Inlays and Onlays
Dr. G. V. KRISHNA MOHAN,
Reader in Department of Prosthodontics,
came back in modern dental history in late
ninteenth century as an esthetic means of restoring carious
Unfortunately the use of porcelain inlays was halted by too
high failure rate because of poor marginal fit and the easily
wash out conventional cement.
– Porcelain inlays tentatively reintroduced in 1980s as a
result of several technological developments:
advances made in refractory investments.
the use of silane coupling agents.
the use of composite resin cements.
improved bonding technique.
Case selection determines the medium or long term
success of ceramic inlays/ onlays.
Case selection can be done on
basic rules like:
To be indicated for
medium –level damage to
vital molars & premolars.
Must be prepared to leave
an outer enamel margin for
Prepared margins must
never coincide with occlusal
contacts as it is a root cause
of medium term failures.
extensive unsupported over hangs must be avoided
because it may lead to fractures.
contraindicated in parafunctional activity.
ease to access the cavity for preparation, making
impressions and bonding.
contraindicated in short clinical crown.
Modifiable adverse clinical conditions
Certain adjustments can often improve status of tooth
making ceramic inlays /onlays as a viable option like
A very DEEP CAVITIY with insufficient remaining dentin
thickness <0.5 m.m can be dealt with using a calcium
hydroxide lining as a pulpal dressing and covered with resin
modified glass ionomer cement.
SUBGINGIVAL MARGINS may be dealt with by partial
gingevectomy, thus rendering them supragingival for
impression making and bonding
Ceramic inlays or onlays ???
prefer to prepare an inlay cavity in view of the cuspal
reinforcement effect by bonding
prefer to cuspal overlay in clinical situations like;
• margins located away occlusal contacts, on the labial
and lingual surfaces.
• esthetically onlays are superior
and more reliable seal.
Both inlays /onlays differs from that of cast metal onlays/
inlays due to properties of ceramics.
Following modifications to a conventional inlay
for ceramic inlays are:
a proximal cavity with no
slice cut or bevel edge.
axial walls with a roughly
10 degrees angle of taper.
rounded internal line angles.
the base of the main cavity should be flat.
occlusal margins may not coincide with occlusal
margins should be prepared to a 90 degree
cavosurface line angle; alternatively they should
present a hallow ground chamfer in an attempt to
create an ‘invisible’ margin.
Cuspal overlying should allow a clearance of at least 1.5mm
All cuspal angles should be rounded and margins should
consist of a shoulder with a rounded internal line angles or
Tapered round-end diamond instuments and olive-shaped
or sperical instrument designed for hollow ground
chamfer are used for inlays and onlays .
Fabrication of inlay/onlays
IMPRESSION MAKING AND DUPLICATES
Impressions of supragingival cavity preparations
made with hydrocolloids or silicones. Addition silicones are
material of choice.
Fabrication of ceramic inlays/ onlays often requires
preparation of duplicate dies of refractory material. Usage of
addition silicones aids in accurate duplicate casts.
Temporization is an indispensable stage ,oversight here can
affect pulp and/ or final adhesion of ceramic restoration.
Best solution consists of direct, chair side creation of light –
cured resin inlays/ onlays after lubrication of teeth. After
trimming and adjusting the margins and occlusal contact
sites resin inlay luted with eugenol free temporary cement
Try in allows the fit of the inlay or onlay to be tested.
This stage requires care and accuracy owing to the
fragility of the ceramic retorations prior to bonding.
The inlays / onlays are inserted using a small globule of
wax of low melting point attatched to a plastic instrument
handle ,or using a placing instrument such as ACCUPLACER, HU-FRIEDY.
Both try in and bonding are facilitated if a vertical
stabilization groove has been incorporated in
Adjustments of interproximal contact areas, and any
areas of friction on internal surface should be done.
A sheet of carbon paper may be used for detecting the
contact area or better still proximal surface can be
stained with pillar-box red dissolve in chloroform.
Corrrection should be carried out slowly ,using
aluminous silicone wheels or cups.
FRICTION ON THE INTERNAL SURFACE
A white silicone fluid (FITCHECKER,GC) is used for
detection of discrepancies and adjusted with red-banded
medium speed diamond instruments.
Not recommended to check occlusal contact prior to
bonding ,causes fracture of inlay/ onlay .
If necessary to check a silicone fluid
film(MEMOSIL,BAYER) should be used to soften occlusal
CHOICE OF CEMENT
If the inlay/ onlay >2mm thickness the cement of choice
will be dual cure resin cement.
If >3mm thickness the cement of choice is
autopolymerizing resin cement.
Resin cements should be used in conjugation with
appropriate dentin –enamel adhesives.
CHOICE OF COLOR OF CEMENT
The choice of resin cement color is an important
Considering the thickness of restoration, some prefer luting
cement to be only faintly coloured and translucent enough
to bring out the natural color of dentin and enamel.
This takes into account try in pastes are used to match with
VISCOCITY OF CEMENT
Microfilled composite cements are used previously because of the
fluidness and fineness of the cement layer but medium term
breakdown ,wear and hydrolysis occurs at weak point of inlays/ onlays
bonded with cement .
So highly filled and viscous microhybrid composite cements are used
for bonding . As it is less fluidic requires ultrasonic placement.
The more accurate the margins the smaller the thickness devoted to
the composite cementend the more marginal defects will be.
The accuracy of investments and refinements of ceramics and
composite cements permit mean thickness values of 0.05 nanomicrons
Margin failure results from:
Wear and loss of the composite
Insufficient thickness of ceramic
Microscopic cracks in the ceramic
Microsropic distortion of the margins due to
concentration of stress
Coincidence of margins with functional occlusal
QUALITY OF ADHESION AND SEAL
Adhesion and seal are certainly associated ,but can evolve
completely independently of each other. Both can effect on
the success of inlays/ onlays.
Debonding occurs due to marginal leakage from a defect of
the margin ,such as splitting , wear at the interface a poor fit
etc, or from a cervical margin bonded onto the dentin or
Rubber dam application
Removal of provisional inlays and cavities are cleaned with hand
instruments, with ultrasonic instruments and finally with air-powder
abrasive device to remove contaminants and temporary cement.
Best for luting is usage of single-component enamel-dentin adhesive
and dual cure luting composite.
Inlays/ onlays while sandblasting are protected externally by wax
Internal aspect of inlay/ onlay is etched for 90 secs with10% of HF acid ,
rinsed in running water dried and silanated. After evaporation of the
silane ,primer is applied and light cured.
Tooth surface first disinfected with chlorexidine gel, dried and etched
with all etch technique. Two thin coats of one-step primer applied and
Composite mixed and applied onto preparation, inlay is inserted and excess
cement is removed with brush and dental floss.
Inlay is secured in position and light cured for 1 min, small excesses can
removed with bade and more excesses is removed with fluted bur.
After cleaning and checking the occlusion one important step before
polishing ,namely sealing the margins and surface of the restorations.
For that purpose all accessible limits are etched for 10 sec, rinsed ,dried
,impregnated with a liquid resin and light cured for 20 seconds.
BLOCKING TUBULES WITH PROTECTIVE HYBRID LAYER and SEALING THE
MARGINS AND SURFACES are two very important steps for acheiving
Finally polished with silicone cup disks and lustered with diamond paste on a