The document discusses agar and alginate as hydrocolloid impression materials. It provides details on their composition, uses, types, preparation and properties. Agar is extracted from seaweed and forms a gel when cooled. It is used for full arch impressions and duplications. Alginate forms a gel through a chemical reaction with calcium sulfate. It is commonly used for complete dentures and orthodontic impressions due to its fast setting time. Both materials provide accurate impressions but alginate is more popular due to being easier to use.
Gypsum products-a topic of dental materials for dental students....
lots of knowledge...includes classification,uses,manufacturing processes etc.
COURTESY: My college friends....
A number of theories have been put forward for impressions. each having its own advantage and disadvantage.
Different spacers guide and aid in in making the desired impression with adequate pressure in the desired region of the arch in maxilla and mandible. different materials are used for spacers depending on the need.
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.
Gypsum products-a topic of dental materials for dental students....
lots of knowledge...includes classification,uses,manufacturing processes etc.
COURTESY: My college friends....
A number of theories have been put forward for impressions. each having its own advantage and disadvantage.
Different spacers guide and aid in in making the desired impression with adequate pressure in the desired region of the arch in maxilla and mandible. different materials are used for spacers depending on the need.
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.
Impression material are used to register or reproduce the form and the relationship of the teeth and the oral tissue, the area involved may vary from a single tooth to the whole dentition, or an impression may be made of an edentulous mouth.
Hydrocolloids and synthetic elastomeric polymer are among the materials most commonly used to make impressions of various areas of the dental arch.
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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.
Hydrocolloids /certified fixed orthodontic courses by Indian dental academy Indian dental academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.
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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.
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
Smoking is a major public health problem. Cigarette smoking acts as a nicotine delivery in humans, has found to produce profound changes in physiological architecture. Smoking’s as well as chronic pain are one of the major challenging health concerns faced in day to day life. During smoking nicotine is quickly absorbed into the blood stream within a time gap of 30 seconds it reaches the brain. It stimulates the brain to release various chemicals namely epinephrine which will give a pleasurable euphoric effect. It is a proven fact that smoking of tobacco will cause the production of Rheumatoid factors or anti-cyclic citrullinated peptide autoantibodies which is a risk factor for the development of Rheumatoid arthritis. There is a positive relation between smoking and depression and it has been seen smokers use more number of cigarettes when depressed and smoking also caused the individual who is depressed more prone to pain than a normal smoker. Quitting of smoking is quite difficult because of unpleasant withdrawal syndrome that consists of frustration, depression, anxiety, reduced heart rate, increased weight, depressed mood, difficulty in concentration. Because of all these withdrawal symptoms individuals who try to quit start up again very soon. Smoking is a health hazard, this is a well-known fact and the noxious effects are multiple so in management of pain in theseindividual’s, necessary steps has to be put forward in order to quit the habit. Cognitive behavioural therapy or antidepressant therapy in the management of pain of depressed patients who are smokers has shown good results in a rehabilitation centre on the course of the management of pain.
Taurodontism, a dental anomaly is defined as a change in tooth shape caused by the failure of
Hertwig’s epithelial root sheath to invaginate at the proper horizontal level. Enlarged and elongated
pulp chamber, apically shifted pulpal floor, and lack of constriction at the level of the cementoenamel
junction are the characteristic features. In performing root canal t
appreciate the complexity of the root canal system, canal obliteration, configuration, and the potential
for additional root canal systems. Careful exploration of the all orifices with the help of magnification,
ultrasonics and a modified filling technique are useful for its better management.
Smear layer is a controversial topic in the field of operative dentistry and endodontics. This presentation includes composition, concepts, structure, advantages, disadvantages, and removal methods of smear layer.
This presentation is all about restoration of endodontically treated teeth, prefabricated post and core, cast post and core, direct and indirect technique.
This presentation describes about evolution of nitinol (NiTi), its properties, manufacturing, metallurgy and various rotary systems in the field of endodontics.
About failures of root canal treatment and retreatment. This presentation describes about various techniques for gutta percha removal, posts removal, pastes removal, and removal of separated instrument
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.
ARTIFICIAL INTELLIGENCE IN HEALTHCARE.pdfAnujkumaranit
Artificial intelligence (AI) refers to the simulation of human intelligence processes by machines, especially computer systems. It encompasses tasks such as learning, reasoning, problem-solving, perception, and language understanding. AI technologies are revolutionizing various fields, from healthcare to finance, by enabling machines to perform tasks that typically require human intelligence.
Report Back from SGO 2024: What’s the Latest in Cervical Cancer?bkling
Are you curious about what’s new in cervical cancer research or unsure what the findings mean? Join Dr. Emily Ko, a gynecologic oncologist at Penn Medicine, to learn about the latest updates from the Society of Gynecologic Oncology (SGO) 2024 Annual Meeting on Women’s Cancer. Dr. Ko will discuss what the research presented at the conference means for you and answer your questions about the new developments.
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
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
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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
New Directions in Targeted Therapeutic Approaches for Older Adults With Mantl...i3 Health
i3 Health is pleased to make the speaker slides from this activity available for use as a non-accredited self-study or teaching resource.
This slide deck presented by Dr. Kami Maddocks, Professor-Clinical in the Division of Hematology and
Associate Division Director for Ambulatory Operations
The Ohio State University Comprehensive Cancer Center, will provide insight into new directions in targeted therapeutic approaches for older adults with mantle cell lymphoma.
STATEMENT OF NEED
Mantle cell lymphoma (MCL) is a rare, aggressive B-cell non-Hodgkin lymphoma (NHL) accounting for 5% to 7% of all lymphomas. Its prognosis ranges from indolent disease that does not require treatment for years to very aggressive disease, which is associated with poor survival (Silkenstedt et al, 2021). Typically, MCL is diagnosed at advanced stage and in older patients who cannot tolerate intensive therapy (NCCN, 2022). Although recent advances have slightly increased remission rates, recurrence and relapse remain very common, leading to a median overall survival between 3 and 6 years (LLS, 2021). Though there are several effective options, progress is still needed towards establishing an accepted frontline approach for MCL (Castellino et al, 2022). Treatment selection and management of MCL are complicated by the heterogeneity of prognosis, advanced age and comorbidities of patients, and lack of an established standard approach for treatment, making it vital that clinicians be familiar with the latest research and advances in this area. In this activity chaired by Michael Wang, MD, Professor in the Department of Lymphoma & Myeloma at MD Anderson Cancer Center, expert faculty will discuss prognostic factors informing treatment, the promising results of recent trials in new therapeutic approaches, and the implications of treatment resistance in therapeutic selection for MCL.
Target Audience
Hematology/oncology fellows, attending faculty, and other health care professionals involved in the treatment of patients with mantle cell lymphoma (MCL).
Learning Objectives
1.) Identify clinical and biological prognostic factors that can guide treatment decision making for older adults with MCL
2.) Evaluate emerging data on targeted therapeutic approaches for treatment-naive and relapsed/refractory MCL and their applicability to older adults
3.) Assess mechanisms of resistance to targeted therapies for MCL and their implications for treatment selection
Couples presenting to the infertility clinic- Do they really have infertility...Sujoy Dasgupta
Dr Sujoy Dasgupta presented the study on "Couples presenting to the infertility clinic- Do they really have infertility? – The unexplored stories of non-consummation" in the 13th Congress of the Asia Pacific Initiative on Reproduction (ASPIRE 2024) at Manila on 24 May, 2024.
micro teaching on communication m.sc nursing.pdfAnurag Sharma
Microteaching is a unique model of practice teaching. It is a viable instrument for the. desired change in the teaching behavior or the behavior potential which, in specified types of real. classroom situations, tends to facilitate the achievement of specified types of objectives.
Recomendações da OMS sobre cuidados maternos e neonatais para uma experiência pós-natal positiva.
Em consonância com os ODS – Objetivos do Desenvolvimento Sustentável e a Estratégia Global para a Saúde das Mulheres, Crianças e Adolescentes, e aplicando uma abordagem baseada nos direitos humanos, os esforços de cuidados pós-natais devem expandir-se para além da cobertura e da simples sobrevivência, de modo a incluir cuidados de qualidade.
Estas diretrizes visam melhorar a qualidade dos cuidados pós-natais essenciais e de rotina prestados às mulheres e aos recém-nascidos, com o objetivo final de melhorar a saúde e o bem-estar materno e neonatal.
Uma “experiência pós-natal positiva” é um resultado importante para todas as mulheres que dão à luz e para os seus recém-nascidos, estabelecendo as bases para a melhoria da saúde e do bem-estar a curto e longo prazo. Uma experiência pós-natal positiva é definida como aquela em que as mulheres, pessoas que gestam, os recém-nascidos, os casais, os pais, os cuidadores e as famílias recebem informação consistente, garantia e apoio de profissionais de saúde motivados; e onde um sistema de saúde flexível e com recursos reconheça as necessidades das mulheres e dos bebês e respeite o seu contexto cultural.
Estas diretrizes consolidadas apresentam algumas recomendações novas e já bem fundamentadas sobre cuidados pós-natais de rotina para mulheres e neonatos que recebem cuidados no pós-parto em unidades de saúde ou na comunidade, independentemente dos recursos disponíveis.
É fornecido um conjunto abrangente de recomendações para cuidados durante o período puerperal, com ênfase nos cuidados essenciais que todas as mulheres e recém-nascidos devem receber, e com a devida atenção à qualidade dos cuidados; isto é, a entrega e a experiência do cuidado recebido. Estas diretrizes atualizam e ampliam as recomendações da OMS de 2014 sobre cuidados pós-natais da mãe e do recém-nascido e complementam as atuais diretrizes da OMS sobre a gestão de complicações pós-natais.
O estabelecimento da amamentação e o manejo das principais intercorrências é contemplada.
Recomendamos muito.
Vamos discutir essas recomendações no nosso curso de pós-graduação em Aleitamento no Instituto Ciclos.
Esta publicação só está disponível em inglês até o momento.
Prof. Marcus Renato de Carvalho
www.agostodourado.com
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.
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
2. CONTENTS
Hydrocolloids.
Sol-Gel Transformation.
Agar Agar
Introduction
Uses
Composition
Preparation
Types
Manipulation
Properties
Impression techniques.
Alginate
Introduction
Composition
Uses
Types
Chemistry
Manipulation
Packaging
Shelf Life
Properties
Latest advances
Types of Failure
Disinfection of
impression material
Conclusion
Refrences
2
3. HYDROCOLLOIDS
HYDROCOLLOID are lyosol basically
consists of gelatin particles
suspended in water and water is the
dispersion medium .
Solution – uniformly dispersed solute
and solvent e.g. salt in water – exist as
a single phase
Suspension – visible insoluble
particles in solute e.g. dust in water
Emulsion – visible insoluble liquid in
liquid e.g. oil in water
3
4. Solvent and Solute
Solution
single phase, which
means a homogenous
mixture, where the solute
exists as small molecules
or ions in the solvent.
Colloids
Emulsion
heterogeneous two-phase
system, a dispersed phase
of particles of at least
sufficient size to be seen
microscopically, dispersed
in a medium.
Hydrocolloids
4
5. SOL-GEL TRANSFORMATION
Hydrocolloids can exist in 2 different forms – SOL
and GEL.
Sol – has the appearance & characteristics of a
viscous liquid.
Gel – a jelly like elastic semi-solid – produced from
sol by a process called GELATION – by formation of
fibrils or chains or micelles of the dispersed phase
which become interlocked – brush heap structure
GELATION – thus, the conversion of sol to gel .
5
7. It occurs in two ways.
1. By temperature changes:
Gelation is brought about by a reversible process. E.g.
Agar. The fibrils are held together by secondary molecular
forces. So that they break at slightly elevated temperature
and become reestablished as the hydrocolloid cools to
room temperature.
The temperature at which these changes occurs is the
Gelation temperature.
The Gel is converted to sol when it is heated to a higher
temperature which is known as Liquification
temperature.
The temperature lag is known as hysterisis.
7
8. 2. By chemical change
Conversion of sol to gel is brought about by chemical
reaction, the fibrils thus formed are held together by
primary bonds and are unaffected by temperature.
Hence they are called irreversible hydrocolloid e.g.
Alginate.
Gel can be converted to sol (liquid) by heating,
cooling a sol causes it to become a gel.
Agar (hot) cool to 43 C Agar (cold)
(Sol) heat to 100 c (gel)
8
10. 1925 – Alphous Poller – Negacol.
Modified & introduced in dental
profession as Dentacol in 1928.
Agar is an organic hydrophilic colloid
(polysaccharide) extracted from certain types of
seaweed( kelp plant).
It is a sulphuric ester of a linear polymer of galactose.
10
INTRODUCTION
11. USES OF AGAR:
1. Widely used at present for cast
duplication .
2. For full mouth impression without deep
undercuts .
3. As tissue conditioner.
4. Was used for crown & bridge before the
11
12. COMPOSITION
Water - 84 % - dispersion medium
Agar - 13 - 17 % - gelling agent, dispersed
phase
Borates - 0.2 - 0.5% - improves strength and
retards
setting of plaster or
stones
K sulphate - 1 - 2% - it counters the retarding
effect of borates and provide good surfaces on
gypsum models/dies
Alkyl benzoates - 0.1 % - preservatives
Fillers like diatomaceous earth, clay, silica, wax, rubber,
and
inert powders for control of strength, viscosity and
rigidity.
12
13. COMMERCIAL BRANDS
Acculoid / Cartrilloid (Van R)
Sugident (Lactona)
Cohere / SuperBody / SuperSyringe (Ghingi-pak)
Indentic (Cadco)
SUPPLIED AS
solid gel in collapsible tubes (for impressions)
No. of cylinders in a glass jar (syringe material)
In bulk containers (for duplication)
13
14. PREPARATION OF AGAR
Cleanliness, maintenance, and care of the conditioner
and strict adherence to time and temperature are
mandatory.
The water pots should be clean and free of any foreign
material, eg, wax, calcium deposits, and "scum" from
the boiling water.
Conditioners stay clean.
Failure to keep the pots clean will result in temperature
variations.
14
15. The conditioner is turned on.
Thirty minutes should be allowed for the water to reach
the desired temperatures before proceeding.
The boiling pot temperature should be maintained.
The water is brought to a boil, and boiling is continued
for 10 minutes.
Tooth preparation – should be caries free , without
undercuts( if present – should be filled with cements
resins or composites)
The cervical margins should be distinct.
15
16. TYPES OF AGAR
1. Heavy bodied – in poly tubes or flex
skins
2. Medium bodied
3. Regular bodied
4. Light bodied – in syringes 16
•Trays should be selected and tried in the
patient's mouth before the impression material is
placed in them.
•There should be 3 mm of impression material
around the teeth occlusally and laterally.
17. MANIPULATION
The following steps are recommended
Heat in water at 100° C (212° F) for 8 - 10 minutes.
Store in water at 65° C (149° F) for 8-10 hours
Place in a tray at 65° C (149° F)
Temper in 46° C (115° F) water for 2 minute before taking the
impression to increase the viscosity and pressure applied
to the syringe material, also making comfortable for the
patient.
The solution is taken directly from the
storage compartment, is first ejected at the
base of the preparation and then the
remainder of the prepared tooth is covered.
17
18. In the meantime, tray material is tempered,
water soaked outer layer is soaked with a dry
guaze before placing to ensure good union
between tray and syringe material. The tray
material is positioned with passive pressure.
ADA specifications no.11 specifies that gelation
temperature must not be less than 37°C (98.6°F)
or more than 45°C (113°F).
Gelation is accomplished by circulating cool
water with a time not less than 5 minutes.
After gelation, impression is withdrawn in one
piece, parallel to line of withdrawal of prepared
tooth. 18
19. Excess is trimmed and impression is stored in 2 %
potassium sulfate, controls water volume and has better
surface integrity in stone for 5 to 20 mins.
The potassium sulfate solution gives a harder surface to
the stone die material.
The potassium sulfate should not be washed out of the
impressions before the dies are poured.
The impression must be blown carefully; the impression
should not be dehydrated, but an excessive amount of
water or moisture should not be left in the impression.
Impression must be poured immediately after retrieval,
and disinfected with iodophor, bleach or glutaraldehyde.
The cast should be kept in contact with impression for at
least 30minutes, or preferably 60 minutes.
19
21. BOILING /
LIQUIFACTION
SECTION
• 1 0 mins in boiling water (1 0 0 c)
• Every time material is reliquified, 3
mins should be added. this is
because it is more difficult to break
down the agar brush heap structure
after a previous use.
STORAGE
SECTION
• 65 – 68ºC Temp. is ideal. It can be
Stored in the sol condition till
needed.
TEMPERING
SECTION
46ºC for 2-10 mins with material
loaded in the tray.
CONDITIONING
UNIT
21
22. PROPERTIES
1. Gelation Temperature - after boiling for 8
minutes, the material should be fluid enough to
be extruded from the container. After tempering,
the sol should be homogeneous and should set to
a gel between 37" and 45" C when cooled.
2. Permanent deformation - The ANSI/ADA
Specification requires that the recovery from
deformation be greater than 96.5% (permanent
deformation be less than 3.5%) after the material
is compressed 20% for 1 second.
22
23. 3. Flexibility - 4% to 15%. Materials with low flexibility
can be accommodated in areas of undercuts by
providing somewhat more space for the impression
material so it is subjected to a lower percentage of
compression during removal.
4. Strength –
compressive strength - 8000 g/cm2.
tear strength - 800 to 900 g/ cm.
Because agar hydrocolloid impressions are viscoelastic,
the strength properties are time dependent, and higher
compressive and tear strengths occur at higher rates of
loading.
5. Compatibilty with gypsum - Agar is more compatible
with gypsum model materials than alginates 23
24. 6. Distortion during gelation
Contraction occurs during physical change from
sol to gel.
If the material is held rigidly in the tray , material
will shrink towards the centre of its mass , thereby
creating larger dies.
Since sol is the poor thermal conductor , rapid
cooling may cause conc. Of stress near the tray
where gelation first takes place.
Therefore water at 20 degree celcius is suitable for
cooling.
24
25. IMPRESSION TECHNIQUES
Full arch impression
Sectional arch impression
Sectional arch impression techniques follows
same procedure as for full arch.
Selected tray should cover the tooth and its
adjacent two or more teeth.
Indication:
1. Working model for inlay preparation.
2. Single or more teeth preparation.
25
26. LAMINATE TECHNIQUE: - [Schwartz (1951)]
It is a modified procedure using both reversible and
irreversible hydrocolloid. Tray hydrocolloid is
replaced with a mix of chilled alginate that bonds
syringe agar. Alginate sets by chemical reaction
whereas agar by temperature change.
The equipment needed for taking an agar impression
can be minimized by use of an agar-alginate, syringe-
tray combination impression.
In this procedure a syringe type of agar in a cartridge
is heated in boiling water for 6 minutes and stored in
a 65'c water bath 10 minutes before use.
The tray alginate of the regular set type is mixed with
10% more water than normally recommended and it
is placed in a tray.
26
27. The agar is injected around the preparation and the mixed
alginate is promptly seated on top of the agar. The alginate
sets in about 3 mins, and the agar gels within this time as a
result of being cooled by the alginate.
During the setting of the alginate and gelling of the agar a
bond forms between them. The impression may be removed
in about 4 minutes.
Since the hydrocolloid, not the alginate, is in contact with the
prepared teeth, maximum detail will be reproduced.
bond together better than others, with tensile bond strengths
ranging from 600 to 1100gm/cm2.
Values at the high end of the range resulted in cohesive
failure of the agar, where as those at the low end produced
adhesive failure between the agar and the alginate. It is
therefore advisable to follow the manufacturer's suggestions
for appropriate combinations.
27
28. ADVANTAGES
Agar provides tissues details and solidifies
when it comes in contact with alginate
prepared in water at 70°F, Preventing rapid
gelation.
the elimination of water-cooled
impression trays.
agar is more compatible with gypsum
model materials than alginates.
the accuracy is acceptable.
Economical and simple.
Liquification and storage of agar not
required
Decreased setting time (3minute). 28
29. WET FIELD TECHNIQUE
In this, tooth surfaces are purposely left wet and
areas are actually flooded with warm water.
The syringe material is introduced quickly,
liberally and in bulk to cover occlusal / incisal
areas only.
While the syringe material is still liquid, tray
material is seated, the hydraulic pressure of the
viscous tray material forces the syringe material
into areas to be restored.
This motion displaces the syringe material,
blood and debris throughout the sulcus. 29
30. ADVANTAGES OF AGAR
1. Helps in preparing dies accurately.
2. Good elastic property and reproduces
most undercut areas.
3. Good recovery from distortion.
4. Non hydrophobic.
5. Palatable and well tolerated.
6. Cheap.
7. Can be reused.
30
31. DISADVANTAGES
Does not flow properly.
Cannot be electroplated.
Due to heat , it may be painful.
Tears relatively easily.
31
33. The word Alginate comes from ‘Algin’ which is a
peculiar mucous extract yielded by certain brown
seaweed.
Alginates are based on anhydro-ß-d mannuronic
acid or anhydro-P-D-guluronic acid.
S. Willium Wilding 1940s introduced.
Alginate was used as a substitute for agar when it
became scarce during World War II (Japan was a
prime source of agar)
Current status – alginate more popular than agar
.
33
34. COMPOSITION
1. Ester salt of alginic acid (sodium or potassium
or triethanolamine alginate) – 15 % - dissolves
in water and reacts with calcium ions to form
gel.
2. Calcium sulphate – 16 % - reacts with
potassium alginate & forms insoluble calcium
alginate
3. Zinc oxide – 4 % - filler and influences physical
properties and setting time of the gel.
4. Potassium titanium fluoride/silicate or k
sulphate – 3 % - gypsum hardener
34
35. 6. phosphate – 2 % - retarder and Delays gelation by
reacting with calcium sulphate in preference to
soluble alginate to form insoluble gel.
7. Glycol - small amount - To make powder dustless
8. Chemical indicators - small amount
pH changes from alkaline to neutral to indicate
different stages in manipulation
Violet – during spatulation
Pink - ready to load
White - ready for insertion into mouth
9. Wintergreen/peppermint - trace amount
10. Disinfectants ( ammonia salts and CHX) - small
amount
35
36. USES
1. Complete denture prosthesis & orthodontics
2. Mouth protectors
3. Study models and working casts
4. Duplicating models
TYPES:
Type I – Fast setting.
Type II – Normal setting.
36
38. CHEMISTRY The alginate when mixed with water becomes a
sol. Gelation occurs by a chemical reaction .
The simplest and the popular method is reacting
the soluble alginate with calcium sulphate to
produce insoluble calcium alginate gel.
Chief ingredient is one of the soluble alginates
which is a linear polymer of the sodium salt of
anhydro-beta-d-mannuronic acid.
Calcium sulfate (Reactor) reacts with potassium
or sodium alginate in an aqueous solution.
38
39. Production of Calcium alginate is delayed by the
addition of soluble salts acting as retarder like
sodium or potassium phosphate, oxalate or
carbonate.
2Na3PO4 + 3CaS04 Ca3(PO4) + 3Na2SO4
When supply of sodium phosphate is exhausted,
calcium ions begin to react with potassium
alginate to produce calcium alginate.
K2Alg + CaSO4 + H2O K2SO4 + Ca Alginate.
ADA no 18 describes two types of alginates
Type I (fast setting) - 1 to 2 min
Type II (normal setting) - 2 to 4.5 minutes
39
40. MANIPULATION
Fluff or aerate the powder by inverting the
container with the lead on several times –
ensures uniform distribution.
A clean flexible plastic bowl, a clean wide bladed
stiff metal / plastic spatula.
Tray selection : perforated metal rim lock tray or
plastic tray with retentive holes.
An excess of saliva around the teeth should be
removed -may cause bubbles in the
interproximal areas and on the occlusal surfaces
of the teeth. 40
42. 42
•Powder is added to liquid to wet the powder
with water and to reduce entrapment of air.
•One scoop of pre-dispensed powder products
is used with the amount of water specified by
manufacturer (16g of powder to 38 ml of
water)
•Once the powder is moistened, rapid
spatulation by swiping, or stropping against
the side of the bowl.
•A vigorous figure of 8 motion
can also be used.
43. Mix by hand spatulation / mechanical
spatulation with or without vacuum vigorously
for smooth creamy mix with minimum voids
(mixing time 45sec- 1 min) .
Air bubbles can be minimized by careful
application of the impression material to tooth
and into vestibular area with finger pressure
before placement of filled tray.
43
44. Filled tray is held passively and motionlessly and
material is left for 2 -3 minutes, till it becomes firm
because of adequate maturation of chemical set.
The thickness of the gel between tray and the tissues
should be 3 mm .
Working time 1 – 2 min
44
45. Tray should separated immediately suddenly with a jerk -
to avoid rocking and possible deformation of impression.
Excess material is trimmed .
The impression is washed in cold water to remove saliva
stored in an environment of 100% humidity or covered
with a damp napkin to prevent drying.
Impression should be poured within 10 mins for accuracy.
Cast should be separated from alginate impression as
soon as the stone has reached the optimal stage of rigidity
i.e. after 45 - 60 minute.
45
48. If allowed to remain for longer time, alginate
dehydrates and damaging changes take place in the
surface of stone.
The mixing time also affects strength of the gel
structure. The strength of gel can be reduced as
much as 50% if mix is not complete.
Under mixing can lead to grainy mix which leads
to reduced tissue detail reproduction.
Prolonged mixing results in weakened gel
structure as fibrils once formed will be broken
up. This will also lead to reduced working time 48
49. Manual Technique
A mixing time of 45 seconds to 1 minute is
sufficient .Mixing should result in a smooth creamy
mix that does not drip off the spatula, when it’s
raised from the bowl.
49
50. Automated Technique
A variety of mechanical devices are available for
spatulating the alginate impression material. The
required quantity of powder and water are
dispensed in a bowl. Spatulation is
carried out until a smooth creamy mix
of alginate is obtained. This results in a
superior mix than obtained manually.
50
51. PACKAGING
Alginate is supplied as a powder i.e. packaged in bulk
in a sealed screw top plastic container or hermetically
sealed metal can. A plastic scoop and cylinder is
provided .
Preweighed packets constructed of plastic or metal
foil. it increase storage life and decrease moisture
contamination.
Automatic mixing systems have been developed for
paste/paste alginates. These systems consist of a
mixing unit that mixes
- an aqueous base paste – sodium alginate polyacrylic
acid
- an organic initiator paste - calcium sulphate-
hemihydrate and sodium
phosphate. 51
52. SHELF LIFE
Alginate impression material deteriorates rapidly at
elevated temperatures by depolymerisation of the
alginate constituent. Materials stored for one
month at 65 degree Celsius are unstable for use as
they do not set at all or set too rapidly for any
practical use. Even at 54 degree Celsius there’s
evidence of deterioration.
The ADA specification number 18 for alginate
impressions specify that storage within original
container for 1 week at 60 degree Celsius in a
relative humidity of 100% the compressive strength
of the gel should not be less than 0.255Mpa.
52
53. POURING THE CAST
The pouring of the cast should start from one end of
arch. Afterwards it is placed in a humidator while stone
hardens. Stone cast or die should be kept in contact
with the impression preferably for 60 minutes or for a
minimum of 30 minutes.
NEW METHOD
A proper dental stone mixed with an accelerator is
painted over the entire anatomic surface of the
impression. A base is added only after the first
application of stone sets. This method protects against
volume change of the irreversible hydrocolloid
impression material and distortion of the unsupported
portions of the impression.
53
54. ADVANTAGES
Easy to manipulate
Comfortable for patient
Economical
Viscosity and setting time can be altered.
Hydrophilic nature allows small presence of water on the
tissues
without causing major inaccuracies in the impression.
DISADVANTAGES
Distortion begins immediately after removal from the
mouth .
Surface details and accuracies are poor.
Retention of alginate to non-perforated trays is
inadequate. 54
55. PROPERTIES1. Taste & odor: variety of colors and flavors.
2. Flexibility : 14% at a stress of 1000 gm/cm2.
3. Elastic recovery : 97.3%
Permanent deformation is less if set impression is
removed from mouth quickly.
The ANSI/ADA Specification requires that the
recovery from deformation be more than 95% (or a
permanent deformation of less than 5%) when the
material is compressed 20% for 5 seconds at the
time it would normally be removed from the mouth.
55
56. 4. Reproduction of tissue details : lower than agar.
ADA Sp. Requires material to reproduce a line that
is 0.075 mm width.
5. Strength :
Compressive strengths – 5000-8000 gm/cm2
Tear strength - 350-700 gm/cm2
6. Dimensional stability: poor
7. Storage : cool, dry, tightly closed lid.
56
58. CONTROL OF SETTING TIME
Lengthening the setting time is better accomplished by reducing
the temperature of the water used with the mix than by reducing
the proportion of powder.
Reducing the ratio of powder to water reduces the strength and
accuracy of the alginate.
The setting reaction is a typical chemical reaction, and the rate can
be approximately doubled by a temperature increase of 10" C.
using water cooler than 18" C or warmer than 24" C is not advisable.
The clinical setting time is detected by a loss of surface tackiness.
58
59. CONTROL OF GELATION TIME
The gelation time is measured from the beginning of
the mixing until gelation occurs. It must allow
sufficient time for the dentist to mix the material, load
the tray and place it in the patient’s mouth.
Once gelation starts the impression must not be
disturbed because growing fibres will be fractured
and impression would be sufficiently weakened.
Optimal gelation time - 3 – 4 mins at temperature of
200C.
ADA specification no:18 for alginate have described
two types of alginate based on gelation time.
Type I (fast setting) : 1 – 2 minutes
Type II (normal setting) : gelation time 2.5 - 4
mins 59
60. Gelation time is best regulated by the amount
of retarder added during manufacturing.In
another way the clinician can safely
influence gelation time by altering the
temperature of water used to mix the
impression material.
Increase in temperature
leads to a decrease in
gelation time and vice
versa. However using
water cooler than 180C
and warmer than 54 c
is not recommended. 60
61. COMPATIBILITY WITH
GYPSUM
Gypsum casts is not compatible with both type of
hydrocolloid impression. To ensure maximum surface
hardness, methods employed are :
1. Immersing the impression in a solution containing an
accelerator for setting of gypsum products before
pouring impression with gypsum. This acts by two
ways
(a) accelerates setting of gypsum.
(b) Reacts with gel to produce a surface layer that
reduces or prevents syneresis and eliminates the
retarding action of the gel.
Potassium sulphate, Zinc sulphate, manganese
sulphate, potash alum etc are chemicals usually used in
hardening solutions. Most effective is 2% K2SO4
solution. 61
62. 2. Incorporating a plastic hardener or accelerator in
the material by the manufacturer. Potassium
titanium fluoride is most commonly used
hardening agent.
In general a hardening solution is not required
unless specified by the manufacturer as most of the
commercially available alginates contain a hardener
in them.
62
63. LATEST ADVANCES
MODIFIED ALGINATES:
1. In the form of a sol, containing the water. A reactor of
plaster of Paris is supplied separately.
2. Paste system, one containing the alginate sol, the
second the calcium reactor. These materials are said
to contain silicone and have superior tear resistance.
63
64. 3. ALGINOT
it is an extremely cost-effective, reliable
alternative.
High quality material that delivers accuracy and
performance.
Available in a faster set time to increase patient
comfort and reduce chair time without
compromising performance or working time.
The improved thixotropic consistency reduces
slumping and displacement from the impression
tray.
Indications: Preliminary impressions, provisional
crown and bridge impressions, study models,
registration/opposing dentition impressions,
impressions for orthodontic models, sports guards,64
65. 4. SILGINAT(Kettenbach LP)
It is a medium viscosity addition-curing elastomeric
polyvinyl silioxane impression material with alginate-like
consistency, specially developed for taking impressions of
the opposing jaw, temporary crowns/bridges and fabricating
splints.
The use of an A-silicone for opposing jaw impressions as well
as for precision impressions and bite registration leads to an
optimal standardized interaction.
Silginat is stable, has a low tear resistance and is easy to
disinfect.
Quantity - Cartridge (38 mL)
Working Time - 76 - 90 seconds
Complete Set Time - 2 min 30 secs
Viscosity - Medium Body
Set Times Available - Regular Set 65
66. 5. SILGINAT FOIL BAG ALGINATE
SUBSTITUTE MATERIAL
Quantity Foil Bag - (362 mL)
Working Time - 90 seconds
Dispensing Plug & Press Dispensing System
Complete Set Time - 3 minutes
Viscosity - Medium Body
Set Times Available - Regular Set
66
67. 6. STATUSBLUE(dmg america)
StatusBlue is an efficient, clean and stable alginate alternative.
A-silicone formula makes it quick and easy to take situation
impressions for temporaries, model-cast dentures, orthodontic
models, and opposing jaw models.
100% dust-free and cold disinfected, allowing for clean and safe
impression taking and delayed pouring, or re-pouring of
impressions.
Quantity - StatusBlue for Automix Guns Canister 7 (+1 FREE)
50ml Cartridges 16 Automix Tips
Working Time - 1:15
Dispensing - Gun
Complete Set Time - 1:45
Viscosity - Type Medium Bodied ( < 35mm)
Set Times Available - 1:45
67
68. 7. FREEALGIN MAXI
( Zhermack , inc)
A-silicone, alginate alternative, fast setting, medium
viscosity for all alginate indications. Packaged for all
automatic mixing machines.
1:1 mixing ratio.
Quantity - 6 X 380 mL Cartridge
base and catalyst
2 bayonet ring
Dispensing - Automatic Mixing
Machine
Scent/ Flavor - Mangustan Flavour
68
69. 8.POSITION™ PENTA™ QUICK VPS
ALGINATE REPLACEMENT
Accurate, dimensionally stable preliminary
impressions that take less time.
The material offers a fast working
and setting time, and is ideal for all
typical alginate impression indications.
Multiple pour capabilities save time and money, no
need to pour immediately, and no cleaning of bowls
and spatulas.
it is dispensed at the touch of a button through 3M
ESPE’s fully automated Pentamix™ 3 Automatic Mixing69
70. Quantity - Kit includes: 1 base paste – 300ml; 1 catalyst
– 60ml; 1 Penta™ cartridge, lavender; 6 Directed Flow
Impression Trays (1 each size S, M, L, Upper and
Lower)
Working Time - 1 min 10 sec (including mixing)
Dispensing - Automatic Mixer
Complete Set Time - 2 min 40 sec
Viscosity - Medium Bodied
Set Times Available - 3 min (Position Penta) and
2 min 40 sec (Position Penta Quick)
70
71. 9.ANTISEPTIC ALGINATE
IMPRESSION MATERIAL
Introduced by Tameyuki Yamamoto,
patented in 1990.
An antiseptic containing alginate impression
material contains 0.01 to 7 parts by weight of an
antiseptic such as glutaraldehyde and
chlohexidine gluconate per 100 parts by weight of
a cured product of an alginate impression
material.
The antiseptic may be encapsulated in a
microcapsule or clathrated in a cyclodextrin. 71
72. 10. CAVEX COLOR CHANGE
Material with color indications
avoiding confusion about setting time.
Color changes visualizes the major
decision points in impression making
initially - white
end of mixing time - violet
end of setting time – pink to white
Other advantages of this material are
improved dimensional stability (upto 5 days)
Good tear and deformation resistance
Dust free
Smooth surface, optimum gypsum compatibility.
72
73. 11.LOW DUST ALGINATE
IMPRESSION MATERIAL Introduced by Schunichi in 1997.
This composition comprises an alginate a gelation
regulator and a filler as major components which
further comprises sepiolite and a
tetraflouroethylene resin having a true specific
gravity from 2-3.
The material generates less dust, has a mean
particle size of 1-40microns.
73
74. ADVANTAGES
Easy mixing
Excellent stone surface
Unsurpassed smoothness
Fine detail
Packed in 1 lb poly- aluminium pouches to increase
shelf life and reduce storage space.
2 scoops impression per pound.
Available in 2 forms – identic dustfree and
kromaFaze
74
75. ALGINATE
Material changes colour signaling
when to carry out each stage of the
procedure
Purple – spatulate
Pink – load tray
white – insert for impression
The color change is because of the indicator
present: PHENOLPHTHALEIN
Total elapsed time from start to
finish is just over 1 minute.
Impression can be kept over 100
hours without distortion or
shrinkage by simply rinsing and
enclosing in a plastic bag.
75
76. 13. ALGINMAX (FUNG INT.)
High precision chromatic dental alginate.
Excellent dimensional stability allows casting of
the impressions even after 5 days (if impressions
are correctly stored in sealed containers).
Dust free alginate and lead and cadmium free.
Excellent gypsum compatibility and
biocompatibility.
Very high compressive strength and recovery
from deformation.
Flavour – vanilla mint
Color – pale blue
Setting time – 3 min
Shelf life – 3 years
76
77. 77
Specifically designed for use with
any automatic delivery and mixing
system, Kettosil incorporates all of
the advantages of polyvinyl siloxane for accurate, fast
and easy impressions in any indication where an alginate
would normally be used .
Excellent Dimensional Stability.
Extremely low linear dimensional change value of 0.20%
comparable to polyvinyl siloxanes.
fullest possible recovery after removal from mouth, low
shrinkage during setting
14. KETTOSIL
78. Kettosil impressions can be poured 30 minutes
after removal from the mouth and up to 21 days
after impression taking.
Highly thixotropic properties for smooth,
controlled flow under pressure while minimizing
material slump and patient gagging.
Supplies bubble-free reproduction of surface
detail and critical areas such as gingival crevices
and occlusal grooves.
Reproduces every oral detail in stone study or
opposing models. Perfectly defined margins.
78
79. High Recovery From Deformation of 99.2% .
No Wasted Material
Activated cartridges of Kettosil can be sealed by
leaving unused material in the filler tip.
For the next impression, simply remove the
previous tip, then dispense as per routine.
Total working time of 1 minute 20 seconds.
maintains accuracy, saves time and maximizes
patient comfort.
79
80. Agar Alginate
3)
Dimensional
accuracy
PROPERTIES
1) Flow
2) Elasticity
4)
Dimensional
stability
Excellent
Elastic
98.8%
Imbibition
and synersis
Can record fine
details
Elastic 97.3%
No dimensional
changes
Imbibition
and synersis
No
dimensional
changes
80
81. 5) Adhesion
With the tray
6) Compatibility
with Cast
Manipulation Special equipments No Special
equipments
Addition accept addition Does not accept
Tear strength
Electroplating Can not be it can be
Dipped in 2%
K2SO4
Special
perforated
tray
More
compatible.
needs perforated stock tray
Dipped in 2% K2SO4
Less compatible
81
agar alginate
82. TYPES OF FAILURES
DISTORTION -Delayed pouring of impression.
-Movement of the tray during
seating.
- Early removal from mouth.
- Improper removal from mouth.
GRAINY
IMPRESSION
- Inadequate mixing
- Prolonged mixing
- Less water in mix
TEARING - Inadequate bulk
- Moisture contamination
- Too early removal from mouth
- Prolonged mixing
82
CAUSES
83. BUBBLES - Early gelation
- Air incorporation
VOIDS - Excess moisture or
debris on tissues
ROUGH OR
CHALKY
STONE CAST
- Improper cleaning
- Premature removal of
cast
- Improper manipulation of
stone
83
84. Alginate (Irreversible hydrocolloid):
All the instrument i.e. rubber bowl, spatula are
sterilized or disinfected by spraying with 0.5%
NaOCl or 2% glutaraldehyde.
Spray technique -
Rinse under tap water to clean saliva or organic
debris.
Trim excess alginate from non-critical areas to
decrease amount of Microbial contamination.
Spray the entire impression surface and the
reverse side of the tray as well. It can be kept in
a plastic bag or humidor for the recommended
exposure time. .84
DISINFECTION OF
IMPRESSION PROCEDURE
MATERIALS
85. When it reached the lab, it is again cleaned with
water and stone cast is poured.
For immersion technique, disinfectant with
short exposure time is selected to minimize
distortion and deterioration of cast.
Aluminium sulfate treatment of alginate
impression:
After disinfection, the impression is sprayed
with aluminium sulfate and kept for 90 seconds
in a humidor.
Casts produced have better details and surface
smoothness than impression disinfected but
untreated.
85
86. CONCLUSION
Success of alginate hydrocolloid impression
material since its emergence as an alternative to
reversible hydrocolloid was mainly due to its ease
of manipulation , comfort to the patient and less
cost .
But the facts like its dimensional instability, its
incompatibility with gypsum and availability of
better alternatives like elastomers which produce
better surface detail has replaced it but still it is
the impression material of choice in the field of
dentistry.
86
87. REFERENCES Philip’s science of dental materials (11thEdition)-
Anusavice KJ
Restorative Dental Materials (11thEdition)- Craig
RG, Powers JM
Fundamentals of Fixed Prosthodontics (3rdEdition)
– Shillngberg Jr HT et al
Contemporary fixed prosthodontics – Rosensteil
Textbook of Operative Dentistry – Sikri VK
Basic dental materials – 1st edition – manapallil JJ
Operative Dentistry Modern Theory and Practice
(Indian ed. 1) - Marzouk MA, Simonton AL, Gross RD
87
Editor's Notes
alginates rich in guluronan form strong, brittle gels, whereas those rich in mannuronan form weaker
and more elastic gels.
K ti f - To counteract the inhibitory effect of hydrocolloid on setting of gypsum and improves the surface of stone model
Diatomaceous earth - increases the stiffness and strength of the gel
produces smooth texture
ensures a firm gel surface that is not tacky
increases the flexibility of set impression
Sodiumtripolyphosphate and tetrasodium pyrophosphate are the two most common salts used
. The silaceous particle, are similar to asbestos fibres that produce fibrinogenesis and carcinogenesis. So inhalation of fumes should be avoided.