Oxygen is Not Always Welcome

If you have worked with light-curable resin, you’re most likely familiar with the oxygen-inhibition layer that forms on the resin after polymerization. Its presence often confuses clinicians—raising questions about whether or not the material they’re working with has expired. While the oxygen-inhibition layer initially seems peculiar, the explanation for its existence is simple. Light-curable resin never fully polymerizes in the presence of oxygen. Whenever ambient air (thus, oxygen) has access to this type of resin (even on a cured surface), a thin, unpolymerized layer of resin will always remain.  

Although the clinician can simply wipe this layer off, it can actually be very useful. When composite is built in layers, the presence of the oxygen-inhibition layer helps bind each layer of composite to the next. This is because each successive layer seals off the previous one from ambient air, allowing it to be completely polymerized. Removing the oxygen-inhibition layer would prevent a solid and durable bond from forming between the layers.

Conversely, there are situations where the formation of the inhibition layer can prove bothersome, such as when using composite to bond tooth-colored restorations like porcelain inlays and crowns. It is well known that the weak point with a crown or inlay is the cement interface. Therefore, an excess or shortage of composite must be avoided in order to achieve a flush interface.

Because excess composite is so difficult to remove after polymerization, clinicians usually try to remove excess composite before light curing, and herein lies the problem. Once one has wiped the oxygen-inhibition layer off, what was once a flush interface becomes concave and leaves a void.

What to do? Surely, leaving excess composite at the interface, which must then be laboriously removed after polymerization, is not an acceptable solution.

Personally, I prefer to remove all excess composite before light curing and apply a protective gel called DeOx® to the surface to be cured. The syringe and tip delivery, of course, makes the application of DeOx practical. DeOx is almost as clear as glass and doesn’t hinder penetration of light from the polymerization lamp. DeOx does, however, provide a tight barrier against the influence of oxygen, and can be easily rinsed away. Using DeOx allows for complete polymerization while preventing voids in the interface.

DeOx is also useful when performing a restoration that requires the curing light to come in direct contact with the composite. In this case, using DeOx to cover the tip of the curing lamp prevents composite from hardening on the filter and incapacitating the light.

For the most effective application of DeOx, use the Insprial Brush tip. It slightly lowers the viscosity of the gel, making it easier to apply. The fine brush fibers on the Inspiral Brush tip also help to evenly and precisely spread the DeOx.

DeOx makes working with light-curable resin so much easier by preventing voids in the interface without preventing polymerization from the curing light. It also protects the tip of a curing light that must come into direct contact with a composite. DeOx is a simple product with a very particular purpose, and I wouldn’t go without it in my practice.

Categories: Fischer Philosophy, ProductsTags: Composite Restorations, DeOx, Dr. Dan Fischer, dr. fischer, Inc., Inspiral Brush Tip, layering composite, Light Curing Resin, Oxygen Inhibition Layer, oxygen layer dental, oxygen layer resin, Resin, Ultradent products
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Dr. Ann Marie Gorczyca
This is a great Blog. I wish I could share it on social media. Could you add the share buttons at the bottom of your blog?