Lecture 1: Alginate Impressions

Question 1

What thickness is required of an accurate alginate impression?

Answer 1

thickness between 1/8 and 1/4 of an inch

Question 2

T/F: Adhesives CANNOT be used when making an impression.

Answer 2

FALSE! Adhesives can be used to prevent pullbacks which would otherwise require the impression to be redone.

Question 3

Why would prepackaged Alginate material be preferred?

Answer 3

reduced exposure to humidity, pre-calculated, longer shelf life.

Question 4

How would adding less water than recommended to the alginate powder affect the material?

Answer 4

makes for a less viscous material. REMEMBER! add water first and then powder

Question 5

What is the main advantage of vacuum mixing?

Answer 5

Less air captured in mixture–> less air bubbles–> more accurate and stable impression

Question 6

T/F: When taking an impression, you only want to put enough material in the tray to take a negative of all tooth structures.

Answer 6

FALSE! You want to overextend the impression to include the deep tissue (vestibule) as well.

Question 7

Where should the operator be positioned when taking a MANDIBULAR impression?

Answer 7

operator in front with fingers on top of tray

Question 8

Where should the operator be positioned when taking a MAXILLARY impression?

Answer 8

operator behind with fingers in middle of tray

Question 9

How should the tray be placed into the patient’s mouth when taking an impression?

Answer 9

Roll back to forward so the material doesn’t fall to back of throat of patient and so that the deep tissue of the anterior vestibule is captured as well.

Question 10

How much time should it take to MIX the alginate?

Answer 10

1 min

Question 11

How much time should it take to LOAD and SET the tray?

Answer 11

1.25 min

Question 12

How much time does it take for the material to POLYMERIZE?

Answer 12

2.25 min

Question 13

How much time does it take to DISINFECT the impression?

Answer 13

10.5 min

Question 14

How long should the entire process of making an impression with alginate take?

Answer 14

15 min in completion

Question 15

How do we disinfect the impression?

Answer 15

By spraying it with disinfectant. Why? because water flows in and out of the precipitate so you don’t want it to absorb too much water and alter the dimension.

Question 16

Which of the following is not an irregularity observed when taking an impression?
Pull backs
Show throughs
Over extension
Mucous secretion

Answer 16

Over extension is not an irregularity its actually preferred.
Pull backs are prevented by using adhesives
Mucous secretion is prevented by having the patient use a mouthwash or by dabbing.
Show throughs are prevented by properly placing the tray and making sure that there is material surrounding the oral structures without hindrance from the tray.

Question 17

T/F. An ideal impression achieves minimum extension but maximum detail.

Answer 17

FALSE! An ideal impression achieves BOTH maximum extension AND maximum detail.

Question 18

After disinfecting and sitting 10 min wrapped in a moist paper towel, what’s the next step?

Answer 18

MAKING THE CAST!

Question 19

What happens if you separate the cast from the impression too early?

Answer 19

you fuck it up. so sit cho ass down n be patient.