CAD/CAM chairside anterior crown using CEREC 3D
A single unit anterior crown in a young female has always been a challenge to restore. We have now been using the CEREC 3D for four years, and with constant improvements in the software and materials available we have been able to increase the range of applications with some innovative techniques.
Below is a case study of a 25-year-old dental nurse who fractured her central incisor while surfing (Figure 1).
Vitality was normal and there was no pulpal involvement. Radiographs showed no root fracture. The fractured portion was lost.
Initially we made a provisional crown with a three colour porcelain block (Vita Mark 11 Tri-colour 1M1 1M2 1M3) prepared, imaged, designed and milled on the same day with no surface characterisation (Figure 2).
Following this we used a home bleaching technique (Optident 15% over six weeks wearing the close fitting tray for two hours a day) to increase the value of the natural dentition prior to final restoration.
This was then prepared with a rounded chamfer 1mm preparation with supra-gingival margins (Figure 3) and imaged intra-orally, including the UL1, to give us the preparation model and the ‘copy’ model.
The margins of the preparation can be kept within enamel (Figure 2), allowing for improved bonding and a supra-gingival margin that will aid better finishing and maintenance of the interface between the final porcelain and natural tooth structure.
The margins of the virtual preparation are then defined under magnification (Figure 4) and the software allows the shape of the UR1 to be mirror-imaged (Figure 5) and super-imposed onto the virtual model of the UL1 (Figure 6). This will create an exact duplicate of the UL1, which can be manoeuvred and modified to ensure ideal contact points are created and the buccal profile blends harmoniously with that of the neighbouring teeth.
By altering the transluscency of the virtual crown (Figure 7) and using the scrolling ‘cut’ feature in the software, it is also possible to ensure that adequate thickness of porcelain is allowed for and adjusted if necessary.
Minor alterations of the surface morphology can be included to achieve a final result that blends with the shape of the neighbouring UR1, and to ensure suitable emergence profile and surface morphology.
This is then milled at the same visit, polished, characterised with Vita stains and furnace checked with a coloured try-in paste and cemented with a protocol as for cementation of a traditional veneer.
With translucency similar to natural enamel, the light transmission through the finished restoration is unimpeded by a core structure and should best be described as a 360º veneer.
Radiologically the cementation will show as a white fine line and any subgingival flash can be removed. It also allows for easy long-term monitoring of any change.
So, a two-hour visit, one injection, no impressions, no second fitting appointment, no lab fee and a result to be pleased with.
Computerised technology can help us to provide a service to the patient that is to the benefit of both the practice and patient alike.