Casting Impressions

Question 1

How would you define occlusion

Answer 1

The way the top and bottom teeth meet together

Question 2

Why is assessment of occlusion important

Answer 2

Affects daily life impacting quality of life

Question 3

What is the condyle

Answer 3

The area of the mandible that is of direct interest of the TMJ, which articulate with the temporal bone

Question 4

When does the condyle move along the articular eminence

Answer 4

When the TMJ is opened wide > 2mm example when yawning

Question 5

What is terminal hinger axis

Answer 5

Rotation of condylar heads around an imaginary horizontal line

Question 6

What could cause clicking from the TMJ

Answer 6

The condyle moving into and out of place on the articular disc

Question 7

What could cause the patient to complain of locked jaw

Answer 7

Condyle is stuck behind the articular disc so patient finds it hard to open their mouth

Question 8

What are some treatments of locked jaw

Answer 8

Warm compress
Wiggling the jaw
Muscle relaxants

Question 9

How do we clinically identify possible signs of malocclusion

Answer 9

Extra orally
-symmetry
-muscles of mastication tender
-TMJ clicking
-Lips, traumatic lesions

Intra orally
-white line on buccal mucosa (Linea alba)
-tongue, scalloped margins
-gingiva, traumatic lesions
-teeth are worn or restored

Question 10

What position is reproducible to assess occlusion

Answer 10

Intercuspal position

Question 11

How can contact points be assessed

Answer 11

Articulating paper
Shimstock
Cast models
Digital 3D/model

Question 12

How can we tell forces are dissipated evenly

Answer 12

Stable forces will run down the long axis of the tooth

Question 13

What is the thickness of shimstock

Answer 13

8 microns

Question 14

What occurs with group function of the mandible

Answer 14

Molars on one side of the arch are all in contact while molars on the opposite side of the arch are not

Question 15

What is the term when only the incisors come in contact when the mandible is shut

Answer 15

Incisor guidance
Molars do not occlude on both sides

Question 16

What occurs with canine guidance

Answer 16

All teeth are not in contact
Don’t occlude while biting

Question 17

What is a bruxist

Answer 17

A patient who grinds their teeth

Question 18

What does hypertrophy mean

Answer 18

An overgrowth of gum tissue around the teeth

Question 19

What are white lines on the soft tissues called

Answer 19

Linea alba

Question 20

Why are impressions so important

Answer 20

-Medico-legal requirement
-Have a record of patient’s teeth for treatment planning when they are not there
-For the lab to work from

Question 21

What are the stages of an impression

Answer 21

Check pateint’s occlusion. Do they have reproducible occlusion? ​
a) If they do – miss step 6​
b) If they do not include step 6​

Select correct tray​

Select correct adhesive for the tray and wait for it to dry (depends on manufactures guidelines)​

Prepare impression material and load it into the tray (usually tray for lower dentition first)​

Position it correctly in patients mouth and hold in place, border molding until the impression material hardens​

Take it out and inspect it. If okay repeat with upper tray.​

Record patient’s occlusion using a suitable technique (e.g. softened wax wafer, bite registration paste)​

Place impressions in perform for 10 minutes minimum. ​

Fill out lab card correctly​

Wrap impression materials in damp material (e.g. damp tissues) and place in a container (with bite registration included if necessary). Attach the lap prescription.​

Question 22

What is the function of a facebow

Answer 22

Record the relationship between the maxillary plane and the position and angulation of the condyles to allow for replication for stimulation and analysis

Question 23

What term is given which explains the condyle moving in a downward forward and inward direction and why does this occur

Answer 23

Translation
Patient is moving their mandible laterally (to one side)

Question 24

What is the movement the jaw is doing if the condyles were moving downward and forward

Answer 24

Protrusion

Question 25

What movement does a working side condyle make

Answer 25

Rotation

Question 26

What movement does a non-working condyle make

Answer 26

Translation

Question 27

Why are incisors and canines important in terms of mandibular movement

Answer 27

Incisor guidance is important in movements such as protrusion

Canine guidance is important in movements such as lateral excursion

Question 28

What does ICP stand for

Answer 28

Intercuspal position

Question 29

What does the upper palatal cusps occlude against in ICP

Answer 29

Lower marginal ridge and fossa

Question 30

What do the lower incisors and canine tips occlude against in ICP

Answer 30

Upper cingulum

Question 31

What are the two major categories of trays

Answer 31

Dentate (teeth)
Edentulous (no-teeth)

Question 32

Which impressions do we begin with and why

Answer 32

Lower impressions as they are better tolerated and don’t trigger the gag reflex

Question 33

What features indicated a successful impression

Answer 33

Capture all the anatomy from the arch
Uniform impression
Rounded edges which mean depth of sulcus captured
Teeth and anatomy clear to see
Tray not showing through the impression

Question 34

What is used for bite registration

Answer 34

Bite registration past or folded wax

Question 35

What ingredients are used when casting impressions

Answer 35

30ml water
110g dental stone

Question 36

What are the spikes on top of the cast when filling the mould

Answer 36

Stalagmites - used for retention