KATANA Zirconia restoration: Pre-treatment for adhesive luting

The prerequisite for adhesive luting is a reliable bond between the tooth and the restorative material. The quality of the bond depends on the resin cement and its correct application. The state of the bonding surface also plays a decisive role. The surfaces of the tooth and restoration must be conditioned and clean. We spoke with Dr. Adham Elsayed.

All-ceramic restorations require adhesive luting. Is this true for all restorative materials (zirconia, lithium disilicate, hybrid ceramics, etc.)?

Yes and no, several factors must be taken into account. The first important factor are the material properties, especially the flexural strength. Fortunately, clear guidelines based on scientific studies are available. As a guideline, all materials with a flexural strength of less than 350 MPa should be placed with an adhesively luted. Correct adhesive luting stabilizes the restoration and tooth structure. Restorative materials of higher strength (e.g. reinforced glass-ceramics, lithium disilicate ceramics, zirconia, etc.) can be cemented with conventional methods. However, some studies indicate that an adhesive luting can improve the overall stability, whereas others show no significant difference.

Another factor guiding the decision for or against adhesive luting is the preparation design. For crowns and bridges, the decisive factor is whether the operator has been able to adhere to the preparation guidelines (minimum abutment height of 4 mm and maximum convergence of 15 degrees)1-5 in order to create the required retention and resistance form for conventional cementation. Minimally invasive restorations, such as resin-bonded fixed dental prothesis (FDPs), veneers and inlay FDPs, are based on a non-retentive preparation design. In such cases, only adhesive luting can ensure adequate retention.

Aesthetics is another important factor. Besides the restorative material, the luting material also has a major impact on the optical outcome. For highly translucent ceramics in particular, it is recommended to resort to adhesive luting. While conventional cements are usually only available as opaque materials, resin composites come in different colours with higher colour stability (PANAVIA V5 or PANAVIA SA Universal).

How should the surface be pre-treated or conditioned for adhesive luting?

Pre-treatment of the surface depends on the structure or microstructure of the ceramic. Silicate ceramics (e.g. glass ceramics) have a glass phase and can be etched. Etching increases the surface area, thus preparing it for adhesive luting. In contrast, oxide ceramics like zirconia as well as composites have no or neglectable amount of glass phase. They cannot be etched. Their surface is conditioned by air-abrasion (with aluminium oxide). This is the only current method which is scientifically proven for achieving a dependable bond with these materials.

How important is correct cleaning of the tooth and restoration surface for the quality of the bond?

The restoration surface must be decontaminated immediately prior to luting. Contamination must be removed thoroughly. Rinsing with water or alcohol has been shown to be insufficient. Therefore, cleaning solutions such as KATANA Cleaner have been developed.

Rub it in, rinse and dry—that's all—for optimal bonding procedures. Unlike other cleaning products, which have to be rubbed in for longer and are only suitable for extraoral use due to their high pH value, KATANA Cleaner is applied within 10 sec. and is suitable for both intraoral and extraoral use.

Any contamination is detrimental for the adhesive bond. At try-in of the restoration, for example, its surface becomes contaminated. Saliva, possibly blood, etc. accumulate and the proteins contained act to isolate all subsequently applied components (e.g. the primer). Any contamination must therefore be thoroughly removed prior to the bonding procedure. This is also the case for direct adhesive restorations. KATANA Cleaner offers a simple and quick way to accomplish this task.

What makes KATANA Cleaner so interesting for the user?

The special features of KATANA Cleaner are its integrated MDP salt and mild pH-value. Let's look at the function of the MDP salt. Rubbed in (for 10 seconds), the cleaner causes the contaminant particles (e.g. remnants from the work process, proteins from saliva, blood, etc.) to adhere to the MDP salt, like a magnet. The contamination is flushed out of the surface by rinsing with water. This ability is attributable to the MDP salt and makes KATANA Cleaner interesting and easy to use. In addition, the pH-value allows us to use the cleaning solution both intraorally and extra-orally, which is another special feature. We generally recommend the use of KATANA Cleaner—for both direct and indirect restorations. Thanks to the universal applicability of the cleaning solution, only one material is needed, while the time required is extremely low. Even for bonding abutments on a titanium base, cleaning with KATANA Cleaner is recommendable as it provides for an ideal basis (before applying the primer). In this case, contamination (e.g. finger grease, residues of the air abrasive) could also act as an insulator and impair the quality of the bond.

References:

1. Ladha K, Verma M. Conventional and contemporary luting cements: an overview. J Indian Prosthodont Soc. 2010;10(2):79-88.
2. Edelhoff D, Özcan M. To what extent does the longevity of fixed dental prostheses depend on the function of the cement? Working Group 4 materials: cementation. Clin Oral Implants Res. 2007;18 Suppl 3:193-204.
3. Güth JF, Stawarczyk B, Edelhoff D, Liebermann A. Zirconia and its novel compositions: What do clinicians need to know? Quintessence Int. 2019;50(7):512-20.
4. Smith CT, Gary JJ, Conkin JE, Franks HL. Effective taper criterion for the full veneer crown preparation in preclinical prosthodontics. J Prosthodont. 1999;8(3):196-200.
5. Uy JN, Neo JC, Chan SH. The effect of tooth and foundation restoration heights on the load fatigue performance of cast crowns. J Prosthet Dent. 2010;104(5):318-24.

• 13 déc. 2022

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