Principles of Tooth Preparation (Pt. I) Flashcards
Anatomy of Preparation
Planar occlusal reduction: ____
Functional and non-functional cusp bevel: ____
Seating
groove: ____
Axial reduction: ____
Finish line: ____
structural durability structural durability retention and resistance retention and resistance junction between restoration and preparation
Principles of Tooth Preparation
Biologic
Affects ____
Mechanical
Affects ____ of restoration
Esthetic
Affects ____ of patient
health of oral tissues
integrity and durability
appearance
I. Biologic Considerations
Prevent ____
damage
I. Biologic Considerations
Conservation of Tooth Structure
• Use ____ restorations, where possible
• Minimize ____ to maximize remaining tooth structure surrounding pulp
– Sufficient ____ necessary for restorative material
• Amount depends on ____ being used
– Thickness of remaining dentin
• inversely proportional to ____
• Avoid unnecessary apical extension of preparation
partial coverage reduction reduction restorative material pulpal response
I. Biologic Considerations
Conservation of Tooth Structure
With periodontally involved tooth, ____ margins preferred
____ extension of preparation results in additional tooth reduction due to decrease in ____ diameter
supragingival
apical
coronal
I. Biologic Considerations
Avoidance of Overcontouring
• Axial reduction
– Need ____ for development of
good axial contours
– Generally, crown should duplicate ____ of original tooth
• Unless correction of malformed or malposed tooth
insufficient axial reduction > ____ restoration > gingival ____
sufficient space
profile and contours
overcontoured
inflammation
I. Biologic Considerations
Avoidance of Overcontouring
For ceramo-metal restorations, adequate porcelain thickness is essential for ____ and ____
strength
esthetics
Once restorations are recontoured, gingival health ____
returns
I. Biologic Considerations Margins • (1)Margin \_\_\_\_ • (2)Margin \_\_\_\_ • (3)Margin \_\_\_\_
placement
adaptation
geometry
(1)Margin Placement
Supragingival vs. Subgingival
• Supragingival margins when possible
– Easier to prepare with ____ tissue trauma
– Usually in ____, not cementum or dentin
– Easier to keep ____-free
– Impressions or optical capture more easily made
• less soft tissue damage
– Restorations can be easily evaluated at time of ____ and recall appointments
minimal
enamel
plaque
placement
(1)Margin Placement Supragingival vs. Subgingival • Subgingival margins – Major etiologic factor in \_\_\_\_ disease – Indications • \_\_\_\_, cervical erosion, or subgingival restorations present • \_\_\_\_ extends to the gingival crest • \_\_\_\_ and/or resistance needed • \_\_\_\_ to hide margin • Inability to control \_\_\_\_
periodontal dental caries proximal contact area additional retention esthetics sensitivity
(2)Margin Adaptation
- Junction between restoration and tooth is always a potential site for ____ caries
- More accurately restoration is adapted to tooth, lesser chance of recurrent decay or periodontal disease
- Well designed preparation has smooth and even margin
- Rough, irregular or ____ junctions reduce adaptation accuracy of the restoration
recurrent
stepped
(2)Margin Adaptation
Time spent obtaining a smooth margin makes the subsequent steps of tissue displacement, impression making, die fabrication, waxing, and finishing much easier and results in a ____-lasting restoration
Smooth margins particularly important when fabricating restorations with ____ (computer-aided design/computer-aided manufacture)
longer
CAD/CAM
(3)Margin Geometry
• Margin configuration VERY controversial
• Guidelines for acceptable margin design
– Ease of preparation without ____ enamel
– Ease of ____ in impression and on die
– Distinct ____ to which wax pattern can be finished or design terminated
– Sufficient ____ of material
– Conservation of ____
overextension or unsupported identification boundary bulk tooth structure
(3)Margin Designs • (a)\_\_\_\_ • (b)Chamfer with \_\_\_\_ • (c)\_\_\_\_ • (d)Shoulder with\_\_\_\_ • (e)\_\_\_\_ shoulder • (f)\_\_\_\_ edge
chamfer bevel shoulder bevel sloped feather
(3)Margin Designs (a)Chamfer
• Chamfer finish line
– A design in which the ____ meets the external axial surface at an ____ angle
gingival aspect
obtuse
(3)Margin Designs (a)Chamfer
• Chamfer margin
– Tapered diamond
with rounded tip
– Hold along ____
path of placement
(3)Margin Designs (a)Chamfer
Tilting away will create ____ and ____ walls
Tilting toward tooth will ____ and result in excessive ____
undercut
divergent
over-reduce
contour
(3)Margin Designs (a)Chamfer
• The chamfer should never be prepared wider than ____ the tip of the diamond; otherwise an ____ lip of enamel may result
half
unsupported
(3)Margin Designs (a)Chamfer
Advantages
Distinct ____, adequate bulk easier to control
Disadvantages
Care to avoid ____ lip of enamel
Indications
____ restorations, lingual margin of metal- ceramic crowns
margin
unsupported
cast metal
(3)Margin Designs • Bevel – A slanting edge • May be more suitable for \_\_\_\_
• Objective
– Allow the cast metal margin to be ____ against the prepared tooth structure
• If do not have access to burnish, may be little advantage to ____
– Minimize ____ (??)
– Protect unprepared tooth structure from
____
• Removing ____ enamel
cast restorations bent or burnished marginal discrepancy chipping unsupported
(3)Margin Designs
Bevel
Effect of Bevel on Marginal fit at Gingival Margin
If internal cross section of crown is same or < prepared tooth»_space;> ____o bevel decreases marginal discrepancy by ____%
If internal diameter is slightly larger** than prepared tooth»_space;> Beveling increases ____
45
70
marginal discrepancy
Chamfer with bevel
Advantages:
____ of material, advantages of ____
Disadvantages:
Extends preparation ____
Indications:
____ restorations, lingual margin of ____ crowns
bulk bevel apically cast metal metal-ceramic
