Alginate ( Hydrocolloid Impression Material)

Question 1

Ideal properties of alginate

Answer 1

• Acceptable taste
• quick setting time
• easy to remove from skin / cloth
• no impression of tonsils
• can breathe.

Question 2

Composition / constituents of alginate

Answer 2

Potassium alginate + calcium sulphate + water = calcium alginate potassium sulphate and water

• potassium alginate , forms alginate gel
• calcium sulphate , form alginate gel
• sodium phosphate, delay reaction of calcium so extend working time
• Potasium sulphate -
• ammonium salt and chlorhexidine, disinfectant
• Glycols, dustless
• Fillers - control viscosity prior to setting

Question 3

Properties of alginate

Answer 3

• fluid to record fine details
• Elasticity protect from undercuts
  -Adhesion can be problem
• compatible with plaster and dental stone
• setting time affected by water temperate.

Question 4

Manipulation of alginate

Answer 4

• tumble powder
• used manufacture measures
• water at 21 degree
• use adhesive or perforated tray
• vigourous mixing / push against side of bowl

Question 5

Time for alginate

Answer 5

Mixing time- 30-45 seconds
Working time - 1 min 30 seconds
Setting time - 2 minute 15 seconds
From start of mix - 45 second interval

Question 6

Alginate tray

Answer 6

• should be disposable
• holders are rigid
• can be sterilised
• check edge for roughness
• correct size

Question 7

Impression taking .

Answer 7

• apply fix on tray
• measure powder and liquid correctly
• mix thoroughly
• load tray, no excess
  -stand behind patient for upper
• stand front for lower
• muscle trim the peripheries
• keep tray still until set .
• your position and patient position should not too high or low
• rotate loaded tray to insert
• lift lip to allow material to flow into sulcus
• seat posteriorly first and then anteriorly
• muscle trim
• wait for set
• break seal in sulcus with finger and remove impression carefully by rotating it out of mouth
• clean patient face and offer rinse to remove excess.

Question 8

How to assess impression?

Answer 8

• Wash , dry and use good light to check
• check for air blow, drags, adhesion to tray, sulcus, good definition around teeth.

Question 9

Good impression

Answer 9

• free of bubbles
• good details of all teeth
• extend till second molar
• have good external roll
• smooth surface
• symmetrical in tray
• 1/4 thickness around entire impression
• no impression of tongue and lips

Question 10

If patient gag how to handle ?

Answer 10

• stay calm
• lean slightly forward
• take deep breathes down to your tummy
• wiggle leg
• think about something they like to do
• reassure patient
• constant talk calmly

Question 11

Complications with alginate

Answer 11

Anatomical- access , gag reflux, trismus, abnormalities
Local - irritation , allergy , eye contact , inhalation, ingestion
Psychological- anxiety , phobia

Question 12

Spotter

Answer 12

Rate you impression . Good , ok , not fit
What went wrong.
How can it prevent