Ceramic Inlays and Onlays

Presented by,Dr. G. V. KRISHNA MOHAN,

Reader in Department of Prosthodontics,SSCDS

INTRODUCTION

CERAMIC INLAYS came back in modern dental history in late ninteenth century as an esthetic means of restoring carious leisons.

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

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 reliable seal.

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 conditionsCertain 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.

Tooth preparation Both inlays /onlays differs from that of cast metal onlays/

inlays due to properties of ceramics.

INLAYSFollowing 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.

an enlarged isthmus (not <2mm wide).

rounded internal line angles. the base of the main cavity should be flat.

occlusal margins may not coincide with occlusal contacts. 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.

ONLAYS Cuspal overlying should allow a clearance of at least 1.5mm

preferably 2mm. All cuspal angles should be rounded and margins should

consist of a shoulder with a rounded internal line angles or deep chamfer.

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 are

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.

TEMPORIZATIONTemporization 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

TRYIN 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 ACCU-PLACER, HU-FRIEDY.

Both try in and bonding are facilitated if a vertical stabilization groove has been incorporated in preparation

Adjustments of interproximal contact areas, and any areas of friction on internal surface should be done.

INTERPROXIMAL AJUSTMENTS

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 impact.

cementing

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

consideration. 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 tooth.

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.

MARGINAL FIT 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

contact sites

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 cementum.

Clinical bonding procedures

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 light cured.

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 excellent bonding.

Finally polished with silicone cup disks and lustered with diamond paste on a prophylactic cup.

Thank You for Listening