Clinical Continued »
Consequently there is no guarantee with respect to enamel preparation.
The indirect technique The logical evolution of all these concepts was put forward by G. Gürel in 2003: it combines the idea of minimum reduction while considering the volume of the final restorative shape, and also the use of specific burs that make a controlled penetration possible. This tech- nique is based on a simple but rigorous procedure ensuring a high level of reproducibility irrespective of the clinician.
Clinical procedure Phase one: aesthetic analysis and wax-up Smile analysis is an indispen- sable prerequisite for any planned aesthetic restoration. It is based on several well-defined criteria. The changes envisaged are illustrated by modelling with composite resin, applying it directly to the dry tooth without the use of an adhesive (Figs 3 and 4). Once the desired modifications
have been agreed upon (form of teeth, diastema closure, etc), an impression will enable the dental technician to make a more detailed wax-up using a study model (Figure 5). Based on this model, a rigid matrix can now be made either by using thermoforming or with a silicone impression.
Phase two: making the mock-up
Fig 9
Fig 10 Fig 11
The mould is filled with a composite resin (e.g. Luxatemp Star, DMG) and inserted over the patient’s teeth until polymerisation is completed. To avoid clogging up the instruments, it is recommended to use a bis-acryl resin for this mock-up and not a conventional powder/liquid system. Once in place, the matrix
will indicate the final restoration and should be left on the teeth as a guide during preparation.
Phase three: a minimally invasive preparation through the mock-up Depending on the material chosen, the thickness of the restorative material should determine the diameter of the bur and thus the depth of penetration. Once
Figs 9 to 11: The remaining parts of the mock- up are removed and allow the practitioner to get a clear view of the guiding grooves. Prepa- ration will continue until the coloured grooves are completely removed, and completed within the proximal zones in accordance with the aesthetic needs. The impression can be used again, when filled with bis-acrylic resin (Luxatemp Star, DMG), in order to make the provisional restorations
determined, the horizontal grooves are cut into the labial surface ensuring a penetration parallel to the surface, until there is contact with the smooth part of the chuck on the resin of the mock-up (Figure 6). Once these labial grooves
have been made, the occlusal reduction should be undertaken before removing the mock-up (Figure 7). To visualise the depth limit for the preparation better, the bottom of each groove can be highlighted with a pencil or felt tip marker (Figure 8). The mock-up is removed
leaving only the coloured grooves (Figure 9). These are then joined together and the final preparation
Continued »
Fig a Figs a-e: The cutting sequence of the procedure:
The resin mock-up in place over the prepared teeth (a). The depth of the grooves do not depend only on the diameter of the bur, but also on the aesthetic template (mock-up) used (b,c). Once the mock-up is removed, the depth of the guide grooves varies (d). It is now possible to finalise the preparation by joining the bottom of the grooves (e). The enamel layer is preserved better and the thickness of the ceramic veneer is standardised
62 Scottish Dental magazine
Fig b
Fig c
Fig d
Fig e
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