The document discusses the process of metal casting in dentistry. It begins with an introduction to casting and defines it as a process where molten material is poured into a mold and allowed to harden. It then covers topics like dental waxes, sprue formation, investing materials, burnout procedures, casting machines, and alloy melting temperatures. The overall document provides an overview of the key steps and considerations for the dental metal casting procedure.
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-
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
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.
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.
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.
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
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.
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.
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.
Description :
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 procedures /certified fixed orthodontic courses by Indian dental aca...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
LOST WAX TECHNIQUE
Lost wax casting technique dates back to Bronze Age(approx. 3000-3500 BC).
Taggart’s presentation to the New York Odontological Group in 1907 on the fabrication of cast inlay restorations developed in 1905 often has been acknowledged as the first reported application of the lost-wax technique in dentistry.
Taggart devised centrifugal casting machine under the principle of lost wax technique
Pickling is heating the discolored casting in an acid.
The best pickling solutions for gypsum bonded investments is a 50% hydrochloric acid solution.
The hydrochloric acid aids in the removal of any residual investment, as well as of the oxide coating.
The disadvantage of hydrochloric acid is that the fumes from the acid are likely to corrode laboratory metal furnishings. In addition, these fumes are a health hazard and should be vented via a fume hood.
A solution of sulfuric acid may also be more advantageous in this respect.
Ultrasonics are also useful for cleaning the casting.
INTRODUCTION- Removable partial denture: the replacement of missing teeth and supporting tissues with a prosthesis designed to be removed by the wearer-GPT.
Cast partial denture is a type of partial denture comprising a cast metal framework with acrylic resin prosthetic teeth.
Traditional acrylic partial dentures are less durable, retentive, and stronger than cast partial dentures.
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
this presentation describes the various casting procedures, their history, the various metal alloys that are used for casting. it explains the various casting procedures in details and the casting defects in brief.
Casting procedures/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.
Knee anatomy and clinical tests 2024.pdfvimalpl1234
This includes all relevant anatomy and clinical tests compiled from standard textbooks, Campbell,netter etc..It is comprehensive and best suited for orthopaedicians and orthopaedic residents.
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
New Drug Discovery and Development .....NEHA GUPTA
The "New Drug Discovery and Development" process involves the identification, design, testing, and manufacturing of novel pharmaceutical compounds with the aim of introducing new and improved treatments for various medical conditions. This comprehensive endeavor encompasses various stages, including target identification, preclinical studies, clinical trials, regulatory approval, and post-market surveillance. It involves multidisciplinary collaboration among scientists, researchers, clinicians, regulatory experts, and pharmaceutical companies to bring innovative therapies to market and address unmet medical needs.
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.
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
Prix Galien International 2024 Forum ProgramLevi Shapiro
June 20, 2024, Prix Galien International and Jerusalem Ethics Forum in ROME. Detailed agenda including panels:
- ADVANCES IN CARDIOLOGY: A NEW PARADIGM IS COMING
- WOMEN’S HEALTH: FERTILITY PRESERVATION
- WHAT’S NEW IN THE TREATMENT OF INFECTIOUS,
ONCOLOGICAL AND INFLAMMATORY SKIN DISEASES?
- ARTIFICIAL INTELLIGENCE AND ETHICS
- GENE THERAPY
- BEYOND BORDERS: GLOBAL INITIATIVES FOR DEMOCRATIZING LIFE SCIENCE TECHNOLOGIES AND PROMOTING ACCESS TO HEALTHCARE
- ETHICAL CHALLENGES IN LIFE SCIENCES
- Prix Galien International Awards Ceremony
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.
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!
Ozempic: Preoperative Management of Patients on GLP-1 Receptor Agonists Saeid Safari
Preoperative Management of Patients on GLP-1 Receptor Agonists like Ozempic and Semiglutide
ASA GUIDELINE
NYSORA Guideline
2 Case Reports of Gastric Ultrasound
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
6. Casting is a process in which molten material
is poured into a mould and allowed to harden
into the shape of the mould.
Term “casting” is applied to the shape
produced as well as to the process by which
it is made.
7. The lost wax technique has been used for
centuries but its use in dentistry was not
common until 1907,when W.H.TAGGART
introduced his technique with the casting
machine in Chicago-USA
8. Casting ring
Sprue former
Crucible former
Vacuum Investing unit
High heat electric furnace
Source of high heat i.e. flame
Centrifugal casting machine
Finishing and polishing instruments
9. Dental waxes are originally polymers
consisting of hydrocarbons & their derivatives
(e.g. ether & alcohol) and are blends of natural
and synthetic waxes, natural resins, oils, foils,
and gums
M. wt => 400-4000.
Melting range of 50*C to 300*C, rather than
a single temperature,
because their components consists of a wide
distribution of molecular weight
10. The American national standards institute /
American dental association(ANSI/ADA)
specification NO:4 waxes used for fabrication
of patterns for dental casting are divided into
two types
TYPE 1: medium wax used in direct
techniques;
TYPE 2: soft waxes used in indirect
techniques
.
11. There are three basic requirements, as
follows:
1. The sprue must allow the molten wax to
escape from the mold
2. The sprue must enable the molten metal
to flow into the mold with as little
turbulence as possible.
3. The metal within it must remain molten
slightly longer than the alloy that has
filled the mold.
12. The sprue can be wax, plastic, or metal
Wax sprues are preferred for most castings
because they melt at the same rate as the
pattern and thus allow easy escape of the
molten wax.
13. Solid plastic sprues soften at a higher
temperature than the wax pattern and
may block the escape of wax, resulting in
increased casting roughness.
However, plastic sprues can be useful
when casting fixed partial dentures
(F.P.D) in one piece because their added
rigidity minimize distortion.
Also, hollow plastic sprues are available
that permit the escape of wax
14. METAL SPRUES
If a metal sprue is used, it should be made
of non-rusting metal to avoid possible
contamination of the wax.
They are usually removed from the
investment at the same time as the crucible
former.
16. Wax patterns can be sprued in one of two
different methods.each method has it’s
advantages & disadvantages.
17. With the direct spruing the flow of the
molten metal is straight from the casting
crucible to pattern area in the ring.
This method requires less time
PROCEDURE:
A straight Sprue former is luted to the
thickest part of the wax pattern.
18. One end is to the wax pattern & other end is
secured to the crucible former
The sprue former can be modified by placing
a ball or round reservoir between the pattern
and the button
19. Even with the ball reservoir, the spruingEven with the ball reservoir, the spruing
method is still direct.method is still direct.
Direct spruing is used most frequently for
the single units.
The draw back of this method is the
potential suck back porosity at the junction
of the restoration and the sprue.
20. With the indirect spruing,the molten metal
does not flow directly form the casting
crucible into the pattern area.
The casting alloy takes a circuitous root before
it reaches the pattern areas.
21. With this method of spruing,the connector bar
is 6-gauge or 8-gauge round wax to which the
wax pattern sprues are attached on one side
and with two larger ingot sprue formers on
the other side.
Connecter bar
Wax pattern sprues
Ingot sprue formers
22. Here the connector acts as a reservoir.
Indirect Spruing offers advantages such
as greater predictability and reliability in
the casting plus enhanced control of
solidification shrinkage.
23. The reservoir of spruing system should be
placed in the heat center of the ring.
This should have the largest mass at any
part of the sprue system
HEAT CENTRE
24. If the pattern is small, the sprue former
must be small, because attaching a large
sprue formers to thin, delicate pattern
could cause distortion.
If the sprue diameters too small, this area
will solidify before the casting itself and
localized shrinkage porosity (suck –back”
porosity) may develop.
25. 2.5 mm (10 gauge) sprue is recommended
for molar and metal ceramic patterns.
A smaller 2.0 mm (12 gauge) is adequate
for premolars & partial coverage
restoration including Inlays , Onlays and
Cast Post.
The ideal area for theSPRUE POSITION (OR)
LOCATION is the point of greatest bulk in the
pattern to avoid distortion and to permit
complete flow of the alloy into the mold cavity.
26. The sprue former should be directed away form any
thin or delicate part of the pattern, because the
molten metal may abrade or fracture investment in
this area and result in a casting failure.
If it is sprued at a 45o
angle to the proximal area, a
satisfactory casting is obtained.
27. This length is depends on the length of the
casting ring.
Length should be adjusted so that the top of
the wax pattern is with in 6 mm of the open
end of the ring for gypsum bonded
investments.
In the phosphate bonded investment it is
within 3-4 mm of the top of the investment.
29. Stainless steel rings
Pyronel alloy metal rings.
Available in two shapes round and
oval and two diameters large & small.
30. PYRONEL ALLOY METAL RINGS (WHIP MIX
CORPORATION)
Even after repeated heating they remain
precision fitting and stable in size.
They do not flake, corrode or peel away, thus
they have an unusually long life.
31. These are used in ring less casting
system
A ring less system that provides
maximum expansion of investment is
available commercially.
32. The system, called the power cast ring less
system consists of 3 sizes of rings and
formers with a release ring, preformed wax
sprues and investment powder, and a
special investment liquid.
33. These rings are tapered to allow for
removal of the investment mold after the
material has set.
This system is suited for casting of alloys that
require greater mold expansion than
traditional gold-based alloys
34. The sprue is attached to a crucible former.
Usually made of rubber / wax which
constitutes the base of the casting ring
during investing.
The exact shape of the crucible former
depends on the type of casting machine
used.
35. With the use of solid metal rings or casting
flasks, provision must be made to permit
investment expansion.
However, the most commonly used technique
to provide investment expansion is to line
the walls of the ring with a ring liner.
36. Traditionally, asbestos was the material
of choice, but it can no longer be used
because its carcinogenic potential makes
it a biohazard
2 types of non-asbestos ring liner material
have been produced.
1.An alluminosilicate ceramic liner
2.A cellulose (paper) liner
37. FUNCTIONs
a. Allows for mould expansion.
b. When the ring is transferred from the
furnace to the casting machines, it
reduces loss of heat, as it is a thermal
insulator.
c. Permits easy separation of the investment
from the ring after the casting is over.
38. The dry liner is tacked in position with
sticky wax, and it is then used either dry or
wet.
With a wet liner technique, the liner ring is
immersed in water for a time, and the excess
water is shaken away.
Squeezing the liner should be avoided,
because this leads to variable amounts of
water removal and non-uniform expansion.
39. A ceramic liner not absorb water like
cellulose liner, its network of fibers can
retain water on the surface.
The liner does not only afford greater
normal setting expansion in the
investment, but also the absorbed water
causes a semi hygroscopic expansion.
The thickness of liner should be
approximately 1 mm
40. The expansion of the investment is always
greater in the unrestricted longitudinal
direction than in to radical direction, that is,
toward to ring.
Placing the liner short (3.25 mm) of the endsPlacing the liner short (3.25 mm) of the ends
of the ring tends to produce more uniformof the ring tends to produce more uniform
expansion; thus there is less chance forexpansion; thus there is less chance for
distortion of the wax pattern and the mold.distortion of the wax pattern and the mold.
41. In general, the investment materials contain.
1. Refractory material
2. Binder
3. Modifiers Quartz&Cristobalite Dental stone
42. 1. Gypsum bonded investmentsGypsum bonded investments
They are used for casting gold alloys
They can withstand temp up to 700o
C
2. Phosphate bonded investmentsPhosphate bonded investments
They are used for casting cobalt chromium alloys
They can with stand high temperatures
3. Silica bonded investmentsSilica bonded investments
Alternative to the phosphate bonded investments,
for high temperature casting used in the casting of
base metal alloy partial dentures.
43. Classification:- According A.D.A specification no.2 for casting
investments for dental gold alloys, there are 3 types.
Type – I
Are those employed for the casting of inlays or
crowns when the allow casting shrinkage
compensation is accomplished principally by
thermal expansion of the investment.
Type – II
compensation for alloy shrinkage is by the
hygroscopic expansion.
Type III
Investments are used in the construction of partial
denture with gold alloys.
44. Phosphate bonded investments have the
following approximate composition
according to ALLAN, ASGAR (1966) and
mabic (1973):
Quartz, Cristobalite =>75 %to 90%
Mono ammonium phosphate =>7 %to 10%
Magnesium oxide =>3% to 5%
45. Unspecified amounts of carbon are often
added to these powders, giving them a black
Color, to minimize oxidation of alloys cast
into them.
Base metal alloy react with carbon at
temperature above 1500o
C, however, forming
Carbides that can embrittle these alloys;
carbon free (white) phosphate investments
are available for fabrication of copings and
frameworks.
47. These are used for pouring impressions,
placing investment around wax patterns in
casting flasks (rings)
Two types
1.Offer variation in intensity
of vibratory action
2.Offer variation in vibration
frequency. The table of the unit is covered by a
rubber cushion, which moderates the
sharpness of the vibration and
facilitates cleaning
48.
49. The vacuum mixing of investments to
eliminate air bubbles from the mix is
essential to the production of fine dental
castings.
It provides both vacuum source and power
spatulation in appropriate carriers or
vessels (bowls)
.
50. The whip mix corporation manufactures a
combination mixing unit, which serves as a
vacuum pump, power mixer, and vibrator.
Designed primarily for wall mounting
51. The first attempts at wax elimination
and mold conditionings were gas-fired
appliances or other simple arrangements
typified by a casting flask (ring) resting upon
a wire mesh suspended over a Bunsen
burner.
52. Furnace with electric muffles were developed
that permitted adjustment of temperature for
high heat or low heat casting techniques and
timing devices were added later.
53. With the development of high heat (silicate
and phosphate bonded) investments, the use
of multiple stage of burnout temperatures to
prevent mold cracking and damage became
necessary
54. 1. Allow the investment to set for the
recommended time (usually 1 hour) and then
remove the rubber crucible former
a. If a metal sprue is used, remove it as well
b. Any loose particles of investment should be
blown off with compressed air.
55. 2.Place the ring with the sprue facing down
in the furnace on a ribbed tray. The tray
allows the molten wax to flow out freely
56. 3.Bring the furnace to 200*C (400*F) and hold this
temperature for 30 minutes most of the wax is
eliminated by this time.
4.Increase the heat to the final burnout
temperature [generally 650*C (1200*F) or
480*C (900*F) follow the manufacturers
instruction] and hold for 45 min ; because the
heating rate affects the expansion.
57. When transferring the casting ring to the
casting machine, a quick visual check of the
sprue in shaded light is helpful to see
whether it is properly heated. It should be a
cherry red color.
58. A vessel made of a refractory substance and
used for melting and calcining materials at
high temperature .
59. Generally 4 types of casting crucibles are
available: Clay, Ceramic, Quartz AndClay, Ceramic, Quartz And
Zirconia Alumina.Zirconia Alumina.
60. Clay crucibles are appropriate for many of the
crown & bridge alloys, such as the high noble
and noble type.
Ceramic crucibles can be used not only for high
noble crown & bridge alloys but also for the
higher fusing gold based metal ceramic alloys.
61. Crucibles made from alumina, quartz, or silica
Are recommended for high fusing alloys of
any type these are especially suited for alloys
that have a high melting temperature or those
that are sensitive to carbon contamination.
62. Casting machines provide the means for transferring the
molten alloy from the melting crucible to the mold.
Types-
1. Centrifugal casting machine
2. Air pressure machine- Hereus
3. Induction melting casting machine
4. Steam pressure machine- Solbrig machine
5.Spring wound electrical resistance-machine furnace-
casting machine
63. CENTRIFUGAL CASTING MACHINE:
May be spring driven or motor driven.
Advantage-
simplicity of design and operation.
both large and small castings can be cast on
same machine.
64. AIR PRESSURE MACHINE:
Gases like compressed air or gases like
carbon monoxide or nitrogen, can be used.
Used for making small castings.
65. INDUCTION MELTING CASTING MACHINE:
Metal is melted and forced by air pressure
into mould.
Used for casting base metal alloys.
66. Alloys can be melted by:
Blow torch
By electrical resistance
Induction
BLOW TORCH:
Fuel used is a combination of-
Natural or artificial gas and air
Oxygen and acetylene gas (for high fusion
aloys)
67. Element melting temp
Gold 1945 F
Copper 1981 F
Silver 1761 F
Platinum 3217 F
Palladium 2826 F
Indium 313 F
Zinc 787 F
Tin 449 F
68. Gallium 86 F
Iron 2797 F
Iridium 4449 F
Ruthenium 4530 F
Nickel 2647 F
Cobalt 2723 F
Rhenium 5755 F
Molybdenum 4730 F
Chromium 3470 F
Boron 3690 F
Manganese 2273 F
69. Let first consider the gold crown and bridge
alloys.
After the casting has solidifies, the ring is
removed and quenched in water as soon as the
button exhibits a dull-red glow.button exhibits a dull-red glow.
70. 1.The noble metal alloy is left in an annealed
condition for burnishing,polishing,and
similar procedures.
2.when the water contacts the investment, a
violent reaction ensures, resulting in a soft,
granular investment that is easily removed.
71. After quenching, Gypsum bonded investment
quickly disintegrate.
Phosphate bonded investment do not
disintegrate and must be forcibly removed from
the casting ring.
72. ** NOTE:-
Gold based ,palladium based , metal ceramic
alloys and base metal alloys are bench-cooled
to room temperature before the casting is
removed from the investment.
73. ** NOTE:-
Casting from these alloys are generally not
pickled.
Abrasive blasting devices (sand blaster) are
used for cleaning the surface of castings.
74. Often the surface of casting appears dark
with oxides and tarnish such a surface film
can be removed by a processremoved by a process known as
pickling.
75. The surface oxides from the casting are
removed by pickling in 50% hydrochloric acid.
The disadvantage of HCL is the fumes from
acid are likely to corrode lab metal
furnishings and health hazard.
76. So the process performed ultrasonically
while the prosthesis is sealed in a Teflon
container.
The best method for pickling is to place
the casting in test tube and pour the acid
over it
It may be necessary to heat the acid,but
boiling should be avoided.
77. Important features, which have become
standard on most units offered.
1. A small, light, easily manipulated “pencil”,
which provides a precise continuous steam of
extremely fine abrasive blasting material on
demand and under control of the operator.
78. 2. An abrasive tight compartment within which the
blasting process can be confined.
The apparatus should provide a large viewing
window and a good internal light source for
visibility.
The blasting compartment should incorporateThe blasting compartment should incorporate
restricting cuffs to fit around the wrists.restricting cuffs to fit around the wrists.
79. An adequate suction device to withdraw the
spent abrasive from the blasting
compartment
80. After recovery of casting the casting is
held in a sandblasting machine to clean the
investment from its surface
SAND BLASTER & SAND
BLASTING MACHINE
85. 1. CAD-CAM PROCESS:
Computer -Aided Designing and
Computer -Aided Machining.
Process-
involves imaging of prepared tooth.
designing the restoration in size and shape with
the help of a computer.
then machining (cutting) a ceramic or metal block
again by using a computer.
86. 2. COPY-MILLING PROCESS:
First master die is made of a prepared tooth.
Its 3-dimensions are recorded in a computer and enlarged.
A block of metal is milled to form the surface of a crown.
Another graphite die is made.
Now both graphite die and milled metal block are placed in an
electroplating bath.
After current is switched on, internal surface of the crown is
created in a metal block by copying the graphite die.
87. SIGNIFICANCE:
Casting is a very important part of dentistry.
A proper casting of a dental restoration i.e. inlay,
crown, bridge etc. can be of great use in giving
proper treatment and comfort to a patient.
A metal casting
eg. Gold alloy casting is-
indestructible in saliva.
perfect restoration can be produced.
has maximum resistance to force of mastication.
88. Thus we conclude that “casting is a complex
process involving number of steps and costly
equipment.”
A dental restoration having a perfect fit is
only possible when-
the right technique is applied.
one has good understanding of materials
used in casting.
89. DEFECTS IN CASTING:
If proper procedure is not followed the casting may
have some defects.
The defective casting may –
not fit.
have poor esthetics.
have poor mechanical properties.
Classification of Casting Defects:
(by COOMBE)
Distortion
Surface Roughness
Porosity
Incomplete Casting
Contamination
Black castings due to sulphur compounds.
TO
BE
CONTINUED
LATER…
.
90. 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
Basic Dental Materials
John J. Manappallil
91. J Dent Res. 1988 Nov;67(11):1366-70
The effect of casting ring liners on the potential expansion of a
gypsum-bonded investment.
Earnshaw R.
Effect of wet and dry cellulose ring liners on setting expansion
and compressive strength of a gypsum-bonded investment (J
Prosthet Dent 1996;76:519–23.)
Dent Mater J. 1994 Dec;13(2):240-50.
Effects of rapid burnout type gypsum-bonded investment on
performance of castings. Part 1. Surface aspects and fit of
crowns.
Murakami S, Kozono Y, Asao T, Yokoyama Y, Sera M, Lu YS,
Uchida Y.
Quintessence Int. 2007 May;38(5):e271-8.
Characteristics of commercial quick-heating phosphate-
bonded investments for the accelerated casting technique.
Yang CC, Yang HH, Ding SJ, Huang TH, Kao CT, Yan M
Quintessence Int. 2007 Feb;38(2):e78-82.
Effect of sprue design on the castability and internal porosity
in pure titanium castings.
Editor's Notes
In short it can be defined as the act of forming an object in a mould.
Dental restorations made by casting are inlays, crowns, removable partial denture frameworks, bridge etc.
Molecular weight
This provides a reservoir to compensate for the shrinkage that occurs during solidification of the casting
There is no single method of spruing that is universally accepted.
Although direct spruing can produce acceptable results, in many instances
This permits the reservoir to remain molten longer and enables it to furnish alloys to the patterns until they complete the solidification process.
With most modern machines, the crucible former is tall to allow use of a short sprue and allow the pattern to be positioned near the end of the casting ring
There are 3 types of investment materials
They all contain silica, as a refractory constituent the type of binder used is different.
Best investment should have a thermal expansion of not less than 0.1% not greater than 1.6%
Most commercial phosphate investment powders are mixed with a liquid (supplied by the manufacturer) that is predominately water with a proportion of colloidal silica, sufficient to add about 2% silica to the investment mix.
Sand is a mixture of small mineral particles predominantly composed of silica the particles represent a mixture of colors, making sand abrasives distinct in appearance.
Sand particles have a rounded to angular shape.
Revising Again in brief…….
Investing and casting, a series of highly technique sensitive steps,converts the wax pattern into a metal casting.
Accurate and smooth restorations can be obtained if the operator pays special attention to each step in the technique.