Alginate ( Hydrocolloid Impression Material) Flashcards
Ideal properties of alginate
- Acceptable taste
- quick setting time
- easy to remove from skin / cloth
- no impression of tonsils
- can breathe.
Composition / constituents of alginate
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
Properties of alginate
- 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.
Manipulation of alginate
- tumble powder
- used manufacture measures
- water at 21 degree
- use adhesive or perforated tray
- vigourous mixing / push against side of bowl
Time for alginate
Mixing time- 30-45 seconds
Working time - 1 min 30 seconds
Setting time - 2 minute 15 seconds
From start of mix - 45 second interval
Alginate tray
- should be disposable
- holders are rigid
- can be sterilised
- check edge for roughness
- correct size
Impression taking .
- apply fix on tray
- measure powder and liquid correctly
- mix thoroughly
- load tray, no excess
-stand behind patient for upper and midline should be in middle - 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.
- wash dry and inspect impression under light .
- No undercut , blow, bubble , less define impression.
How to assess impression?
- Wash , dry and use good light to check
- check for air blow, drags, adhesion to tray, sulcus, good definition around teeth.
Good impression
- 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
If patient gag how to handle ?
- 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
Complications with alginate
Anatomical- access , gag reflux, trismus, abnormalities
Local - irritation , allergy , eye contact , inhalation, ingestion
Psychological- anxiety , phobia
Spotter
Rate you impression . Good , ok , not fit
What went wrong.
How can it prevent
What is alginate
- Irreversible Hydrocolloid impression material
- Reaction occurs as calcium, salt, and phosphate dissolve
What do you look for in your alginate impression for good study model ?
- Fluid to record fine details
- Elasticity protects undercuts
-Compatible with plaster and dental stone
