Alginate Impression (Lec 2)

7/28/2019 Alginate Impression (Lec 2)

1/18

1

*Alginate impression

-Today we will talk about impression materials, as you know and as a

review of your dental material, we have different types of impression

materials..we will talk specifically about alginate impression materials

-When we classify impression materials, we do not classify them basedon its consistency when they are going to the mouth (before they set) ,but

we classify them on how they set when it is inside the mouth

-the impression material that is most used in dentistry by far without

controversy is alginate


2/18

2

-Alginate falls in the ELASTIC ACQUOES HYDROCOLLOID type of

impression material.Most widely used impression material

*Indications

study modelsRemovable partial dentures

*Examples of commercially available alginate:Hydrogum (Zhermack)

Jeltrate (Dentsply/Caulk)

Coe Alginate (GC America)


3/18

3

-Alginate is not very strong material; it tears relatively easy, and also it isflexible material, which mean when it goes to an undercut it should have

sufficient thickness so it can able to be compressed and to be pulled out,

if it is too thin, it is going to tear.

-alginate is mucustatic impression material, it is flexible, requireminimum space of 3 mm, it range from 3-6 mmthat is mean when I

place the tray in the patient mouth, the rim of the tray should be free inthe patient mouth there should be 3-6 mm between the buccal surfaces of

the teeth on the right and the left side and the tray

-The thing that we definitely not supposed to use alginate is the final

impression for fixed prosthesis and implant prosthesis ,you will find

that some private clinic do use it but it is not accurate enough for crown

and bridge procedure and fixed implant procedure, it is not accurate

enough and not strong enough-Silicones are mainly the final impression material of choice for most

fixed procedure.>> Why difficult to disinfect? You can't leave it in water and you can'tleave it more than 5-10 min otherwise it will distort.


4/18

4

* Selection of a Stock Tray

-What type of trays should we use

with alginate?

-We definitely need mechanicalretention, it is elastomeric

impression material, and the most

common type of mechanical

retention is perforated trays

-We can use adhesive for alginate

impression, a special adhesive foralginate.each type of

impression material has its own

adhesive, we should not mix

between, this is very important,

we spray it in thin layer, and it

should become fully dried when it become dried, it become sticky and

tacky , now we are ready to place our impression material


5/18

5

- There are two tray types you can use when taking alginate

compounds:

1- Disposable plastic trays: Must be coatedwith adhesives to prevent its separation from

alginate especially when it contains no or fewperforations.

2-Metal trays:

- Metal trays have a rim locked edges. rim

lock trays (they have metal ledge around the rimto hold alginate in place)

- can be sterilized.

- No need for adhesives to be used (adhesives

cannot be cleaned).

- When estimating the size of the tray that:

You'll use a barrier must be used on the deposable trays to insure that it

will not be contaminated.

Metal trays can be sterilized so they do not need a barrier.

Make sure that the space between the tissue and the tray is 3-6 mm.

- Impression trays come in small, medium and large sizes

- If the tray needs to be extended distally you can use beading wax to

build it up.- How to check the fitness of the mandibular tray??(These directions are for right handed clinicians left handed clinicians

must reverse these directions):

Stand at 8 o'clock position.

Hold the handle of the tray with your right hand and turn it over. Retract the right check with the index finger of your left hand.


6/18

6

Hold the tray sideways and insert it using the side of the tray to retract

the left cheek.

Rotate the tray in the mouth until it is centered.

Left the front of the tray up and visually inspect that the alveolar ridges

clear the tray .ask the patient if the tray feels comfortable.

- How to check the fitness of the maxillary tray??(These directions are for right handed clinicians left handed clinicians

must reverse these directions):

Stand at 8 o'clock position. The insertion of the tray is the same as for the mandibular one.

When the maxillary tray is in the mouth lower the front of the tray to

make sure it clears the alveolar ridge.

Ask the patient if it feels comfortable.

- After finishing checking the trays ask the patient to rinse with full

strength antimicrobial wash for 30 seconds.


7/18

7

* PREPARING ALGINATES

- Remember always to wear a mask to filter all the dust particles whenusing alginate powder since it is not healthy to breathe any dust particles

-studies have found evidence ofpulmonary hypersensitivity to seaweed

dust, and evidence of precipitating antibody to sodium alginate and

seaweed extracts in the serum of people dealing with alginate dust.

Alginate powder come in two sets:

- Regular set: creamy in color, jells (harden) in 3-4 mins

- Fast set: pinkin color, jells (harden) in 1-2 mins

Shake the container well before using the material to remix the heavier

components with the lighter ones (homogenizing the material) resultingin a proper amount of the material in each scoop.

*Preparations:

Measuring by weight is more accurate than by volume, but it is not

practical in clinic Therefore, we used measurement by volume in the

clinic

Ratio is.1 scoop powder: 1 measure water

* For the maxilla: it needs 3 scoops of powder with 3 measures of water

* For the mandible: it needs 2 scoops of powder with 2 measures of water


8/18

8

Water measures are taken in room temperature since:

- Warm water will accelerate the set of alginate

- Cold water will retard it

Temple the closed alginate container as mentioned before

Fill a scoop and tap it firmly until the powder is condensed

Add water to one of the bowels (which you like to take the impression

with it first)

Put the maxillary 3 scoops in one bowel and the 2 scoops forthe

mandible in another one

Gently start mixing powder with water until the powder is completely

wet


9/18

9

Now the mixing action becomes more aggressive. Use the blade of the

spatula to push alginate against the side of the bowelthis is called

stropping.

Mixture can be held in one place and stropped side to side or it can be

moved around inside the bowel and the bowel is rotated with the otherhand

Aggressive spatulating continues until smooth creamy mixture is

obtained, which takes about 30 seconds (fast set alginate requires 45

second of mixing for a creamy consistency)

The mixture should not contain grains


10/18

10

Gather alginate on the spatula and press into the maxillary tray from

posterior, while mandibular tray must be loaded from both sides allowing

the alginate to meat at the middle

Try to avoid air bubbles while loading

Smooth the alginate with your wet figure creating an indentation with

your figure to help orient the tray when seating it into the pt's mouth.

Now you are ready to take an impression

- The right handed clinicians stand in


11/18

11

* Taking impression

-The ideal setting position for the patients is always upright, you cant

take the impression while they are supine or semi-supine or lying down.There is a great danger of choking.

-Now concerning where you set as a doctor it depends on the wither you

take the impression for the maxilla or mandible

*For Maxilla:

-You stand behind the patient and to the

right (Between 9-12oclock)

*step by step:

- The right handed clinician stands at 11

o'clock or 12 o'clock position.

- The chair must be lowered slightly to have a

better view over the patient's head.

- Remind the patient to breath from his nose

during the impression taking.

- Retract patient's left cheek with your left index finger.

- Hold the sideways using the edges of the tray to retract the patient's

right cheek.- Insert the tray and rotate it to center it into the mouth.- Align the handle with the midline of the center anterior teeth.

- Seat the posterior of the tray first and left the handle to seat the anterior

part.

-hold the patient's head upright with your left arm behind .this prevent thepatients from tipping their head back and helps with the gagging.

- Hold the seated tray until the alginate feels rubbery.


12/18

12

- To remove the impression stand at the position of 8 o'clock in front of

the patient and rape the seal in one of the two ways:

1-Tell the patient to close his lips and blow to puff their cheeks

2-If this doesn't replace the seal bring your right index finger along the

left edge of the tray and break the seal manually.

- Snap the tray out quickly to minimize distortion

- Use your left hand finger to create a "pushing" over the opposing teethso the tray won't snap against the mandibular teeth.

- Remove the tray by rotating its sideways.

- Instruct the patient to rinse out excess alginate

*For Mandible:

-You can stand in either in front of the patient Or beside the

patient.(Between 6-9oclock)

*step by step:

- The right handed clinicians stand in the 8 o'clock position, left handed

must reverse directions

- Raise the chair so you won't have to bend.

- Set the patient upright.


13/18

13

- Hold the tray handle with your right hand then turn it over.

- Retract the right cheek and hold the tray sideways and insert it while

rotating it into the mouth until it is centered.

- Seat the tray gently over the teeth and soft tissues from posterior toanterior.- Immediately muscle trim from the impression by bringing the patient's

lower lip up over the edge.

- Instruct the patient to left up their tongues upward and forward and

relax it.

- Hold the tray into the patient's mouth until the alginate feels rubbery anddoes not stick to your fingers

- The setting time of the alginate using room temperature water is 2 mins

and 30 seconds from the start of the mixing.

- Once the material has set, break the seal with one figure in the left

vestibule in the patient's oral cavity.

- Snap tray quickly to minimize distortion.

- Remove the tray by rotating it out of the oral cavity.

- Ask the patient to rinse out excess alginate

*After removing both trays

from the patient's mouth, give

him a towel and a mirror towipe out excess alginate from

the skin

- Rinse the impression under

running water and spray it with

disinfectant (it is important not

to soak the impression in

disinfectant liquid due to the

likelihood of imbibitions).

- After10 mins of contacting

with the disinfectant rinse the impression before pouring it with stone, it

is recommended to pour the impression as soon as possible as distortion

increases due to delay pouring and evaporation.

- Wrap it in a paper towel that has been wetted and let set in a bag to

maintain 100% humidity.


14/18

14

*Handling the Material:

1. Pre-measure materialdo not take containers to your operatory. Do

not handle containers with contaminated gloves/hands. This makes

infection control easier.

2. Do not leave containers open in a humid environment - humidity and

high temperatures can cause deterioration of the powder.

3. Do not mix in a bowl contaminated with dental stone gypsum can

cause acceleration of the alginate. Conversely alginate contamination of abowl used to mix stone can diminish the strength of the cast or model

produced.Keep separate bowls and spatulas for alginate and stone.

*Problem solving

-example: You are treating a patient and preparing him for a partialdenture prosthesisHe told you he has a bad gag reflex which had

stopped him from finishing the treatment with another doctor. What areyou going to do differently to take a successful impression?


15/18

15


16/18

16


17/18

17

* What is the difference between the following terms??

-Imbibition: distortion by water absorption

-Syneresis: loss of water and shrinkage distortion.

-Detergent: is a surfactant or a mixture of surfactants with "cleaning

properties in dilute solutions, removes dirt, especially from the surface of

things

-Disinfectant: are substances that are applied to non-living objects to

destroy microorganisms that are living on the objects.

-Disinfection does not necessarily kill all microorganisms, especially

resistant bacterial spores; it is less effective than sterilization, which is an

extreme physical and/or chemical process that kills all types of life.

-Disinfectants are different from other antimicrobial agents such as

antibiotics, which destroy microorganisms within the body, and

antiseptics, which destroy microorganisms on living tissue.

-Sterilization: is a term referring to any process that eliminates(removes) or kills all forms of microbial life, including transmissible

agents (such as fungi, bacteria, viruses, spore forms, etc.) present on a

surface, contained in a fluid, in medication, or in a compound such asbiological culture media.


18/18

18

-Sterilization can be achieved by applying heat, chemicals, irradiation, or

high pressure.

-Asepsis: is the state of being free from disease-causing contaminants

(such as bacteria, viruses, fungi, and parasites) or, preventing contact withmicroorganisms.

-The term asepsis often refers to those practices used to promote or

induce asepsis in an operative field in surgery or medicine to prevent

infection.

-Ideally, a surgical field is "sterile," meaning it is free of all biological

contaminants, not just those that can cause disease, putrefaction , orfermentation , but that is a situation that is difficult to attain,especially given the patient is often a source of infectious agents.

Therefore, there is no current method to safely eliminate all of the

patients' contaminants without causing significant tissue damage.

However, elimination of infection is the goal of asepsis, not sterility.

-Mixing time: the time to achieve a predefined level of homogeneity of a

flow tracer in a mixing vessel

-Setting time: The length of time that a resin or adhesive must be

subjected to heat or pressure or chemical reaction to cause them to set,that is, harden, gel, or cure.

-Border molding: the shaping of an impression material by the

manipulation or action of the tissues to determine the denture borderposition.

-Border extension of tray: extend borders of the tray if needed.

Extension should be made only to provide coverage of critical anatomy,

not for the purpose of displacing or distorting the vestibular tissues,which should be registered accurately to obtain a peripheral seal on a

denture.

*Extremely important note: this script involved what is written in your

batch script done by your collogue "Rmz Rabadi " also the alginate video

and the questions related to it..also what I saw it important from

previous year lecture in addition to extra-important notes and photos

related to alginate in general I hope it will be enough to pass the

exam.

Documents

Alginate Impression (Lec 2)