By Franklin Tay, BDSc (Hons), PhD

STATE-OF-THE-ART CURRENT ADHESIVES

Manufacturers have adopted an etch-and-rinse approach or a self-etch approach in the design of adhesives for bonding restorative materials to tooth structures, which differ in how these adhesives interact with dental hard tissues. Etch-and-rinse adhesives are offered as two- or three-step systems, depending on whether primer and bonding are separate or combined in a single bottle. Likewise, self-etch adhesives are available as one- or two-step systems. Etch-and-rinse adhesives are often preferred when large areas of enamel are still present, while self-etch adhesives provide more predictable bonds to dentin.

Despite current trends toward fewer and simpler application steps, one-step adhesive systems appear to be less predictable than multi-step etch-and-rinse and self-etch systems. Some manufacturers have recently introduced more versatile single-bottle “universal” or “multi-mode” adhesives that encompass self-etch chemistry but also enable the same adhesive to be used with phosphoric acid-etching in the etch-and-rinse mode. Some universal adhesives also incorporate silane primer for chemical bonding to silica-based ceramics, and methacryloyloxydecyl dihydrogen phosphate (MDP) for chemical bonding to zirconia-based ceramics. Because clinical studies on universal adhesives are short-term, they cannot be considered state-of-the-art in the context of evidence-based dentistry. Conversely, two-step mild, self- etch adhesives have been well-tested in clinical trials and represent the current state-of-the-art for bonding to dentin, with reduced incidence of postoperative sensitivity when compared to etch-and rinse adhesives.

DEVELOPMENT OF CONTEMPORARY ADHESIVES FROM A RESEARCHER’S PERSPECTIVE

The current thinking by researchers is that dentin bonding is not as durable as it was originally perceived. This lack of durability is attributed partially to secondary caries around restorative margins that are devoid of enamel and partially to the degradation of the adhesive joint. The latter may be caused by the hydrolysis of ester bonds in the adhesive component by salivary esterases, or by degradation of water-rich, resin-sparse regions of the hybrid layers by endogenous collagen-bound proteases such as matrix metalloproteinases (MMP) and cathepsin K, that are activated from their dormant preforms to active forms by the acidity of contemporary adhesives. These activated enzymes slowly degrade the denuded collagen matrix within hybrid layers, resulting in gradual loss of adhesion.

Much work has been done in developing therapeutic dental adhesives that are able to resist secondary caries and degradation of the adhesive joint. One of the most thoroughly studied antimicrobial resin monomers is the quaternary ammonium methacrylate developed by Kuraray known as methacryloyloxydodec ylpyridinium bromide (MDPB). This polymerizable resin monomer is incorporated in the two-step self-etch adhesive CLEARFIL™ SE Protect. Recent research has demonstrated that MDPB resin is also an effective inhibitor of both MMP and cysteine cathepsins, thereby providing a mechanism to increase the longevity of resin–dentin bonds by preventing collagen degradation. Indeed, an in-vitro and in-vivo study (Donmez, et al. J Dent Res. 2005;84:355-359) showed that resin-dentin bonds created with CLEARFIL™ SE Protect (aka, CLEARFIL™ Protect Bond) did not degrade after 1 year when compared with a similar self-etch adhesive that did not incorporate the MDPB resin monomer.

MOST COMMON CLINICAL APPLICATIONS OF CLEARFIL™ SE PROTECT

As a board-certified endodontist, the author uses CLEARFIL™ SE Protect as an antimicrobial adhesive to establish coronal seal after finishing root canal treatment to prevent reinfection of the peri-radicular tissues via coronal leakage through the filled root canals (Figure 1 and Figure 2). Another common use of CLEARFIL™ SE Protect is the restoration of the access cavity prepared through a zirconia-based full-coverage restoration. By taking advantage of the MDP component, the author feels more confident that he can bond to the zirconia with a resin composite without causing leakage along the composite-zirconia interface.

Disclaimer: This article was provided by Dr. Tay.

Fig 1. Preoperative radiograph of tooth No. 18. Diagnosis: pulpal necrosis with symptomatic api-cal periodontitis.

Fig 2. Postoperative radiograph of tooth No. 18. Coronal seal was created with radiolucent antimicrobial self-etching adhesive (CLEARFIL™ SE Protect, arrow) and a radiopaque flowable composite, followed by placement of a cotton pellet and a temporary restoration.

ADVANCED NEW FEATURES FOR MORE CONFIDENCE

Studies show that the risk of bacteria remaining in cavities tends to increase with smaller minimal intervention cavities (S. Imazato; Dent. Mater. J. 2009).

CLEARFIL™ SE Protect contains a new functional monomer MDPB, which exhibits an “Antibacterial Cavity Cleansing Effect” (Fig 3).

Fig 3. The bactericidal mechanism of MDPB is presumed to be similar to the well-known antibacterial agent CPC**, which is in many toothpastes and mouth rinses. **Cetyl pyridinium chloride

EXCEPTIONAL RESEARCH RESULTS

Increased durability of resin-dentin bonds

Recent research has demonstrated that MDPB is also an effective inhibitor of matrix metaloprotinases (MMP) that may deplete collagen.

The advantage of MDPB over chlorhexidine (CHX) is that it polymerizes with adhesive resins and cannot leach from the hybrid layer.

(Pashley et al. Compend Contin Educ Dent. 2011)

Fluoride-release

CLEARFIL™ SE Protect contains a patented, specially treated sodium fluoride (NaF); the NaF in CLEARFIL™ SE Protect is coated with a unique polymer capsule that allows release of NaF while the bonding layer physical properties, including strength, are maintained.

Simple proven procedure - avoid technique sensitivity

CLEARFIL™ SE Protect is a two bottle primer and adhesive bonding system.

• No scrubbing needed to achieve good bond strength to tooth structure
• No shaking required Bond itself maintains homogeneity and creates no worries in the quality of the first and last drop of adhesive.

DIRECT RESTORATION

Follow the standard procedures for isolation, moisture control, cavity preparation and pulp protection.

Dentist:

FRANKLIN TAY, BDSC (HONS), PHD

Franklin Tay is Professor and Chair in the Department of Endodontics, College of Dental Medicine, Georgia Regents University, Augusta, Georgia, and a Fellow of the Academy of Dental Materials, as well as a Diplomate of the American Board of Endodontics. With more than 400 papers published in peer reviewed journals, his research interests include biomineralization of collagen scaffolds with apatite and/or silica, remineralization of resin-dentin bonds, antimicrobial sol-gel chemistry, mesoporous silica, and endodontic materials.

First published in COMPENDIUM, April 2014, Volume 35, Number 4.

For the placement of veneers, a resin cement must be selected that supports long-lasting aesthetics, is easily applied, offers a working time sufficient for simultaneous cementation of multiple restorations and provides excellent bond strength. The new “PANAVIA™ Veneer LC” is precisely what you need.

For the pretreatment of the tooth you can use PANAVIA V5 Tooth Primer as shown in our previous workflow video.

BUT did you know that CLEARFIL Universal Bond Quick is also an option? Today’s video demonstrates exactly how. Check it out!

Hypersensitivities make patients suffer, no matter what their cause is. Kuraray Noritake Dental Inc.’s TEETHMATE™ DESENSITIZER is the solution for all of them. Designed to crystallize hydroxyapatite (HAp) from the ground up, the material effectively and durably occludes exposed dentinal tubules and enamel cracks. The tubules may be exposed due to gingival recession, dental erosion or excessive toothbrushing, professional tooth cleaning, scaling and root planning, tooth whitening or restorative procedures. TEETHMATE™ DESENSITIZER provides lasting hypersensitivity relief in all those cases – a fact that is surely one of the reasons for its winning of a Dental Advisor award for the eighth consecutive year.

Consisting of natural calcium and phosphate, the product may even be applied to freshly prepared tooth structure without negatively affecting the bond strength of subsequently utilized dental adhesives or cements.

The consultants of the Dental Advisor conducted a six-month clinical study to be able to evaluate the performance of TEETHMATE™ DESENSITIZER. They selected 27 patients with hypersensitivity issues in their dental practices. Thermal testing with cold air was used to identify the affected teeth, 54 of which were included in the evaluation. For the initial assessment, patients were asked to evaluate their level and frequency of hypersensitivity per tooth on a five-point scale (1 = severe, persistent sensitivity to 5 = no sensitivity). Subsequently, TEETHMATE™ DESENSITIZER was applied according to the instructions for use. Sensitivity was evaluated again immediately after the treatment and six months later. At baseline, 91 percent of the patients stated that they had no or only mild, sporadic sensitivity, which was still the case for 85 percent after six months. This indicates that the product is very effective in providing immediate and even long-term hypersensitivity relief.

Hence, it is not surprising that TEETHMATE™ DESENSITIZER has been among the winners of the Dental Advisor’s Top Product Award every year between 2015 and 2022.

Study results that confirm the material’s effectiveness in reducing pre- and post-operative sensitivity in the context of tooth whitening¹ and indirect restoration procedures² are also available, so that users can count on a reliable performance in a wide range of indications.

1 Mehta D, Jyothi S, Moogi P, Finger WJ, Sasaki K. Novel treatment of in-office tooth bleaching sensitivity: A randomized, placebo-controlled clinical study. J Esthet Restor Dent. 2018 May;30(3):254-258.

2 Shetty R, Bhat AN, Mehta D, Finger WJ. Effect of a Calcium Phosphate Desensitizer on Pre- and Postcementation Sensitivity of Teeth Prepared for Full-Coverage Restorations: A Randomized, Placebo-Controlled Clinical Study. Int J Prosthodont. 2017 Jan/Feb;30(1):38-42.

Case by CDT Daniele Rondoni

When planning to replace Class II restorations, many things need to be considered. In order to select the most appropriate restorative technique and preparation design, it is essential to evaluate the amount and state of the remaining tooth structure, first. After repeated restoration replacement or in teeth originally restored with amalgam, for example, the remaining walls and cusps are often weakened and prone to fractures and cracks. When the cavity walls appear to be too thin or the structure is weak at the time of restoration replacement, it may be better to remove walls and cusps and opt for indirect adhesive restorations (overlays) instead of direct composite restorations. Due to favourable material properties – in particular a high flexural and compressive strength while being gentle to the opposing dentition and not too rigid for the surrounding tooth structures – we often opt adhesive restorations made of KATANA™ AVENCIA™ Block in those situations.

The following clinical case is used to describe the replacement of two composite restorations with overlays made of the innovative hybrid ceramic material.

Fig. 1. Initial clinical situation with composite restorations on the second premolar and first molar in need of replacement. The tooth structure particularly of the first molar was weak, with the distobuccal cusp already fractured.

Fig. 2. Prepared tooth structure ...

Fig. 3. Restorations milled from a KATANA™ AVENCIA™ Block after high-gloss polishing and characterization.

Fig. 4. Finalized restorations on a resin model.

Fig. 5. Adhesively cemented restorations in the patient’s mouth.

FINAL SITUATION

Fig. 6. Treatment outcome with a nice transition from the tooth structure to the restoration.

Dentist:

DANIELE RONDONI, MDT

Born in Savona in 1961 where he lives and has worked in his own laboratory since 1982 with his collaborators. Graduated from the dental technician school IPSIA “P. Gaslini” in Genoa in 1979. He continued his education by attending relevant workshops for the “Italian dental school“ and broadened his professional experience in Switzerland, Germany and Japan. Since 2011 Kuraray Noritake Dental International Instructor.

It is difficult to cover every flowable composite indication with a single viscosity: Sometimes, you need it to stay put where applied or malleable to create a specific shape. In other situations, you need it runny so that it flows into every corner or undercut. In order to meet all those needs, Kuraray Noritake Dental Inc. offers CLEARFIL MAJESTY™ ES Flow with three different levels of flowability: High, Low, and Super Low. The level of flowability is selected depending on the indication, the geometry and size of the cavity. For example, the high-flowability option is best suited as a cavity liner, while the super low flowability variant is preferable in the context of composite veneering.

However, the material has much more to offer, as confirmed by the consultants of the Dental Advisor who have honored the product with an Editors’ Choice and a Top Product Award for the seventh time in a row (Volume 39, Number 01, January-February 2022).

The 29 Dental Advisor consultants tested the medium flowability variant (Low) of CLEARFIL MAJESTY™ ES Flow in their dental practices. They assessed the product’s performance regarding placement/handling, aesthetics, viscosity and polishability. All four properties received an “excellent” rating. CLEARFIL MAJESTY™ ES Flow Low shows no running during placement, while it offers a good adaptation to the cavity walls and even flows into narrow areas. Equipped with Kuraray Noritake Dental Inc.’s Light Diffusion Technology, the material integrates seamlessly with the surrounding tooth structure and a glossy surface is obtained simply by wiping with a cotton roll soaked in alcohol.

Due to these properties and a convincing overall performance, the product received a 98 percent rating, and all 29 consultants stated that they would recommend CLEARFIL MAJESTY™ ES Flow to a colleague. Since 2015, the product has won the Top Product Award time and again, and with its three viscosities, it is likely to become your favourite product for an even broader range of indications.

By Dinesh Sinha, BDS, PHD, Senior Technical and Marketing Manager Dental Division, Kuraray America, Inc.

The all-ceramic restoration market, including that for zirconia, lithium disilicate, and lithium silicate, has been growing rapidly worldwide since the beginning of the 2000s. With the increasing market demand, various dental manufacturers market different dental ceramics that can be used in many dental prosthetic applications. These materials require different minimum thicknesses and preparations to successfully function in the oral environment.

STRENGTH OF DENTAL CERAMICS (FLEXURAL STRENGTH)

The most common method of measuring ceramic strength is by evaluating its flexural strength (in megapascals, MPa). The flexural strength test applies a force on the top of a ceramic specimen, which causes the specimen to bend and fracture. The International Standards Organization (ISO) and the ADA have developed a standard for measuring the flexural strength of dental ceramics. Two methodologies are commonly used today:

• The biaxial flexural strength method (Figure 1): a circular, ceramic specimen/disc that is supported by 3 points, and force is applied in the middle.
• The 3-point bend method (Figure 2a): a rectangular specimen/bar is used and supported by 2 points, and force is applied in the middle. The 3-point bending test for flexural strength is mostly used with zirconia.

Both tests are acceptable; however, ceramics tend to produce higher values when tested with the biaxial method compared to the 3-point bend method. Furthermore, even in a 3-point bending test, if the span lengths (Figures 2b and 2c) of the specimens are increased, ceramic tends to bend abruptly and fail or crack easily. The span length setting in the 3-point bending test for flexural strength plays a critical role in establishing the flexural strength test value. The ISO does provide a guidance on testing that ceramic bars can be in the span length of 12 to 30 mm, but 12 mm and 30 mm can produce completely different flexural strengths. In other words, the shorter the span length, the higher the flexural strength. It is important that clinicians or dental ceramists understand the testing conditions before comparing or selecting the best ceramic for suitable clinical conditions.

Fig. 1: Biaxial Bending Flexural Strength Test.

Fig. 2: 3-point Bending Flexural Strength Test with different span lengths.

INCREASING THE STRENGTH OF CERAMICS

The most straightforward method of increasing the strength of a ceramic is to increase its thickness. This means the preparation depth needs to be higher and may not be favorable in a minimal intervention. There are times when the clinical situation itself may limit the thickness to which a tooth can be prepared (eg, lower incisors). In these cases, another option is to select a stronger ceramic material. In general, dental zirconia has a higher strength compared to lithium disilicate.

Another option is to adhesively (resin) bond the ceramic restoration to the tooth surface. This will easily increase the fracture resistance of a ceramic. Kuraray Noritake Dental Inc. has a legacy of inventing groundbreaking technologies in resins and ceramics. We invented and introduced the Original MDP monomer in 1981. All Kuraray Noritake PANAVIA™ cement brands (Figure 3) contain this MDP monomer. These cements perform best with KATANA™ Zirconia material (Kuraray Noritake Dental Inc.) (Figure 4). Currently, due to the wide availability of different materials, it is important to understand and properly interpret ceramic strength before comparing or selecting material for clinical use.

Dentist:

DINESH SINHA, BDS, PHD

First published in: A Journal of Dental Technology | November/December 2021

One of the key features when talking about cements is the ease of removal of excess cement. Our newest cement - PANAVIA™ Veneer LC - offers the ideal paste consistency, a low film thickness and long working time.

But how about excess removal? Do you wonder how do we compare to other similar products?

Check out this video demonstrating an excess removal comparison between PANAVIA Veneer LC and other brands.

PANAVIA™ Veneer LC

Great solution for challenging task

PANAVIA™ family just got bigger! We are introducing the new PANAVIA™ Veneer LC – the specialist cement that offers aesthetics, excellent paste viscosity, easy handling and 200 seconds(!) working time under ambient light (8000 lux.). Coming in four different shades with matching try-in pastes from PANAVIA™ V5 system, it allows users to take into account the individual shade requirements and deliver highly aesthetic outcomes when cementing veneers, inlays and overlays.

Join our free webinar now and be the first to learn all the details about this new and exciting product from Kuraray Noritake Dental Inc..

ABOUT DR JORGE ESPIGARES, DDS, PHD

Dr. Jorge Espigares received his DDS degree at the Faculty of Dentistry, University of Granada in Spain and obtained his PhD degree under the supervision of Prof. Tagami at Tokyo Medical and Dental University in Japan. Specialized in Cariology and Operative Dentistry, Dr. Jorge Espigares has clinical experience in Spain and UK, and has authored and coauthored full-length research publications with his colleagues at TMDU.

Minimally invasive procedures using highly aesthetic restorations is what patients expect when they seek restorative treatment. With the various types of restorations available today, it is possible to meet these expectations – provided that the right materials are used.

For the placement of veneers, a resin cement must be selected that supports long-lasting aesthetics, is easily applied, offers a working time sufficient for simultaneous cementation of multiple restorations and provides excellent bond strength. The new “PANAVIA™ Veneer LC” is precisely what you need.

What is the workflow you ask? Check out the video to see the full workflow using PANAVIA V5 Primer and CLEARFIL Ceramic Primer Plus.

Are you looking for an easy and simple finishing method for full contour crowns? How about using CERABIEN ZR FC Paste Stain?

Check out the videos created by @danielerondoni and @mr.roberto.rossi and get started!