INTRODUCTION

Patient demands and expectations have never been as concrete as in this day and age: Influenced by role models on social media and new aesthetic standards, our patients ask for brighter smiles or for restorations with specific tooth forms rather than demanding a perfect copy of nature. For us dental technicians, the challenge lies in finding a perfect balance between fulfilling these demands and respecting established biomimetics-inspired principles of aesthetics and function.

To accomplish this task, we need to know which principles need to be respected and where there is room for creativity. At the same time, it is essential to be well-informed about the latest technological advancements and developments in dental materials to be able to select the most appropriate restorative approaches. Only by understanding the selected materials and technological tools very well, will we be able to exploit their potential and deliver the best possible restorative solution. To sum up, we need to keep one foot in the boat of science and the other in the boat of art. Only by balancing both can we navigate the rapid advancements in the field effectively - ensuring they serve patients’ best interests while avoiding practices that lack purpose or meaning.

The challenge lies in finding a perfect balance between fulfilling the patient‘s demands and respecting established biomimetics-inspired principles of aesthetics and function.

MATERIAL CHOICES

Our favored framework materials for the production of aesthetic anterior restorations include KATANA™ Zirconia UTML, KATANA™ Zirconia STML discs (both Kuraray Noritake Dental Inc.) and lithium disilicate-based press ingots Amber® Press (HASS). These high-strength ceramics are ideal for fulfilling the aesthetic and functional demands of anterior restorations. Their balanced optical properties allow for the creation of lifelike restorations. Their physical and mechanical properties, on the other hand, are responsible for stability during all clinical steps from try-in to permanent placement, proven bonding ability and a certain error tolerance: Minor adjustments or modifications are possible without the risk of inducing cracks or dimensional changes when firing repeatedly. Finally, both materials are digital workflow compatible, which means that procedures are quick, mock-up, temporary restoration and definitive restoration easily aligned, and remakes facilitated.

The restorations are usually designed in full contour; a labial cutback of 0.3 to 0.5 mm creates sufficient space for the veneering porcelain. The preferred layering approach is micro-layering combined with the internal live stain technique, which offers the benefits of a controlled procedure and predictable, highly aesthetic outcomes with brilliant depth effects in short time. A layering material that precisely meets our needs regarding the preferred approach and is perfectly compatible with both, lithium disilicate and zirconia, is CERABIEN™ MiLai (Kuraray Noritake Dental Inc.).

The following two case reports are used to illustrate how this material combines with the different framework materials, revealing further benefits of the selected ceramics and techniques.

CASE #01

LITHIUM DISILICATE VENEERS

This 36-year-old female patient wanted to replace her bonded composite veneers. She expressed the demand for a brighter smile with a bleached color (NW 0.5) selected for her six maxillary anterior teeth and first premolars. However, she wanted the tooth preparation for this treatment to be as minimally invasive as possible.

In addition, she specifically requested that the teeth be square in form, with the lateral incisors the same length as the central incisors and the incisal edges straight, without rounded corners – clearly influenced by modern aesthetic standards. We explained our concerns regarding potential aesthetic and functional issues that might necessitate further intervention or adjustments, but she remained firm in her choices.

FROM DESIGN TO PRESSED FRAMEWORK

In line with the patient’s demands, it was planned to restore her maxillary teeth from first premolar to first premolar with lithium disilicate veneers (Amber® Press HT in the shade W2), which would allow for the desired minimally invasive preparations and bright appearance. Following tooth preparation, an analog impression was taken and sent to our laboratory. After the production of the model, the case was digitalized for the virtual designing of the veneers. In order to create space for the porcelain, the labial surfaces of the full-contour restorations were reduced by 0.3 mm with the software (exocad® DentalCAD, Figs. 1 and 2).

The frameworks were then milled in wax and pressed in Amber® Press HT W2 (Figs. 3 and 4). Sprues were cut and the surfaces of the veneer frameworks processed with a Diagen-Turbo-Grinder Ø 3,5 x 11 mm Cone and Wheel.

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THE COMBINATION OF EFFECT LIQUIDS AND MICRO-LAYERING ON HIGHLY AESTHETIC ZIRCONIA IS THE EFFECTIVE WAY TO ACHIEVE OUTSTANDING RESULTS

Case by Leonidas Dimitriou, MDT

As an addition to its well-aligned portfolio of multi-layered zirconia (KATANA™ Zirconia Multi-Layered series) and veneering porcelain for zirconia (CERABIEN™ ZR), Kuraray Noritake Dental Inc. has recently introduced a set of dyeing liquids. Esthetic Colorant for KATANA™ Zirconia is applied to the surface of the monolithic or anatomically reduced zirconia restoration prior to the final sintering procedure. In this way, it is possible to imitate typical internal colour effects of natural teeth quite easily. Depending on the desired outcome, users may add just a final layer of glaze, liquid ceramics or stains and porcelains to their zirconia restorations treated with Esthetic Colorant. The following two case examples are used to demonstrate two different procedures involving the use of the effect liquids.

CASE EXAMPLE 1

In the first case, we produced three two-unit splinted crown restorations for six maxillary anterior teeth. The zirconia crowns (made of KATANA™ Zirconia YML) were anatomically reduced and individualized with Esthetic Colorant mainly in the incisal and cervical areas immediately after milling. For the application of the selected liquids, we used the Liquid Brush Pen specifically developed for Esthetic Colorant. The restorations were dried for half an hour, placed in the sintering furnace for sintering according to the recommended protocol for KATANA™ Zirconia and subsequently finished with CERABIEN™ ZR porcelains. Finally, CERABIEN™ ZR Paste Stain Glaze was applied for the final high-gloss finish.

Fig. 1. Pre-sintered anatomically reduced crowns after milling.

Fig. 2. Esthetic Colorant applied to the milled restorations.

Fig. 3. Appearance of the individualized restorations after the final sintering procedure.

Fig. 4. Restorations after porcelain layering.

FINAL SITUATION

Fig. 5. Final restorations with a natural appearance. The effects created with Esthetic Colorant shine from deep within the restorations.

Fig. 6. Lateral view of the final restorations from the left.

Fig. 7. Lateral view of the final restorations from the right.

CASE EXAMPLE 2

In this second case, two three-unit restorations were produced using KATANA™ Zirconia YML in the colour A3. We designed and milled them in full contour, then reduced them with hand instruments by 0.2 mm and added some texture effects to the surface before applying Esthetic Colorant. In this case, we played with different shades of Esthetic Colorant. Even when applied on a minimally reduced or monolithic surface, the liquids are able to create a nice depth effect as they diffuse into the zirconia structure. The amount of liquid applied is easily controlled with the Liquid Brush Pen, so that the intensity of the colours is predictable. After sintering, we added some internal stains, CERABIEN™ ZR Luster Porcelain and a final layer of CERABIEN™ ZR FC Paste Stain Glaze to finish the restorations. The outcome speaks for itself.

Fig. 8. Milled monolithic restorations with a pronounced surface texture.

Fig. 9. Vestibular and palatal surfaces individualized with Esthetic Colorant to create and intensify some natural colour effects.

Fig. 10. Appearance of the restorations immediately after sintering.

Fig. 11. Restorations after internal staining.

Fig. 12. A layer of luster porcelain applied to the minimally reduced restorations.

FINAL SITUATION

Fig. 13. Final outcome after glazing.