PRINCIPLES OF PREPARATION FOR CAST RESTORATIONSDEEPTHI P.R.

II YEAR MDS

CONTENTS Introduction

Preparation path

Apico occlusal taper of a preparation

Preparation features of the circumferential tie

Mechanical problems for cast restorations and preparation design solutions in general

INTRODUCTION Cast alloys & ceramics: intracoronal & extracoronal

Intracoronal: ‘ Mortise’ shaped, definite walls & floors joined at line angles, point angles

Extracoronal: Occlusal and axial surface reduction, ending gingivally with no definite flat floor

General principles of tooth preparation- applicable

Greater surface extension in outline form than amalgam

support for tooth structure

excellent marginal manipulation

compensates for cariously weak joints :

self- cleansable & /or protection

PREPARATION PATH Single insertion path: opposite to the direction of occlusal loading- function will seat restoration rather than displace it

Tooth reduction: oriented in one path, the path of withdrawal & insertion of the future wax pattern & restoration

Parallel to the long axis of the tooth crown

Enhanced retention & reduced micro movements during function

APICO-OCCLUSAL TAPER OF A PREPARATION

Opposing walls & axial surfaces: perfectly parallel to each other-

- maximum retention

- materials inserted & withdrawn from preparation

- permanent deformation: impractical technique/ misfitting restorations

Exact parallelism: technical problems

Slight divergence of opposing walls intracoronally & slight convergence of opposing axial surfaces extracoronally

APICO-OCCLUSAL TAPER OF A PREPARATION

2 to 5 degrees from the path of preparation – increased or decreased:

1. Length of the preparation wall and/or axial surfaces

The greater the wall length is, the more taper will b necessary: not> 10 degrees

The less the wall length is, the less the taper will be, approaching 0 degrees: but should not be less in extremely short walls

2. Dimensions and details of surface involvement and internal anatomy in the preparation

The greater the surface involved

The more detailed the internal anatomy

Taper increased: not > 10 degrees- to diminish friction

Frictional component between the preparation & the contacting materials: distortion in materials used

APICO-OCCLUSAL TAPER OF A PREPARATION

3. The need for retention

The greater the need: the lesser the taper- approach parallelism

Greater occlusal reduction and rounded internal & external anatomy for non noble alloys & cast ceramics - less taper to compensate for loss of retention

Taper: equally at the expense of two opposing walls/ axial surfaces- one path of insertion

Solely at the expense of one side only: opposing side absolutely parallel to insertion path

APICO-OCCLUSAL TAPER OF A PREPARATION

Preparation should not be made with one side having more taper than the other:

More than one path of insertion

Micromovements of the final restoration

If cariogenic & anatomical conditions dictate two different tapers for opposing walls: preferable to create two planes- inner & outer

Inner planes: parallel to each other or of equal taper- assure single path of insertion

Outer planes: satisfy the needs compelling different tapers

APICO-OCCLUSAL TAPER OF A PREPARATION

Factors determining the choice of design

Cariogenic & anatomical considerations

Different lengths of opposing parts of the preparation

Need for reciprocal retention

Presence of more surrounding walls/ axial surfaces on one side than the other

PREPARATION FEATURES OF THE CIRCUMFERENTIAL TIE

Tooth/ cement/ cast joint complex: weakest link

Peripheral marginal anatomy: Circumferential tie

Marginal peripheries: designed for the most favorable relationship between the restoring casting and the luting cement

Margin ends on enamel: Fulfill Noy’s requirements for ideal cavity wall

- enamel must be supported by sound dentin

- enamel rods forming the cavosurface margin should be continuous with sound dentin

- enamel rods forming the cavosurface margin should be covered with the restorative material

- angular cavosurface angles should be trimmed

PREPARATION FEATURES OF THE CIRCUMFERENTIAL TIE: Intracoronal

BEVEL A plane of a cavity wall or floor directed away from the cavity preparation

Six types according to the shape and tissue involvement

A. Partial bevel

B. Short bevel

C. Long bevel

D. Full bevel

E. Counterbevel

F. Hollow ground / Concave bevel

BEVELS PARTIAL BEVEL

Part of the enamel wall not > 2/3rd of its dimension

Not used usually

Trims weak enamel rods from margin peripheries

SHORT BEVEL

The entire enamel wall, but not dentin

Used mostly with Class I alloys especially for type 1 and 2

BEVELS LONG BEVEL

Enamel wall and upto one half of the dentinal wall

Most frequently used for the first 3 classes of materials

Preserves the internal “boxed up” retention and resistance features

FULL BEVEL

All of the enamel and dentinal walls of the cavity wall or floor

Well reproduced by all 4 classes of alloys

Deprives the preparation of the internal resistance & retention

Used only when any other bevel is impossible to b used

BEVELS COUNTERBEVEL

Capping cusps to protect and support them

Bevel used opposite to a an axial wall- on the facial or lingual surface

Gingival inclination facially or lingually

HOLLOW GROUND/ CONCAVE BEVEL

Any bevel especially long, full or counter bevels when prepared in a concave form

More space for cast material: material’s castability, retention and better resistance to stresses

Ideal for Class IV and V

BEVELS- Functions Bevel portion: specific angulation relative to the remaining portion of the wall/ floor, the long axis of the crowns or a specific landmark

Extend to certain limits

Create obtuse- angled marginal tooth structure: bulkiest & strongest configuration

Acute angled marginal cast alloy substance: most amenable to burnishing

Eliminates the cement line by bringing the cast alloy closer to tooth structure

BEVELS- Functions Only circumferential tie with possibility of a direct retentive frictional component between the casting & tooth

Resistance form of tooth- restoration complex by encompassing cusps

Compensate for problems in the castability of alloys- produce better details for retention

“Flexible extensions” of a cavity preparation, allowing the inclusion of surface defects, supplementary grooves, or other areas on the tooth surface.

Minimum tooth involvement and no sacrifice of the resistance & retention

Gingival bevels: Gingival margins to cleansable or protected areas

Facial & lingual proximal walls:

FLARES Flat or concave peripheral portions of the facial and lingual walls

Facial and lingual proximal walls in intracoronal cavity preparations for castings

2 types: Primary & Secondary

PRIMARY FLARE:

The conventional and basic part of the circumferential tie facially & lingually for an intracoronal preparation

Similar to long bevel

Specific angulation: 450 to the inner dentinal wall proper

Hollow ground: cast ceramics/ non noble alloys

FLARES Functions: same as bevels

The most peripheral part of proximal preparation: if they fulfill the objectives of a circumferential tie

SECONDARY FLARE

A flat plane superimposed peripherally to a primary flare

Sometimes, prepared in hollow ground form to accommodate materials with low castability

Solely in enamel, with some dentin in all or parts of its surfaces

Different angulations, involvement & extent, depending on function

FLARES: Functions & Indications

-Bucco- lingual wide extensions- primary flare ending with acute angled margins

Secondary flare at correct angulation- the needed obtuse angle of marginal tooth structure

- Broad/ malposed contact areas

Finishable cleansable areas without changing the fixed angulation of the primary flare

- Ovoid teeth: peripheral marginal undercuts occlusoapically on the facial &/or lingual peripheries of a cavity

Secondary flare at correct angulation-eliminate these undercuts with minimal sacrifice of tooth structure

- Surface defects/ decalcifications: involved in preparation without extending the primary flare

CIRCUMFERENTIAL TIE: Extracoronal

CHAMFER FINISHING LINE

Class I, II, III materials

Bulk & definite termination for the preparation marginally, with little tooth involvement – 0.5mm maximal depth

Placed gingivally on any involved axial surface: if finishable- cleansable / protected

Subgingival extracoronal preparations if gingiva floor considerations are precluded

Contraindicated: Class IV & V materials

DisadvantagesLiability of transitional

continuation of a circumferentia tie with

adjacent bevel ties

Limited burnishability of marginal cast alloy

CIRCUMFERENTIAL TIE: Extracoronal

KNIFE EDGE/ FEATHER EDGE FINISHING LINE:

The least tooth structure involvement

Involves enamel only: when the margin is on enamel

Very castable- burnishable type of alloy- Type II Gold alloy

Accessible areas of tooth surface for proper finishing

Minimal axial depth required for biologic / anatomic purposes

Easy & efficient blending with beveled constituents

CIRCUMFERENTIAL TIE: Extracoronal

Disadvantages:

Indefinite termination for the casting

Margins not being covered with a casting: less wetting alloys

Risk of fracture: burnishing-finishing-polishing

Definite contraindication: Class III, IV, V materials

Thin cross- section

Ease of over- strain- hardening

CIRCUMFERENTIAL TIE: Extracoronal

BEVELLED SHOULDER FINISHING LINE:

The most tooth structure involvement

Definite gingival floor: wall proper + bevel

Maximum bulk of the cast is needed marginally for materials that are limited in their castability & burnishability

Easy blending with the bevelled constituents

Maximum reduction of marginal problems of internal spacing

Ideal for subgingivally located margins- maximum predictability of the casting termination gingivally

CIRCUMFERENTIAL TIE: Extracoronal

HOLLOW GROUND/ CONCAVE BEVEL:

Exaggerated chamfer or a concave beveled shoulder

Tooth involvement : Chamfer< Hollow ground < Bevelled shoulder

Termination: not as predictable, but mechanically comparable to a beveled shoulder

Superior to chamfer

Care: no residual frail enamel/ thinned tooth structure

CIRCUMFERENTIAL TIE: Extracoronal

Advantages:

Good transitional continuity with the beveled portion of the circumferential tie

Helps the casting to seat preferentially

Aids in stabilizing the casting

Ideal for Class IV & V cast materials

Used successfully for materials with limited castability

CIRCUMFERENTIAL TIE: Extracoronal

Functions similar to bevels & gingival floors

Minimize symptoms of internal spacing marginally: chamfer & hollow ground

Combinations used: cariogenic & anatomic needs; castability & finishability of restorative material

Avoid sharp angles/ interruptions at the junction

of the gingival & occlusal corners of the tie

Round the junctions at the level of the circumferential tie,

not internally

• Avoid stress concentration• Non coverage of the margin by the

casting• Possible minor undercuts

CIRCUMFERENTIAL TIE: Extracoronal

Maximal depth at the junction of the tie with the wall/ floor/ axial surface

Complete reproduction and coverage of the details in the casting

Best resist stresses

No element in occlusal contact

Peripheral margin: linear- paralleling the periphery/ curvature of anatomy

Smoothest & continuous: impression materials, die materials, waxes, investment, alloy & ceramic melts can wet details- precise reproduction

AUXILLARY MEANS OF RETENTION

Compound & complex tooth involvement

Formability of cast restorations: myriad retention & resistance means

Luting cementsGroovesReverse bevelInternal box External boxesSlotPins

CollarSkirtsCapping of cuspsCapping of the marginal ridgePostsGross roughening

Reciprocal retentionCapping of occluso- proximo- facial or lingual corners Precementation groovingElectrolytic etching

LUTING CEMENTS Locking the cast to tooth structure

Auxillary: can’t substitute frictional retention

Susceptible to dissolution & weaker than casting or tooth structure

The less the cement thickness- the less the possibility of clinically recognizable failure at tooth- cement-casting interface

Fill the space between them

Fill the vacancies or irregularities

Wet the details of both casting & tooth

preparation

GROOVESCompletely in dentinInternal grooves: as internal as possible, adjacent to the axial wall

Prevents lateral displacement of mesial, distal, facial &/or lingual parts Stepped to preserve anatomical landmarks, increase locking capabilitiesIndicated: dimensions are limited & ocking mechanism needed proximally

Dentinal portion of the facial/ lingual

walls

Gingival floors proximally Mesial or distal walls

Gingival floors of the facial or lingual

portion

GROOVES Contraindicated:

- impinge on the pulp chamber or root canal system

- undermine/ involve axial angle of the tooth

- undermine adjacent enamel

External grooves: Preparations lacking retention

Short/ severe taper/ extreme width

Placed in areas of sufficient dentin bulk

Periphery of surface extension

Cut in a step form inwards or outwards- increases locking

GROOVES Reciprocal means of retention: improves seating of the restoration, minimize marginal discrepancies

Standardized tapered fissure bur: No. 168/ 699

Maximum 2mm depth- at the expense of the side walls or axial surfaces

Accentuated: Wedelstaedt/ Hatchet

All types of cast materials: ceramics- no definite internal line angles

REVERSE BEVEL Expense of the gingival floor- internal dentinal plane inclining gingivally- axially

Locks the restoration & prevents proximal displacement

Flat dentinal transition with the gingival bevel

Gingival floor with sufficient dimension without decreasing the resistance

Gingival marginal trimmers

Class I, II, III materials- rarely class IV

INTERNAL BOX One of the most efficient immobilizing retention resistance means

In dentin

4 vertical surrounding walls joining the floor at definite line and point angles

Next to a marginal ridge with intact proximal wall as one of the walls

Anywhere in the preparation floor with sufficient dentin bulk

Peripheries : ideal location for even immobilization

Reciprocated at the opposite ends of the preparation

Shallow cavities/ short preparations- dovetail cannot be prepared

INTERNAL BOXMinimum 2mm in three dimensions, but not equal length, width, depth

Stepped apically or occlusally with different levels in th epulpal floor

No. 168/ 699

Surrounding walls shaved to be parallel & have definite angles: Hatchet, Monangle chisel, angle former

Contraindicated: Class IV & V materials

EXTERNAL BOX Box shaped preparations opening to the axial tooth surface

3,4,5 surrounding walls & floors- proximal, facial or lingual

Stepped occlusally or gingivally or not stepped

Accommodate grooves in their surrounding walls

Peripheral portions: beveled or flared

Armamentaria: similar to internal box

Contraindicated for cast ceramics

SLOT Internal cavity- floor of a preparation

Continuous surrounding wall – non defined angles & floor, junction between floor and walls very rounded

Less locking, but more readily reproduced in casting

Indication: same as internal box

Suitable size round bur & tapered fissure bur

2-3 mm depth – compatible dimensions with the size of restoration

All five classes of materials

PINS Cemented & threaded/ Parallel & non- parallel/ Vertical & horizontal/ Cast & wrought

Used for Pinlay design of cast restoration

I. According to the mode of incorporating in a casting

A. Wrought pins: Cast on/ Soldered. Threaded in

B. Cast pins

II. According to their relationship to the ong axis of the tooth

A. Vertical

B. Horizontal

COLLAR, SKIRTS, CAPS, POSTS COLLAR: Surface extension completely surrounding a cusp or a surface of a tooth

SKIRT: A Specific extension involving a part of the axial angle of a tooth

Part of surface extension preparation designs

CAPPING OF CUSPS: Very efficient if the cusp is not shortened to the extent that it will not effective in locking the restoration

Hollow- ground bevel/ hollow- ground bevel collar

CAPPING OF MARGINAL RIDGES: Finishable cleansable finish line created

Intact marginal ridge, sound adjacent proximal surface & pronounced occlusal embrasure

Collars, skirts, caps: all classes of materials with modifications

CAPPING OF THE OCCLUSO-PROXIMO-FACIAL OR LINGUAL CORNERS , POSTS

Protects thinned corners due to over preparation or wide preparation of ovoid teeth

Adds to retention by locking the restoration

A bevel extension added facially or lingually at the corners- added to the preparation in a knife edge or chamfer finish line

Filamentous diamond stone

Contraindicated: Class IV & V materials

POSTS: not used as retention means for final cast restoration

Used for cast core foundation or substructure restoration

GROSSLY ROUGHENING, IRREGULARIZING OR MULTIPLE LEVELLING THE SURFACE

Pulpal floor or occlusal surface: Preserving present irregularities or creating intentional irregularities

More retention & lateral locking

Adequate dimension- leaving bulky tooth structure between them for resistance

Smooth surfaced- with no undercuts, no frail or undermined enamel

Flat, dished up or sloped gingival or pulpal floors: different levels created

Fissure burs, chisels

All types of cast materials

RECIPROCAL RETENTION Placing retention modes at every end of the preparation or parts of the preparation: Basic principle

Every retention mode – opposite retention mode for complete immobilization of the restoration

Otherwise: Substantial stresses in the locked side, especially at the interface

Opposite grooves or internal box to oppose an internal box/ dovetail to oppose a proximal external box etc.

PRECEMENTATION GROOVING OF THE CASTING & THE ADJACENT TOOTH SURFACE/ WALLS

An inverted truncated cone groove cut on one or more sides of the casting & similar groove cut opposite it on the preparation

Sufficient dimension: bulky amount of cementing agent

Sufficient amount of cement mixed & flown into the grooves when cementing the casting

Enhances the retention provided by the cement

Class V cavity preparations: little frictional retention form

ELECTROLYTIC ETCHING OF TOOTH SURFACE OF THE CASTING

Internal/ tooth surface of Class IV cast material : electrolytic etching

Margins & external surface : covered with sticky wax

Electrolytic cell: 0.5 N HNO3 ,Anodic electrode of the casting, Cathode of another non- noble alloy higher in the electromotive force table

Low voltage current passed – selective etching of the casting, dissolution of grain boundaries & less noble elements

Microscopic irregularities similar to acid etching of enamel

10- 15 minutes

ELECTROLYTIC ETCHING OF TOOTH SURFACE OF THE CASTING

Suitable cementing agent – wets irregularities on both casting & tooth surface increase retention

Principal means of retention if microscopic retaining irregularities on the alloy reciprocated to similar ones on the tooth

Tooth preparation: confined to enamel

Several techniques use the phenomenon as a sole retaining device for fixed prosthesis & cast restorations based on few principles:

* The luting bonding agent is always a composite resin

* Tooth should have adequate enamel thickness to be etched by phosphoric acid

* Class IV cast alloy- for better selective etching

ELECTROLYTIC ETCHING OF TOOTH SURFACE OF THE CASTING

* Minimal tooth preparation- requiring only enough reduction to accommodate the metal, with no attempt to create mortise, cone or box- shaped preparations

* Cast alloy should be in contact with the maximum surface area of available enamel

* If the casting is an attachment for a fixed prosthesis, the pontic should be an indexing tooth for lateral movement of the mandible

Failures: cohesive in the luting agent, so a minimum thickness should be used

ELECTROLYTIC ETCHING OF TOOTH SURFACE OF THE CASTING

- The tooth surface is reduced to allow 1- 1.1 mm cast thickness

- Casting is fabricated in the conventional way

- The casting is tried in the mouth

- The internal (tooth) surface of the casting is etched

- The involved enamel surface is etched

- The composite is flowed into both the enamel and the casting and allowed to cue under pressure

- Excess composite is flaked off

- The exposed surface of the composite resin is polished

Similar procedure with cast ceramic restorations: etching with HF 5-10% for 15 minutes

OTHER PREPARATION FEATURES TO MINIMISE MECHANICAL PROBLEMS

All line and point angles should be definite, but not angular

- easily reproduced in casting

- avoid stress concentration

- substantial roundness: Class V materials

Axial wall slant towards the pulpal floor + Rounding of the axiopulpal line angle: reduce stresses at the isthmus area

Reduction of tooth structure should follow the original anatomy of the tooth

- create even reduction

- minimum tooth involvement

- even physiologic distribution of forces

OTHER PREPARATION FEATURES TO MINIMISE MECHANICAL PROBLEMS

Maximum reduction – occluding surfaces

- average 1mm cleared for metallic casting in inclined planes of cusps

- 1.5 mm for cast ceramics

- reduction in concave form: to accommodate bulk of casting where stresses are maximum

Internal parts of the preparation- mortised to preserve retention & resistance features

- boxed up portion occupy maximum dimensions of the cavity preparation

- necessitates the walls be prepared in different planes

- internal planes be fixed at almost right angles with the adjacent walls

DESIGNS OF PREPARATIONS FOR CAST RESTORATIONS

5 general designs:

1. Inlays

2. Onlays

3. Cast restorations with surface extensions

4. Pin-lays

5. Full veneer cast or cast based restorations

INLAY INDICATIONS:

Width of the cavity does not exceed one- third the intercuspal distance

Strong, self- resistant cusps remain

Minimal or no occlusal facets, and if present, are confined to the occlusal surfaces

The tooth is not to be an abutment for a fixed or removable prosthesis

Occlusion or occluding surfaces are not to be changed by restorative procedure

INLAY- Class I, II & III materials GENERAL SHAPE:

Occlusal portion: dove- tailed

Proximal portion: boxed

INLAY- Class I, II & III materials LOCATION OF MARGINS:

OCCLUSAL PORTION-

Facial, lingual & sometimes proximal margins :inclined planes of the corresponding cusps/ triangular ridges/ marginal ridges

Bucco-lingual width does not exceed 1/3rd intercuspal distance

The most peripheral margins: away from the contact with the opposing tooth surfaces

Wear facets, supplementary grooves, areas of decalcification, any defects in the adjacent parts of the occlusal surface- beveled portion of the preparation

INLAY- Class I, II & III materials PROXIMAL PORTION-

Facial & lingual margins: embrasures

Full length of an explorer passes freely occluso-gingivally

All undermined enamel, surface defects & peripheral marginal undercuts eliminated

Proximal extension increased to improve accessibility, but terminated short of the axial angle of the tooth

Extensions: flare portion & not the wall proper

Gingival margins: extended to include any surface defects & concavities and eradicate marginal undercuts

Extensions: bevels & not wall proper

INLAY- Class I, II & III materials INTERNAL ANATOMY:

Occlusal portion: Facial/ lingual walls and sometimes proximal walls- Wall proper & Occlusal bevel

Wall proper:

Pulpal 2/3rd of the walls

Formed completely of dentin

Taper from each other : 2-50 or parallel

Walls parallel to the long axis of the crown

Right angle/ slightly obtuse angle with the pulpal floor

INLAY- Class I, II & III materials Occlusal bevel:

Long bevel constituting almost one third of the walls

Bevelled outer plane: 30- 45 degrees to the long axis of the crown width of the preparation

- Bevels not needed in very steep cusps- Narrow preparations- Occlusal extension & enamel involvement of wall proper: bevel enamel rods in the inner one third of the inclined planes

Steepness of the cusps

Width of the preparation- Accommodate more bulk of the alloy- Resist increased stresses- Bevels the enamel rods inclined towards the cusps

Direct wax pattern

- More marginal bulk required

Extensions:

Remotely located defects,

supplementary grooves,

decalcifications on occlusal surface

INLAY- Class I, II & III materials

INLAY- Class I, II & III materials Bevel: usually half of the wall proper

Extended : wear facets, decalcifications, occlusal defects, supplementary grooves

Move the margin away from occlusal contacts

Wider & deeper cavities: bevels extended to improve the taper & reduce frictional components for easier material manipulation

INLAY- Class I, II & III materials Pulpal floor:

Flat over most of its extent or at least the peripheral portions

Conventional depth > amalgam for increased length of the surrounding walls

1- 1.5mm from the DEJ

Definite line angle with all the walls except the axial wall- very rounded

INLAY- Class I, II & III materials Axial wall:

Bucco- lingually: Flat or slightly rounded

Gingivo- occlusally: vertical or slightly divergent to the pulpal foor- 5 to 10 degrees

Divergence: taper

Creating bulk: stress concentration areas

Extreme rounded junction with pulpal floor: prevents stress concentration

Ideal depth: 1- 1.5 mm from the DEJ

INLAY- Class I, II & III materials Facial & Lingual walls:

2 or 3 planes

Axial half: Wall proper- completely dentin& meets axial wall at a right angle relationship

Main resistance & retention feature

Proximal half: Primary flare- enamel & dentin with an unchanged 450 to the wall proper

Third plane: Secondary flare- enamel peripherally

Simplify impressions & wax pattern manipulations

Not used if direct wax pattern is to be fabricated

Variable angulation & extent

INLAY- Class I, II & III materials Gingival floor:

Flat in the bucco- lingual direction; slightly obtuse angle with the buccal & lingual walls

2 planes in axio- proximal direction

Axial half: Gingival floor proper

Perfectly flat, formed of dentin & making a right angle/ obtuse angle with the axial wall

Proximal half: Long bevel inclining gingivally

Angulated at 30- 450 to the wall proper

INLAY- Class I, II & III materials

Occlusal bevel & primary or secondary flare proximally

Primary or secondary flares proximally & the gingival bevel

Additional retention means:

Grooves- Facial, lingual or gingival proximally

Internal boxes/ slots- Occlusally

Capping corners of cusps

Rounded

MODIFICATIONS FOR CLASS IV AND SOME CLASS III ALLOYS

More rounded internal line and point angles

Less tapered & more parallel surrounding walls

All circumferential tie constituents hollow ground to improve the capability of these alloys to replicate marginal details during casting

Tooth preparation deeper: axially & pulpally to compensate for poor castability

Extent & angulation of circumferential tie constituents governed similarly as earlier

MODIFICATIONS FOR CLASS V CAST MATERIALS

In addition to the changes for Class IV alloys:

Definitely flat pulpal & axial walls meet surrounding walls in very rounded line angles

No decisive differentiation between surrounding walls & the circumferential tie constituents

Both – exaggerated hollow ground bevels/ very rounded shoulderss

REFERENCES Sturdevant’s Art & Science of Operative Dentistry

Operative Dentistry- Marzouk

Principles and Practice of Operative Dentistry- Charbeneau GT

Cast Restorations- Shillingburg

Fundamentals of Operative Dentistry- Summit