Non-elastic impression materials like impression compound and zinc oxide eugenol set via physical or chemical reactions and cannot record undercuts due to fracturing upon removal. Elastic impression materials like hydrocolloids (alginate and agar) and elastomers set viscoelastically, allowing compression in undercuts and subsequent recovery to accurately record details. Hydrocolloids exist as sols that gel upon temperature change via physical (agar) or chemical (alginate) reactions. They have high flow, flexibility, and compatibility with gypsum but shrink and are dimensionally unstable when dry.
direct filling gold... material aspect, types, condensation, cavity design, modifications. detaied seminar for post gradutes.... any doubts or suggestions contact dr.mb@hotmail.com
This presentation tells everything about composite resin from history to composition to usage protocols. A must read for all dental students before practicals and exams.
Principles and concepts of designing obturators/ orthodontic seminarsIndian 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.
Elastic impression materials /certified fixed orthodontic courses by Indian d...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.
direct filling gold... material aspect, types, condensation, cavity design, modifications. detaied seminar for post gradutes.... any doubts or suggestions contact dr.mb@hotmail.com
This presentation tells everything about composite resin from history to composition to usage protocols. A must read for all dental students before practicals and exams.
Principles and concepts of designing obturators/ orthodontic seminarsIndian 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.
Elastic impression materials /certified fixed orthodontic courses by Indian d...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.
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: 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.
A dental impression is a negative imprint of hard (teeth) and soft tissues in the mouth from which a positive reproduction (cast or model) can be formed. It is made by placing an appropriate material in a stock or custom dental impression tray which is designed to roughly fit over the dental arches.
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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.
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
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.
A dental impression is a negative imprint of hard (teeth) and soft tissues in the mouth from which a positive reproduction (cast or model) can be formed. It is made by placing an appropriate material in a stock or custom dental impression tray which is designed to roughly fit over the dental arches. Impression material is of solid or semi-solid nature when first mixed and placed in the mouth. It then sets to become an elastic solid (usually takes a few minutes depending upon the material), leaving an imprint of person's dentition and surrounding structures of the oral cavity
Impression materials for complete denture/certified fixed orthodontic courses...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
A simplified explanation of mucostatic and mucocompressive and selective pressure impression technique. difference between rigid and non rigid with the advantages and disadvantages
types of materials, manipulation techniques, uses had described in detail. based on exam point of view
Impression materials/dental implant courses 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.
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
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
Basavarajeeyam is a Sreshta Sangraha grantha (Compiled book ), written by Neelkanta kotturu Basavaraja Virachita. It contains 25 Prakaranas, First 24 Chapters related to Rogas& 25th to Rasadravyas.
These lecture slides, by Dr Sidra Arshad, offer a quick overview of the physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar lead (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
6. Describe the flow of current around the heart during the cardiac cycle
7. Discuss the placement and polarity of the leads of electrocardiograph
8. Describe the normal electrocardiograms recorded from the limb leads and explain the physiological basis of the different records that are obtained
9. Define mean electrical vector (axis) of the heart and give the normal range
10. Define the mean QRS vector
11. Describe the axes of leads (hexagonal reference system)
12. Comprehend the vectorial analysis of the normal ECG
13. Determine the mean electrical axis of the ventricular QRS and appreciate the mean axis deviation
14. Explain the concepts of current of injury, J point, and their significance
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. Chapter 3, Cardiology Explained, https://www.ncbi.nlm.nih.gov/books/NBK2214/
7. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
Adv. biopharm. APPLICATION OF PHARMACOKINETICS : TARGETED DRUG DELIVERY SYSTEMSAkankshaAshtankar
MIP 201T & MPH 202T
ADVANCED BIOPHARMACEUTICS & PHARMACOKINETICS : UNIT 5
APPLICATION OF PHARMACOKINETICS : TARGETED DRUG DELIVERY SYSTEMS By - AKANKSHA ASHTANKAR
NVBDCP.pptx Nation vector borne disease control programSapna Thakur
NVBDCP was launched in 2003-2004 . Vector-Borne Disease: Disease that results from an infection transmitted to humans and other animals by blood-feeding arthropods, such as mosquitoes, ticks, and fleas. Examples of vector-borne diseases include Dengue fever, West Nile Virus, Lyme disease, and malaria.
Tom Selleck Health: A Comprehensive Look at the Iconic Actor’s Wellness Journeygreendigital
Tom Selleck, an enduring figure in Hollywood. has captivated audiences for decades with his rugged charm, iconic moustache. and memorable roles in television and film. From his breakout role as Thomas Magnum in Magnum P.I. to his current portrayal of Frank Reagan in Blue Bloods. Selleck's career has spanned over 50 years. But beyond his professional achievements. fans have often been curious about Tom Selleck Health. especially as he has aged in the public eye.
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Introduction
Many have been interested in Tom Selleck health. not only because of his enduring presence on screen but also because of the challenges. and lifestyle choices he has faced and made over the years. This article delves into the various aspects of Tom Selleck health. exploring his fitness regimen, diet, mental health. and the challenges he has encountered as he ages. We'll look at how he maintains his well-being. the health issues he has faced, and his approach to ageing .
Early Life and Career
Childhood and Athletic Beginnings
Tom Selleck was born on January 29, 1945, in Detroit, Michigan, and grew up in Sherman Oaks, California. From an early age, he was involved in sports, particularly basketball. which played a significant role in his physical development. His athletic pursuits continued into college. where he attended the University of Southern California (USC) on a basketball scholarship. This early involvement in sports laid a strong foundation for his physical health and disciplined lifestyle.
Transition to Acting
Selleck's transition from an athlete to an actor came with its physical demands. His first significant role in "Magnum P.I." required him to perform various stunts and maintain a fit appearance. This role, which he played from 1980 to 1988. necessitated a rigorous fitness routine to meet the show's demands. setting the stage for his long-term commitment to health and wellness.
Fitness Regimen
Workout Routine
Tom Selleck health and fitness regimen has evolved. adapting to his changing roles and age. During his "Magnum, P.I." days. Selleck's workouts were intense and focused on building and maintaining muscle mass. His routine included weightlifting, cardiovascular exercises. and specific training for the stunts he performed on the show.
Selleck adjusted his fitness routine as he aged to suit his body's needs. Today, his workouts focus on maintaining flexibility, strength, and cardiovascular health. He incorporates low-impact exercises such as swimming, walking, and light weightlifting. This balanced approach helps him stay fit without putting undue strain on his joints and muscles.
Importance of Flexibility and Mobility
In recent years, Selleck has emphasized the importance of flexibility and mobility in his fitness regimen. Understanding the natural decline in muscle mass and joint flexibility with age. he includes stretching and yoga in his routine. These practices help prevent injuries, improve posture, and maintain mobilit
Local Advanced Lung Cancer: Artificial Intelligence, Synergetics, Complex Sys...Oleg Kshivets
Overall life span (LS) was 1671.7±1721.6 days and cumulative 5YS reached 62.4%, 10 years – 50.4%, 20 years – 44.6%. 94 LCP lived more than 5 years without cancer (LS=2958.6±1723.6 days), 22 – more than 10 years (LS=5571±1841.8 days). 67 LCP died because of LC (LS=471.9±344 days). AT significantly improved 5YS (68% vs. 53.7%) (P=0.028 by log-rank test). Cox modeling displayed that 5YS of LCP significantly depended on: N0-N12, T3-4, blood cell circuit, cell ratio factors (ratio between cancer cells-CC and blood cells subpopulations), LC cell dynamics, recalcification time, heparin tolerance, prothrombin index, protein, AT, procedure type (P=0.000-0.031). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and N0-12 (rank=1), thrombocytes/CC (rank=2), segmented neutrophils/CC (3), eosinophils/CC (4), erythrocytes/CC (5), healthy cells/CC (6), lymphocytes/CC (7), stick neutrophils/CC (8), leucocytes/CC (9), monocytes/CC (10). Correct prediction of 5YS was 100% by neural networks computing (error=0.000; area under ROC curve=1.0).
2. Non-elastic Impression Materials
Definition:
They are impression materials which fracture or distort upon removal
from the undercut area after setting.
They can’t record the undercut area.
Better to use them in completely edentulous patients.
Types:
1.
Impression wax.[Historical]
2.
Impression compound.
3.
Plaster.
4.
Zinc oxide & eugenol.
2
4. Impression Compound
Types:
Type I
Low fusing
compound
[soften at5060ºC]
-1ry impression
+Stock tray
-Single
impression +
Copper band
Type II
High fusing
compound
[soften
at70ºC]
Tray material to
hold 2ndry
impression
material.
Peripheral seal
4
5. Impression Compound
Composition:
1.Thermoplastic waxes & resins
Thermoplastic polymers
2.Fillers
body.
3.Gum
adhesive to the tray.
4. Plasticizers.
5. Pigments.
Setting reaction:
Being thermoplastic, it sets by physical setting reaction.[Reversible]
Impression compound[Hard] ~45ºC Impression compound [Soft]
5
6. Impression Compound
Manipulation:
1.As impression compound is of low thermal conductivity,
[Type of bonding] adequate time should be given for
uniform heating
Flow during impression
taking.
Soaking
in warm water-bath .[Sheets or cakes]
Over a flame.[Sticks]
Dry kneading with fingers.
6
7. Impression Materials
Manipulation:
Application as:
1ry impression material + stock tray.
Single impression + copper band.
Peripheral seal.
Tray material for 2ndry impression.
2. As impression compound is of low thermal conductivity,
adequate time should be given for uniform cooling.
Distortion on removal from the mouth.
7
9. Impression Compound
1.
2.
3.
Properties:
Viscous material
Low flow.[Mucocompressive technique]
.·.It can not record the fine details.
High coefficient of thermal expansion & contraction [Due to weak
intermolecular 2ry bonds]
Contraction during cooling from mouth-to room temperature 0.3-0.4%.
Rigid material:
.·.It is used only in minimum undercut.[Completely edentulous patient]
4.
Self adhesive to the tray (has gum).
9
10. Impression Compound
4.
5.
7.
Properties:
Non-elastic on removal from undercut
distortion.
Not dimensional stable during storage due to release of internal
stresses
Time + Temperature
distortion.
.·. Immediate pouring of the model is recommended.
Compatible with the model material:
a. The gypsum mix can adapt & fill the impression.
b. No separating medium is required.
c. Being thermoplastic ,the assembly [Tray + impression +
model] is immersed in warm water-bath to soften the impression
compound for easy separation from the model.
d. The single impression can be copper electroplated.
10
11. Zinc Oxide & Eugenol ZOE
Supplied form:
Two pastes of contrast colors in metallic collapsible
tubes.
11
13. Zinc Oxide & Eugenol
1.
2.
Types:
Eugenol free impression material for sensitive patients:
Other type of oil of cloves instead of eugenol.
Regarding setting time: [According to the amount of
accelerators & retarders]
Type I Hard
S.T. 10 minutes.
Type II Soft
S.T.15 minutes.
13
14. Zinc Oxide & Eugenol
Setting reaction:
It is acid base reaction.
Zinc oxide + water
Zinc hydroxide +2 Eugenol
[ZO+2Eugenol
Zinc hydroxide
Zinc eugenolate Chelate
[Salt]+H2O
Zinc Eugenolate]
14
15. Zinc Oxide & Eugenol
Setting reaction:
Chelation reaction:
It is the attachment of molecule or ion to metal ion at
more than one point.
The term Chelation is derived from the Greek word
meaning crab’s claw indicating2 projecting attachments.
A central zinc atom is held by 2 adjacent eugenol.
15
16. Zinc Oxide & Eugenol
1.
2.
3.
Manipulation:
Armamentarium:
- Oil resistant paper pad or glass slab & Stainless Steel spatula.
- Special tray.
Steps:
Two equal lengths of the two pastes.
Mix until homogeneous mix without streaks is obtained.
Factors affecting setting time:
High temperature & humidity: accelerate the setting reaction.
Cool glass slab & spatula: retard the setting reaction.
Application:
2ndry impression for completely edentulous patient + Special tray.
16
18. Zinc Oxide & Eugenol
1.
2.
3.
4.
5.
6.
7.
8.
Properties:
High flow
Record the fine details.
Slight contraction during setting.[0.1%]
Rigid
Use in minimum undercut. [completely edentulous patient]
Self adhesive to the tray.
Non-elastic
Can’t record the undercut. Distortion on removal.
Can be disinfected.
Dimensional stable during storage.
Compatibility with model materials:
a.
The gypsum mix can adapt & fill the impression.
b.
No separating medium is required.
c.
Immerse the assembly in warm water-bath for easy separation.
d.
Can not be electroplated.
18
20. Elastic Impression Materials
Definition:
Elastic impression materials are able to record the undercut area in
the dental arch on removal from the patient’s mouth.
They are able after setting to compress at the undercut area
facilitating their removal from the patient’s mouth.
This is known as flexibility.
Then they return back to the original recorded dimensions. This is
known as elasticity.
But these materials are not purely elastic, they are viscoelastic.
20
21. Elastic Impression Materials
What is viscoelasticity?
Viscoelasticity is a strain time relationship.
It is a combination of :
Elastic
• On stress application :Immediate strain , which
remains constant during stress application.
• On stress removal: Immediate recovery.
Anelastic
• On stress application: Gradual increasing strain
during stress application..
• On stress removal: Gradual recovery till reaching
zero.
Viscous
• On stress application: Gradual increasing strain
during stress application.
• On stress removal: No recovery
Permanent strain.
21
23. Elastic Impression Materials
1.
2.
What is the influence of viscoelasticity on the impression
material?
Don’t exert pressure on the tray after insertion.
Don’t move the tray.
Rapid snap removal of the impression in a direction as nearly // as
possible to the long axes of the teeth.
- Permanent deformation.
Tear strength.
Time is required to allow for the gradual recovery of the anelastic
recovery.
Types:
Hydrocolloids.[Aqueous elastic impression materials]
Rubbers [Elastomers][ Non aqueous elastic impression materials]
23
26. Hydrocolloids [Aqueous Elastic
Impression Materials]
States of hydrocolloids:
Sol [Viscous liquid]
Gelation
Gel [Jelly like material]
Types of hydrocolloids:
Reduction in temperature
reaction
Agar
[Reversible hydrocolloid]
Chemical
Alginate
[Irreversible hydrocolloid]
Both are introduced in the sol form intra-orally.
They are removed in the gel form from the patient’s mouth.
26
27. Hydrocolloids[Aqueous Elastic Impression
Materials]
Structure of hydrocolloid gel:
Gelation occurs by the agglomeration of the dispersed phase
[Solute] to form fibrils in a network pattern enclosing water
in-between.[Brush heap structure]
This is
accompanied by
slight
shrinkage.
Filler
Fibrils
H2O
27
28. Hydrocolloids [Aqueous Elastic Impression
Materials]
1.
2.
3.
Factors affecting gel strength:
Concentration of fibrils.
Concentration of fillers.
Temperature.
N.B. Hydrocolloids are of poor tear strength.
.·. - Use in thick section.[4-6mm]
- Rapid snap removal.
28
29. Hydrocolloids [Aqueous Elastic Impression
Materials]
Dimensional stability:
Being hydrocolloid
Dry condition
Wet condition
Loss of water
SYNERSIS
Gain of water
IMBIBITION
Shrinkage
Expansion
Poor dimensional stability
29
30. Agar[Reversible]
Supplied form:[Gel]
1. Sealed container.
2. Metallic collapsible tubes. [ High viscosity
Flow]
3. Syringe material.[ Low viscosity
Flow]
It is packaged -In plastic or glass cartridges that fit a
syringe.
- Preloaded syringe.
30
31. Agar[Reversible]
Composition:
The gel is composed of:
Agar
12%
Dispersed phase.[Natural polymer]
Water 8o%
Dispersion medium.
Viscosity.
Borax
Filler to control
Strength
but acts as retarder for the setting
of gypsum model.
Potassium sulfate Accelerator for the setting of
gypsum model.
31
32. Agar[Reversible]
Gelation reaction:
It is a physical reaction.[Reversible]
Sol
70 - 100ºC
Gel.
37 -45ºC
Hysteresis:
It is the temperature lag between the liquefaction & gelation
temperature, otherwise
- Gelation will be rapid.
- There will be thermal injury to the
patient’s tissues.
32
33. Agar[Reversible]
Manipulation:
Agar needs special armamentarium.
1.Heating & Conditioning Bath:
1st Compartment:[Boiling] Gel
Sol.
2nd Compartment:[Storage] Store in the sol state.
3rd Compartment:[Tempering] to avoid thermal
injury of the patient.
33
34. Agar[Reversible]
2.
Manipulation:
Use of water cooling system tray with means of retention. [Looped
wire]
Avoid –
3.
◦
◦
Exerting pressure on the tray after insertion.
◦
Iced water
Moving the tray during gelation.
Application as
Concentration of stresses.
-Full & quadrant impression for partially or
completely edentulous patients.
- Duplication material.
34
35. Alginate[Irreversible]
Supplied form:
Powder in
-Bulk container.
-Preweighed package for individual impression.
N.B. Preweighed package is preferable than large container,
because alginate is very sensitive to storage temperature &
moisture contamination.[Poor shelf life]
Precautions during storage:
1.
Stock only for 1 year.
2.
Store in cool dry place.
35
36. Alginate[Irreversible]
Composition
:
Action:
Sodium or Potassium alginate
12%
Calcium sulfate dihydrate 12%
Soluble salt.[Natural polymer]
Trisodium phosphate 2%
Filler
Fluoride
Glycol
Chemical indicators
To release Ca++ to react with
alginate. [Reactor]
Retarder .
Viscosity
To control
Strength
Accelerator for the setting
of gypsum model.
Decrease dust formation.
To indicate the pH changes during
manipulation.
36
37. Alginate[Irreversible]
Gelation reaction:
It occurs by chemical reaction.[Irreversible]
It occurs in 2 steps:
- Retardation reaction:[To prolong the working time]
Trisodium phosphate + Calcium sulphate dihydrate +H2O
Calcium phosphate + Sodium sulphate.
- Gelation reaction:
Potassium alginate + Calcium sulphate dihydrate
+H2O
Calcium alginate [gel]
+ Potassium sulphate
37
38. Alginate[Irreversible]
The gel structure:
The final structure sodium alginate
cross-linked with calcium ions.
Types:
According to the amount of
Trisodium phosphate [Retarder]
-Regular set
-Fast set
Cross-linking of Sodium alginate
39. Alginate[Irreversible]
1.
2.
3.
4.
Manipulation:
Armamentarium:
-Rubber bowl & stiff wide bladed Stainless Steel spatula.
- Perforated stock tray for retention.
Steps:
Proportioning for powder & water.
Vigorous mixing against the sides of the rubber bowl [Sol]
Mixing time: 1 minute [Regular set] 45 seconds [Fast set]
Gelation time: 1.5-5 minutes from the start of the mix till the
material looses tackiness.[Sol
Gel]
Avoid -Iced water for mixing.
-Exerting pressure on the tray after mixing.
-Moving the tray during gelation.
39
42. Agar & Alginate
Properties:
High flow, since the dispersion medium is water.
.·. Excellent in recording fine details.
Slight shrinkage during gelation due to agglomeration of the dispersed
phase.
Flexible.
Agar< Alginate[most flexible elastic impression material]
Not adhesive to the tray.
Need for mechanical retention.
e.g. Perforations.
Viscoelastic.
Record the undercut.
.·. No torque or twist during removal of the impression.
Rapid snap removal
Permanent deformation [Agar<Alginate]
Allow for gradual recovery before pouring the model.
42
43. Agar & Alginate
Properties:
Low tear strength.
.·. –Use thick section. [4-6mm]
- Rapid snap removal.
Can be disinfected only by spraying .
During storage they are subjected to synersis & imbibition.
.·.- Pour the model as soon as possible.
- Keep the impression in a humidor .[100%relative humidity]
- Wrap the impression in wet paper towel.
43
44. Agar & Alginate
1.
2.
3.
4.
Properties:
Compatibility with model materials:
Being hydrophilic , the gypsum model can be poured without air
pockets.
No need for separating medium.
.·. Easy separation if the impression is not left overnight.
Retarding effect on the model surface
Chalky soft
surface.
Therefore an accelerator for the setting of the gypsum model
is included in the material.
Can not be electroplated.
44