Case by Max Andrup

The maxillary right first premolar of this patient had a huge defect on the lingual aspect extending subgingivally. In order to facilitate proper working field isolation for the placement of an onlay, it was decided to elevate the margin using the deep margin elevation (DME) technique. Moisture control is more easily handled with a matrix and composite compared to trying to keep a deep box dry at the placement of an indirect restoration. The preferred method used to maximize the bond strength to dentin was immediate dentin sealing combined with resin coating, while the luting material of choice was warmed light-curing resin composite (CLEARFIL™ AP-X). It shows a superior performance compared to dual-cure luting materials e.g. in terms of conversion of monomers to polymers, time available for excess removal, bio-mechanical properties and polymerization shrinkage stress.

Fig. 1. Pre-operative situaton with clearly visible deep distal margin. In reality, it was even deeper than the picture reveals. The Brinker Rubber Dam Clamp B4 placed here is a life saver in cases with subgingival margins. The buccal wall was still intact. We planned to reduce it to allow the onlay to cover it completely, allowing it to work under compression and thus increasing the fracture resistance.

Fig. 2. Situation after placement of a sectional matrix on thedistal aspect of the tooth. In order to retract the rubber dam mesially, PTFE tape was placed in this area. This allowed me to seal the dentin in a perfectly dry environment. For immediate dentin sealing, the smear layer developed on the dentin immediately after tooth preparation was compacted with the aid of air abrasion (50 μm alumina particles) to provide for the best possible bonding conditions, followed by the application of the bonding agent (CLEARFIL™ SE Protect). Afterwards, the bonded dentin was covered with a thin layer of flowable resin composite (CLEARFIL MAJESTY™ ES Flow). This resin coating ensures that the hybrid layer is thick enough and that the dentin is perfectly sealed.

Fig. 3. After immediate dentin sealing and resin coating. The hybrid layer was left to mature for approximately five minutes. This measure leads to an increased bond strength to dentin, which prevents issues that might occur due to the polymerization shrinkage stress occurring after composite placement. Subsequently, CLEARFIL™ AP-X was applied in small increments, starting in the distal box. In this way, the biobase was built up to the desired height. The main arguments for using CLEARFIL™ AP-X as a replacement for deep dentin are that the modulus of elasticity is within the same range as that of dentin and it exhibits an extraordinarily low polymerization shrinkage.

Fig. 4. Lateral view of the tooth at the day of delivery. View of the tooth at the day of delivery after rubber dam placement and prior to air-abrasion treatment of the biobase, which was performed to remove any remaining temporary cement. Following try-in, the lithium disilicate onlay was cleaned with KATANA™ Cleaner and pretreated with CLEARFIL™ Ceramic Primer. The biobase was sandblasted again for cleaning.

Fig. 5. Onlay in place after selective etching of the enamel with 35 % phosphoric acid etchant, and application of CLEARFIL™ SE Bond to the biobase and the intaglio of the onlay as well as luting with heated CLEARFIL™ AP-X. Excess composite was removed and the composite light cured.

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Fig. 6. Occlusial view of the luted restoration.

Dentist:

Max Andrup graduated from the University of Umeå in 2010 and today runs his private practice in the city of Hudiksvall, Sweden. He has a passion for restorative dentistry with a biomimetic approach.

Case by Dr Paul Guicherit

A girl presented to the dental office after a bicycle accident. She had a traumatized maxillary left central incisor and an abrasion injury was visible on and above her upper lip.

The tooth was restored immediately using CLEARFIL™ MAJESTY ES-2 Universal in the shade UL (Universal Light).

The outcome was excellent due to a great optical integration and an invisible transition between the tooth and the resin composite.

Clinical photo credits: Dr Paul Guicherit

Case by Max Andrup

This is the story of cusp fracture due to cuspal tension. This is a common weakness of amalgam-restored teeth associated with expansion of the restorative material. The affected maxillary right first premolar was restored with a crownlay.

For seating of the crownlay, the use of warmed light-curing resin composite (CLEARFIL™ AP-X) has proven its worth. Compared to a dual-cure luting resin, the selected material offers many benefits including the fact that the heat assists in the conversion of monomers to polymers, the time available to remove excess is almost unlimited, and the composite offers better bio-mechanical properties as well as a lower polymerization shrinkage stress.

Fig. 1. Pre-operative situation. The patient requested for an emergency appointment, where we temporarily fixed the lost buccal cusp and made a new appointment for a crownlay preparation. After removing the amalgam and temporary filling, the remaining amount of tooth structure was quite beneficial with a large lingual cusp and a ring of enamel around the whole tooth.

Fig. 2. The decision was made to reduce the lingual cusp and to place a crownlay working in compression. As the thickness of the cusp was adequate for an onlay, this treatment option would have been equally suitable. After tooth preparation, immediate dentin sealing was performed: For this purpose, I air-abraded the dentin to remove the smear layer and give the adhesive the best condition for a strong bond to dentin. Then, CLEARFIL™ SE Protect was applied to the tooth surface and covered with a thin layer of flowable resin composite (CLEARFIL MAJESTY™ Flow) to ensure a total seal.

Fig. 3. The resin composite surface was air-abraded with 50 μm zirconia particles, followed by selective etching of the enamel with a 35-percent phosphoric acid etchant. After try-in of the crownlay made of lithium disilicate, the tooth surface and the restoration were cleaned with KATANA™ Cleaner.

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Fig. 4. The cleaned crownlay was pre-treated with CLEARFIL™ Ceramic Primer, before warmed CLEARFIL™ AP-X was applied to both tooth structure and restoration for luting. The colour of the crownlay matched the colour of the adjacent premolar, while the visible part of the restored tooth’s remaining structure was stained from amalgam corrosion.

Dentist:

Max Andrup graduated from the University of Umeå in 2010 and today runs his private practice in the city of Hudiksvall, Sweden. He has a passion for restorative dentistry with a biomimetic approach.

By Dr Alessandro Devigus

This video illustrates the Cementation of Katana STML Crowns with Panavia V5.

Dentist:

DR. ALESSANDRO DEVIGUS

Dr. Alessandro Devigus received his degree from Zurich University, Switzerland, in 1987. Since 1990 his working in his own private practice with a focus on CAD CAM and Digital Dentistry. He is also CEREC Instructor at the Zurich Dental School.

Dr. Alessandro Devigus is an active member of the European Academy of Esthetic Dentistry (EAED), founder of the Swiss Society of Computerized Dentistry, Neue Gruppe member, ITI fellow and speaker.

Dr. Devigus is editor-in-chief of the International Journal of Esthetic Dentistry, author of various publications and an international lecturer.

Case by Max Andrup

This patient had requested for an emergency appointment and presented with severe erosive tooth wear in several teeth, a crack in the mesial wall of the maxillary first molar and a failing direct restoration with recurrent decay on the adjacent second premolar. I decided to replace the direct resin composite restoration immediately as this was the main cause of discomfort. It was decided to restore the other defects during the next appointment.

The resin composite of choice was CLEARFIL MAJESTY™ ES-2 (Universal shade concept), an innovative material with a single universal shade designed for posterior restorations. The manufacturer claims that, due to the integration of Kuraray Noritake Dental Inc.’s light diffusion technology, this universal shade nicely blends in with the surrounding tooth structure virtually independent of its colour. Curious about the real potential of this concept, I wanted to put the material to a test.

Fig. 1. Pre-operative situation revealing signs of severe erosive tooth wear, a cracked mesial wall of the first molar and a failed filling on the second premolar with recurrent decay.

Fig. 2. Appearance of the tooth after removal of the direct composite restoration. The recurrent caries is obvious.

Fig. 3. Caries Detector applied to the decayed tooth structure.

Fig. 4. Establishing of a peripheral zone totally free of caries with the aid of Caries Detector. It may be useful to apply the dye several times.

Fig. 5. The final situation after several applications of Caries Detector. The peripheral zone is completely free of caries, which is a strict requirement for the establishment of a perfect seal during bonding. Affected caries stained light pink is not removed not to risk going near the pulp.

Fig. 6. Build-up of the proximal wall with CLEARFIL MAJESTY™ ES-2 (U shade) after the application of CLEARFIL™ SE Protect and a small layer of CLEARFIL MAJESTY™ ES Flow in a thickness of about 0,5 mm. By focusing on the proximal wall connecting to enamel first, the hybrid layer is given the time needed to mature. Not putting a new increment on top of the hybrid layer for the first five minutes will lead to an increased bond strength to dentin.

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Fig. 7. Appearance of the tooth immediately after finishing and polishing. Although the rubber dam is still in place and the tooth structure is not yet rehydrated, it is evident that the composite blends in very well with the remaining tooth structure to form a seamless margin.

Dentist:

Max Andrup graduated from the University of Umeå in 2010 and today runs his private practice in the city of Hudiksvall, Sweden. He has a passion for restorative dentistry with a biomimetic approach.

Zirconia ceramics are increasingly being used for dental prostheses. In the past, they were used as a substructure that was baked with porcelain; nowadays, monolithic zirconia prostheses have been made possible by the introduction of aesthetic zirconia ceramics varieties. They are used more and more, even as RBFDPs (Resin Bonded Fixed Dental Prosthesis).

There is currently quite a lot of discussion about zirconia. So much the better, because it keeps the dynamics of the subject alive. Is it possible to adhesively cement zirconia? Is it permissible to sandblast zirconia? Is it feasible to polish zirconia? Is wear of the antagonist an issue? And so on and so forth.

New dental technologies and materials have been developed in recent years to meet the demand for aesthetic, biocompatible and metal-free prostheses. Although porcelain has been used as an aesthetic dental material for more than hundred years, its restrictions are now well-known. It is the fragility of porcelain (low flexural strength and fracture toughness) in particular which restricts its application in areas where the exertion of massive force on the material is a factor. Zirconia has a high flexural strength and is therefore suitable for multiple dental applications.

Development

The first generation of zirconias used in dentistry belonged to the Partially Stabilised Zirconia (PSZ) class. This type of zirconia, stabilised with yttrium oxide, was composed of a mix of monoclinic, tetragonal and cubic crystals but is no longer used nowadays. The so-called Y-TZP variant was then used for many years, and still is. Its main characteristics are high flexural strength (> 1.000 MPa) and an opaque white appearance. For the most part, this variant is composed of tetragonal crystals of a few hundred nanometers. To keep the material stable at room temperature, approximately 3 mol% of yttrium oxide is added to the composition, which is why it is sometimes referred to as 3Y zirconia.

In order to improve its aesthetic properties, a start was made on the development of a new variety, so-called cubic zirconia. Cubic zirconia is characterised by a high translucence, meaning that a lower flexural strength must be accepted. Admittedly, the flexural strength of this variant is lower than that of the tetragonal variety, but still much higher than the flexural strength of lithium disilicate. It also contains more yttrium oxide; approximately 5 mol%.

Crystal phases

We currently know zirconia crystals in three varieties: monoclinic, tetragonal and cubic. In general, zirconia only exists in the monoclinic phase at room temperature. Monoclinic zirconia has low strength as well as low translucence. Tetragonal zirconia crystals are metastable and can only exist at room temperature after having been stabilised with yttrium oxide, among other metal oxides. The characteristics of tetragonal zirconia are that it is strong, but at the same time devoid of aesthetic
properties. Cubic crystals are stable and ensure improved translucence. Although prostheses made from cubic zirconia are not as strong as the tetragonal variety, they are highly aesthetic, and are even suitable for monolithic restorations in the aesthetic zones.

Multilayer

KATANA™ Zirconia ML, STML and UTML, as well as the latest KATANA™ Zirconia Block, are so-called multilayer zirconias. These products are built up of four layers with an ascending degree of translucency, ranging from the more opaque and coloured body layer (cervical), through two transitional layers, to the translucent incisal edge (occlusal/incisal). The invisible transition from one layer to another is achieved using a unique process. The secret is in the specific distribution of particles during the pre-sintered stage (continuous gap grading). In combination with the cold isostatic pressing method, this ensures material of an outstandingly high quality.

KATANA™ Zirconia Block

The use of KATANA™ Zirconia Block makes it possible to produce a complete monolithic zirconia prosthesis in a short time. This block was developed to be used within the CEREC workflow. After scanning, the prosthesis is ground for approximately 15 minutes and can then be sintered in the SpeedFire oven in just half an hour¹). KATANA™ Zirconia Block shares the properties of KATANA™ STML and can be used for the production of single-unit prostheses such as full crowns for both anterior and posterior applications.

Wear of the antagonist

The question of whether zirconia prostheses are harmful to the antagonist would seem to be justified; after all, this is a very hard material. Hardness, however, does not relate directly to the abrasive properties of a material. Smoothly polished zirconia is minimally abrasive, something which has been corroborated by multiple studies²). Glaze, porcelain, lithium disilicate and even enamel are all more abrasive for the antagonist.

CAD/CAM

Thanks to emerging digital solutions (CAD/CAM) combined with the possibility of executing fixed partial dentures (FPDs) in monolithic zirconia, a fully digital workflow - from scan to prosthesis - is now feasible.

Sandblasting

Sandblasting using alumina is the standard method for the roughening of zirconia. In order to reduce the decline from the tetragonal crystal stage to the monoclinic stage, it is recommended that sandblasting be carried out at a maximum pressure of 2.5 bar using 50 micron aluminium oxide particles as a maximum³). In practice, zirconia is also frequently sandblasted tribochemically, for example, by means of CoJet (3M). The results achieved with this method are variable. In the case of limited pressure (2.5 bar as a maximum) there is a risk that the energy will be insufficient to achieve an effective and complete fusion between the silica and the zirconia surface. It is therefore recommended that CLEARFIL™ Ceramic Primer Plus be used for adhesive connection with the sandblasted surface. The silane in this ceramic primer bonds chemically with the silica, while the MDP bonds with the areas of zirconia not covered by silica. The use of silane alone does not provide an adequate basis for a reliable result⁴). Sandblasting with alumina, however, followed by priming with CLEARFIL™ Ceramic Primer Plus, is a well-proven and reliable method to ensure effective bonding to zirconia⁵).

Not etchable, but certainly bondable

Zirconia is not – or is barely – etchable with the etching technology available (HF). In addition, it cannot be recommended that zirconia be treated with phosphoric acid, because of the bonding of phosphates to the surface of the zirconia, which will inhibit a chemical activation of the surface for some adhesive cementation systems. The question of whether an etching product should be used is a valid one; after all, chemical etching is not necessary to achieve surface roughness. Achieving surface roughness is, however, a logical option, and roughening by means of sandblasting would seem to be the most appropriate method for zirconia. Thereafter, chemical bonding is ensured using a phosphoric functional monomer, preferably MDP.

Adhesion principles

Three basic factors are required to achieve the effective bonding of different materials. In keeping with the principles of adhesion, these are: surface enlargement (micromechanical retention), chemical activity (adsorption and electrostatic bonding) and a high-energetic surface to guarantee proper adaptation.

Adhesive bonding

The best method of adhesive bonding for zirconia is the use of a composite cement containing MDP. Professor Mathias Kern published an article about bonding to zirconia using MDP as early as 1998. This study showed that sustainable resin bonding to zirconia can only be achieved using a composite cement with a special adhesive monomer. The monomer used was in fact MDP. In the meantime, many studies have been published about bonding to zirconia.

On the one hand, these studies concern bonding with phosphate monomers (MDP); on the other hand, attention has been paid to the modification of the zirconia surface to render it etchable. The simplest and most reliable method is to sandblast the surface at a low pressure using aluminium oxide, followed by priming with an MDP-containing primer⁶).

PETER SCHOUTEN,
Technical Manager Kuraray Europe Benelux

1) Depending on the method of grinding/milling.
2) Mörmann W.H. et al. Wear characteristics of current aesthetic dental restorative CAD/CAM materials: Two body wear, gloss retention, roughness and Martens hardness. Journal of the mech. Behavior of Biomedical Materials 20 (2013) 113-125, Janyavula S. et al. The wear of polished and glazed zirconia against enamel. J Prosthet Dent 2013; 109;22-29 Stawarczyk B. et al. Comparison of four monolithic zirconia materials with conventional ones: Contrast ratio, grain size, four-point flexural strength and two-body wear. Journal of the mech. Behavior of Biomedical Materials 59 (2016) 128-138 D’Arcangelo C. et al. Wear Evaluation of Prosthetic Materials Opposing Themselves. Oper Dent 2017 antagonistic surface roughness on the wear of human enamel and nanofilled composite resin artificial teeth. J Prosthet dent 2009; 101: 342-349.
3) Attia A. / Kern M. Effect of cleaning methods after reduced-pressure Air Abrasion on Bonding to Zirconia Ceramic J Adhes Dent 2011; 13: 561-567.
4) Pilo R. Effect of tribochemical treatments and silane reactivity on resin bonding to zirconia. Dent Mater (2017).
5) Kern M. Bonding to oxide ceramics - Laboratory testing versus clinical outcomes. Dent Mater (2014).
6) M. Kern et al., Bonding to zirconia ceramic: adhesion methods and their durability. Dent Mater 14: 64-71, Jan.1998.

Did you know that a complete removal of temporary cement from the abutment tooth with a rubber cup and pumice paste or an ultrasonic scaler is usually impossible? In most cases, some visibly undetectable residues remain on the surface. They will negatively affect the bonding performance of the permanent cementation system you selected. KATANA™ Cleaner is our answer to this problem! Applied after conventional temporary cement removal, it provides optimal conditions for permanent cementation.

All relevant details are revealed in this scientific report.

By Aleksandra Łyżwińska, DMD

The MOD restoration on the maxillary left second premolar of this patient was in need of replacement. It was decided to create a direct composite overlay with CLEARFIL MAJESTY™ ES Flow - Super Low A3, CLEARFIL MAJESTY™ ES-2 Classic A2. CLEARFIL™ SE BOND 2 was used after selective etching of the enamel to establish a chemical bond to enamel and dentin. For the finishing and polishing procedure, abrasive discs were used first, followed by silicon carbide rubber instruments and the CLEARFIL™ Twist DIA system.

Fig. 1. Initial clinical situation revealing the composite restoration to be replaced on the second premolar.

Fig. 2. Occlusal view of the teeth after cavity preparation including cusp reduction.

Fig. 3. Lateral view of the teeth after cavity preparation.

Fig. 4. Matrix band held in place with wedges and two rings.

Fig. 5. Situation after etching, bonding, removal of one ring, and build-up of the interproximal walls with CLEARFIL MAJESTY™ ES-2 Classic in the shade A2.

Fig. 6. Cavity filled with CLEARFIL MAJESTY™ ES Flow - Super Low A3.

Fig. 7. Occlusal surface restored with CLEARFIL MAJESTY™ ES-2 Classic in the shade A2.

Fig. 8. Polishing with the pre-polisher of the CLEARFIL™ Twist DIA system.

Fig. 9. Polishing with the high-shine polisher of the CLEARFIL™ Twist DIA system.

Fig. 10. Appearance of the restoration immediately after rubber dam removal and checking of the occlusal contacts.

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Fig. 11. Linguo-occlusal view of the treatment outcome.

Fig. 12. Lateral view of the treatment outcome.

Dentist:

ALEKSANDRA ŁYŻWIŃSKA
Warsaw, Poland

Aleksandra Łyżwińska, DMD, is a passionate aesthetic and adhesive dentist. Driven by Evidence Based Dentistry, her goal includes using modern composite materials and bonding agents in her clinical practise. In addition to her primary job, she worked as a lecturer and an assistant professor at the Department of Conservative Dentistry and Endodontics of Medical University of Warsaw, her alma mater.

Universal applicability of dental materials – this is a feature highly valued by the products’ users. It allows them to slim down the range of materials needed, which leads to reduced stock inventory and facilitates the establishment of universal workflows. With fewer variables and inconsistencies, all members of the practice team will know exactly what to do and how to do it, which mean less errors and consistent outcomes.

As one of the leading developers and providers of bonding agents, cements and composite filling as well as indirect restorative materials, Kuraray Noritake Dental strongly supports the universality trend in dentistry. Popular examples of universal products for direct restoration procedures are CLEARFIL™ Universal Bond Quick, a one-step dental bonding agent that works with or without a separate etching step, and the filling material CLEARFIL MAJESTY™ ES Flow.

Indirect restorative workflows are streamlined e.g. with PANAVIA™ SA Cement Universal, a self-adhesive resin cement indicated for all kinds of restorative materials, which is always used according to the same universal protocol.

Prior to the use of this product, the dental practitioner should consider cleaning the tooth and the restoration with KATANA™ Cleaner indicated for extra- and intra-oral use and providing optimal conditions for a strong and durable bond.

Both products recently received very positive ratings from the evaluators of Clinician’s Report. Click here to see the evaluations!

By Dr. Michał Sucholdolski

This patient was concerned about the discoloration that had appeared on the occlusal surface of the mandibular left first molar. In an intraoral examination, caries was diagnosed in this area.

As the occlusal surface was almost intact initially, it was decided to restore the tooth with resin composite using the stamp technique. For this purpose, the occlusal anatomy was recorded using CLEARFIL MAJESTY™ ES Flow in the shade A3, which was stamped onto the occlusal surface and fixed to an applicator by light curing. Afterwards, the carious tissue was removed with the aid of caries-detector dye. Following cleaning of the prepared cavity and application of the bonding agent (CLEARFIL™ SE BOND 2), CLEARFIL MAJESTY™ ES Flow (A3) was applied to the cavity floor. The final occlusal layer was created with CLEARFIL MAJESTY™ ES-2 in the shade A3. The stamp was used to transfer the original occlusal anatomy to the new surface before light curing. A natural gloss was obtained by polishing of the surface with the CLEARFIL™ Twist DIA system.

Fig. 1. Initial clinical situation with an occlusal surface affected by caries.

Fig. 2. Appearance of the tooth after the application of caries detector dye during cavity preparation.

Fig. 3. Stamp created with flowable resin composite.

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Fig. 4. Treatment outcome.

Dentist:

Dr. Michał Sucholdolski is a graduate of Silesia Medical University in Zabrze, Poland. He has attended various national and international conferences on microscopic dentistry, endodontic treatment and aesthetic restorative dentistry.

He makes use of innovative dental approaches such as Digital Smile Design, the MicroVision preparation concept, minimally invasive preparation techniques and modern direct restoration techniques.

He is a Member of the Polish Association of Endodontic Treatment and author of scientific work and publications in dental magazine.