4. Lab Considerations I Flashcards
Polyether is hydro-(philic/phobic)
philic
Gluteraldehyde can be used to disinfect what impression materials
polysulfide and silicones
-NOT polyether, reversible and irreversible hydrocolloids
Iodophors
-Irreversible and reversible hydrocolloids, polysulfides, silicones and polyethers
Chlorine compounds can be used to disinfect what impression materials
-Irreversible and reversible hydrocolloids, polysulfides, silicones and polyethers
Complex phenolics can be used to disinfect what impression materials
Ye
- Polysulfide
- Silicones
No
- Polyehter
- irreversible hydrocolloid
- not enough data for reversible hydrocolloid
Phenolic gluteraldehyde can be used for what impression materials
Yes
- Reversible hydrocolloid
- Polysulfide
- Silicone
No
- Polyether
- Irreversible hydrocolloid
Common concerns of lab techs
- Insufficient info on work authorization
- Unsatisfactory tooth preps
- Deficient impressions
- Inadequate occlusal instruction and records
- Lack of knowledge of dental technology
ADA guidelines establishing the responsibilities of the dentist are
- Provide a signed, writeen and detailed instructions
- Accurate impressions, casts, occlusal records, and mounting
- ID finishlines (when not obvious)
- Indicate preferred materials with shade description
- Realistic
- Approval to proceed with modifications
- Infection control
- Return all casts for remakes
when is it the dentist’s responsibility to ditch the die
when the finishline isn’t clear (otherwise it can be done by the lab)
ADA responsibilities of the lab
- Follow dentist instructions
- Review unclear/questionable items
- Match shade described
- Notify dentist if work can’t proceed
- Complete work in timely manner
- Inform dentist of materials used
- Follow infection control
- Inform dentist of subcontracting
Metal issue card is needed for what crowns
CCC or PFM
Jade stone should set for how long
1 hr
What material is most commonly used for master casts
Gypsum
Advantages of gypsum
0Dimensionally accurate
- Low cost
- Easy to use
- Compatible with all impression materials ** Big advantage**
- Quick setting time
- **Capable of reproducing a 20 um wide line as prescribed by the ADA specification No. 19 for elastomeric impression materials
Disadvantages of gypsum
- Setting expansion
- Vulnerable to fracture upon retrieval from impression
- Poor abrasion resistance
Another name for resin rock is
epoxy resin
Advantages of resin rock are (compared to gypsum)
- Better abrasion resistance (due to reinforcement from resin)
- Less expansion (has resin which shrinks)
- Excellent surface details
- Stronger than gypsum –> resists fracture
Disadvantages of resin rock
- Technique sensitive
- Time consuming, long setting time
- Incompatible with some impression materials
- Polymerization shrinkage
What impression materials are not compatible with resin rock
polysulfide and hydrocolloid
Describe the process of making and electroplated die
- Impression placed in electroplating bath
- Later pure silver or copper is deposited on impression and supported with type IV stone/resin
Advantages of electroplated dies are
-Excellent abrasion resistance
Disadvantages of electroplated dies are
- Technique sensitive
- Time consuming
- Expensive
- Impression material incompatibility (Polyether, PVS= hard to plate)
Why should the master cast of the pindex only be 10 mm thick
- Avoid mounting issues
- Makes cuts easier
What are the critical features of adequate dies
- Accurately reproduce the teeth/preps
- Finish lines are accessible and clearly marked
- Seat completely in master cast base
- Are stable. No rocking, rotation/wobbling
- Independently removable
- Acces to end of pin
What must be returned to the lab if you are requesting a remake and why
- Old restoration
- Working casts
- Quality control from case of remake
- *Prevent repetition of mistakes
What are the minimum enclosures when submitting a case to the lab
- Working cast (pindex)
- Solid pour cast (must be full arch esp if it is zirconia
- Impression
- May also need bite reg. and mounted Dx casts
What does the lab need if you are submitting work for a survey crown for a partial
- RPD Design
- Tripoded survey cast
- Intraoral preps must be done before survey crown
What are the different MCC margin designs
- Metal margin
- Metal ceramic margin
- Ceramic margin
Different names for…
- Metal margin
- Metal ceramic margin
- Ceramic margin
- Metal margin –> metal collar
- Metal ceramic margin –> Metal Ceramic margin –> disappearing metal margin
- Ceramic margin –> porcelain margin
Which MCC margin design is the least and most esthetic
Least= metal collar (or metal margin) Most= ceramic/porcelain margin
What is the most and least conservative MCC margin
most= metal margin (metal collar) Least= ceramic margin
What burs are used for the following margins
- Metal margin
- Metal ceramic margin
- Ceramic margin
- Metal margin = chamfer
- Metal ceramic margin= Deep chamfer or slanted shoulder
- Ceramic margin = radial (or modified) shoulder
When are you likely to perscribe a metal occlusal on an MCC
- Limited restorative space
- Opposing metal restoration (if porcelain is highly polished it should be ok)
Define a high noble alloy
- Noble metal content > or equal to 60%
- Gold > or equal to 40%
Define titanium alloy
> or equal to 85%
Define Noble Alloys
> or equal to 25%
Define Base alloys
<25% noble
Metals of the platinum group include
- PT
- Pd
- Rhodium
- Iridium
- Osmium
- Ruthenium
What are the options for a noble alloy for a PFM and CC
PFM
-High Pd (white)
CCC
- Silver- PD or Ag-Pd (White)
- Au 40% (yellow)
High noble gold has _% Au
70
What return specs for the restoration do you want
- Polished metal
- Glazed porcelain
