This summary is based on the Journal of the American Dental Association Perspectives-Observations (December 2013)
Advantages of Flowable Resins
- Flowable resins also vary markedly in viscosity. Some flow almost like water when placed in tooth preparations, and others are relatively putty-like.
- All brands of flowables are less viscous than are conventional composites.
- The major reason flowables are popular is one significant singular advantage they flow.
Limitations of Flowable Resins
- The polymerization shrinkage and stress of some flowable composite brands have been shown to be more than those of conventional composites.
- Recently it has been shown that some new brands of flowables now exhibit wear characteristics similar to those of conventional composites.
- The strength of some flowables has been shown to be lower than that of conventional composites. In recent years, nanofillers and microfillers have been added to most resin-based composites—and the filler content of some newer flowables is comparable with that of conventional resins.
- Depth of resin cure of most flowables has been shown to be less than acceptable for the now in-vogue “bulk fill” technique.
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Flowables have definitely changed the way I practise restorative dentistry. Most importantly, in class 2 restorations I use flowable liner, just a little, then without curing I pack conventional composite until most of the flowable comes out. Then cure and build up this way in 2 -3 mm increments. Guess what, hardly any pullback gaps. Try it, you just might like it!
I’m with tomasz on this one for sure. I notice less sensitivity as well.
A lot of dentists lack a fundamental understanding of the science of the materials they are using.
Quite obviously, flowable composites have less filler particles… and higher ratio of resin… and therefore lower viscosity.
Efforts are constantly made to make conventional composites more highly filled to improve physical properties and minimize shrinkage. A less-filled flowable composite obviously has inferior physical properties and more shrinkage (compared to conventional composite). In theory, conventional composite should be better.
However, in practice, the flowable materials provide an EASE of placement. This is not only for the provider’s benefit. As everyone knows, composite resin restoration are extremely technique sensitive. A restoration placed under ideal conditions can perform very well, however one placed under compromised conditions can be vastly inferior. Therefore, one must consider not only the physical properties of the material. If the flowable material allows the provider to place the restoration more quickly and effectively… minimizing voids… this can translate to improved clinical outcomes.
As far as bulk fill, I believe there are several advantages, however a self cure material is necessary for those advantages to become fully actualized. This translates to a self cure glass ionomer base or a self curing composite resin… ideally dual cure to facilitate placement. With bulk fill light cured materials, there are potential severe limitations, as the author of this article has indicated.