Optimising design and shade—replacement of a resin-bonded bridge for aesthetic reasons

A patient with high aesthetic demands

A patient in his early twenties presented for consultation with a purely aesthetic concern. He had been wearing a double-retainer resin-bonded prosthesis (Fig. 1) for several years, placed owing to the congenital absence of the mandibular central incisors. Although the bridge had served him well functionally, the patient now wished to have it replaced with a more aesthetic solution that better matched the shade of his natural teeth.

After clinical and radiographic assessment, several treatment options were considered, taking into account the patient’s age, bone volume and aesthetic expectations. The final decision was to fabricate a new resin-bonded bridge, optimised in terms of both design and shade, using a multilayered zirconia to achieve a natural-looking result.

Preliminary steps in the dental office

A pretreatment impression of the bridge was taken before its removal, using the iTero Element 5D Plus intra-oral scanner (Align Technology; Fig. 2). These pretreatment scans, which are performed almost routinely for our prosthetic reconstructions, allow the laboratory to capture the volume of the existing prosthesis, replicate the shape (if suitable) and often visualise wear facets. This helps minimise or even eliminate the need for subsequent adjustments. The existing resin-bonded bridge was then removed, and the abutment teeth were prepared as minimally invasively as possible. Once again, the intra-oral scanner was used to take an impression of the situation (Fig. 3).

Production of the resin-bonded bridge

The scan was sent directly from the intra-oral scanner to the design4me platform (DIGISMILE) to carry out the digital design of the planned bridge (Figs. 4 & 5). A repositioning key was also designed by the dental technicians to provide for accurate seating of the bridge during cementation (Fig. 6). The material of choice was KATANA Zirconia YML (Shade B1; Kuraray Noritake Dental), a multilayered zirconia, owing to its outstanding physical and aesthetic properties—specifically its gradient in shade translucency and flexural strength (Fig. 7).

The production centre, DIGISMILE, subsequently received the STL files of the bridge and the positioning key, modelled by the dental technicians on the design4me platform (using exocad), ready for milling and printing. The laboratory was also provided with intra-oral photographs to replicate the surface texture, possible characterisations and shades. The bridge was milled using a DWX-52D milling machine (Roland DG). Polishing, surface finishing and staining were carried out using burs (Komet Dental) and MiYO liquid porcelain (Jensen Dental). The repositioning key meanwhile was 3D-printed with a NextDent 5100 printer (3D Systems) using surgical guide resin (Fig. 8).

Definitive placement in the dental office

The adhesive cementation procedure is one of the most critical steps of the whole workflow. Once the bridge had arrived in the dental office and try-in was successfully completed, the focus was on moisture control and the establishment of ideal bonding conditions. In this regard, strict isolation of the working field with saliva ejectors, cotton rolls and ideally a dental dam is essential, followed by pretreatment of the abutment teeth and of the retainer wings of the bridge.

Treatment outcome

Thanks to the pretreatment scan and the overlay of the old bridge with the new one, no adjustments were necessary, although occlusion checking remained essential. At a recall after 18 months, gingival integration was satisfactory: the patient was able to use interdental brushes and maintain the prosthesis properly (Figs. 11 & 12).

Conclusion

In this clinical case, the choice to produce a double-retainer resin-bonded bridge almost identical in design to the previous one may seem conservative. However, this decision was supported by several factors: the patient’s good tolerance of the previous prosthesis, the tissue integrity of the abutment teeth and, most importantly, the opportunity to significantly improve aesthetics thanks to advances in materials and bonding techniques, allowing us to keep preparation minimal.

The new bridge, designed with highly aesthetic multilayer zirconia and bonded using a strict protocol, achieved a perfectly integrated and natural result without the need for more invasive options (therapeutic gradient). Furthermore, this approach invites the restorative team to consider emerging trends in resin-bonded bridge design, notably the option of two single-retainer cantilever bridges, which might be considered in similar cases in the future.

This case highlights the importance of individualised treatment planning, which does not rely solely on innovation, but on precise clinical assessment, attentive listening to patient needs and expectations, careful implementation of available tools, and the use of high-quality materials and protocols.