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
