Fig.1
Today the limit between partial indirect restorations and full crowns is blurred, so we often choose to restore with an overlay teeth that we would have covered with a full crown just a few years ago. We might also find ourselves removing old crowns and replacing them with large overlays.

Fig.2
In this illustration, you can see the shape of an extensive overlay preparation. The paste composite is placed on the proximal preparation margins (lime green), and flowable composite is spread all over the preparation (dark green).

Fig.3
The restoration is positioned. Once you start pushing it, the paste composite will come out from the proximal areas, the ones where we need the most control, and it will be easy to remove. The flowable composite will come out from the buccal and lingual, leaving a thin layer in between the preparation and the overlay.

Fig.4
So, at the end of the cementation, we will have most of the surface covered in a thin layer of flowable composite, and paste composite only in the proximal cervical margins.

Fig.5
Let’s see a clinical case. First step is isolation with the rubber dam. Then sandblasting and selective enamel etching are carried out. The composite you can see in the picture, outside the margins of the preparation, is a flowable wing.

Fig.6
A universal adhesive is used to bond the surface.

Fig.7
Paste composite is placed on the margins. These increments will prevent the flowable composite from leaking in that area.

Fig.8
The areas where the paste composite is placed are highlighted in lime green.

Fig.9
Then the flowable composite in the central area of the preparation.

Fig.10
The area where the flowable composite is placed is highlighted in dark green.

Fig.11
Lateral view of the tooth just before the placement of the restoration.

Fig.12
The restoration is positioned, and the excess material leaks exactly how we want it to.

Fig.13
Detail of the leakage. Note how only paste composite is in the proximal area.

Fig.14
Occlusal view of the excess composite distribution.

Fig.15
The restoration is pushed to perfectly fit the preparation. It’s now easy to remove the paste composite with a sharp instrument. If a thin layer were used, it wouldn’t go inside the contact point. The thinner, the better. A brush makes it easy to remove the flowable.

Fig.16
Final picture, buccal view.

Fig.17
Final picture, occlusal view.

Conclusions

The Combo cementation combines the advantages of paste and flowable composites. The dual-consistency approach guides the leakage of the flowable, thus making it easier to clean the proximal areas.

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