#10 – Take alginate impressions

One of the indications a client will use to determine the quality of care we provide is this procedure. Is it done quickly, sloppy, with little regard for the client, or is it down in a “classy” manner that provides every convenience for the client?

If you are going to provide a first class service, it begins with the client Have they had impressions before? Do they know what to expect? Do they know why the impressions are being made? What can you do for them to make the procedure more comfortable?

Let’s look at those one at a time:

Why are we taking impressions?

The difference between first class and average is right here. Introduce yourself to your client. Review their chart with them to make sure they know why they are having the impressions. Discuss the treatment plan. Reinforce the treatment the client has selected. Tell them how successful it should be. Get to know them and what they want to accomplish.

Next, if this is the first time they have had impressions, tell them what to expect. “Mrs. Jones, these impressions will be an extremely accurate reproduction of your upper and lower jaws. Your doctor will use them to design the _____ for you. Here’s what you can expect today. I’ll take one model each of your upper and lower jaw. I mix the impression material together until it has the consistency of mashed potatoes and then I’ll fill a tray with it. I’ll put the tray in your mouth for not more than two minutes. The material will get to about the consistency of Jell-O and then I’ll take it out. Later I’ll pour plaster into this mold and when the plaster hardens, this will be a model of your jaw. Do you have any questions?”

Making your client comfortable

Impressions can be a scary, uncomfortable, a sloppy experience or, in the hands of a trained professional, no big deal. Some clients can handle this appointment easier than others, but the more confidence your client has in you, the easier the appointment will be.

1. Place vaseline in a wide area around their lips and cheeks. This will prevent the alginate from sticking to the face.

2. Dip the tray in our mouthwash to improve the taste of the metal.

3. Bib tight around the neck

4. Remember these materials go into the client’s mouth. Cover the counter with a paper towel. All trays, wax, spatulas, etc. to be on the towel.

5. Fluff up the alginate. Some particles are much heavier than others and will settle to the bottom. Shaking the can for 30 seconds will create a homogenous mix. There is lead in the alginate, so let the can sit for 1 minute or more before you remove the lid.

6. We use a fast set alginate. You will have a maximum of 2 1/2 minutes from the start of spatulation until the first set of the material. Regular set would give you twice as much time, but greatly increase the client’s discomfort and potential to gag.


1. Review with your client what you are going to do and why. “Have you had impressions before?” If not Fit trays, mix powder and water, will look like mashed potatoes, gets about as hard as Jell-O in 2 minutes, take out, pour plaster into, when hard, separate, have model of teeth. Pick the correct size tray. When you pick the trays, remember they will go in to the client’s mouth. Place a paper towel on the counter, all trays, wax, etc. should be placed on this paper.

2. With the top on the alginate can, fluff up the powder. Let the can set for a minute so the powder won’t blow around where you can breathe it (it contains lead). The powder look all alike, but there are many different elements. Shaking it up mixes these elements for a more accurate impression.

3. Examine the mouth for any problems. Does your client have existing appliances? Does your doctor want the impression taken with the appliances in or out of the mouth? If the impression is taken with the appliance in, is it to be poured with the appliance in or out of the impression? Any loose teeth or temporary crowns that could come out with the impression?

4. Fit the upper tray. It will usually be one size larger than the lower tray. If you can’t see the back tooth run your finger along the back of the tray and feel if the tooth is covered. The upper impression is “gaggier” than the lower, let your client know the tray is a “mouthful”, but avoid suggesting that the tray will make them gag. Ask if the tray pinches anywhere. When you have picked the upper tray, place a double row of blue wax over the posterior to prevent alginate flowing down your client’s throat. With the top on the alginate can, fluff up the powder. Let the can set for a minute so the powder won’t blow around where you can breath it (It contains lead). The powder looks all alike, but there are many different elements. Shaking it up mixes these elements for a more accurate impression

5. With your client seated upright and an emesis basin behind him/her (just in case), prepare for the lower impression.

6. Use 2 scoops for the lower impression with room temperature water. You will at first use water that is too cold. 70 degrees is room temperature. Use a thermometer to check the feel at first. It is warmer than you think. Warm water sets too fast and cold water will be uncomfortable to the client’s teeth. The 2 scoops are placed in a rubber bowl. Don’t pack the powder into the scoop. For a correct water/powder ratio, the powder should be loosely packed and the excess skimmed off the top with a spatula. Add water. Using a wide bladed spatula mix the alginate thoroughly by pushing it against the sides of the bowl and rotating the bowl. After no more than 45 seconds, the mix should have a smooth consistency.

7. Scoop up the alginate and load the lower tray. Where there are no teeth, fill it full. Where there are teeth, fill it about 1/2 full to prevent too much excess alginate in the client’s mouth. Wet your finger and smooth out the surface of the alginate. Gather the remaining alginate from the bowl and scrape it on the side of the bowl. Take some of this extra from the bowl and rub it on the occlusal surface of the lower teeth. This will prevent bubbles from forming when you seat the impression. Also, if you are trying to get an impression of the lateral throat form for missing molars, have your client raise their tongue 1/2 way toward the roof of their mouth and place one finger’s worth of alginate between the tongue and gums.

8. Standing in front of your client have your client raise the tongue 1/2 way up toward the roof of mouth, seat one side of tray in your client’s mouth. Rotate the tray into the mouth. Seat back first with a slight jiggling, rocking motion. Hold the lip out so air can escape as you seat the front part of the tray down.

9. Have your client hold the impression with both hands. Index fingers on the top of the tray and thumbs under the chin. When your client holds the impression, they can avoid putting too much pressure on area of the tray that is pushing too hard on gums. If you push you won’t be able to feel this pressure spot and you will hurt the client. If the client is uncomfortable, hold the tray for him.

10. When the impression first hardens, tell your client, “1 minute to go.” This helps them struggle through. Stay with the client until the impression hardens. If you are holding the tray check the hardness by putting some impression material on your finger. When it hardens, time one more minute. If your client is holding the tray, use this time to prepare for the upper impression. Test the material every 15 20 seconds in the mouth. When it has hardened (usually 1 1/2 2 minutes from start of spatulation) let it set one more minute. Keep an emisis basin handy just in case the client gags.

11. Remove the tray by standing behind the client and putting your thumbs on the top of the tray (this prevents the tray from banging the top teeth on removal) and your middle fingers on the bottom edges in the bicuspid areas. Try not to tear the alginate. Try to snap the alginate out. Don’t jerk the client’s head, but try to do a minimum of wedging back and forth to remove. The more you work it back and forth to remove it, the greater will be the distortion.

12. Hand your client a paper towel to help them clean up and make sure you have a good impression. Are the teeth all there? Do you have a good roll of tissue? Are the edentulous areas fully extended? If so, rinse off blood/saliva, spray with disinfectant, and wrap the impression in a wet paper towel and set it aside.

13. Next, take the upper impression. When you sized the tray, you got a good indication whether your client might gag. Now you’ll know! If this is a problem, see the last section on gagging.

14. Mix and load the tray. If it’s for partial dentures, check for a high palate this takes extra material and place it on the palate, then add some to the occlusal surfaces. If all you need is the teeth, don’t fill the center of the tray. Just fill a horseshoe shape around the outer one inch. Then point the occlusal surfaces of the teeth with alginate.

15. Standing behind your client, rotate the tray into your client’s mouth. Use your left hand to pull the left cheek out as you rotate the left side of the tray in. Seat the back of the tray first and, using your left hand to hold the lip out, seat the tray from back to front. This will greatly reduce the amount of material that goes down your client’s throat. When the tray is completely seated, mold the lip in against the tray to reduce excess.

16. To remove the upper tray, stand behind the client and put your thumbs on the rim of the tray in the bicuspid area and rotate down quickly to avoid distortion.

17. If the upper impression is good (good detail and full peripheries), wrap it in a wet paper towel and concentrate on the client.
a. Rinse
b. Floss/brush as needed until mouth clean
c. Give a mirror and wet and dry paper towels to remove Vaseline and alginate
d. Remove bib and escort to front desk
e. Quickly return and pour models

18. Wash blood and saliva off impression. Spray with a disinfectant. Rinse again and pour.

19. Pour the impression immediately. If you plan to make a second impression, wrap the first in a disinfectant soaked towel to prevent drying out distortion.

Consistency is runny/grainy
Toe little powder
Water too cold
Impression material tears when remove
Material too thin
Material not completely set
Incorrect removal
Impression not stored in humidor
Impression not poured immediately
Impression pulled away from the tray
Impression removed too soon
Tray allowed to move during setting
Stone model rough/chalky
Water pooled in tooth impressions before pouring
Stone mix too watery

20. Remove model from impression within a few hours to prevent erosion of the model by chemicals leaked from the impression.

In case of Gagging

1. Reassure your client that a gag reflex is normal. It protects foreign bodies from going down the trachea into the lungs. It is initiated by contact with the posterior 1/3 of the tongue or the soft palate.

2. There are 4 areas that produce the gag reflex
a. Base of tongue
b. Sides of throat
c. Soft palate
d. Uvula

3. There are a number of causes of gagging
a. General health problems:
1. Blocked nasal passages

2. Conditions causing an irritable stomach
a. Alcoholism
b. Ulcers

3. Heavy smokers

b. Psychological factors
1. To gain attention
2. To avoid treatment
3. Fears dentistry, anxiety, apprehension

c. Physiologic factors
1. Seeing an object that could cause a gag
2. Sound of someone else gagging
3. Some smells cause gagging (perfume, smoke)
4. Touch from an appliance, impression

d. factors caused by us
1. overloaded impression tray
2. overextended prosthesis
3. picking a slow set impression material
4. not seating client up

4. Simple minor gag techniques
a. You hold the tray
b. Have client breathe through nose keeps pharynx open
c. Keep eyes open
d. Deep breaths
e. Keep emissis basin nearby and out of client’s sight
f. Talk to client about something else they can concentrate on also tell them how much time is left every 15 20 seconds.

1. Be confident, concerned, sympathetic, reassuring
2. Many clients gag
3. Most can control it
4. Gagging is nothing to be embarrassed about

5. Medications
a. Nitrous oxide
b. Topical anesthesia on posterior of tongue and soft palate

6. Systematic desensitization for severe gaggers

a. Learn muscle relaxation
1. One daily session at least

b. Establish a grade list of increasing gag potential dental anxiety events for client to work on at home
1. Dentist touch a front tooth
2. Dentist looks under tongue
3. X ray of front tooth
4. X ray of back tooth
5. Impression of upper teeth

c. Home exercises
1. Lubricate finger with toothpaste and massage tongue, cheeks, palate for 2 minutes, 4 times each day
2. After 7 days use ultra soft toothbrush moistened with cold water. Continue for 6 weeks.

Takes & Pours models effectively

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