The document discusses principles of tooth preparation for cast restorations. It covers topics such as preparation path, apico-occlusal taper, circumferential tie features for intracoronal and extracoronal preparations, and auxiliary means of retention such as grooves, boxes, and pins. The key goals of preparation design are to provide maximum retention, resistance, and a definitive path of insertion and withdrawal for the restoration. Taper, bevels, flares, and other features are used to achieve an ideal relationship between the casting and tooth for a strong, durable restoration.

1. PRINCIPLES OF
PREPARATION FOR CAST
RESTORATIONS
DEEPTHI P.R.
II YEAR MDS

2. 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

3. 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

4. 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

5. 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- materials inserted & withdrawn from preparation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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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:

17. 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

18. 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

19. 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

20. 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
Disadvantages
Liability of transitional
continuation of a
circumferentia tie with
adjacent bevel ties
Limited burnishability of
marginal cast alloy

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. 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

28. AUXILLARY MEANS OF RETENTION
Compound & complex tooth involvement
Formability of cast restorations: myriad retention & resistance means
Luting cements
Grooves
Reverse bevel
Internal box
External boxes
Slot
Pins
Collar
Skirts
Capping of cusps
Capping of the
marginal ridge
Posts
Gross roughening
Reciprocal
retention
Capping of
occluso- proximo-
facial or lingual
corners
Precementation
grooving
Electrolytic etching

29. 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

30. GROOVES
Completely in dentin
Internal 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 capabilities
Indicated: 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

31. 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

32. 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

33. 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

34. 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

35. INTERNAL BOX
Minimum 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

36. 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

37. 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

38. 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

39. 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

40. 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

41. 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

42. 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.

43. 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

44. 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

45. 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

46. 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

47. 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

48. 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

49. 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

50. 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

51. 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

52. INLAY- Class I, II & III materials
GENERAL SHAPE:
Occlusal portion: dove- tailed
Proximal portion: boxed

53. 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

54. 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

55. 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

56. 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

57. 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

58. 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

59. 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

60. 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

61. 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

62. 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

63. 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

64. 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

65. 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

66. 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