The Ceramic Primer I’ve Trusted for 10 Years

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

Glass-ceramics are typically etched using 5-9.5% hydrofluoric acid, which selectively removes the amorphous glass compounds. This creates a clean, microretentive surface. Afterwards, silanization forms a thin covalent layer of methacrylate groups that co-polymerize with the luting composite during restoration seating. The two-step process of hydrofluoric acid etching followed by silanization has been extensively studied and is considered the current standard for preparing glass-ceramics before adhesive cementation. [1, 2]

Although hydrofluoric acid is effective, it poses safety concerns in dental practice primarily due to its toxicity, rather than its etching capabilities. Upon contact, hydrofluoric acid rapidly penetrates the skin and mucous membranes. Inside the body, it severely disrupts calcium metabolism and can cause deep burns in soft tissues, sometimes reaching the bones. [3] Consequently, efforts to develop alternatives to hydrofluoric acid have been undertaken multiple times. However, none of these alternatives have matched the etching performance of hydrofluoric acid. [4-7]

Launched in early 2015, Monobond Etch & Prime (Ivoclar Vivadent AG) is a glass-ceramic primer that provides a safer, HF-free method for conditioning glass-ceramic materials. Additionally, it simplifies the process by allowing both etching and silanation of glass-ceramic surfaces in a single, easy step—something no other commercial ceramic primer offers.

The breakdown of Si–O–Si bonds ("etching") by ammonium fluoride results in the conversion of Si–O–C bonds in the silane system into highly reactive Si–OH groups (silanol). These silanol groups can spontaneously condense to form insoluble polysiloxane, but they can also, in theory, promote effective functionalization of the glass-ceramic surface. The ammonium polyfluoride in Monobond Etch & Prime inhibits the condensation of silanol groups, maintaining a steady level of highly reactive monomeric silanol. As a result, Monobond Etch & Prime uniquely offers a single-bottle ceramic primer that continuously provides surface-active silanol compounds.

  When comparing the ceramic conditioning method using Monobond Etch & Prime with the conventional approach. it is evident that the new primer simplifies the process. The Monobond Etch & Prime method requires only one material from a single bottle and involves just three treatment steps, whereas the conventional method necessitates two materials from two bottles (HF gel and silane primer) and involves five steps.

Development tests have demonstrated that the new primer allows for a consistent contact time across all types of ceramic materials without the risk of over-etching. When using hydrofluoric acid, however, the contact time must be adjusted based on the etchant’s concentration and the specific glass ceramic being treated. Monobond Etch & Prime considerably reduces the treatment time for all ceramic materials compared to the conventional method. This uniform application of contact time helps minimize the potential for errors.

The activating effect of ammonium polyfluoride on the silane coupling agent allows Monobond Etch & Prime to form a strong, durable bond with ceramic and luting composite materials. The bonding performance on various glass-ceramic types was evaluated using the Variolink Esthetic DC luting composite by measuring tensile bond strength (TBS). These results were compared to those obtained with the traditional hydrofluoric acid etching combined with Monobond Plus. To assess the long-term durability of the adhesive bond, the specimens were aged through 10,000 thermocycles in water (5°C/55°C) before measuring the TBS.

Monobond Prime & Etch achieves comparable bond strengths to the combination of hydrofluoric acid etching and Monobond Plus, despite producing a less pronounced etching pattern. This is because ammonium polyfluoride ions promote the formation of reactive silanol groups. When the ceramic is rinsed, the polyfluoride is removed, and the silanol groups are no longer stabilized. This facilitates a highly effective functionalization process that compensates for the less pronounced etching pattern.

Thanks to its self-etching capabilities, Monobond Etch & Prime offers additional innovative features that traditional glass-ceramic primers cannot provide. Ammonium polyfluoride ensures the removal of surface contaminants such as salivary proteins and silicone oils, which may remain after the try-in of ceramic restorations, thus eliminating the need for an extra cleaning step before cementation.

The challenge of managing restorations that were pre-conditioned in the lab and may have become contaminated afterwards is now eliminated. Unlike second etching with hydrofluoric acid, which carries the risk of over-etching and damaging the ceramic microstructure, this risk is avoided with Monobond Etch & Prime. It is easily used to re-condition glass-ceramic restorations that have already been treated in the laboratory, whether with the conventional hydrofluoric acid and silane or with the new primer.