Zirconium oxide meets sintering metal

By DMT David May

Many patients desire fixed implant prosthetic solutions that calls on the creativity of the dental technician in terms of the type of restoration and its cost, which must not be exorbitant. In this article, DMT David May, presents a concept for generating CAD/CAM-guided implant-supported dentures that are both aesthetic and cost-effective.

Prologue

In the age of implantology, more patients are presenting themselves in dental practices with a desire for fixed dentures. They long for a better quality of life and wish for a carefree smile.

At the time our patient consulted the practice, she had been provided with a telescopic prosthesis in the maxilla, which had been converted into a full denture.

Her ultimate wish was to be provided with fixed, functional dentures that can meet her high aesthetic demands.

Such functional prosthetic rehabilitation requires well thought-out therapy planning. The patient’s wishes were summarised and implemented together with the treating dentist.

The individual digital and analogue work steps are documented in the following case study.

The patient first came to us when she had already received six implants in region 11, 13, 16, 21, 23 and 26. During the healing phase, she wore her telescopic prosthesis, which had been reworked to a full denture.

Screw-retained temporary restoration on implants

In the following step, the patient was prepared for the final work with a screw-retained temporary denture. An occlusally screw-retained bridge was to be fabricated for the final restoration.

For the occlusal screw connection, we used Medentibase abutments from Medentika, which are offered by Amann Girrbach.

The conical titanium bases and bonding bases enable the fabrication of multi-pontic screw-retained bridge constructions on implants. In addition, they allow compensating small divergences.

Medentika’s Medentibase abutments are available in five gingiva heights to ensure optimal adaptation to the vertical implant position and the emergence profile.

After a thorough functional analysis, we began with the fabrication of the long-term temporary restoration.

An aesthetic tooth set-up was created on an individual acrylic base. This already came close to the patient’s expectations.

As bonding bases had been incorporated into the acrylic body, the aesthetic set-up could be screw-retained firmly in the mouth and, in a further step, the function and aesthetics could be checked conclusively.

Before the CAD/CAM-supported manufacturing process, the patient’s minimal requests for changes were accepted.

With the finished tooth set-up, which then acted as our blueprint for the final restoration, we began the CAD/CAM-supported planning and fabrication process.

Firstly, the aesthetic set-up was scanned and fully anatomically milled from acrylic.

We used the Ceramill Temp Multilayer acrylic blank (Amann Girrbach) which is approved for long-term temporary restorations.

As the shade layers of the blanks are modelled on the structure of natural teeth, only minor corrections had to be made.

The gingival region was overlaid with gingiva-coloured, light-curing composite.

Finally, the adhesive caps were worked in so that the temporary denture could be screwed to the titanium bases in the mouth.

With this screw-retained, temporary bridge, our patient enjoyed her new outlook on life for about three months.

The extension of the base, as well as the shape and shade of the teeth almost corresponded to the final restoration.

After the positive feedback from the patient, we proceeded on the definitive work. The model for this was the fully anatomical situation of the temporary bridge.

Based on the ideal situation already worked out, a new scan was performed (Figs. 1-3).

After completing the scanning process, the frame was virtually adapted. The design of the bridge framework was started in the software.

As this was to be manufactured from the millable Ceramill Sintron sintering metal, the corresponding material parameters had to be observed.

Initially, we designed a reduced wax-up (Fig. 4). We reduced the tooth sections so that the shape resembled a prepared stump.

The gingival portion was also defined. We had adopted the model, gingiva and abutment situation for the scan.

Then, we screwed the matching scanbodies onto the model analogues. Due to the strong angulation of the implant at 26, a 20° angled Camlog titanium base had to be used.

This made it possible to optimise the emergence of the occlusal screw connection in the occlusal surface (Fig. 5).

Perfect symbiosis of stability and aesthetics

For stability, Ceramill Sintron was used as material for the bridge framework.

This is a so-called sintering metal, which in its raw state has a wax-like consistency and can be easily processed with desktop milling machines.

As a result, the workflows have become more efficient with significant increase in the safety of the work process.

Sintering the milled structure led to a biocompatible, stable, homogeneous and distortion-free cobalt and chromium (CoCr) frame (Figs. 6-7).

Hence, the casting and labour-intensive finishing of CoCr is no longer necessary.

After checking the fit, we polished the base to a high gloss and bonded the bonding bases to the frame. Now, the Sintron structure could be screwed onto the model (Figs. 8-9).

This situation now formed the basis for the aesthetic finalisation of the superstructure.

The model including the Sintron bridge was duplicated and another saw model was produced; allowing for the preparation margin of individual crowns to be better displayed and checked.

This saw model was scanned and the data obtained “matched” with the CAD data of the temporary bridge enabling us to revert back again to the full anatomy of the future crowns.

For aesthetic reasons, we reduced the front labially to allow us to veneer it individually with ceramics (Fig. 10).

Then, we chose the fully anatomical shape for the posterior crowns which had already proven itself for the temporary restoration.

For the monolithic crowns, we used the highly translucent Ceramill Zolid FX Multilayer zirconium oxide (Amann Girrbach).

This material enables the fabrication of tooth structures and frames with an integrated shade gradient. The soft colour transitions are nature simulate enamel, dentine and cervical shades, without disturbing breaks in colour.

Such tooth-like pre-staining allows for efficient and economical processing without requiring a further manual colouring.

After the sintering process, the individual crowns were adapted (Fig. 11).

The Zolid FX Multilayer crowns could be individualised excellently with stains, so that an aesthetic result could be achieved without great layering efforts.

We added some life to the labially reduced anterior crowns with minimal individual layering by using zirconium oxide veneer ceramic Noritake Cerabien ZR.

The CoCr frame was silanised in the classic manner and opaqued (Fig. 12).

As a precaution, another try-in was made. The crowns were provisionally bonded to the frame and the gingival section was modelled from pink wax.

The try-in is exciting for the patient, clinician and for us. This is where it is revealed whether the work was precise and the transfer from analogue to digital has worked.

And for our case, the try-in showed that our work approach, which always followed the blueprint of the temporary restoration, had proved to be effective. The implant-supported bridge could thus be completed.

To condition the Zolid FX Multilayer crowns, we used Monobond Plus (Ivoclar Vivadent). The ceramic crowns were finally bonded to the frame using Multilink Hybrid Abutment (Ivoclar Vivadent).

Using different gingiva materials from the Ceramage composite system (Shofu), we created a natural-looking gingiva (Figs. 13-17).

Conclusion

Such restorations inspire our patients because they receive fixed dentures despite tooth loss and do not have to accept compromises in terms of aesthetics.

In the end, we all looked forward to the day when the finished work could be handed over to the patient.

After incorporating the implant restoration, the screws were tightened and the screw channels were closed. The patient was happy and left the practice with a completely new attitude to life.

This article was published in Dental Asia May/June 2021 issue.

About the author

DMT David May completed his dental technician training in Stuttgart, Germany, in 2000. From 2000 to 2003, he was employed by the Weber laboratory in Ravensburg, Germany. He then worked in the Stroppe-Jäger dental laboratory in Lindau, where he gained experience in all areas of dental technology. In 2010 he successfully passed his Master’s examination in Karlsruhe and Halle – by taking external courses. Since 2017, he has been working with Rosa Winterhalter as a business partner at the Lindauer Zahntechnik GmbH in Lindau.