Preventing air-inhibited layer

Do you need to use an air-inhibition coating during curing if, after polishing, you etch and seal with a composite sealant such as Fortify from Bisco or OptiGuard from Kerr?

Michael Miller, DDS

Do you need to use an air-inhibition coating during curing if, after polishing, you etch and seal with a composite sealant such as Fortify from Bisco or OptiGuard from Kerr?

The air-inhibited layer is an uncured, resin-rich, "slimy-to-the-touch" layer. It forms on the surface of a restoration or on the margins of an indirect restoration that has been luted with resin cement when exposed to ambient room air. You can prevent this wear-prone layer from forming by coating the restoration with a water-soluble material, such as glycerin or commercial products (DeOx, Ultradent).

If you do use one of these products, it is applied prior to curing the surface increment of your restoration. You cure the restoration through the air inhibitor and rinse it off with water prior to finishing it. The result is a restoration with a hard surface, devoid of the air-inhibited layer.

However, using any kind of air inhibitor is only necessary if you have absolutely no excess after curing. This is a rare and highly unlikely occurrence, especially with a direct restoration. In the vast majority of instances, you need to adjust the occlusion or other contours of a restoration.

The air-inhibited layer is immediately removed during these finishing and polishing procedures.

Composite surface sealants, on the other hand, are really designed to penetrate into the finished and polished surface of a restoration, filling any microcracks that have occurred during these finishing procedures.

So an air inhibitor serves a different purpose than a composite sealant. We suggest eliminating the air inhibitor and only using the composite sealant when occlusal wear figures to be heavy. For example, use a composite sealant when a large posterior composite is done on a mandibular molar. Otherwise, its clinical significance is doubtful.

Remember, you don`t use a composite sealant to fill in the gaps between the tooth and restoration. They typically are not viscous enough. (They have a very low viscosity to allow them to penetrate into the microcracks in the surface of the composite.) For sealing gaps at the tooth-restoration interface, use a flowable composite or a pit-and-fissure sealant.

Are desensitizers really necessary under composites?

This is a concept that is highly controversial. Many practitioners believe that using materials such as desensitizers (such as Gluma Desensitizer, Heraeus Kulzer), or disinfectants (such as Tubulicid, Dental Therapeutics/Global Dental) after etching - but before applying an adhesive - will be more effective in minimizing or eliminating sensitivity than when applying the adhesive without one of these products. However, no clinical studies have validated the efficacy of applying one of these products before the adhesive.

In a laboratory study, Gluma Desensitizer was found to decrease the gaps around restorations. But data from our research lab indicate lower bond strengths when Gluma Desensitizer was used as a remoistener compared to the untreated control. Tubulicid also decreased bond strengths in our lab, compared to the untreated control.

We believe that proper use of one of our top-rated adhesives will provide adequate sealing of the dentin to eliminate having to use a desensitizer. Proper use means knowing the optimal way to leave the tooth in terms of moisture before applying the adhesive.

Our tests showed very explicitly that a slight change in the moisture left on the dentin can substantially affect the bond strength of many adhesives. Unfortunately, the directions which come with most adhesives do not adequately and explicitly tell you how to achieve this surface. Therefore, it is not surprising that sensitivity is being noted with these restorations.

Dr. Miller is the publisher of REALITY and REALITY Now, the information source for esthetic dentistry. He is an international lecturer and a fellow of the American Academy of Cosmetic Dentistry, as well as a founding member. He maintains a private practice in Houston, Tex. For more information on REALITY and to receive a complimentary issue of his monthly update, REALITY Now, call (800) 544-4999 or logon to www.reality=esthetics.com.

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