2016 dr ghazy handout of principles of tooth preparations

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By
Dr. Mohamed Hamed Ghazy
Professor of Fixed Prosthodontics
Faculty of Dentistry,
Mansoura University, Egypt
mghazy@mans.edu.eg
OCTOBER 31, 2015
Principles of Tooth Preparation
WHAT IS A TOOTH PREPARATION?
a clinical procedure consisting of removal of
tooth structures and / or shaping of the tooth
to accommodate a fixed restoration
TOOTH REPLACEMENT
WHY
Problems in Fixed Restorations
Esthetic Problem
Occlusal Problem
Marginal Leakage
Crown Dislodgement / Non-retention
Periodontal Problem
Crown Perforation

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Problems in Fixed Restoration
Can be avoided by
Correct Tooth Preparation
What is a Correct Tooth Preparation?
What are the principles that govern
Tooth Preparation
WHAT IS A CORRECT TOOTH PREPARATION?
• Removal of tooth structure does not
weaken the tooth
• Amount of reduction follows the
requirements of restoration
• Resist displacement in all directions
• Presence of optimum tooth height
• Finish line that can accommodate
robust margin with close adaptation
• Provide optimal space for crown which
is sufficiently thick to prevent fracture,
distortion or perforation
• Unnecessary reduction
• Endangers the pulp
• Lack of retention and resistance
features
• Finish line that cause micro leakage
• Inadequate space for crown which is
thin and may cause fracture,
distortion or perforation
Incorrect Tooth PreparationCorrect Tooth Preparation
I- Diagnosis & treatment plane
phase.
II- Active Phase of Treatment:-
→ Tooth preparation.
→ Impression making.
→ Working cast & die.
→ Wax pattern.
→ Investing.
→ Casting.
→ Intra-oral try-in.
→ Cementation.
III- follow-up & maintenance.
The principles of tooth
preparation are divided
into 3 basic categories:-
1) Biologic considerations
… which affect the health of the oral
tissues.
2) Mechanical considerations
… which affect the integrity and
durability of the restoration.
3) Esthetic considerations
… which affect the appearance of the
patient.
What is Optimal ?
≠ Ideal ?
≠ Acceptable?

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Biological Principles
of
Tooth Preparation
maintenance of pulp vitality, adjacent teeth & soft tissues and
conservation of tooth structure
1) Prevention of damage during tooth preparation:-
1- Adjacent teeth.
2- Soft tissue.
3- Pulp.
2) Conservation of tooth structures.
3) Consideration affecting future dental health:-
1- Axial reduction.
2- Margin placement.
3- Margin adaptation.
4- Margin geometry.
5- Occlusal considerations.
6- Preventing tooth fracture.
Biological Principles
of Tooth Preparation:-
A. Prevention of damage during tooth preparation:
1- Adjacent teeth:-
- NEVER damage the adjacent tooth ….. Why ??
Prevention of damage during tooth preparation
1- Adjacent teeth.
2- Soft tissue. 3- Pulp.
Conservation of tooth structures.
Consideration affecting future dental health:-
1- Adjacent teeth:-
To prevent damage to adjacent tooth:-
Metal matrix band
Tooth being prepared
Prevention of damage during
tooth preparation:-
1- Adjacent teeth.
2- Soft tissue.
3- Pulp.
1- Adjacent teeth.

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2- Soft tissue:-
Mirror or saliva ejector To protect
tongue, lips & checks.
1- Adjacent teeth.
Zekrya,s gingival retractorRetraction cord
3- Pulp:-
- Care is needed to prevent pulpal injuries
Pulpitis pulpal degeneration.
- Freshly sectioned dentinal tubules (during
tooth preparation)
Provide a source for irritant to easily reach
pulpal tissues.
Irritant may be:-
- Temperature.
- Chemicals.
- Bacterial.
1- Adjacent teeth.
3- Pulp:-
The morphology of the pulp must be considered before
tooth preparation.
 Pulp size (seen in x-ray) … … … decrease with age.
 Pulp morphology … … … related to the coronal contour.
occlusocervically ≠ faciolingually
1- Adjacent teeth.

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3- Pulp:-
A- Temperature.
Heat generation is affected by:-
1- Excessive pressure
2- High rotational speed
3- Coolant type
4- Cutting instrument
(shape &condition)
• Use feather-light touch.
• Never without air-water cooling.
• Use low-speed with pin preparation.
•Use air-water cooling system
•Instrument with suitable abrasives.
•Avoid dull instrument.
1- Adjacent teeth.
Pin preparation must be done with low-speed
…. Why ???
1- Adjacent teeth.
3- Pulp:-
B- Chemical action.
Avoid use of chemicals to clean the tooth after preparation.
… because … it cause pulpal irritation.
Chemicals (e.g., base, resin, luting agent) placed over freshly
Cut dentin … … cause pulpal irritation.
Varnish or dentin bonding agent form a barrier against
these chemicals … but … it affect retention.
1- Adjacent teeth.
3- Pulp:-
C- Bacterial action.
When bacteria reaches the pulp … … can cause pulpal damage.
Incomplete caries removal.
 caries must be removed completely.
 In-direct pulp capping is not recommended.
Microleakage under cemented restoration.
 Use cement with minimal microleakage
& with anti-bacterial action.
1- Adjacent teeth.

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A. Prevention of damage during tooth preparation.
B. Conservation of tooth structure.
Conserve as much tooth structure
as possible (i.e. Avoid unnecessary
removal of tooth structure).
Tooth structure is conserved by:-
1) Use of partial coverage rather
than complete coverage.
2) minimal practical convergence
angle (taper) between axial
walls.
3) preparation of the occlusal surface
must follow the anatomical planes.

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4) preparation of the axial walls should
be done evenly.
if necessary, tooth should be
repositioned orthodontically.
Q: preparation done // long axis or ┴ occlusal plane ?
5) selection of margin
geometry that is
conservative & compatible
with other principles of
tooth preparation.
6) Avoid unnecessary apical
extension of the preparation.
A. Prevention of damage during tooth preparation.
C.Considerations affecting future dental health.
1)Axial reduction.
2) Margin placement.
3) Margin adaptation.
4) Margin geometry.
5)Occlusal considerations.
6) Preventing tooth fracture.

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A. Considerations affecting future
dental health.
1. Axial reduction.
- Over-contoured restorations is associated
with gingival inflammation.
… So … Preparation must provide sufficient space
to construct anatomically correct axial contour.
Over-contoured rest
+ Inflamed gingiva
Insufficient tooth reduction
Re-contoured rest
+ healthy gingiva.
1.Axial reduction.
2.Margin placement.
3.Margin adaptation.
4.Margin geometry.
5.Occlusal considerations.
6.Preventing tooth fracture.
dental health.
1. Axial reduction.
The inter-proximal & furcation area of posterior teeth must be
Properly contoured.
1.Axial reduction.
2.Margin placement.
4.Margin geometry.
dental health.
2. Margin placement.
The preparation margin should be supra-gingival (whenever possible).
Adv.,:- Easily prepared with superior accuracy.
Easily finished without soft tissue trauma.
Facilitate impression making with less soft tissue trauma.
… with CAD/CAM … facilitate optical capture.
Restoration margins can be easily evaluated during try-in
& at recall appointments.
More easily kept clean & plaque free.
1.Axial reduction.
2.Margin placement.
4.Margin geometry.
dental health.
2. Margin placement.
Sub-gingival margins are indicated in the following:-
Caries, cervical erosion or restoration extend subgingivally (crown
lengthening is contra-indicated).
Axial contour modification is needed ( undercut for RPD clasp).
Root sensitivity (can not be managed by more conservative procedure e.g.,
dentin bonding agent).
The margins of an esthetic restoration is to be hidden subgingivally.
Additional retention & resistance are needed.
The proximal contact area extends apically to the level of gingival crest.
1.Axial reduction.
2.Margin placement.
4.Margin geometry.

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dental health.
3. Margin adaptation.
Junction between cemented restoration &
the tooth is the potential site for recurrent
caries … … … Why ??
•The margin must be properly designed,
smooth & minimal marginal gab.
• Marginal gab range:
10 µm … … for casting
50 µm … … for porcelain
1.Axial reduction.
2.Margin placement.
4.Margin geometry.
dental health.
4.Margin geometry.
Cross-sectional configuration of the margin
= Finish line
= Line of demarcation between
prepared and unprepared
tooth structure.
1.Axial reduction.
2.Margin placement.
4.Margin geometry.
dental health.
4.Margin geometry.
Guidelines for margin design:-
(Requirement)
1. Ease of preparation.
2. Ease of identification in impression or optical scan.
3. Wax pattern can be easily finished & handled without distortion.
4. Conservation of tooth structure.
1.Axial reduction.
2.Margin placement.
4.Margin geometry.
dental health.
4.Margin geometry.
1- Feather edge margin
Advantages
-Conservation of tooth
structure.
Disadvantages
- Fail to provide adequate bulk at the margin.
Indication:
NOT recommended
(historically was used with copper band
Imp tech before development of elastomeric
Impression materials.
2- Chisel edge margin
Advantages
Conservation of tooth
structure,
Disadvantages
Location of margin
difficult to control.
Indication:
- occasionally on tilted
tooth.
1.Axial reduction.
2.Margin placement.
4.Margin geometry.

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dental health.
4.Margin geometry.
3- Beveled margin
Advantages
- Removes unsupported enamel.
- Allow finishing of metal.
Disadvantages
- Extends preparation into the sulcus (if used
on apical margin)
Indication:
- Facial margins of partial coverage
- inlay / onlay margins
1.Axial reduction.
2.Margin placement.
4.Margin geometry.
dental health.
4.Margin geometry.
4- Chamfer margin
Instrument:
Using tapered diamond with a rounded tip
The gingival margin is prepared with the diamond held
precisely in the intended path of withdrawal of the
restoration
1.Axial reduction.
2.Margin placement.
4.Margin geometry.
1.Axial reduction.
2.Margin placement.
4.Margin geometry.
dental health.
4.Margin geometry.
4- Chamfer margin
Advantages
• Distinct and easily identified.
• Provide adequate bulk of material at the margins
Disadvantages
• Care is needed to avoid leaving a ledge of unsupported
enamel
1.Axial reduction.
2.Margin placement.
4.Margin geometry.

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Indication
dental health.
4.Margin geometry.
4- Chamfer margin
Cast metal rest. , Lingual margin of metal-ceramic
restoration
1.Axial reduction.
2.Margin placement.
4.Margin geometry.
dental health.
4.Margin geometry.
5- Shoulder margin
Preparation
Using tapered diamond with a flat end.
It should form 90 degree angle with
unprepared tooth surface.
1.Axial reduction.
2.Margin placement.
4.Margin geometry.
Advantages
- Provide adequate bulk of material
Disadvantages
- Less conservative to tooth
structure
Indication
- Facial margin of metal ceramic restoration.
- All ceramic crown.
dental health.
4.Margin geometry.
5- Shoulder margin
1.Axial reduction.
2.Margin placement.
4.Margin geometry.
dental health.
4.Margin geometry.
5- Shoulder with bevel margin
Advantages
Provide adequate bulk of material, in addition
to advantage of bevel.
Disadvantages
Less conservative to tooth structure.
Extend preparation apically.
Indication
Facial margin of posterior metal ceramic
restoration in which facial metal collar is
used.
1.Axial reduction.
2.Margin placement.
4.Margin geometry.

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1.Axial reduction.
2.Margin placement.
4.Margin geometry.
1.Axial reduction.
2.Margin placement.
4.Margin geometry.
dental health.
4.Margin geometry.
6- Sloped Shoulder margin
Advantages
Provide adequate bulk of material,
in addition to advantage of bevel
Disadvantages
Less conservative to tooth
structure.
Indication
Facial margin of metal ceramic
restoration.
1.Axial reduction.
2.Margin placement.
4.Margin geometry.
1.Axial reduction.
2.Margin placement.
4.Margin geometry.

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5. Occlusal considerations.
Sometimes compromising the principle of
conservation is preferable to the potential harm that
result from traumatic occlusion.
c) Considerations affecting future
dental health.
1.Axial reduction.
2.Margin placement.
4.Margin geometry.
A satisfactory tooth preparation allows sufficient space to develop a functional
occlusal scheme in the finished restoration.
dental health.
No tooth is unbreakable
1.Axial reduction.
2.Margin placement.
4.Margin geometry.
6- Preventing tooth fracture
Tooth preparation should be designed to prevent fracture of
restored teeth.
Providing a cuspal coverage restoration (onlay) rather than an
inlay lessens the chance of such fracture.
However, although not conservative of tooth structure, a complete
crown is often a better solution.
1.Axial reduction.
2.Margin placement.
4.Margin geometry.
dental health.
By
mghazy@mans.edu.eg
November 7, 2015

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MECHANICAL CONSIDERATIONS
Biological principles
Mechanical principles
Retention form
1- Magnitude of dislodging forces
2- Geometry of tooth preparation
3- Roughness of the fitting surface of the restoration
4- Material being cemented
5- Type of luting agent
6- Film thickness of the luting agent
Resistance form
1- magnitude and direction of dislodging forces
3- Physical properties of luting agent
Deformation
1- Alloy selection
2- Adequate tooth reduction
3- Margin design
Esthetic principles
1- Providing Retention form
2- Providing Resistance form
3- Preventing deformation of restoration
(structure durability)
Retention form
3- Roughness of the fitting surface of the
restoration
Resistance form
1- Magnitude and direction of dislodging forces
Deformation
1- Alloy selection
3- Margin design
Esthetic principles
PRINCIPLES OF TOOTH PREPARATIONS
Definition:
The quality of a preparation that prevents
the restoration from becoming dislodged by
such forces parallel to the path of withdrawal
Retention form
Resistance form
Deformation
Esthetic principles
RETENTION FORM
 Forces that tend to remove a cemented restoration along its
path of withdrawal are small compared to those that tend to
seat or tilt it.
eg. Sticky food
Retention form
Resistance form
Preventing deformation of the restoration1. Magnitude of the dislodging forces:
RETENTION FORM

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a) Taper: Is the convergence of two opposing external
walls of a tooth preparation as viewed in a given plane.
Retention form
Resistance form
Preventing deformation of the restoration2. Geometry of the tooth Preparation:
RETENTION FORM
 External Internal
Retention form
Resistance form
RETENTION FORM
Axial walls of a preparation must taper slightly to permit the restoration to seat
Two opposing surfaces, each with a 3degree inclination (diamond held parallel
to the intended path of insertion) 6 degree taper
The more nearly parallel the opposing walls of a preparation, the greater
should be the retention
Walls are tapered:
-visualize preparation walls
-prevent undercuts
-compensate fabrication inaccuracies
-permit complete seating during cementation
Retention form
Resistance form
RETENTION FORM
What is the definition of Tipping Path?
It is the path along which the restoration, could be displaced
under the displacing occlusal force
Retention form
Resistance form
RETENTION FORM

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Path of insertion
Definition
That direction through which the restoration could be
precisely seated on the corresponding tooth or teeth
Parallel to the long axis of the tooth Parallel to the incisal 2/3 of the tooth
Retention form
Resistance form
RETENTION FORM
 b) Limiting number of paths of insertion
path of insertion: it is the direction through which the restoration could
be precisely seated on the prepared teeth.
Retention form
Resistance form
RETENTION FORM
PATH OF INSERTION OFA PREP. MUST PARALLEL
THE ADJACENT PROXIMAL CONTACTS
Retention form
Resistance form
RETENTION FORM
c) Type of preparation:
Complete coverage has closed curve while the grooves of the partial
coverage prevents movement  to the long axis of the tooth
Retention form
Resistance form
RETENTION FORM

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Retention form
Resistance form
RETENTION FORM
d) Undercuts
Retention form
Resistance form
RETENTION FORM
√ X
Retention form
3-Roughness of the fitting surface of the restoration
Resistance form
RETENTION FORM
PREP. IN THE MOUTH IS VIEWED THROUGH
A MOUTH MIRROR USING ONE EYE
Retention form
Resistance form
RETENTION FORM

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e) Surface area:
i) Preparation length:
Longer walls interfere with tipping displacement
Tipping path: It is the path along which the restoration
could be displaced under the displacing occlusal force
Retention form
Resistance form
RETENTION FORM
Short prep. can be improved by adding grooves
Retention form
Resistance form
RETENTION FORM
ii) Preparation diameter
Retention form
Resistance form
RETENTION FORM
f) Stress concentration
Sharp line angles
→ ↑ stress
→ ↑ failure
Retention form
Resistance form
RETENTION FORM

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Retention form
Resistance form
Preventing deformation of the restoration
3. Roughness of the fitting surface of the
restoration.
RETENTION FORM
The more reactive the alloy is, the more adhesion to the selected
cement.
 Base metal alloys > noble alloys.
 Amalgam core > composite and cast gold
Retention form
Resistance form
Preventing deformation of the restoration4.Materials being cemented
RETENTION FORM
Resin cement > conventional ones
Adhesive resin > glass ionomer > polycarboxylate > zinc
phosphate > zinc oxide-eugenol.
Retention form
Resistance form
Preventing deformation of the restoration5. Type of luting cement
RETENTION FORM
Retention form
Resistance form
Preventing deformation of the restoration5. Type of luting cement
RETENTION FORM

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Retention form
 1.Magnitude of the dislodging forces
 2.Geometry of the tooth preparation
 3. Roughness of the fitting surface of the restoration
 4.Materials being cemented
 5.type of luting cement
 6.Film thickness of the luting agent (uncertain)
6. Film thickness of the luting agent
Retention form
Resistance form
Preventing deformation of the restoration
RETENTION FORM
RESISTANCE FORM
 Def. It is the features of the tooth preparation
that enhance the stability of a restoration
and resist dislodgement along an axis other
than the path of withdrawal. (apical, oblique and
horizontal direction).
Retention form
Resistance form
Deformation
1- Alloy selection
3- Margin design
Esthetic principles
-Normal occlusion→ biting
forces ,well distributed and
axially directed → greater
resistance.
-Biting habits (pipe smoking-
bruxism) → large oblique
force →lower resistance.
Retention form
Resistance form
Deformation
Esthetic principles
A. Magnitude and direction of the dislodging
force.
RESISTANCE FORM
Tooth preparation must be shaped so that particular areas
(resistance areas) of the axial wall prevent rotation of the
crown
 1. Taper
Retention form
Resistance form
Deformation
Esthetic principlesB. Geometry of tooth preparation:
RESISTANCE FORM

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2. Diameter
Small (premolar) > large (molar).
Retention form
Resistance form
Deformation
RESISTANCE FORM
3. Height:
Long > short.
Retention form
Resistance form
Deformation
RESISTANCE FORM
4. Preparation type:
Complete coverage > Partial coverage (as no buccal resisting areas)
Retention form
Resistance form
Deformation
RESISTANCE FORM
Adhesive resin > Glass ionomer > Zinc phosphate > Zn
polycarboxylate > Zinc oxide-eugenol
C. Physical properties of the luting cement:
Retention form
Resistance form
Deformation
Esthetic principles
RESISTANCE FORM

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A restoration must have sufficient strength to
prevent permanent deformation during function.
Otherwise, it will fail.
Retention form
Resistance form
1- magnitude and direction of dislodging forces
Deformation
Esthetic principles3. Preventing deformation of the restoration
DEFORMATION MAY BE A RESULT OF:
1. Inappropriate alloy selection.
2. Inadequate tooth preparation.
3. Poor margin design.
4. Poor metal-ceramic framework design.
Retention form
Resistance form
Deformation
1- Alloy selection
3- Margin design
4. metal-ceramic framework design
Esthetic principles
3. Preventing deformation of the restoration
Type I and Type II gold alloys are
too soft for crowns and fixed partial
dentures.
Type III or Type IV gold alloys are
harder
1. Alloy selection
There should be a minimum alloy thickness
of about 1.5 mm over centric cusps
1 mm over non centric cusp
2. ADEQUATE TOOTH REDUCTION
Retention form
Resistance form
Deformation
1- Alloy selection
3- Margin design
Esthetic principles

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Occlusal reduction should be as uniform, following
the cuspal planes of the teeth thus will give
rigidity to the crown because of the "corrugated
effect" of the planes.
Retention form
Resistance form
Deformation
1- Alloy selection
3- Margin design
Esthetic principles
The supraerupted tooth may need considerably
more than 1.5 mm of reduction to result in
adequate clearance
Retention form
Resistance form
Deformation
1- Alloy selection
3- Margin design
Esthetic principles
Putty index made before tooth preparation
facilitates evaluation of tooth reduction
uniformity.
Retention form
Resistance form
Deformation
1- Alloy selection
3- Margin design
Esthetic principles
 Distortion of the restoration margin is
prevented by:
 1. Sufficient tooth reduction that provide
sufficient room for metal at the margin as
in case of a chamfer preparation.
3. MARGIN DESIGN
Retention form
Resistance form
Deformation
1- Alloy selection
3- Margin design
Esthetic principles

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 2. The grooves and ledges incorporated in a partial coverage
restoration provide essential strengthening for the casting,
particularly on anterior pinledge retainer.
3. MARGIN DESIGN
Retention form
Resistance form
Deformation
1- Alloy selection
3- Margin design
Esthetic principles
Proper framework design allows:
 a. Even thickness of porcelain veneer.
 b. Proper porcelain metal interface in framework design to allow
distinct margin.
Retention form
Resistance form
Deformation
1- Alloy selection
3- Margin design
Esthetic principles4. METAL-CERAMIC FRAMEWORK DESIGN
 c. Good connector design
 d. Optimally placed occlusal contact:
The centric stops can be located on either porcelain or metal, 1- 1.5
mm away from the junction
Retention form
Resistance form
Deformation
1- Alloy selection
3- Margin design
Esthetic principles4. METAL-CERAMIC FRAMEWORK DESIGN
 Existing restorations in the opposing arch can influence framework
design.
A porcelain restoration with a cast crown will abrade the gold.
Retention form
Resistance form
Deformation
1- Alloy selection
3- Margin design
Esthetic principles
4. METAL-CERAMIC FRAMEWORK DESIGN

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By
mghazy@mans.edu.eg
November 21, 2015
PRINCIPLES OF TOOTH PREPARATION
 Biological
considerations
Affect the health of the
oral tissues
 Mechanical
considerations
Affect of the integrity
and durability of the
restoration
 Esthetic
considerations
Affect the appearance
of the patient
ESTHETIC CONSIDERATIONS
 Determination of patient expectations and needs.
Esthetic principles
All ceramic restorations
Metal ceramic restorations
1. Facial tooth reduction
2. Incisal reduction
3. Proximal reduction
4. Labial margin placement
Partial coverage restorations
1- Proximal margin
2- Facial Margin
 High esthetic but less conservative (1-1.2mm)
Esthetic principles
1- Proximal margin
2- Facial Margin

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Esthetic restorations includes:
Esthetic principles
1- Proximal margin
2- Facial Margin
PRINCIPLES OF TOOTH PREPARATIONS
Esthetic principles
 All ceramic restorations
 Metal –ceramic restorations
 1- Facial surface reduction
 2- Incisal reduction
 3- Proximal reduction
 4- Labial margin placement
 Partial coverage restorations
 1- Proximal margin
 2- Facial margin
Esthetic principles
1- Proximal margin
2- Facial Margin
Can mimic original tooth color better than the
other restorative options can.
Includes :- inlays – onlays – veneers – crowns.
High esthetic but less conservative (1-1.2mm)
… so can not be used with thin teeth or teeth with
large pulps.
Esthetic principles
1- Proximal margin
2- Facial Margin
 The exact amount of reduction
depends to some extent on the
physical properties of the alloy
used for the substructure, and on the
manufacturer and the shade of
the porcelain.
 Minimum 1-1.3mm
Prepared in two distinct planes
Lower incisors → pulp exposure Or →
less than ideal esthetic
Esthetic principles
1- Proximal margin
2- Facial Margin

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-Adequate thickness of porcelain is needed to
create a sense of color depth and
translucency
-Minimum reduction of 1.5 mm is required
-Shade problems incisal and cervical 3rd of
restoration (here direct light reflection from
the opaque layer can make the restoration
appear very noticeable
-Opaque porcelain generally have a
different shade from body porcelain,
they often need to be modified with
special stains in these areas with
very thin teeth like mandibular
incisors.
Esthetic principles
1- Proximal margin
2- Facial Margin
Incisal edge with no metal backing → increase esthetic
Incisal edge  no metal backing.
So, it can be made with a
translucency similar to that of
natural tooth structure
-reduction  2 mm
-Excessive reduction – reduces retention
and resistance
Esthetic principles
1- Proximal margin
2- Facial Margin
 Metal ceramic junction is 1mm. lingual to the contact for better esthetic
- Esthetics depends on exact location of the metal ceramic junction in
complete restoration
- Proximal surface of anterior tooth will look most natural if they are
restored as the incisal edges without metal backing.
Esthetic principles
1- Proximal margin
2- Facial Margin
The margin should follow the contour of the free gingiva
Supragingival margin placement has many biologic advantages.
Nevertheless,
High lip line → Subgingival finishing line
Esthetic principles
1- Proximal margin
2- Facial Margin

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Mesial → just buccal to the proximal contact.
Angulation → follow the long axis of posterior teeth and incisal
2/3 of facial surface of anterior teeth
Esthetic principles
1- Proximal margin
2- Facial Margin
1. Proximal margin
Esthetic partial-coverage restorations depend
on accurate placement of the potentially
visible facial and proximal margins.
 Distal → further buccally as it is less
visible to all proper preparation,
finishing and access to oral hygiene
Esthetic principles
1- Proximal margin
2- Facial Margin
1. Proximal margin
Maxillary:
Just beyond the occluso-facial
line angle
Short bevel to prevent enamel
chipping.
Esthetic principles
1- Proximal margin
2- Facial Margin
2. Facial margin
Mandibular:
Facial chamfer as appearance is impaired by the
occlusal reduction.
Esthetic principles
1- Proximal margin
2- Facial Margin
2. Facial margin

11/24/2015
29
Esthetic principles
1- Proximal margin
2- Facial Margin
THANK YOU FOR YOUR
INTEREST

2016 dr ghazy handout of principles of tooth preparations

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