Case report by Dr. Wissam Dirawi, DDS

During the last decade, zirconia has increasingly established itself as the material of choice in oral prosthodontic rehabilitation. Its great mechanical and inert properties are the main reason for this trend. Since the introduction of multi-layered zirconia blanks more than ten years ago, the optical properties have been improved dramatically. The multi-layered zirconia used nowadays (e.g. KATANA™ Zirconia YML from Kuraray Noritake Dental Inc.) offers well-balanced mechanical properties, translucency and colour. It allows dental technicians from all over the world to produce aesthetic full-contour restorations that are merely stained.

Even in the anterior region, stained monolithic restorations may be an option. Factors such as the age of the patient, the internal colour structure of the adjacent dentition, the number of teeth to be restored (one versus all four or six maxillary anterior teeth), the aesthetic demands of the patient and financial aspects should be taken into account in the material selection process. In the case described below, full-contour zirconia was selected for several reasons.

BACKGROUND

The 71-year-old female presented in the clinical due to aesthetic problems in the maxillary anterior region. Oral hygiene was good and the patient was a non-smoker. Infraposition of the existing implant-based crown (Nobel Biocare Brånemark RP fixture) in the position of the right central incisor (tooth #11 according to the FDI notation) was evident. Moreover, gingival retraction was observed on the maxillary right lateral incisor (tooth #12), while the left lateral incisor (tooth #22) has a major composite filling with discolouration. The patient expressed the desire to adjust the gingival level differences and to restore the four maxillary incisors with all-ceramic crowns for optimal aesthetics.

Fig. 1. Initial situation: Frontal view.

Fig. 2. Initial situation: Facial view.

Fig. 3. Initial situation: Occlusal view of the maxilla.

Fig. 4. Initial situation: Occlusal view of the mandible.

MATERIAL SELECTION

Due to the decision to restore all four anterior incisors, monolithic zirconia was a suitable material option. It would allow the team to obtain the desired results within the financial framework. In order to meet the aesthetic demands of the patient, provide for the required mechanical properties and allow for proper masking of the underlying structures, KATANA™ Zirconia YML was selected. It offers colour, translucency and flexural strength gradation throughout the multi-layered blank.

TREATMENT PROCEDURE: FROM PREP TO TEMPORIZATION

In order to design the indirect restorations, a digital impression was taken with an intraoral scanner and the data was transferred to the dental laboratory Teknodont in Malmoe, Sweden. There, a digital wax-up was created. After patient approval, a matrix was produced and sent to the clinic. Here, the old restorations were removed and the three maxillary incisors (all but the one replaced by an implant) prepared for full coverage restorations. A healing abutment was placed on the implant and a temporary bridge produced chairside using the matrix and Protemp 4 Temporization Material (3M) in the shade A3. Subsequently, a gingivectomy was carried out with a ceramic burr (Ceratip, Kt.314.016 – KOMET) in the buccal aspect of the left central and lateral incisor.

Fig. 5. Chairside-produced temporary in the patient’s mouth.

After the patient’s approval of the aesthetics, phonetics and function of the temporary restoration, the situation was captured with an intraoral scanner again. This allowed the team to duplicate the shape of the construction. Based on the acquired data, a new set of splinted temporary crowns made of PMMA (HUGE Multilayer PMMA) in the shade A3 was milled in laboratory. They were placed to allow the patient to further evaluate the aesthetic appearance and function for a couple of weeks. The patient was happy with the phonetics, function and appearance of the crowns, which were merely slightly too bright in comparison to the adjacent teeth, and approved the shape for the production of the permanent restorations.

Fig. 6. Printed model …

Fig. 7. … with splinted PMMA crowns.

Fig. 8. Lab-made temporary restorations.

Fig. 9. Long-term temporary in place: Lateral view from the right.

Fig. 10. Long-term temporary in place: Frontal view.

Fig. 11. Long-term temporary in place: Lateral view from the left.

FINAL RESTORATIONS: PRODUCTION AND CEMENTATION

Based on the dataset of the temporary restorations, four separate crowns – one implant and three tooth-based – were designed in full contour. Without any anatomical reduction, the restorations were milled from KATANA™ Zirconia YML. Based on the evaluation of the temporary restoration, the shade selected this time was A3.5. CERABIEN™ ZR FC Paste Stain was used for external staining and glazing of the surface. Still in the laboratory, the implant-based crown was cemented to the gold-shaded titanium abutment (Elos Medtech) with PANAVIA™ V5 (Kuraray Noritake Dental Inc.) in the shade opaque for an improved masking effect.

While the abutment crown was screwed onto the implant and the screw hole closed with composite, the three tooth-based crowns were placed using PANAVIA™ SA Cement Universal (Kuraray Noritake Dental Inc.).

Fig. 12. Final restorations on the model.

Fig. 13. Intraoral situation prior to restoration placement.

CONCLUSION

Multilayered zirconia is a suitable material for many clinical situations. Due to the availability of modern types of highly translucent, multi-layered blanks, it is possible to produce aesthetic outcomes even when using the material monolithically – not only in the posterior region, but also in the aesthetic zone in some indications. The present case shows that very good results and patient satisfaction can be obtained. And due to outstanding mechanical properties, these outcomes may be expected to last for a long time.

Fig. 14. Immediate treatment outcome: Facial view.

Fig. 15. Immediate treatment outcome: Frontal view.

Fig. 16. Immediate treatment outcome: Occlusal view.

Dentist:

WISSAM DIRAWI

Dr. Wissam Dirawi, Malmoe, Sweden. DDS.
Specialist in Oral Prosthodontics and Senior Adviser at Aqua Dental.

2000 Master´s degree in dentistry.
2000 - 2018 General Dentist in public dental care and private practice.
2011 - 2018 Part-time teacher and researcher at Malmö University, Faculty of Dentistry.
2018 Specialist in Oral Prosthodontics. Senior clinical adviser. Lecturer.

References

- Alfadhli R, Alshammari Y, Baig MR, Omar R. Clinical outcomes of single crown and 3-unit bi-layered zirconia-based fixed dental prostheses: An up to 6- year retrospective clinical study: Clinical outcomes of zirconia FDPs. J Dent. 2022 Dec;127:104321.
- Le M, Papia E, Larsson C. The clinical success of tooth- and implant-supported zirconia-based fixed dental prostheses. A systematic review. J Oral Rehabil. 2015 Jun;42(6):467-80.
- Alammar A, Blatz MB. The resin bond to high-translucent zirconia-A systematic review. J Esthet Restor Dent. 2022 Jan;34(1):117-135.
- Sadowsky SJ. Has zirconia made a material difference in implant prosthodontics? A review. Dent Mat 2020; 36: 1–8.
- Mazza LC, Lemos CAA, Pesqueira AA, Pellizzer EP. Survival and complications of monolithic ceramic for tooth-supported fixed dental prostheses: A systematic review and meta-analysis. J Prosthet Dent 2022; 128: 566–74.
- Passia N, Mitsias M, Lehmann F, Kern M. Bond strength of a new generation of universal bonding systems to zirconia ceramic. J Mech Behav Biomed Mater. 2016; 62:268–274.
- Sailer I, Makarov NA, Thoma DS, Zwahlen M, Pjetursson BE. All-ceramic or metal-ceramic tooth- supported fixed dental prostheses (FDPs)? A systematic review of the survival and complication rates. Part I: Single crowns (SCs). Dent Mater 2015; 31:603-623.
- Pjetursson BE, Sailer I, Makarov NA, Zwahlen M, Thoma DS. All-ceramic or metal-ceramic tooth- supported fixed dental prostheses (FDPs)? A systematic review of the survival and complication rates. Part II: Multiple-unit FDPs. Dent Mater 2015; 31:624–639.

By Manabu Suzuki, Director of Dental Division, Kuraray America, Inc.

Kiyoko Ban, a prominent figure in the dental technology field, has made a lasting impact as a researcher, developer, and founder of Noritake Dental business (Fig. 1). Renowned for her contributions to dental porcelains like Noritake's CZR and EX-3, and KATANA™ Zirconia, Ms. Ban stands as a pivotal force in the global advancement of dental technology, earning her the esteemed reputation of developer and marketer within the dental technology community.

After completing her university education in Nagoya, Ms. Ban initially assisted in her family's gas station business. However, driven by a desire for a career change, she enrolled in a newly established dental technician college in Nagoya at the age of 30. Her aspiration was to enter a field where gender distinctions held no sway, offering the potential for worldwide recognition based on technical mastery.

In 1977, a college-sponsored tour to American dental laboratories ignited Ms. Ban's dream to work in the United States. However, she delved into research across various fields such as chromatology (the science of color), ceramics and metals, finding a newfound passion for research over clinical work after graduation because she was offered a "Curriculum Chief" position from the college when she graduated (Fig. 2).

Fig. 2. Ms. Ban, a curriculum chief at the Dental Technicians College, devoted her evenings to material research.

Fig. 3. In the 1990s, Ms. Ban actively engaged in promoting EX-3 through sales efforts in Italy.

Her teaching career spanned from the age of 34 to around 40, during which she pioneered porcelain training sessions for technical improvement and arranged lectures over weekends by famous speakers such as Masahiro Kuwata.

At the age of 40, she resigned teaching career and pursued her research career. The opportunity to conduct full-scale experiments led her to the discovery of a company with advanced ceramic technology "Noritake Co., Limited", renowned for its tableware. In 1986, Cusp Dental Supply, a research institute, was established by Ms. Ban in Nagoya, focusing on the development of materials for PFM crowns. The commercialization of Super Porcelain AAA (EX-3) in 1987 marked a significant milestone, addressing issues prevalent in porcelain materials of that time, such as cracks, greening, and fluorescence.

She began traveling all over Japan and around the world to sell the products she had developed and went on to develop new products that were needed by dental technicians worldwide (Fig. 3). She continued to develop new products such as CZR, CZR Press, and KATANA™, the world's first multilayer zirconia.

Ms. Ban has been actively involved in mentoring students and graduates seeking opportunities to work overseas. During summer vacations, she took students and professionals interested in working abroad to countries like Australia, Germany, and the United States. The aim was to visit dental clinics, dental technician schools, and laboratories, fostering exposure and learning in an international context.

Simultaneously, Ms. Ban delved into researching non-precious dental technology. Inspired by her exposure to the term "non-precious" during her time in the United States, she anticipated its potential in Japan. Her research presented at lectures and events highlighted the shift in the landscape as the price of gold surged, rendering precious alloys containing significant amounts of gold impractical for PFM crowns.

As the demand for their developed products grew, the need for global acceptance became apparent. In 1990, Cusp Dental Research was established in Manhattan, New York, marking Ms. Ban's foray into establishing a company overseas. Despite the unfamiliarity with legal procedures and the challenges of setting up a foreign company, Ms. Ban, driven by determination, overcame these hurdles. The establishment of the company in the United States expanded their presence internationally Fig. 4).

Fig. 4. Capturing the essence of ISC 1996 - the International Symposium on Ceramics in Orlando, FL..

Noritake Dental Supply Co., Limited was established in 1998 by the Noritake Co., Limited, which aimed to further expand its dental business. Despite the absence of a capital relationship with Noritake at the time of establishing the research laboratory, Ms. Ban played a key role in joint research efforts with Noritake. Then she was invited to this company as the position of president, owning 60% of the stock, while Noritake held 40% (Fig. 5).

Besides Noritake Dental business, she continued expansion with the establishment of a dental laboratory in Boston in 1995. Despite the challenges posed by the September 11, 2001 World Trade Center incident, they acquired their building in Boston, integrating their New York laboratory into the Boston operations.

Ms. Ban's tenure as president of Noritake Dental Supply persisted until 2009, but organizational changes following the merger with Kuraray in 2011 led to her transition into an advisory role (Fig. 6). Despite the shift in responsibilities, her commitment to the dental technician profession remained steadfast.

Fig. 5. Noritake Dental Supply Inc Inauguration Party, 1998.

Kiyoko Ban's path encapsulates not just a career but a legacy in the field of dental technology. From her early struggles in a tooth carving class to establishing and expanding international laboratories, Ms. Ban's story is one of determination, innovation, and a deep-rooted commitment to advancing the dental technician profession.

Fig. 6. A scene from Ms. Ban’s retirement celebration as Noritake Dental Supply president, surrounded by esteemed dental technicians from around the world.

Available Now!

Have you ever produced a zirconia restoration without obtaining the outcome you expected? Most dental technicians probably have. The bad thing is that aesthetic flaws such as colour deviations or white spots and technical issues like cracks can occur and require remakes. The good thing is, however, that those problems are usually avoidable. Do you know how?

We would like to show you – in the new KATANA™ Zirconia Troubleshooting Handbook we just completed. On 30 pages, this handbook summarized the most important facts about modern zirconia-based restorative materials, their selection, the KATANA™ Zirconia line-up and, finally, possible aesthetic or technical problems, their origin and solutions to overcome them.

Let us assume that the beauty of your restorations is limited due to a lack of translucency. By looking up the problem “lack of translucency”, you will find a compact, well-structured overview of possible causes and adequate solutions. The recommendations include selecting dry instead of wet milling, abstaining from sandblasting the restoration surface and checking of the sintering parameters, quality of the sintering beads and position of the restoration in the furnace. For more details, problems and solutions, download the handbook!

DOWNLOAD NOW

Importance of high-quality prosthodontic treatment

High-quality treatment is probably the most important element on the road to patient satisfaction. During every single appointment, the patient wants to feel well cared for by a skilled professional, while chair time and the number of appointments should be reduced to the necessary minimum. This implies that, in the context of prosthodontic treatment, a restoration needs to fit perfectly straight away and be stable over time to avoid remakes and extra appointments.

But how is it possible to deliver perfectly fitting, high-quality restorations every time? Among the potential sources of problems with the quality of indirect restorations are common mistakes made in the dental office or laboratory, communication issues and – often overlooked – the use of low-quality dental zirconia.

Zirconia restorations – contemporary and aesthetic dental solution

More than 20 years ago, zirconia entered the dental market as a substitute to metal used for the production of crowns and bridges. Both materials – zirconia and metal – were usually combined with a layer of porcelain, forming porcelain-fused-to-metal or porcelain-fused-to-zirconia restorations. In the years to come, several leading manufacturers of dental zirconia (like Kuraray Noritake Dental Inc.) focused on material improvements. These improvements gradually transformed the original white-opaque framework material into a ceramic material with tooth-like optical and excellent mechanical properties. The latest zirconia variants, available with different levels of translucency and strength, are regarded as the best-possible treatment option in a wide variety of patients and indications by many dental professionals around the world. One reason is that they require just a small or no layer of porcelain. Another is that, with low minimum wall thicknesses, they allow for conservative tooth preparations, while they offer a favourable long-term behaviour – that is, if a high-quality material is used.

Quality differences of dental zirconia

Zirconia product quality may vary depending on various factors such as the purity of the raw materials (not only zirconia, but also alumina and yttria as well as colour additives etc.), the exact chemical composition, the grain size and particle distribution. Every step in the blank production process – from powder compilation to blank pressing and pre-sintering – has an impact on the final quality, i.e., the mechanical and optical properties of the zirconia, too.

Common issues resulting from low-quality zirconia

Whenever there is something wrong with the optical properties of a restoration – with its translucency, its overall colour or the transition from one layer to the next in blanks with a multi-layered colour structure – the problem will become apparent after the final sintering procedure in the laboratory. A remake might be necessary and eventually, the blemish might be identified during try-in, which will most likely have a negative impact on patient satisfaction. The same is true for cases with an improper fit resulting from inhomogeneities in the material structure, for example. What is even worse is an inferior biocompatibility, surface quality, edge stability, flexural strength or fracture toughness. These issues are identifiable only with testing equipment that is very expensive and usually not available in dental laboratories. This means that flaws of this kind usually remain undetected until a real clinical problem – like gingival recession, increased plaque accumulation, higher wear or an early failure that might cause pain and discomfort – occurs.

Overview of potential problems and clinical consequences for patients

Certification and standardization of dental zirconia

That is why specialists have developed an ISO standard (ISO 6872:2015), which describes in-vitro tests every manufacturer of dental zirconia used in Europe or the United States needs to conduct in order to pass FDA approval and receive the CE mark. The described tests are used to measure the flexural strength and fracture toughness, the two probably most important properties determining the long-term behaviour of restorations produced from the material. Every material used in Europe or the United States needs to have passed these tests.

How to avoid placing low-quality dental zirconia restorations in your patients’ mouths

Hence, everyone using this certified dental zirconia should be safe and able to minimize material-related risks. However, the increasing popularity of dental zirconia has attracted the attention of companies trying to have their share of the cake without undergoing the necessary efforts needed to safeguard a high product quality and pass certification. Non-certified products that lack CE marking have one thing in common: they definitely put your business and patient at risk.

So how is it possible to safeguard zirconia product quality from the dental office? The good news is that there are some simple rules available. By following them, you are able to avoid placing counterfeit or low-quality dental zirconia restorations in your patients’ mouths.

Avoid placing counterfeit or low-quality dental zirconia restorations in your patients’ mouths.

Three golden rules to provide your patients with high-quality zirconia restorations:

• Only order restorations that are produced domestically or in a region with the same standards as your own: restorations produced in dental laboratories in China, for example, need to fulfil lower standards (thus lacking CE mark) and might not live up to your expectations.
• Talk to your (domestic) laboratory partner about the source of their zirconia: make sure they are purchasing zirconia from leading manufacturers (e.g. Kuraray Noritake Dental Inc.) via authorized distributors or sellers they really know.
• Avoid deals that are too good to be true: low prices may be tempting, but the final cost of a treatment may be even higher than usual when complications occur.

Long-term impact for patients when using certified zirconia restorations

Making certain that the zirconia placed in your dental office fulfils the highest possible quality standards is an important contribution to long-term patient satisfaction. Even if the initial cost of high-quality zirconia restorations is somewhat higher than that of inferior-quality work, the overall investment may be lower when the restorations last longer and remakes are eliminated. Your happy patients are likely to be more engaged and compliant with oral hygiene regimens as well as loyal, with a positive impact on your reputation and patient base.

Research zirconia options and choose for products from certified manufacturers

If you would like to go one step further, you can even compare certified zirconia variants from several manufacturers and detect differences. Kuraray Noritake Dental Inc., for example, is one of very few manufacturers of dental zirconia carrying out the whole manufacturing process including raw material production in-house. In this way, the company is able to control every step in the procedure and provide for an outstanding product quality – no matter which material variant is selected. With the available portfolio consisting of KATANA™ Zirconia UTML (ultra translucent multi-layered), KATANA™ Zirconia STML (superior translucent multi-layered) and the high-translucent multi-layered HTML PLUS as well as YML (with additional strength and translucency gradation), it is possible to cover virtually every indication.

By DT Simone Maffei and Dr. Filippo Menini

EVOLUTION IN PROSTHODONTICS

Nowadays, digital workflows in prosthodontics are well-established, and many modern dental laboratories have already embraced the option of producing monolithic restorations or restorations with a minimal cut-back for micro-layering in a fully digital environment.

The spread of digital technologies and the availability of new restorative materials with improved aesthetic properties have increased the popularity of this technique among dental technicians. This way of working offers considerable advantages for daily procedures, starting with improved ways of communication between the clinician and dental technician. For example, it is now possible to view and evaluate impressions with the whole treatment team including the dental technician almost instantaneously after impression taking – and without anyone having to leave their office.

In addition to advanced communication options, digital technologies have allowed us to use materials that otherwise could not be processed, such as zirconia and hybrid composites. As a consequence, lots of innovative materials conquered the market, and this has opened up the possibility to always select what is perfectly suited for each specific clinical situation. Adapting to these trends is absolutely essential for anyone who wants to meet a modern dental practitioner’s increased demands.

LONG DISTANCE DENTAL COLLABORATION

Working with digital workflows has allowed us to broaden the scope of action of the modern laboratory, enabling virtually effortless collaboration with clinicians hundreds or thousands of kilometres away. The case presented below is a perfect example: In our dental laboratory in Modena, we produced two anatomical crowns made of KATANA™ Zirconia for a patient who needed a combination of direct and indirect restorative treatment to be carried out by Dr. Filippo Menini in Belluno, about 300 km to the northwest. The whole communication and coordination between practice and laboratory was performed remotely and without us seeing the patient.

MATERIAL CHOICES

Monolithic restorations offer countless clinical and technical advantages. With a major part of the process accomplished by machines, they truly rationalize procedures. The challenge resulting from this simplification, however, lies in the achieving of excellent aesthetics.

Whereas until a few years ago, it was very difficult to accomplish this task due to the poor optical properties of the available materials, today we can safely say that we have materials, techniques and protocols at our disposal that allow us to obtain aesthetically acceptable results. At the same time, those materials offer excellent mechanical resistance to the forces and stress to which they are exposed in the oral cavity and a very high precision of fit, if these restorations are produced in a fully digital workflow.

We have chosen to work with prosthetic materials and finishing solutions from a company that manufactures and develops them in-house: Kuraray Noritake Dental Inc. (Kuraray Noritake). They offer zirconia discs for milling as well as effect liquids, veneering porcelain and liquid ceramics for an aesthetic finish and even resin cement systems for adhesive luting – all from a single source. This gives us the advantage of using clear and predictable working protocols from fabrication to cementation of the restoration.

CLINICAL CASE

The 31-year-old patient presented with multiple carious lesions, inadequate restorations and in particular a destructive caries in the maxillary right second premolar (tooth #15, FDI notation, Fig. 1). The latter tooth was endodontically treated and built up using a glass fibre post. The X-ray revealed carious lesions and infiltrated margins of the restorations (Fig. 2). The treatment plan for this quadrant included direct composite restorations on the first premolar and first molar (teeth # 14 and 16) and an indirect zirconia crown used to restore the second premolar (tooth #15; Fig. 3). In addition, a zirconia crown needed to be produced for the mandibular right second premolar (tooth #45).

Fig. 1. Initial clinical situation in the maxillary right quadrant.

Fig. 2. Radiograph showing carious lesions and restorations with marginal leakage.

Fig. 3. Marked surfaces that will be treated.

During the first session, the clinician restored the first molar and premolar with composite (Figs. 4 and 5). In addition, the tooth preparation on the maxillary and the mandibular second premolar was performed using the biologically oriented preparation technique (BOPT; Figs. 6 and 7). Two single-tooth temporaries were then produced, recreating a cervical profile according to the BOPT (Fig. 8). In the next step, the digital impression was taken using the double chord technique (Fig. 9). The file generated by the intraoral scanner was first analysed using a greyscale view. This view allows for a better assessment of the quality of the acquired data than the coloured image (Fig. 10). The temporary restorations were finished, polished and placed on the teeth using temporary cement (Fig. 11).

Fig. 4. Restoration procedure on the maxillary first molar.

Fig. 5. Restoration procedure on the maxillary first premolar.

Fig. 6. BOPT crown preparation on the maxillary second premolar.

Fig. 7. Detail of the subgingival preparation, using burs with calibrated notches, taking care not to touch the supra-crestal attachment complex, but precisely taking care to remain within the width of the sulcus.

In the dental laboratory, we received the intraoral scans in the STL format: Both arches with the prepared teeth and the usual bit register (vestibular scan of the arches in occlusion). Following a careful evaluation of the impressions and the quality of the triangulation of the points of the STL file detected by the scan, a full-contour design of the crowns was performed (zero cutback crowns). This allows us to obtain an emergence profile, according to the BOPT, which is extremely accurate. The anatomy was developed taking into account the functional movements of the patient, which were based on information retrieved from a virtual articulator integrated in the CAD software. These movements can be verified and – if necessary – corrected on the physical articulator in a subsequent step. As it is possible to use the same type of articulator (in our case ARTEX by Amann Girrbach) both in the virtual environment and the real one (control phase) offers the advantage of using the same settings and consequently the same movements in both worlds (Fig. 12).

Fig. 8. Production of the temporary restoration.

Fig. 9. Digital impression taken using the double cord technique: a 000-sized cord soaked in aluminium chloride is placed in the sulcus as the first cord, followed by a non-soaked cord of size 1.

Fig. 10. Greyscale view of the impression, facilitating the clinical evaluation.

Fig. 11. Cementation of the temporary restoration.

Fig. 12. Virtual models based on the digital impression of both arches, with the software-designed full-contour crowns in different views.

The STL files of the designed restorations were sent to the CAM software for milling of the zirconia crowns with a 5-axis CNC machine. The material of choice was in this case KATANA™ Zirconia YML (Kuraray Noritake Dental Inc), which is multi-layered in strength, translucency and colour, and thus suitable for a variety of cases (Fig. 13). Once milling was finished, the elements were removed from the disc and their surface treated with diamond burs and specific rubbers designed for the processing of pre-sintered zirconia. In this phase, it is possible to individualise the anatomy and surface texture of the restorations, a task that is very difficult to accomplish in the milling process. With the dedicated rubbers, the surface can also be smoothened, which will improve the appearance of our restorations after sintering (Fig. 14).

On top, individualization of the pre-sintered restorations was accomplished with Esthetic Colorant (Kuraray Noritake). These new effect liquids have been specifically developed for KATANA™ Zirconia. They contain a special primer that limits the depth of penetration, which results in an appearance similar to external stains, while a depth effect is created. Precise application of the liquids is possible with the Liquid Brush Pen. The Esthetic Colorant line-up consists of twelve colours to facilitate stock management in the dental laboratory, while still providing for natural aesthetics and perfect harmony in the oral cavity. Impact on the flexural strength of the zirconia substructure by the liquids is kept to a minimum, as they have been optimised to limit this effect and avoid fractures. (Fig. 15).

Sintering is carried out in a specially calibrated furnace, scrupulously following the protocol recommended by the manufacturer. Afterwards, the finishing procedure can be continued. With special stones, the cervical edge was first regularised: In the deeper, subgingival areas, the intraoral scanner usually has some difficulties capturing all the necessary information. As a consequence, the STL file is triangulated with some irregularities at the cervical margin. These irregularities need to be regularised, before the thickness of the margin is reduced to '0'. In fact, during milling it, is created with a thickness of 0.2 mm to avoid micro-chipping that would compromise the accuracy of the cervical margin. Figure 16 shows both the thickness of the cervical margin, which, despite the finishing preparation, retains a thickness of 0.2 mm, and the irregular course of the same due to the irregular shape of the STL file around the sulcus.

Fig. 13. KATANA™ Zirconia YML blank with milled crowns.

Fig. 14. Finishing with diamond burs and specific rubbers for pre-sintered zirconia.

Fig. 15. Individualisation with Esthetic Colorant.

Fig. 16. Finishing of the restorations after sintering.

The restorations were then sandblasted with 50-μm aluminium dioxide at 2 bar pressure and cleaned under a steam jet. After an evaluation of the colour revealed after sintering, the finishing phase was completed with the aid of CERABIEN™ ZR FC Paste Stain (Kuraray Noritake Dental Inc.) and polishing instruments. The ceramic emulsions FC Paste Stain allow us to adjust the chroma and value of the restorations and to imitate all those aesthetic features that will improve integration in the oral cavity. With this technique, it is very easy to achieve the desired shade match, as the appearance of the stain applied to the surface is exactly like its appearance after firing. In this way, it is easy to monitor the outcome and – if desired – compare with a reference and adjust whenever necessary (Figs. 17 and 18).

For cementation of the restorations, the clinician used PANAVIA™ SA Cement Universal in combination with KATANA™ Cleaner (both Kuraray Noritake Dental Inc.). The cleaner has a pH value of 4.5 be used both intra and extra-orally, improving adhesion in all restorative procedures. PANAVIA™ SA Cement Universal is the only self-adhesive resin cement containing the unique LCSi monomer – a long carbon-chain silane coupling agent. In combination with the original MDP monomer, which is also present in the paste and enables chemical adhesion with zirconia, dentin, enamel and metal alloys, this coupling agent provides for adhesion of the cement to any material, including glass-ceramics, without the need for a separate primer (Figs. 19, 20 and 21). At the cementation appointment, the last planned direct reconstruction of the maxillary second molar (tooth #17) was also carried out.

Fig. 17. Characterisation with CERABIEN™ ZR FC Paste Stain.

Fig. 18. Finished restorations ready to be handed over to the clinician.

Fig. 19. Cementation procedure in the maxilla: Sandblasting of the tooth and cleaning of the tooth structure with KATANA™ Cleaner.

Fig. 20. Cementation procedure in the maxilla: Sandblasting of the crown’s intaglio and cleaning of the restoration with KATANA™ Cleaner.

Fig. 21. Cementation procedure in the maxilla: Self-adhesive cementation with PANAVIA™ SA Cement Universal.

Fig. 22. Direct restoration procedure on the second molar.

Fig. 23. Restorations immediately after finishing and polishing.

Fig. 24. Detailed view of the restored quadrant.

Fig. 25. Occlusal view of the maxillary teeth.

RESULT

The aesthetic integration provided by the high quality of KATANA™ Zirconia YML, combined with the pre- and post-sintering individualisation, made it possible to achieve an excellent integration of the anatomical zirconia crowns. Figures 22 to 25 show the outcome in the newly restored maxillary right quadrant with natural tooth structure, direct composite restorations and the monolithic zirconia crown.

ABOUT THE AUTHORS

DT SIMONE MAFFEI

Simone Maffei, a dental technician since 1996 (IPSIA L.Galvani Reggio Emilia), embarked on his career in Modena at his father William's laboratory. Throughout his professional journey, he has demonstrated a commitment to excellence by participating in numerous courses led by prominent international speakers. These courses span the realms of dental technology and photography. Presently, Maffei is not only a respected speaker at national and international conferences but has also contributed articles to both Italian and foreign sector magazines. His written works delve into the intricate intersection of dental photography and the aesthetics of the smile. A testament to his expertise, Maffei earned recognition as the recipient of the prestigious AIOP International Award in 2014. He actively shares his knowledge by conducting courses in Italy and abroad, focusing on dental technology, dental photography, natural ceramic layering techniques, and the three-dimensional coloring of monolithic restorations. As a valued member of the Digital Dental Revolution (DDR) Team, Maffei serves as a speaker at courses and international conferences, where he imparts insights on various facets of digital dentistry. Simone Maffei is also the proud owner of the Laboratorio Odontotecnico Maffei in Modena. Collaborating with his sister Elisa, the laboratory specializes in crafting aesthetic ceramic reconstructions for both natural teeth and implants, showcasing a dedication to the art and science of dental aesthetics. Active Member of AIOP SOSPESO – Accademia Italiana di Odontoiatria Protesica (Italian Academy of Prosthetic Dentistry). Ordinary Member of SIPRO Società Italiana Protesi e Riabilitazione Orale (Italian Society of Oral Prosthetics and Rehabilitation).

FILIPPO MENINI

Dr. Filippo Menini graduated in Dentistry and Dental Prosthetics from the Universidad Europea De Madrid in 2017. He has been passionately dedicated to the study of direct and indirect adhesive techniques in the field of conservative dentistry. He became a Regular Member of the Italian Academy of Conservative Dentistry in 2018 and the Italian Academy of Prosthetic Dentistry in 2019. In November 2021, he joined the Think Adhesive Members, and since February 2022, he has been a contract tutor at the University of Siena in the Endo-Resto master program taught by Professor Grandini. Dr. Menini has attended numerous courses in conservative dentistry, endodontics, periodontology, and adhesive prosthetics to manage his work in a multidisciplinary perspective. He has his dental practice in Belluno.

Case by MDT Daniele Rondoni and MDT Roberto Rossi

Full-contour or an anatomically reduced design? When we need to decide how we want to design and finish a zirconia restoration we are asked to produced, many factors need to be taken into account – from aesthetics to function and from time- to budget-related ones. As the outcomes are strongly dependent on the optical and mechanical properties of the zirconia used, however, we are convinced that the first thing to do is to select a portfolio of high-quality zirconia materials. By experimenting with them in the dental laboratory, using different designs and finishing approaches with aligned materials and by comparing the results, you will be able to select the most appropriate concepts for your everyday work. In addition, you will develop a clear idea on when to use which concept.

Our own selection

The zirconia portfolio used in our dental laboratory consists of the KATANA™ Zirconia Multi-Layered Series from Kuraray Noritake Dental Inc. It consists of three materials with a multi-layered colour structure designed to meet different needs with regard to flexural strength and translucency (KATANA™ Zirconia UTML, STML and HTML PLUS) and one material with colour, translucency and flexural strength gradation (KATANA™ Zirconia YML). Due to the favourable optical properties of this series and new effect liquids, it is often possible to opt for a full-contour design or – in the anterior region – for a slight cutback limited to the vestibular area plus a micro-layer of porcelain.

The effect liquids – Esthetic Colorant for KATANA™ Zirconia – were introduced n early 2023. They are applied to the surface of the milled zirconia to pre-treat tissue areas of large restorations, to add specific individual characteristics to the restoration or to prevent a greyish effect caused by the shining through of discoloured abutment teeth or metal parts. While most liquids are used on the outer surface of the restorations, the latter effect is achieved by applying Esthetic Colorant OPAQUE or WHITE to the intaglio.

Case example

The following case example describes the use of Esthetic Colorant in the context of producing a full-contour screw-retained implant bridge made of zirconia with a titanium bar. The zirconia part was milled from KATANA™ Zirconia YML, the vestibular morphology refined with rotating instruments and then, the vestibular, palatal and occlusal surfaces were treated with Esthetic Colorant as shown in Figures 1 and 2. The true colour effect is revealed after sintering.

Fig. 1. Frontal view of the milled zirconia structure after the application of Esthetic Colorant in the shades BLUE, GRAY, ORANGE and PINK.

Fig. 2. Occlusal view of the milled zirconia structure after the application of Esthetic Colorant BLUE, GRAY, ORANGE and PINK.

Fig. 3. Nicely pre-treated zirconia structure after sintering.

By adding some CERABIEN™ ZR FC Paste Stain and Glaze in the vestibular area and to the tissue parts, it is possible to finish this restoration in a nice way. The contact areas are always just polished to a high gloss in our approach, as it is the most antagonist-friendly way of treating the surface. As a final measure, the zirconia structure was connected to the titanium bar before it was sent to the dental office for try-in.

Fig. 4. Frontal view of the finalized zirconia part.

Fig. 5. Occlusal view of the structure after finishing.

Fig. 6. Connecting the zirconia superstructure and titanium bar.

Conclusion

With a well-selected zirconia portfolio and aligned finishing solutions, it is easy to establish concepts that allow you to respond to the needs of virtually every patient in a streamlined way. In our experience, the use of high-quality products with good aesthetic properties – a high translucency and naturally pre-shaded multi-layer structure – pays off as it allows us to reduce the thickness or do without a porcelain layer. In this way, we are able to increase the efficiency of our procedures without compromising the outcomes.

The KATANA™ Zirconia Multi-Layered Series and the new Esthetic Colorant for KATANA™ Zirconia support us in an ideal way by allowing us to efficiently produce a perfect base for whatever finishing approach we select.

Dentists:

Case by Kanstantsin Vyshamirski

A male patient (47 years of age) presented to his dentist with severe damage to his teeth. His main request was to increase aesthetics, to achieve a more pleasing envisaged aesthetic area. A side request was to achieve a ‘whitening but natural look’. This was achieved by using a lighter colour palette of zirconia and porcelain materials.

The final result was achieved through the creation of a wax-up, followed by a mock-up, provisional restoration and finally adhesive bonding of the zirconia crowns.

INITIAL SITUATION

Fig. 1. Initial situation. Male patient (47 years of age).

Fig. 2. Planning the new smile according to patient’s aesthetic and functional parameters.

Fig. 3. Mock-up in place to check the new look in the patient’s mouth.

Fig. 4. KATANA™ Zirconia YML shade A1 crowns with labial cutback after milling.

Fig. 5. Crowns after sintering on the plaster model.

Fig. 6. Noritake CERABIEN™ ZR porcelain layering map.

Fig. 7. Finishing the labial surface using both polishing and selfglaze. On the palatal side of the crowns only CERABIEN™ FC Paste Stain stains and glaze were used for finishing. To aid in optimisation of the soft tissue condition the palato-cervical and near proximal areas were polished.

Fig. 8. Finished crowns on the plaster model.

Fig. 9. Try-in using PANAVIA™ V5 White try-in paste, to confirm the proper appearance. For the final adhesive cementation PANAVIA™ V5 White has been used.

FINAL SITUATION

Fig. 10. Situation after seven months. The result is aesthetically pleasing and the gingival condition excellent.

Fig. 11. Recall after 1.5 years.

Dentist:

KANSTANTSIN VYSHAMIRSKI

Kanstantsin started his dental technician career in 2014. His speciality is aesthetic prosthetic porcelain works. Kanstantsin is an experienced user of KATANA™ Zirconia and Noritake porcelains. He owns his lab in Riga, Latvia.

Photo credits to Giuliano Moustakis

Can you imagine a world without multi-layered zirconia? The invention of a zirconia material with natural colour gradation and well-balanced translucency and strength led to fundamental changes in the way zirconia-based restorations are produced. When the first product of its kind – KATANA™ Zirconia ML – was introduced to the dental market exactly ten years ago, dental technicians all over the world suddenly started rethinking their manufacturing concepts.

Since then, the trend towards a decreased thickness of the porcelain layer, a limiting of this layer to the vestibular area and the production of monolithic restorations is clearly perceivable. Technicians have developed their own concepts of micro-layering, which allow for more patient-centred approaches. This is also due to the fact that the total wall thicknesses of the restorations may be decreased without compromising the aesthetics. The line-up of multi-layered zirconia currently available from Kuraray Noritake Dental Inc. (KATANA™ Zirconia UTML, STML, HTML Plus and KATANA™ Zirconia YML with additional translucency and strength gradation) enables users to make indication-related material choices for the production of restorations that are precisely aligned to the individual demands of each case.

The reasons to choose KATANA™ quality

But why choose KATANA™ Zirconia instead of any other multi-layered zirconia disc? According to experienced users of the KATANA™ Zirconia Multi-Layered series, there are many reasons to opt for KATANA™.

For Jean Chiha, owner at North Star Dental Laboratories and Milling Center in Santa Ana, California, it is the combination of optical and mechanical properties that makes the difference: 

“KATANA™ Zirconia is the game changing material with well-balanced esthetics and strength!”. 

Naoki Hayashi, president of Ultimate Styles Dental Laboratory in Irvine, California, aesthetics is the most decisive argument to opt for the discs from Kuraray Noritake Dental Inc. He states:

“KATANA™ Zirconia discs offer trusted esthetics which gives me confidence in my clinical cases”.

Naoto Yuasa, chief ceramist at Otani Dental Clinic in Tokyo, adds predictability as an important factor:

“KATANA™ sustains my passions for aesthetic restorations and those of a predictable future in the long run”, whereas dependability is the key element.

For Hiroki Goto, the laboratory manager at Sheets and Paquette Dental Practice in Newport Beach, California reports:

“Without KATANA™ there is no pride. Haven’t experienced it yet? You have to see how reliable it is!”

Finally, we have asked Kazunobu Yamada, a pioneer in making porcelain laminate veneers using complementary color techniques and a first-hour user of KATANA™ Zirconia, what comes to his mind when thinking about KATANA™ Zirconia. According to the president of CUSP Dental Laboratory in Nagoya City, there is a clear link between the product name and its characteristics:

“Did you know that the word "KATANA" also means "protection against misfortune and evil"? Katana zirconia, the culmination of many years of research and development by Kuraray Noritake, has an unparalleled quality. KATANA™, for me, is truly "Protection for all technicians".”

The origin of well-balanced properties

It seems that the KATANA™ Zirconia Multi-Layered line-up stands out due to set of valuable properties enabling a dental technician to produce beautiful, high-quality restorations every time. The secret of success lies in meticulous raw material selection and controlled processing from the powder to the pre- sintered blank carried out at the production facilities of Kuraray Noritake Dental Inc. in Japan. They provide for the high product quality that is responsible for the materials’ outstanding behaviour supporting the best possible outcomes.

Clinical Case by DT Ghaith Alousi

What does it take to reconstruct teeth according to the patient’s individual sense of beauty? Experience shows that copying nature is the secret of success. To become a good duplicator, it is essential to develop an eye for detail with regard to tooth forms, surface morphology and the internal colour structure of the teeth to be copied. In addition, the duplicator needs to develop an understanding of the materials and tools used to copy those details. The last key success factor is taking pleasure in interacting with patients.

Read the clinical case created by Ghaith Alousi and published in the LabLine magazine’s Autumn edition now and learn about his approach to creating aesthetic restorations, mimicking nature and truly individualising restorative treatments.

Interview with Andreas Chatzimpatzakis

Fewer bakes, fewer ceramic powders - there is clearly a trend toward simplification in the production of zirconia-based prosthetic work. This is also true for implant-based restorations, which often involve gum parts. DT Andreas Chatzimpatzakis, international trainer for Kuraray Noritake Dental Inc., and the owner of ACH Dental Laboratory in Athens, Greece, shares his approach to high aesthetics in implant prosthodontics in the following conversation.

You are a user of the CERABIEN™ ZR portfolio from the outset. When did you test the products for the first time and why?

Well, it was many years ago when I finished my very first zirconia-based restoration. The reason to test CERABIEN™ ZR was that when I asked the dental technician who had milled the framework which porcelain system to use. He suggested to use CERABIEN™ ZR, which I did. I was immediately impressed by the system and by the outcome I was able to achieve on the first attempt.

Did you ever test any other porcelain systems for ceramic layering?

Yes. Before I becoming an international trainer for Kuraray Noritake Dental Inc., I had the opportunity to test many other porcelain systems for layering on zirconia. Based on this experience, I can say that CERABIEN™ ZR is unique and the best system I have ever used. The reason is that its translucency and chroma are extremely close to natural teeth. In addition, due to a controlled firing shrinkage, a One-Bake Technique may be employed even in long-span restorations.

Your hands-on demonstration at the Kuraray Noritake Dental booth during the IDS 2023 in Cologne focused on White and Pink Aesthetics achieved with CERABIEN™ ZR. Is there a specific concept you use?

Nowadays, everyone producing dental restorations – no matter whether based on natural teeth or on implants – is confronted with increasing aesthetic demands of patients and dental practitioners. The high demands are developed because life-like restorations and cosmetic dental treatment outcomes are presented everywhere in the web and on social media. The showcased quality of outcomes is simply expected, even if the financial budget is limited. To be able to fulfil these demands in the field of implant-based prosthodontics, I have developed an approach that allows me to achieve high aesthetics with little effort. My concept is based on using not too many ceramic powders. For extra chroma and special characterization, I rely on the power of the internal live stain technique, first introduced by Hitoshi Aoshima-sensei.

Please summarize the most important details of your presentation.

The first important detail is the design and characterization of the framework. Before sintering, I apply Esthetic Colorant for KATANA™ Zirconia. After the sintering process, shade base stain and internal stains are mixed and applied. In this way, I create a nice canvas that helps me to achieve a life-like result with only a few selected ceramic powders. In most cases, three to five powders are enough to produce a great result. Among the powders used most frequently are Opacious Body, Body, LTX, Mamelon and CCV. After the first bake and a little grinding, I make use of internal stains again. They offer support in the controlling of the chroma and the integration of special characteristics. When this step is completed, the final build-up is done with one or two ceramic powders, most of the times LT1 and Enamel or LT0. Pink aesthetics are usually created with Tissue 1, 3 and 5. For the free gingiva, LT Coral is my go-to solution. The major goal is always to obtain maximum quality in a minimum of time. To achieve this, a good knowledge of the materials and of course practicing – on both, porcelain build-up and morphology – are strictly required.

Fig. 1. Complex implant-based restoration: Framework design.

Fig. 2. Esthetic Colorant …

Fig. 3.  … applied prior to the final sintering procedure.

Fig. 4. Appearance after sintering.

Fig. 5. Final outcome.

Are there any concrete tips and tricks you would like to share?

For the characterization of the framework, I mix the internal stains with shade base stain powders; mostly with SS Fluoro. For the first bake, especially when the restoration is large and the amount of ceramic to be applied huge, I reduce the heating rate up to 38 degrees per minute. I also increase the drying process up to 17 or even 20 minutes depending to the restoration. Experience shows that these measures optimize the aesthetic outcomes.

You often mention that it is extraordinarily important to understand the morphology of natural teeth to be able to produce beautiful restorations. Why is this the case?

A successful prosthetic restoration needs to offer proper function and aesthetics. Function means a precise fit, perfect contact points and occlusion, a proper emergence profile and interproximal embrasures for self-cleaning etc. All this is described by the term morphology. Aesthetics, on the other hand, is guided by shape and colour. The effort required to establish a proper morphology is much higher (about 70 percent of the total work) than the effort involved in obtaining the right translucency, opalescence and chroma.

What instruments do you use to imitate the morphology of natural teeth and how do you do it?

I usually make use of the Optimum™ Spring Ceramic Brush Size 8 (MPF Brush Co.), stones and diamond burs for detailed grinding and carving after the final bake. I studied morphology at the Osaka Ceramic Training Centre in Japan with Shigeo Kataoka-sensei. According to him, a key factor in creating a perfect macro and micro morphology lies in the shadows. To be able to take into account the interference of light and shadow during grinding, a light source is placed on one side of the restoration.

How many bakes do you need to produce highly aesthetic restorations?

It depends on the case, although in many situations, I nowadays opt for some kind of micro-layering. Lately, I have used micro-layering a lot with internal stain directly on the zirconia framework. In other cases, I do a quick first bake, then the internal staining, a final bake and glazing. For small or single-unit restorations in the posterior region, a One-Bake Technique is often sufficient. Even a Zero-Bake approach using Esthetic Colorant on a monolithic zirconia restoration may be appropriate here, and it is very convenient. If there is a restoration with high aesthetic demands – these are typically single anterior restorations – the technique I select depends on the shade. In some cases, using only the internal stain technique is enough to reach a high aesthetic level, while in other cases, additional steps need to be taken. To my mind, there is no single technique that fits all cases. As mentioned before, I try to achieve high aesthetics in a minimum of time.

Fig. 6. Clinical example of achieving high aesthetics in a minimum of time: Before …

Fig. 7. … and after crown placement.

Fig. 8. High aesthetics …

Fig. 9. … achieved in a minimum of time.

Did your approach change due to the availability of high-translucency zirconia materials with colour (and flexural strength) gradation?

Well, yes! My overall approach changed more to micro-layering. Several years ago, we needed to consider how to mask the framework and how to achieve translucency in areas with limited space. The problem was solved for single-unit and small anterior bridge restorations with the availability of KATANA™ Zirconia UTML and STML. With the introduction of KATANA™ Zirconia YML, a high-translucency material became available for long-span or implant-based restorations as well. We have strength and translucency all in one disc. In most of my cases, the framework material replaces the dentin with regard to morphology and shade. Hence, I need to focus on adding the enamel by applying the transparent and translucent powders. The powders of the internal stain technique are used to characterize the framework, and with a micro-layer of porcelain, the goal of creating an aesthetic restoration in the minimum of time is achieved. This is exactly why I am sure that micro-layering is the future.

What drives you to share your knowledge with others?

My passion! I love my work! And I love to see technicians become better and better. Dental technology is an exciting journey, a journey that begins when the first impression arrives in the dental laboratory, and it ends when the final restoration is cemented into the patient’s mouth. And this journey is so exciting because we change lives. We change people’s personalities, we give them back their smile, we give them back their self-respect. Consider that every day, every single moment working on our bench trying to imitate nature… there is nothing more exciting than that!!!

My approach as an instructor is to lead dental technicians to master the art of observing natural teeth. This is the way every individual will understand morphology and shade. You need no special talent to be a very good dental technician. You need to observe! Your eyes see, your mind understands, and your hands will follow.