02: Principles of Tooth Preparation Flashcards
What is the primary indication for preparation for indirect restoration?
Significant coronal tooth loss or destruction
What are some causes for significant coronal tooth loss or destruction
Large restoration that has failed
Gross caries with significant coronal damage
Trauma resulting in damage or loss of total coronal tooth structure
Retainer for suspending pontics to replace missing teeth
What does CVC mean?
Complete Veneer Crown
What is the first step in preparation design?
Path of Insertion
What does an extracoronal restoration use for retention?
Opposing external surfaces
What does an intracoronal restoration use for retention?
Opposing internal surfaces
What is the degree measurement of the ideal taper?
12 degrees
What are two important considerations of the path of insertion?
Free of undercuts and appropriately aligned
What must the path of insertion be parallel to?
The adjacent proximal contacts
What happens if the path of insertion is not parallel to the proximal contacts?
It will be prevented from seating
What is the purpose of tapering?
It provides both resistance and retention
What are four forms of auxillary retention?
Box
Groove
Pin Hole
Steps
What is the critical skill for the preparation?
Prepare the tooth with an ideal tapered path of placement free of undercuts.
Without damaging the adjacent tooth.
What is something that the patient must be made aware of when they are thinking about purely cosmetic dentistry?
Conservation of Tooth Structure
What crowns resulted in the least amount of lost tooth structure?
Ceramic veneers and Resin bonded retainers (3-30%)
When teeth were prepared for all ceramic and metal ceramic crowns, how much coronal structure was lost?
63-72%
Compared to conventional crowns, how much tooth structure was removed for porcelain laminate veneers and resin bonded prostheses?
1/4-1/2 the amount
In molars that are 3-4 mm in height, exceeding a _________ degree single axial inclination angle is detrimental to overall surface area
10
Students are taught a 2-5 degree taper with a 1.2-1-5 mm occlusal clearance….very hard to do. What percent of all prepared teeth meet that criteria?
12.7%
What was the average taper angle?
9.5 degrees
What was the average abutment height?
4.8-6.9 mm
Besides boxes, grooves, and pinholes, what is another form of auxiliary retention?
Steps
What type of margin placement (finish line) is better at promoting future gingival health than the other options?
Supragingival
Is it more common for dental students to undertaper or overtaper?
Overtaper
What is step 1 of the surveying exercise?
Get measurement instruments
What is step 2 of the exercise
Select mandibular arch “E”
After getting the mandibular arch “E” what is the next step
Affix the mandibular arch in the surveyor table
Once the mandibular arch is affixed in the surveyor table, what is the next step?
Adjust the table tilt and locate the path of insertion and undercuts
After surveying the mandibular arch on the table, what do we do?
Mark any undercuts with the graphite rod
Does a CAD/CAM mill require more or less taper than a traditional crown made in a lab?
More (slightly)
Lecture Quiz Question 2: Reducing the paths of removal increases……?
Retention
What height tooth can get away with more taper? (Tall or Short)
Tall because there is more surface area
Quiz Question 3: A prep on a tooth with a small diameter resists pivoting movements ____________ (Worse than/Better than) a prep of equal length on a tooth or larger diameter.
Better than
Quiz Question 4: The resistance of this short preparation has been ________ (Improved/Reduced) by adding grooves
Improved
If you have a choice, where is preferred placement of the margin (Supragingival/Subgingival)
Supragingival
For marginal integrity and fit, what type of shoulder do we use (slope/bevel)
slope
To help surface texture, what type of diamond bur should you try to use (Coarse/Fine)
Fine
What are some results of poor marginal integrity
Bad fit and contours can trap bacteria and cause many more problems.
