CLASS 3 AND CLASS 4 Flashcards
Difference of class 3 and class 4?
Class 3 does NOT involve the incisal angle
What is the labial and gingival length in Class 4 cavity preparations?
6 mm
What it the axial depth of class 3?
1 mm
When you have a large cavity that is not confined to the enamel, what kind of class 4 should be done?
Beveled conventional tooth preparation
General tooth preparation involves?
Obtaining access to defect
Removing faulty structures
Creating the convenience form for the restoration
How does the restoration stick in class 3?
Chemical bonding
Additional preparation is required for class 3, T or F?
False but it can be done
When is addition retention form needed? and what do you do?
Large cavity
Increase the surface area with a wider enamel bevel
Indications for labial approach in class 3?
Carious lesion is located facially
Teeth are irregularly aligned
Extensive carious lesion extending into the facial surface
Faulty restoration that was placed from the facial approach that needs to be replaced
What bur is used in Lingual approach?
Round bur that is 0.7 or 0.8 mm
Where is the point of entry in lingual approach/
At the level of the lesion making sure to not hit the adjacent tooth
What kind of stroke is used to access the lesion in lingual approach?
Brush stroke, light pressure and intermittent cutting
What dictates the outline form of a class 3 in a normal tooth?
Carious lesion
Ideal axial wall depth in a Class 3
- 75 to 1.25 mm
0. 2 mm into the dentin
Shape of the normal external tooth contour that should be followed in a class 3 ?
Convex
This aids in the retention form of class 3
Boxlike design
Opposing wall parallelism
Slight undercuts
Rough prepared walls
When is beveling done in a class 3 cavity prep?
For replacing an existing defective restoration
For Large carious lesions
Where is the bevel placed, why? and when is beveling done, why?
Bevel is placed labially because mastication forces are too heavy on the lingual.
Beveling is done when the tooth or the CSM is not in contact with the opposing tooth during occlusion
What is the appearance of a class 3 cavity prep? Outline form, Axial Depth, Incisal and gingival wall and Labial depth?
Outline form - Rectangular with rounded sides
Axial depth - 1 mm
Incisal and gingival wall - 3 mm
Labial depth - 1.5 mm
Where is the class 3 cavity prep placed on a tooth?
Middle 3rd
What are the types of class 4 tooth preparations?
Conventional tooth preparation
Beveled conventional tooth preparation
Modified class 4 preparation
in this type of tooth preparation, beveling is not needed. why?
Conventional tooth preparation bc of the 90 degree CSM
This type of tooth preparation is used for Large cavities?
Beveled conventional tooth preparation
Retention in beveled conventional tooth preparation is obtained by?
Groove or other shaped undercuts
Dovetail extension
Threaded pins
