Quiz 4 Flashcards
What is a key advantage of low-fusing porcelains?
They are less abrasive.
The low-fusing porcelains are less abrasive to opposing tooth structures and can be repolished more easily after adjustments are made.
Which of the following is considered to be an intrinsic stain?
Tetracycline.
Tetracycline is an antibiotic that if taken during tooth bud development will produce intrinsic staining in the enamel. This type of stain can only be lightened by bleaching.
What is correct regarding power-whitening?
Patients are sent home with custom trays and additional whitening materials.
Power-whitening will not last indefinitely. Patients are supplied with custom whitening trays and additional whitening material to use at home in order to maintain the desired effect.
What is the approximate thickness of metal in a PFM crown where porcelain is bonded?
0.3 to 0.5 mm.
This allows for adequate thickness of the porcelain for color and strength.
What is the best way to protect oral tissues during a power-whitening appointment?
Dental dam.
Power-whitening materials are high-concentration gels and require the use of a dental dam and additional gingival protection with petroleum jelly or similar material.
What is the active ingredient in OTC bleaching materials?
Carbamide peroxide.
Carbamide peroxide products are popular for home whitening and are available in liquids or gels.
What is the process called when porcelain particles are melted and fused to metal?
Sintering.
Porcelain particles melt at their borders and fuse together, called sintering.
What do bleaching materials often contain to help reduce tooth sensitivity?
Fluoride.
Some bleaching products contain chemicals such as potassium nitrate or fluoride that are claimed to reduce or eliminate sensitivity during bleaching.
When should the shade of a tooth be taken?
Before preparation of the tooth and before a rubber dam is placed.
The color of the rubber dam can interfere with accurate matching.
Where should the shade tab be positioned when obtaining a shade match?
In the same plane as the tooth to be matched.
The shade tab should not be in front of the teeth or outside of the mouth.
What is true about computer-aided machining for crown and bridge techniques?
No die needs to be poured, and no temporary crown is necessary.
Dental offices that have these systems can prepare and deliver the restoration in the same visit.
Which ceramic dental material has a zirconium oxide or aluminum oxide matrix?
Polycrystalline ceramic.
The stronger ceramics often are used as a core over which esthetic porcelains are placed.
How do pressed ceramic veneers compare to feldspathic porcelain veneers?
Pressed ceramic veneers are thicker than feldspathic porcelain veneers and are too translucent for very dark teeth.
They require a deeper preparation of the tooth than feldspathic veneers.
What is most challenging when placing veneers?
The natural tooth structure is dark.
Dark teeth are more challenging to cover with veneers and achieve an esthetic result.
What is the major drawback of all-ceramic restorations in the posterior of the mouth?
Fracture rate.
The fracture rate for all-ceramic crowns in the posterior part of the mouth is higher than for PFM crowns.
What chroma and value does an extra light bleached tooth have?
Low chroma and high value.
Some manufacturers are starting to include bleaching shades that are extra light.
What can porcelain veneers be to hide the color of a darker natural tooth?
Opaque.
Using some opaque porcelain helps to hide the darkness.
Why should a leaking restoration be replaced before bleaching?
Prevent excessive penetration of bleach through dentinal tubules that might irritate the pulp and cause sensitivity.
Bleaching may be done as a prerestorative procedure.
What solution is used to condition the inside of the veneer?
Hydrofluoric acid.
To get the resin to stick to the porcelain, the internal surface of the veneer is roughened by etching it.
What is true regarding home bleaching prescribed by the dentist?
The gel is placed in a custom-formed soft, thin plastic tray and is worn by the patient for periods as short as 30 minutes twice daily or as long as overnight.
The home bleaching process is as effective as the in-office process but takes much longer.
