The bonding surface of a restoration must be conditioned before the restoration can be placed in the mouth using the adhesive cementation protocol. This preliminary treatment establishes the basis for a strong adhesive bond. The type of conditioning required largely depends on the properties of the restorative material used.
Glass-ceramics (incl. lithium disilicate, such as IPS e.max CAD and IPS e.max Press), oxide ceramics (zirconium oxide, such as IPS e.max ZirCAD Prime and Prime Esthetic) and hybrid ceramics clearly differ from each other in terms of materials science, although these materials can hardly be distinguished from each other at first glance.
The type of restorative material used determines the specific pre-treatment protocol that needs to be followed. The methods differ in the way that the bonding surface is activated. They involve either etching with hydrofluoric acid (glass-ceramic) or sandblasting with aluminium oxide (zirconium oxide).
- Etching: The bonding surface of restorations made with glass-ceramic materials (including lithium disilicate) is etched with hydrofluoric acid. In this process, an etching pattern is created which forms the basis for the adhesive bond. Subsequently, a silane-containing primer is applied. The silane bonds to the glass particles in the ceramic and forms a bond to the luting composite.
- Sandblasting with aluminium oxide: Zirconium oxide does not have a glass phase. Therefore, the bonding surface is activated by sandblasting. In order to achieve a strong bond, an MDP-containing primer must be applied. MDP, which is a monomer, can be described in simple terms as an “adhesive” for various types of surfaces (enamel, dentine, oxide ceramic or metal). Note: Silane-containing primers do not work on zirconium oxide, because this material does not contain glass particles.
Step 1: Cleaning of the restoration surface
First the restoration surface is cleaned. Saliva, blood and any other residue (e.g. of glycerine-containing try-in paste) is carefully removed. For this purpose, the restoration is thoroughly rinsed with water and then dried with air.
Step 2a: Etching the restoration surface (glass-ceramic)
Restorations made of glass-ceramic are etched with hydrofluoric acid. This product roughens the surface and creates microscopic pores into which the luting composite can penetrate. In this process, it is very important to follow the safety instructions (health protection measures) and prevent over-etching. Alternative materials to hydrofluoric acid are available (single-component ceramic primers, e.g. Monobond Etch & Prime).
Step 2b: Sandblasting the restoration surface (zirconium oxide)
The surface is activated by gently sandblasting it using moderate pressure (observe the grit size and blasting pressure specified by the zirconium oxide manufacturer).
Step 3: Applying the primer
After the surface has been activated, the restoration is treated with a primer. Products such as Monobond® Plus are universal and can be used on different restorative materials. They establish a chemical bond between the bonding surface and the luting composite.
“Do I need to work with a variety of primers?”
In theory, zirconium oxide restorations must be treated with an MDP-containing primer, while glass-ceramic restorations require a silane-containing primer. Working with a variety of primers, however, makes processes more complex. Moreover, keeping a wide variety of materials in stock in the practice can be quite challenging (shelf life, storage space). Therefore, universal primers such as Monobond Plus offer a convenient solution. This type of primer contains three components: MDP for zirconium oxide, silane methacrylate for glass-ceramics and sulphide methacrylate for precious metal alloys. Because it can be used universally, it allows you to standardise and streamline your workflow. A universal primer reduces the number of products you need use: It satisfies many different requirements and simplifies processes.
Do different types of all-ceramic materials require different primers? Not necessarily: A universal primer such as Monobond Plus allows you to standardise your adhesive cementation processes, minimise sources of error and enhance your efficiency.
“Can I avoid having to use hydrofluoric acid etching in my practice?”
If you routinely use glass-ceramic restorations in your practice, you will know that etching with hydrofluoric acid is an important step, which however, is also quite unpopular. Handling hydrofluoric acid requires great care, and the question of how long to etch often arises.
The duration of the etching process depends on the amount of glass particles in the restorative material. High-strength glass-ceramic materials (lithium disilicate) need to be etched for shorter periods than conventional glass-ceramics. The etching time must be exactly observed to prevent over-etching.
Practitioners who want to avoid the uncertainties of etching, will find a simple solution in Monobond Etch & Prime. The single-component ceramic primer etches and silanates the bonding surface in one step, irrespective of the type of glass-ceramic used.
Can you avoid hydrofluoric acid etching altogether? Yes, Monobond Etch & Prime makes etching with hydrofluoric acid superfluous. Because you can use Monobond Etch & Prime in many different clinical scenarios, it will make your work easier and safer.
“What should I do after having tried in a restoration that has been pretreated in the laboratory?”
After having tried in a restoration that has been pretreated in the laboratory, it is important to gently clean the surface in order to remove any impurities that could have been introduced during the try-in. Renewed etching or sandblasting is not necessary und could even damage the restoration. We recommend using Ivoclean for thorough cleaning of restorations after the try-in. This cleaning agent efficiently removes residues and gently cleans the restoration surface. For the subsequent adhesive cementation, the restoration has to be conditioned with a universal primer (Monobond Plus) in order to ensure optimum adhesion.
Does a pretreated restoration have to be etched or sandblasted again? No, nevertheless, it is important to clean the restoration thoroughly after the intraoral try-in. To ensure a smooth and safe workflow, the use of a special cleaning agent such as Ivoclean is recommended
“Can the clinical adhesive cementation procedure be simplified?”
A clear and consistent protocol helps you to develop a routine which will allow you to approach your treatments calmly and confidently and therefore avoid making mistakes and achieve sound results. Variolink Esthetic offers a versatile solution that is suitable for all types of restorations and materials. A dual-cure (DC) variant is available for all types of restorations and a light-cure (LC) variant for thin and highly translucent restorations. Both variants are based on the same composition: They follow the same cementationprotocol.
Is it possible to simplify the clinical procedure? Yes, certainly, because Variolink Esthetic offers you a straightforward protocol and a coordinated solution. A standardised adhesive cementation protocol for all types of restorations and materials simplifies your routine cementation workflow.
Learn more about the versatility of Variolink Esthetic: Sign up for our adhesive cementation user guide and secure a free test pack for your practice.
