2016 dr ghazy handout of principles of tooth preparations

11/24/2015

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By

Dr. Mohamed Hamed Ghazy

Professor of Fixed Prosthodontics

Faculty of Dentistry,

Mansoura University, Egypt

[email protected]

OCTOBER 31, 2015

Principles of Tooth PreparationWHAT 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

mailto:[email protected]

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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.




A. Prevention of damage during tooth preparation: 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 reductionRe-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 beProperly 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 casting50 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 elastomericImpression materials.

2- Chisel edge margin

Advantages

Conservation of tooth

structure,

Disadvantages

Location of margin

difficult to control.

Indication:

- occasionally on tiltedtooth.




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.

6. Preventing tooth fracture.

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





[email protected]

November 7, 2015

Principles of Tooth Preparation


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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 retentionWalls 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

DefinitionThat direction through which the restoration could beprecisely 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 OF A 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



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



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By





[email protected]

November 21, 2015

Principles of Tooth Preparation

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:Biological principles


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


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 alloyused 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

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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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Transcript of 2016 dr ghazy handout of principles of tooth preparations