Casting Impressions Flashcards
How would you define occlusion
The way the top and bottom teeth meet together
Why is assessment of occlusion important
Affects daily life impacting quality of life
What is the condyle
The area of the mandible that is of direct interest of the TMJ, which articulate with the temporal bone
When does the condyle move along the articular eminence
When the TMJ is opened wide > 2mm example when yawning
What is terminal hinger axis
Rotation of condylar heads around an imaginary horizontal line
What could cause clicking from the TMJ
The condyle moving into and out of place on the articular disc
What could cause the patient to complain of locked jaw
Condyle is stuck behind the articular disc so patient finds it hard to open their mouth
What are some treatments of locked jaw
Warm compress
Wiggling the jaw
Muscle relaxants
How do we clinically identify possible signs of malocclusion
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
What position is reproducible to assess occlusion
Intercuspal position
How can contact points be assessed
Articulating paper
Shimstock
Cast models
Digital 3D/model
How can we tell forces are dissipated evenly
Stable forces will run down the long axis of the tooth
What is the thickness of shimstock
8 microns
What occurs with group function of the mandible
Molars on one side of the arch are all in contact while molars on the opposite side of the arch are not
What is the term when only the incisors come in contact when the mandible is shut
Incisor guidance
Molars do not occlude on both sides
What occurs with canine guidance
All teeth are not in contact
Don’t occlude while biting
What is a bruxist
A patient who grinds their teeth
What does hypertrophy mean
An overgrowth of gum tissue around the teeth
What are white lines on the soft tissues called
Linea alba
Why are impressions so important
-Medico-legal requirement
-Have a record of patient’s teeth for treatment planning when they are not there
-For the lab to work from
What are the stages of an impression
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.
What is the function of a facebow
Record the relationship between the maxillary plane and the position and angulation of the condyles to allow for replication for stimulation and analysis
What term is given which explains the condyle moving in a downward forward and inward direction and why does this occur
Translation
Patient is moving their mandible laterally (to one side)
What is the movement the jaw is doing if the condyles were moving downward and forward
Protrusion
What movement does a working side condyle make
Rotation
What movement does a non-working condyle make
Translation
Why are incisors and canines important in terms of mandibular movement
Incisor guidance is important in movements such as protrusion
Canine guidance is important in movements such as lateral excursion
What does ICP stand for
Intercuspal position
What does the upper palatal cusps occlude against in ICP
Lower marginal ridge and fossa
What do the lower incisors and canine tips occlude against in ICP
Upper cingulum
What are the two major categories of trays
Dentate (teeth)
Edentulous (no-teeth)
Which impressions do we begin with and why
Lower impressions as they are better tolerated and don’t trigger the gag reflex
What features indicated a successful impression
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
What is used for bite registration
Bite registration past or folded wax
What ingredients are used when casting impressions
30ml water
110g dental stone
What are the spikes on top of the cast when filling the mould
Stalagmites - used for retention
