Monobond etch & prime

NO Hydrofluoric Acid No More

Etching and Silanization in one easy step

Monobond Etch & Prime is a self-etching glass-ceramic primer that allows glass-ceramic surfaces to be conditioned without using hydrofluoric acid.

Glass-ceramics form a popular group of materials in fixed prosthetics because they offer high mechanical strength, excellent esthetics and fabrication processes that are well established in dentistry. The popularity of glass-ceramics is further enhanced by the fact that they involve a highly effective cementation technique in which the ceramic contact surfaces are etched with hydrofluoric acid (HF), conditioned with methacrylate silane and then incorporated through co-polymerization with a methacrylate-based luting composite. Restorations that are adhesively placed in such a manner are firmly supported by the tooth structure. This results in a considerable increase in the creative leeway to design restorations. [1, 2]

Monobond Etch & Prime

Glass-ceramics are typically etched with 5 - 9.5% hydrofluoric acid. In the process, the amorphous glass compounds are selectively removed. The result is a very clean, microretentive surface. The subsequent silanization process generates a thin layer of covalently bonded methacrylate groups that co-polymerize with the luting composite when the restoration is seated. The two-step process of hydrofluoric acid etching and silanization has been the subject of numerous publications and is currently regarded as the state of the art for the conditioning of glass-ceramics prior to adhesive cementation. [1, 2]


Effective though it may be, hydrofluoric acid raises safety issues in the dental practice. These issues are related to the toxicity of hydrofluoric acid and not, as is commonly assumed, to its etching effect. On contact, hydrofluoric acid quickly enters the skin and mucous membranes. In the body, it strongly interferes with the body's calcium metabolism and causes severe burns in the underlying soft tissues and sometimes as deep down as to the bones. [3] For this reason, attempts to find an alternative to hydrofluoric acid have been made on several occasions. However, none of these alternatives yielded results on a par with hydrofluoric acid etching [4-7].


Introduced in early 2015, Monobond Etch & Prime (Ivoclar VivadentAG) is a glass-ceramic primer that offers an HF-free and therefore considerably safer procedure to condition glass-ceramic materials. In addition, Monobond Etch & Prime allows glass-ceramic surfaces to be etched and silanated in one easy step - something that none of the other commercially available ceramic primers can do. Table 1 describes the key constituents of the formulation (patent pending) and their functions.


Table 1: Composition of Monobond Etch & Prime

Component Function Additional properties

Ammonium polyfluoride

Etches glass-ceramic surfaces

- HF-free and consequently significantly less toxic

- Stabilizes the silane coupling agent in a highly reactive form

Silane coupling agent: methacrylate silane & silane cross-linking agent

Forms a polymerizable film on the ceramic surface

- Methacrylate silane: strong and durable bonding effect

- Cross-linking agent: accelerates the reaction with the ceramic surface

- Silane coupling agent is stable in storage in the presence of ammonium polyfluoride


Component Function Additional properties

Solvent: alcohol & water Handling

- Ease of use- Excellent film formation- Favourable rinsing properties due to low evaporation tendency

Food colourant Visibility

- Clear contrast with the colour of the ceramic material

- Water soluble and easy to rinse off

Table 1: Composition of Monobond Etch & Prime


A side effect of the break-up of the Si-O-Si bonds ("etching") by ammonium fluoride is that the Si-O-C bonds of the silane system are converted to highly reactive Si-OH groups (silanol). On the one hand, these silanol groups undergo spontaneous condensation and rapidly form insoluble polysiloxane. On the other hand, they, in theory, also lead to a highly effective functionalization of the glass-ceramic surface. The ammonium polyfluroide contained in Monobond Etch & Prime suppresses the condensation reaction of the silanol groups. As a result, Monobond Etch & Prime is the only single-bottle ceramic primer that contains highly reactive monomeric silanol on a steady level to provide surface active compounds at all times.


The application procedure and mode of action of Monobond Etch & Prime can be explained as follows:


1. Monobond Etch & Prime is applied to the glass-ceramic surface using a microbrush and then rubbed into the surface for 20 seconds. In the process, the primer liberates the ceramic surface from adhering saliva proteins and silicone oils.


2. Monobond Etch & Prime is left on the ceramic surface for another 40 seconds without agitating it. The polyfluoride ions now react with the exposed ceramic to produce a roughened, clean and activated surface, onto which the adhesion-promoting silanol compounds are deposited.


3. After the primer has been allowed to react, it is rinsed off from the ceramic surface with a water spray. In the process, the water soluble ammonium fluoride ions are removed. The formation of Si-O-Si bonds begins. The activated ceramic surface has a high reactivity with the silanol groups contained in Monobond Etch & Prime and this enhances the surface functionalization.


The ceramic surface is dried with compressed air until moisture is no longer visible. In the process, the silane compounds undergo final condensation to form a robust layer containing reactive methacrylate end groups on the ceramic surface.


If the ceramic conditioning method using Monobond Etch & Prime is compared with the conventional method, as in Table 2, it can be clearly seen how the conditioning procedure is streamlined with the new primer. While the procedure based on Monobond Etch & Prime involves only one material from one bottle and three treatment steps, conventional conditioning procedures require two materials from two bottles (HF gel, silane primer) and five steps.


As development tests have shown, the new primer allows a uniform contact time to be applied to all types of ceramic materials without posing the risk of over-etching. If hydrofluoric acid is used, however, the contact time must be adjusted according to the concentration of the etchant and the type of glass ceramic being conditioned. As Table 2 shows, Monobond Etch & Prime significantly shortens the treatment time for all ceramic materials compared with the conventional procedure. Enabling users to apply the same contact time for all materials reduces the risk of errors.


Table 2: Comparison: conventional conditioning vs Monobond Etch & Prime


Conventional (HF/silane) Monobond Etch & Prime

Etching (HF)

1. Leave on (2060

s)

Etching &

priming

1. Apply (20 s)

Monobond Etch &

Prime and

leave on (40 s) 2. Rinse with water

2. Rinse with water3. Blow dry

Priming (silane)

4. Apply primer &

leave on (60 s)3. Blow dry

5. Blow dry

2 bottlesApplication time:

80 – 120 s1 bottle

Application time:

60 s

The activating effect of ammonium polyfluoride on the silane coupling agent enables Monobond Etch & Prime to establish a strong and lasting bond with the ceramic and luting composite. The bonding effect on different glass-ceramic materials was assessed in conjunction with the Variolink Esthetic DC luting composite by measuring the tensile bond strength (TBS). The resultant values were compared with those of the conventional combination of hydrofluoric acid etching and Monobond Plus. To test the durability of the adhesive bond, the specimens were aged by subjecting them to 10,000 thermocycles in water (5°C/55°C) before the tensile bond strength was determined. The resulting tensile bond strength values are shown in the next slide.



Figure 1. Tensile bond strength after artificial ageing (10,000 thermocycles); Monobond Etch & Prime vs HF/Monobond Plus (MBP) with Variolinke Esthetic DC.

As can be seen in Figure 1, Monobond Etch & Prime produced tensile bond strength values comparable to those of hydrofluoric acid etching and Monobond Plus on all ceramic surfaces. This means that users can take advantage of the benefits outlined in Table 2 without having to accept any compromises in the renowned quality of the Monobondproducts.


Interestingly, Monobond Etch & Prime is capable of establishing a strong adhesive bond that is resistant to thermocycling without creating the same pronounced etching pattern as the conventional procedure.

As the scanning electron microscope images of IPS e.max CAD in Figure 2 show, the new primer results in a significantly less pronounced erosion pattern than 5% hydrofluoric acid gel. This means that over-etching of the ceramic can be reliably avoided and the ceramic does not exhibit the mat appearance typical of ceramic surfaces etched with hydrofluoric acid.


Figure 2: SEM images of IPS e.max CAD

The reason why Monobond Prime & Etch achieves similar bond strengths as the combination of hydrofluoric acid etching and Monobond Plus even if it produces a less pronounced etching pattern lies in the fact that the ammonium polyfluoride ions induce the formation of reactive silanol groups. When the ceramic is rinsed, the polyfluoride is removed and the silanol groups are no longer stabilized. This gives way to a highly effective functionalization process that offsets the less pronounced etching pattern.


Given its self-etching capabilities, Monobond Etch & Prime features additional innovative properties that conventional glass-ceramic primers cannot offer. Ammonium polyfluoride ensures that surface contamination such as salivary proteins and silicone oils, which may be present after the try-in of the ceramic restorations, are removed, thereby eliminating the need for an additional cleaning step prior to cementation.


Additionally, the issue of how to proceed with restorations that were pre-conditioned in the lab and may, for instance, have become subsequently contaminated no longer poses a difficulty. While a second etching with hydrofluoric acid always incurs the risk of over-etching and damage to the microstructure of the ceramic, this risk does not arise with Monobond Etch & Prime. It is no problem to use Monobond Etch & Prime to re-condition a glass-ceramic restoration that has previously been conditioned in the laboratory either with a conventional combination of hydrofluoric acid and silane or with the new primer.


Conclusion: Monobond Etch & Prime is a self-etching single-component glass-ceramic primer that produces a similar adhesive bond strength as the conventional procedure with hydrofluoric acid and silane. The innovative new material from Ivoclar Vivadent eliminates the need for using hydrofluoric acid as the etchant and the concomitant separate working steps. Monobond Etch & Prime therefore enables safe, easy and reliable conditioning of all glass-ceramic restorations in the practice.


Refrences• 1. Tian, T., et al., Aspects of bonding between resin luting cements and glass ceramic materials.

Dent. Mater., 2014. 30(Copyright (C) 2015 American Chemical Society (ACS). All Rights Reserved.): p. e147-e162.

• 2. Pisani-Proenca, J., et al., Influence of ceramic surface conditioning and resin cements on microtensile bond strength to a glass ceramic. J. Prosthet. Dent., 2006. 96(Copyright (C) 2014 American Chemical Society (ACS). All Rights Reserved.): p. 412-417.

• 3. Ozcan, M., A. Allahbeickaraghi, and M. Dundar, Possible hazardous effects of hydrofluoric acid and recommendations for treatment approach: a review. Clin Oral Investig, 2012. 16(1): p. 15-23.

• 4. al Edris, A., et al., SEM evaluation of etch patterns by three etchants on three porcelains. J Prosthet Dent, 1990. 64(6): p. 734-9.

• 5. Della, B.A., K.J. Anusavice, and J.A.A. Hood, Effect of ceramic surface treatment on tensile bond strength to a resin cement. Int J Prosthodont, 2002. 15(Copyright (C) 2012 U.S. National Library of Medicine.): p. 248-53.

• 6. Comlekoglu, M.E., et al., Preliminary evaluation titanium tetrafluoride as an alternative ceramic etchant to hydrofluoric acid. J. Adhes. Dent., 2009. 11(Copyright (C) 2012 American Chemical Society (ACS). All Rights Reserved.): p. 447-453.

• 7. Kukiattrakoon, B. and K. Thammasitboon, Optimal acidulated phosphate fluoride gel etching time for surface treatment of feldspathic porcelain: on shear bond strength to resin composite. Eur J Dent, 2012. 6(Copyright (C) 2012 U.S. National Library of Medicine.): p. 63-9.


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Monobond etch & prime