Bioactive cements have their benefits—and their drawbacks.
Bioactive materials, including cements, restorative materials, and liners, have been hot topics for several years, and for good reason. Materials that can potentially strengthen, remineralize, or even regenerate enamel have significant positive implications for restorative dentistry.
At the most basic level, bioactive materials have a biological effect on the surrounding tissue. For dentistry, this means a bioactive should bond to the tooth and release ions to promote remineralization at the tooth margins. This is accomplished through the release of calcium and fluoride, which can stimulate reparative functions and help prevent recurring decay. By promoting hydroxyapatite formation on the cement’s surface, this chemical release can assist in creating dentinal bridging while self-sealing and rebuilding the margins—effectively sealing against bacteria that could produce caries.
“A bioactive cement has several potential advantages,” says Nathaniel Lawson, DMD, PhD, director of the Division of Biomaterials at the University of Alabama at Birmingham School of Dentistry. “First, they can help prevent demineralization around the margins of a crown by releasing ions. They can also precipitate hydroxyapatite in an open cement gap. And third, they can precipitate hydroxyapatite so that the interface between the tooth and the cement for a seal.”
Selecting bioactive cements
While many people focus on bioactive restorative materials or liners, bioactive cements play a large role in the restorative process because they pull double duty. They provide cementation while also strengthening the tooth’s enamel. This double duty means their properties differ a bit from their restorative cousins.
“A cement needs different handling properties than a restorative; it needs to flow,” Dr Lawson says. “Cements usually need to have a chemical cure mechanism. But cements do not require the mechanical properties of a restorative.”
“Materials like Ceramir® from Doxa Dental, a calcium aluminate glass-ionomer hybrid material, have technology that was initially developed as a restorative material, but it did not possess sufficient mechanical properties,” Dr Lawson continues. “It was then used for a cement.”
But not all bioactives are created equal. Each one comes with its own benefits and drawbacks.
“We’ve measured several bioactive cements and each have advantages,” Dr Lawson says, referencing research studies he’s completed on bioactives. “TheraCem® from Bisco stands out in its high retentiveness. This is because it is a resin-based cement. Ceramir and Dentsply Sirona’s Calibra® Bio both have the ability to prevent demineralization of the surrounding teeth and have extremely easy clean-up.”
Essentially, it’s important to consider which properties are most critical for a particular case. While Ceramir and Calibra Bio are more moisture tolerant, their retention is not as high. Resin bioactive cements like ACTIVA® BioACTIVE from Pulpdent Corporation or the calcium-releasing cement TheraCem, are less moisture tolerant and require more meticulous isolation but have higher retention and high bond strength to most substrates. TheraCem, in particular, contains a methacryloyloxydecyl dihydrogen phosphate monomer that can bond to substrates, including metal, composite and zirconia—all without necessitating an etchant, adhesive, or dedicated primer.
Additionally, clinicians should take into account how vital esthetics are for each particular case. “It’s important to consider that many bioactive cements are opaque and may affect the color and translucency of glass-based ceramic crowns,” Dr Lawson says.
The potential downsides of bioactive cements
In addition to potential esthetics issues, recent lab studies found that while bioactive cements have varying levels of calcium release, all the bioactive cements tested were found to have less fluoride release than a control resin-modified glass ionomer (RMGI) cement. The bioactive cements did produce crown retention similar to the RMGI cement. However, the study concluded that bioactive cements might not be indicated for adhesively bonded restorations.1 Fundamentally, Dr Lawson explains, while bioactive cements can occlude open margins with calcium phosphate precipitates, the retention strength isn’t always as good as that of adhesive resin cements.
“The big drawback can be weaker retention,” says Dr Lawson. “I would not use a bioactive cement when a preparation has very low or no retention.”
Diving deeper into the benefits of bioactive materials versus resin cements, a 2020 study published by Dr Lawson and colleagues found that while bioactives can help prevent root dentin demineralization, RMGI cements provided the most protection for surrounding teeth.However, the study concluded that both bioactive and RMGI cements are a good choice for patients at a higher risk for secondary caries around the crown margins.2
The final verdict
The bottom line: Assuming a bioactive cement’s properties (such as bonding or esthetics) are high quality and comparable to a traditional cement, there’s basically no disadvantage to using one of these cements. While the jury may still be out on overall efficacy, why not introduce the added benefit of ion release? It certainly can’t hurt. This is especially true in light of the improvements made daily in mechanical strength, designed to make the strength of bioactives comparable to resin-based and glass ionomer cements.
In the end, the future of bioactive cements is bright. Dr Lawson is optimistic and even hopes to see improvements in other areas. “The future of bioactive materials may mean something that would prevent the attachment of plaque biofilm,” he says. “We’ll have to wait and see.”