October 2, 2008 | Web Exclusive
Dental adhesives: Always room for improvementDr. Harald Heymann outlines the advantages and disadvantages of total-etch and self-etch adhesive systems in the October issue of DPR. Here he takes a look at the latest improvements in adhesive systems, and why self-etch systems offer reduced sensitivity. By Renee Knight
We’ve seen significant improvements in total-etch and self-etch adhesives in recent years. Some manufacturers have even re-introduced time-proven total-etch materials such as the OptiBond FL (Kerr) and All Bond 2 (Bisco). Historically, these systems have afforded some of the best clinical performance. We conducted a 12-year recall at UNC under the direction of Dr. Al Wilder with OptiBond FL and found an 89% retention rate. Most self-etch systems would do well to afford such rates at three years. Based on that, Kerr re-introduced the material with improvements, including incorporating a radiopaquing agent. The old All-Bond 2 has also been improved and re-introduced as All-Bond 3. It, too, has inherent radiopacity through incorporating radiopaque nano particles.
| Don’t be so sensitive
One of the biggest advantages of using self etching systems is reduced sensitivity. Tooth sensitivity is a result of fluid movement within the dentinal tubules stimulating barometric receptors at the base of the dentinal tubules. In a classic study by Dr. David Pashley, the smear layer itself has been shown to reduce dentin permeability and fluid flow by 86%.4
With traditional phosphoric acid etching, these smear plugs are totally removed, dentinal tubules are opened up and ultimately, they must be sealed properly with primer to ensure that no post-op sensitivity occurs. Self-etching primers do not face this issue to the same degree because they employ less aggressive acids that do not usually remove the smear plugs as aggressively, resulting in excellent tubular sealing. Unlike conventional total etch techniques employing phosphoric acid conditioners that open the tubules, if incomplete coverage of all cavity surfaces occurs when applying self etching primers, no increase in sensitivity results because the smear plugs remain intact.
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We’ve probably seen most of the recent improvements in the self-etch realm. To address excessive hydrophilicity and durability concerns, manufacturers have introduced materials that feature a hydrophobic component. 3M ESPE introduced Adper Scotchbond SE that includes a hydrophobic overcoat in the second bottle. This material is essentially a self-etch version of the old multi-bottle material, Scotchbond MP. It incorporates an adhesive with a hydrophobic layer to improve bond durability.
Surpass (Apex Dental Co.) also shows considerable promise. Like the old “gold standard” multi-bottle systems, it includes a separate (non-rinse) etchant, hydrophilic primer and hydrophobic adhesive. It is anticipated that these “hybrid” self-etch versions of the traditional multi-bottle total-etch materials may overcome the concerns that have been present with the more hydrophilic self-etch systems that have largely been present in the marketplace to date.
Why radiopaque?
In the past, most adhesives were not radiopaque. If they were placed in too thick of a layer under the composite restoration, they often looked like recurrent caries on a radiograph. This was because of their lack of radiopacity. That’s a confounding variable when you’re determining if there’s decay or not. Radiopaque fillers now used in many new adhesives show up clearly on x-rays, making it easier for dentists to differentiate them from recurrent caries. That’s a big improvement.
Don’t give in to the hype
It’s extremely difficult to keep up with all the systems in the market today. There is often a lot of hype when new products are introduced, but I urge you all to be discriminating dental consumers. Don’t be so quick to buy the “latest and greatest” product on the market. Often times materials are introduced without significant clinical trials, and that can lead to unexpected failures. Speaker testimonials are also not fool proof by any means. Their crystal ball is no better than yours.
It is also important to keep in mind that in vitro bond strength numbers are among the most misleading pieces of information used to advertise dental adhesives. In vitro bond strengths mean little when it comes to predicting clinical performance. There are too many variables in dentin bond strength testing, making it difficult for them to accurately predict clinical performance.
For example, bond strengths are directly related to the depth dentin has been prepared. The deeper you go into dentin, the more tubules you encounter and the less intertubular dentin is present. The deeper you prepare a tooth, the lower the bond strength becomes. This means if a study uses teeth that were deeply prepared, versus a study where the teeth were not deeply prepared, the bond strengths for the two studied would be different simply based on the dentin depth.
Standing the test of time
To ensure you give your patients the best possible care, it is always safest to use time-proven materials that have a track record. The old adage of “oldies but goodies” most certainly applies in the realm of dental adhesives. There are some very promising innovations, but my recommendation is to wait a few years until these materials have been validated clinically as opposed to trying something that’s largely unproven.
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Sidebars: Common Mistakes and Typles of Bonding Systems
References
1. Perdigão J et al. Total etch vs. self etch: Effects on post-operative sensitivity. J Amer Dent Assoc 2003; 34:1621-1629.
2. Perdigão J et al. The effect of adhesive and flowable composite on post-operative sensitivity: two week results. Quint Inter 35:777-784
3.Schupbach P et al. Closing of dential tubules by Gluma desensitizer. Eur J Oral Sc 1997; 105:414-421.
4. Pashley DH et al. Regional resistances to fluid flow in human dentin in vitro. Archs Oral Biol 1978; 23:807
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