SAFE ANTIBIOTICS
Clindamycin: No dose change
Azithromycin: No dose change
Doxycycline: No dose change
Metronidazole: Normal dose for Mild/Mod. disease
Vancomycin Pulvules
ANTIBIOTICS WITH ALERTS
Pen VK: Prolong interval
Amoxicillin: Prolong interval
Augmentin: Decrease dose
Ampicillin: Decrease dose
Dicloxacillin: Decrease dose
Keflex: Prolong interval
Duricef: Prolong interval
Clarithromycin: Avoid
Metronidazole: Prolong interval for severe disease
IV Vancomycin: Avoid
1)Pen VK: INTERVAL PROLONGED; DOSE UNCHANGED
a)Serum Creatinine < 2.0 mg/dL or the CrCl is > 50 mL/minute:
Pen VK is dosed normally at 250-500 mg PO q6h
b)S. Creatinine 2.0 mg/dL to Predialysis or CrCl 10-50 mL/minute:
Pen VK is dosed at 250-500 mg q8-12h
c)Patient on Dialysis:
Pen VK is dosed at 250-500 q12-16h
2)Amoxicillin: DOSE UNCHANGED; INTERVAL PROLONGED
a)Serum Creatinine below 3.3 mg/dL or Cr Cl >30 ml/minute:
Dispense the normal dose of Amoxicillin: 250-500 mg PO q8h
b)Serum Creatinine above 3.3 mg/dL to Predialysis or Cr Cl 10-30 ml/minute:
Prolong the interval and dispense: 250-500 mg PO q12h
Avoid using the 875 mg tablet
c)Cr Cl <10 ml/minute or the Dialysis Patient:
Prolong the interval and dispense: 250-500 mg PO q24h
The dose must be administered after dialysis completion
3)Augmentin:
Decrease the total dosage by 50% in the renal compromised patient
4)Azithromycin:
Use full dose of Azithromycin in the Renal compromised patient
Kidney disease: No dose change is needed with Kidney disease or Renal failure
Used with 50% total dose reduction in patient with both Kidney & Liver disease
5)Metronidazole (Flagyl):
Dose adjustment is required only in the presence of renal failure/dialysis
Metronidazole should be dosed at 500 mg PO q12h instead of q8h after the dialysis
6)Tetracycline HCL:
a. Serum Creatinine between 1.25-2.0 mg/dL or CrCl 50-80 mL/minute:
Dose Tetracycline HCL q8-12h
b. Serum Creatinine between 2.0 mg/dL to Pre-dialysis or CrCl 10-50 mL/minute:
Dose Tetracycline HCL q12-24h
c. In the presence of Dialysis or CrCl <10 mL/minute:
Dose Tetracycline HCL q24h
7)Doxycycline:
No dose change needed with kidney/live/kidney & liver disease
Read more...
" The Professional Man has no right to be other than a continuous student "
Quote of the day
Wednesday, September 8, 2010
Monday, September 6, 2010
Allergies in Dentistry
Sulpha Allergy: "Sulfa allergy" is a term used to describe adverse drug reactions to sulfonamides, a group of drugs that includes those with and without antibiotic characteristics.
b) Sulphite/bisulphite Allergy: All dental local anesthetics that contain epinephrine contain metabisulfite which is an antioxidant to prevent breakdown of epi.
Sulfites are added to injectable epinephrine (such as in the Epi-Pen) to prevent browning, which decreases the effectiveness of the drug. However, epinephrine has not been reported to cause adverse reactions in people with sulfite allergy, and should not be withheld in an allergic emergency. Injectable epinephrine may prove life saving in people with sulfite allergy experiencing anaphylaxis.
Read more...
b) Sulphite/bisulphite Allergy: All dental local anesthetics that contain epinephrine contain metabisulfite which is an antioxidant to prevent breakdown of epi.
Sulfites are added to injectable epinephrine (such as in the Epi-Pen) to prevent browning, which decreases the effectiveness of the drug. However, epinephrine has not been reported to cause adverse reactions in people with sulfite allergy, and should not be withheld in an allergic emergency. Injectable epinephrine may prove life saving in people with sulfite allergy experiencing anaphylaxis.
Patients who are allergic to sulpha are not allergic to bisulphites and vice-versa. It is safe to give epi containing local anesthetics with sulpha allergy
c)Penicillin : Allergic to Penicillin means allergy to all members of penicillin family. If its a simple rash type of reaction then we can use cephalosporins but in case of severe anaphylaxis type reaction even cephalosporins are contraindicated. Even for rash type reactions it is advisable not to give cephalosporins because of other choice available at disposal.
d)Codeine : A patient allergic to codeine is usually allergic to morphine due to cross reactivity. Before giving out prescription make sure you not only ask "Are you allergic to codeine/morphine but ask have you taken codeine/morphine before" ?
e)Local Anesthetics: Allery to amide anesthetics is very rare. Allergy to one amide does not contraindicate the use of other amides. There is definite cross reactivity with ester anesthetics ie allergy to one ester anesthetic means allergy to all ester anesthetics
f) Latex Allergy: Children with spina bifida are at extraordinary high risk of latex hypersensitivity.
Screening: Have you experienced hives, wheezing, rashes, coughing, or difficulty in breathing when handling items like balloons and rubber balls?”
“Have you experienced any of these symptoms after contact with medical or dental products like rubber gloves or dental dams?”
“Have you ever worked in a health care setting? In the rubber industry?”
Dental Management: There are two main sources of latex exposure to our patients. The primary source is latex gloves. The practitioner must wear nonlatex gloves for the latex-sensitive patient. The second source is aerosolized latex. Latex proteins adhere to the cornstarch powder added by manufacturers to assist in donning and removal. It is a common misconception that it is the powder to which a person is allergic; rather, it is the protein sticking to the powder.
Each time powdered gloves are used, latex is introduced into the air, where it can remain up to 12 hours.(14) This “latex dust” acts as a sensitizing aeroallergen, and in sensitive people has caused serious, asthmatic life-threatening reactions. Therefore, merely wearing nonlatex gloves while treating an allergic patient may be an inadequate precaution when powdered latex gloves are being used elsewhere in the office.
If there is any question of safety, it is often advisable to have an allergic patient come to your office and simply sit in your waiting room. If there is any risk, it may be prudent to refer the patient to a latex-safe office.
For the latex-allergic patient, the following are recommended:
the patient should be the first patient of the day (low “latex dust”);
no direct contact with latex is allowed;
nonlatex substitutes for patient care must be used: prophy cups, dental dam, N20 mask, etc.;
latex in the room must be ALARA (As Low As Reasonably Achievable);
any latex items that cannot be removed must be covered;
the room should be close to the entrance (in case of emergency);
personnel setting up the room must wear nonlatex gloves;
instruments must be handled only with nonlatex gloves;
lab work must be handled with nonlatex gloves and thoroughly rinsed before placement;
multi-dose glass vials of anesthetic or glass ampules should be used;
if the patient is taking beta blockers, a medical consult must be done (these drugs interfere with the medications needed to resuscitate a patient should an emergency arise);
use nonlatex blood pressure cuffs;
wear minimal perfume and aftershave;
gutta percha has a potential for cross-allergencity (an alternative is Ketac-Endo fill).
Original Author for latex topic By Lawrence D. Duffield, DDS
Journal of the Michigan Dental Association
June 1998 href="http://www.latexallergylinks.org/MDA.html">http://www.latexallergylinks.org/MDA.html
c)Penicillin : Allergic to Penicillin means allergy to all members of penicillin family. If its a simple rash type of reaction then we can use cephalosporins but in case of severe anaphylaxis type reaction even cephalosporins are contraindicated. Even for rash type reactions it is advisable not to give cephalosporins because of other choice available at disposal.
d)Codeine : A patient allergic to codeine is usually allergic to morphine due to cross reactivity. Before giving out prescription make sure you not only ask "Are you allergic to codeine/morphine but ask have you taken codeine/morphine before" ?
e)Local Anesthetics: Allery to amide anesthetics is very rare. Allergy to one amide does not contraindicate the use of other amides. There is definite cross reactivity with ester anesthetics ie allergy to one ester anesthetic means allergy to all ester anesthetics
f) Latex Allergy: Children with spina bifida are at extraordinary high risk of latex hypersensitivity.
Screening: Have you experienced hives, wheezing, rashes, coughing, or difficulty in breathing when handling items like balloons and rubber balls?”
“Have you experienced any of these symptoms after contact with medical or dental products like rubber gloves or dental dams?”
“Have you ever worked in a health care setting? In the rubber industry?”
Dental Management: There are two main sources of latex exposure to our patients. The primary source is latex gloves. The practitioner must wear nonlatex gloves for the latex-sensitive patient. The second source is aerosolized latex. Latex proteins adhere to the cornstarch powder added by manufacturers to assist in donning and removal. It is a common misconception that it is the powder to which a person is allergic; rather, it is the protein sticking to the powder.
Each time powdered gloves are used, latex is introduced into the air, where it can remain up to 12 hours.(14) This “latex dust” acts as a sensitizing aeroallergen, and in sensitive people has caused serious, asthmatic life-threatening reactions. Therefore, merely wearing nonlatex gloves while treating an allergic patient may be an inadequate precaution when powdered latex gloves are being used elsewhere in the office.
If there is any question of safety, it is often advisable to have an allergic patient come to your office and simply sit in your waiting room. If there is any risk, it may be prudent to refer the patient to a latex-safe office.
For the latex-allergic patient, the following are recommended:
the patient should be the first patient of the day (low “latex dust”);
no direct contact with latex is allowed;
nonlatex substitutes for patient care must be used: prophy cups, dental dam, N20 mask, etc.;
latex in the room must be ALARA (As Low As Reasonably Achievable);
any latex items that cannot be removed must be covered;
the room should be close to the entrance (in case of emergency);
personnel setting up the room must wear nonlatex gloves;
instruments must be handled only with nonlatex gloves;
lab work must be handled with nonlatex gloves and thoroughly rinsed before placement;
multi-dose glass vials of anesthetic or glass ampules should be used;
if the patient is taking beta blockers, a medical consult must be done (these drugs interfere with the medications needed to resuscitate a patient should an emergency arise);
use nonlatex blood pressure cuffs;
wear minimal perfume and aftershave;
gutta percha has a potential for cross-allergencity (an alternative is Ketac-Endo fill).
Original Author for latex topic By Lawrence D. Duffield, DDS
Journal of the Michigan Dental Association
June 1998 href="http://www.latexallergylinks.org/MDA.html">http://www.latexallergylinks.org/MDA.html
Read more...
Sunday, July 26, 2009
Impression Materials
EDENTULOUS IMPRESSIONS
ZOE impression paste and impression plaster
ADV Examples of mucostatic impression materials, do not compress the tissue during seating of tray. Ideal material for taking impression of Edentulous structures.
Disadv Are inelastic, cannot be removed past undercuts without fracturing or distorting.
Solution Use very fluid, light body elastomeric impression materials
ELASTOMERIC IMPRESSION MATERIALS
a) Polysulfide, byproduct water. Custom trays recommended for impression making to reduce quantity of material and hence dimensional changes. Lowest viscosity and so one of the least stiff allowing it to be removed from undercut areas with minimum stress
b)Condensation silicone, byproduct ethyl alchohol
c)Additional silicone/ Polyvinyl Siloxanes. No reaction byproduct but reaction between moisture and residual hydride polymers can lead to production of hydrogen gas which can result in pinpoint voids in gypsum if casts are poured soon after removal from mouth. So wait an hour.
Sulphur in latex/vinyl gloves inhibit the setting of this material. Touching the tooth with gloved finger can inhibit the setting of impression material in critical area producing major distortion
d) Polyether
PUTTY refers to high viscosity materials which are highly filled so that less polymer is present and there is less polymerization shrinkage.
IMPRESSION MAKING
Longer the impression material remains in the mouth, less the distortion on removal
I) Multiple Mix technique
a)LIGHT body material- used with syringe and placed directly on hard and soft tissues
b)HEAVY body material- used in tray to support light body material
II) Monophase or Single Viscosity technique : MEDIUM Viscosity materials are used. Single mix is made and part of it is placed in syringe and part on tray. When the medium viscosity material is pushed through the syringe the viscosity decreases (pseudoplastic property). Material in tray retains its medium viscosity and when seated forces the syringed material past critical areas.
III) Putty Wash Technique:
a) Two step technique: Make a preliminary impression with thick putty material in a stock tray using thin polyethylene sheet as a spacer for light body material. This makes a custom tray in which light body material can be used to make a final wash impression. Some light body material can be placed directly onto the preparation.
b)Single step technique: Light body material is syringed in place and unset putty is seated in a tray and then in mouth. Disadv is that the higher viscosity material may displace the lighter material and the critical areas may be reproduced in putty rather than lighter material and the required detail may not be captured in the material.
Both these techniques have distortion as their problem. Inadequate space for light body or distortion of set putty can cause problems.
POURING THE CAST
a) Two or three dies can easily be constructed as these materials are dimensionally stable. Each successive die will be less accurate than the first.
b)The time interval between the impression pours should be less than 30 mins.
c)Polyvinysiloxane materials are hydrophobic which make it difficult to wet the surface by gypsum forming slurry. Use the surfactant spray to form a bubble free cast.
WORKING AND SETTING TIME
Store or Mix the material on cool slab to increase the working time and then the setting time is decreased in mouth at high temp. Working and setting time decrease as viscosity increases.
DIMENSIONAL STABILITY
Polysulfides and Condensation silicones lose reaction byproducts, water and alcohol respectively, so for maximum accuracy, pour these impressions within 30 mins.
Additional silicone and Polyether can be stored from 24 hours to 1 week.
DISINFECTION
Condensation silicones, Polysulfides and Additional silicones can be disinfected with any EPA disinfectant.
Polyethers are suseptible to dimensional changes if immersed for longer than 10 mins due to absorption of water and leaching of water soluble plasticizer.
Long immersion time with Polyvinylsiloxanes may cause the surfactant to leach out rendering the material less hydrophilic and hence difficult to pour.
Rinse and dry the impression after 10 mins of immersion in disinfectant.
EDENTULOUS IMPRESSIONS
ZOE impression paste and impression plaster
ADV Examples of mucostatic impression materials, do not compress the tissue during seating of tray. Ideal material for taking impression of Edentulous structures.
Disadv Are inelastic, cannot be removed past undercuts without fracturing or distorting.
Solution Use very fluid, light body elastomeric impression materials
ELASTOMERIC IMPRESSION MATERIALS
a) Polysulfide, byproduct water. Custom trays recommended for impression making to reduce quantity of material and hence dimensional changes. Lowest viscosity and so one of the least stiff allowing it to be removed from undercut areas with minimum stress
b)Condensation silicone, byproduct ethyl alchohol
c)Additional silicone/ Polyvinyl Siloxanes. No reaction byproduct but reaction between moisture and residual hydride polymers can lead to production of hydrogen gas which can result in pinpoint voids in gypsum if casts are poured soon after removal from mouth. So wait an hour.
Sulphur in latex/vinyl gloves inhibit the setting of this material. Touching the tooth with gloved finger can inhibit the setting of impression material in critical area producing major distortion
d) Polyether
PUTTY refers to high viscosity materials which are highly filled so that less polymer is present and there is less polymerization shrinkage.
IMPRESSION MAKING
Longer the impression material remains in the mouth, less the distortion on removal
I) Multiple Mix technique
a)LIGHT body material- used with syringe and placed directly on hard and soft tissues
b)HEAVY body material- used in tray to support light body material
II) Monophase or Single Viscosity technique : MEDIUM Viscosity materials are used. Single mix is made and part of it is placed in syringe and part on tray. When the medium viscosity material is pushed through the syringe the viscosity decreases (pseudoplastic property). Material in tray retains its medium viscosity and when seated forces the syringed material past critical areas.
III) Putty Wash Technique:
a) Two step technique: Make a preliminary impression with thick putty material in a stock tray using thin polyethylene sheet as a spacer for light body material. This makes a custom tray in which light body material can be used to make a final wash impression. Some light body material can be placed directly onto the preparation.
b)Single step technique: Light body material is syringed in place and unset putty is seated in a tray and then in mouth. Disadv is that the higher viscosity material may displace the lighter material and the critical areas may be reproduced in putty rather than lighter material and the required detail may not be captured in the material.
Both these techniques have distortion as their problem. Inadequate space for light body or distortion of set putty can cause problems.
POURING THE CAST
a) Two or three dies can easily be constructed as these materials are dimensionally stable. Each successive die will be less accurate than the first.
b)The time interval between the impression pours should be less than 30 mins.
c)Polyvinysiloxane materials are hydrophobic which make it difficult to wet the surface by gypsum forming slurry. Use the surfactant spray to form a bubble free cast.
WORKING AND SETTING TIME
Store or Mix the material on cool slab to increase the working time and then the setting time is decreased in mouth at high temp. Working and setting time decrease as viscosity increases.
DIMENSIONAL STABILITY
Polysulfides and Condensation silicones lose reaction byproducts, water and alcohol respectively, so for maximum accuracy, pour these impressions within 30 mins.
Additional silicone and Polyether can be stored from 24 hours to 1 week.
DISINFECTION
Condensation silicones, Polysulfides and Additional silicones can be disinfected with any EPA disinfectant.
Polyethers are suseptible to dimensional changes if immersed for longer than 10 mins due to absorption of water and leaching of water soluble plasticizer.
Long immersion time with Polyvinylsiloxanes may cause the surfactant to leach out rendering the material less hydrophilic and hence difficult to pour.
Rinse and dry the impression after 10 mins of immersion in disinfectant.
Polysulfide (Coe-Flex,Permlastic)
Advantages High tear resistant,Modest Cost
Disadvantages Long working time,Requires custom tray,Odor,Pour within 1 hour,Stains clothes
Vinyl Polysiloxane (Aquasil,Express/Imprint/Imprint II,Extrude,Polysil)
Advantages One material,Easily seen margins,Pour repeatedly,Stable delay pour
Disadvantages Hydrophobic,No flow If sulcus moist,Low tear strength,High cost,Difficult to pour cast
Polyether (Impergum,Permadyne)
Advantages Fast setting,Least hydrophobic,Easily seen margins,Good stability,Delay pour
Disadvantages Stiff, high modulus, Bitter taste, Needs to block undercuts,Absorbs water,Leaches components,High Cost.
Read more...
ZOE impression paste and impression plaster
ADV Examples of mucostatic impression materials, do not compress the tissue during seating of tray. Ideal material for taking impression of Edentulous structures.
Disadv Are inelastic, cannot be removed past undercuts without fracturing or distorting.
Solution Use very fluid, light body elastomeric impression materials
ELASTOMERIC IMPRESSION MATERIALS
a) Polysulfide, byproduct water. Custom trays recommended for impression making to reduce quantity of material and hence dimensional changes. Lowest viscosity and so one of the least stiff allowing it to be removed from undercut areas with minimum stress
b)Condensation silicone, byproduct ethyl alchohol
c)Additional silicone/ Polyvinyl Siloxanes. No reaction byproduct but reaction between moisture and residual hydride polymers can lead to production of hydrogen gas which can result in pinpoint voids in gypsum if casts are poured soon after removal from mouth. So wait an hour.
Sulphur in latex/vinyl gloves inhibit the setting of this material. Touching the tooth with gloved finger can inhibit the setting of impression material in critical area producing major distortion
d) Polyether
PUTTY refers to high viscosity materials which are highly filled so that less polymer is present and there is less polymerization shrinkage.
IMPRESSION MAKING
Longer the impression material remains in the mouth, less the distortion on removal
I) Multiple Mix technique
a)LIGHT body material- used with syringe and placed directly on hard and soft tissues
b)HEAVY body material- used in tray to support light body material
II) Monophase or Single Viscosity technique : MEDIUM Viscosity materials are used. Single mix is made and part of it is placed in syringe and part on tray. When the medium viscosity material is pushed through the syringe the viscosity decreases (pseudoplastic property). Material in tray retains its medium viscosity and when seated forces the syringed material past critical areas.
III) Putty Wash Technique:
a) Two step technique: Make a preliminary impression with thick putty material in a stock tray using thin polyethylene sheet as a spacer for light body material. This makes a custom tray in which light body material can be used to make a final wash impression. Some light body material can be placed directly onto the preparation.
b)Single step technique: Light body material is syringed in place and unset putty is seated in a tray and then in mouth. Disadv is that the higher viscosity material may displace the lighter material and the critical areas may be reproduced in putty rather than lighter material and the required detail may not be captured in the material.
Both these techniques have distortion as their problem. Inadequate space for light body or distortion of set putty can cause problems.
POURING THE CAST
a) Two or three dies can easily be constructed as these materials are dimensionally stable. Each successive die will be less accurate than the first.
b)The time interval between the impression pours should be less than 30 mins.
c)Polyvinysiloxane materials are hydrophobic which make it difficult to wet the surface by gypsum forming slurry. Use the surfactant spray to form a bubble free cast.
WORKING AND SETTING TIME
Store or Mix the material on cool slab to increase the working time and then the setting time is decreased in mouth at high temp. Working and setting time decrease as viscosity increases.
DIMENSIONAL STABILITY
Polysulfides and Condensation silicones lose reaction byproducts, water and alcohol respectively, so for maximum accuracy, pour these impressions within 30 mins.
Additional silicone and Polyether can be stored from 24 hours to 1 week.
DISINFECTION
Condensation silicones, Polysulfides and Additional silicones can be disinfected with any EPA disinfectant.
Polyethers are suseptible to dimensional changes if immersed for longer than 10 mins due to absorption of water and leaching of water soluble plasticizer.
Long immersion time with Polyvinylsiloxanes may cause the surfactant to leach out rendering the material less hydrophilic and hence difficult to pour.
Rinse and dry the impression after 10 mins of immersion in disinfectant.
EDENTULOUS IMPRESSIONS
ZOE impression paste and impression plaster
ADV Examples of mucostatic impression materials, do not compress the tissue during seating of tray. Ideal material for taking impression of Edentulous structures.
Disadv Are inelastic, cannot be removed past undercuts without fracturing or distorting.
Solution Use very fluid, light body elastomeric impression materials
ELASTOMERIC IMPRESSION MATERIALS
a) Polysulfide, byproduct water. Custom trays recommended for impression making to reduce quantity of material and hence dimensional changes. Lowest viscosity and so one of the least stiff allowing it to be removed from undercut areas with minimum stress
b)Condensation silicone, byproduct ethyl alchohol
c)Additional silicone/ Polyvinyl Siloxanes. No reaction byproduct but reaction between moisture and residual hydride polymers can lead to production of hydrogen gas which can result in pinpoint voids in gypsum if casts are poured soon after removal from mouth. So wait an hour.
Sulphur in latex/vinyl gloves inhibit the setting of this material. Touching the tooth with gloved finger can inhibit the setting of impression material in critical area producing major distortion
d) Polyether
PUTTY refers to high viscosity materials which are highly filled so that less polymer is present and there is less polymerization shrinkage.
IMPRESSION MAKING
Longer the impression material remains in the mouth, less the distortion on removal
I) Multiple Mix technique
a)LIGHT body material- used with syringe and placed directly on hard and soft tissues
b)HEAVY body material- used in tray to support light body material
II) Monophase or Single Viscosity technique : MEDIUM Viscosity materials are used. Single mix is made and part of it is placed in syringe and part on tray. When the medium viscosity material is pushed through the syringe the viscosity decreases (pseudoplastic property). Material in tray retains its medium viscosity and when seated forces the syringed material past critical areas.
III) Putty Wash Technique:
a) Two step technique: Make a preliminary impression with thick putty material in a stock tray using thin polyethylene sheet as a spacer for light body material. This makes a custom tray in which light body material can be used to make a final wash impression. Some light body material can be placed directly onto the preparation.
b)Single step technique: Light body material is syringed in place and unset putty is seated in a tray and then in mouth. Disadv is that the higher viscosity material may displace the lighter material and the critical areas may be reproduced in putty rather than lighter material and the required detail may not be captured in the material.
Both these techniques have distortion as their problem. Inadequate space for light body or distortion of set putty can cause problems.
POURING THE CAST
a) Two or three dies can easily be constructed as these materials are dimensionally stable. Each successive die will be less accurate than the first.
b)The time interval between the impression pours should be less than 30 mins.
c)Polyvinysiloxane materials are hydrophobic which make it difficult to wet the surface by gypsum forming slurry. Use the surfactant spray to form a bubble free cast.
WORKING AND SETTING TIME
Store or Mix the material on cool slab to increase the working time and then the setting time is decreased in mouth at high temp. Working and setting time decrease as viscosity increases.
DIMENSIONAL STABILITY
Polysulfides and Condensation silicones lose reaction byproducts, water and alcohol respectively, so for maximum accuracy, pour these impressions within 30 mins.
Additional silicone and Polyether can be stored from 24 hours to 1 week.
DISINFECTION
Condensation silicones, Polysulfides and Additional silicones can be disinfected with any EPA disinfectant.
Polyethers are suseptible to dimensional changes if immersed for longer than 10 mins due to absorption of water and leaching of water soluble plasticizer.
Long immersion time with Polyvinylsiloxanes may cause the surfactant to leach out rendering the material less hydrophilic and hence difficult to pour.
Rinse and dry the impression after 10 mins of immersion in disinfectant.
Polysulfide (Coe-Flex,Permlastic)
Advantages High tear resistant,Modest Cost
Disadvantages Long working time,Requires custom tray,Odor,Pour within 1 hour,Stains clothes
Vinyl Polysiloxane (Aquasil,Express/Imprint/Imprint II,Extrude,Polysil)
Advantages One material,Easily seen margins,Pour repeatedly,Stable delay pour
Disadvantages Hydrophobic,No flow If sulcus moist,Low tear strength,High cost,Difficult to pour cast
Polyether (Impergum,Permadyne)
Advantages Fast setting,Least hydrophobic,Easily seen margins,Good stability,Delay pour
Disadvantages Stiff, high modulus, Bitter taste, Needs to block undercuts,Absorbs water,Leaches components,High Cost.
Read more...
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The sole purpose of writing this blog is to be a continuous learner, to share information and to keep that information safe and easily accessible before it vanishes in pages of history.