Fig.1
In a quick analysis of the initial situation, the tooth 26 has inappropriate restoration in terms of the modelling and the outline of the cavity. This indicates a bad harmony between the tooth and the restoration. Also, clinically and radiographically, it is clear that the secondary caries were placed in the margins of both teeth (26 and 25). All in all, all variables must be taken into consideration to know how to remove the old restoration, the caries, and how to design the cavity and restoring both teeth (26 and 25).

Fig.2
First key to get a good visualization of a perfect cavity design is the rubber dam isolation. It is important to understand that the idea of the isolation is not only the placement of a rubber dam sheet, but also the well positioning of the rubber dam in order to isolate and protect the soft tissue.

Fig.3
After isolation, the cavity preparation was done using a (D2) bur from STYLE DIRETTO kit (Intensiv, Switzerland). This bur is a diamond straight bur with rounded end. Further, it has the dual function of removing the old composite, and shaping the cavity, especially the geometry of the enamel walls.
As it is known for composite restoration, the walls should be almost right angle (the cavosurface angle), and the internal line angles should be rounded. This can be happened when this bur enters the cavity perpendicular to the floor.

Fig.4
After removing the old composite from the tooth, the obvious caries is located underlying the composite restoration. It is better to remove the dentin caries by the bur (slow speed carbide bur) that generated less smear layer.

Fig.5
The caries were now removed using a carbide rounded bur. It is essential to note that the slow speed carbide rounded bur, comes in 3 sizes starting from the smallest to the largest (D3 – D4 – D5) when using the STYLE DIRETTO kit. According to the size of the cavity and the extent of the lesion, the size increases.

Fig.6
One of the important rules for class 2 cavity preparation is the opening of the contact with the adjacent tooth. For this purpose, it is decent to use the flame bur (D6) for moving the proximal margins outside the contact point area.

Fig.7
In case there are caries near to the enamel where no vibrations are needed, it is wise to use the medium-fine grit rounded bur (D7).
It is so common (in class 2 cases) to face irregular cervical margin which sometimes has chalky enamel (decalcified enamel). So, it is important to flatten this part and to remove the decalcified enamel without hitting the adjacent tooth.

Fig.8
For flattening the cervical margin, it is better to use a tip called cutting surface bur (D8), making easy to position the bur in the cervical margin without hitting the adjacent tooth structure.

Fig.9
The view of the tooth after finishing all the steps of the cavities preparation. It is crucial to mention that by using the correct sequence of the burs, a clean cavity will be obtained and will be ready to receive a good adhesion with a good matrix to recreate the margins.

Fig.10
Choosing the correct matrix (according to the contour, height, and thickness) is very important. In this case, a back to back technique was done to have a smooth and a functional contact. By doing so, all matrices were placed at one time, next, the wall of the first tooth was restored, then one matrix was removed, and then the wall of the second tooth was built to have a good contact point.

Fig.11
View of the restorations after the finishing and polishing procedures. In this situation, the modeling was done using the P CompoSite by White Dental Beauty and the Espresso posterior technique (FMT as described by Hardan – Akhundov et al.,)

Fig.12
Occlusal contact was checked. In addition, the high spot was eliminated, then a final polishing was done to create a healthy and functional restoration.

Fig.13
2 months follow-up showed a good harmony of the restorations with the tooth structure.

Conclusions

Following the correct sequence in direct composite restorations, will prevent falling in big mistakes that will destruct the structure of the tooth.
Using good burs with sequence, will give the advantage of having a perfect cavity design that will help in getting longevity for the daily posterior restoration.
In this case, the P CompoSite used for restoring the cavities with the help of STYLE DIRETTO kit for preparing the cavities, marked a good outline for a better harmony of the restoration with the tooth structure.

Bibliography

1. Walter Devoto 2022. Good practice in minimal preparation. How to get your patient and technician what they need (Walter Devoto 2022 \ styleitaliano.org.)
2. Marchetti G. 10 TIPS on Posterior direct restoration in daily flow. 2018. Styleitaliano.org
3. Manauta J, Salat A. Layers, An atlas of composite resin stratification. Quintessence Publishing Co; 2012.
4. Hardan L, Sidawi L, Akhundov M, Bourgi R, Ghaleb M, Dabbagh S, Sokolowski K, Cuevas-Suárez CE, LukomskaSzymanska M. One-year clinical performance of the fast-Modelling bulk technique and composite-up layering technique in class I cavities. Polymers. 2021 Jun 4;13(11):1873.