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Robert Elsenpeter is a freelance writer and frequent contributor to Dental Products Report and Dental Lab Products. He is also the author of 18 technology books, including the award-winning Green IT: Reduce Your Information System's Environmental Impact While Adding to the Bottom Line. As such, he’s particularly interested in the technological side of dentistry.
It’s easy to feel overwhelmed by all the choices on the market. Here’s how to streamline the decision-making process when it comes to purchasing cements.
There are no lack of resin cements on the market, and it’s easy to be overcome by all the choices. But it doesn’t have to be overwhelming. Knowing what’s out there, what’s best for individual cases and what works for one’s personal style are factors that can help you to find the best resin cements.
A primer to resin cements
A good place to start is with a high-level overview of resin cements to understand the classifications into which they’re divided. Each has cases for which they’re best suited, demonstrating different levels of strength, complexity and ease of use.
“I think of resin cements in three categories,” says Dr. Nathaniel Lawson, DMD, director of the division of biomaterials at the University of Alabama at Birmingham School of Dentistry. “Resin-modified glass ionomer (RMGI) cements are the easiest to use but the least retentive. They don't require primers and they are moisture-tolerant.”
While ease of use is, of course, a very appealing characteristic, the more retentive a resin cement, the more finicky it is to handle.
“Self-adhesive resin cements are more retentive than RMGI cements and improve the fracture resistance of ceramic crowns,” Dr. Lawson says. “Since they are self-adhesive, it is not necessary to apply a primer on the tooth, which can be difficult if you are working in an area of the mouth exposed to excessive saliva.”
Those cases requiring the most retention are facilitated by cements requiring additional steps and materials.
“Resin cements that are used with a tooth primer or adhesive are the most retentive cements and they would be my choice for restorations with minimal or no retention (i.e., veneers, onlays, Maryland bridge, very short crowns),” Dr. Lawson says.
One size doesn’t fit all
It would certainly be convenient if one resin cement could do it all. Unfortunately, different cases require different cementation systems.
“In my office, I evaluate it on a case-by-case basis,” says Dr. Jennifer Sanders, DMD, a general dentist in Frenchtown, Montana. “It definitely depends on what kind of retention I need and material that I’m using.”
Finding the right cement for each case is a matter of making some trade-offs, chiefly between retention and ease of use.
“Those tend to be opposite things that we’re considering,” Dr. Sanders says. “It seems like the systems that have the best retention usually take a few more steps to get everything done. I use one cement for my anteriors, or for any really low retention molar, where prepping the restoration monomer and then etching the tooth, and then priming the tooth, and then light-curing, and then doing the cement. So, it’s a lot of steps.
“Whereas in my day-to-day, average crown, I’m using a self-bonding, self-etching cement - kind of an all-in-one,” she continues. “It’s a lot simpler and a lot faster, and that one tends to be my go-to for my average cases, but it doesn’t have the same retention. I don’t feel comfortable using it on a really short crown or a veneer.”
That doesn’t mean that a practice needs to stock countless bottles of resin cements covering each and every possible case permutation. Dr. Lawson says a dentist really only requires three cements.
“Of the properties mentioned above in a cement (i.e., retentiveness, moisture tolerance, ease of use), I don't think that there is a cement that combines all properties,” Dr. Lawson says. “I think that the dentist can get away with three cements: a conventional cement (like RMGI) for the average retentive preparation; a resin cement for bonding to less retentive preparations; and you might also need a light-cure resin cement, if you choose to bond veneers.”
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While ease of use and retention seem to be on opposite ends of the resin cement spectrum, there are variables and factors at play within that spectrum that doctors can use to find their ideal resin cement system.
For instance, the type of etching used is an issue that might factor into one’s decision-making process.
“Manufacturers test their cement strength based on the process they’re recommending,” Dr. Sanders says. “If you want the best results, you do have to follow the process they recommend. If they recommend using a separate etch versus an all-in-one etch-bond and prime, then that’s probably what you want to do.”
Best outcomes are, of course, the primary factor when selecting a cement. However, all things being equal, ease of etching does influence Dr. Sanders’s decision-making process.
“For example, for my average crown that has good retention, I don’t use the cement that I have to etch separately because it is an extra step,” she says.
Curing is another variable in the selection process that will likely vary from case to case.
“In my more translucent anterior cases, I would tend toward the light cure, and I’m fine with that,” Dr. Sanders says. “If I’m placing a crown in the back, then I’d want a dual-cure. I’d use a resin-modified glass ionomer cement if I’m doing a gold crown because I know I’m not curing through that.”
Whether or not priming is necessary is another step that can complicate the process.
“Priming is its own separate step,” Dr. Sanders explains. “I go with the system of cement based on what they’re recommending because that’s what makes the cement work best. That’s what it’s been tested to work best with, based on the conditions they give you. It’s not necessarily something I consider separately. In general, I just look at the system and say, ‘Okay, how many steps are there and is it worth it?’”
Juggling those variables will depend on the dentist and what works best in his or her hand.
“I think that the dentist’s ability to handle the cement is more important than the properties of the cement,” Dr. Lawson says. “If a resin cement is applied in a non-isolated field, all of the retentive benefits are lost.”
With a process as complex as cementation, there are plenty of opportunities for mistakes, but a little planning and forethought can help to ameliorate those issues. For instance, Dr. Lawson observes that indirect restoration preparation - and environmental integrity - are often perplexing.
“People get very confused with how to treat the intaglio of ceramic crowns prior to bonding,” Dr. Lawson says. “Simply put, lithium disilicate needs to be etched and then primed with silane. Zirconia needs to be sandblasted and then primed with an MDP-containing product. It gets a little bit more complicated when you are coordinating these jobs between the dentist and the lab and also when you consider how the crown will be cleaned after try-in. A simple method is to let the lab etch or sandblast the crown, then try it in in the clinic, clean it with one of the commercially available ceramic cleaners (i.e., Ivoclean® or ZirClean®), and then apply the primer. Another common error I see is the use of resin cements in wet environments. Bonding a crown requires isolation just like bonding a composite filling.”
Nothing helps teach a lesson like one’s past mistakes, and Dr. Sanders learned that one product just can’t do it all.
“In the past, mistakes I have made were not thinking as much about what cement I was using,” she says. “Just finding one cement and using it on everything, and then running into cement failures on these less retentive crowns. I have to imagine that’s a pretty common mistake. You get into the groove of doing one thing, and you don’t actually consider, ‘Wait, what would be best for this specific case?’ If you are seeing any failure, really kind of evaluate, ‘What can I do better? What am I not thinking about?’”
Choosing the best resin cement (or cements) need not be an overwhelming endeavor. By factoring in such issues as case needs, the required number of steps and what feels best in the doctor’s hand, the ideal candidates should make themselves known.