Week 4 Flashcards
The different gypsum stones are classified based on?
Compressive strength
Type IV and V are classified based on?
Percentage of setting expansion
Type I is good for?
Used to mount casts to the articulator, used to be used to capture soft tissue impressions in denture patients.
What is Type II good for?
Rarely used. used in the investment and processing of dentures.
What is Type III Good for?
Diagnostic mounting
Pouring final impressions for denture, its easy to break out the denture after the final processing.
What is type IV good for?
Die stone
Used to fabricate crowns and bridge work.
Good at resisting abrasion
Good for PFM
Gold crowns
Noble/High Noble mettle
What is Type V good for?
High strength high expansion high strength stone
the larger shrinkage upon cooling when an base metal is used.
What is the W/P ratio?
the quotient obtained when the weight (or volume) of the water is divided by the weight of the powder.
as the W/P ratio increases, what happens?
the setting time increases, the strength of the gypsum product decreases, and the setting expansion decreases.
What Type IV high strength low expansion stone is used at ASDOH?
Excalibur
What is the proper way to mix stone with water?
Don’t guess the amount
Mix with spatula for about 15 seconds
Vacuum mix for 20-30 seconds
Type 1 mounting plaster states at ASDOH
W/P?
Working time?
Setting time?
W/P: 63 mL/100g
60-90 seconds
3 Min
When is a bite registration needed to mount?
when MIP is not stable due to missing or flat teeth
What happens when the bite registration is not all the way trimmed?
the bite registration will not sit on the casted stone
all but where the cusp tips articulate must be trimmed
When can a cast be mounted without bite registration?
When MIP is stable
When does a “record base” need to be fabricated?
When a “rock” or tipping will exists between two casts when not enough teeth are present to “tripodize” them.
this provides a platform for a bite registration to be made intraorally.
A record base can be made out of
pink TRIAD (UDMA).
What is the purpose of wax when making a record base?
A wax rim is added to the base to allow for quick adjustment of the height during the record appointment. 2-3 mm of space is created between the rim and teeth.
Why are V notches made in the record base?
V-notches are placed in the wax, so that the registration can be placed back on in the exact orientation every time.
record base must be fabricated of the?
the cast that is to be mounted (master cast). A record base made on another cast will not seat properly when transferred onto a cast from a different impression, even if the same type of impression material and stone is used.
There are two bite registration materials used in the clinic floor. What are they?
What material are they?
Regisil 2x
Take 1 Advanced
Both materials are fast setting PVS materials.
What is Regisil’s working time?
1m 10s
Do not confuse Regisil with?
Do not confuse this material with the medium body PVS as it is also purple in color.
Bite records for cross arch situations are to be taken with…
Regisil
This registration material is to be reserved for simple straightforward cases such as single unit crowns because of its quick setting time
Take 1
What is the Pindex system?
The pindex system prepares the master cast for crown fabrication
What is the advantage of the index system?
The advantage of the pindex system is that the die can be removed individually for ease of waxing
The interproximal regions and margins can be easily accessed and waxed with the die removed from the base. The die and wax up can then be placed back onto the base to wax up the crown to the proper interproximal and occlusal contacts.
The recommended thickness for die spacer is?
20 to 40 µm
A full contour wax up is performed if…
fabricating a full metal crown
A cut back of the wax is performed from the full contour wax up when…
fabricating a metal coping for a PFM crown.
The sprue should be attached to the
bulkiest noncritical part of the pattern
When casting multiple restorations, a ______is added to act as a reservoir for molten metal.
runner bar
The reservoir should be placed in the_________ Because?
center of the ring
correct placement of the wax pattern will ensure that the porosity will exist in the reservoir and not on the crown.
An investment must fulfill three important requirements:
- It must reproduce precisely the detailed form of the wax pattern.
- It must provide sufficient strength to withstand the heat of burnout and the actual casting of the molten metal.
- It must expand sufficiently to compensate for the solidification shrinkage of the alloy.
An investment material is primarily composed of…
and is made of?
A binder and the refractory material
Gypsum, phosphate or ethyl silicate Binder – provides rigidity
Refractory material function is to…
and is made of?
regulate thermal expansion of the investment material.
silica (quartz and cristobalite)
The investment material used at ASDOH is?
GC Fugivest II a phosphate bonded investment material.
The higher the noble content will result in the following properties when compared to base metal alloys:
1) Melting temperature - decrease
2) Shrinkage on cooling – decrease
3) Castability - better
4) Hardness – decreased
5) Corrosion – decrease (more resistant to corrosion)
High Noble alloy types used?
Gold-Silver-Platnum (Au-Ag-Pt)
Gold-Copper-Silver-palladium (Au-Cu-Ag-Pd)
Noble alloy types used?
Gold-Copper-Silver-Palladium (Au-Cu-Ag-Pd)
Gold-Silver-Palladium-indium (Au-Ag-Pd-In)
Palladium-Copper-Gallium (Pd-Cu-Ga)
Silver-Palladium (Ag-Pd)
What are the noble mettles of dentistry
Ruthenium(Ru) Rhodium (Rh) Palladium (Pd) Osmium (Os) Iridium (Ir) Platinum(Pt) Gold (Au)
What is not considered a noble mettle in dentistry?
Silver Ag
The higher noble content alloys result in…
crowns that have better adaptation to the die/preparation
he advantage of base metal alloys is
their low cost and rigidity in long span bridges/frameworks.
The strait line from the auditory meatus to the bridge of the nose in mounting a face bow.
Frankfort horizontal plane
the Frankfort horizontal plane is established by?
The lowest point on the orbitale (B) and the highest point on the margin of the external auditory meatus (A).
The average distance from the Nasion to the Frankfort Horizontal is…
23 mm
The 3rd point of reference allows us to triangulate the measurements so that the maxillary cast can be mounted accurately in all three dimensions
The Nasion
WHAT IS A TRIPLE TRAY IMPRESSION?
A triple tray, or dual arch impression, captures the teeth on the prepared arch, the opposing arch, and the jaw relation record.
What must a mouth must have for a triple tray impression to be accurate?
Adjacent healthy teeth
Articulation with face bow and full mount vs triple tray?
The principle difference between these two scenarios is that they follow a different arc of movement. Therefore the teeth with move across each other in a different pattern.
The face bow with the full arch will represent the Pt. moment more accurately.
Triple tray Contraindications
Multiple fixed units Fixed partial denture Survey crowns Implant supported fixed restorations No cases with Class II or III occlusion
Triple tray indications
Indication for occlusion is: Angle Class I occlusion,
mutually protected occlusiona
singlecrown bounded by intact teeth in the arch.
The teeth opposing the prepared tooth should have intact occlusal surfaces.
Also, the patient should be able to close all the way down into MI without interference.
Triple tray steps
- Select and evaluate a closed-mouth tray. Make sure the patient can close easily into maximal intercuspation without interference with the tray.
- Apply adhesive to tray walls. Load both sides of the closed-mouth tray.
- Concurrently, remove cord and, using a syringe, apply impression material onto critical areas.
- Place the loaded closed-mouth tray into position and have the patient close properly. Check the contralateral side to
verify maximum intercuspation. - Remove the polymerized impression, helping the patient open the mouth by applying pressure to the set material or tray border on the non-prepared side.
WHAT IS CONDYLAR INCLINATION?
The angle at which the condyle moves away from a horizontal reference plane is referred to as the “condylar guidance angle”
HOW DO WE FIND THE PATIENTS CONDYLAR INCLINATION?
By making a protrusive record. Instruct the patient to protrude their mandible forward to an edge to edge position. This will cause separation in the posterior region, where you can place bite registration material
By setting the angle on the articulator shallower than the average angle measured clinically, the clearance between the teeth in the mouth will be…
greater than what is seen on the articulator.
condylar inclination average
45 degrees
