Guide the enamel with dentin

This technique is intended to highlight the importance of the enamel thickness, which without a doubt is the factor that determines the success of an esthetic restoration.

Balancing the thickness of dentin and enamel in any material always determines the color, opacity and translucency of a tooth. It would be ideal to be able to generate buccal walls as the first step of any direct restoration (this is a very important reason of why veneers integrate so well), unfortunately this is technically difficult and inaccurate, especially for the day-to day dentistry.

Fig.1

This image shows they secret of aesthetic restorations, the 0.5 mm space for the composite enamel, unfortunately difficult to understand and then difficult to generate. And the explanation of why this is difficult is because the last layer of enamels is directly affected by the underlying dentin mass, meaning that if the dentin amount is poor, the enamel layer will be very thick and thus gray, and with a low value. On the contrary if the dentin layer is too much, the enamel layer will be very thin and the restoration will be very opaque… all of this especially affects the margin area.

old composite restoration upper left incisor resin light curing transparent silicone index direct mamelons stratification cast model dentin mass layering enamel impression prepared cavity

Fig.2

An old unaesthetic restoration was scheduled to be replaced. A new easy method to construct an enamel wall with an exact thickness will be proposed during the explanation of this clinical case.  The first step will be, with a flame bur, to draw a very thin line where the margin is visible, to be able to take an alginate impression and locate the margin.

Fig.3

The model is poured  and cut in the lab according to the line we marked before. A wax-up of the dentinal core is carried out, and with a caliper the technician will measure that the thickness between the enamel area (stone) and the dentin area (wax) has a step of 0.5 mm in the margin area. Mamelons are copied to achieve a more natural restoration.

Fig.4

Everything is going to be registered in transparent laboratory silicone, which is very precise and elastic. A second impression will be taken to the full wax up (with the enamel area already waxed), preferably on a second model.

Fig.5

The first silicone key will be used as it is obtained, the second one will be cut in half in order to obtain a vestibular key and a palatal key. Once we get the wax-up back from the laboratory  and the silicone keys, we can proceed to remove the old restoration, polish the margins and carry out the bonding procedures.

Fig.6

The dentin impression will be filled up with a dentin composite (opaque and chromatic) in this case an A3 dentin was used. The silicone is placed in the preparation making sure that there is enough material contacting the tooth but not too much to create excess. If some of this happens, the silicone can be removed before curing to be filled up with more material or some excess can be removed. Once we are sure of the dentin contacting the tooth we cure for 20 seconds, remove the silicone carefully.

Fig.7

And we cure again without the silicone. The dentinal core must look exactly as the wax-up, some corrections can be performed, as covering a small bubble.

Fig.8

With the second set of silicones, the palatal wall will be stamped, only being careful of not touching the contact points.

Fig.9

The enamel is placed in the silicone key, stamped on the tooth and polymerized for 20 seconds.

old composite restoration upper left incisor resin light curing transparent silicone index direct mamelons stratification cast model dentin mass layering enamel impression prepared cavity

Fig.10

The proximal walls are modeled with the aid of matrices and wooden wedges. Before placing the last layer, some white effects are placed imitating the neighbor tooth.

Fig.11

The final enamel layer can be placed manually or stamped with the last silicone, only if the silicone fits perfectly.

Fig.12

The last layer stamped and polymerized before the silicone was removed.

Fig.13

For the final Stages, the restorations was polished according to the morphology of the adjacent teeth. The final case after one week shows an optimal integration in color, shape, margin and surface.

Conclusions

Notice how only using three masses (one dentin, one enamel and one white effect) all the natural features can be achieved, this integration happens because of the enamel-dentin ratio. Any practitioner who acquires the ability to understand and model the dentins with the aim of leaving the exact space for the enamel will certainly succeed most of the times when stratifying.

Even though this case is a solution for selected cases, is presented here with the purpose of understanding the importance of the enamel-dentin thickness in aesthetic restorations.

This knowledge avoids improvisation and links the every day dentistry to a protocol and therefore a success on regular basis.