Fig.1
Initial case where an interproximal caries on the mesial of the first molar is programed and the two amalgams are to be replaced due to secondary caries, marginal infiltration and incorrect anatomy. The proximal walls are rather intact before caries removal. This fact has to be copied and reproduced later on.

Fig.2
First of all, and previous to any preparation, a wedge will be inserted between the desired cavities in order to separate the teeth, move the soft tissues away form the preparation site and protect the gingival margins. With the wedge in place, an impression will be taken with a light curing gingival barrier, preferably with a high contrast color. A small amount of the material will be placed in the proximal areas and cured. NOTE: For some time we used not to cure the resin which results rather inconvenient, now is mandatory to polymerize this step.

Fig.3
A sandblasted proximal Ring is placed in contact with the non polymerized material, and yet not polymerized, so the next increment of material can embrace the ring end.

Fig.4
More material is placed to fully embrace the extremities of the ring and polymerized.

Fig.5
The ring is carefully separated from the cavity. Generally the impression material is removed in one piece and without breaking. Accidental excesses that have flowed under or around the wedge should be removed at this point with an abrasive disc. The ring must remain attached to the tweezers slightly opened, otherwise the sharp edges of the impression can touch and break.

Fig.6
Cavities are prepared without removing the wedge and looking to clean perfectly the cavity. after the cavity is completely clean then the wedge can be temporarily removed to be able to place the matrices.

Fig.7
When selecting a matrix we suggest matrices with a pronounced concavity, thin but resistant and as simple as possible. At this stage, the main aim is to obtain a perfect wedging and gingival marginal seal of the matrices. Once achieved we can proceed to the next step.

Fig.8
The ring is then placed between the matrices, as the resin has the previous shape of the initial situation, it will squeeze both matrices to the tooth structure and adapting perfectly to the walls of both cavities in a way that no ring can do in every situation.

Fig.9
Although the matrices may seem to have strange foldings, the shape achieved corresponds to the initial anatomy, and acts as a container for the proximal walls. The problem of the contact points when using two contiguous matrices will be easily solved in a further step.

Fig.10
One of the two proximal walls is constructed with a Body A3 shade and perfectly polymerized. After that, the custom ring is removed and the matrix is pulled out with a strong tweezer, without removing the the wedge.

Fig.11
The custom ring is placed again, the insertion is quite identical so the premolar shape still will be optimal. The contact point will be strong as there is only one matrix separating teeth and the wedging and ring are very strong.

Fig.12
The premolar distal wall is constructed with the same A3 body mass. The composite is condensed very well to fill and adapt perfectly the composite to the margins.

Fig.13
The custom ring is removed, and at this stage is no longer useful and it can be cleaned. The remaining matrix will be removed.

Fig.14
The last matrix is removed in order to have better vision and see precisely the shape of the marginal ridges achieved.

Fig.15
The view of the proximal walls show extreme precision of the boxing stage, where no excess was obtained neither from vestibular or palatal, making so easy the finishing stage.

Fig.16
The cavity can be filled up with small increments of composite in order to avoid contraction. The mass used was the same A3 body. The cavity is intended to be filled up with the same color, a medium translucent mass is easier to polymerize and color is more than ideal with the systematic use of single shades in posterior teeth.

Fig.17
With sectional technique, one by one, every cusp is built up separately, achieving a perfect anatomy of a small section of the occlusal surface and then fixing it by polymerization, then the next cusp can be modeled without altering the other this is repeated for every cusp, until achieving the full occlusal surface. Note in this image how the vestibular cusps are done and the palatals are missing yet.

Fig.18
The whole anatomy already modeled and ready to receive stains.

Fig.19
The stain technique (which will be discussed in an upcoming article) is easy and natural. But most of all reliable, repeatable and allowing the user to avoid the presence of bubbles and flaws.

Fig.20
The premolar with the stain on place. The las polymerization should be long, about a minute in order to achieve a good surface hardness, correct conversion degree and thus quality of the material for long term.

Fig.21
Lateral view pointing out the polishing and the morphology.

Fig.22
Control picture after a month.

Fig.25
4 year control (uploaded on April 2017) Update (July 2017)- MyCustomRings Kit has been released in partnership with Polydentia powered by Styleitaliano, to learn more, follow this link

Bibliography

1. Liebenberg W. Posterior composite resin restorations: operative innovations. Pract Period Aesthet Dent 1996;8:769-778.
2. Pallesen U, Qvist V. Composite resin fillings and inlay. An 11 year evaluation. Clin Oral Invest 2003;7:71-79.
3. Magne P, Dietschi D, Holtz J. Esthetic restorations for posterior teeth: practical and clinical considerations. 1996;Int J Period Rest Dent 2:105-119,206
4. Tjan AH, Bergh BH, Lidner C. Effect of various incremental techniques on the marginal adaptation of class II composite resin restorations. J Prosthet Dent 1992;67:62-6.