for saw cutting.
- Dies sectioned and removed.
29. Die Spacing:
- Main objective is to create room for the final casting-
cementing medium.
- Done to insure complete seating of the casting.
- Done using insoluble paints.
- Should be applied on the die to cover the axial walls,
cavity floor, and preparation surface short of the
circumferential tie constituents.
- Thickness should be 25 microns.
Modern Operative dentisty by Marzuck
30. WAX PATTERN FABRICATION
According to marzuck:
1. Create a wax mass and carve in the restoration shape.
2. Incrementally build by the restoration using was cones,
triangles, and drops.
3. Fabricate the pattern directly inraorally
4. Anatomic core technique.
Modern Operative dentisty by Marzuck
31. According to Anusavice
1. Direct method of wax pattern fabrication
2. Indirect method of wax pattern fabrication
Philips science of dental materials- 12th Edn.
32. Indications
-Tooth with easy accessibility
-Cavity preparation with minimal proximal extension.
-Cavity preparation where walls are flat, internal line angles are
sharp and gingival bevel is definite.
1) Direct method
Textbook of Operative Dentistry- Vimal sikri 4th Edn.
33. - Hold the stick of wax over the flame
and rotate it rapidly until it becomes
plastic.
- The soften wax shaped approximately
to the prepared cavity.
Materials used in dentistry: S. Mahalaxmi
34. - Insert the wax into the cavity and held
under finger pressure until it solidifies.
- The wax should be allowed to cool
gradually to mouth tempreture.
- Cold carving instrument should be used.
- Withdraw the patern carefully in the long
axis of the tooth
- The pattern shoud be touched as little as
possible with hands to avoid temperature.
Materials used in dentistry: S. Mahalaxmi
35. 2) Indirect method
1) Incremental build up on cast.
2) Dipping method.
1) Incremetal build up:
- Suitable lubricant is applied
- Cusps with their tips are built up by addition of
wax.
- Triangular ridges of cusps are added and the
whole anatomy is produced
36. 2) Dipping Method:
- The die can be dipped repeatedly in the hot liquid
wax
- Fossae and grooves then carved on the bulk of
wax usking PKT no. 1 and no. 4 instruments.
37. - Similar to functionally generated path technique.
- Pattern built with hard wax to the desired shape of the future
restoration.
- The patient is asked to go through all mandibular movements and
positions.
- Functionally generated quaderant tray and fast setting plaster is
carried to wax pattern and impression taken.
Anatomic Core Technique
Modern Operative Dentistry - Marzuck
38. - Anatomic core is tried in the quaderant.
- One die at a time filled with molten wax.
- The anatomic core is removed.
The next die is treated in the same way
39. SPRUING THE PATTERN
- Main objective is to create an inlet for the melt into the
investment mold created by the wax pattern.
- Should be formed when the pattern is on the die.
- It prevents mechanical stress.
- Helps in the proper removal of the molten wax.
- Helps to mount the pattern on the crucible former.
- Generally of three types
- Metal
- Plastic
- Wax
Modern Operative Dentistry - Marzuck
(Manapallil dental materials)
40. Desired characteristic of a sprue former:
1. Sprue former surface should be smooth to prevent any irregular
inlet walls.
2. Should not react with any other ingredient.
3. They should be cylindrical in shape to create perfect rounded inlet.
Textbook of Operative Dentistry- Vimal Sikri 4th Edn.
41. Diameter of the sprue:
- Most important fector.
- Dictates the speed by which the melt enters and fills the mold.
- The sprue diameter should be thicker than thickest part of the pattern.
- The diameter will be 8-18 gauge.
8 – 3mm
18 – 0.8mm
42. Length of the sprue:
- The end of the wax pattern away form the
sprue should be 1/8 – ¼ “ fro the end of the
ring.
- This allows the minimum thickness of
investment.
- Allows escape of mold gases.
- Larger ring, larger should be the sprue.
- Spatial location of pattern also influence the
length of sprue.
1/8 to ¼ “
44. Number of sprue:
- Configurations of pattern affects the number of sprue.
Example:
-Pattern should decrease in dimension going from sprue end to
another
-One sprue in enough.
-If wax pattern have thin area between the sprue and the periphery,
the melt will solidify here.
-In such cases sprue should be used.
45. Location of the sprue:
- Should be attached to the bulkiest part of the
pattern
- This minimizes the effect of released residual
stresses.
- It will also ensure the tinner cross-section of the
mold.
46. - Should be atttahed to the least anatomical areas.
1) Areas of no grooves.
2) Cuspal anatomy
3) Fossae or ridges
- Proximal surface are the ideal location.
47. Angulation of the sprue former:
- Should never directed toward thin, delicate
cross section of the pattern.
- Melt should not hit these areas at 90 ֯ to
avoide fracture failure.
- Should be at 45֯ .
- At right angle it can create reverse flow of
metal.
45 ֯
48. - At right angle also create concavities
in the mold.
Contemporary Fixed Prsothodontics, Rosenteil 4th Edn.
49. The sprue-wax pattern joint:
- Most necessary when high velocity
ingeress is required.
- It should be flared to allow mold to enter
at more speed.
- Flaring gives the non obstructed flow of
molten metal by maximum dimension.
50. Reservior:
- Made 1-2 mm away from the joint.
- Dimension should far exceeding than
the thickest part of the thickest portion
of the pattern.
- Shape should be round or oval
Reservior
51. Venting:
- Always release of gases occur in the investment.
- This can be due to thickness of the investment.
- In such cases the proper investment should be chosen to give away the
waxes
- Proper thickness of investment and porosity in investment provide
adequate venting.
52. Removal of wax pattern & Sprue former:
- Possibilty of stressing the pattern during removal.
- Should be removed in the long axis of the tooth.
First choice:
Use the sprue former to remove the pattern.
Second choice:
Use two fingers on the both sides of the pattern.
53. Third choice:
- Formulate a suitable size of staple from
the paper staple or a wire.
- Staple is attached with help of sticky
wax to the farthest two end of the
pattern.
- It should be 45֯ to the pattern.
- Holding the pattern with staple it can be
removed on long axis of tooth.
54. FORMING THE CRICUBLE
- In most cases it is funnel shaped.
- Connected same way as the sprue is attached
to the pattern.
- Depth and inclination governed by the factors
governs by the diameter of sprue like-
Alloy density
Machine energy
Velocity
Porosity of investment.
55. - Made up of rubber, metal, or plastic.
- Modifications can be done by adding waxes.
- Junction between the sprue and crucible former is
covered with waxes.
56. Surface treatment of pattern
- Waxes are hydrophobic in nature.
- Difficult to wet them with water and investment liquid.
- It should be covered completely by investment to record all the details.
- Surface active agents (Soaps) are generally applied to the pattern.
- It reduces the surface tension, encourages the solid component, thus
provide closeness.
- Vibration also can be used during investing.
57. Placing the ring liner
- A ring liner is placed inside of the casting
ring.
- It should be short at one end.
- Earlier asbestos liners were used.
- Its use has been discontinued due to
health hazard from breathing its dust
Types of Non asbestos ring liners Used are:
— Fibrous ceramic aluminous silicate
— Cellulose (paper)
— Ceramic-cellulose combination
58. Functions of the Ring Liner:
1. Allows for mold expansion (acts as a cushion)
2. When the ring is transferred from the furnace to the casting machine
it reduces heat loss as it is a thermal insulator
3. Permits easy removal of the investment after casting.
59. INVESTMENT OF THE WAX PATTERN
- Main objective is to catch all the details of the
wax pattern.
- Investing materials
1) Gypsum bonded
2) Phosphate bonded
3) Ethyl silica bonded
60. Principles of investing:
1) Choice of the ring:
- For hygroscopic expansion technique- rubber ring is used.
- For thermal expansion- metal ring.
- Diameter and length of the ring should be selected to allow for
the desired dimension of the mold walls.
61. 2) Preparation of the ring for non-confinement of the investment
expansion:
- in such cases rubber ring is used.
3) Assembling the ring and the crucible former:
- For low fusing class I and class II alloys it is possible to attach the stone
die to wax pattern and invest them together.
4) Preparation of the investment to mix:
- Distilled water or indicated liquid is used for mixing.
62. - Mechanical vaccum mixing used to lessen voids.
5) Adding the investment mix to the wax pattern
and filling the ring.
- Done under vibration of vaccum.
6) Facilitating the desired setting through
hygroscopic expansion during hardening the
investment.
63. 7) Removal of solid or non burnable sprue
former:
- Crucible former detached from the ring.
- The sprue fomer if not going to be left in the
investment wax complex, removed.
64. Investment of the pattern
- Pattern invested with suitable investment material.
Two methods for investing the prepared pattern:
1) Manual investing
2) Vaccum investing
Textbook of Operative Dentistry: Vimal Sikri 4th Edn.
65. 1) Manual investing:
- Water and powder incorporated in an appropriate ratio in a rubber
bowl.
- With hand spatula the mix is mixed in the rotating motion.
- Mixing is done for 1 minute.
- Placed on the vibrating table and stirred very slowly for 0 sec to
remove trapped air.
- Investment poured into the pattern.
- Allowed to set for 1 hour
66. 2) Vaccum mixing:
- Investment is mixed in the vaccum mixer and
pattern invested under vaccum.
- Vaccum investing equipment available in the
market.
Method:
- Invest and water is taken bowl.
- Mix is placed in mixing unit.
67. - Unit is motor driven, and the air evacuated by
means of tube attached to the mixing unit form the
vaccum pump.
- Evacuation of air will reduce the possibility of
bubble formation
68. BURNOUT OF THE WAX
- It is the heating of the casting ring with the
invested wax pattern in the furnace.
Placement of ring in the burnout furnace:
- The invested casting ring is placed in a room
temperature.
- First placed on a rubber ceramic tray in
furnace, facing down to drain the wax.
- This slows molten wax to flow out.
Materials used in dentisty: S. Mahalaxmi
69. - Temperature is than increased , when reaches to 300 degree, the ring
is inverted.
- This allows the circulation of oxygen within the oven in the mold
cavity.
- Also inverting prevents the carbon formation
70. Two Stage burnout procedure
- Depend upon the sprue former used.
- For plastic sprue the two stage burnout is used.
- Plastic needs time to melt, first stage allows the softening of the
plastic.
- Second stage, the ring is inverted and placed with the sprue end
downward to allow total elimination.
71. Burnout tempratures
Type of investment Type of
expansion
Maximum temp. Time
Gypsum bonded Hygroscopic 500 C / 900 F 1 hr.
Gypsum bonded Thermal 700 C / 1200 F 1 hr
Phosphate bonded Thermal 700 – 1030 C 45
mins
Ethyl silica bonded Thermal 1090- 1130 C
72. Procedure for wax burnout
- Casting ring should be placed at the room temperature.
- The temperature should be gradually increased.
- Rapid heating generate steam, causing flaxing of the mold walls.
- Investments are poor conductors of heat.
- Placing directly in the heated furnace will result in the rapid change in
the temp. that can result in the flaxing or cracking the investment.
- Ring should be placed in the furnace for 45-90 minutes.
73. Time lapse b/w burnout and the wax:
- 1 minute may be allowed between removal of casting ring from the
burnout.
- To prevent the heat loss the casting ring is maintained at the max
temp.
74. Casting crucibles
-The alloy during melting placed in the
crucible.
- The crucible should
1. Not cause reaction with the alloy
resulting in contamination of alloy.
2. It should withstand the temp. of the
melting torch.
75. Crucibles used for dif types of alloys
Clay – High noble and noble alloys
Carbon – Noble alloys for crown
Aluminium – High fusing alloys
Quartz – High fusing alloys
- carbon crucible should not be used with high palladium, silver-palladium,
nickel–chromium, and cobalt-chromium alloys.
76. MELTING OF THE ALLOY
- Alloy should be heated as quickly as possible
to a completely molten state above its liquid
temp.
- At the same time, it should not be so hot
that it begins to oxidize or that crystallization
is delayed when it reaches the extremities of
the mold cavity.
- Gold alloys ball up and have a mirror like
shining surface that appears to be spinning.
77. Methods of casting
1) Torch melting
2) Vaccum casting machine
3) Casting using centrifugal machine
4) Induction casting machine
5) Direct current arc melting
78. 1) Torch melting
- Fuel mostly used is a mixtures of natural or artificial gas
and air.
- The alloy melted using the reducing flame of gas torch.
- Torches are of two types
1) Single artificial tip:
- Concentrate more heat on the area.
2) Multiorifice tip:
- Distribute the heat over wider area enabling uniform
heating
- Used for casting metal ceramic.
79. Mixing zone
Cumbusion zone
Reducing zone
Oxidizing zone
Zones of flame
A properly adjusted torch develops adequate temperatures
of 870°C–1000°C for melting dental alloys whose melting
ranges are within these temperatures.
80. 1) Mixing zone:
- Long cone emerging directly from the
nozzle of the torch.
- Air and gases are mixed in this zone
2) Combustion zone:
-Immediately surrounding the inner zone.
- Green in color and known as combustion
zone
-Gas and air are partially burned.
81. 3) Reducing zone:
- Blue in color and located outside the combustion zone.
- Hottest part of the flame
- kept in contact with the alloy.
4) Oxidizing zone:
- Outermost zone of the flame
- Not used to melt the alloy
82. Centrifugal casting machine
- Various designs are available
- Molten metal forced into the mold by
centrifugal force.
- Force is created by spring wound.
- It is winding the arm of the casting
machine 2–5 turns.
- The crucible is attached to the free
arm also known as the broken arm.
83. - Spring is wound and locked.
- Once the alloy is melted after ring placement the spring is released.
- This initiates the rotational motion.
- Molten metal moves to the mold.
84. Induction casting
- Melted in electrical induction furnace
- Currents generated within metal and
resistance lead to heating of the metal.
- Induction heater consist of electromagnet
is used.
- High frequency current will melt the metal.
85. Arc melting
- Alloy is vaccum melted and cast by pressure in an
argon atmostphere.
- Currents produced between 2 electrodes.
- Temp generates are 4000 C .
- Alloy melts very quickly in this method.
- One of the advantage as alloy melts within
seconds.
Materials used in dentistry: S. Mahalaxmi
86. Vaccum Casting
- Titanium and its alloys require vaccum are
heating argon pressure casting.
- Melting point for titanium is 1071 C
- Vaccum is applied beneath the casting ring
and molten alloy can drawn into by suction
87. Divesting
- Removal of casting from the investment
mould.
- After divesting all the casting undergoes three
main steps
1) Quenching
2)Sand blasting.
3)Pickling.
88. 1) Quenching:
- For noble metal alloys the ring is removed and
immediately quenched in water.
- Quenching enables the metal to burnish.
- Investment undergo violent reaction resulting
in the crumbling of the granular investment.
- This makes the casting to be removed easily.
89. 2) Sand blasting:
- The oxide layer and any remaining
particles of investment are removed by
lightly air abrading.
- All surfaces abraded with a 50-μm
abrasive.
90. 3) Pickling:
- After removal the castings covered by dark
oxides.
- Removed by the process called pickling.
- This involves soaking the casting in a hot acid
solution for several minutes.
- 50 % HCL is recommended for pickling.
91. Finishing & Polishing
- Clean all the debris, inner surface should be inspected first.
- Should never be tried on stone until inner surface is evaluated.
Technique:
- Gold being soft should be finished at slow speed.
- Initial contouring should be done with carbide burs.
- Silicone carbide green stone or heatless polymer stone.
- Finishing is done with Aluminium oxide (pink) stone or medium grade
impregnated rubber cups, wheels and points.
92. CASTING DEFECTS
- Errors in the procedure often results in defective castings.
- The casting in such a case may not fit or may have poor esthetic and
mechanical properties.
- Innumerable steps in casting may create many problems in casting
leads to casting defects.
1) Distortion
2) Surface roughness and other surface defects
3) Porosity
4) Incomplete casting
5) Contaminated casting
93. Distortion
- Distortion of wax pattern may occur during removal.
Causes:
- Thermal changes
- Improper handling during removal
- Distortion during storage
- Relaxation of stresses
- Distortion during removal of die
Textbook of Operative Dentistry: Vimal Sikri 4th ed
94. Prevention:
- Hard wax should be used, because soft wax is more susceptible to
temperature changes.
- Careful handling during removal of the pattern.
- Stresses can be minimized by softening the wax at uniform temp. of 50
C
- Wax should be added in smaller increments.
- Should be invested immediately.
95. Surface Roughness
- Surface roughness defined as finely spaced surface
imperfections.
Causes:
- Air bubbles on the wax pattern.
- Too rapid heating during burn-out.
- Higher water powder ratio gives rough casting.
- Prolonged heating of pattern.
Textbook of Operative Dentistry: Vimal Sikri 4th ed
96. - Foreign body inclusion.
- Larger particle size of silica.
- Too high or too low casting pressure.
- Excess surfactant.
Prevention:
- Proper burn out and adequate heating time.
- Smaller particle size of silica in the investment.
- Pressure should be 15 lbs/Sq. inch
- Proper water powder ratio.
- Air bubbles can be avoided by vibrating the mixture before and after
mixing
97. Noduls in casting:
- Large nodules due to air trapped during
casting.
- Multiple nodules because of inadequate
vaccum during investing.
- Improper brush technique
- Lack of surfactant
- Nodules on occlusal surface can be
because of excessive vibration.
Contemporary fixed prosthodontics: Rosenstiel 5th edn.
98. Avoided by:
- Even minute nodules can limit the seating of the
casting.
- When they are large or situated on a margin, they
usually necessitate remaking of the restoration.
- A binocular microscope is extremely helpful for
detecting and removing nodules.
99. - When small nodules present, they can often
be removed with a No. 4 or No. 2 round bur.
- A slight excess of metal should be removed
to ensure that the nodule does not interfere
with complete seating.
- Can be avoided by careful investing
technique.
- Use of a surfactant
- Vacuum spatulation, and careful coating of
the wax pattern with investment
Contemporary fixed prosthodontics: Rosenstiel 5th edn.
100. Fins:
- Caused by cracks in the investment that
have been filled with molten metal.
- Excessive casting force.
- Steam generated from too-rapid heating.
- Reheating an invested pattern.
Contemporary fixed prosthodontics: Rosenstiel 5th edn.
101. - Improperly situated pattern (too close to the
periphery of the casting ring)
- Rough handling of the ring after investing
- Premature heating (mold still wet)
- Increased water-to-powder ratio
102. Porosity
- It can be internal or external.
- External porosity can cause discoloration.
- Severe porosity at the tooth restoration
interphase can even cause secondary caries.
- Internal porosity weakens the restoration.
103. - They are categorized as
1) Solidification defects
A. Localized shrinkage porosity
B. Suck back porosity
C. Microporosity
2) Porosity due to gases
A. Pinhole porosity
B. Gas inclusions
3) Sub surface porosity
4) Back pressure porosity
104. 1) Localized shrinkage porosity:
- Usually found near the sprue-
casting junction.
- Occurs when the cooling sequence is
increased and the sprue freezes
before the rest.
- Allows main molten metal to flow
into the mould.
- If sprue solidifies before the rest of
casting
105. Avoided by-
A. Using sprue of correct thickness
B. Attach sprue to thickest part of pattern
C. Flaring the sprue at the point of attachment or placing a reservoir
close to the wax pattern.
D. Placing sprue in such a way so that a hot spot formation is avoided.
E. Not using an excessively long sprue
F. Reducing the mold-melt temperature difference.
Textbook of operative dentistry : Vimal sikri 4th Edn.
106. 2) Suckback porosity:
- Variation of shrink spot porosity.
- External void on crown apposite to sprue.
- Hot spot created by the hot metal impinging on
the mold wall.
- Sprue already solidified result in suck back
porosity.
- Avoided by reducing temp. different between
mold and molten alloy.
107. 3) Micro porosity:
- Fine irregular void within casting
- Occur when casting cools too rapidly.
- Temp should be reduced gradually
108. Porosities due to gases-
1) Pin hole porosity:
- The metal absorbs gases when it is in molten state
- Upon solidification, the absorbed gases are expelled
- Casues tiny voids.
2) Gas inclusion porosity:
- Gas occluded from a poorly adjusted blowpipe flame.
- If the reducing zone of the flame is not used.
- larger than the pin hole type
109. 2) Back Presure porosity:
- Caused by inadequate venting.
- Trapped gases within investment.
- Metal enters into mold they are pushed out and create pressure.
Avoided by:
- Using adequate casting force
- Using investment of adequate porosity
- Place pattern not more than 6 to 8 mm away from the end of the ring.
- Providing vents in large castings
110. 3) Subsurface porosity:
- The exact reason for this has not been established.
- May be due to the simultaneous nucleation of solid grains.
- Can be avoided by controlling the rate at which the molten metal
enters the mold.
111. Incomplete casting
Causes:
- Insufficient alloy used.
- Alloy not able to enter thin parts of mold
- Mold is not heated to casting temperature.
- Premature solidification of alloy.
- Sprues are blocked with foreign bodies.
- Back pressure due to gases in mold cavity.
- Low casting pressure.
- Alloy not sufficiently molten or fluid.
112. - If compensation for shrinkage of alloy is not
done by adequate expansion of mold cavity.
- shrinkage of the impression material.
- If an area of wax is too thin (less than 0.3
mm)
- insufficient casting force
- inadequate heating of the metal
113. Avoided by:
- Use larger size of sprue former.
- Have casting temperature at least 150°F (57°C) above fusion
temperature of alloy.
- Mold should soak heat for approximately one hour at burnout
temperature.
- Mold should be removed from burnout oven and casting completed
within one minute.
- Use the adequate amount of force for casting
114. Shiny casting with rounded margins:
- When the wax is not completely eliminated, it
combines with oxygen or air in the mold cavity
forming carbon monoxide.
- gas prevents the oxidation of the surface of
the casting gold with the result the casting to
be shiny.
- The formation of gas in the mold is so rapid
that it also has a back pressure effect.
115. Pits in casting:
- Caused by residual debris in mold.
- Use of dirty wax.
- Loose debris in crucible.
Avoided by:
- Use clean, new wax for patterns and sprue.
- Use clean crucible for each casting.
116. Contaminated casting
A casting can be contaminated due to:
1. Oxidation, caused by:
—Overheating the alloy
—Use of oxidizing zone of flame
—Failure to use flux
2. Sulphur compounds, formed by the breakdown of the
investment when the ring is overheated.
Avoid by
—Not overheating alloy
—Use reducing zone of the flame
—Use flux.
117. Discoloration
- Contamination with copper during pickling.
- Contamination with mercury.
- By avoiding the use of steel tongs to hold casting during
pickling.
- If used then the tips of the tongs should be covered with
rubber.
- Castings should never be placed with amalgam dies or kept
on a table where amalgam scrap is present
118. Black Casting
Can be due to two reasons:
1. Overheating the investment above 700°C causes it to decompose liberating
sulphur or sulphur compounds. They readily combine with the metals in
gold alloy forming a sulfide film. This gives a dark casting which cannot be
cleaned by pickling.
2. A black casting can be also due to incomplete elimination of the wax pattern,
as a result of heating the mold at too low temperature. A carbonized wax
remains which sticks to the surface of the casting. It can be removed by
heating over a flame.