illustration of composite leakage during overlay cementation Introduction

The Combo cementation. A dual-consistency composite approach.

Combo is a new approach to adhesive cementation. The idea behind it, is to combine composite consistencies to make cementation of indirect restorations easier. In the Combo approach, a small amount of paste composite is positioned on the proximal-cervical margins of the preparation, while flowable composite is spread to cover the rest of the preparation.

illustration of extension of onlay overlay crown preparation

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.

illustration of dual consistency composite onlay cementation

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).

illustration of overlay luting

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.

illustration of cemented 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.

overlay preparation under rubber dam isolation

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.

overlay preparation with bonding agent

Fig.6

A universal adhesive is used to bond the surface.

paste composite on the margins of overlay preparation

Fig.7

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

illustration for positioning paste composite in the combo cementation technique

Fig.8

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

flowable composite positions for overlay cementation

Fig.9

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

illustration of the combo cementation technique

Fig.10

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

dual-consistency composite for overlay cementation

Fig.11

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

composite leakage during overlay cementation

Fig.12

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

proximal composite leakage

Fig.13

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

occlusal view of overlay during cementation

Fig.14

Occlusal view of the excess composite distribution.

buccal leakage of flowable and paste composite during overlay cementation

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.

cemented overlay on lower molar

Fig.16

Final picture, buccal view.

overlay partial restoration on lower second molar

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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