Exam 3 Review Questions Flashcards
What are the steps for making a temporary out of transparent matrix?
- Select correct crown form by measuring mesiodistal width
- Estimate length and trim transparent crown form with scissors
- Try the crown in, allow for incisal thickness - do not seat flush with the edge of adjacent tooth
- Mark proximal contact spots and poke holes with a heated wire
- Fill matrix
- Seat crown with facial contours lined up for optimal esthetics
- Remove flash
- After 2 minutes remove crown from prep, wait 5 minutes and lift matrix off provisional
- Adjust, polish and finish provisional
What are the steps of working with a ProTemp pre-formed provisional?
- Measure the mesiodistal width to determine the prefabricated crown size
- The crown form chosen should be slightly smaller than the mesiodistal width of the space, too wide of a crown will result in distortion
- Record occlusal height using adjacent teeth to trim down ProTemp crown
- Apply vasoline to prep
- Remove ProTemp from package and remove protective covering
- Trim excess based on pre-measured occlusocervical height
- Seat ProTemp with light pressure and adjust cavosurface line angles and margins with TN 5475 instrument
- Place in maximum intercuspation and readapt all margins
- Light cure for 2-3 seconds buccal, readapt margins, light cure 2-3 seconds lingual, readapt margins, and light cure occlusal 2-3 seconds, then remove and light cure for 60 seconds
- Finish, polish
When is opaque porcelain applied and what are its functions?
- Applied first - onto the metal
- Functions
- Cover up the metal gray color
- Responsible for the chemical bond between metal and ceramic
What are some problems with all ceramic crowns (ACC’s)?
- Technique sensitive and time consuming luting procedure
- Brittle
- Fragility - occlusal adjustment after cementation
- Easy to leave margins rough causing gingival irritation
- Lack of repairability
- Inability to trial cement the restoration
- Greater potential for fracture - may not be wise to use on molars
What influences color?
- Object
- Observer
- Light
When is a Beveled Shoulder used?
- Used in MCC preps with a circumferential beveled metal margin.
- Absence of plaque adhesion at the cavosurface line angle is imperative to the long term success of the restoration. A polished metal margin provides excellent reduction in plaque adhesion and a minimal gap space between the restoration and the preparation, resulting in less potential for recurrent caries. Metal margins are typically recommended for posterior restorations as well as lingual and proximal areas that do not compromise the esthetic result
- 0.5 mm long bevel at 90˚ on a 1.5 mm shoulder, leaving new shoulder at 1.2 mm.
How do you know when to place boxes or grooves in a crown prep?
- If the ratio is less than 0.4, auxiliary features are necessary
- Retentive box may be required, due to caries or because a groove was placed in a misaligned position.
- All boxes and grooves should have the same path of withdrawal.
What does the ratio of axial wall height to occlusal diameter have to be in order to successfully retain a crown?
Greater or equal to 0.4
What measure is the intensity or saturation of a color?
Chroma
The relative darkness or lightness of a color, or brightness of an object is called what?
Value
What is the range of the color spectrum?
380-750 nm
What indicates how well a light source renders color as compared to a standard source?
CRI - Color Rendering Index
What is CRI affected by? (along with color temperature)
- Time of day
- Humidity
- Pollution
- Cloud cover
A CRI greater than what, is recommended for shade matching?
90
What are the 3 different light sources?
- Incandescent - yellow
- Fluorescent - blue (50-80 CRI)
- Natrual Daylight - closest to CRI 100
