P G Student
Dept. of Conservative Dentistry
Materials for cast restorations
Indications & Contraindications
Advantages and disadvantages
Principles of Cavity design for Cast inlay
Tooth preparation for Inlay Class II cast
Bevels- Various types and significance.
Variations in proximal margin design.
Tooth Preparations For Cast Restorations
With Surface Extension.
Dr. Phil brook in 1897,was the first to introduce
Inlay in dentistry who gave the concept of forming
an investment around a wax pattern, eliminating the
wax, and filling the resultant mold with a gold alloy.
In 1907 Taggart changed the practice of restorative
dentistry by introducing his technique for cast gold
It was most certainly Taggart who recognized the
significance of cast gold restorations.
METERIALS FOR CAST RESTORATIONS
Until recently gold-based alloys have been the only
ones used for cast dental restorations. The ADA
sp#5 still requires 75% of gold-plus- platinum group
metals to be present in alloys for cast restorations
According to Sturdevant there are 4 distinct groups of
The traditional high gold alloys.
Low gold alloys.
Base metal alloys.
ACCORDING TO MARZOUK:
1. Class-I: Gold and platinum group based alloys.
2. Class-II: Low gold alloys (gold content < 50%).
3. Class-III: Non-gold palladium based alloys.
4. Class-IV: Nickel-chromium based alloys.
5. Castable moldable ceramics
CHARACTERISTICS OF CAST GOLD
According to ADA sp#5 the alloys are characterized
Type I-soft gold alloys
Type II-medium hard alloys
Type III-hard alloys
Type IV-extra hard alloys
According to ADA specification No.5:
1. Type-I (Soft): For restorations subject to very
slight stress such as inlays.
2. Type-II (Medium): For restorations subject to
moderate stress such as onlays.
3. Type-III (Hard): For high-stress situations,
including onlays, crowns, thick veneer crowns
and short-span fixed partial dentures.
4. Type-IV (Extra hard): For extremely high stress
states, such as endodontic posts and cores, thin
veneer crowns, long span fixed partial dentures
and removable partial dentures.
Alloy Type Total noble metal content
High Noble (HN) Contains 40 wt.% Au +
60 wt.% of noble metal
elements (Au + Ir + Os + Pd
+ Rh + Ru).
Noble metal (N) Contains 25 wt.% of the
noble metal elements.
Predominantly base metal Contains < 25 wt.% of the
(PB) noble metal elements.
Type Au Cu Ag Pd
I 83% 6 10 0.5 Balance
II 77% 7 14 1 Balance
III 75% 9 11 3.5 Balance
IV 69% 10 12.5 3.5 Balance
INGREDIENTS OF NOBLE METAL ALLOYS:
The most important element in dental gold alloys is
gold, copper, silver, platinum metals and zinc.
Gold is primarily responsible for deformability
Ranks lowest in strength.
Characteristic yellow color with a strong metallic
Density (Sp gravity) 19.3 g/cm3.
Fusion temperature – 1063o C.
2. Platinum: May be added to
1. Strengthen the alloy.
2. Raise the fusion point (1755).
3. Import rigidity, nobility and hardness.
4. Whiten the alloy.
5. Specific gravity-- 21.37.
6. Also malleable and ductile.
Serves the same functions but is much less
expensive than platinum.
4. Iridium, Ruthenium and Rhodium:
Trace amounts of these metals are added as
“Grain Refiners” melting point .
As little as 0.005% is sufficient to refine the grain
size. Grain refiners produce smaller grains.
Fine-grained alloys are generally stronger and
more ductile than coarse-grained alloys.
Indium can also act as a scavenger for the alloy
during casting procedure. Also serve to increase
the tarnish and corrosion resistance.
It contributes to the strength and hardness of the
alloy. Although it mimics gold in its deformability
effect, it adversely affects the malleability and it
lowers tarnish resistance.
Food containing sulfur compounds, cause severe
tarnish on silver.
Silver serves to balance the red color given by
Adding small amounts of palladium to silver
containing alloys prevents the rapid corrosion of
such alloys in the oral environment
Contributes strength and hardness, but
decreases the malleability of the alloy, i.e., it
decreases the tarnish and corrosion resistance .
The content should not exceed 16%. Gives the
alloy reddish appearance. Lowers the fusion
7. Zinc: (Present only in low percentages, around
Acts as a deoxidizer and reduces the oxygen
content (because O2 released during
solidification results in porosity).
Dens Yield -lus Rate
Type of Melting Hardne
-ity stren of of
cast Elongation range ss
(gm/ gth elasti tarni
materials (o F) (VHN)
cm3) (MPa) city( sh
Class I 20-25% 943-960 16.6 103 80 10-12 0%
Class II 20% 924-960 15.9 186 101 12 2-3%
Class III 15-18% 924-960 15.5 207 121
ClassIV 3-11% 834-916 12.8 241 138 30 0%
ClassV 0% 10.6 262 143 60 0%
Endodontically treated teeth
Teeth at risk for fracture
Dental rehabilitation with cast metal alloys
Diastema closure and occlusal plane correction
Correction of occlusion
Wide open contacts and occlusal plane correction
Adjunct to periodontal therapy to correct tooth
anamolies predisposing to plaque accumulation
Sub gingival lesions
Physiologically young dentition with large pulp
chambers are poor candidates for cast restoration
Developing and deciduous teeth
High plaque / caries indices.
Control of contours & contacts
Extensive tooth preparation
Cemented restoration, discrepancy and micro
Abrasive and splitting force on natural teeth
Number of appointments and higher chair time
Cost and Temporary restoration requirement
PRINCIPLES OF CAVITY DESIGN FOR CAST
Basic differences between Amalgam and Cast
restoration preparation are
Bevels- occlusal and gingival
For maximum retention in a cast restoration
opposing walls and opposing axial surfaces of a
tooth preparation should be perfectly parallel to
Taper should be an average of 2-5 degree from
path of preparation. It can be decreased or
increased according to the length of the preparation
wall and/or axial surface, surface involvement and
internal anatomy in the preparations.
Extension of opposing walls, which diverge toward
the occlusal form a convergent angle. A bisection of
this angle positions the “line of draw” which is
perpendicular to the pulpal floor.
The preparation should have a single insertion
(draw) path, opposite to the direction of the occlusal
loading. This path is usually parallel to the long axis
of the tooth. So that the completed cavity will have
draft (no under cut).
PREPARATION FEATURES OF THE
The peripheral margin anatomy of the preparation
is called circumferential tie.
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
Bevels are the flexible extensions of a cavity
preparation, allowing the inclusion of surface
defects, supplementary grooves, or other areas on
the tooth surface.
Require minimum tooth involvement
Bevels create obtuse-angled tooth structure i.e. the
strongest configuration and acute-angled marginal
alloy i.e. burnish able. Thus makes it possible to
decrease the cement line.
A lap, sliding fit is produced at gingival margin.
It results in 30-degree metal that is burnish able.
Weak enamel is removed.
SIX TYPES OF BEVELS
Partial Bevel: involves part of enamel wall, not
exceeding 2/3rds its dimension. It is not used in
cast restorations, except to trim weak enamel rods.
Short Bevel: includes entire enamel wall, but not
dentin, it is used with class-I alloys specially for
type 1 & 2 (Gold platinum based alloys).
Long Bevel: includes all enamel & up to ½ of the
dentinal wall, its major advantage is that it
preserves the internal boxed-up resistance. , most
frequently used for the 1st 3 classes of cast
Full Bevel: Includes all of the dentinal and enamel walls
of the cavity wall or floor. Its use should be avoided
except in cases where it is impossible to use any other
form of bevel
Counter Bevel: when capping cusps to protect and
support these, this type of bevel is used, opposite to an
axial cavity wall, on the facial or lingual surface of the
Hollow ground bevel (concave)- All the types of bevels
are in the form of a flat plane, but any of them especially
that last three can be prepared in a concave form.
PRINCIPLES OF CAVITY DESIGN FOR
CAST INLAY RESTORATIONS
An Inlay is defined as a restoration which has been
constructed out of the mouth from gold, porcelain or
other metal and then cemented into the prepared
cavity of the tooth.
The class-II inlay involves the occlusal and
proximal surfaces of a posterior tooth and may cap
one or more cusps but not all of the cusps.
The class-II onlay involves the proximal surfaces of
a posterior tooth and caps all of the cusps.
TOOTH PREPARATIONS FOR CLASS II
CAST METAL INLAYS
Resistance and Retention form
Removal of infected caries and pulpal protection.
Preparation of bevels and flares
Outline form for a DO preparation
Carbide burs for preparation
Initial entry is made in the central fossa/pit with a
tapered fissure bur no.271 to establish the pulpal
floor (punch cut) to a depth of 1.5mm.
The depth is determined by the extent of existing
carious lesions or restorations or the need for
Long axis of the bur should be parallel with long axis of
The occlusal outline is
extended mesiodistally along
the central groove and
stopped just short of the
marginal ridge. The bur is
kept in the vertical position in
the long axis of the tooth
through-out the preparation
so that its taper provides the
3 to 5-degree divergence to
the facial and lingual walls
(total divergence of 6 to 10
PRIMARY RESISTANCE FORM
Use of box shape
Preservation of cusps and marginal
Slight rounding of internal line angles
Capping weakened cusps
Adequate thickness of restorative
Removing the remaining infected dentin with
no. 2 or 4 round bur
Insertion of suitable base and completed base.
PREPARATION OF BEVELS AND FLARES
The slender flame shaped fine-grit diamond is used
to bevel the occlusal and gingival margins and to
apply the secondary flare on the proximal-facial and
It will result in 30-400 marginal metal & 140-1500
Placement of retraction cord
facilitates bevelling gingival margin
For the facial and lingual proximal walls in an inlay
cavity preparation for castings flares are used, which
are the flat or concave peripheral portions of the facial
and lingual walls
There are 2 types of flares
The primary flare
The secondary flare
The primary flare:
Is the conventional and basic part of the cavity
facially and lingually for an intra coronal preparation.
It is very similar to a long bevel formed of enamel and
part of dentin on the facial or lingual wall. Primary
flares also have a special angulation i.e., 450 to the
inner dentinal wall proper.
Functions and indications –
These design features perform the same function
They can bring the facial and lingual margins of the
cavity preparation to cleansable finishable areas.
They are indicated for any facial or lingual proximal
wall of an intracoronal cavity preparation.
It is almost always a flat plane super imposed
peripherally to a primary flare. It is usually prepared
solely in enamel. Unlike primary flares, secondary
flares may have different angulations, involvement
and extent depending on their function
Functions and indications of secondary flare-
Lesions with wide bucco-lingual extensions
Contact areas too broad
Extension gingivally to extend root surface lesion
When the occlusal outline is extended up the cusp
slopes more than half the distance from primary
groove, capping the cusp should be considered.
If it is extended two thirds or more, capping is
Introduced by Dr.G.V Black in which the proximal
cavities are prepared box shaped with buccal and
lingual walls and a definite gingival floor.
It has its own resistance and retention form.
Direct wax pattern can be made.
The outline form of the proximal surface can be
made on all types of teeth.
Minimum display of metal.
It involves removal of lots of tooth structure.
Clinically it is time consuming.
Narrow bevels leave a sharp edge and an undercut
gingivally , which cannot be satisfactorily
While taking impression distortions and breaking of
wax pattern occurs.
This form of cavity is modified so that the proximal
surface is flat without definite side walls. This is
slice preparation which depends for its retention
mainly on the occlusal key, channels or locks cut in
the axial wall.
Historically ,a slice referred to the placement of
extra coronal taper using a disk of adequate
diameter to contact nearly the entire proximal
As abutment in bridge work
Small carious lesion only on the middle of the
To improve retention form.
Teeth with proximal undercuts can be eliminated
which facilitates taking impression.
Advocated for quadrant work where proximal
outline form can be rapidly developed.
For indirect wax pattern technique.
Less tooth structure is sacrificed.
Quicker and easier.
Well protected enamel margins.
Increases resistance and retention form by
exposing a larger amount of tissue surface to the
frictional grasp of the restoration.
Thoma(1951)pointed out that it displays
unnecessary amount of gold.
Reduced retention form.
Direct wax pattern cannot be made as
distinguishing between the margins is difficult.
The margins of metal which we’ll get are very thin
which can get distorted.
disking of the proximal
surface to establish the
buccal and lingual
extent of finish lines
and provide a lap joint
Auxiliary slice preparation-wraps partially around the
proximal line angles, thus providing additional tooth
Resistance form is enhanced.
Provide external retention form.
In view of the shortcomings of box type and slice
type preparations ,Barishman advocates a modified
preparation which may be called the box cum
Modified flare is nothing but a combination of box
and slice preparation taking advantage of the box
preparation and slice preparation.
Minimum disking of the proximal walls is done for
better finishing and polishing
TOOTH PREPARATION WITH SURFACE
Surface extensions are required to include facial or
lingual defects beyond the axial angle of the tooth.
Surface extensions are required to eradicate severe
peripheral Marginal undercuts, which have not been
removed by the maximum angulations and extent of
a secondary flare.
A surface extension is necessary to encompass an
axial angle for reinforcing and supporting reasons.
A surface extensions is needed to add to the
retentive capability of the restoration proximally
especially with shortened facial and lingual walls or
as a reciprocal means of retention
More surface extension is required to fulfil the
objectives of secondary flares in extremely wide
cavities or contact areas
REVERSE SECONDARY FLARES
Can be added to a cavity (tooth) preparation in lieu
of a secondary flare
The reverse secondary flare is in the form a partial
bevel. It involves only enamel with its maximum
depth at its junction with the main cavity
preparation. In ends on the facial or lingual surface
with a knife edge finishing line, and its extent
should not exceed the height of contour of the facial
or lingual surface in the mesio-distal direction nor
should it include the tip of the cusp.
This is a more extensive surface extension than the
reverse secondary flare also superimposed on the
basic intracoronal inlay or onlay cavity preparation
facially and or lingually
Skirting is required to involve defects with more
dimensions (especially depth) than those that can
be involve in a reverse secondary flare
A skirt is required to import resistance and retention
on a cast restoration in lieu of a missing or
shortened opposing facial or lingual walls.
Skirting is necessary when the contact areas and
contour of the proximal surface are to be changed
Skirts are essential facially and lingually for tilted
teeth in order to restore the occlusal plane.
This type of surface extension is the most involving
surface wise and depth wise.
They are two types
a) Cuspal collars
b) Tooth collars
Cuspal collars which involve the facial or lingual
surface of one cusp only in a multi-cusped tooth.
Tooth collars involve the entire facial or lingual
surfaces of the tooth.
They help in retention and resistance when an
entire cusp is lost prior to the tooth preparation or
when it is necessary to remove if due to excessive
They help retention in shortened teeth.
They help resistance and to enhance support for
tooth that is endodontically treated.
Cast restorations form an integral link in the dental
restorative chain. They are an excellent choice in
many demanding situations. Understanding the
principles of tooth preparations and the intricacies of
cast restorations will enable the dentist to optimally
utilize this excellent option when the clinical situation
Art and science of operative dentistry-Sturdevant
Principles and practice Operative Dentistry-
Fundamentals of operative dentistry-Marzouk
Atlas of inlays, onlays, crown and bridges-
Inlays Crowns & Bridges-Cowell and Curson
Textbook of Operative Dentistry-Vimal Sikri