Examining the world of self-etch

Jan. 1, 2005
If I use a self-etching adhesive, it won�t etch uncut enamel. How do you “cut” all enamel margins of a preparation? And, if I have to etch the enamel with phosphoric acid, then why am I using a self-etcher? I am concerned with microleakage and sensitivity.

By Michael Miller, DDS

If I use a self-etching adhesive, it won’t etch uncut enamel. How do you “cut” all enamel margins of a preparation? And, if I have to etch the enamel with phosphoric acid, then why am I using a self-etcher? I am concerned with microleakage and sensitivity.

With virtually all preparations, there is some alteration of the enamel cavosurface margin. An exception to this rule could be a cervical noncarious lesion, where you may merely roughen the dentin but you may not alter the enamel margin. In cases such as this, you would be safer by etching the enamel with phosphoric acid, even if you plan to use a self-etching adhesive. Be sure to rinse the acid by directing your air-water syringe in a coronal direction to keep any of the etch-infused rinse water off the dentin. Otherwise, if you have a more conventional preparation with a beveled enamel margin, a self-etching adhesive will be quite effective when it comes to sealing the enamel margin.

I have heard you should use the accompanying company’s adhesive/primer along with its resin cement (i.e., OptiBond and Nexus2). Does it really make a difference if one crosses over and mixes components (e.g., OptiBond with RelyX Veneer Cement)?

As long as the curing mechanism is the same (light-cured adhesive with light-cured cement), crossing over brand lines is perfectly acceptable and has been done clinically for many years.

I have two patients with anterior veneers that are five to 10 years old. They have developed some staining at the margins. Would wearing bleaching trays remove the staining? Are there any precautions about strength to use? I was considering Day White.

It is highly unlikely bleaching will help stained margins, which is a sign of micro-leakage. You can try polishing the margins, but if the staining has actually penetrated under the veneers, you will probably need to remove it by sandblasting with a very fine tip or using a small diamond in a highspeed and then restoring the defect with a flowable composite.

Have you had any untoward results when cementing Empress2 crowns with glass ionomer cement as opposed to bonding?

After the Advance debacle, we advised strongly against using any type of ionomer cement for a metal-free restoration. Therefore, while Empress2 was on the market, we did not lute it with any cements other than resin. It has since been replaced with Eris, but we still believe a resin cement is the product of choice to use. Nevertheless, we have had no reports of restorations fracturing when luted with ionomers over the last few years.

A friend endorsed the use of superoxyl for obtaining hemostasis and I am unfamiliar with this product. Do you recommend it and are there any contraindications to its use?

Superoxyl is essentially liquid 35 percent hydrogen peroxide. It is primarily used as a power bleach, but has also been advocated as a chemical cautery for spot hemostasis. While it can be effective for very limited use, it can also cause very severe soft-tissue burns. We don’t advise its use due to the potentially severe untoward effects.

Could you please illuminate why using diamond burs dry to finish composite is contraindicated?

Diamonds, whether used for cutting tooth structure or for finishing restorations, are much more efficient when used with water spray, which helps to keep them from clogging with cutting debris. Finishing carbide burs also clog with cutting debris, but to a much less degree than diamonds. Once a diamond of any type gets clogged, its cutting efficiency drops substantially.

REALITY has given Bondlink a 5-star rating, but do you know how long the bond to self-cure resin will last? Also, is there any information about microleakage?

Good question about the longevity of the bond with Bondlink (or any other adhesive). We have not performed long-term adhesive testing on Bondlink (or any other adhesive). There are studies that suggest bond strength of many hydrophilic adhesives can weaken or hydrolyze over time, but clinical evidence of this phenomenon is lacking. Nevertheless, since Bondlink is not the primary adhesive and is merely facilitating the adhesion between single-component adhesives and self-cure materials, we would assume this bond would be stable. Since most of these self-cure materials are being used for core materials and since most core materials are covered by the crown, failure of the bond could only be shown by crown dislodging with the core inside. The same applies with microleakage. Since the core is typically covered with the crown, microleakage is not usually tested with these materials.

I have experienced a problem with veneers that debonded from the porcelain side because there was still some composite on the tooth. I have racked my brain to find out why. I have been doing veneers for years with no problem, but when I switched labs and materials almost two years ago to try to improve my esthetics, this is what happened. Before this happened, I was using Nexus2, but I was using the RelyX kit when this happened. The lab said they etched with HF 9 percent for one minute, then I silanated and bonded.

The only thing I can put my finger on is the fact that Ivoclar said that the lab should have used 4-5 percent for one minute or 9 percent for 30 seconds. They said this could have been the problem. You have said in one of your previous responses that you didn’t think this was the problem. Do you still believe that and if not, do you have any other input? Since all this happened, I have switched labs and products, but I still wonder why this happened. Also, why do you think some veneers are still bonded and some are not? Do you think they all will debond over time? I did about 55 veneers and 12 have debonded. One last thing - I found out some of the resin in the kit was expired but the bonding agent and silane was not. My Patterson rep said it could have been in storage for a while, but he doesn’t know why the resin expired, but the bonding agent and silane were not.

The percentage of HF and the etching time are highly unlikely reasons for debonding. It is also difficult to speculate why some veneers have debonded while others have not. Certainly, expired materials could be the source - we emphasize paying great attention to these dates. All components to a kit do not typically have the same expiration date. The expiration date listed on the kit is typically based on the product that has the shortest shelf life. You should always check the shelf life listed in our annual edition and the expiration date of the product when you receive it. If the shelf life is two years, but the expiration date on the product only indicates you have one year remaining to use it up, the product has probably been sitting on a distributor’s shelf for one year. You should return the product for fresher material.

Dr. Michael 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. For more information on REALITY and to receive a complimentary issue of his monthly update, REALITY Now, call (800) 544-4999 or visit www.realityesthetics.com.