A young 19-year old girl presented with a fractured UR6 buccal cusp and a defective occlusal amalgam restoration.
After a full examination, it was evident that over two thirds of the tooth had been affected by secondary decay. The patient wanted her tooth to be restored with a natural looking restoration that would not only look good for many years but also last a long time.
After discussing all treatment options with the patient, a CAD/CAM all-porcelain onlay was chosen to restore the UR6.
The patient was not only amazed by the efficiency of the manufacturing of the Cerec restoration (using Cerec AC’s Bluecam), but also by the seamless aesthetic integration of the final restoration.
The old amalgam restoration and secondary decay was conservatively removed and the mesio-buccal cusp was assessed.
It was decided to extend the onlay over the mesio-buccal cusp but leave the unaffected palatal cusps unprepared. After the preparation was complete all margins were smoothed with a white stone bur.
Smooth margins are essential to ensure successful location of the margins using the Cerec AC system, thus producing a restoration with excellent marginal adaptation. Due to the excellent aesthetic integration of the Cerec restorations, all margins were kept supra gingival and minimal tooth preparation was required.
Optispray opaquing agent was applied to the UR6 and adjacent teeth, which facilitates the optical impression process. A 3D digital impression was recorded with the Cerec AC’s Bluecam camera. This is simply recorded by the dentist chairside in less than 20 seconds by positioning the camera over the prepared and adjacent teeth and slowly moving the camera distal to mesial over the arch. The Bluecam camera doesn’t require any foot pedals to capture an image; instead an automatic shutter instantly captures the digital impression without user intervention.
Designing the restoration
After the digital impression has been acquired, a similar digital impression is recorded of the opposing arch and then a scan of the prepared tooth in occlusion is recorded. This now produces three scans, which is enough information to create a functional, aesthetic restoration.
After confirming the buccal registration correlation, the margins can be automatically marked on the digital impression of the UR6. Once the clinician has confirmed the margins, the Cerec AC system automatically produces an onlay restoration proposal for the UR6. The automatic proposal and design of the restoration is based on the system’s comprehensive biogeneric database of human tooth morphology, in this case, no adjustments were required.
To ensure a proper occlusal profile, the systems unique bite registration ‘virtual grinding’ feature was activated to set occlusal contact strength to precisely the dentists desired preference.
Milling and fitting
Once the designing process is complete, the UR6 onlay was milled in a MC XL milling unit in under seven minutes from a solid block of all ceramic A2 Vita Mark 2 CAD material.
After trying the restoration in and checking the occlusal contacts, the connective sprues were removed with a grinding wheel.
Finally, to turn the porcelain onlay into a poly-chromatic natural looking restoration, a single stage stain and glaze crystallisation process, using vita Akzent Stains, was completed.
Before final cementation, the UR5 was protected with PTFE tape to ensure no unwanted excess cement was bonded interpoximally. The tooth and fitting surface of the onlay were mechanically etched with a chair side Microetcher II containing Cojet (30-mm silanated ceramic particles). Sandblasting is essential to remove the aprismatic enamel and provide a meticulously clean surface prior to acid-etching and adhesive application.
A 35% phosphoric acid was used on the enamel for 15 seconds and rinsed off. A thin layer of a dentine-desensitising agent (Gluma) was applied along the exposed dentine surface to reduce post-operative sensitivity.
After careful air-drying to leave a moist dentine surface, a thin layer of bonding agent (Optibond Solo) was applied to all surfaces of the UR6 and light cured for 30 seconds.
The porcelain onlay-fitting surface was then prepared with 9% hydrofluoric acid for 60 seconds, wash and dried, and to clean any excess contaminants 35% phosphoric acid was applied for 20 seconds and washed and dried. A freshly mixed silane was mixed and applied to the fitting surface and left to air dry for 60 seconds.
Finally a thin layer of wetting resin was applied to the fitting surface (Optibond 2FL).
NX3 Nexus third generation dual cure dental cement (Clear) was used due to its excellent bond strength and colour stability.
A dental probe and floss was used to ensure all excess cement was removed after an initial ‘tack cure’.
After completely light curing the restoration (according to manufacturers recommendations), interproximal contacts were checked and cleaned with an ultrasonic scaler if necessary.
The patient was extremely happy with the final aesthetics of the restoration and within an hour her tooth felt ‘as good as new again’.
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