429 Too Many Requests

Phosphoric acid is not only used for etching enamel and dentin surfaces within dental bonding procedures, but also frequently as an intra- and extra-oral cleaning agent for tooth structure and dental restorations. But is phosphoric acid always the right choice?

Direct Restorations

Many bonding procedures are performed using self-etch adhesive systems. When applied to the prepared tooth surface, the acidic monomers in the primer and/or the bond partially remove and modify the smear layer, resulting in a thin hybrid layer. A substantial amount of hydroxyapatite crystals remain on the slightly etched surface, enabling both chemical and mechanical adhesion between the adhesive and the dental tissue. If the bonding surface in the cavity is contaminated e.g. with blood or saliva, and phosphoric acid is applied for cleaning and decontamination, it etches the tooth structure, too, resulting in the removal of HAp. This will prevent the desired chemical adhesion, between the bonding system and the tooth, which may lead to compromised bond strength. Hence, cleaning with phosphoric acid may have a negative effect in this context and cannot be recommended.

Great cleaning results with no negative effect on the performance of the dental adhesive are obtained with the universal cleaning solution KATANA™ Cleaner. It contains an MDP salt of triethanolamine (MDP-TEA), as well as 'free' MDP. With a pH of 4.5, KATANA™ Cleaner is essentially neutral, meaning that, unlike phosphoric acid, it does not remove hydroxyapatite from the tooth. However, it does still effectively eliminate any saliva and/or blood contamination.

Indirect Restorations

For materials containing glass, such as lithium disilicate and feldspathic porcelain, phosphoric acid is a tried-and-tested agent for removing contamination, such as deposits produced when etching these materials with hydrofluoric acid. However, routine use of phosphoric acid to remove contamination from indirect restorations may not be wise. In fact, its use on zirconia is not recommendable, as it could inhibit the desired chemical adhesion of phosphate monomers in the bonding agent to the surface of the zirconia restoration.

When cementing prosthetics using self-adhesive resin cements like PANAVIA™ SA Cement Universal or cements that use self-etching primers (e.g. PANAVIA™ F2.0 or PANAVIA™ V5), the use of phosphoric acid on dentin is not recommended for the same reasons as in the case of direct restorations.

No pitfalls, no restrictions

Unlike 35% phosphoric acid, KATANA™ Cleaner is a product that cleans reliably without inducing negative side effects – independent of the type of tooth structure, kind of restorative material and planned bonding procedure. Hence, it is a universal cleaning solution that allows you to streamline your procedures.

CERABIEN™ ZR
High translucent and opal porcelain for True-to-life, highly aesthetic restoration.

Blue-tinged light translucency at incisor edge of enamel was reproduced with LTx and LT Royal Blue.

Initial situation.

LTx and LT Royal Blue were used at the incisor edges to reproduce the bluish opalescence and translucency effect.

Step 1: Build-up of internal structures.

In order to reproduce the mamelon structure with stain and dentin color, Internal Stains were applied, then baked.

Step 2: Applied the first Internal Stain, then baked it.

In order to reproduce the stain in the internal enamel structure, Luster porcelains were applied and baked as a base.

Step 3: Applied the first enamel structure, then baked.

In order to reproduce the white spot and the incisor halo, Internal Stains were applied before baking.

Step 4: Applied the second Internal Stain before baking it.

To reproduce the subtle color and translucency of enamel, Luster porcelains were applied before baking.

Step 5: Applied the second enamel structure before baking it.

Step 6: Final situation.

Photos: Courtesy of Otani Dental Clinic, MDT Ryuzo Shiba and MDT Naoto Yuasa.

New liquid ceramic FC Paste Stain for full-contour solutions with KATANA Multi-layered Zirconia - Features and 3D-technique.

ROBERTO ROSSI 

"YOU CAN’T STOP THE WAVES, BUT YOU CAN LEARN TO SURF"

Born in Savona in 1989, he studied and got his diploma at “Mazzini” Dental School, the one dental school in his hometown, and he still lives there. In 2007 he was awarded the National Award for Best Dental Technician in Turin. Since 2008 he has been working at Daniele Rondoni’s Dental Lab and he is now in charge of the aesthetic planning of dental restorations. He shares this task with Master Dental Technician Daniele Rondoni, with whom he decides which strategy and materials – composites or ceramic especially – to opt for. In 2011 he coauthored with Mr. Rondoni “Sei faccette additive in composito” (Six additional composite facets), an article published in Dental Labor, 5/2011. A teacher at NISC, Noritake Italian Study Club since 2014, he is also a teacher at the AAT Community College – a reality he feels especially attached to – and he is in charge of the photographic services and social network profiling of the lab.

When art meets technology;
Logical evolution of design and techniques: Microlayering with Kuraray Noritake new porcelains. 

DANIEL RONDONI
Born in Savona in 1961, he lives and works in his hometown where he has been the manager and director of his own laboratory since 1982.

By Dr. PhD. Jusuf Lukarcanin

Is it possible to fulfil high aesthetic demands by restoring anterior teeth with composite resin? It is – provided that several important factors are respected. One of these factors is the faithful reproduction of the natural tooth morphology, which has a decisive impact on aesthetics and function. Moreover, success is determined by the selection of the right shades of high-quality composite resin and their purposeful combination using proper layering techniques.

Introduction

The aesthetic appearance of direct anterior restorations is affected by proper shade selection on the one hand and the creation of a natural shape and texture on the other¹. Hence, the dental practitioner’s own artistic skills play a decisive role. According to Fahl, information about the tooth morphology and function, and the optical properties of the tooth should be taken into consideration when the most suitable restorative material and shade are selected².

These minimally invasive composite restorations are no longer a temporary solution for the anterior region. Instead, they are regarded as an adequate alternative to indirect restorations, as they are both durable and able to closely imitate the natural tooth structure³⁴.

Clinical case example 1

This 45-year-old female patient presented with a diastema and a disproportion in the size and shape of her maxillary central incisors (Fig. 1). In the first step, a detailed case history was taken and an intra-oral examination was carried out. Subsequently, the initial situation was recorded by taking intra-oral photographs, which would allow for a computer-aided morphological evaluation and treatment planning (Fig. 2).

Fig. 1: Pre-operative image.

Fig. 2: Digital mock-up.

The patient’s second visit started with a professional tooth cleaning procedure followed by isolation of the maxillary anterior teeth. Afterwards, the tooth shade was determined and appropriate composite shades were selected. In this case, the shades A2E, Amber Translucent and A3D of CLEARFIL™ Majesty ES-2 Premium (Kuraray Noritake Dental, Japan) appeared to be most suitable. In addition, a mock-up was created using mock-up resin in order to produce a silicone key.

Opting for a minimally invasive procedure, no mechanical tooth preparation using drills was performed after removal of the mock-up. Instead, the enamel was merely etched with 35% phosphoric acid gel (K-Etchant, Kuraray Noritake Dental) to increase the surface roughness. After rinsing and drying, the adhesive agent (CLEARFIL™ Universal Bond, Kuraray Noritake Dental) was applied to the etched surfaces. Composite layering started with the build-up of palatal shells with the aid of the silicone key. Following light-curing of the shells, a small amount of composite in the dentin shade A3D was applied to the proximal surfaces using a thin spatula and a brush. The aim was to reduce light transmission in the area of the dentin core. The restoration was completed with a combination of the composite shades A2E (enamel) and Amber Translucent, which were applied using a modeling brush.

Finishing and polishing was accomplished using flexible rubber polishing discs containing diamond particles (CLEARFIL™ Twist DIA, Kuraray Noritake Dental) with a low-speed handpiece. No additional finishing and contouring was necessary due to the use of a brush during layering, which ensured the creation of a natural shape and surface texture. Figure 3 shows the outcome of the restoration procedure.

Fig. 3: Treatment outcome immediately after polishing.

Oral hygiene training was provided and follow-up examinations were performed after three, six and twelve months (Fig. 4). Healthy hard and soft tissue conditions were observed during these visits.

Fig. 4: Clinical situation at the one-year recall.

Clinical case example 2

This 30-year-old female patient had a diastema, irregularly shaped anterior teeth and showed signs of abrasive tooth wear (Fig. 5). Following a detailed anamnesis and intra-oral examination, the tooth shade was determined and the composite CLEARFIL™ Majesty ES-2 Premium selected in the monochromatic shade Universal A1.

Fig. 5: Pre-operative clinical situation.

Following the isolation of the working field, 35% phosphoric acid etchant (K-Etchant) was applied to the enamel of all teeth between the maxillary right canine and the maxillary left first molar. The surfaces were then treated with a universal bonding agent (CLEARFIL™ Universal Bond) as recommended by the manufacturer. Modeling was carried out with a thin spatula and a modeling brush for composite. Neither a silicone key nor any wetting or modeling resin were used in the procedure. For polishing, the flexible polishing discs CLEARFIL™ Twist DIA were used at low rotational speed. Thanks to the use of the modeling brush, no additional finishing with diamond-coated instruments was necessary. Figures 6 and 7 show the final restoration at baseline and one week after completion of the treatment.

Fig. 6: Treatment outcome at the day of the restorative procedure.

Fig. 7: Clinical situation after one week.

This patient also received oral hygiene training and presented for recalls three, six and twelve months after the treatment. The patient maintained an exemplary oral hygiene behaviour, so that it came as no surprise that the soft tissues were healthy and the restorations were in a perfect condition after one year (Fig. 8).

Fig. 8: Clinical situation one year after the restorative treatment.

Discussion

Nowadays, direct composite restorations are becoming increasingly popular. Especially for young patients and all those who do not want to sacrifice large amounts of healthy tooth structure, the technique is an ideal treatment option⁵. In many cases, aesthetic outcomes are possible without mechanical tooth preparation, but a selective etching procedure only⁶.

The clinical lifetime of these restorations depends on many factors. Important prerequisites for high-quality outcomes include the selection of a suitable composite material with the required surface hardness, appropriate finishing and polishing, a good oral hygiene behaviour, and proper maintenance measures during periodical follow-up visits. As a matter of course, the manual skills of the dental practitioner and the use of selected materials according to the manufacturer’s instructions for use also have a direct impact on the long-term success of the restorations⁷⁸⁹. A user’s inability to meet one of these requirements and failure to carry out all working steps correctly may have a direct impact on the quality of the restoration.

Conclusion

Composite resin is a popular material class for the production of aesthetic anterior restorations die to their straightforward use and rapid application, good repair options and high aesthetic potential when used properly . The two case examples illustrate that a treatment with composite resin is often the best treatment option when a non-invasive procedure completed within a single visit is desired.

About the author

Dr. Jusuf Lukarcanin is a Certified Dental Technician (DCT) and a Doctor of Dental Science (DDS). He studied dentistry at the Ege University Dental Faculty in Izmir, Turkey, where he obtained a Master‘s degree in 2011. In 2017, he received a Ph.D. degree from the Department of Restorative Dentistry of the same university. Between 2012 and 2019, Dr. Lukarcanin was the head doctor and general manager at a private clinic in Izmir. Between 2019 and 2020, he worked at Tinaztepe GALEN Hospital as a Restorative Dentistry specialist, between 2020-2022 he worked at MEDICANA International Hospital Izmir as a Restorative Dentistry specialist. Currently he is an owner of a private clinic for aesthetics and cosmetics in Izmir.

References

^{1. Heymann HO (1987) The artistry of conservative esthetic dentistry Journal of the American Dental Association 115(Supplement)14-23.}

^{2. Fahl N Jr (2012) Single-shaded direct anterior composite restorations: A simplified technique for enhanced results Compendium of Continuing Education in Dentistry 33(2) 150-154.}

^{3. Barrantes, J. C. R., Araujo Jr, E., & Baratieri, L. N. (2014). Clinical Evaluation of Direct Composite Resin Restorations in Fractured Anterior Teeth. Odovtos-International Journal of Dental Sciences, (16), 47-61.}

^{4. Vargas M (2011) Clinical techniques: Monocromatic vs. polycromatic layering: How to select the appropriate technique ADA Professional Product Review 6(4) 16-17.}

^{5. Ferracane, J. L. (2011). Resin composite—state of the art. Dental materials, 27(1), 29-38.}

^{6. Norling, N. A. (2010). Combining “prep-less” and conservatively prepared veneers to correct enamel defects and asymmetry. Journal of Cosmetic Dentistry, 2010.}

^{7. Ölmez, A., & Kisbet, S. (2012). Kompozit rezin restorasyonlarda bitirme ve polisaj işlemlerindeki yeni gelişmeler. Acta Odontologica Turcica, 30(2), 115-22.}

^{8. Senawongse, P., & Pongprueksa, P. (2007). Surface roughness of nanofill and nanohybrid resin composites after polishing and brushing. Journal of Esthetic and Restorative Dentistry, 19(5), 265-273.}

^{9. Giacomelli, L., Derchi, G., Frustaci, A., Bruno, O., Covani, U., Barone, A., Chiappelli, F. (2010). Surface roughness of commercial composites after different polishing protocols: an analysis with atomic force microscopy. The open dentistry journal, 4, 191.}

^{10. Hickel, R., Heidemann, D., Staehle, H. J., Minnig, P., & Wilson, N. H. F. (2004). Direct composite restorations. Clin Oral Invest, 8, 43-44.}

^{11. Korkut, B., Yanıkoğlu, F., & Günday, M. (2013). Direct composite laminate veneers: three case reports. Journal of dental research, dental clinics, dental prospects, 7(2), 105.}

KATANA™ Zirconia ML (Kuraray Noritake Dental) was the first zirconia on the dental market with integrated shade gradation. First presented at IDS 2013, this material has revolutionized the world of zirconia. Over the course of time, KATANA™ Zirconia UMTL, STML and the change from ML to HTML completed the product portfolio. This article highlights the differences.

By Attila Kun, Hüde in Lower Saxony, Germany

In daily clinical and laboratory routine, we become aware of the diversity of characteristics of natural teeth. Natural teeth impress with their individual optical properties and characteristics, as well as the variety in their shape and texture. The challenge of imitating these aspects with ceramic restorations is a task that we handle in the lab with passion and motivation.

Imitation of the natural tooth requires the appropriate framework material (e.g. KATANA™ Zirconia HTML), an appropriate veneering ceramic or stain system (e.g. Noritake CZR™), along with sensitivity and skill. Although modern materials lay an important foundation, implementation of the restoration is to a large extent an artistic skill. In order to select the appropriate material, depending on the indication, the dental technician should pay attention to the facts and material science (material properties, parameters). Dental sensitivity and craftsmanship are also required for aesthetic realization of the prosthetic. Whether monolithic restoration, thin-layer veneer or individually layered, zirconia offers various advantages as a restorative material (e.g. good mechanical properties, high biocompatibility). In recent years, zirconia has been further developed and optimised through material modifications, and now, new zirconia generations are available. These materials are remarkable due to their translucency and outstandingly aesthetic properties. For certain indications, monolithic restorations can be realized in such way that the optical properties hardly differ from those of a veneered restoration.

Looking back at KATANA’s history

KATANA™ Zirconia ML (Kuraray Noritake Dental) was launched in 2013. This was the first zirconia on the market with a polychromatic shade gradient (ML = Multi-Layered) and has revolutionized the market since. The chroma and saturation of KATANA™ Zirconia ML decrease from cervical to incisal. The market responded very well to the polychromatic discs, so Kuraray Noritake Dental took the next step. In 2015, the KATANA™ family grew with two new translucent materials: KATANA™ Zirconia STML (super-translucent) and UTML (ultra-translucent). Translucency studies have revealed the very high light transmission of KATANA™ Zirconia UTML (43%) and STML (38%). It should be noted that the strength of the material drops with rising translucency. In 2019, KATANA™ ML became KATANA™ HTML. This change included a shade extension from 6 to 14 shades and the adaptation to the VITAPAN Classical shades to ensure an even simpler shade selection for the dental technician for an even better communication between dentist and dental technician. A few years back, the new zirconia stains (CZR™ FC Paste Stain, Kuraray Noritake Dental) were also launched on the market, thus perfecting the KATANA™ potpourri for highly aesthetic yet durable zirconia restorations.

The KATANA™ Zirconia STML layered structure.

Same translucency level as glass-ceramic (e.max Press LT).

With higher flexural strength than glass-ceramic (e.max Press LT).

Comparison of KATANA™ HTML, STML, UTML with comparable ceramic products (Kuraray Noritake overview graphics)

The Japanese word KATANA™ denotes a special kind of traditional Samurai sword. A special feature is the exquisite raw material. The KATANA™ sword combines expedient form with artistic design. We dental technicians aspire to this in our work too. KATANA™ Zirconia offers us the optimal foundation here. The multi-layered KATANA™ materials show a smooth progression of shade and brightness from cervical to incisal. Our experience shows that a functional and aesthetic restoration can thus be implemented in an efficient way.

Application of polychromatic zirconia

Fully anatomical, partially anatomical or as a framework — the polychromatic KATANA™ materials can be used in a variety of ways. The integrated shade gradient displays gentle nuances of enamel, dentin and cervical shade and, in the case of STML, also a translucency gradient. Depending on the indication, the zirconia blanks open up different ways of achieving aesthetic restoration. Especially for complex repairs and anterior restorations, the set-up is an indispensable foundation for us, because the "right" material alone is no guarantee for success. Precise planning is called for. This why we have to first conceive an overall picture. The surface structure, shape and contour are built up manually in wax and after a double scan the wax-up is virtually reduced. This creates a dentin structure or framework that can be milled out of the respective zirconia.

KATANA™ multi-layered materials allow the framework to become a shade-bearing foundation. The CAD construction of the restoration is made in a reduced anatomical crown shape. A dentin core is then milled from zirconia. The ceramic veneer is reduced to a minimum. For a vivid result, the framework can also be characterised with internal stain. Shrinkage during baking is not likely. Shade stability comes from the framework. In addition, the thin veneer layer ensures low shrinkage and lays the secure foundation for high stability and a low risk of chipping. The result is a natural looking restoration. Shine, warmth, naturalness — the optical properties mainly come from the KATANA™ framework!

Differences between and indications for KATANA™ Zirconia HTML, UTML, STML.

KATANA™ Zirconia HTML

KATANA™ Zirconia HTML has high flexural strength. Crowns and bridges (also with a large span) are typical indications. KATANA™ HTML is available in numerous shades, which cover individual requirements in the lab. The material offers optimal optical properties for frameworks. The incident light is transmitted and yet the stump is concealed. The flexural strength is about 1125 MPa.

The framework is designed following a cut-back. The challenge of ceramic veneers (CERABIEN™ ZR, Kuraray Noritake Dental) lies in the subtle, often diffuse, shade variety of the neighboring natural teeth. These characteristics can be implemented using the internal stain technique. The intensive stains can be mixed, for example with Bright (Dilution). Shade depth and three-dimensionality are created once the layering is then covered with luster compound. Luster compounds are a special feature of the Kuraray Noritake ceramic system. The compounds envelop the actual layering like a fine cocoon. Depth and liveliness are achieved thanks to the opalescent properties.

KATANA™ Zirconia STML

Aesthetic restorations need light and translucency, which KATANA™ Zirconia STML offers. The zirconia is modified by the manufacturer adding yttrium oxide, by varying the particle sizes, and increasing its translucency. KATANA™ Zirconia STML also has a polychromatic shade gradient from cervical to incisal. In addition to the shade intensity, its translucency also varies. Therefore, this material is well suited for frameworks in the anterior region (up to three units). The lower translucency in the cervical area is optimal for the shade-bearing framework foundation. The balanced combination of graduated chroma and translucency allow the optical properties of natural teeth to be imitated to the best effect. The flexural strength is 748 MPa.

KATANA™ Zirconia UTML

UTML offers the highest translucency in the KATANA™ family. By modifying the material, the optical properties come close to those of a glass-ceramic. This extends the range of indications to include monolithic restorations in the esthetically visible region, e.g. veneers. KATANA™ UTML has less chroma than conventional zirconia. This is achieved through a consistently high degree of transparency, which brings out the intrinsic shade of the dentin (chameleon effect). KATANA™ UTML is indicated for veneers, onlays or full-contour crowns. The flexural strength is 550 to 600 MPa.

For the purpose of phantom work, we used KATANA™ UTML to produce full-contour veneers. The wafer-thin veneers were milled with a minimum thickness of 0.3 mm. Despite the thinness of the layer, there were no fractures or chipping at the edges. Individual characterization was achieved through the staining technique. The milled veneers display beautiful transparency. In order to perfectly bring out the optical properties, an adhesive bonding cement (e.g. PANAVIA™ V5, Kuraray Noritake Dental) can be used for such delicate restorations.

Wafer-thin veneers (0.3 mm) of KATANA™ Zirconia UTML on the model.

Light and shadow

Something that is often said also applies to aesthetic restorations: "What is essential is invisible to the eye". In order to obtain a perfect ceramic restoration, besides layering, the lifelike, the shape, contour and surface texture are important factors. Therefore—no matter whether monolithic or veneered—suitable preparation of micro- and macro-textures should never be overlooked. The application of gold powder, for example, has proven to be helpful. Even the finest structures become visible under the gold powder. As with black and white images, the eye is not distracted by shade effects. After incorporating the textures and the final touches, manual polishing and adjustment of the shine was undertaken.

Conclusion

The KATANA™ Zirconia series allows us flexible application and the possibility of reproducing the variety of natural teeth in an efficient way. The materials differ in their translucency and mechanical properties.

• KATANA™ Zirconia UTML is suitable for full-contour crowns in the anterior and posterior regions, veneers, inlays/onlays and single crowns in the posterior region.
• KATANA™ Zirconia STML is ideal for crowns and small posterior bridges.
• KATANA™ Zirconia HTML is a high strength framework material for crowns and bridges.

With this selection of zirconia materials, dental technicians are well-equipped and prepared for everyday work and can devote themselves to dental precision work based on individual specifications.

Dental technician Attila Kun
Hannker Dental
Ludwig-Gefe-Straße 28
49448 Hüde
info@hannker-dental.de

Our commitment to you:

Kuraray Noritake dental products offer dental professionals all over the world high-quality products using simple procedures with long-lasting results. With the COVID-19 outbreak, all of us are now going through difficult times which we were not prepared for. Our thoughts are with all those people who are affected by the coronavirus pandemic.

We, at Kuraray Europe GmbH, as the European sales office of Kuraray Noritake Dental Inc., feel a strong responsibility towards our customers and partners, colleagues and communities and we would like to inform you that, in spite of the challenges we are now facing, we will do our best to provide you with the services that you require:

1. Business as usual.

It is both important that we continue to provide products and services to all our customers and at the same time secure the safety of our employees. With that in mind, we have transitioned most of our employees not involved in manufacturing to working remotely and eliminated all non-essential and cross-border travel. This change should not impact in any way how you, our dear customers, contact us. We are ready, willing and able to support you. Clearly, to keep face-to-face interactions to a minimum, we will focus our communication on what is most convenient for you – either a phone call, through email or video chat (Skype, FaceTime or Google Hangout). Whatever is convenient for you!

2. Delivery

As of today, we have sufficient inventory for both dentists and dental labs, as well as reliable logistics. Thanks to our global network of dealer-depots, dental professionals all over the world will continue to have direct local access to our wide range of Kuraray Noritake Dental products. Kuraray Europe GmbH will exert every effort possible to deliver your orders on time. Parallel to this, we kindly ask you to make sure that somebody in your office will be available to receive the parcel. In case, for whatever reason this is not possible, please notify your supplier in advance.

3. Technical Services.
   Our technical service is available to meet your needs.

If there is anything else that we can do to support you, please let us know.

We wish you all the best. Take good care and stay healthy.

Sincerely,

Kuraray Europe GmbH

BU Medical

By Daniele Rondoni, RDT

A middle-aged patient sought dental advice because she felt uncomfortable with the aesthetic appearance of her upper front jaw, specifically regions 11, 12, 21 and 22. Additionally, she was not happy about the diastema between her upper central incisors.

Fig. 1: Initial situation.

The oral examination showed four crown regions (12-22) and revealed that all of them have deteriorated. Tooth 21 had undergone an endodontic treatment, while teeth 11 to 22 have been newly built up. Due to the deteriorated conditions, all affected teeth were taken into consideration in the planning and designing of new restorations, including the intention to close the diastema between the width-to-length-ratio for the incisors.

The best suitable material for a natural look in combination with a close gingival attachment to the restoration is, in this case, zirconia, because of its biocompatibility and gentleness to the gingival region. The KATANA^TM Zirconia series from Kuraray Noritake Dental, offers a line-up of high-quality materials combined with true-to-life aesthetics, due to its natural color gradient within the material.

Fig. 2: Preparations, showing discoloration in the cervical area of tooth 21.

Fig. 3: Occlusal view of the preparations.

Fig. 4: The four zirconia crowns after designing followed by milling.

Fig. 5: Result directly after sintering.

To achieve an even more natural-looking and aesthetic restoration, CZR FC Paste Stains were used externally on the zirconia surface.

Fig. 6: Characterization of the restoration.

As often done, Cervical 2 was used to give an orange tint to the cervical area, to accentuate even better the natural tooth gradation. For the incisal areas, Grayish Blue in combination with Value was used to enhance transparency and opalescence. Same procedure applied to the approximal areas. Mamelon Orange 2 was used to reproduce dark orange stain on the mamelons.

Fig. 7: Result after cementation of the four new zirconia crowns. Their shape and chroma blend harmoniously with the arch.

Fig. 8: The vestibular view showing natural-looking characterization.

During a period of five years, annual check-ups showed intact crowns and a healthy gingiva. Additionally, the durability of the restorations, including their mechanical and optical properties revealed no signs of deterioration.

A strong and durable bond between the tooth and the restoration is a decisive factor influencing the long-term performance of dental restorations. The quality of the bond, however, is not only affected by the bonding agent or cementation solution used, but also by the condition of the bonding surface. For those who would like to ensure clean tooth and restoration surfaces in an easy way, Kuraray Noritake Dental has developed KATANA™ Cleaner, a universal cleaner with MDP salt and a pH of 4.5 for intra- and extra-oral application.

It has been proven that proteins present in saliva and blood have a negative effect on the performance of dental adhesives. Especially in indirect procedures, however, it is impossible to keep the bonding surfaces free of oral fluids. At try-in at the latest, the prepared tooth and the restoration are contaminated and need to be cleaned. Rinsing with water does not have the desired effect, and even with many available cleaners, a certain amount of proteins are usually left on the surface. Tests show that by using KATANA™ Cleaner or by sandblasting, the desired high cleaning effect needed is obtained, without compromising bond strength. This is true for KATANA™ Zirconia restorations, while KATANA™ Cleaner also leads to the desired results on dentin and enamel – surfaces in the oral cavity for which sandblasting and most of the other cleaners are not indicated.

The use of KATANA™ Cleaner offers yet another advantage: the cleaning procedure is extraordinarily simple, quick and neat. The universal cleaner comes in a bottle with an innovative flip-top cap, enabling single-handed dispensing onto the dish. It is then rubbed into the surface of the restoration and the prepared tooth structure or the abutment for ten seconds, rinsed with water and dried. Thanks to the high surface activity of MDP salt, these ten seconds are sufficient to remove the proteins on the substrate almost completely, creating conditions very similar to those found on a non-contaminated bonding surface. Subsequently, the selected bonding agent or cementation solution – e.g. PANAVIA™ V5 or PANAVIA™ SA Cement Universal – is applied according to the maufacturer’s usage instructions.

The result is a strong long-lasting bond, which gives users a peace of mind. Pilot users who have already tested the product agree that KATANA™ Cleaner is the easy way to optimise bond quality and streamline any adhesive procedure.

As co-editor-in-chief of the Journal of Adhesive Dentistry, Prof. Bart Van Meerbeek is one of the most respected authorities on the topic of dental bonding agents. Here, he discusses how they have advanced over the last three decades and what the future of adhesive dentistry might look like.

Prof. Van Meerbeek, how have bonding agents changed and advanced since you first began studying them?

I believe that the great progress dental adhesive technology has undergone in the last 30 years, and the progress in bonding agents in particular, has had a great impact on the field of dentistry and particularly on restorative dentistry, of course. Many of the current restorative dental procedures make use of adhesive materials and techniques and have advanced greatly compared with when I wrote my dissertation more than two decades ago on the topic of adhesion to dentine. Adhesion to enamel is, of course, relatively easy to achieve in comparison with adhesion to dentine, and when I first started researching this topic, I was limited to conducting clinical trials in which we were confronted with a relatively high number of restoration losses in the short term. I was lucky to have been able to witness first-hand the fast advancements dental bonding has made, having conducted research in this field now for nearly 30 years.

At a certain point, the research community started to realise that there is a smear layer in-between, which is created through cavity preparation, and that this layer interferes with bonding. If you want to achieve successful micromechanical and chemical bonding to the substrate, you first need to do something with this smear layer.

After this, we entered the era of conditioners and primers. In the past, the restorative community had been a little bit afraid of using phosphoric acid owing to its potential for pulp irritation. More and more, however, dental professionals began to use etchants with this chemical in them, as well as primers that effectively promoted bonding between the adhesive resin and dentine. While having achieved excellent bonding performance with multistep adhesives in the laboratory, as was later confirmed in clinical studies, further design and development of adhesive materials next focused on simplification and shortening of bonding procedures.

Out of this, two kinds of adhesives, making use essentially of two different bonding modes, arose: the etch-and-rinse adhesives and the self-etch, or etch-and-dry, adhesives. The newest generation of universal adhesives now enables dental practitioners to choose which of the two bonding modes to apply with one single adhesive formulation.

What advantages do bonded restorations offer over more traditional methods?

Bonded restorations are minimally invasive—the dentist doesn’t have to remove non-diseased tissue to create undercuts to keep the restoration in place, allowing for a more conservative approach. Keeping as much enamel as possible should be a goal of any restorative procedure, as it is simply the best tissue to bond to. Although bonding to dentine has always remained more challenging and has actually slowed down our adhesive endeavours for a long time, adhesively restoring teeth, involving also effective bonding to dentine, can today be achieved in a reliable, predictable and durable way.

Along with highly successful implantology to replace missing teeth, lessening the need for bridges, solitary tooth restorations have substantially increased in number. Bonding promoted the additional shift from conventional tissue-invasive crowns to tissue-preserving partial tooth restorations, as modern adhesives can hold such partial restorations in place on rather flat and even non-retentive surfaces. In addition, bonding procedures allow for more natural-appearing restorations to be achieved by techniques to adhesively lute aesthetic restorations made of glass-ceramics and even the strong zirconia ceramics that no longer can be considered non-bondable.

What is your opinion regarding the current generation of universal adhesive solutions?

I think that this generation is very good, but that they are still not always as good as the more traditional gold standard two-step self-etch and three-step etch-and-rinse adhesives when it comes to their intrinsic bonding potential to dental tissue. However, I do see it as a positive that many of these universal adhesives integrate the MDP monomer, which should be considered to be one of the best functional monomers available today, though it needs to be present at a high concentration and purity level.

The MDP monomer is, generally speaking, excellent at bonding to zirconia as well. When it comes to bonding to different kinds of ceramic as well as resin-based composite restorative materials, it is always helpful to know which universal adhesives contain silane and are claimed to no longer need further treatment of the restoration. This has the advantages of lower technique sensitivity and fewer procedural steps—provided that it does, of course, work. There is current scientific evidence that the silane incorporated in today’s acidic aqueous universal adhesives is, however, insufficiently stable. Fortunately, research is underway to develop new universal adhesives that contain other silanes with higher stability in water at higher acidity.

Overall, I believe that a restoration primer that contains a high concentration of silane along with the MDP monomer is still more effective than many universal adhesives for bonding to restorative materials, since these universal adhesives can contain many other ingredients that create a kind of competition within the material to reach and interact with the substrate surface, leading to lesser bonds.

Another shortcoming of universal adhesives is their thin film thickness and relatively high hydrophilicity, promoting water uptake and hence making them sensitive to hydrolytic degradation. In this light, it’s important to note that, when a viscous and hydrophobic flowable composite is applied on top of a universal adhesive, it can make up for this somewhat and allow for durable bonding to take place.

Is the MDP monomer crucial to the ultimate success of universal adhesives? Are there other factors that can influence this?

Well, it’s very clear that the MDP monomer is one of the most effective monomers available, given its primary chemical binding potential to hydroxyapatite. However, there are significant differences in the MDP monomer purity and concentration levels between these products, factors that are affected by whether or not the monomer is synthesised by the company itself or whether this process is outsourced. Essentially, a universal adhesive that contains a high concentration of very pure MDP monomer should perform the best.

Are there any specific advantages that a self-etch adhesive possesses?

The biggest advantage is that it doesn’t remove all hydroxyapatite and minerals present in dentine and so keeps the weaker dentinal collagen protected. Phosphoric-acid etching results in relatively deep and complete demineralisation with collagen exposure, making the bond more prone to degradation. Partially maintaining minerals around collagen using a mild self-etch adhesive additionally allows for strong ionic bond formation to take place when the adhesive in particular contains the functional monomer MDP. In addition, one should be aware that, while chemical binding doesn’t necessarily lead to higher bond strength, it can create better long-term bond durability.

What do you see as the next step in adhesive dentistry?

One possibility is to reduce the number of steps in the adhesion process with the final goal of having self-adhering restorative materials. There have been developments in this direction, including studies and commercial products, though the products haven’t always proved to be very effective and their bond durability is unclear. Now, however, there are newer materials coming to market with claims that they can be used with no pretreatment. Their clinical effectiveness, nevertheless, still needs to be proved and guaranteed before such self-adhering restorative materials could be used as true amalgam alternatives in routine dental practice.

Another possibility, and current R & D hype, is the development of bioactive adhesives. Many dental researchers and many companies want adhesives not only to deliver good bonding performance but also to have certain therapeutic benefits. What exactly a bioactive adhesive is depends on who you’re talking to. Some researchers believe that they should have antibacterial qualities, whereas others state that remineralisation of dentine and pulpal cell interaction are needed to qualify for the term “bioactive”. We certainly need to investigate whether we can give these materials these additional properties, but on one condition: that the adhesive material does not lose any of its original bonding abilities. That, in my opinion, is the biggest challenge for the future of adhesive dentistry.