CEMENTATION IN THE AGE OF DIGITAL DENTISTRY

USING THE NEXT-GENERATION SELF-ADHESIVE CEMENTS

A REVIEW BY TOMOHIRO TAKAGAKI

Introduction

In recent years, the use of CAD/CAM systems for the production of indirect restorations has become increasingly popular.

The shortage of young, qualified staff in the field of dental technology in Japan1) is likely to contribute to a further increase of automated production techniques such as CAD/CAM, which require fewer manual production steps compared to traditional manufacturing techniques.

Also globally, the number of restorations fabricated using CAD/CAM systems is rapidly increasing. This leads to an even more widespread use of innovative, tooth-coloured restorative materials such as zirconia, silicate ceramics and resins.

Demand for placing restorations using the principle of adhesion by resin cements is more and more increasing in daily clinical settings. However, it is difficult and complicated to condition the tooth and restoration surfaces using many primers correctly.

In addition, the combination of many different components is time-consuming, complex and cost-intensive. Self-adhesive resin cements, which do not require conditioning the surface of teeth or some restorations with primers, have been released recently, and have become popular among dental practitioners.

However, there are many reports2) on the dislodgement of resin-based CAD/CAM restorations and full-zirconia crowns that have been placed using self-adhesive cements. Hence, demand is high for a resin cement system that is both simple to use and reliable in performance.

In this document, I explain the fundamental technology of resin cement systems and their range of applications. In addition, I will introduce the method of using a next-generation self-adhesive cement, PANAVIA™ SA Cement Universal (Kuraray Noritake Dental Inc., Fig. 1), as an example.

Adhesive resin cements which require primer treatment.

Classification of resin cements

Conventional resin cement systems usually come with primers which are used for conditioning tooth structure and restorations, respectively. Using early systems, it was necessary for the operator to select the most appropriate primer properly according to the type of restorative material that needed conditioning.

In recent years, resin cement systems incorporating a universal bond as a system component have been introduced. They can also be used as a tooth structure bonding system for direct restorations.

Figure 2 shows the classification of resin cement systems by the system component.

Resin cement systems can roughly be classified into two categories: "Resin cements which require primer treatment", which condition tooth structure and crown restorations using primers or a universal bond, and "self-adhesive cements", which contain functional monomers and do not require tooth surface conditioning.

Representative examples of these two types of resin cements are PANAVIA™ V5 and PANAVIA™ SA Cement Plus (Kuraray Noritake Dental Inc.).

PANAVIA™ V5 is a resin cement which requires the conditioning of tooth structure and crown restorations using primers. This product does not contain functional monomers in the cement itself, which aims at improving the aesthetics and polymerization properties of the resin cement. Therefore, the tooth structure needs to be conditioned using PANAVIA™ V5 Tooth Primer (Kuraray Noritake Dental Inc.) containing the functional monomer MDP, which penetrates deeper into the tooth structure for reliable adhesion. The surface of the restorations is conditioned using CLEARFIL™ CERAMIC PRIMER PLUS (Kuraray Noritake Dental Inc.).

It also contains MDP, this time responsible for creating a strong chemical bond to zirconia and non-precious metals, and y-MPTS, a silane-coupling agent which is effective for conditioning silica-based ceramics and silica-based fillers contained in CAD/CAM restorations.

PANAVIA™ V5 uses two types of primer for tooth structure and restorations, respectively, to make it possible to bond to a variety of restorative substrates while assuring a high level of bond to tooth structure3)

The other product, PANAVIA™ SA Cement Plus, a self-adhesive cement, contains MDP in the resin cement to deliver an excellent bonding performance to tooth structure, zirconia, and non-precious metals. However, since the chemical adhesion to resin-based materials and silica-based ceramics of this cement is limited, resin-based CAD/CAM restorations or lithium disilicate glass ceramic restorations need to be conditioned separately. In addition, the self-adhesive cement does not contain any water so that its bonding performance to tooth structure is not sufficient, compared with resin cements using primers for conditioning4). It is recommended that a universal bond is used for tooth surface treatment when mounting a restoration that does not have any mechanical retention force.

PANAVIA™ SA Cement Plus can be used with a CLEARFIL™ Universal Bond Quick (Kuraray Noritake Dental Inc.) for tooth surface treatment. In this way, a stable adhesion on the part of tooth structure is established (Fig. 4).

Advent of a really "universal" self-adhesive cement

Universal bonding agents and conventional self-adhesive cements have a very useful product concept with regard to the purpose of reducing the trouble of conditioning tooth and restoration surfaces before bonding. As mentioned above, however, there is no denying that the use of such materials gives rise to some confusion in clinical settings because they are not completely "self-adhesive" for crown restorations. For instance, PANAVIA™ SA Cement Plus, a conventional self-adhesive resin cement, needed a separate silane treatment for silica-based ceramics or resin-based CAD/CAM restorations.

This is why PANAVIA™ SA Cement Universal (Fig. 1), a new self-adhesive cement, has been introduced by Kuraray Noritake Dental Inc.. It contains a novel silane-coupling agent (LCSi monomer) (Fig. 5) in the resin cement so that there is no need to condition silica-based restoratives with a silane-coupling agent separately (Fig. 6). In addition, PANAVIA™ SA Cement Universal also contains MDP, the functional monomer already contained in conventional self-adhesive cements, to bond well to zirconia ceramics and non-precious metals without using any primer. Therefore, it can be said that PANAVIA™ SA Cement Universal is really a "self-adhesive" resin cement which can be used for the bonding of any type of indirect restorations. It is also possible to use universal bonds for conditioning tooth structure as before (Fig. 7). This procedure is preferable whenever a particularly strong bond to a tooth abutment is needed.

Conventional silane-coupling agent (y-MPTS) A novel, long carbon-chain silane-coupling agent (LCSi)

PANAVIA ™ SA Cement Plus (a conventional self-adhesive

PANAVIA ™ SA Cement

Placement

of resin-based

CAD/CAM using PANAVIA™ SA Cement Universal

Restorations

Our research results* shows that it is especially useful to use PANAVIA™ SA Cement Universal when placing resin-based CAD/CAM restorations in the mouth. When using conventional self-adhesive cements, it was necessary to perform a silane treatment in order for the cement to bond to the fillers exposed by sandblasting.

PANAVIA™ SA Cement Universal allows the operator to apply the cement and place the restoration immediately after sandblasting (Fig. 8).At our department, we evaluated the bonding performance of PANAVIA™ SA Cement Universal to CAD/CAM resin blocks, using a CAD/CAM resin block as an example. The results showed that PANAVIA™ SA Cement Universal offers the same level of bond strength as the conventional cement system without requiring a separate silane treatment (Fig. 9).

Fig. 7 Difference in the shear bond strength of PANAVIA™ SA Cement Universal to tooth structure with versus without the use of CLEARFIL™ Universal Bond Quick. Even if no conditioning is performed, PANAVIA™ SA Cement Universal bonds to tooth structure to some degree due to the action of MDP contained in the cement. It is advisable to use CLEARFIL™ Universal Bond Quick for the abutment tooth in cases with insufficient mechanical retention or if a particularly strong bond between the tooth structure and the restoration is required.

Fig. 8 Differences in the procedure of placing resin-based CAD/CAM restorations with PANAVIA™ SA Cement Plus and with PANAVIA™ SA Cement Universal. It is not necessary to perform a silane treatment separately when placing resin-based CAD/CAM restorations with PANAVIA™ SA Cement Universal. Sandblasting should be performed immediately before the placement of the restoration, observing the instructions for use of the resin block manufacturer (alumina oxide grain size: 50 µm; air pressure: 1 to 2 bar). If trial fitting of the restoration is conducted in the mouth after sandblasting, the prepared tooth should be cleaned using a phosphoric acid etching agent.

Fig. 9 Micro-tensile bond strength to a CAD/CAM resin block. Without requiring a separate silane treatment, PANAVIA™ SA Cement Universal offers the same level of bond strength as obtained by using the conventional cement system (CLEARFIL™ CERAMIC PRIMER PLUS + PANAVIA™ SA Cement Plus).*

*https://pubmed.ncbi.nlm.nih.gov/34832458/

Conventional self-adhesive cement system (CLEARFIL™ CERAMIC PRIMER PLUS + PANAVIA™ SA Cement Plus)

Case 1

Clinical procedure for placing a resin-based CAD/CAM crown using PANAVIA™ SA Cement Universal (Figs. 10 to 18)

Case study

The clinical procedure for placing a resin-based CAD/CAM restoration (Case 1) using PANAVIA™ SA Cement Universal as a cement is shown in Figs 10 to 18. The clinical procedure for placing a full-zirconia crown (Case 2) also using PANAVIA™ SA Cement Universal is shown in Figs 19 to 27.

Conclusion

It can be said that the self-adhesive cement technology has finally reached maturity with the advent of PANAVIA™ SA Cement Universal, a "really" self-adhesive cement. Of course, some pretreatments of the tooth structure and restorative surfaces are still required, such as cleaning of the restoration surface or removal of temporary cement from the abutment. In all, it may be concluded that PANAVIA™ SA Cement Universal is a reliable and high-performance resin cement, which has simplified the previously complicated pre-cementation procedures.

Case 2

Fig. 27 State of the restoration immediately after placement. Using conventional resin cements, there might be a risk that excess resin cement aroused may not be removed completely. However, PANAVIA™ SA Cement Universal features easy removal of excess cement, and almost no residual excess cement was observed during the clinical check-up.

References

1) Study meeting on the training and retention of dental technicians, Reference material 2, Ministry of Health, Labour and Welfare

2) Kazuhiko Suese: Investigation study on the introduction of CAD/CAM crowns into health insurance coverage during the initial stage. Proceedings of the Academic Meeting of Japan Academy of Digital Dentistry. 5 (1): 85 - 94, 2015

3) San San May Phyo Aung, Tomohiro Takagaki, Aye Ko Ko, Sumayah Halabi, Takaaki Sato, Masaomi Ikeda, Toru Nikaido, Michael F Burrow, Junji Tagami: Adhesion durability of dual-cure resin cements and acid-base resistant zone formation on human dentin. Dental Materials, 2019 in press.

4) Yuki Naruse, Tomohiro Takagaki, Naoko Matsui, Takaaki Sato, Alghamdi Ali, Masaomi Ikeda, Toru Nikaido, Junji Tagami: Effect of alumina-blasting pressure on adhesion of CAD/CAM resin block to dentin. Dent Mater J, 37 (5): 805-811, 2018.

TOMOHIRO TAKAGAKI

Department of Operative Dentistry, Division of Oral Functional Science and Rehabilitation, School of Dentistry, Asahi University Hozumi 1851, Mizuho City, Gifu Prefecture 501-0296, Japan Department of Cariology and Operative Dentistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (part-time instructor)