Inlays and onlays / implant dentistry course/ implant dentistry course

Contents
 Introduction
 Definitions
 Cast Metal Restorations
 Indications and Contraindications
 Advantages and Disadvantages
 Tooth Preparation
 Restoration
 Onlays

 Tooth-Coloured Restorations
 Indirect Composites
 Ceramic Restorations
 Restoration
 Repair of restorations
 CAD-CAM based restorations
 Inlay retained Bridges
 Strength and Longevity of Inlays and Onlays
 Review of Literature

 Sometimes, a tooth is treatment planned to be
restored with an intracoronal restoration, but the
decay or fracture is so extensive that a direct
restoration, such as amalgam or composite, would
compromise the structural integrity of the restored
tooth by possibly undermining the remaining tooth
structure or providing substandard opposition to
occlusal forces.
 In such situations, an indirect gold or porcelain inlay
restoration may be indicated.
 When an inlay is used, the tooth-to-restoration
margin may be finished and polished to such a
super-fine line of contact that recurrent decay will
be impossible.

 It is for this reason that some dentists recommend
inlays as the restoration of choice for pretty much any
and all filling situations.While these restorations
might be ten times the price of direct restorations,
the superiority of an inlay as a restoration in terms of
resistance to occlusal forces, protection against
recurrent decay, precision of fabrication, marginal
integrity, proper contouring for gingival (tissue)
health, ease of cleansing and many other aspects of
restorative quality offers an excellent alternative to
the direct restoration. For this reason, some patients
request inlay restorations so they can benefit from its
wide range of advantages even when an amalgam or
composite will suffice.The only true disadvantage of
an inlay is the higher cost.

 Additionally, when decay or fracture incorporate
areas of a tooth that make amalgam or composite
restorations essentially inadequate, such as
cuspal fracture or remaining tooth structure that
undermines perimeter walls of a tooth, an onlay
might be indicated. Similar to an inlay, an onlay is
an indirect restoration which incorporates a cusp
or cusps by covering or onlaying the missing
cusps.
 All of the benefits of an inlay are present in the
onlay restoration.The onlay allows for
conservation of tooth structure when the only
other alternative is to totally eliminate cusps and
perimeter walls for restoration with a crown.

 Just as inlays, onlays are fabricated outside of the
mouth and are typically made out of gold or
porcelain. Gold restorations have been around for
many years and have an excellent track record.
 In recent years, newer types of porcelains have
been developed that seem to rival the longevity
of the gold. Either way, if the onlay or inlay is
made in a dental laboratory, a temporary is
fabricated while the restoration is custom made
for the patient. A return visit is then required to
deliver the final prosthesis. Inlays and onlays may
also be fabricated out of porcelain and delivered
the same day utilizing techniques and
technologies relating to CAD/CAM Dentistry.

Definitions
 Inlay
A fixed intracoronal restoration; a dental
restoration made outside of a tooth to
correspond to the form of the prepared
cavity, which is then luted into the tooth.

 Onlay
A restoration that restores one or more
cusps and adjoining occlusal surfaces or the
entire occlusal surface and is retained by
mechanical or adhesive means.

 These restorations are versatile and are
especially applicable to Class II onlay
preparations.
 Class II inlay involves the occlusal and
proximal surfaces of a posterior tooth and
may cap one or more but not all the cusps.
 The Class II onlay involves the proximal
surfaces of the tooth and caps all of the
cusps.

Materials Used
 Casting alloys used  advantage  high
tensile and compressive forces  valuble in
restorations to rebuild most or entire occlusal
surface.
 Four distinct groups of alloys are used
currently:
 High gold alloys
 Low-gold alloys
 Pallidium-silver alloys
 Base Metal Alloys

 The alternatives to high gold restorations
have required modifications of technique or
acceptance of reduced performance, most
commonly in regard to decreased tarnish
resistance and decreased burnishability.

History of Casting Alloys
 In 1907,Taggart introduced the lost wax
technique for the fabrication of cast inlay
restorations in dentistry.
 In 1950, resin veneers were developed for gold
alloys.
 In 1959, Porcelain Fused to MetalTechnique was
introduced.
 In 1971, Nickel based alloys as alternative to gold
alloys.
 1980s saw the introduction of All Ceramic
Restorations.

Mechanical Properties of
Dental Casting Alloys
Alloy type Description Use
I Soft Some inlays
II Medium Inlays and Onlays
III Hard Onlays, Crowns,Thick
Veneer Crowns, Short
span FPDs
IV Extra-hard ThinVeneers Crowns,
Long span FPDs, CPDs
1997/2002 ADA no. 5

 Classification according to composition:
Noble Metal
Content wt%
Gold Content
wt%
High Noble 60 40
Noble At least 25 -
Predominantly
Base metal
Less than 25 -
1984

Indications
 Large Restorations
 Better strength
 Control of contours and contacts
 Better alternative to a crown to teeth that have
been greatly weakened by caries or by a large
failing restoration, but facial and lingual surfaces
are relatively unaffected by the disease/injury.
 For such a weakened teeth, the superior physical
properties of the casting alloys are desirable to
withstand occlusal loads placed on the
restorations.

 An onlay can be designed to distribute occlusal loads
over the tooth in such a manner that decreases the
chances of fracture of the tooth in the future.
 Maintaining facial and lingual enamel/cementum is
conducive to maintaining the health of contiguous
soft tissue.

 Endodontically treated teeth
 Molars and Premolars with endodontic treatment
can be restored with a cast metal onlay
 Teeth at risk for fracture
 Teeth with extensive restorations, Fracture lines in
enamel and dentin must be recognised as
cleavage planes for future tooth fracture.

 Dental rehabilitation with cast metal alloys
 When cast metal restorations have already been used
to restore adjacent or opposite teeth, the continued
use of the same metal to avoid electrical or corrosive
activity that may occur if the dissimilar metals are
used.
 Diastema Closure and Occlusal plane correction
 Indicated when extension of mesiodistal dimension of
tooth is necessary.
 Cast onlays may also be used to correct the occlusal
plane of a slightly tilted tooth.

 Removable Prosthodontic Abutment
 Teeth that are to serve as abutments for a
removable partial denture can be restored with a
cast metal restoration.
 Advantages:
1. Superior physical properties allow it to
withstand the forces imparted by the partial
denture.
2. The rest seats, guiding planes and other aspects
of contour relating to the RPD are better
controlled when the indirect technique is used.

Contraindications
 High Caries rate
 Facial and Lingual tooth surface must be free of
caries or previous restorations.
 If present, the tooth must be restored with a Full
crown.
 Young patients
 Amalgam or Composites are the restorative
material of choice for Class I and II restorations
unless the tooth is severely broken down or
endodontically restored.

 Esthetics
 Their use is restricted to the tooth surfaces that
are not visible at conversational distance.
 Small restorations
 Amalgam and Composites serve as a better
option.

Advantages
 Strength
 Biocompatibility
 Low wear
 Control of Contours and Contacts

Disadvantages
 Number of Appointments and More Chair time
 Provisionalisation is required
 Costs
 Technique sensitive
 Splitting forces

Preoperative Considerations
 Occlusion
 Occlusal contacts must be evalauted
 It must be decided if existing occlusal relationships
can be improved with a cast metal restoration
 Evaluation at Maximum Intercuspation, and also
during eccentric movements
 The pattern of occlusal contacts influences the
preparation design, the selection of interocclusal
records, and the type of articulator.

 Anaesthesia
 Eliminates pain, Reduces Salivation
 Considerations forTemporary restorations
 An index can be fabricated preoperatively using
elastomeric impression material or alginate.

Tooth Preparations for Cast
Metal Restorations

Principles of Cavity
Preparation
 For inlay work the dual objectives in cavity
preparation are to remove the caries and
shape the cavity for an effective restoration.
Factors governing a good inlay preparation:
 Caries:
 The final outline of the cavity depends on the
extent of the carious lesion.
 Where it is minimal an initial penetration is made
just into dentine and the cavity is extended at this
optimal depth to the classic outline.

 The outline is decided by the class of the cavity and
the need to remove adjacent stagnation areas on the
tooth surface.
 A larger carious lesion will have caused some obvious
cavitation due to enamel breakdown.The first stage
here is to remove undermined enamel in order to
obtain access to the lesion. Carious enamel at the DE
junction is removed next. Further undermined
enamel is removed next and any remaining fissures
are included in the cavity outline.

 Retention and Resistance:
 Resistance to occlusal stresses is generally obtained
by providing flat pulpal and gingival floors of the
cavity, if necessary by the addition of a cement base
over the pulp.
 Resistance to lateral stresses is provided by an
occlusal lock and by axial walls.
 For good retention, an inlay must have a single path
of insertion into its cavity in a direction which is
usually in line with the main occlusal load,
masticatory forces will then tend to seat the inlay
more securely into its cavity.

 This single path of insertion is achieved by near
parellelism of the cavity walls so that the inlay can
be displaced only along the path of its insertion.
The friction provided between the near parallel
walls and the inlay when its cemented will prevent
this displacement.
 Cavo-surface Angles
 The marginal integrity of an inlay depends on the
existence of a well defined cavo surface angle.
They are usual cut in enamel and must be smooth
and finished with great care, crumbling of the
margin due to minor irregularities may cause
recurrent caries.

 The margin must also allow for
burnishing of the margins of the
restoration if a gold restoration is
being planned.
 Minimum Cavo surface angle which
permits thin enough gold capable of
being burnished is about 135°.
 This special preparation is known as
bevelling. They usually extend half the
thickness in enamel except cervically
where the enamel is thinner and a full
thickness of enamel is bevelled.

Class I Cavity
 Inlays for this type of cavity have a very limited
application, but may be considered where
opposing cast restorations are already present
or are being planned.
 Generally inlays are not indicated for Class I
cavities, Amalgam or composites provide
excellent restorative option.
 A very large Class I cavity requiring cuspal
coverage may be restored with an inlay if the
operator is satisfied that the caries activity is low
enough.

Cavity Preparation
 Step 1: Access: the tooth is
penetrated to just within the dentine,
using aTC bur
 Step 2: Extension:The fissures are
removed by extending at the
optimum depth, using a tapered
fissure bur.This instrument if used
correctly, produces the correct taper
with a flat floor.
 Step 3: Caries Removal and Lining:
Remaining caries is excavated and
the resulting cavity lined to produce a
flat floor just within dentine.

 Step 4: Finishing: Sharp burs
running at low speed is
recommended for the
intracoronal details and
Bladeless or 40 bladedTC burs
used at ultra high speed are
recommended for the cavo-
surface angles.
 Bevelling is not necessary when
the cavo surface angle is greater
than 135°. But when the angle is
less than 135° the margin must
be bevelled.

 A direct wax pattern is usually indicated for
this type of a cavity.
 Type II wax (Hard type) is used.

Class II Cavity
 Proximal restorations are by far the most
common restorations in Restorative
dentistry.
 A Class II restoration may vary from a
relatively conservative MO/DO Box
preparation to Mesio-occluso-Distal
Restorations to Cusp capping.

Box Preparation
 This type of a preparation consists of an
occlusal part in dovetail form and an
proximal box.
The Steps in preparation are:
 Step 1: Access:A smallTC bur is used to
cut just within the marginal ridge and to
penetrate along the enamel-dentine
junction to the proximal caries.
 Step 2: Extension of the Proximal box:
The proximal cut is extended to gingival
level with a fine, tapered fissure bur at
ultra speed. Sweeping cuts are made
bucco-lingually to outline the lateral
extent. Undermined enamel is removed
using a chisel or a hatchet.

Tapered fissure bur is then
used to remove irregularities
on the proximal box and
flatten the gingival floor.
 Step 3: Outline of the occlusal
form:Tapered fissure bur is
used to outline the occlusal
part of the preparation.The
occlusal outline is similar to
that of a Class I cavity.

 Step 4: Finishing the Proximal
Box:The Proximal box is
completed using a fine
abrasive disc or a chisel to
plane its vertical walls and to
sharpen its line angles.
To achieve optimum cavo-
surface margin, the buccal and
lingual walls may be flared
using fine abrasive discs.
Gingival enamel is finished
using aTC finishing bur.

 Step 5: Gingival Lock: a
groove may be cut into
the dentine of the gingival
floor using a reverse GMT.
This acts as a stop. But
this feature is not
essential.
 Step 6: Finishing the
Occlusal Dovetail:The cut
enamel surface of the
dovetail is smoothened
with a plain cut bur.
 Step 7: Caries Removal
and Lining: Any caries
remaining is removed and
base is applied, deep
excavations need a
protective sub-base.

Extensive Proximal Cavities
 In case of extensive Proximal cavities, the
approach to cavity preparation is slightly
modified,
 Here, the undermined enamel and marginal
ridge are removed first using a chisel, followed
by initial minimal extension of the proximal
and occlusal parts of the cavity followed by
the removal of all the caries and final
extension.

MOD cavities
 This type of cavity with its combined
mesial and distal parts is more difficult
to prepare because of the extra
surfaces which must be kept to a
common path of withdrawal.
 In case of an unaffected, strong
oblique ridge, a separate MO and DO
cavities are prepared and restored.
 The distoocclusolingual restoration
that caps the distolingual cusp is
preferable to the DO restoration
because it protects the miniature
distolingual cusp from subsequent
fracture.

Modification for Esthetics
 For esthetic reasons, minimum flare is desired for
the mesiofacial proximal wall in the maxillary
premolars and first molars in class II cast metal
preparations.
 The mesiofacial margin is minimally extended
facially of contact to such a position that the
margin is barely visible from a facial viewing
position.
 To accomplish this, the secondary flare is omitted,
and the wall and margin are developed with a
chisel or enamel hatchet and final smoothing with
a fine-grit paper disc, or a narrow diamond or bur
when access permits.

For abutment teeth
 Extending the facial, lingual, and gingival
margins may be indicated on the proximal
surfaces of abutments for RPDs to increase
the surface area for development of guiding
planes.
 In addition, the occlusal outline form must be
wide enough faciolingually to accommodate
any contemplated rest preparations without
involving the margins of the restoration.
These extensions may be accomplished by
simply increasing the width of the bevels

Extension gingivally to
include root-surface lesions
 The gingival extension should be accomplished
primarily by lengthening the gingival bevel,
especially when preparing a tooth that has a
longer clinical crown than normal as a result of
gingival recession.
 It is necessary to only slightly extend the gingival
floor, and although the axial wall consequently
must be moved pulpally, this should be minimal.
 Extending the preparation gingivally without
these modifications would result in a dangerous
encroachment of the axial wall on the pulp

Capping cusps
 The facial and lingual margins on
the occlusal surface frequently
must be extended toward the cusp
tips to the extent of existing
restorative materials and to
uncover caries.
 Undermined occlusal enamel
should be removed because it is
weak. Moreover, removing such
enamel provides access for proper
excavation of caries.

 When the occlusal outline is extended up the
cusp slopes more than half the distance from
any primary occlusal groove (central, facial, or
lingual) to the cusp tip, capping the cusp
should be considered.
 If the preparation outline is extended two
thirds of this distance or more, capping the
cusp protects the weak, underlying cuspal
structure from fracture due to the
masticatory forces and also removes the
occlusal margin from a region subjected to
heavy stress and wear.

 Cusp reduction appreciably decreases
retention form because of decreasing the
height of the vertical walls; consequently,
proximal retention grooves usually are
recommended.
 It may be necessary to increase retention
form by extending facial and lingual groove
regions of the respective surfaces, or by collar
and skirt.
 These additional retention features also
provide the desired resistance form against
forces tending to split the tooth.

 A full crown is indicated if both the lingual
and facial smooth surfaces are defective,
especially if the tooth is a second or third
molar.
 When only a portion of the facial smooth
surface is carious and the lingual surfaces of
the teeth are conspicuously free of caries, an
MOD inlay or onlay with a lingual groove
extension is chosen over the crown because
the former is more favorable to the health of
the gingival tissues and more conservative in
the removal of tooth structure.

 If distofacial defect is more extensive and
deeper into the tooth a gingival shoulder
extending from the distal gingival floor
around to include the affected facial surface
is recommended.This shoulder partially
provides the desired resistance form.

Class III Cavities
 Inlays for simple Class III cavities are not
generally recommended although exceptionally
one with a small palatal extension may be
suitable for a denture rest.
 An important indication for a class III inlay is the
distopalatal restoration used as a minor retainer
in an upper canine or central incisor for a fixed-
movable bridge. Unfortunately, this design
decreases the retention of the inlay and
additional retention is usually necessary.This is
obtained by using pin placed within the palatal
dovetail at the farthest point from the proximal
box.

Tooth Preparation
 The lingual outline is
formed using aTC Bur.
 Lingual dovetail or lock is
used to give resistance
form.
 It should be 1 mm deep.

 Continue the cut along the
midline of the cingulum to 1
mm of the gingiva. Second cut
should extend distally close to
the lesion being restored on
the distal aspect.
 A reverse L shape outline is
formed.
 Proximal box is prepared
without preparing the facial
enamel, to avoid unesthetic
display of metal, and also to
conserve tooth structure.

 Smoothen the axial wall
of the box.
 Proximal flares and
bevels are given using a
flame shaped diamond
bur.
 The entire finish line
must then be finished
using a flameTC
finishing bur.

Class V Cavities
 There are 2 distinct lesions at the cervical margin
of the buccal or lingual surfcare of a tooth which
may need restorations. One begins as caries of
the enamel at the gingival third of the crown and
the other is a cavity of cementum and dentin at
the cervical margin of a tooth with gingival
recession and is due to abrasion forming a cavity
with an overhang of sound enamel.
 With the advent of restorative materials like GIC,
inlays are not a choice of treatment for most of
these patients.

Tooth Preparation
 Outline is made using aTC bus
 The preparation should be 1 mm
deep axially. If there is an
extensive lesion then create a
ledge around the periphery of the
preparation extensions.
 Extend the preparation to the
line angle of the tooth. Keep the
finish line supragingival.

 The occlusal finish line should
extend no farther than the
height of contour.
 Pinholes are drilled using a
0.6mm drill.
 At the mesial and distal
edges of the outline form.

 Bevel is given using the flame
diamond bur
 Place 45 degree bevel around
the periphery of the entire
outline form, approximately
0.5mm in width.
 Finish the preparation with a
plane carbide finishing bur.

Onlay Preparation
 The cast metal onlay restoration spans the gap
between the inlay, which is primarily an
intracoronal restoration, and the full crown, which
is a totally extracoronal restoration. The cast metal
onlay by definition caps all of the cusps of a posterior
tooth and can be designed to help strengthen a tooth
that has been weakened by caries or previous
restorative experiences.
 It can be designed to distribute occlusal loads over
the tooth in a manner that greatly decreases the
chance of future fracture. It is more conservative of
tooth structure than the full crown preparation and
its supragingival margins, when possible, are less
irritating to the gingiva.

 Usually an onlay diagnosis is made
preoperatively because of the tooth's status.
However, sometimes the diagnosis is
deferred until extension of the occlusal step
of an inlay preparation facially and lingually
to the limits of the carious lesion
demonstrates that cusp reduction is
mandatory.

Occlusal Considerations
 Clinicians have linked marginal failures to
weakened cusps and preparation walls bending
away from the restoration under stress
 Isthmus width and depth have also been
recognised as contributing factors
 As long as the tooth is intact it has structural
integrity, when a tooth preparation is done
tooth is weakened and is prone to fracture.
 Premolar-11-52% less fracture resistance when
class I isthmus is cut into oclusal surface
 17-57% less strength when it has proximo-
occlusal preparation

 Only 36-61% of its strength left when MOD
preparation is done so chances of fracture at
the isthmus is more

 Cusp have a mechanical
height that is equal to the
anatomical height
measured from the cusp
tip to the level of central
groove
 In MOD mechanical
length is greatly
increased –distance from
cusp tip to gingival
extension of Preparation.
This causes elongation of
lever arm and hence in
small tooth can cause
fracture

• Inlay has a tendency to wedge the cusps
apart particularly when there is a wide
isthmus.
• Occlusal forces applied produces stress along
the side of the restoration and at its base

 This situation in could lead to
fracture of the tooth
 Onlay will distribute the forces
evenly over a wide area
reducing the potential for
breakage
 The wedging effect produced
by inlays were shown by
photoelastic stress analysis by
Fisher et al.Inlay produced
stress concentration at the
walls of the isthmus and the
line angles

Tooth Preparation
Initial Preparation
 Occlusal reduction: tapered fissure carbide and
round-end diamond bur used

 1.5 mm clearance on functional cusps
 1.0 mm clearance for nonfunctional cusp
 Reduction should follow the general topography
of the occlusal surface.

 Functional Cusp
Bevel is given

 Occlusal Shoulder
on the functional
cusp side
 Provides for
greater bulk of
metal on functional
cusp
 Increased
resistance
 Reinforced margin
(more durable)

 Occlusal isthmus
preparation
 Flat end tapered
fissure carbide bur
used.
 Isthmus is made now
if not prepared earlier
while removing the
existing restoration.
 Bur held parallel to
long axis of the tooth.

 Prepare pulpal floor
along the central
groove extend
mesially and distally,
facially and lingually
• Should be 1.0mm
shallower than the
isthmus in an inlay
because occlusal
surface has been
reduced already

• Isthmus should be ½ to 1/3rd the width
between the facial and lingual cusp tips.
• 2-5 degree taper per wall- (according to
Sturdevant)
 When the wall length or surface involvement
increases, taper increased.
 Taper reduced- when wall is short and need
for retention is more narrow at pulpal surface

 Proximal box
preparation
 Tapered fissure carbide
bur. Mesial and distal
proximal boxes are
prepared to the level of
the gingival crest
 Gingival floor should
be 1mm wide and the
Proximal clearance
should be 0.5mm

 Buccal and Lingual walls
should diverge
occlusally
 Use hatchets/chisels to
plane the facial and
lingual walls and refine
the axiobuccal and
axiolingual line angles
 Shallow (0.3mm)
retention grooves cut in
facioaxial & linguoaxial
line angles with a
carbide bur in dentine
for retention

Final preparation
 Removal of infected carious dentin and defective
restorative materials and pulp protection
 If the proximal boxes and the occlusal step has
been extended properly then any remaining
caries or restorative material should be visible. It
should be removed.
 All the horizontal surfaces i.e., the pulpal floor,
gingival floor and shoulder should be smoothened
using an endcutting bur.

Smoothening of Isthmus, gingival seat and Shoulder

Proximal Flares
 Primary flare and Secondary flare
Primary flare
 part of circumferential tie
 similar to a long bevel
 formed of enamel and part of dentin
 Placed on facial and lingual proximal wall.
 have 45o angulation to inner dentinal wall
proper
 places proximal margins in cleansable
finishable areas.

Secondary Flare
 Is a flat plane superimposed on a primary
flare usually prepared solely in enamel but
may involve dentin also
 Places margins in more cleansable
finishable areas
 Results in 40 degrees marginal metal.
 A more blunted and stronger enamel
margin is produced
 May have different angulations,
involvement & extent

Indications of Secondary Flare
 Broad contact areas, secondary flare brings
the facial and lingual margins to finishable,
cleansable areas, without sacrificing much
tooth structure.
 In case caries is widely extended in
buccolingual dimension.
 To include surface defects on facial and
lingual aspect beyond the primary flare.
 To overcome undercuts that may be present
at the cervical aspect of the facial and lingual
proximal walls

 Flame shaped
diamond used
 Place the flares on the
proximal box from
within starting with
the tip of the flame
diamond
 A wide enamel
hatchet can also be
used to form the flares

Finishing bevels
 Gingival bevel
 Flame diamond bur used
 0.5mm to 1mm wide
 Placed along the entire
gingival floor of the box
 Should blend with the
flares without forming an
undercut.

 Should blend with the
flares without forming an
undercut.
 Removes unsupported
enamel
 Results in 30 degree
marginal metal that is
easily burnishable.
 A lap sliding fit is
produced at the gingival
margin

Facial and lingual bevels
 Flame diamond used
 0.5mm wide
 Placed on buccal
(maxillary)and lingual
(mandibular) occlusal
surfaces, should be
blended into the flares.
 Bevel should result in 40
degrees marginal metal
 An Occlusal shoulder
bevel is also placed

Additional Retentive features
 Skirt Preparation
 Collar Preparation
 Slot Preparation

Skirt Preparation
 When the proximal portion of a class II
cavity for an onlay is being prepared
and the lingual wall is partially or totally
absent the retention is provided by
skirt preparation of the facial margin
and vice versa
 Recommended when proximal
contours and contacts are to be
extended more than the normal
dimensions
 When splinting posterior teeth
together with onlay.The additional
retension and resistance is very useful
because of the stress on each un

Collar Preparation
 To increase the retention and resistance form
when preparing a weakened tooth for a MOD
onlay capping all the cusps , a facial or lingual
collar or both may be provided
 To reduce the display of metal on the facial
surfaces of the maxillary premolars and the
first molars are usually not prepared for collar.

Slot Preparation
 After cusp reduction the vertical
walls of the occlusal step portion
of the preparation are reduced so
they provide very little retention
form. In such cases necessary
retention can be obtained by
making a slot preparation
 It is indicated in short clinical
crown and in cusps that have been
reduced
 A slot removes more tooth
structure than for a pin but it is
less likely to cause microfractures
in dentin

Restorative techniques
 Interocclusal records:
If the patient has sufficient canine guidance
to provide disocclusion of the posterior teeth,
then the necessary registration of the opposing
teeth can be obtained by (1) making a MI
interocclusal record with commercially available
bite registration pastes or (2) making full-arch
impressions and mounting the casts made from
these impressions on a simple hinge articulator.

 But, Cast metal restorations made with these
simple bite registration techniques often require
adjustments in the mouth to alleviate
interferences during mandibular movements.
 The use of full-arch casts mounted on a
semiadjustable articulator is recommended
when restoring a large portion of the patient's
posterior occlusion with cast metal restorations.
 It involves very little extra chair time and gives
the laboratory technician much more
information about the general occlusal scheme,
pathways of cusps, opposing cusp steepness and
groove direction, and the anatomy of the other
teeth in the mouth.

Temporary Restoration
 Direct technique
 Indirect technique

Final Impression
 The indirect technique for making cast metal
restorations is accurate and dependable.
 Fabrication of the cast metal restoration
takes place in the laboratory, on a cast made
from an impression of the prepared and
adjacent unprepared teeth.

 Ideal Requirements of an impression material:
 It must become elastic after placement in the mouth
because it must be withdrawn from undercut regions
that usually exist on the prepared and adjacent teeth.
 It must have adequate strength to resist breaking or
tearing on removal from the mouth.
 It must have adequate dimensional accuracy, stability,
and reproduction of detail so that it is an exact
negative imprint of the prepared and adjacent
unprepared teeth.
 It must have handling and setting characteristics that
meet clinical requirements.
 It must be free of toxic or irritating components.
 It must be able to be disinfected without distortion.

 The most common impression material of
choice for indirect restorations are the
polyvinyl siloxanes.
 Tissue retraction is recommended in case of
subgingival margins. Use of appropriate
styptics are recommended in case of
hemorrhage.

Wax Patterns
 The Impression are poured and working cast and
Dies are prepared.
 The working casts/Dies are mounted using the
interocclusal record made previously.
 The Patterns are formed using type I Inlay
pattern wax.The proximal contours and contact
are established first.
 Then the occlusal wax up is done. Payne has
advocated that the facioligual width of the tooth
be divided in quarters and then waxed up.
 Spruing, investing and Casting are done in the
conventional manner.

Seating, adjusting &
Polishing the casting
 Fit of the casting is confirmed on the die.
 The margins are burnished using a ball or a
Beavertail burnisher in case of gold restorations.
 The occlusion is checked using articulating paper
and corrections are made if any by selective
grinding.
 Rubber discs and points are used to polish the
casting, followed by a soft bristle wheel disc and
tripoli.

 In the patient’s mouth, the prepared tooth is
isolated.
 Check the proximal contacts. Passing a floss
interproximally will indicate the tightness and
position of the contact.
 If contact is open then soldering at the
contact point must be done.
 Occlusion is checked in both MI and Eccentric
movements and correction made if any.
 Margins are adpated in case of gold alloys
using a burnisher.

Cementation
 Before Cementation, isolate the tooth from saliva
with the aid of cotton rolls, and saliva ejector if
needed.
 Use a air syringe to dry the preparation walls, but
do not desiccate them.
 Manipulate the cement of choice according to
manufacturers instructions.
 The casting is cemented, by coating the
preparation surface of the casting with the cement
and place the casting in place using operative
pliers.Then press using ball burnisher in the pit
areas.Then, ask the patient to bite on a burlew
disc. Remove the excess cement, check for excess
cement interproximally using a floss.

Repair
 In case of fracture of the cast restoration, if
the area is small and if the restoration is
intact and retentive, then it may be repaired
using composites or amalgam.

 Tooth-Coloured Restorations
 Indirect Composites
 Ceramic Restorations
 Restoration
 Repair of Restorations
 CAD-CAM based restorations
 Inlay retained Bridges
 Strength and Longevity of Inlays and Onlays
 Review of Literature

Mondelli JPD 1980
 All occlusal cavity preparations decrease the
strength of teeth in proportion to the width of
the preparation.
 The Class I occlusal preparation reduces the
strength of the tooth less than the occlusal
portion of the Class II preparation with equal
width.
 The width of the isthmus was a statistically
significant factor. A desirable width of the
isthmus is one-fourth the intercuspal distance.
This dimension provides greater strength
regardless of the Class of the cavity.

Spruing for Inlays and
Onlays
 Patterns for inlays and onlays maybe sprued in
either of the following ways:
 Sprue former positioned at the contact point, this
preserves occlusal anatomy and will result in
increased expansion in the mesiodistal direction due
to mold expansion out end of the casting ring.
 Sprue former placed at the marginal ridges, this
preserves contacts at the expense of some occlusal
anatomy and provides for equal ex[ansion in all
directions.

Direct wax/Indirect wax
According to Anusavice,
 Type I – MediumWax used in DirectTechniques
 Type II – Soft waxes used in Indirect technique
 Composition: NaturalWaxes(Hydrocarbons of
paraffin and microcrystalline wax series,
carnauba wax, candelila wax and resins) and /or
synthetic waxes.They contain compatible
fillers to control expansion and shrinkage of the
wax product.
ANSI/ADA Speci fication No. 4

Inlay Wax flow(%)
Type of
wax
T=30° C
(Max)
T=37° C
(Max)
T=40° C
(Min)
T=40° C
(Max)
T=45° C
(Min)
T=45° C
(Max)
I - 1.0 - 20 70 90
II 1.0 - 50 - 70 90
Philips’ Science of Dental Materials, Anusavice, Eleventh Edition

According to Craig,
 Type 1 (soft) – used as an indirect technique
wax
 Type 2(hard) – used for direct patterns in the
mouth
Craigs’ Resorative Dental Materials, Powers and Sakaguchi, twelfth edition

Provisionalisation
 Polymethyl methacrylate(Duralay)
 Polyethyl methacrylate(Snap)
 Polyvinyl methacrylate(Trim)
 Protemp II : Bis-acryl composite resin
 VLC urethane dimethacrylate(Triad)

Margins of a class V cavity
in case of a gingival
recession?

Tooth Coloured Inlays and
Onlays

 Tooth-coloured indirect systems include
laboratory-processed composites or ceramics
such as porcelain fired on refractory dies or
hot pressed glasses.
 In addition, chairside computer-aided
design/computer-assisted manufacturing
(CAD/CAM) systems are currently available
and are used to fabricate ceramic
restorations.

Indications
 The indications for Classes I or II indirect
tooth-coloured restorations relate to a
combination of esthetic demands and size of
the restoration and include the following:
 Esthetics: Indirect tooth-coloured restorations
are indicated for Class I or Class II restorations
located in areas of esthetic importance for the
patient.

 Large defects or previous restorations: Indirect
tooth-coloured restorations should be considered
for restoration of large Class I or Class II defects or
replacement of large existing compromised
restorations, especially those that are wide
faciolingually and require cusp coverage. Large
preparations are best restored with adhesive
restorations that strengthen the remaining tooth
structure.
 Indirect tooth-coloured restorative materials are
more durable than direct composites, especially in
regard to maintaining occlusal surfaces and
occlusal contacts .

 The wear resistance provided by indirect materials is
especially important in large posterior restorations that
involve most or all of the occlusal contacts.
 However, without sufficient bulk, an extensive indirect
ceramic or composite restoration may fracture under
occlusal loading, particularly in the molar region
 Economic factors: Some patients desire the best dental
treatment available, regardless of cost. For these
patients, indirect tooth-coloured restorations may be
indicated not only for large restorations, but also for
moderate-sized restorations that might otherwise be
restored with a direct restorative material.

Contraindications
 Heavy occlusal forces:
Ceramic restorations may
fracture when they lack
sufficient bulk or are subject
to excessive occlusal stress,
as in patients who have
bruxing or clenching habits.
 Inability to maintain a dry
field: Adhesive techniques
require near-perfect
moisture control to ensure
successful long-term clinical
results.

 Deep subgingival preparations: Although this
is not an absolute contraindication,
preparations with deep subgingival margins
should be avoided.These margins are difficult
to record with an impression and are difficult
to finish. Additionally, bonding to enamel
margins is greatly preferred, especially along
gingival margins of proximal boxes.

Advantages
 Esthetics
 Conservative of tooth structure removal (less
extension)
 Insulative, having low thermal conductivity
 Repairable

 Improved physical properties: A wide variety of
high strength tooth-coloured restorative materials,
including laboratory-processed and computer-
milled composites and ceramics, can be used with
indirect techniques.
 Indirect restorations have better physical
properties than direct composite restorations
because they are fabricated under relatively ideal
laboratory conditions.
 Also, while CAD/CAM restorations are generally
fabricated chairside, the materials themselves are
manufactured under very nearly ideal industrial
conditions .

 Wear resistance: Ceramic restorations are
more wear resistant than direct composite
restorations, an especially critical factor when
restoring large occlusal areas of posterior
teeth. Laboratory-processed composite
restorations wear more than ceramics, but
less than direct composites.

 Reduced polymerization shrinkage: With
indirect techniques, the bulk of the
preparation is filled with the indirect tooth-
coloured restoration, and stresses are
reduced because very little composite
cement is used during cementation. Although
shrinkage of composite in thin bonded layers
can produce relatively high stress, studies
indicate that indirect composite restorations
have fewer marginal voids, less microleakage,
and less postoperative sensitivity than direct
composites.

 Ability to strengthen remaining tooth
structure:Tooth structure weakened by caries,
trauma, and/or preparation can be
strengthened by adhesively bonding indirect
inlays and onlays.The reduced
polymerization shrinkage stress obtained
with the indirect technique is also desirable
when restoring such weakened teeth.

 More precise control of contours and contacts:
Indirect techniques usually provide better contours
(especially proximal contours direct restorations because of the
improved access and visibility ) and occlusal contacts than
direct restorations.
 Biocompatibility and good tissue response:Ceramic
materials are considered the most chemically inert
of all materials.They are biocompatible and
generally are associated with a good soft tissue
response.The pulpal biocompatibility of the
indirect techniques is related more to the adhesive
composite cements rather than the ceramic
materials used.

 Increased auxiliary support: Most indirect
techniques allow the fabrication of the
restoration to be totally or partially delegated
to dental laboratory technicians. Such
delegation allows for more efficient use of
the dentist's time.

Disadvantages
 Increased cost and time: Most indirect techniques
require two patient appointments, plus fabrication
of a temporary restoration.These factors, along
with laboratory fees, contribute to the greater cost
of indirect restorations as compared to direct
restorations.
 However, while indirect tooth-coloured inlays and
onlays are more expensive than direct restorations
(amalgams or composites), they are usually less
costly than more invasive esthetic alternatives,
such as all-ceramic or porcelain-fused-to-metal
(PFM) crowns.

 Technique sensitivity: Restorations made using
indirect techniques require a high level of operator
skill. Precision is necessary during preparation,
impression, try-in, cementation, and finishing the
restoration.
 Brittleness of ceramics: A ceramic restoration can
fracture if the preparation does not provide
adequate thickness to resist occlusal forces or if the
restoration is not appropriately supported by the
cement medium and the preparation. Fractures can
occur either during try-in or after cementation,
especially in patients who generate unusually high
occlusal forces.

 Wear of opposing dentition and restorations:
Ceramic materials can cause excessive wear of
opposing enamel and/or restorations. Recent
improvements in ceramics have reduced this
problem, but ceramics, particularly if rough
and unpolished, can wear opposing teeth and
restorations.

 Resin-to-resin bonding difficulties: Laboratory-
processed composites are highly cross-linked,
so few double bonds remain available for
chemical adhesion of the composite cement .
Therefore the composite restoration must be
mechanically abraded and/or chemically
treated to facilitate adhesion of the cement .
The bond between the indirect composite
restoration and the composite cement is the
weak link in the system. However, bonding of
composite cements to properly treated
ceramic restorations is not a problem.

 Short clinical track record: Indirect bonded
tooth coloured restorations have become
relatively popular only in recent years and are
still not placed by many practitioners.
Fewer controlled clinical trials are available,
so the long-term durability of these
restorations, although expected to be good,
is not particularly well documented .

 Low potential for repair: Indirect restorations,
particularly ceramic inlays/onlays, are difficult
to repair in the event of a partial fracture. If
the fracture occurs in the restoration, an
indirect composite inlay or onlay can be
repaired using an adhesive system and a
lightcured restorative composite.The bond
strengths of indirect composite repair and
direct composite repair appear to be
equivalent .

 When a partial fracture occurs in a ceramic
inlay/onlay, repair is usually not a definitive
treatment.The actual procedure (mechanical
roughening, etching with hydrofluoric acid, and
application of a silane coupling agent before
restoring with an adhesive and composite) is
relatively simple.
 However, because ceramic inlays/onlays are
indicated in areas where occlusal wear, esthetics,
and resistance are important, direct composite
repairs are not suitable because that composite
will be exposed to a challenging environment.

 Difficult intraoral polishing: Indirect composite
restorations can be polished intraorally with
the same instruments/ materials used to
polish direct composites.
 Ceramics, on the other hand, are more
difficult to polish after they have been
cemented because of either limited access or
lack of appropriate instrumentation.

INDIRECT COMPOSITES:
INLAYS AND ONLAYS

 The physical properties of composite
restorations are improved when the composite is
free of voids, and the resin matrix is maximally
polymerized.
 Well-cured restorations is best accomplished in
the laboratory using devices that polymerize the
composite under pressure, vacuum, inert gas,
intense light, heat, or a combination of these
conditions. Several commercial systems use
these techniques to optimize the physical
properties of their composite materials.

 Laboratory-processed composite
inlays and onlays are more
resistant to occlusal wear than
direct composites, particularly in
occlusal contact areas. However,
they are less wear-resistant than
ceramic restorations.
 They offer easy adjustment, low
wear of the opposing dentition,
good esthetics, and potential for
repair.

Indications for Indirect
composite inlays and onlays
 When maximum wear resistance is desired
from a composite restoration,
 When achievement of proper contours and
contacts would otherwise be difficult, and
 When a ceramic restoration is not indicated
because of cost or concerns about wear of the
opposing dentition.

 A study by Donly et al, on a comparison of
composite inlays/onlays and cast gold
inlay/onlays revealed no statistically
significant differences. However, composite
inlays showed a 50% failure rate in molars
suggesting that they were better suited for
restoration of premolars.

Steps in Fabrication
 The indirect composite restoration is initially
formed on a replica of the prepared tooth.
 The composite is built up in layers,
polymerizing each layer with a brief exposure
to a visible lightcuring unit.
 After it is built to full contour, the restoration is
coated with a special gel to block out air and
thus prevent formation of an oxygen-inhibited
surface layer.
 Final curing is accomplished by inserting the
inlay into an ovenlike device that exposes the
composite to additional light and heat.
 The cured composite inlay is trimmed, finished,
and polished in the laboratory.

Materials used
 Tetric (IvoclarVivadent)
 Z100 (3M ESPE) (85%wt
ultrafine Zirconia-Silica Ceramic
particles that reinforce a highly
crosslinked polymeric matrix)
 Maxxim
 Gradia GC (hybrid MFR
formulation, couples a microfine
ceramic/prepolymer filler with a
urethane dimethacrylate matrix
to produce a superior ceramic
composite with exceptionally
high strength and superior
polishability.

 The ceramic materials used are feldspathic
porcelain, hot pressed ceramics, and
machinable ceramics designed for use with
CAD/CAM systems.
 The physical and mechanical properties of
ceramics come closer to matching those of
enamel than do composites.
 They have excellent wear resistance and a
coefficient of thermal expansion very close to
that of tooth structure.

Feldspathic Porcelain Inlays
and Onlays
 Dental porcelains are partially crystalline
minerals (feldspar, silica, alumina) dispersed in
a glass matrix. Porcelain restorations are made
from finely ground ceramic powders that are
mixed with distilled water or a special liquid,
shaped into the desired form, then fired and
fused together to form a translucent, material
that looks like tooth structure.
 Currently, many ceramic inlays and onlays are
fabricated in the dental laboratory by firing
dental porcelains on refractory dies.

 Many dental laboratories use this technique to
fabricate ceramic inlays and onlays because of its
low startup cost.
 The ceramic powders and investments are
relatively inexpensive, and the technique is
compatible with most existing ceramic laboratory
equipment such as firing furnaces.
 The major disadvantage of this technique is its
technique sensitivity. Problems with fit and
strength may be present. Inlays and onlays
fabricated with this technique must be handled
very gently during tryin to avoid fracture.
 Even after cementation, the incidence of fracture
is rather high for this type of ceramic restorations.

Hot Pressed Glass Ceramics
 In 1968, it was discovered that certain glasses
could be modified with nucleating agents and,
upon heat treatment, be changed into
ceramics with organized crystalline forms.
 Such glassceramics were stronger, had a
higher melting point than noncrystalline glass,
and had variable coefficients of thermal
expansion.

 At first, these glass-ceramics were primarily
developed for cookware and other
heatresistant products. In 1984, the glass-
ceramic material Dicor (Dentsply
International,York, Pennsylvania) was
patented and rapidly became a popular
ceramic for dental restorations.
 A major disadvantage of Dicor was its
translucency, which necessitated external
application of all shading.

 Dicor restorations were made using a lost-wax,
centrifugal casting process. Newer leucite-
reinforced glassceramic systems also use the
lost-wax method, but the material is heated to a
high temperature and pneumatically pressed,
rather than centrifuged, into a mold.
 Although studies by Catell et al indicate that hot
pressed ceramics are not significantly stronger
than fired feldspathic porcelains.They do appear
to provide better clinical service.

 The Moulds for pressed ceramics are
fabricated using the lost wax technique, and
the ceramic ingots are pressed into the mold
at 1100°C.
 The advantages of hot pressed ceramics are
their
(1) similarity to traditional "wax-up"
processes,
(2) excellent marginal fit, and
(3) relatively high strength.

 The surface hardness and occlusal wear of
these ceramics are very similar to enamel.
Pressed ceramic inlays are stronger than
porcelain inlays made on refractory dies, but
are still quite fragile until cemented.
 The incidence of postcementation fracture
for pressed ceramic inlays is expected to be
lower than that for ceramic inlays fired on
refractory dies, but higher than for inlays
made with CAD/CAM systems.

CAD CAM
 Rapid improvements in technology
have spawned several computerized
devices that can fabricate ceramic
inlays and onlays from high-quality
ceramics in a matter of minutes.
 Some CAD/CAM systems are very
expensive laboratory-based units
requiring the submission of an
impression or working cast of the
prepared tooth.
 The CEREC system was the first commercially
available CAD/CAM system developed for the
rapid chairside design and fabrication of ceramic
restorations.The recent version of this device is
the CEREC 3 (Sirona USA, Charlotte, North
Carolina).

 Generation of a CEREC
restoration begins after
the dentist prepares the
tooth and uses a
scanning device to
collect information
about the shape of the
preparation and its
relationship with the
surrounding structures.
This step is termed an
optical impression.

 A video image of the prepared tooth is
displayed to ensure proper positioning of the
scanning device.The CEREC systems use the
optical techniques of Moire fringe
displacement and active triangulation to
measure the height and depth of the
preparation.

 The system projects an image of the
preparation and surrounding structures on
a monitor, allowing the dentist or auxiliary
personnel to use the CAD portion of the
system to design the restoration.
 The operator must input and/or confirm
some of the boundaries of the restoration,
such as the position of the gingival margins.
Once the restoration has been designed,
the computer directs a micromilling device
(CAM portion of the system), which mills
the restoration out of a block of high
quality ceramic or composite in a matter of
minutes.The restoration is removed from
the milling device, ready for try-in and
cementation.

 The CEREC systems are designed to be used
chairside, which eliminates the need for a
conventional impression, temporary
restoration, and multiple appointments. In
addition to the speed of these systems, a
major advantage is the quality of the
restorative material.
 Manufacturers make blocks of machinable
ceramics or machinable composites specifically
for computer-assisted milling devices.
Because these materials are fabricated under
ideal industrial conditions, their physical
properties have been optimized.

 The major disadvantages
of CAD/CAM systems are
high initial cost and the
need for extra training.
 However, CAD/CAM
technology is changing
rapidly, with each new
generation of devices
having more capability,
accuracy, and ease of use .

Blocks used
 VITA manufactures CEREC Blocs by Sirona
andVITABLOCS®Mark II for CEREC®.These blocks
are made of feldspathic porcelain.
 IvoclarVivadent produces Empress® CAD leucite-
reinforced porcelain blocks, as well as IPS e.max
CAD blocks of lithium disilicate.
 3M™ ESPE™ makes the Paradigm™ C ceramic
and Paradigm™MZ100 composite blocks for
CEREC®
 Zirconia Blocks may also be used
 VITA CADTemp

Tooth Preparation
 Preparations for specific types of indirect
tooth-coloured inlays and onlays may vary
because of differences in fabrication steps for
each commercial system and variations in the
physical properties of the restorative
materials. Before beginning any procedure,
the clinician should have decided what type
of restoration is indicated.

 Preparations for indirect tooth-coloured
inlays and onlays basically are meant to
provide adequate thickness for the
restorative material and at the same time a
passive insertion pattern with rounded
internal angles and well-defined margins.
 All margins should have a 90 degree butt-
joint cavosurface angle to ensure marginal
strength of the restoration.
 All line and point angles, internal and
external, should be rounded to avoid stress
concentrations in the restoration and tooth,
thereby reducing the potential for fractures.

 The carbide bur or diamond used for tooth
preparation should be a tapering instrument
that creates occlusally divergent facial and
lingual walls.
 Gingival-occlusal divergence allows for
passive insertion and removal of the
restoration.
 The junction of the sides and tip of the
cutting instrument should have a rounded
design to avoid creating sharp, stress-
inducing internal angles in the preparation.

 Although the optimal gingival-occlusal
divergence of the preparation is unknown, it
should be greater than the 2° to 5° per wall
recommended for cast metal inlays and onlays.
 Divergence can be increased because the tooth
coloured restoration will be adhesively bonded
and as very little pressure can be applied during
try-in and cementation.
 Throughout preparation, the cutting
instruments used to develop vertical walls are
oriented to a single path of withdrawal, usually
along the long axis of the tooth crown.

 The occlusal step should be prepared 1.5 to 2 mm
in depth.
 Most composite and ceramic systems require that
any isthmus and any groove extension be at least
1.5 mm wide to decrease the possibility of fracture
of the restoration.
 Facial and lingual walls should be extended to
sound tooth structure and should go around the
cusps in smooth curves.
 Ideally, there should be no undercuts that would
prevent the insertion or removal of the
restoration. Small undercuts, if present, can be
blocked out using a glass-ionomer liner.

Rounded axiopulpal
line angle
Widened isthmus

 The pulpal floor should be smooth and relatively
flat. Following removal of extensive caries or
previous restorative material from any internal wall,
the wall is restored to more nearly ideal form with a
light-cured glass-ionomer liner/base.
 The facial, lingual, and gingival margins of the
proximal boxes should be extended to clear the
adjacent tooth by at least 0.5 mm.These clearances
will provide adequate access to the margins for
impression material and for finishing and polishing
instruments.
 For all walls, a 90-degree cavosurface margin is
desired because composite and ceramic inlays are
fragile in thin cross-section.

 The gingival margin should be extended as
minimally as possible because margins in
enamel are greatly preferred for bonding and
because deep subgingival margins are difficult
to record and to isolate properly during
cementation.
 When a portion of the facial or lingual surface
is affected by caries or other defect, it may be
necessary to extend the preparation (with a
gingival shoulder) around the transitional line
angle to include the defect.The axial wall of
the shouldered extension should be prepared
to allow for adequate restoration thickness.

 When extending through or along cuspal
inclines to reach sound tooth structure, a cusp
usually should be capped if the extension is
two thirds or greater than the distance from
any primary groove to the cusp tip.
 If cusps must be capped, they should be
reduced 1.5 to 2 mm and should have a 90
degree cavosurface angle.

 When capping cusps, especially centric holding
cusps, it may be necessary to prepare a shoulder
to move the facial or lingual cavosurface margin
away from any possible contact with the
opposing tooth, either in maximum intercuspal
position or during functional movements.
 Such contacts directly on margins can lead to
premature deterioration of marginal integrity.
 The axial wall of the resulting shoulder should
be sufficiently deep to allow for adequate
thickness of the restorative material and should
have the same path of draw as the main portion
of the preparation.

 During preparation, stains on the external
walls, such as those often left by corrosion
products of old amalgam restorations, should
be removed. Such stains could appear as
black or gray lines at the margin after
cementation.
 It is especially critical to generously round all
line and point angles, internal and external,
to avoid areas of stress concentrations that
could later lead to fracture of the restoration.

Impressions
 Most tooth-coloured indirect inlay/onlay
systems require an impression of the
prepared tooth and the adjacent teeth as well
as interocclusal records, which allow the
restoration to be fabricated on a working cast
in the laboratory similar to that of cast
restorations.

Temporary Restoration
 This may be fabricated in the conventional
manner, using the direct or indirect method.
 Using Acrylic resin or Bisacryl composite
materials.
 Care must be taken to avoid bonding the
temporary restoration to the preparations.
 A non-eugenol based temporary cement is
recommended for the same. If the temporary
phase is expected to last more than 3 weeks,
zinc phosphate cement may be used.

CAD CAM Technique
 Clinical procedures for CAD/CAM systems such as the
CEREC differ somewhat from the procedures
previously described.
 Tooth preparations for CAD/CAM inlays must reflect
the capabilities of the CAD software and hardware and
the CAM milling devices that fabricate the
restorations.
 One example of how preparations are modified when
using the CEREC system pertains to undercuts.
Laboratory-fabricated indirect systems require the
preparation to have a path of draw that allows
insertion and removal of the restoration without
interferences from undercuts. However, the CEREC
system automatically "blocks out" any undercuts
during the optical impression.

 Occlusally convergent walls can result in a more
conservative preparation along the occlusal aspect,
especially when replacing old amalgam
restorations, which were prepared with such
undercuts for retention.
 Care should be taken, however, not to allow
excessive undercuts especially at the base of the
cusps.These undercut areas eventually will be filled
with the composite cement, and these materials
lack the properties to act as dentin replacements.
 Also, large undercuts may result in undetected
internal voids during cementation, which could lead
to dramatic failures.The facial and lingual walls of
the proximal boxes should be prepared without
undercuts and with draw to avoid excessively wide
composite cement lines.

 Using the CEREC system, an experienced
dentist can prepare the tooth, fabricate an
inlay, and deliver it in approximately 1 hour.
This system eliminates the need for a
conventional impression, temporary
restoration, and multiple patient
appointments.

Try in and cementation
 The try-in and cementation of tooth-coloured
inlays / onlays are more demanding than that for
cast metal restorations because of:
 The relatively fragile nature of the ceramic or composite
material,
 The requirement of near-perfect moisture control, and
 The use of composite cements.
 The ceramic or composite inlay is relatively fragile
until it is bonded in place with composite cement.
Very little pressure should be applied to the
restoration during try-in. Because of this fragility,
occlusal evaluation and adjustment are delayed
until after cementation.

 Optimum Moisture control must be maintained.
 After removing the temporary restoration, all the
temporary cement is cleaned from preparation walls.
 The inlay or onlay is placed into the preparation using
very light pressure to evaluate its fit. If the restoration
does not seat completely, the most likely cause is an
overcontoured proximal surface. Using the mouth mirror
where needed, the embrasures should be viewed from
the facial, lingual, and occlusal aspects to determine
where the proximal contour needs adjustment to allow
final seating of the restoration, while simultaneously
producing the correct position and form of the contact.
Passing thin dental floss through the contacts will reveal
the tightness and position, thus signifying to the
experienced operator the degree and location of excess
contact.

 Articulating papers also can be successfully
used to identify overtight proximal contacts.
Abrasive disks are used to adjust the proximal
contour and contact relationship.
 While adjusting the intensity and location of
the proximal contacts, successively finer grits
of abrasive disks are used to polish the
proximal surfaces because they will be
inaccessible for polishing after cementation.

 If the proximal contours are not overcontoured, and the
restoration still does not fit completely, the preparation
should be checked again for residual temporary
materials or debris.
 If the preparation is clean, internal and/or marginal
interferences might also prevent the restoration from
seating completely.
 Once these interferences have been identified through
careful visual inspection of the margins and/or using fit-
checker materials, they should be adjusted on the
restoration, on the preparation, or both. Fortunately,
these interferences are rare because contemporary
impression materials and ceramic systems are very
accurate, and the laboratory usually applies a die-spacer
on the internal aspects of the preparation to avoid
difficulties in seating the restoration.

 Marginal fit is verified after the restoration is
completely seated. Slight excesses of contour
can be removed, if access allows, using fine-grit
diamond instruments or 30-fluted carbide
finishing burs.
 These adjustments are preferably done after the
restoration is cemented, to avoid marginal
fractures. Most indirect tooth-coloured
restorations have slightly larger marginal gaps
than comparable gold restorations.

Cementation
 For proper adhesive bonding, the internal
surface of the inlay/onlay must be treated
before cementation.The techniques and
materials vary, depending on the specific
restorative system used.
 For most laboratory-processed composite
inlays/ onlays, the resin matrix has been
polymerized to such an extent that few
bonding sites are available for the composite
cement to chemically bond to the internal
surfaces of the restoration.

 To improve the bond of the cement to the
processed composite restoration, some
systems require the use of a solvent to soften
the internal surfaces of the restoration before
cementation.
 Other systems recommend sandblasting or
air-abrading the inside of the composite
restoration with aluminum-oxide abrasive
particles to increase surface roughness and
surface area for bonding.

 For ceramic inlays and onlays,
hydrofluoric acid is usually used
to etch the internal surfaces of
the restoration.
 Such acid-etching increases
surface relief and therefore not
only increases the surface area,
but also results in
micromechanical bonding of
the composite cement to the
ceramic restoration.
 Hydrofluoric acid-etching is
usually done by the laboratory.

 However, the clinician should check the
internal surface of the restoration to confirm
the etching, which is evident by a white-
opaque appearance similar to acid-etched
enamel.
 Chairside ceramic etching is done with a 2-
minute application of 10% hydrofluoric acid
on the internal surfaces of the inlay/onlay.
After etching, the ceramic is treated with a
silane coupling agent to facilitate chemical
bonding of the composite cement.

 The preparation surfaces are etched and treated
with the components of an appropriate
enamel/dentin bonding system.Typically, the
final step of the bonding system also is applied to
the internal surfaces of the restoration previously
etched and silanated.
 A dual-cure composite cement is mixed and
inserted into the preparation with a paddle-
shaped instrument or a syringe.
 The internal surfaces of the restoration also are
coated with the composite cement, and the inlay
is immediately inserted into the prepared tooth,
using light pressure.

 Excess composite cement is removed with
thin-bladed composite instruments, brushes,
or an explorer.The operator must be careful
not to remove composite from the marginal
interface between the tooth and the inlay.
The cement is now light-cured from occlusal,
facial, and lingual directions for a minimum
exposure of 60 seconds from each direction.

Finishing and Polishing
For ceramic restorations
 Medium- or fine-grit diamond instruments are
used initially to remove any excess composite
cement back to the margin.
 Care must be taken to preserve the glazed
surface of ceramic restorations as much as
possible. Slender flame interproximally, while
larger oval or cylindric shapes are used on the
occlusal surface.
 After using the fine-grit diamond instruments,
30-fluted carbide finishing burs are used to
obtain a smoother finish.

For indirect composite restorations
 Finishing may be started with 12-fluted
carbide finishing burs instead of diamonds.
 Interproximally, a No. 12 surgical blade can
be used to remove excess composite cement
when access permits.Abrasive strips of
successively finer grits also can be used to
remove slight interproximal excesses. Much
care must be used to avoid damaging the
gingiva or the root surfaces when using such
instruments interproximally.

 With care and appropriate instrumentation,
ceramic restorations can be polished to a
surface smoother than glazed porcelain.

 After the finishing and polishing the occlusal
contacts are verified and corrected if
necessary using a fine grit diamond, followed
by 30-fluted carbide finishing burs.
 The restoration is then repolished in areas of
adjustments made.
 Indirect composites may be polished using
the same instrumentation and materials used
for direct composites.

CAD CAM Restorations
 When delivering a CAD/CAM inlay, more
adjustments are usually necessary when trying-
in, finishing, and polishing.
 The original CEREC system milled the occlusal
surface relatively flat without any significant
surface detail, and did not take into account the
opposing occlusion.The newer CEREC 2 and 3
systems are able to mill in occlusal contours in a
variety of manners.

 They can extrapolate existing contours
beyond the cavo surface margin to the
central groove, or they can build the surface
up to the level of a scanned wax bite.The
neighbouring teeth, in particular the marginal
ridges and cusp heights, also can be used as
references for the design of the occlusal
surface of a CAD/CAM restoration.

 If the preoperative contours of the tooth were
satisfactory, the system can reproduce them
in the restoration.
 When adjusting the occlusion of a CAD/CAM
inlay, it may be necessary to use medium-grit
diamonds with air-water spray coolant for
initial contouring of the occlusal surface,
followed by the instrumentation previously
discussed for finishing and polishing.

Common Problems and Solutions
 The most common cause of failure of tooth-
coloured inlays and onlays is bulk fracture. If
bulk fracture occurs, replacement of the
restoration is almost always indicated.

Repair
 Minor defects in indirect composite and ceramic
restorations can be repaired with relative ease.
Of course, before initiating any repair procedure,
the operator should determine whether
replacement rather than repair is the appropriate
treatment. If repair is deemed to be the
appropriate treatment, the dentist should
attempt to identify the cause of the problem and
correct it if possible. For example, a small
fracture due to occlusal trauma may indicate that
some adjustment of the opposing occlusion is
required.

 For both composite and ceramic inlays, the
repair procedure is initiated by mechanical
roughening of the involved surface.While a
coarse diamond may be used, a better result
is obtained with the use of air-abrading or
grit-blasting with aluminum oxide particles
and a special intraoral device.

 For ceramic restorations, the initial mechanical
roughening is followed by brief (typically 2
minutes) application of 10% hydrofluoric acid
gel. Hydrofluoric acid etches the surface,
creating further microdefects to facilitate
mechanical bonding. Although many indirect
composites contain etchable glass filler
particles, hydrofluoric acid treatment of
composites is neither necessary nor
recommended. However, a brief application of
phosphoric acid may be used to clean the
composite surface after roughening.

 The next step in the repair procedure is
application of a silane coupling agent. Silanes
mediate chemical bonding between ceramics
and resins and also may improve the
predictability of resin-resin repairs.The
manufacturer's guidelines should be followed
when using silanes, as they can differ
substantially from one particular product to
another. After the silane has been applied, a
resin-bonding agent is applied and light-cured.
A composite of the appropriate shade is placed,
cured, contoured, and polished.

Indications:
 Abutment teeth with fillings
 Replacing 1 or 2 teeth in the
premolar, molar region
 Metal-ceramic
 All-ceramic
 Fiber –reinforced composite

Contraindications:
 Pontic span too large
 Excessive parafunctions
 Clinical crown too short
 Weakend periodontium
 Occlusal anomalies
 Abutment teeth tilting
 Poor oral hygiene

 Advantages:
 Less destructive to tooth
structure
 Cavities, fillings involved
in preparation
 Good esthetics
 Fixed restoration
 Marginal finishing line
easy to clean-
preservation of the
periodontium
 Disadvantages:
 Only 1 or 2 missing
teeth-short pontic span

Preparation for an inlay-retained bridge Apply Primer to the enamel and dentin and disperse

Etch the pressed inlay-retained bridge with IPS
Ceramic Etching gel for 20 sec., rinse and silanize. Fill the bridge with Cement and remove excess

IPS e.max ZirPress on Zirconium Oxide Inlaybridge

Strength
 Noble Metal Alloys
 High Noble
 Yield Strength: 270-600 Mpa
 Noble
 Yield Strength: 260-1145 MPa
 Base Metal Alloys
 Yield Strength: 644-710 Mpa
 Tensile Strength: 700-970 MPa

 Ceramics
 Heat Pressed
 Flexural Strength: 121-350 Mpa
 Feldspathic
 Flexural Strength: 60 Mpa
 CAD/CAM
 Flexural Strenght: 105-900 MPa
 Composites
 Direct and Indirect
 Flexural Strength: 60-180 MPa
 Amalgam
 Compressive Strength: 227-526 MPa

Review of literature
 In a dental practice, 2328 ceramic inlays were placed
in 794 patients.The restorations were manufactured
chairside using CEREC technology and adhesively
inserted at the same appointment.
 The probability of survival was 95.5% after 9 years;
35 CEREC restorations were judged as failures.
 In a clinical follow-up light-microscopic examination
of 44 randomly selected restorations, an average
composite joint width of 236.3 microns was found.
45.1% of the restorations exhibited a perfect margin,
and 47.4% of the investigated joint sections showed
underfilled margins.
PosseltA, KerschbaumT. Longevity of 2328 chairside CEREC inlays and onlays. Int
J Comput Dent. 2003; 6(3): 231 – 248.

 This follow-up study examined the performance of CEREC inlays
and onlays in terms of clinical quality over a functional period of 10
years.
 Of 200 CEREC inlays and onlays placed in a private practice between
1989 and early 1991, 187 restorations were observed over a period of
10 years.The restorations were fabricated chairside using the
CEREC-1 computer-aided design/manufacturing (CAD/CAM)
method andVita MK I feldspathic ceramic.An adhesive technique
and luting composite resin were used for seating the restorations.
After 10 years, the clinical performance of the restorations was
evaluated using modified USPHS criteria.The results were used to
classify success and failure.
 RESULTS:The success rate of CEREC inlays and onlays dropped to
90.4% after 10 years. A total of 15 (8%) failures were found in 11
patients. Of these failures, 73% were caused by either ceramic
fractures (53%) or tooth fractures (20%).The reasons for the
remaining failures were caries (20%) and endodontic problems (7%).
The three-surface CEREC reconstructions were found to have the
most failures.
OttoT, De Nisco S. Computer-aided direct ceramic restorations: a 10-year prospective
clinical study of CEREC CAD/CAM inlays and onlays. Int J Prosthodont. 2002; 15(2): 122 –
128.

 29 clinical reports were identified in the search.The systematic
analysis reduced the focus of review to 15 studies. The data
available establishes ceramic intra-coronal restorations
machined by the CEREC System as a clinically successful
restorative method with a mean survival rate of 97.4% over a
period of 4.2 years.The review also highlights the reasons and
the rates of failure for this type of restoration.The predominant
reasons for failures are fracture of the ceramic, fracture of the
supporting tooth, postoperative hypersensitivity and wear of the
interface lute.
 SIGNIFICANCE: Machinable ceramics, as used by the CEREC
System provide a useful restoration with a high success rate.
These restorations are color stable and wear at a clinically
acceptable rate.Wear of the luting composite on occlusal
surfaces leads to the phenomenon of submargination. Ceramic
fracture, wear at the interface and post-operative
hypersensitivity remain a problem which requires further
investigation.
Martin N, Jedynakiewicz NM. Clinical performance of CEREC ceramic inlays: a
systematic review. Dent Mater. 1999; 15(1): 54 – 61.

 CEREC or IPS Empress ceramic inlays, Arabesk or Charisma
F resin-based composite (RBC) restorations were compared
in this study.
 There was no significant difference (P > 0.05) between the
mean values of the sound teeth (2,102 N) and the teeth
with the CEREC ceramic inlays (2,139 N). However, both
groups demonstrated a significant difference (P < 0.05)
when compared with the teeth with IPS Empress ceramic
inlays (1,459 N) and Arabesk RBC restorations (1459 N). No
significant differences were found between the last two
groups. Molars restored with Charisma F composite
restorations (1,562 N) revealed no significant difference
when compared with all other groups including controls (P
> 0.05).
 A stabilization of molars is possible by means of an
adhesive restoration in the form of an “internal splinting”
regardless of the restorative material used.
Bremer BD, GeurtsenW. Molar fracture resistance after adhesive restoration
with ceramic inlays or resin-based composites. Am J Dent. 2001; 14(4): 216 – 220.

 Al-Hiyasa et al in their study to compare the
wear of teeth against four dental porcelains
and gold concluded that gold was the least
abrasive. And that machinable ceramics
significantly less abrasive and more resistant
to wear than the conventional aluminous and
bonded porcelains.
Al-Hiyasat AS, SaundersWP, Sharkey SW, Smith GM, GilmourWH. Investigation of
human enamel wear against four dental ceramics and gold. J Dent. 1998; 26(5-6): 487
– 495.

 An in vitro study to evaluate the fracture load of
zircon frames veneered with a polymer glass
holding box inlay-retained fixed partial
dentures was conducted by Ohlmann et al.
 And they concluded that Polymer veneered
FPDs withY-TZP frames showed acceptable
fracture resistance values, but they cannot yet
be unreservedly recommended for clinical use.
Fracture values for CAD/CAM manufacturedY-
TZP frames combined with a press ceramic
deserve further clinical investigation.
Brigitte Ohlmann 1†, Olaf Gabbert 1, Marc Schmitter 1, Herbert Gilde 1 and Peter Rammelsberg. Fracture
resistance of the veneering on inlay-retained zirconia ceramic fixed partial dentures. 2005,Vol. 63, No. 6, Pages
335-342 Acta Odontologica

 Wolf compared the margin quality of
titanium and high gold inlays and found that
the margins of titanium restorations were
acceptable clinically but high gold
restorations had better marginal adaptation.
B.Wolf Margin quality of titanium and high-gold inlays and onlays — a clinical study
Dental Materials,Volume 14, Issue 5, Pages 370-374

 A clinical study on Zirconia based ceramic
inlay retained FPDs inferred that on’y 1o% of
the bridges were unacceptable after a 2 year
period of study. And 80% of the restorations
were acceptable in accordance with the US
public health criteria.
 Within the limitation of this study, it was
concluded that Zirconia based ceramic inlay
retained fixed partial dentures showed a
satisfactory clinical performance over 24
months period.
Mahmoud Abdul Salam Mohamed Shakal CLINICAL EVALUATIONOF ZIRCONIA BASED
CERAMIC INLAY RETAINED FIXED PARTIAL DENTUREVolume (55), Number (3.1), Jul 2009

 Niek et al reported a survival for composite
resin of 91.7% in 5 years and 82.2% in 10
years.
 For amalgam the survival rate is 89.6% at 5
years and 79.2 % at 10 years
Dental materials 2007; 23: 2-8

 A study was done to evaluate the clinical
performance of bonded leucite reinforced
glass ceramic inlays and onlays after 8 years
Conclusions:
 Marginal integrity was decreased at the end
of 8 years
 Surface roughness was increased
 No significant influence was attributed to the
size of the inlay
 The absence of enamel in proximal boxes did
not have any influence on the marginal
performance or secondary caries of the
inlays and onlays.
Dent Materials 2005;21:262–71

 Chipping mainly occurred in areas having
been subjected to rotary occlusal adjustment
 No statistically significant correlation
between dimensions of the inlay and
fractures were observed
 It was concluded that IPS Empress inlays
demonstrated to be successful even in large
defects. Neither the absence of enamel
margins nor cuspal replacement affected the
quality of the restorations.
Dent Materials 2005;21:262–71

 Various long term studies upto 15 years have
shown that ceramic inlays made of
prefabricated Cerec Mk block ceramic had a
signifcantly higher survival rate than
laboratory fired ceramic inlays.
Chicago :Quintessence 2006:65-72

 A study was done to examine the performance of
Cerac inlays and onlays in terms of clinical quality
over a functional period of 10 years
 Three surface inlays had significant lower survival
rates
 Premolars have slightly lower risk than molars
 Higher risk of failures were seen in male patientsIn
most cases facture occurred at thinnest region of
the inlay (isthmus fracture) or at the marginal
ridges
 Bruxism should be considered a risk group with
regards to Cerec restorations
Int J Prosthodont 2002;15:122-128

 A study was done to compare 4 types of inlays direct
composites, Indirect composites ( Estilux), Direct
ceramic ( cerec system), Indirect ceramic (Vita Dur
N)
 The survival rate for inlays without repair was 80%
for cerec inlays , 66.9% forVita Dura N , 55.5% for
Estilux and 66.7% for direct composites
 No significant differences in surface textures
 No significant differences in color match but
marginal discoloration was found in composite
restorations
 Main reason for failures ofVita Dura N was fracture
of the restorations and for composites it was
secondary caries and pulpal reactions
Quintesssence Int 2006;37: 139-144

References:
1. Shillingberg, H.T. Jr et al. Fundamentals
of Fixed Prosthodontics, 3rd edn.
2. Shillingberg, H.T. Jr et al. Fundamentals
of Tooth Preparation.
3. Rosensteil, Land, Fujimoto. Contemporary
Fixed Prosthodontics. Fourth Edition.
4. Sturdevant's Art and Science of Operative
Dentistry. Fifth edition
5. G. F. Kantorowicz. Inlays, Crowns and Bridges.
3rd Edition.
6. Cowell, Curson. Inlays, Crowns and Bridges. 4th
Edition.

7. Posselt A, KerschbaumT. Longevity of 2328 chairside
CEREC inlays and onlays. Int J Comput Dent. 2003;
6(3): 231 – 248.
8. OttoT, De Nisco S. Computer-aided direct ceramic
restorations: a 10-year prospective clinical study of
CEREC CAD/CAM inlays and onlays. Int J Prosthodont.
2002; 15(2): 122 – 128.
9. Martin N, Jedynakiewicz NM. Clinical performance of
CEREC ceramic inlays: a systematic review. Dent
Mater. 1999; 15(1): 54 – 61.
10. Bremer BD, GeurtsenW. Molar fracture resistance
after adhesive restoration with ceramic inlays or resin-
based composites.Am J Dent. 2001; 14(4): 216 – 220.
11. Al-Hiyasat AS, SaundersWP, Sharkey SW, Smith GM,
GilmourWH. Investigation of human enamel wear
against four dental ceramics and gold. J Dent. 1998;
26(5-6): 487 – 495.

12. Brigitte Ohlmann, Olaf Gabbert, Marc
Schmitter, Herbert Gilde and Peter Rammelsberg.
Fracture resistance of the veneering on inlay-
retained zirconia ceramic fixed partial dentures.
2005,Vol. 63, No. 6, Pages 335-342 Acta
Odontologica
13. B.Wolf Margin quality of titanium and high-gold
inlays and onlays — a clinical study
Dental Materials,Volume 14, Issue 5, Pages 370-374
14. Mahmoud Abdul Salam Mohamed Shakal Clinical
Evaluation Of Zirconia Based Ceramic Inlay Retained
Fixed Partial Denture.Volume (55), Number (3.1), Jul
2009
15. Dental materials 2007; 23: 2-8
16. Dent Materials 2005;21:262–71
17. Chicago :Quintessence 2006:65-72
18. Int J Prosthodont 2002;15:122-128

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