Tips and tricks for working with flowables

March 18, 2019

Find out how you can make this type of composite work for your dental practice.

Flowable composite is one of many categories of dental composite. “Flowables” are known for their excellent handling properties. They’re also known for increased polymerization shrinkage and reduced mechanical properties as compared to the other composite categories.

However, if you can count on one thing in dental materials, it’s change. Let’s take a closer look at this type of composite and how it can work for your practice. DPR spoke to three clinicians to get their take on flowable composites and how you can go with the flow in your practice.

The advantages of flowables

Flowable composites have a lower viscosity than their thicker counterparts. They can flow into the nooks and crannies of preparations that might otherwise be difficult to fill with a thicker composite. Flowable composites usually come in a syringe with a small-gauge needle to help them do their job in small preparations.¹ Another advantage of the lower viscosity is flowables can form very thin layers, which prevents bubbles or voids in the material.²

The disadvantages of flowables

Of course, what makes flowables great for some restorations limits their effectiveness in others. The lower filler content of some materials can lead to more polymerization shrinkage.³ Also, when there’s less filler present, it can lead to a reduction in the composite’s mechanical properties.⁴

However, not all flowables are alike. Newer materials have higher filler contents than their predecessors, which improve some of the well-known disadvantages. These improved materials can be used for more than in the past and with similar results to more viscous composites.⁵

Flowables: suffering a bad rap from an inauspicious start?

Nathaniel Lawson, DMD, an assistant professor in UAB’s School of Dentistry’s division of biomaterials, thinks the reputation for reduced mechanical properties is just a bad rap for flowable composites. The materials are improving in strength and wear all the time.

When introduced in the ‘90s, the first flowables were more viscous because manufacturers reduced the filler content. Dr. Lawson estimates it was in the 50- to 60-percent range, which decreased their strength and wear properties. He says that reputation has stuck with flowables still today.

However, flowables in the post-2010s are 70 to 80 percent filled. Today, Dr. Lawson explains, flowable composites are approximating the mechanical properties of highly filled composites as far as strength and wear.

“Flowable composite is less viscous, so it adapts better. However, to get that flow, manufacturers had to take out some of the filler particles initially,” Dr. Lawson explains. “Now, they've manipulated the size of the particles, and that's how they've been able to obtain the different handling properties without reducing filler content. Also, that's how they've been able to maintain the strength.”

In 2015, Dr. Lawson and his team at UAB published a study in Operative Dentistry. The study compared the two-year recalls of both flowable and conventional highly filled composite resin in Class I restorations. Flowables had similar clinical performance after two years to highly filled composites in restorations of this type.

More recently, the team published a 2018 study, which reported similar performance of a flowable composite as a conventional, highly filled composite in “small- to moderate-sized occlusal restorations.”

“I'm not afraid to use flowables in posterior restorations. My hesitation in using them is if I have some area I want to sculpt because they don’t have great sculpting properties,” Dr. Lawson says.

However, Dr. Lawson says that some flowables have a slightly higher polymerization shrinkage percentage.

“The wear and strength of flowables have been improved, but the shrinkage hasn't been resolved. It's still an issue,” Dr. Lawson says.

According to the Journal of Conservative Dentistry, flowables need more study. The current literature on their success is too limited to make predictions about their long-term success.⁶

However, based on the research available at the time of publication (2017), the scientific evidence does suggest that flowables had similar clinical efficacy after three years to their conventional composite counterparts for both carious and noncarious lesions.⁷ Furthermore, they perform well for occlusal cavity preparations, as sealants for pits and fissures, minimally invasive Class II restorations and noncarious cervical lesions.⁸

Outside of scientific study, however, flowables have their uses in your everyday practice. Here are a few ways our clinicians shared that you can use flowables to great effect in your direct composite restorations.

Continue to page two to read more...

Tip #1: Use it to line the bases of your restorations

Most clinicians agree that flowable composite has outstanding performance as liners for deep restorations in the posterior. It’s the most common use of flowable composites in day-to-day practice.

Les Crawford, DDS, practices in Maumee, OH, outside of Toledo, with Namay Dentistry. Dr. Crawford uses flowable composite in deep posterior direct restorations with irregularities on the surface of the base. Then, he finishes with a high-filler packable composite. The low viscosity and self-leveling properties of the flowable composite make it an optimal base.

“It flows right into all those weird grooves and little caverns I make when I'm taking out the decay. It levels the surface and makes it a little bit easier to fill for the rest of it afterward,” Dr. Crawford says.

Dr. Crawford says he only uses flowable composite in direct posterior restorations where it has proven to work. He feels that using it in the anterior is risky for esthetics. Flowable composite is more translucent than conventional composite, Dr. Crawford explains. When used in anterior restorations, the light passes through the composite into the open oral cavity behind and the tooth looks gray.

"No one wants a gray tooth,” Dr. Crawford says.

Tip #2: Lay the groundwork for your flowable carefully

Edward Kusek, DDS, is a private practice general dentist in Sioux Falls, SD, with 34 years of experience. Dr. Kusek also uses flowable composite as a base or a liner in the box area of his direct restorations with bulk fill composites.

After placing two layers of his bonding agent, Dr. Kusek says he adds a thin layer of flowable composite and cures it. The flowable helps prevent any voids as he compresses the bulk fill composite on top.

“If I'm doing a Class II, I like to put a little bit of flowable into the box area and go over it with an explorer to thin it out and ensure I get out any bubbles. I put the flowable in there and cure it because it seals that box up a little bit better for me,” Dr. Kusek says. “Mine isn’t super thick, so it will level out, but you still need to move it around a little bit.”

One of the things Dr. Kusek looks for in his flowable composite is high radiopacity. It helps him distinguish between the restoration and secondary caries at future appointments with the patient.

“Otherwise, when the patient comes back in, you'll see a little dark line in the area where you placed it, and you might confuse that with decay,” Dr. Kusek says.

Tip #3: Explore new ways to use flowable properties for better patient outcomes

Dr. Kusek also likes to use flowable composite in incremental layers for his Class V restorations. He finds that he doesn’t have the same challenges with polymerization shrinkage and wear problems around the margins that he had with past products.

Dr. Kusek says he also finds flowables useful with his full-mouth restoration cases. He uses a flowable composite to lute overdenture materials together, which helps to prevent voids. Also, when delivering a screw-retained appliance, he uses a flowable to seal up the access holes. Depending on the location of the access hole, he’ll use the tooth-colored or gingival-colored composite option.

“It has a better feel for the patient,” Dr. Kusek says.

Dr. Crawford also uses flowable composite when working with Invisalign clear retainers. Invisalign has attachments that take the place of the brackets in conventional braces.

“We put a little flowable in the tray, set the tray on the teeth and then cure it with the light. Then, once we take the tray off, they're onto the teeth,” Dr. Crawford says.

Dr. Lawson agrees that flowable composite is excellent to use in the boxes of Class II restorations. Additionally, he’ll sometimes use it in narrow occlusal preparations, particularly when it’s easier to flow composite into the prep rather than pack it.

“Sometimes you can get them to adapt into smaller preparations in the anterior region like an incisal-edge-type filling,” Dr. Lawson says.

References

1. Baroudi, Kusai and Jean C Rodrigues. “Flowable Resin Composites: A Systematic Review and Clinical Considerations” Journal of clinical and diagnostic research : JCDR vol. 9,6 (2015): ZE18-24.

2. Ibid.

3. Ibid.

4. Ibid.

5. Shaalan, Omar Osama et al. “Clinical evaluation of flowable resin composite versus conventional resin composite in carious and noncarious lesions: Systematic review and meta-analysis” Journal of conservative dentistry : JCDvol. 20,6 (2017): 380-385.

6. Shaalan, Omar Osama et al. “Clinical evaluation of flowable resin composite versus conventional resin composite in carious and noncarious lesions: Systematic review and meta-analysis” Journal of conservative dentistry : JCDvol. 20,6 (2017): 380-385.

7. Ibid.

8. Ibid.