Bonding to Zirconia Works Effectively With Primer

BISCO’s Z-Prime™ Plus offers versatility and enhanced bond strength

Nathaniel Lawson, DMD, PhD

Nathaniel Lawson, DMD, PhD, never planned to become one of the leading authorities on dental materials in the world. In fact, he modestly insists that he was not even that strong of a student at the University of Alabama at Birmingham (UAB) School of Dentistry. "I would not have pictured myself then becoming an expert," Lawson says. "I am still not completely comfortable with being considered an authority. I have limitations in other areas of dentistry, but I have focused my energy and attention in one area, and I really enjoy it."

Lawson's modesty aside, he has established himself as one of the foremost researchers in his field, publishing more than 200 articles, abstracts, book chapters, and periodicals related to dental materials and serving as an investigator on more than 75 research grants. In 2020, he was honored as Mentor of the Year by the American Association of Dental Research. Through all his research and mentorship, Lawson has followed in the footsteps of his own mentor, John O. Burgess, DDS, MS, whom he met while applying to dental school. As an undergraduate at Tulane University in New Orleans, Louisiana, Lawson met Burgess at the nearby Louisiana State University and worked on research with him as part of his application process for dental school. Burgess eventually recruited him to UAB's combined DMD/PhD program, but even after earning those degrees, Lawson was uncertain of what career path he wanted to pursue. He tried his hand at clinical dentistry and started a residency, but soon afterward, Burgess called to ask him about teaching and doing research at UAB. "I found my way here almost unwillingly," says Lawson, who is now an associate professor and director of the Division of Biomaterials at UAB School of Dentistry, "but I have ended up enjoying it quite a bit. I really like teaching, and I enjoy mentoring as well as discovering new aspects of dental research. I also like simplifying the research we do into clinically relevant, digestible tidbits of information."

Some of Lawson's favorite research has involved bonding to zirconia—a technique that he was not aware of while in dental school. "When I came back to teach in 2014, I was introduced to zirconia bonding," Lawson says. "Many clinicians are skeptical of bonding to zirconia and even question why anyone would want to do it. However, plenty of scientific studies have shown that there is a hydrogen and/or ionic bond between MDP monomers and zirconia, so zirconia is not an inert material; you can achieve a chemical bond. Why would you? I believe there are cases when it is the best option. For example, I have a case right now that involves a nonretentive Maryland bridge, and I want to use zirconia for its strength at the connector."

For cases like this, Lawson uses materials like BISCO's Z-Prime^™ Plus—a single-component priming agent used to enhance adhesion between indirect restorative materials and resin cements. Z-Prime Plus was the first-ever dedicated zirconia primer, and it significantly enhances bond strengths to zirconia, alumina, and metal substrates due to its unique combination of two active monomers: MDP, a phosphate monomer, and BPDM, a carboxylate monomer. This combination of monomers gives Z-Prime Plus a synergistic effect, resulting in its high bond strengths. Z-Prime Plus is compatible with light-cure and dual-cure resin luting cements, and its convenient, single-bottle delivery offers ease of dispensing. It provides versatility and durability with many different substrates and significantly enhances the bond strengths of other resin cements.* Z-Prime Plus does not need to be refrigerated; it can be stored at room temperature. There is no need to shake the bottle prior to use because Z-Prime Plus is always homogeneous. BISCO recommends applying it after trying in the restoration.

Lawson notes that Z-Prime Plus can be used for bonding to titanium implant abutments or for replacing fractured porcelain-fused-to-zirconia (PFZ) restorations. However, the most common application is for bonding zirconia crowns and bridges. "A reliable primer is critical when bonding to zirconia," Lawson says. "There are two components to the technique. The first is roughening the surface, which is accomplished by sandblasting. The second is chemically bonding to that surface. The primer increases the bond strength, so I would never attempt this technique without it."

Z-Prime Plus is dispensed in a thin coat, which Lawson says is helpful to the process. "If you apply a bonding agent with MDP to the intaglio surface of a crown," he says, "you need to make sure that it does not light-cure from ambient light because that can potentially build up a film thickness. Z-Prime Plus does not have any light-curing components, so that is an advantage."

Lawson and his team at UAB studied the impact of applying Z-Prime Plus on the inside of restorations as soon as they arrived from the laboratory before saliva contamination during try-in. "Once you apply Z-Prime Plus on that surface, it is protected from getting contaminated by saliva," he says. "One of our studies demonstrated that, when saliva was placed on the restoration treated with Z-Prime Plus, we could simply rinse it off and did not need any other kinds of cleaners."

With a reliable primer to increase bond strengths, will bonding to zirconia become more common in the future? Lawson suspects that many clinicians will be persuaded by increasing anecdotal evidence to support the research. "Ten years ago, I do not know if I ever would have thought to use a bonded zirconia Maryland bridge," he says. "There are still indications for which many clinicians are hesitant and might still prefer lithium disilicate as a result, but if they start seeing bonded zirconia bridges remaining strong after 10 years in patients' mouths, they might reconsider. Z-Prime Plus is helping to produce the results that we need."

Key Points

• High bond strengths to zirconia, alumina, and metal restorations, and it is compatible with light-cure and dual-cure resin luting cements.

• Convenient, single-bottle delivery offers ease of dispensing.

• Provides versatility and durability with many different substrates and significantly enhances the bond strengths of other resin cements.*

• Use in conjunction with ZirClean, a cleaning gel designed for the non-abrasive cleaning of the bonding surfaces of zirconia (and other prosthetic restorations) after intraoral try-in.

* BISCO Inc, data on file.

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