This seminar discusses casting defects in dentistry. It begins with an introduction to casting and defines casting as forming an object from a mold using a molten material. It then discusses common casting defects like distortion, surface roughness, porosity, and incomplete casting. Specific causes of each defect are explained like distortion occurring from wax shrinkage or investment expansion. Prevention methods are also provided, such as slow heating of investments to avoid surface roughness from cracking. Overall, the seminar provides an overview of casting defects and their causes and prevention in dental prosthodontics.
Casting defects/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
Casting defects/cosmetic dentistry course by Indian dental academyIndian 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.
This document discusses common casting defects in dentistry, their causes, and methods to prevent them. It begins by classifying defects and dimensions inaccuracies. It then examines specific defects like distortion, surface roughness, porosities, incomplete castings, and discolored castings. For each defect, it outlines potential causes such as wax pattern issues, improper investments, heating/cooling rates, and gas entrapment. It provides tips to control defects like using the proper water/powder ratio, venting molds, and casting procedures. The conclusion emphasizes that following methods can avoid defects and produce high quality castings for clinical success.
This document discusses common casting defects in dentistry, their causes, and methods to prevent them. It begins by classifying defects and dimensions inaccuracies. It then examines specific defects like distortion, surface roughness, porosities, incomplete castings, and discolored castings. For each defect, it outlines potential causes such as wax pattern issues, improper investments, heating/cooling rates, and gas entrapment. It provides tips to control defects like using the proper water/powder ratio, venting molds, and casting procedures. The conclusion emphasizes that following methods can avoid defects and produce high quality castings for clinical success.
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 casting defects that can occur during the dental casting process. It begins by classifying casting defects according to authors Philips and Rosensteil. Common defects include distortion, porosity, incomplete details, and surface irregularities. The document then examines specific defects in more detail such as air bubbles, water films, heating issues, liquid to powder ratios, and foreign bodies. It provides causes and ways to prevent common defects. In conclusion, the document emphasizes that casting defects can usually be avoided by strict adherence to established casting procedures and techniques.
Casting procedures /certified fixed orthodontic courses by Indian dental aca...Indian dental academy
Page 17
Casting procedures
The document discusses the procedures for dental castings using the lost wax technique. It covers preparation of the master die from dental stone, fabrication of the wax pattern, design of the sprue and investing procedure. The key steps include:
1. Preparing an accurate wax pattern on the stone die with sprues attached in strategic locations.
2. Investing the pattern in a specialized dental investment material like gypsum or phosphate bonded investment using vacuum mixing.
3. Allowing the investment to set fully before slowly heating it to burn out the wax pattern, leaving a mold to pour the molten dental alloy into.
4. Careful control of
Casting defects/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
Casting defects/cosmetic dentistry course by Indian dental academyIndian 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.
This document discusses common casting defects in dentistry, their causes, and methods to prevent them. It begins by classifying defects and dimensions inaccuracies. It then examines specific defects like distortion, surface roughness, porosities, incomplete castings, and discolored castings. For each defect, it outlines potential causes such as wax pattern issues, improper investments, heating/cooling rates, and gas entrapment. It provides tips to control defects like using the proper water/powder ratio, venting molds, and casting procedures. The conclusion emphasizes that following methods can avoid defects and produce high quality castings for clinical success.
This document discusses common casting defects in dentistry, their causes, and methods to prevent them. It begins by classifying defects and dimensions inaccuracies. It then examines specific defects like distortion, surface roughness, porosities, incomplete castings, and discolored castings. For each defect, it outlines potential causes such as wax pattern issues, improper investments, heating/cooling rates, and gas entrapment. It provides tips to control defects like using the proper water/powder ratio, venting molds, and casting procedures. The conclusion emphasizes that following methods can avoid defects and produce high quality castings for clinical success.
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 casting defects that can occur during the dental casting process. It begins by classifying casting defects according to authors Philips and Rosensteil. Common defects include distortion, porosity, incomplete details, and surface irregularities. The document then examines specific defects in more detail such as air bubbles, water films, heating issues, liquid to powder ratios, and foreign bodies. It provides causes and ways to prevent common defects. In conclusion, the document emphasizes that casting defects can usually be avoided by strict adherence to established casting procedures and techniques.
Casting procedures /certified fixed orthodontic courses by Indian dental aca...Indian dental academy
Page 17
Casting procedures
The document discusses the procedures for dental castings using the lost wax technique. It covers preparation of the master die from dental stone, fabrication of the wax pattern, design of the sprue and investing procedure. The key steps include:
1. Preparing an accurate wax pattern on the stone die with sprues attached in strategic locations.
2. Investing the pattern in a specialized dental investment material like gypsum or phosphate bonded investment using vacuum mixing.
3. Allowing the investment to set fully before slowly heating it to burn out the wax pattern, leaving a mold to pour the molten dental alloy into.
4. Careful control of
The document discusses common casting defects that can occur with the lost wax technique, including distortion, surface roughness, porosity, and incomplete detail. Distortion is often due to uneven expansion of the investment material around the wax pattern. Surface roughness and irregularities are caused by factors like excessive investment heating rates or improper liquid to powder ratios. Porosity issues include localized shrinkage near the sprue, microporosity from rapid solidification, and gas or pinhole inclusions trapped during solidification. Proper control of casting parameters can help minimize these defects.
Lab steps mould preparation to finish/ dental crown & bridge 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
Casting Defects Analysis in Foundry and Their Remedial Measures with Industri...iosrjce
In this current scenario of globalization, foundries play a key role for manufacturing industries as
they are the major source of castings. As a key industry a foundry’s performance should be effectively high in
terms of production with minimum number of rejections. Castings are the major inputs for most industrial
products hence foundry industry is most indispensable. Casting is an integrated process considered as an
artwork with experienced professionals for high quality yield, even then in highly controlled environment
defects are dominant to take place leading to rejections, contrary to rejections a foundry’s key attempt is to
satisfy the demands neglecting quality levels. The challenges of casting defects are to be identifiedand
minimized for effective castings. This study provides an intense knowledge of critical casting defects and their
root cause analysis. In this paper efforts are made to achieve technically feasible remedies for minimizing
several casting defects and improving the quality of castings which will serve as control measures for quality
control professionals with zero defect concepts
Casting Defects Analysis in Foundry and Their Remedial Measures with Industri...AVINASH JURIANI
In this current scenario of globalization, foundries play a key role for manufacturing industries as they are the major source of castings. As a key industry a foundry's performance should be effectively high in terms of production with minimum number of rejections. Castings are the major inputs for most industrial products hence foundry industry is most indispensable. Casting is an integrated process considered as an artwork with experienced professionals for high quality yield, even then in highly controlled environment defects are dominant to take place leading to rejections, contrary to rejections a foundry's key attempt is to satisfy the demands neglecting quality levels.
This document discusses casting defects found in industrial case studies and proposes remedial measures. It begins by introducing the importance of minimizing casting defects for foundry industries. Nine common casting defects are then analyzed: blowholes, shrinkage, hot tears/cracks, lamination, lumps, sand inclusion, flashes, mismatch, and misrun. For each defect, an industrial case study example is provided along with the likely causes and recommended remedial measures. The aim is to provide foundry professionals with knowledge of casting defects and how to control factors to improve quality and reduce rejections. In conclusion, analyzing defects and identifying causes and solutions can help increase casting yield for industries.
Dental Lab steps from mould preparation to finish/ 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.
ADVANCED TECHNIQUES IN CASTING DEFECTS AND REJECTION ANALYSIS: A STUDY IN AN ...ijiert bestjournal
Casting process is the most widely used process in manufacturing industries especially in automotive products. Production of casting involves various pr ocesses like pattern making,molding,and core maki ng and melting. It is very difficult to produce defect fre e castings. A defect may be the result of a single cause or a combination of causes. The castings may have one or more defects. Foundries are still using trial and error methods to solve quality problems. There are benefi ts of using a more disciplined approach to define,identify and determine the root cause of the defect which is an expensive and error-prone process. This project is about new devolvement for identification of defects for 4 R cylinder block which is presently having a 40% or more percent rejection in Kirloskar ferrous industrial l td,Solapur. This project also presents a methodolo gy in rejection level percent by using scientific study o n casting defects. Various casting quality improvement techniques such as;P roduct Process Search analysis (PPS) Inspection method,Design of Experiment (DOE),and by using a Casting simulation software and by finding out the c ause-effect diagram. This project presents a review on literature of different methods adopted by many foundries to reduce the percent of rejecti on. A new approach is proposed which may be helpful for f oundries for controlling and reducing the defects.
Formwork is a temporary structure used to contain freshly poured concrete and shape it to the required dimensions. Proper formwork design and construction is critical to ensure concrete quality and structural performance. Common causes of formwork failure include improper stripping, inadequate bracing, excessive vibration, unstable supports, and poor concrete placement control. To prevent failures, formwork should be carefully inspected for defects, properly braced and supported, and able to withstand anticipated loads without excessive deformation. Worker safety must also be a top priority during all formwork operations.
This document discusses various types of casting defects that can occur during dental prosthesis fabrication. The main types discussed are distortion, surface roughness/irregularities, porosities, and incomplete/missing details. Distortion can be caused by mishandling wax patterns or uneven investment expansion. Surface issues result from improper investing techniques or foreign substances in the mold. Porosities form due to solidification shrinkage, trapped gases in the alloy, or improper venting of the mold. Following investing and casting best practices can help prevent most defect issues.
The document discusses various defects that can occur in adhesive coatings such as oozing, blistering, cratering, cracking, contamination, and peeling. It provides examples and descriptions for each defect type. Potential causes are outlined for many of the defects, including applying too soft an adhesive, exposure to moisture after coating, using low quality or old adhesive, applying the coating too rapidly, coating at too high a temperature, and electrostatic charges attracting dirt to the coated surface. Remedies are suggested for some defects, such as using a higher quality adhesive and allowing adequate drying time between coating and exposure to other conditions.
This document discusses dental casting and investment materials. It defines casting as the process of replicating a wax dental restoration pattern in metal using the lost wax technique. There are three main types of investment materials used: calcium sulfate-bonded, phosphate-bonded, and silica-bonded. Each has specific properties and temperature limits suitable for different alloy types and restorations. The casting process involves making a wax pattern, investing it, burning out the wax, and pouring molten alloy into the mold. Common casting defects that can occur include distortion, porosity, roughness, and incomplete casting if the procedure is not followed correctly.
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 an overview of the casting process used in dentistry. It discusses the history of lost wax casting techniques dating back to the Bronze Age. The key steps of the casting procedure are described, including making the wax pattern, adding a sprue, investing in a refractory material, and burning out the wax prior to casting. Common casting defects are also outlined relating to distortion, discoloration, porosities and other issues. Causes of defects are correlated to specific steps in the procedure. Details are provided on factors that influence optimal wax pattern design, sprue design and investment selection and parameters.
This document discusses debonding in orthodontics. It begins by introducing the process of debonding orthodontic brackets and different debonding instruments. It then provides a detailed overview of clinical debonding procedures for different bracket materials like steel, ceramic, and bonded lingual appliances. Methods such as pliers, laser debonding, and thermal debonding are described. The document also discusses removing residual adhesive, evaluating adhesive remnant, and considers the influence of debonding instruments on the enamel surface.
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.
Academic presentation prepared for the final professional of BDS. The presentation talks about casting and investing techniques used in the Conservative Dentistry and Endodontics.
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.
Study of Corrosion Due to Soil Non-Governance and Environmental Factors ...IRJET Journal
The document discusses corrosion that can occur on ghatams (clay percussion instruments) due to environmental and soil factors. Ghatams contain small amounts of metal that can corrode over time when exposed to sweat, dust, water or variations in firing temperature. Different types of corrosion are described, such as stress corrosion cracking from sweat accumulation, pitting corrosion from contact with stagnant fluids, and intergranular corrosion if the clay-metal composition contains impurities. Proper soil governance and controlling environmental exposure factors like dust, water and chloride are important to prevent corrosion and maintain the structural integrity and rhythmic tones of ghatams over long-term use.
Bonding in orthodontics /certified fixed orthodontic courses by Indian dental...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
Electric vehicle and photovoltaic advanced roles in enhancing the financial p...IJECEIAES
Climate change's impact on the planet forced the United Nations and governments to promote green energies and electric transportation. The deployments of photovoltaic (PV) and electric vehicle (EV) systems gained stronger momentum due to their numerous advantages over fossil fuel types. The advantages go beyond sustainability to reach financial support and stability. The work in this paper introduces the hybrid system between PV and EV to support industrial and commercial plants. This paper covers the theoretical framework of the proposed hybrid system including the required equation to complete the cost analysis when PV and EV are present. In addition, the proposed design diagram which sets the priorities and requirements of the system is presented. The proposed approach allows setup to advance their power stability, especially during power outages. The presented information supports researchers and plant owners to complete the necessary analysis while promoting the deployment of clean energy. The result of a case study that represents a dairy milk farmer supports the theoretical works and highlights its advanced benefits to existing plants. The short return on investment of the proposed approach supports the paper's novelty approach for the sustainable electrical system. In addition, the proposed system allows for an isolated power setup without the need for a transmission line which enhances the safety of the electrical network
KuberTENes Birthday Bash Guadalajara - K8sGPT first impressionsVictor Morales
K8sGPT is a tool that analyzes and diagnoses Kubernetes clusters. This presentation was used to share the requirements and dependencies to deploy K8sGPT in a local environment.
The document discusses common casting defects that can occur with the lost wax technique, including distortion, surface roughness, porosity, and incomplete detail. Distortion is often due to uneven expansion of the investment material around the wax pattern. Surface roughness and irregularities are caused by factors like excessive investment heating rates or improper liquid to powder ratios. Porosity issues include localized shrinkage near the sprue, microporosity from rapid solidification, and gas or pinhole inclusions trapped during solidification. Proper control of casting parameters can help minimize these defects.
Lab steps mould preparation to finish/ dental crown & bridge 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
Casting Defects Analysis in Foundry and Their Remedial Measures with Industri...iosrjce
In this current scenario of globalization, foundries play a key role for manufacturing industries as
they are the major source of castings. As a key industry a foundry’s performance should be effectively high in
terms of production with minimum number of rejections. Castings are the major inputs for most industrial
products hence foundry industry is most indispensable. Casting is an integrated process considered as an
artwork with experienced professionals for high quality yield, even then in highly controlled environment
defects are dominant to take place leading to rejections, contrary to rejections a foundry’s key attempt is to
satisfy the demands neglecting quality levels. The challenges of casting defects are to be identifiedand
minimized for effective castings. This study provides an intense knowledge of critical casting defects and their
root cause analysis. In this paper efforts are made to achieve technically feasible remedies for minimizing
several casting defects and improving the quality of castings which will serve as control measures for quality
control professionals with zero defect concepts
Casting Defects Analysis in Foundry and Their Remedial Measures with Industri...AVINASH JURIANI
In this current scenario of globalization, foundries play a key role for manufacturing industries as they are the major source of castings. As a key industry a foundry's performance should be effectively high in terms of production with minimum number of rejections. Castings are the major inputs for most industrial products hence foundry industry is most indispensable. Casting is an integrated process considered as an artwork with experienced professionals for high quality yield, even then in highly controlled environment defects are dominant to take place leading to rejections, contrary to rejections a foundry's key attempt is to satisfy the demands neglecting quality levels.
This document discusses casting defects found in industrial case studies and proposes remedial measures. It begins by introducing the importance of minimizing casting defects for foundry industries. Nine common casting defects are then analyzed: blowholes, shrinkage, hot tears/cracks, lamination, lumps, sand inclusion, flashes, mismatch, and misrun. For each defect, an industrial case study example is provided along with the likely causes and recommended remedial measures. The aim is to provide foundry professionals with knowledge of casting defects and how to control factors to improve quality and reduce rejections. In conclusion, analyzing defects and identifying causes and solutions can help increase casting yield for industries.
Dental Lab steps from mould preparation to finish/ 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.
ADVANCED TECHNIQUES IN CASTING DEFECTS AND REJECTION ANALYSIS: A STUDY IN AN ...ijiert bestjournal
Casting process is the most widely used process in manufacturing industries especially in automotive products. Production of casting involves various pr ocesses like pattern making,molding,and core maki ng and melting. It is very difficult to produce defect fre e castings. A defect may be the result of a single cause or a combination of causes. The castings may have one or more defects. Foundries are still using trial and error methods to solve quality problems. There are benefi ts of using a more disciplined approach to define,identify and determine the root cause of the defect which is an expensive and error-prone process. This project is about new devolvement for identification of defects for 4 R cylinder block which is presently having a 40% or more percent rejection in Kirloskar ferrous industrial l td,Solapur. This project also presents a methodolo gy in rejection level percent by using scientific study o n casting defects. Various casting quality improvement techniques such as;P roduct Process Search analysis (PPS) Inspection method,Design of Experiment (DOE),and by using a Casting simulation software and by finding out the c ause-effect diagram. This project presents a review on literature of different methods adopted by many foundries to reduce the percent of rejecti on. A new approach is proposed which may be helpful for f oundries for controlling and reducing the defects.
Formwork is a temporary structure used to contain freshly poured concrete and shape it to the required dimensions. Proper formwork design and construction is critical to ensure concrete quality and structural performance. Common causes of formwork failure include improper stripping, inadequate bracing, excessive vibration, unstable supports, and poor concrete placement control. To prevent failures, formwork should be carefully inspected for defects, properly braced and supported, and able to withstand anticipated loads without excessive deformation. Worker safety must also be a top priority during all formwork operations.
This document discusses various types of casting defects that can occur during dental prosthesis fabrication. The main types discussed are distortion, surface roughness/irregularities, porosities, and incomplete/missing details. Distortion can be caused by mishandling wax patterns or uneven investment expansion. Surface issues result from improper investing techniques or foreign substances in the mold. Porosities form due to solidification shrinkage, trapped gases in the alloy, or improper venting of the mold. Following investing and casting best practices can help prevent most defect issues.
The document discusses various defects that can occur in adhesive coatings such as oozing, blistering, cratering, cracking, contamination, and peeling. It provides examples and descriptions for each defect type. Potential causes are outlined for many of the defects, including applying too soft an adhesive, exposure to moisture after coating, using low quality or old adhesive, applying the coating too rapidly, coating at too high a temperature, and electrostatic charges attracting dirt to the coated surface. Remedies are suggested for some defects, such as using a higher quality adhesive and allowing adequate drying time between coating and exposure to other conditions.
This document discusses dental casting and investment materials. It defines casting as the process of replicating a wax dental restoration pattern in metal using the lost wax technique. There are three main types of investment materials used: calcium sulfate-bonded, phosphate-bonded, and silica-bonded. Each has specific properties and temperature limits suitable for different alloy types and restorations. The casting process involves making a wax pattern, investing it, burning out the wax, and pouring molten alloy into the mold. Common casting defects that can occur include distortion, porosity, roughness, and incomplete casting if the procedure is not followed correctly.
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 an overview of the casting process used in dentistry. It discusses the history of lost wax casting techniques dating back to the Bronze Age. The key steps of the casting procedure are described, including making the wax pattern, adding a sprue, investing in a refractory material, and burning out the wax prior to casting. Common casting defects are also outlined relating to distortion, discoloration, porosities and other issues. Causes of defects are correlated to specific steps in the procedure. Details are provided on factors that influence optimal wax pattern design, sprue design and investment selection and parameters.
This document discusses debonding in orthodontics. It begins by introducing the process of debonding orthodontic brackets and different debonding instruments. It then provides a detailed overview of clinical debonding procedures for different bracket materials like steel, ceramic, and bonded lingual appliances. Methods such as pliers, laser debonding, and thermal debonding are described. The document also discusses removing residual adhesive, evaluating adhesive remnant, and considers the influence of debonding instruments on the enamel surface.
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.
Academic presentation prepared for the final professional of BDS. The presentation talks about casting and investing techniques used in the Conservative Dentistry and Endodontics.
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.
Study of Corrosion Due to Soil Non-Governance and Environmental Factors ...IRJET Journal
The document discusses corrosion that can occur on ghatams (clay percussion instruments) due to environmental and soil factors. Ghatams contain small amounts of metal that can corrode over time when exposed to sweat, dust, water or variations in firing temperature. Different types of corrosion are described, such as stress corrosion cracking from sweat accumulation, pitting corrosion from contact with stagnant fluids, and intergranular corrosion if the clay-metal composition contains impurities. Proper soil governance and controlling environmental exposure factors like dust, water and chloride are important to prevent corrosion and maintain the structural integrity and rhythmic tones of ghatams over long-term use.
Bonding in orthodontics /certified fixed orthodontic courses by Indian dental...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
Electric vehicle and photovoltaic advanced roles in enhancing the financial p...IJECEIAES
Climate change's impact on the planet forced the United Nations and governments to promote green energies and electric transportation. The deployments of photovoltaic (PV) and electric vehicle (EV) systems gained stronger momentum due to their numerous advantages over fossil fuel types. The advantages go beyond sustainability to reach financial support and stability. The work in this paper introduces the hybrid system between PV and EV to support industrial and commercial plants. This paper covers the theoretical framework of the proposed hybrid system including the required equation to complete the cost analysis when PV and EV are present. In addition, the proposed design diagram which sets the priorities and requirements of the system is presented. The proposed approach allows setup to advance their power stability, especially during power outages. The presented information supports researchers and plant owners to complete the necessary analysis while promoting the deployment of clean energy. The result of a case study that represents a dairy milk farmer supports the theoretical works and highlights its advanced benefits to existing plants. The short return on investment of the proposed approach supports the paper's novelty approach for the sustainable electrical system. In addition, the proposed system allows for an isolated power setup without the need for a transmission line which enhances the safety of the electrical network
KuberTENes Birthday Bash Guadalajara - K8sGPT first impressionsVictor Morales
K8sGPT is a tool that analyzes and diagnoses Kubernetes clusters. This presentation was used to share the requirements and dependencies to deploy K8sGPT in a local environment.
artificial intelligence and data science contents.pptxGauravCar
What is artificial intelligence? Artificial intelligence is the ability of a computer or computer-controlled robot to perform tasks that are commonly associated with the intellectual processes characteristic of humans, such as the ability to reason.
› ...
Artificial intelligence (AI) | Definitio
CHINA’S GEO-ECONOMIC OUTREACH IN CENTRAL ASIAN COUNTRIES AND FUTURE PROSPECTjpsjournal1
The rivalry between prominent international actors for dominance over Central Asia's hydrocarbon
reserves and the ancient silk trade route, along with China's diplomatic endeavours in the area, has been
referred to as the "New Great Game." This research centres on the power struggle, considering
geopolitical, geostrategic, and geoeconomic variables. Topics including trade, political hegemony, oil
politics, and conventional and nontraditional security are all explored and explained by the researcher.
Using Mackinder's Heartland, Spykman Rimland, and Hegemonic Stability theories, examines China's role
in Central Asia. This study adheres to the empirical epistemological method and has taken care of
objectivity. This study analyze primary and secondary research documents critically to elaborate role of
china’s geo economic outreach in central Asian countries and its future prospect. China is thriving in trade,
pipeline politics, and winning states, according to this study, thanks to important instruments like the
Shanghai Cooperation Organisation and the Belt and Road Economic Initiative. According to this study,
China is seeing significant success in commerce, pipeline politics, and gaining influence on other
governments. This success may be attributed to the effective utilisation of key tools such as the Shanghai
Cooperation Organisation and the Belt and Road Economic Initiative.
Optimizing Gradle Builds - Gradle DPE Tour Berlin 2024Sinan KOZAK
Sinan from the Delivery Hero mobile infrastructure engineering team shares a deep dive into performance acceleration with Gradle build cache optimizations. Sinan shares their journey into solving complex build-cache problems that affect Gradle builds. By understanding the challenges and solutions found in our journey, we aim to demonstrate the possibilities for faster builds. The case study reveals how overlapping outputs and cache misconfigurations led to significant increases in build times, especially as the project scaled up with numerous modules using Paparazzi tests. The journey from diagnosing to defeating cache issues offers invaluable lessons on maintaining cache integrity without sacrificing functionality.
Advanced control scheme of doubly fed induction generator for wind turbine us...IJECEIAES
This paper describes a speed control device for generating electrical energy on an electricity network based on the doubly fed induction generator (DFIG) used for wind power conversion systems. At first, a double-fed induction generator model was constructed. A control law is formulated to govern the flow of energy between the stator of a DFIG and the energy network using three types of controllers: proportional integral (PI), sliding mode controller (SMC) and second order sliding mode controller (SOSMC). Their different results in terms of power reference tracking, reaction to unexpected speed fluctuations, sensitivity to perturbations, and resilience against machine parameter alterations are compared. MATLAB/Simulink was used to conduct the simulations for the preceding study. Multiple simulations have shown very satisfying results, and the investigations demonstrate the efficacy and power-enhancing capabilities of the suggested control system.
Redefining brain tumor segmentation: a cutting-edge convolutional neural netw...IJECEIAES
Medical image analysis has witnessed significant advancements with deep learning techniques. In the domain of brain tumor segmentation, the ability to
precisely delineate tumor boundaries from magnetic resonance imaging (MRI)
scans holds profound implications for diagnosis. This study presents an ensemble convolutional neural network (CNN) with transfer learning, integrating
the state-of-the-art Deeplabv3+ architecture with the ResNet18 backbone. The
model is rigorously trained and evaluated, exhibiting remarkable performance
metrics, including an impressive global accuracy of 99.286%, a high-class accuracy of 82.191%, a mean intersection over union (IoU) of 79.900%, a weighted
IoU of 98.620%, and a Boundary F1 (BF) score of 83.303%. Notably, a detailed comparative analysis with existing methods showcases the superiority of
our proposed model. These findings underscore the model’s competence in precise brain tumor localization, underscoring its potential to revolutionize medical
image analysis and enhance healthcare outcomes. This research paves the way
for future exploration and optimization of advanced CNN models in medical
imaging, emphasizing addressing false positives and resource efficiency.
Batteries -Introduction – Types of Batteries – discharging and charging of battery - characteristics of battery –battery rating- various tests on battery- – Primary battery: silver button cell- Secondary battery :Ni-Cd battery-modern battery: lithium ion battery-maintenance of batteries-choices of batteries for electric vehicle applications.
Fuel Cells: Introduction- importance and classification of fuel cells - description, principle, components, applications of fuel cells: H2-O2 fuel cell, alkaline fuel cell, molten carbonate fuel cell and direct methanol fuel cells.
3. In dentistry the lost-wax casting technique was not
popular until 1907 when W.H. Taggart introduced this
technique and casting machine. Today the lost-wax
technique is common practice and is used for a variety
of casting operations
Any imperfections or irregularities that result in
unsuccessful casting which interferes with the fit of
final restoration or its esthetic and mechanical
properties
4. In dentistry the resulting casting must be an accurate
reproduction of the wax pattern in both surface details
and overall dimension.
Reproducing the wax up in metal with predictable
results has always been a challenge.
Small variation in investing or casting can
significantly effect the quality of the final restoration.
Successful castings depend on attention to detail and
consistency of technique
5. Definiton
Casting is defined as something that has been
cast in a mold, an object formed by the
solidification of a fluid that has been poured or
injected into a mold.(GPT)
“Casting is the process by which a wax pattern
of a prepared tooth is fabricated and converted
to its metallic replica”(Rosentiel)
6.
7. Finishing and polishing
Quenching and Pickling
Molten metal is cast into the void created by the wax pattern and the sprue
Invested pattern is heated until all the remnants of wax are burned away
The pattern and sprue are invested
All aspects of final restoration are incorporated into the wax pattern
Wax pattern is first formed on a die or directly on the tooth.
10. An unsuccessful casting result in considerable
trouble and loss of time, in almost all instances,
defects in castings can be avoided by strict
observance of procedures governed by certain
fundamental rules and principles.
Seldom is a defect in a casting attributable to other
factors than the carelessness or ignorance of the
operator.
With present techniques, casting failures should be
the exception, not the rule
Phillip’s science of dental materials-11th edition by Kenneth J.Anusavice
page.337
11. Defects in castings can be classified under four
headings(According to Anusavice)
(1) Distortion
(2) Surface roughness and irregularities
(3) Porosity
(4) Incomplete casting or missing detail
12. Roughness
Nodules
Fins
Incompleteness
Voids or porosity
Marginal discrepancies
Dimensional inaccuracies
14. Any marked distortion of the
casting is probably related to
the distortion of the wax
pattern.
This type of distortion can be
minimized or prevented by
proper manipulation of the
wax and handling of the
pattern
Phillip’s science of dental materials-11th edition by Kenneth J.Anusavice.page338
15. Distortion can occur during
spruing the pattern because of
the heat transferred to the
pattern
16. Wax shrinks during cooling(.2%) and may distort at a later time if
cool too fast
Can also caused by the Stresses occur in the inlay wax as a result of
the heating and manipulation of the wax during fabrication of the
pattern.
To Minimise the distortion :
A wax pattern should not be subjected to temperature extreme that
may cause stress relief and distortion in shape
Patterns should never be left off the die.
Invested as soon as possible after fabrication.
Phillip’s science of dental materials-11th edition by Kenneth
J.Anusavicepage 289
Materials in dentistry –priciples and applications by Jack L.Ferracane.page241
17.
18. Unquestionably some distortion
of the wax pattern occurs as the
investment hardens around it.
The setting and hygroscopic
expansions of the investment may
produce a non-uniform expansion
of the walls of the pattern.
This type of distortion occurs in
part from the non uniform
outward movement of the proximal
walls
Phillip’s science of dental materials-11th edition by Kenneth J.Anusavice page;338
19. The characteristics of investments depend on
various factors such as the liquid-powder ratio,
particle size and chemical composition of the
powder, and mixing methods.
The time between mixing and heating influences
the setting behaviour of the investment.
Moreover, setting expansion may lead to distortion
of the wax pattern.
Restorative dental materials -8th edition by Robert G.Craig.page473
20. Effect of wax melting range and investment liquid
concentration on the accuracy of a three-quarter crown
casting
Michio Ito et al,The Journal of Prosthetic Dentistry Volume 87,
Issue 1, January 2002, Pages 57–61
Conclusion:
1. Within the limitation of this study,casting shrinkage was affected
by the type of wax used
2. The higher the softening temperature, the larger the casting
shrinkage.
23. The surface of a dental casting should be an
accurate reproduction of the surface of the wax
pattern from which it is made, excessive roughness
or irregularities on the outer surface of the casting
necessitate additional finishing and polishing,
whereas irregularities on the cavity surface prevent
a proper seating of an otherwise accurate casting
Surface roughness should not be confused with
surface irregularities.
A smooth surface not only prevents plaque and
calculus accumulation, but it also improves the
corrosion resistance of the alloy
24.
25. Surface roughness is defined as relatively
finely spaced surface imperfections whose
height, width, and direction establish the
predominant surface pattern.
Surface irregularities are isolated
imperfections, such as nodules, that are not
characteristic of the entire surface area
Phillip’s science of dental materials-11th edition by Kenneth J.Anusavice.page338
26. CAUSES:
Air bubbles
Water film
Rapid heating rates
Under heating
Liquid : Powder ratio
Prolonged heating
Casting pressure
Composition of Molten alloy
Foreign bodies / Carbon inclusion
Impact of molten alloy
Pattern position
27. Air bubbles that become attached to the pattern during
or subsequent to the investing procedure cause small
nodule on a casting.
Such nodules can sometimes be removed if they are
not in a critical area.
However, for nodules on margins or on internal
surfaces, removal of these irregularities might alter the
fit of the casting.
Phillip’s science of dental materials-11th edition by Kenneth J.Anusavicepage.338
28. Bubbles of gases trapped between the wax pattern and
the investment produce nodules on the casting surface
Large nodule- Air trapped during investing
Multiple nodules – Inadequate vacuum during mixing
Improper brush technique
Lack of surfactant.
Nodules on occlusal surface – Prolonged vibration after
pouring
Contemporary fixed prosthodontics-4th edition by Rosenstiel.Land.Fujimoto.page702
29. Introduction to metal-ceramic technology-2nd edition by W.Patric Naylor.page94
Rough casting with multiple nodule due to failure to evacuate the
investmet’s gaseous by-products during mixing
30. Prevention
The best method to avoid air bubbles is to use the vacuum
investing technique.
Advantages of vacuum mixing-----
1) Remove air bubbles
2) Produce smooth castings
3) Increase tensile strength of investment
4) 95% of castings free of nodules.
5) Removes all the gaseous by products of chemical reaction
of investment material
Introduction to metal-ceramic technology-2nd edition by W.Patric Naylor page95
31. If a manual method is used various precautions has to
be taken to eliminate air from the investment mix
before the investing.
The use of a mechanical mixer with vibration both
before and after mixing should be practiced routinely.
32. The incidence of nodules on casting is more in
hand mixing than vacuum mixing.
The best method is vacuum mix and vacuum
pour technique. But most popular method
vacuum mix and open pour(hand pour)
33. A wetting agent may be helpful in preventing
the collection of air bubbles on the surface of
the pattern, but it is by no means a certain
remedy.
It is important that the wetting agent be applied
in a thin layer. It is best to air dry the wetting
agent, because any excess liquid dilutes the
investment, possibly producing surface
irregularities on the casting.
Introduction to metal-ceramic technology-2nd edition by W.Patric Naylor page100
35. Wax --- water repellent
Creates space in between wax & investment
Appears as minute ridges or veins
If the pattern is moved slightly, jarred or vibrated after
investing, or if the painting procedure does not result in an
intimate contact of the investment the pattern, such a
condition may result
Prevention --- wetting agent, pattern should not be moved,
jarred or vibrated after investing.
Avoid too high liquid : powder ratio
Phillip’s science of dental materials-11th edition by Kenneth
J.Anusavice.page339
36. Phillip’s science of dental materials-11th edition by Kenneth J.Anusavice page339
37. Rapid heating results in fins or spines on the
casting or may result as a characteristic surface
roughness may be evident because of flaking of
the investment when the water or steam pours
into the mold.
Furthermore, such a surge of steam or water
may carry some of the salts used as modifiers
into the mold.
Introduction to metal-ceramic technology-2nd edition by W.Patric Naylor page94
38. Salts are left as deposits on the walls after
water evaporates and leads to surface
roughness
Remody
The mold should be heated gradually; at least
60 minutes should elapse during the heating of
the investment- filling ring from room
temperature to 7000c.
The greater the bulk of the investment, the
more slowly it should be heated
Phillip’s science of dental materials-11th edition by Kenneth J.Anusavicepage339
39. Contemporary fixed prosthodontics-4th edition by
Rosenstiel.Land.Fujimoto.page702
Fins are also caused by
cracks in the investment
that have been filled
with molten metal
Cracks due to over
vibration during
investment or disturbing
ring during setting
40. Introduction to metal-ceramic technology-2nd edition by W.Patric Naylor.page100
Fin caused by excess wax pattern cleaner or improper heating of the
mold
41. Incomplete elimination of wax residues may occur if
the heating time is too short or if insufficient air is
available in the furnace.
These factors are particularly important with the low-
temperature investment techniques.
42. Voids or porosity may occur in the casting from the
gases formed when the hot alloy comes in contact with
the carbonaceous residues.(due to incomplete wax
elimination)
Occasionally, the casting may be covered with a
tenacious carbon coating that is virtually impossible to
remove by pickling.
Phillip’s science of dental materials-11th edition by Kenneth J.Anusavice
43. The amount of water and investment should be
measured accurately.
The higher the L: P ratio, the rougher the casting.
However, if too little water is used, the investment may
be unmanageably thick and cannot be properly applied
to the pattern.
Both leads to rough surface
The science and art of dental ceramics-volume ii bridge esign and laboratory
procedures in dental ceramics by John W.McLean.page232
44. When the high –heat casting technique is used, a
prolonged heating of the mold at the casting
temperature is likely to cause a disintegration of the
investment, and the walls of the mold are roughened as
a result
Furthermore, the products of decomposition are sulfur
compounds that may contaminate the alloy to the
extent that the surface texture is affected.
Phillip’s science of dental materials-11th edition by Kenneth J.Anusavicepage.340
45. Such contamination may be the reason that the surface
of the casting sometimes does not respond to pickling.
When the thermal expansion technique is employed,
the mold should be heated to the casting temperature-
never higher than 7000c – and the casting should be
made immediately.
46. If an alloy is heated to too high temperature before
casting, the surface of the investment is likely to be
attacked, and a surface roughness of the type described
in the previous section may result.
As previously noted, in all probability the alloy will
not be overheated with a gas – air torch when used
with the gas supplied in most localities.
If other fuel is used, special care should be observed
that the color emitted by the molten gold alloy, for
example, is no lighter than a light orange.
Phillip’s science of dental materials-11th edition by Kenneth J.Anusavicepage340
47. Casting Pressure : Too high pressure during
casting produces a rough surface on the
casting. A gauge pressure of 0.10 to 0.14 Mpa
(15 to 20 psi) in an air pressure casting
machine or three to four turns of the spring in
an average type of centrifugal casting is
sufficient
Phillip’s science of dental materials-11th edition by Kenneth J.Anusavicepage340
48. The ratio of the binder to the quartz influences the
surface texture of the casting.
In addition, coarse silica causes a surface roughness.
If the investment meets ADA specification no.2, the
composition is probably not a factor in the surface
roughness
49. When foreign substances get into the mold, a surface
roughness may be produced. For example, a rough
crucible former with investment clinging to it may
roughen the investment on its removal so that bits of
investment are carried into the mold with the molten
alloy.
Carelessness in the removal of the sprue former may be
a similar cause.
50. Usually, contamination results not only in surface
roughness but also in incomplete areas or surface
voids.
Any casting that shows sharp, well- defined
deficiencies indicates the presence of some foreign
particles in the mold, such as pieces of investment and
bits of carbon form a flux.
51. Bright- appearing concavities may be the result of flux
being carried into the mold with the metal.
Surface discoloration and roughness can result from
sulfur contamination, either from investment
breakdown at elevated temperatures or from a high
sulfur content of the torch flame.
The interaction of the molten alloy with sulfur
produces black castings that are brittle and do not clean
readily during pickling.
52. The direction of the sprue former should be such that
the molten gold alloy does not strike a weak portion of
the mold surface.
Occasionally, the molten alloy may fracture or abrade
the mold surface on impact, regardless of its bulk, it is
unfortunate that sometimes the abraded area is smooth
so that it cannot be detected on the surface of the
casting, such a depression in the mold is reflected as a
raised area on the casting, often too slight to be noticed
yet sufficiently large to prevent the seating of the
casting.
53. 1. The science and art of dental ceramics-volume ii bridge esign and laboratory
procedures in dental ceramics by John W.McLean.page224
54. This type of surface roughness or irregularity can be
avoided by proper Spruing so as to prevent the direct
impact of the molten metal at an angle of 900 to the
investment surface.
A glancing impact is likely to be less damaging and at
the same time an undesirable turbulence is avoided.
55. Likewise, too many patterns positioned in the same
plane in the mold should be avoided,
If several pattern are invested in the same ring they
should not be placed too close together.
The expansion of wax is much greater than that of the
investment, causing breakdown or cracking of the
investment if the spacing between patterns is less than
3mm.
The science and art of dental ceramics-volume ii bridge esign and laboratory procedures
in dental ceramics by John W.McLean page230
56.
57. Carbon, as form a crucible , an improperly adjusted
torch or a carbon-containing investment, can be
absorbed by the alloy during casting.
These particles may lead to the formation of carbides
or even created visible carbon inclusions.
58. There are certain surface discolorations and roughness
that may not be evident when the casting is completed
but that may appear during service.
For example, various gold alloys, such as solders, bits
of wire, and mixtures of different casting alloys should
never be melted together and reused.
The resulting mixture would not posses the proper
physical properties and might form eutectic or similar
alloys with low corrosion resistance.
Discoloration and corrosion may also occur.
59. Porosity may occur both within the interior region of a
casting and on the external surface.
The latter is a factor in surface roughness, but also it is
generally a manifestation of internal porosity.
Not only does the internal porosity weaken the casting
but also if it also extends to the surface, it may be a
cause for discoloration.
If severe, it can produce leakage at the tooth-
restoration interface, and secondary caries may result.
Although the porosity in a casting cannot be prevented
entirely, it can be minimized by use of proper
techniques
Phillip’s science of dental materials-11th edition by Kenneth J.Anusavicepage342
60. I. Solidification defects -
A. Localized shrinkage porosity
B. Microporosity
II. Trapped gases -
A. Pinhole porosity
B. Gas inclusions
C. Subsurface porosity.
III. Residual air
61. Localized shrinkage is generally caused by
premature termination of the flow of molten
metal during solidification.
The linear contraction of noble metal alloys -
changing from a liquid to solid is at least
1.25%.
Localized shrinkage generally occurs near the
sprue-casting.
63. Cause:
Diameter of the is too narrow
Length of the sprue is too long
Absence of reservoir
Direction of sprue at 90 degree
64. This type of void may also occur externally,
usually in the interior of a crown near the area
of the sprue, if a hot spot has been created by
the hot metal impinging from the sprue channel
on a point of the mold wall.
This hot spot causes the local region to freeze
last and results in what is called suck-back
porosity
65. Suck-back porosity often
occurs at an occlusoaxial line
angle or incisoaxial line angle
that is not well rounded.
The entering metal impinges
onto the mold surface at this
point and creates a higher
localized mold temperature in
this region, known as a hot
spot
67. A hot spot may retain a localized pool of
molten metal after other areas of the casting
have solidified. This in turn creates a
shrinkage void, or suck-back porosity.
Remody
Suck-back porosity can be eliminated by
flaring the point of sprue attachment and
reducing the mold-melt temperature
differential, that is lowering the casting
temperature by about 30 degree C.
68. Surface Porosity of Different Investment Materials with
Different Mixing Techniques
Ahmed A et al. Al–Rafidain Dent J. 2009; 9(2): 307–314
Conclusion: Manual technique showing higher value of surface
area and number of porosities than the Vacuum technique.
69. The effect of sprue attachment design on castability and
porosity.
Verrett RG, Duke ES. J Prosthet Dent. 1989 Apr;61(4):418-24.
Conclusion: Flared and straight sprue attachments showed
optimized castability and minimized porosity than compared to
abrupt constriction, and gradual constriction
70. Occurs from solidification shrinkage but is
generally present in fine-grain alloy castings
when the solidification is too rapid for the
microvoids to segregate to the liquid pool.
This premature solidification causes the
porosity shown in the form of small, irregular
voids.
71. Such phenomena can occur from rapid
solidification if the mold or casting
temperature is too low.
Unfortunately, this type of defect is not
detectable unless the casting is sectioned
72. Both pinhole and the gas inclusion porosities
are related to the entrapment of gas during
solidification.
Both are characterized by a spherical contour,
but they are decidedly different in size.
The gas inclusion porosities are usually much
larger than pinhole porosity.
73. Many metals dissolve or occlude gases while they are
molten. For example, both copper and silver dissolve
oxygen in large amounts in the liquid state.
Molten platinum and palladium have a strong affinity for
hydrogen as well as oxygen. On solidification, the absorbed
gases are expelled and pinhole porosity results
The larger voids may also result from the same cause, but it
is more logical to assume that such voids are caused by gas
that is mechanically trapped by the molten metal in the
mold or by gas that is incorporated during the casting
procedure
74.
75. Subsurface porosity occurs on occasion. At
other times, it may be particularly evident.
The reasons for such voids have not been
completely established.
76. They may be caused by the simultaneous
nucleation of solid grains and gas bubbles at
the first moment that the alloy freezes at the
mold walls.
As has been explained, this type of porosity
can be diminished by controlling the rate at
which the molten metal enters the mold.
77. Entrapped –air porosity on
the inner surface of the
casting, sometimes referred to
as back-pressure porosity,
can produce large concave
depressions.
This is caused by the
inability of the air in the mold
to escape through the pores in
the investment or by the
pressure gradient that
displaces the air pocket
toward the end of the
investment via the molten
sprue and button
Phillip’s science of dental materials-11th edition by Kenneth J.Anusavicepage347
78. Since back pressure porosity occurs more generally in
full crown type castings, insertion of a wax rod into the
core of the investment when investing the pattern will
provide a good means of venting the hot gases quickly
Use of reservoir
Introduction to metal-ceramic technology-2nd edition by W.Patric Naylor page99
79. The dinstance from the top of the pattern to the outside
of the investment is kept to ¼ inch
Furnace temperatures above 1100ºF help eliminate this
back pressure porosity condition
Introduction to metal-ceramic technology-2nd edition by W.Patric Naylorpage231
80. Increasing the number of turns on a centrifugal
machine and increasing the casting pressure
81. Performing the casting operation in a vacuum
Using more metal when casting so that a good size
button is left as an important precaution.
Hygroscopic low burn out technique produces more of
this porosity than high heat techniques
82. The entrapment is frequently found in a
“pocket” at the cavity surface of a crown or
mesio-occlusal-distal casting.
Occasionally it is found even on the outside
surface of the casting when the casting
temperature or mold temperature is so low that
solidification occurs before the entrapped air
can escaped.
83. The incidence of entrapped air can be increased
by the dense modern investments, an increase
in mold density produced by vacuum investing,
and the tendency for the mold to clog with
residual carbon when the low-heat technique is
used.
Each of these factors tends to slow down the
venting of gases from the mold during casting.
84. Proper burnout, an adequate mold and casting
temperature, a sufficiently high casting
pressure, and proper L: P ratio can help to
eliminate this phenomenon.
It is good practice to make sure that the
thickness of investment between the tip of the
pattern and the end of the ring not be greater
than 6mm.
85. Occasionally, only a partially complete casting
or perhaps no casting at all is found.
The obvious cause is that the molten alloy has
been prevented, in some manner, from
completely filling the mold.
At least 2 factors that may inhibit the ingress
of the liquefied alloy are insufficient venting of
the mold and high viscosity of the fused metal
86.
87. • Insufficient venting of the mold
• High viscosity of the fused metal
• Incomplete elimination of wax residues from the mold
• Low W/P ratio less porosity
• Inadequate spruing
• Mold is too cold
• Insufficient alloy is used
• Sprues are blocked
• Insufficient casting force
• Back pressure of gases in the mold
• Metal not completely molten
• Wax pattern thin
Notes on dental materials-6th edition by E C.Combe page203
88. Incomplete casting resulting from incomplete
wax elimination characterized by rounded
margins and shiny appearance
Phillip’s science of dental materials-11th edition by Kenneth J.Anusavicepage348
89. Phillip’s science of dental materials-11th edition by Kenneth
J.Anusavicepage348
90. The first consideration, insufficient venting, is
directly related to the back pressure exerted by
the air in the mold.
If the air cannot be vented quickly, the molten
alloy does not fill the mold before if solidifies.
In such a case, the magnitude of the casting
pressure should be suspected.
91. If insufficient casting pressure is employed, the
back pressure cannot be overcome.
Furthermore, the pressure should be applied
for at least 4 seconds.
The mold is filled and the metal is solidified in
1 second or less, yet it is quite soft during the
early stages point.
Therefore the pressure should be maintained
for few seconds beyond this point
These are usually exemplified in rounded
incomplete margins.
92. A second common cause for an incomplete casting is
incomplete elimination of wax residues from the mold.
If too many products of combustion remain in the
mold, the pores in the investment may become filled so
that the air cannot be vented completely.
If moisture or particles of wax remain, the contact of
the molten alloy with these foreign substances
produces an explosion that may produce sufficient
backpressure to prevent the mold from being filled.
z
93. It can be seen as rounded margins with quite
shiny rather than dull appearance. The strong
reducing atmosphere created by carbon
monoxide left by the residual wax causes this
shiny condition of the metal.
The possible influence of the L: P ratio of the
investment has been discussed. A lower L: P is
associated with less porosity of the investment.
An increase in casting pressure during casting
solves this problem.
Phillip’s science of dental materials-11th edition by Kenneth J.Anusavice page347-349
94. Different alloy composition and temperature
probably exhibit varying viscosities in the
molten state, depending on composition and
temperature, however, both the surface tension
and the viscosity of a molten alloy are
decreased with an increase in temperature.
An incomplete casting resulting from too great
a viscosity of the casting metal can be
attributed to insufficient heating..
95. The temperature of the alloy should be attributed
to insufficient heating.
The temperature of the alloy should be raised
higher than its liquidus temperature so that its
viscosity and surface tension are lowered and it
does not solidify prematurely as it enters the mold.
Such premature solidification may account for the
greater susceptibility of the white gold alloys to
porosity because their liquidus temperatures are
higher, thus, they are more difficult to melt with a
gas-air torch flame
96. Prevention:
Proper time and temperature adapted during
burnout.
Too large size casting is due to excessive mold
expansion and this is prevented by the use of
correct type of investment and correct
temperature.
Too small casting is due to, too little mold
expansion and it is prevented by heating the
mold sufficiently
Notes on dental materials-6th edition by E C.Combe.page203
97. Naylor (1986) described in detail the "Laws of
Casting" as they pertain to spruing, investing and
burnout, and casting. The seventeen laws are as
follows:
1. Attach the sprue to the thickest cross-sectional
area of the wax pattern.
2. Orient the margins of the wax pattern to the
right and mark their location. This assures that the
centrifugal, rotational, and gravitational forces on
the molten alloy are used to their proper
advantage.
98. 3. Place the wax pattern in a cold zone of the
investment mold, and position the reservoir in the
heat center of the ring. This improves the
likelihood that casting porosity will occur in the
reservoir rather than in the restoration.
99. 4. The reservoir must have enough molten metal
available to fill the shrinkage that occurs within
the restoration.
5. Do not cast a button if a runner bar, or other
internal reservoir, is used.
100. 6. Turbulence must be minimized, if not totally
eliminated. Use smooth gradual pathways. Avoid
sharp turns, restrictions, and impingement on flat
surfaces.
7. Select a casting ring of sufficient diameter and
length to accommodate the pattern or patterns to
be invested. The patterns should be spaced 1/4"
apart with at least 3/8" of investment between the
patterns and the ring liner.
101. 8. The surface tension of the wax pattern must be
reduced. This enables the casting investment to
wet the patterns more completely.
9. Weigh all casting investment powder and
measure all investment liquids to assure a precise
and consistent liquid-powder ratio
102. 10. Eliminate the incorporation of air in the casting
investment during mixing and pouring. Vacuum
mixing is highly recommended.
11. Allow the casting investment to set completely
before beginning the burnout procedure.
12. Use a burnout technique that is specific for the
type of patterns used (wax versus plastic) and
suitable for the particular casting alloy selected.
103. 13. Adequate heat must be available to properly
melt and cast the alloy selected for use.
14. Use the REDUCING ZONE of the casting
torch to melt the alloy and NOT the oxidizing zone
when torch casting.
104. 15. Enough force must be provided to cause the
liquid alloy to flow into the heated mold,
regardless of the type of casting machine used.
16. Cast to your margins. In a centrifugal casting
machine the margins should be oriented downward
and to the right.
17. Allow the ring to bench cool before quenching.
Introduction to metal-ceramic technology-2nd edition by W.Patric Naylor
page97-103
105.
106.
107. 1. Phillip’s science of dental materials-11th edition by Kenneth
J.Anusavice
2. Contemporary fixed prosthodontics-4th edition by
Rosenstiel.Land.Fujimoto
3. Introduction to metal-ceramic technology-2nd edition by
W.Patric Naylor
4. Restorative dental materials -8th edition by Robert G.Craig
5. The science and art of dental ceramics-volume ii bridge esign
and laboratory procedures in dental ceramics by John
W.McLean
6. Materials in dentistry –priciples and applications by Jack
L.Ferracane
7. Notes on dental materials-6th edition by E C.Combe
8. Applied dental materials-9th edition by John F.McCabe and
Angus W.G.Walls
108. 9.Effect of wax melting range and investment liquid concentration on
the accuracy of a three-quarter crown casting by Michio Ito et al,The
Journal of Prosthetic Dentistry Volume 87, Issue 1, January 2002, Pages
57–61
Editor's Notes
A mole on the chin, a dimple on the cheek, imperfections have long been considered signs of beauty and individuality. But it is not so in the field of dental sciences and specifically in casting technology.
The configuration of the pattern, the type of the wax, and the thickness influence the distortion. For example, distortion increases as the thickness of the pattern decreases.
. The gingival margins are forced apart by the mold expansion, whereas the solid occlusal bar of wax resists expansion during the early stages of stetting.
Even under optimal conditions, the surface roughness of the dental casting is invariably somewhat greater than that of the wax pattern from which it is made. The difference is probably related to the particle size of the investment and its ability to reproduce the wax pattern in microscopic detail. With proper manipulative techniques, the normal roughness in the casting should not be major factor in dimensional accuracy. However, improper technique can lead to a marked increase in surface roughness, as well as to the formation of surfaced irregularities.