ceramic Inlays and onlays

Minimally invasive restorations
Ceramic Inlays and onlays
(adhesive or bonded onlays)
10/21/2019 Sherif sultan,BDS,MsC,PhD,Fixed prosthodontics 1

Minimal intervention or minimally
invasive dentistry is a modern
dental practice designed around
the principal aim of preservation of
as much of the natural tooth
structure as possible.(maximal
preservation of tooth structure)
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Sherif sultan,BDS,MsC,PhD,Fixed
prosthodontics
2

Inlay is 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.
Ceramic inlay is a ceramic
intracoronal restoration.
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• Onlay is a partial-coverage
restoration that restores one
or more cusps and adjoining
occlusal surfaces or the entire
occlusal surface and is
retained by mechanical or
adhesive means.
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Introduction
• The application of ceramic as a restorative material is not
limited to complete coverage crowns or estheticveneers.
Posterior teeth with moderate-sized defects can be
restored with inlays or onlays as an alternative to
amalgam, gold, or resin.
• For esthetic restorations, ceramic inlays and onlays
provide a durable alternative to posterior composite
resins.
• The indirect fabrication of these restorations can
eliminate potential issues associated with operator error,
polymerization shrinkage, and layering composite resin in
association with the direct technique.
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• Bonding the ceramic restoration to tooth
structure can help reinforce areas of
weakened tooth structure and enable more
conservative tooth preparation.
• The procedure consists of bonding the
ceramic restoration to the prepared tooth
with an acid-etch technique. The bonding
mechanism relies on acid etching of the
enamel and the use of composite resin, as in
the resin retained fixed dental prosthesis
technique.
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• Bonding to porcelain is achieved by etching
with hydrofluoric acid and the
use of a silane-coupling agent
(materials are identical to those marketed as
porcelain repair kits).
• Bonded or adhesive onlays can also be
fabricated from laboratory-processed
(indirect) composite resin instead of the
ceramic.
• Bonded ceramic inlays are showing promising
longevity: 8- to 10-year performance.
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Indications
• When an esthetic restoration is required in a posterior tooth and
the size of the defect is beyond what can predictably be restored
with composite resin, but small enough not to warrant a
complete crown, a ceramic inlay or onlay is indicated.
• In general, when cuspal coverage is required for restoration of a
tooth (cuspal coverage is indicated when cusp thickness is 2mm
for vital and 3mm for nonvital tooth), composite resin is not a
viable long-term restorative material.
• Direct Composite resin is the best choice for class 1 and small
size class 2 in which the proximal cavity does not reach to the
transitional line angles, if reach a ceramic inlay is indicated.
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Contraindications
• Poor oral hygiene or active caries.
• Because of their brittle nature, ceramic
restorations may be contraindicated in patients
with excessive occlusal loading, such as those
with bruxism.
• When more than two thirds of the occlusal
table requires restoration, a complete crown is
generally preferred over a ceramic onlay.
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Advantages
• The esthetic durability of ceramic restorations is superior
to that of composite resin restorations, which stain over
time.
• wear resistance is more than composite restorations.
• Marginal leakage associated with polymerization
shrinkage of composite resin is reduced because the
luting layer is comparatively thin.
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• In some situations, this restoration enables the
clinician to conserve tooth structure. When a
significant amount of tooth structure is already missing
and retention form is limited, the ceramic restoration
offers the advantage of bonding. For instance, if a
molar with a fractured cusp requires restoration, the
defect is often treated with a complete crown,
sometimes preceded by endodontic treatment and a
suitable buildup. Such treatment necessitates removal
of a significant amount of tooth structure and
compromises the tooth’s long-term prognosis.
However, with a ceramic onlay, only the missing cusp
need be replaced by bonding the ceramic material to a
circumferential band of enamel; minimal if any
additional retention form is required, and a significant
amount of tooth structure is conserved, in comparison
to the previously described approach
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Nontraditional preparation design for all-ceramic partial coverage. For this onlay preparation,
the wide circumferential band of enamel provides for bonding. A, Tooth preparation. B,
Clinical evaluation of lithium disilicate restoration before the crystallization step. C, Completed
restoration.

Disadvantages
• Ceramics can be abrasive. If care is not taken to
achieve a smooth, well-polished restoration,
opposing enamel that is in sliding contact with
the restoration can produce wear. Rough
porcelain is extremely abrasive of the opposing
enamel. However this is not true for all ceramic
types e.g:- Castable glass-ceramic restorations
are less abrasive than the traditional feldspathic
porcelain.
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• Wear of the composite resin luting agent leading
to marginal gaps and recurrent caries.
• Achieving accurate occlusion can be challenging
with ceramic inlays and onlays. Because they are
fragile, occlusal adjustment needs to occur
intraorally, after cementation. Accurate
adjustment of the occlusion can occur only after
the restoration has been bonded with an
adhesive resin. Therefore, any roughening of the
surface must receive the final polish intraorally,
which can prove time consuming. Similarly,
finishing of the margins can be difficult in the less
accessible interproximal areas. Resin flash or
overhangs can be difficult to detect and may
initiate periodontal disease.
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• Bonding is highly technique sensitive. Achieving an
excellent bond between the tooth and the ceramic
material is achievable, but not simple. The dentist
must ensure excellent isolation, adhere precisely to
the resin manufacturer’s directions, and bond to
tooth structure that is free of defects (i.e.,
sclerotic, decalcified, or otherwise compromised).
• Accuracy is very important with these restorations
because accurately fitting restorations (marginal
gaps less than 100 μm) have been shown to
improve clinical outcomes. so it is better to do
these preparations under magnification
(microscope).
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Preparation
• 1- Occlusal Analysis
• Carefully assess the occlusal contact relationship and mark it
with articulating film. The margins of the restoration should
not be too close (≥1.0 mm) to a centric contact; otherwise,
there will be damaging stresses at the restoration-enamel
junction. To avoid chipping or wear of the luting resin, the
margins of the restoration should not be at a centric contact.
The specified dimensions are minimal values to achieve
adequate ceramic thickness to reduce the risk of fracture. In
general, weaker materials require additional bulk
B. Apply rubber dam. Because good visibility and moisture
control are essential during tooth preparation and caries
excavation.
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• As with any indirect restoration, a path of
draw must be established.
• Tapered diamond burs can produce the
needed divergence to the internal walls and
create the defined 90-degree cavosurface
margins that help maintain the necessary bulk
and strength.
• A rounded internal form prevents stress
concentrations or voids in the luting agent.
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Outline Form
• Preparation is generally governed by the existing restorations
and caries and is broadly similar to that for conventional metal
inlays and onlays (but occl .reduction is 1.5-2mm, no bevels, no
functional cusp ledge or occlusal shoulder, no axiopulpal
grooves). Because of the resin bonding, axial wall undercuts can
sometimes be blocked out with resin-modified glass ionomer
cement, which can allow preservation of additional enamel for
adhesion. However, undermined or weakened enamel should
always be removed.
• The central groove reduction (typically 2 mm) follows the
anatomy of the unprepared tooth rather than a monoplane. This
provides additional bulk for the ceramic. The outline should
avoid occlusal contacts. Areas to receive onlays need 1.5 mm of
clearance in all excursions to allow for adequate ceramic
thickness and prevent fracture.
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• Extend the box to allow a minimum proximal
clearance of 0.6 mm for impression making. The
margin should be kept supragingival, which
makes isolation during the crucial luting
procedure easier and improves access for
finishing. If necessary, electrosurgery or crown
lengthening can be performed.
• The pulpal depth of the gingival floor of the box
should be approximately 1 mm.
• Round all internal line angles. Sharp angles lead
to stress concentrations and increase the
likelihood of voids during the luting procedure.
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Caries Excavation
• With an excavator or a round bur in the low-
speed handpiece, remove any caries not
included in the outline form preparation.
• Place a resin-modified glass ionomer cement
base to restore the excavated tissue in the
gingival wall.
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Margin Design
• Use a 90-degree butt joint for ceramic inlay
margins. Beveled margins are contraindicated
because bulk is needed to prevent fracture. A
distinct heavy chamfer margin is recommended
for ceramic onlay margins.
• Refine the margins with finishing burs and hand
instruments, trimming back any glass ionomer
base. Margins in enamel must be smooth and
distinct for a ceramic restoration to fit accurately.
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Occlusal Clearance (for Onlays)
• Check the occlusal clearance after the rubber
• dam is removed. Clearance must be a
minimum of 1.5 mm to prevent fracture in all
excursions. This can be easily evaluated by
measuring the thickness of the resin interim
restoration with a dial caliper.
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Preparation Guidelines for All
Ceramic Inlays and Onlays
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Secondary impression
• Either take conventional impression as in crown
ad bridge or make digital impression with
CAD/CAM
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Provisional restoration
direct method or with CAD/CAM
• apply the matrix band and wedges as in preparation for condensing
a class II amalgam restoration. The wedges should be placed with
firm pressure so that when the band is removed, proximal contact
is reestablished.
• The band must seal all aspects of the proximal cavosurface margins.
• Using petrolatum on a small cotton pellet, lightly coat all sides of
the cavity preparation and the matrix band.
• Make a handle to remove the resin by placing one end of a 2- to 3-
cm length of unwaxed dental floss in the preparation cavity.
• Mix a small amount of poly-R′ methacrylate, and when it can be
kneaded like bread dough, mold a small cone of it on the end of an
amalgam condenser.
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• Lightly condense the resin into the cavity, being careful not to force it past
the matrix into an undercut. Immediately remove as much occlusal excess
as possible with a sharp spoon excavator.
• Monitor the polymerization by light probing with a hand instrument.
When the resin reaches the late rubbery stage, remove it by tugging the
floss handle with a cotton roll forceps along the path of withdrawal.
• Place the resin in a cup of warm water (37° C) for 5 minutes.
• Trim away whatever flash may be present. Return the polymerized resin
to the cavity preparation and adjust the occlusion, using marking film and
a slow-speed handpiece. (Take extreme care to avoid removing tooth
structure.) Leave the floss handle in place as long as it does not interfere
with adjustments of the occlusion.
• Remove the adjusted interim restoration with the floss handle, and put it
aside where it may be found easily after impression making for the
definitive inlay.
• Clean and dry the cavity preparation, and place a thin coat of interim
cement on the cavity walls. Immediately insert the interim restoration.
• When the cement is set, remove the excess with an explorer and a spoon
excavator. Carefully cut off the floss handle with the scalpel blade.
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A floss handle facilitates removal of an inlay
resin interim restoration during late rubbery stage.
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Fabrication
either from pressable
ceramics or
CAD/CAM
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ceramic Inlays and onlays

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