intro to impression materials

Question 1

impression

Answer 1

detailed replica of teeth and surrounding tissues of the oral cavity

Question 2

when to use an impression

Answer 2

treatment planning
restorative dentistry
orthodontics
paediatric dentistry

Question 3

important properties of impression matierla for patient(short answer quesion)

Answer 3

neutrla taste/odour
short setting time
small tray
easily removed
no retakes 
non toxic

Question 4

important properties of impression matierla for dentist (short answer quesion)

Answer 4

easily mixed
short working times
good quality impressions
low cost
easily disinfected simple procedure
no retakes 
non toxic

Question 5

how to choose the impression material

Answer 5

dependant on presence of teeth
affected by impression technique
selection of tray

Question 6

types of impression material

Answer 6

rigid

flexible

Question 7

rigid impression material

Answer 7

for no teeth
waxes
zinc oxide/eugenol
plaster of paris

Question 8

flexible impression material

Answer 8

hydrocolloids (agar and algeniate)

elastomers (polysulphide, polyether and silicone polymers)

Question 9

what allergic reaction will be with zinc oxide/eugenol

Answer 9

sticky plasters

Question 10

rigid materials use/properties

Answer 10

cannot engage undercuts present on teeth or bone
cannot be used in dentate patients
mainly restricted to endentulous patients with no bony undercuts

Question 11

elastic materials use/properties

Answer 11

can engage undercuts

can be used in tooth/non tooth

Question 12

hydrocolloids

Answer 12

heterogeneous mixture of two phases where the two phases are not readily differentiated

Question 13

solution

Answer 13

homogenous mixture consisting of a single phase

Question 14

suspension

Answer 14

mixture of two phases

Question 15

setting reaction

Answer 15

powder and water
chemical reactions that crosslink polymer chain
crosslinks cannot be broken
solution to gel

Question 16

aliginate

Answer 16

based on alginic acid
forms water soluble salt
good for primary impressions
not good enough for crown/rbidge

Question 17

good properties of algiate

Answer 17

dust free powder
short setting time
well controlled working time
mucostatic
hydorphilic
cheap

Question 18

bad properties of alignate

Answer 18

poor surface reproduction
poor storage stability 
low tear strength
excessive permanent deformation
limited shelf life