Peter Swanson: Cold Atmospheric Plasma and the PZ3

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Intertronics’ MD Peter Swanson discusses the value of plasma surface treatment using the piezobrush PZ3 in dental laboratories

Plasma surface treatment technology is well established in many manufacturing industries including, medical devices, electronics, and automotive. In dental technology, several use cases have been developed, researched, and established to help dental technicians perform tasks more efficiently and achieve better results for patients.

Here Peter Swanson, Managing Director of Intertronics, discusses cold atmospheric plasma technology, the piezobrush PZ3 handheld device, and its applications in dentistry.

Atmospheric plasma technology involves turning a small number of gas molecules into energetic electrons and ions, which can accelerate to high energy and collide with gas molecules to produce short-lived, chemically active materials. Plasma can initiate several physical and chemical processes that both clean and increase the surface energy of materials, to improve the dental technician’s workflow and help improve the restoration’s stability.

Fine cleaning of surfaces

Natural exposure to the air can cause contaminants such as oxides, water, organic substances, and dust to settle on the surface of an implant. These contaminants can affect subsequent processes including bonding, coating, and printing. Plasma can break the organic bonds of heavy organic molecules on the implant’s surface producing lighter and more volatile ones.

The reactive chemical species oxidise organic contaminants, forming molecules such as carbon oxides and water vapour that evaporate to leave the surface in an ultra-clean state. The process also destroys microbial contamination, sterilising the surface. This fine cleaning can be useful in applications such as bonding a titanium abutment to a zirconia crown, reducing the chances of poor adherence.

Improving bonding during colouration

Even when the surface of an implant is clean, some plastics used in dental applications, such as polymethyl methacrylate (PMMA) commonly used in mouthguards, have a low surface energy, which leads to poor wetting. However, the wettability of a surface is a crucial indicator for the quality of follow-up processes.

If the surface energy of a material is below 50 mJ/m squared it becomes challenging to bond to — the liquid just sits as a round droplet on the surface. In dental applications, such as matching the colour of a zirconia crown to the patient’s natural dentition, plasma can help improve colouring results.

In a traditional manufacturing processes, there can be aesthetic issues, such as a conglomeration of pigments at the edge and the glaze/stain not being homogenous. Using plasma treatment avoids these issues.

When plasma is in direct contact with the substrate, electric discharges erode it on the micrometre scale, creating anchoring microstructures that can improve the mechanical binding of a stain. Plasma can also deposit polar hydroxyl and nitric oxide groups on the cleaned surface to increase energy and wettability.

Plasma treatment can therefore increase the surface energy of the zirconia crown, resulting in better wettability and stronger bonding. The process is very effective, does not overheat or visually impact the surface and is safe. As well as improving results, plasma can also achieve a time saving for the technician.

A process that would typically require three lots of firing and finishing can be reduced to just one process, because plasma helps the crown hold the colours and increases the amount of stain deposited in one go.

What does the research say?

Bednarik et al compared cold atmospheric plasma treatment with that of beta radiation for bonding on polypropylene. They found plasma treatment changes wetting behaviour positively, generating polar anchor groups without structural damage. While comparable results could be achieved with beta radiation, plasma treatment is easier to use and can even be handheld.

For example, the piezobrush® PZ3 handheld is the world’s smallest cold atmospheric plasma treatment device. Available with two modules, standard, for the treatment of non-conductive materials such as plastics, and nearfield, for the treatment of conductive materials like metal.

The device is smart and can sense if the incorrect module is being used. The PZ3 is plug and play, requiring only a standard wall socket, no external gas supply, and offers an easy-to-use integrated display. Its low cost means that any dental lab technician can have one on the bench for minimal investment.

Behnecke found positive results in adhesion to polyether ether ketone (PEEK) using the piezobrush PZ3. While sanding, low-pressure plasma and atmospheric plasma were tested, the strongest effect on adhesion was found with cold atmospheric plasma. Takao et al studied the healing behaviour of zirconia composite implants in vivo, finding significantly improved healing behaviour after eight weeks when using plasma treatment.

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