This article presents a case of aesthetic restoration of anterior teeth using KATANA Zirconia Ultra Translucent Multi Layered (UTML; Kuraray Noritake Dental) complete anatomical crowns, with vestibular stratification, and the biologically oriented preparation technique (BOPT).
Everything Kuraray Noritake
The patient requested a solution for an aesthetic problem due to the unnatural look of her old restorations and black triangles from a past history of periodontitis. The resulting retraction of the tissue had left the margins of the prostheses clearly visible, and the loss of the papilla peaks, together with the numerous black spaces between the crowns, required a complex therapeutic approach (Fig. 1).
The treatment plan for the periodontal problems consisted of a non-surgical approach, with scaling and root planing, and the replacement of the old fixed prostheses to recondition the marginal tissue and facilitate the restoration of a new, aesthetically pleasing gingival architecture (Fig. 2).
From a functional point of view, we decided to reduce the deep frontal bite to restore a correct overjet–overbite ratio. This reduction was also important from an aesthetic point of view, as it allowed us to shape the teeth correctly (Fig. 3).
We usually remove old prostheses before beginning a periodontal treatment and make a provisional restoration to create an environment in which the soft tissue can heal. If we have to work beyond the cementoenamel junction, we prefer a vertical preparation for abutments, and the purpose of the provisional restoration is to condition the marginal tissue using the BOPT by Dr Ignazio Loi (Fig. 4).
For the BOPT, the vertical preparation of the abutment has a finishing line that extends into the gingival sulcus. The temporary conditioning of the tissue induced by the provisional prosthesis allows us to modify the level of the gingival parabolas to a certain extent (Fig. 5).
Healing of the tissue one month after the initial periodontal treatment was significant (Fig. 6). The role of the provisional restoration, appropriately realigned, is crucial for obtaining healthy soft tissue around future restorations. The conditioning of the tissue was achieved by means of the provisional restoration, which modified the level and shape of the marginal tissue. Once filled with correctly fitted crowns, the interproximal spaces would be further reduced after the definitive restoration.
The correct management of the provisional restoration is crucial for the healing of the tissue. The placement of a provisional restoration before the periodontal therapy allowed us to create the right environment for complete healing. At the same time, the vertical preparation allowed us to gradually condition the marginal gingival tissue by shortening or lengthening the provisional restoration as necessary (Fig. 7).
One of the advantages of a vertical preparation is that taking the final impression is easy, because the absence of a horizontal finishing line greatly simplifies the procedure (Fig. 8). However, the BOPT also requires the taking of an impression of the subgingival portion of the preparation. The dental technician will have to decide on the marginal shape of restorations according to the position of the gingival marginal in consultation with the clinician and based on the tests conducted with the provisional restoration.
After the casting of the model, we prepared the gingival area to accommodate an ideal configuration of the gingival parabolas (Fig. 9).
After making a wax model, we assessed whether the height of the gingival zenith could be further corrected. Figure 10 shows that the gingival level of tooth #21 was not yet ideal, so we stretched it distally.
Once the wax model was complete, we extracted the tooth from the model and evaluated its protrusion. It was only after joining the gingival protrusion to the arbitrary margin of the preparation that we proceeded to a scan and milled the crowns (Fig. 11).
The restoration was carried out with KATANA Zirconia UTML based on the new formulation of cubic zirconium oxide. This ultra-translucent material was chosen because we were working with light and non-discoloured abutments (Fig. 12).
We finished the crowns on a positional impression to help to improve the gingival adaptation; we had some dispersion of the tissue in the first precision impression due to the use of retractors. We finished the crowns with CERABIEN ZR FC Paste Stain colours and glaze (Kuraray Noritake Dental; Fig. 13).
The surface colours and the slight contrast created are highlighted in this black and white image taken with a blue filter (Fig. 14).
In Figure 15, we can see the natural translucent effect of KATANA Zirconia UTML and the invisible fusion between the abutments and crowns.
Figure 16 shows the clinical situation one year after cementation, performed with PANAVIA V5 (Kuraray Noritake Dental): the marginal tissue was in a good clinical condition, with no signs of inflammation or bleeding. The BOPT allowed us to optimise the level of the gingiva without resorting to periodontal surgery, while the shape of the new crowns made it possible to close all the interproximal spaces for an optimally aesthetic result.
The brightness of the restorations (thanks to the use of a particularly translucent zirconia) combined with the shape of the incisors, greatly improved the aesthetics of the restoration, even though the initial situation appeared to be particularly unfavourable (Fig. 17).
Compared with the previous prostheses, the incisal reduction allowed not only for the optimisation of the functional phase by reducing the overbite, but also made it possible to achieve more natural aesthetics, the contour of the incisal margins following that of the lower lip.
Figure 18 demonstrates the excellent aesthetic properties of KATANA Zirconia UTML and the perfect integration of the prostheses in harmony with the pink tissue.
Editorial note: A list of references is available from the Publisher. This article was published in CAD/CAM―international magazine of digital dentistry Vol. 11, Issue 1/2020.