This document discusses common failures in dental casting procedures. It begins by introducing casting and defining casting defects. It then classifies casting defects into five main categories: distortion, incomplete or missing detail, porosity, contamination, and surface roughness and irregularities. For each type of defect, it describes examples and provides explanations of possible causes and methods for prevention. The document concludes by emphasizing that casting failures can usually be avoided through strict adherence to fundamental casting procedures and techniques.
Dental Ceramics and Porcelain fused to metal isabel
Dental porcelain (also known as dental ceramic) is a dental material used to create biocompatible lifelike dental restorations, such as crowns, bridges, and veneers.
Dental Ceramics and Porcelain fused to metal isabel
Dental porcelain (also known as dental ceramic) is a dental material used to create biocompatible lifelike dental restorations, such as crowns, bridges, and veneers.
History of Direct filling gold
Properties of gold
Indications, contraindications, advantages and disadvantages of direct filling gold, cohesive semi cohesive and non - cohesive gold, types of direct filling gold, Degassing/ Annealing, steps for insertion of dfg, cavity preparation and restoration of direct filling gold
Electrolytic processes in restorative dentisrty /certified fixed orthodontic...Indian dental academy
Welcome to 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 has a unique training program & curriculum that provides students with exceptional clinical skills and enabling them to return to their office with high level confidence and start treating patients
State of the art comprehensive training-Faculty of world wide repute &Very affordable.
brief description about pressable ceramicsCONTENTS: • Introduction • Definition For Dental Ceramics • Definition For Pressable Ceramics • History • Various All Ceramic Systems • Classification • Pressable Ceramics • History • Generation Of Pressable Ceramics • Cerestore – Development Fabrication Advantage Disadvantage 2
3. IPS Empress - Materials And Composition Special Furnace Fabrication Advantage Disadvantage IPS Empress 2- INDICATION Properties Fabrication Method Advantage Disadvantage IPS Emax Press - Microstructure Composition Properties OPC 3G- Development Indication Properties 3
4. INTRODUCTION There have been significant TECHNOLOGICAL advances in the field of dental ceramics over the last 10 years which have made a corresponding increase in the number of materials available. Improvements in strength, clinical performance, and longevity have made all ceramic restorations more popular and more predictable 4
5. DEFINITION FOR DENTAL CERAMICS⁶ An inorganic compound with non metallic properties typically consisting of oxygen and one or more metallic or semi metallic elements (e.g ;Aluminium, Calcium, Lithium, Mangnesium, Potassium, Sodium, Silicon, Tin , Titanium And Zirconium)that is formulated to produce the whole or part of a ceramic based dental prosthesis 5
6. DEFINITION FOR PRESSABLE CERAMICS ⁶ • A ceramic that can be heated to a specified temperature and forced under pressure to fill a cavity in a refractory mold 6
7. HISTORY OF DENTAL CERAMICS ⁶ • 1789-first porcelain tooth material by a French dentist De Chemant • 1774- mineral paste teeth by Duchateau in England • 1808-terrometallic porcelain teeth by Italian dentist Fonzi • 1817- Planteu introduced porcelain teeth in US • 1837- Ash developed improved version of porcelain teeth 7
8. • 1903 – Dr.Charless introduced ceramic crowns in dentistry he fabricate ceramic crown using platinum foil matrix and high fusing feldspathic porcelain excellent esthetics but low flexural strength resulted in failure • 1965- dental aluminous core Porcelain by Mclean and Huges • 1984- Dicor by Adair and Grossman 8
9. 9
10. VARIOUS ALL CERAMIC SYSTEMS Aluminous core ceramics Slip cast ceramics Heat pressed ceramics Machined ceramics Machined and sintered ceramics Metal reinforced system 10
11. MICROSTRUCTURAL CLASSIFICATION⁵ Category 1: Glass-based systems (mainly silica) Category 2: Glass-based systems (mainly silica) with fillers usually crystalline (typically leucite or a different high-fusing glass) a) Low-to-moderate leucite-
Lost-wax technique- definitions and steps including pictures
From spruing, investing, burnout, casting, to finishing and polishing
Source: Contemporary Fixed Prosthodontics
Done by: Lina Nachawati
direct filling gold... material aspect, types, condensation, cavity design, modifications. detaied seminar for post gradutes.... any doubts or suggestions contact dr.mb@hotmail.com
History of Direct filling gold
Properties of gold
Indications, contraindications, advantages and disadvantages of direct filling gold, cohesive semi cohesive and non - cohesive gold, types of direct filling gold, Degassing/ Annealing, steps for insertion of dfg, cavity preparation and restoration of direct filling gold
Electrolytic processes in restorative dentisrty /certified fixed orthodontic...Indian dental academy
Welcome to 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 has a unique training program & curriculum that provides students with exceptional clinical skills and enabling them to return to their office with high level confidence and start treating patients
State of the art comprehensive training-Faculty of world wide repute &Very affordable.
brief description about pressable ceramicsCONTENTS: • Introduction • Definition For Dental Ceramics • Definition For Pressable Ceramics • History • Various All Ceramic Systems • Classification • Pressable Ceramics • History • Generation Of Pressable Ceramics • Cerestore – Development Fabrication Advantage Disadvantage 2
3. IPS Empress - Materials And Composition Special Furnace Fabrication Advantage Disadvantage IPS Empress 2- INDICATION Properties Fabrication Method Advantage Disadvantage IPS Emax Press - Microstructure Composition Properties OPC 3G- Development Indication Properties 3
4. INTRODUCTION There have been significant TECHNOLOGICAL advances in the field of dental ceramics over the last 10 years which have made a corresponding increase in the number of materials available. Improvements in strength, clinical performance, and longevity have made all ceramic restorations more popular and more predictable 4
5. DEFINITION FOR DENTAL CERAMICS⁶ An inorganic compound with non metallic properties typically consisting of oxygen and one or more metallic or semi metallic elements (e.g ;Aluminium, Calcium, Lithium, Mangnesium, Potassium, Sodium, Silicon, Tin , Titanium And Zirconium)that is formulated to produce the whole or part of a ceramic based dental prosthesis 5
6. DEFINITION FOR PRESSABLE CERAMICS ⁶ • A ceramic that can be heated to a specified temperature and forced under pressure to fill a cavity in a refractory mold 6
7. HISTORY OF DENTAL CERAMICS ⁶ • 1789-first porcelain tooth material by a French dentist De Chemant • 1774- mineral paste teeth by Duchateau in England • 1808-terrometallic porcelain teeth by Italian dentist Fonzi • 1817- Planteu introduced porcelain teeth in US • 1837- Ash developed improved version of porcelain teeth 7
8. • 1903 – Dr.Charless introduced ceramic crowns in dentistry he fabricate ceramic crown using platinum foil matrix and high fusing feldspathic porcelain excellent esthetics but low flexural strength resulted in failure • 1965- dental aluminous core Porcelain by Mclean and Huges • 1984- Dicor by Adair and Grossman 8
9. 9
10. VARIOUS ALL CERAMIC SYSTEMS Aluminous core ceramics Slip cast ceramics Heat pressed ceramics Machined ceramics Machined and sintered ceramics Metal reinforced system 10
11. MICROSTRUCTURAL CLASSIFICATION⁵ Category 1: Glass-based systems (mainly silica) Category 2: Glass-based systems (mainly silica) with fillers usually crystalline (typically leucite or a different high-fusing glass) a) Low-to-moderate leucite-
Lost-wax technique- definitions and steps including pictures
From spruing, investing, burnout, casting, to finishing and polishing
Source: Contemporary Fixed Prosthodontics
Done by: Lina Nachawati
direct filling gold... material aspect, types, condensation, cavity design, modifications. detaied seminar for post gradutes.... any doubts or suggestions contact dr.mb@hotmail.com
casting defects during fabrication of alloys.pptxahmedgamal968279
this PowerPoint is concerning with the different types and causes of defects that happened during the casting of dental alloys and how to avoid this fault.
Casting laws/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.
Tom Selleck Health: A Comprehensive Look at the Iconic Actor’s Wellness Journeygreendigital
Tom Selleck, an enduring figure in Hollywood. has captivated audiences for decades with his rugged charm, iconic moustache. and memorable roles in television and film. From his breakout role as Thomas Magnum in Magnum P.I. to his current portrayal of Frank Reagan in Blue Bloods. Selleck's career has spanned over 50 years. But beyond his professional achievements. fans have often been curious about Tom Selleck Health. especially as he has aged in the public eye.
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Introduction
Many have been interested in Tom Selleck health. not only because of his enduring presence on screen but also because of the challenges. and lifestyle choices he has faced and made over the years. This article delves into the various aspects of Tom Selleck health. exploring his fitness regimen, diet, mental health. and the challenges he has encountered as he ages. We'll look at how he maintains his well-being. the health issues he has faced, and his approach to ageing .
Early Life and Career
Childhood and Athletic Beginnings
Tom Selleck was born on January 29, 1945, in Detroit, Michigan, and grew up in Sherman Oaks, California. From an early age, he was involved in sports, particularly basketball. which played a significant role in his physical development. His athletic pursuits continued into college. where he attended the University of Southern California (USC) on a basketball scholarship. This early involvement in sports laid a strong foundation for his physical health and disciplined lifestyle.
Transition to Acting
Selleck's transition from an athlete to an actor came with its physical demands. His first significant role in "Magnum P.I." required him to perform various stunts and maintain a fit appearance. This role, which he played from 1980 to 1988. necessitated a rigorous fitness routine to meet the show's demands. setting the stage for his long-term commitment to health and wellness.
Fitness Regimen
Workout Routine
Tom Selleck health and fitness regimen has evolved. adapting to his changing roles and age. During his "Magnum, P.I." days. Selleck's workouts were intense and focused on building and maintaining muscle mass. His routine included weightlifting, cardiovascular exercises. and specific training for the stunts he performed on the show.
Selleck adjusted his fitness routine as he aged to suit his body's needs. Today, his workouts focus on maintaining flexibility, strength, and cardiovascular health. He incorporates low-impact exercises such as swimming, walking, and light weightlifting. This balanced approach helps him stay fit without putting undue strain on his joints and muscles.
Importance of Flexibility and Mobility
In recent years, Selleck has emphasized the importance of flexibility and mobility in his fitness regimen. Understanding the natural decline in muscle mass and joint flexibility with age. he includes stretching and yoga in his routine. These practices help prevent injuries, improve posture, and maintain mobilit
Pulmonary Thromboembolism - etilogy, types, medical- Surgical and nursing man...VarunMahajani
Disruption of blood supply to lung alveoli due to blockage of one or more pulmonary blood vessels is called as Pulmonary thromboembolism. In this presentation we will discuss its causes, types and its management in depth.
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These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
Acute scrotum is a general term referring to an emergency condition affecting the contents or the wall of the scrotum.
There are a number of conditions that present acutely, predominantly with pain and/or swelling
A careful and detailed history and examination, and in some cases, investigations allow differentiation between these diagnoses. A prompt diagnosis is essential as the patient may require urgent surgical intervention
Testicular torsion refers to twisting of the spermatic cord, causing ischaemia of the testicle.
Testicular torsion results from inadequate fixation of the testis to the tunica vaginalis producing ischemia from reduced arterial inflow and venous outflow obstruction.
The prevalence of testicular torsion in adult patients hospitalized with acute scrotal pain is approximately 25 to 50 percent
Explore natural remedies for syphilis treatment in Singapore. Discover alternative therapies, herbal remedies, and lifestyle changes that may complement conventional treatments. Learn about holistic approaches to managing syphilis symptoms and supporting overall health.
Ethanol (CH3CH2OH), or beverage alcohol, is a two-carbon alcohol
that is rapidly distributed in the body and brain. Ethanol alters many
neurochemical systems and has rewarding and addictive properties. It
is the oldest recreational drug and likely contributes to more morbidity,
mortality, and public health costs than all illicit drugs combined. The
5th edition of the Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) integrates alcohol abuse and alcohol dependence into a single
disorder called alcohol use disorder (AUD), with mild, moderate,
and severe subclassifications (American Psychiatric Association, 2013).
In the DSM-5, all types of substance abuse and dependence have been
combined into a single substance use disorder (SUD) on a continuum
from mild to severe. A diagnosis of AUD requires that at least two of
the 11 DSM-5 behaviors be present within a 12-month period (mild
AUD: 2–3 criteria; moderate AUD: 4–5 criteria; severe AUD: 6–11 criteria).
The four main behavioral effects of AUD are impaired control over
drinking, negative social consequences, risky use, and altered physiological
effects (tolerance, withdrawal). This chapter presents an overview
of the prevalence and harmful consequences of AUD in the U.S.,
the systemic nature of the disease, neurocircuitry and stages of AUD,
comorbidities, fetal alcohol spectrum disorders, genetic risk factors, and
pharmacotherapies for AUD.
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TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
Lung Cancer: Artificial Intelligence, Synergetics, Complex System Analysis, S...Oleg Kshivets
RESULTS: Overall life span (LS) was 2252.1±1742.5 days and cumulative 5-year survival (5YS) reached 73.2%, 10 years – 64.8%, 20 years – 42.5%. 513 LCP lived more than 5 years (LS=3124.6±1525.6 days), 148 LCP – more than 10 years (LS=5054.4±1504.1 days).199 LCP died because of LC (LS=562.7±374.5 days). 5YS of LCP after bi/lobectomies was significantly superior in comparison with LCP after pneumonectomies (78.1% vs.63.7%, P=0.00001 by log-rank test). AT significantly improved 5YS (66.3% vs. 34.8%) (P=0.00000 by log-rank test) only for LCP with N1-2. Cox modeling displayed that 5YS of LCP significantly depended on: phase transition (PT) early-invasive LC in terms of synergetics, PT N0—N12, cell ratio factors (ratio between cancer cells- CC and blood cells subpopulations), G1-3, histology, glucose, AT, blood cell circuit, prothrombin index, heparin tolerance, recalcification time (P=0.000-0.038). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and PT early-invasive LC (rank=1), PT N0—N12 (rank=2), thrombocytes/CC (3), erythrocytes/CC (4), eosinophils/CC (5), healthy cells/CC (6), lymphocytes/CC (7), segmented neutrophils/CC (8), stick neutrophils/CC (9), monocytes/CC (10); leucocytes/CC (11). Correct prediction of 5YS was 100% by neural networks computing (area under ROC curve=1.0; error=0.0).
CONCLUSIONS: 5YS of LCP after radical procedures significantly depended on: 1) PT early-invasive cancer; 2) PT N0--N12; 3) cell ratio factors; 4) blood cell circuit; 5) biochemical factors; 6) hemostasis system; 7) AT; 8) LC characteristics; 9) LC cell dynamics; 10) surgery type: lobectomy/pneumonectomy; 11) anthropometric data. Optimal diagnosis and treatment strategies for LC are: 1) screening and early detection of LC; 2) availability of experienced thoracic surgeons because of complexity of radical procedures; 3) aggressive en block surgery and adequate lymph node dissection for completeness; 4) precise prediction; 5) adjuvant chemoimmunoradiotherapy for LCP with unfavorable prognosis.
Flu Vaccine Alert in Bangalore Karnatakaaddon Scans
As flu season approaches, health officials in Bangalore, Karnataka, are urging residents to get their flu vaccinations. The seasonal flu, while common, can lead to severe health complications, particularly for vulnerable populations such as young children, the elderly, and those with underlying health conditions.
Dr. Vidisha Kumari, a leading epidemiologist in Bangalore, emphasizes the importance of getting vaccinated. "The flu vaccine is our best defense against the influenza virus. It not only protects individuals but also helps prevent the spread of the virus in our communities," he says.
This year, the flu season is expected to coincide with a potential increase in other respiratory illnesses. The Karnataka Health Department has launched an awareness campaign highlighting the significance of flu vaccinations. They have set up multiple vaccination centers across Bangalore, making it convenient for residents to receive their shots.
To encourage widespread vaccination, the government is also collaborating with local schools, workplaces, and community centers to facilitate vaccination drives. Special attention is being given to ensuring that the vaccine is accessible to all, including marginalized communities who may have limited access to healthcare.
Residents are reminded that the flu vaccine is safe and effective. Common side effects are mild and may include soreness at the injection site, mild fever, or muscle aches. These side effects are generally short-lived and far less severe than the flu itself.
Healthcare providers are also stressing the importance of continuing COVID-19 precautions. Wearing masks, practicing good hand hygiene, and maintaining social distancing are still crucial, especially in crowded places.
Protect yourself and your loved ones by getting vaccinated. Together, we can help keep Bangalore healthy and safe this flu season. For more information on vaccination centers and schedules, residents can visit the Karnataka Health Department’s official website or follow their social media pages.
Stay informed, stay safe, and get your flu shot today!
These lecture slides, by Dr Sidra Arshad, offer a quick overview of physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
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NVBDCP was launched in 2003-2004 . Vector-Borne Disease: Disease that results from an infection transmitted to humans and other animals by blood-feeding arthropods, such as mosquitoes, ticks, and fleas. Examples of vector-borne diseases include Dengue fever, West Nile Virus, Lyme disease, and malaria.
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4. TOPICS INCLUDED IN SEMINAR
Introduction
Classification
of different
types of
defects
Etiology of
casting
defects
Its
prevention
Conclusion References
5. INTRODUCTION
• Casting is defined as the act of forming an object in a mold. The object
formed from this procedure is called as casting.
• Any irregularity in the metal casting process that is undesired is called
Casting Defect.
• Casting is one of the most common procedures in dentistry and is mostly
done by dental technicians.
• By understanding the cause of the defect, a dentist as well as technician can
prevent the defect.
7. DISTORTION
• Distortion of the casting is usually due to distortion of
wax pattern
Some distortion of wax occurs when the investment
hardens or due to hygroscopic setting expansion. It does not cause
serious problems
Some distortion of wax
occurs during manipulation,
because of the release of
internal stresses
8. • Minimize distortion by :
1. Manipulation of wax at high temperature
2. Investing pattern within one hour after finishing
3. If storage is necessary, store in refrigerator
DISTORTION
9. SURFACE ROUGHNESS
• Surface roughness can usually be traced to :
1) Air bubbles on wax pattern cause nodules on the casting.
it can be avoided by :-
- Proper mixing of investment
- vibration of mix or by vacuum
investing
-Application of wetting agents
10. 2) Too rapid heating, it may cracks the investment resulting in fins
it can be avoided by :-
- Heat the ring gradually to
7000
C (in at least 1 hour)
3) Higher W/P ratio gives rougher casting. Larger particle size of
investment has the same effect
it can be avoided by :-
- Using correct W/P ratio &
select investment of correct
particle size
11. 4) Prolonged heating causes disintegration of the mould cavity
it can be avoided by :-
- complete the casting as soon as the ring is heated & ready
- Overheating of gold alloy has the same effect. It
disintegrates the investment.
5) Too high or too low casting pressure
it can be avoided by :-
- Using 15 lbs /sq inch of air pressure or three to four
turns of centrifugal casting machine
13. 6) Composition of the investment.
Proportion of the quartz & binder influences the surface
texture of casting. Coarse silica will give coarse casting
6) Foreign body inclusion shows sharp, well defined
deficiencies. Inclusion of flux shows bright concavities
15. POROSITY
• Porosity may be internal or external
• External porosity can cause discoloration of the casting
• Internal porosity weakens the restoration
• Severe porosity at the tooth restoration junction can cause
secondary caries
16. • Porosities are Classified as
1) Those caused by solidification shrinkage
Localized shrinkage porosity
Suck back porosity
Microporosity
2) Those caused by gas
Pin hole porosity
Gas inclusions
Sub-surface porosity
3) Those caused by air trapped in the mould
Back pressure porosity
Acc. To Phillips
17. Localized Shrinkage Porosity Or Shrink Spot
• These are large irregular voids usually found near the sprue-casting
junction.
• It occurs when cooling sequence is incorrect & the sprue freezes
before the rest of the casting.
• During a correct cooling sequence, the sprue should freeze last.
• This helps the molten metal to flow into the mould to compensate
for the shrinkage of the casting as it solidifies.
18. • If the sprue solidifies before the rest of the casting no more molten
metal can be supplied from the sprue.
• The subsequent shrinkage produces voids or pits known as shrink-
spot porosity
it can be avoided by :-
using sprue of correct thickness
Attach sprue to thickest portion of wax pattern
Flaring the at the point of attachment or placing a reservoir close to
the wax pattern
20. SUCK BACK POROSITY
• It is a variation of the shrink
spot porosity
• This is an external void usually
seen in the inside of a crown
opposite the sprue
• A hot spot is created by the hot metal impinging on the
mould wall near the sprue
21. • The hot spot causes this region to freeze last
• The sprue has already solidified, no more molten
material is available & the resulting shrinkage causes a
peculiar type of shrinkage called suck back porosity
• It is avoided by reducing the temperature difference
between the mould & the molten alloy
22. MICROPOROSITY
• These are fine irregular voids within the casting
• It is seen when the casting freezes too rapidly
• Rapid solidification occurs when the mould or casting
temperature is too low
23. PIN HOLE POROSITY
• Many metals dissolve gases when molten
• Upon solidification the dissolved gases are expelled causing tiny
voids, e.g.. platinum & palladium absorb hydrogen
• Copper & Silver dissolve oxygen
24. GAS INCLUSION POROSITY
• These are also spherical voids but are larger than pin hole type
• They may also be due to dissolved gases, but are more likely due to gases
carried in or trapped by the molten metal
• A poorly adjusted blow torch can also occlude gases
25. BACK PRESSURE POROSITY
• This is caused by inadequate venting (air escape) of the mould
• The sprue pattern length should be adjusted so that there is
not more than 1/4th thickness of the investment between the
bottom of the casting ring & the wax pattern
• When the molten metal enters the mould, the air inside is
pushed out through the porous investment at the bottom
26. • If the bulk of the investment is too great, the escape of air
becomes difficult causing increased pressure in the mould
• The molten metal will then solidify before the mould is
completely filled resulting in a porous casting with rounded short
margins
27. • Avoid by
1) Using adequate casting
force
2) Use investment of
adequate porosity
3) Place pattern not more
than 6 to 8 mm away from
the end of the ring
4) Providing vents in large
castings
28. CASTING WITH GAS BLOW HOLES
• If there is any wax residue remaining in the mould, it gives off a
large volume of gas, as the molten alloy enters the mould cavity
• This gas can cause deficiencies in the casting & blow holes in the
residue button
• To help the elimination of wax completely from the mould, the
burn out should be done with the sprue hole facing
downwards for the wax to run down
29. INCOMPLETE CASTING
• An incomplete casting may result when
1) Insufficient alloy used
2) Alloy not able to enter thin parts of mould
3) When mould is not heated to casting temperature
4) Premature solidification of alloy
5) Sprues are blocked with foreign bodies
6) Back pressure due to gases in mould cavity
7) Low casting pressure
8) Alloy not sufficiently molten or fluid
31. To bright and shiny casting with short and rounded margins
• When the wax is not completely eliminated, it combines with oxygen or air in
the mould cavity forming carbon mono-oxide which is a reducing agent. The
gas prevents the oxidation of the surface of the casting gold with the result
that the casting which comes out from the investment is bright and shiny.
The formation of gas in the mould is so rapid that it also has a back pressure
effect.
33. Incomplete casting resulting from incomplete wax
elimination is characterized by rounded margins &
shiny appearance
34. SMALL CASTING
• If compensation for shrinkage of alloy is not done by adequate
expansion of mould cavity, then a small casting will result.
Another reason is, the shrinkage of the impression material.
35. CONTAMINATION
1. Due to oxidation when molten alloy is over heated
2. Use of oxidizing zone of the flame
3. Failure to use flux
4. Due to formation of Sulphur compounds
it can be avoid by :-
• Not overheating alloy
• Use reducing zone of the flame
• Use of flux
36. BLACK CASTING
• Can be due to two reasons
1. Overheating the investment above 7000c causes it
to decompose liberating Sulphur or Sulphur
compounds. They readily combine with the metals in
gold alloy forming a sulphide film. This gives a dark
casting which cannot be cleaned by pickling.
37. 2. A black casting, can be also due to incomplete
elimination of the wax pattern, as a result of
heating the mould 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.
38.
39.
40. CONCLUSION
• An unsuccessful casting results in considerable trouble
& loss of time
• In almost all instances, defects in castings can be
avoided by strict observance of procedures governed by
certain fundamental rules & principles.
• Seldom is a defect in a casting attributable to factors
other than carelessness or ignorance of the operator
• With present technique the casting failure should be the
exception, not the rule.
41. REFERENCES
• Fundamentals of fixed prosthodontics-
Herbert T. Shillingburg
• Dental laboratory procedures – FPD
kenneth D.Rudd , Robert M. Morrow
• PHILIPS’ Science of Dental Materials
Eleventh Edition Anusavice
• Essentials of Dental Materials
SH Soratur
• Contemporary fixed Prosthodontics,
Rosenstiel
Casting procedure is technique sensitive procedure. There are certain rules and principles for casting process and
both dentist as well as dental technicians should be aware of.
This final concluding chart is taken from Contemporary FPD by Rossenstiel