Apex Dental Materials

Apex Dental Materials

Another problem with the newer systems is that combining primer and adhesive or primer and etch results in primer being applied to enamel. Surpass (Apex Dental Materials) and All-Bond SE (Bisco) are the only newer-generation products Dr. Brucia has found that have no solvent in the adhesive. "I absolutely would never want primer on enamel," he said. "Dentin primer does nothing but get in your way."

The solvent in the primer doesn't allow adhesives to cure. With fourth-generation products, in which the primer, etch, and adhesive are separate, you can remove the solvent by air thinning the primer until the movement of fluid stops. "When you mix primer and adhesive together, no matter how good your technique is, 25% of what you have left is solvent," Dr. Brucia said.

Light also helps remove the solvent, he noted. "If you light assist the evaporation of your primer, your bond strength will routinely go up 20%. I have tested this for years. The added amount of time and heat will give you a much better adhesion," he said.

A problem with sixth-generation products (in which the primer and etch are in one bottle, the adhesive in another) is that the acids aren't as effective for etching, Dr. Brucia said. Five-amino salicylic acid, citric acid, and nitric acid are used because they neutralize themselves in the mouth, eliminating the need for rinsing.

But phosphoric acid is better for etching, Dr. Brucia said. "I use phosphoric acid on everything. If you were to take my phosphoric acid away from me, you might lose a finger."

The differences add up starkly in bench tests, he said. With his fourth-generation OptiBond, PermaQuik, Scotchbond and All-Bond, he can instantly achieve 40 megapascals (MPa) of bond strength, and 72 MPa after 24 hours. By contrast, with the newest products, he can only achieve 10-15 MPa.

As further evidence that fourth-generation products last longer, Dr. Brucia cited an article in Dental Materials (July 2000, Vol. 16:4, pp. 285-291) that found that the "three-step resin adhesive and the RMGIC [resin-modified glass ionomer cement) showed clinically acceptable retention rates, while a high failure rate was registered for the one-bottle adhesive."

"I would still rather have a 12-year-old bonding agent and a 20-year-old composite in my inventory than the newer systems today," Dr. Brucia concluded.

Not everyone agrees that bonding strength has declined with the newer systems. Junichi Ohtsuki, product manager for Kuraray America, acknowledged that seventh-generation adhesives "are not perfect yet." But he insisted that "The sixth generation is the best bonding agent for relieving sensitivity." The fourth generation, he said, "is similar in strength, but it's technique-sensitive."

Asked for evidence to back up his claims, Ohtsuki provided DrBicuspid.com with three articles from peer-reviewed journals. Of theses, one dealt only with the consequence of mistakes in technique. The other two actually supported Dr. Brucia's position. For example, a September 2005 review by Peumans et al in Dental Materials concluded that, compared to fourth generation systems, "The clinical effectiveness of two-step etch-and-rinse adhesives was less favorable, while an inefficient clinical performance was noted for the one-step self-etch adhesives" (September 2005, Vol. 21:9, pp. 864-881).

Ohtsuki also provided a symposium paper speculating on hypothetical advantages of "self-etch" (later than fourth-generation) adhesives. Finally, he supplied two articles from Gordon Christensen's CRA Newsletter, but only one (November/December 2003, Vol. 27:11/12, pp. 1-5) reported tests of a fourth-generation product: All-Bond 2 (Bisco). The anonymous authors gave this product a bond strength of 26.5 ± 6.3 MPa on enamel and 36.1 ± 4.9 MPa on dentin.

These researchers found several other recent-generation products stronger. They rated two fifth-generation products the highest in strength. Prime & Bond NT (Caulk/Dentsply) got the highest enamel bond strength rating (46.3 ± 9.8 MPa), while OptiBond Solo Plus SEP got the highest dentin bond strength rating (59.5 ± 6.9 MPa).

On the other hand, Douglas J. Brown, D.D.S., senior manager for clinical affairs at Bisco, acknowledged that the fourth-generation systems have clear advantages. "The evidence has shown that they are stronger and longer-lasting than the self-etches," he said.

The only advantages to the newest products -- particularly the one-step systems -- are speed and convenience. In some instances, such as placing a restoration in an impatient child, that speed might be worth the loss of durability, Dr. Brown argued.

And even Dr. Brucia acknowledged that in situations in which strength is not at a premium, the newest systems might be useful. Overall, though, he warned that many dentists would pay the price for taking the easy route.

"I'm too busy to have sensitivity," he said. "I'm too busy to have failures."

Old-style adhesives are better, researcher says

Old-style adhesives are better, researcher says

Violins, cathedrals, waffle irons: they don't make 'em like they used to. To that list, Jeff Brucia, D.D.S., co-director of the Foundation for Advanced Continuing Education (FACE), would add dental adhesives.

"Apply the technique of the 1970s," Dr. Brucia told an audience of 400 at the recent ADA annual meeting. "It's not the coolest. It just works."

One goal of the seminar, titled "Restorative Materials Update 2008," was to review "new advancements" in restorative dentistry. But according to Dr. Brucia, there have been precious few advancements for the past few decades -- especially in bonding systems.

"There has not been an improvement," he said. "There has been a different mode of application." In fact, many products and techniques being used today are not as good as those Dr. Brucia's father used, he said. "He never had sensitivity. Why weren't his restorations falling off? Why are ours falling off today?"

Three adhesive makers contacted by DrBicuspid.com -- Ultradent, Bisco, and Kuraray America -- offered varied reactions to Dr. Brucia's observations: a Kuraray spokesperson disagreed, an Ultradent spokesperson declined to comment, and a Bisco spokesperson mostly agreed.

The problem with mixing

Dr. Brucia, who inherited his father's San Francisco practice and is a University of the Pacific assistant professor, has also been paid to lecture to some adhesive companies. But he said he's beholden to none -- and often contradicts them. "The companies don't like me," he said.

One reason is that he insists the art of bonding reached its zenith with what is now called the fourth generation. This system requires three bottles: an etch, a primer, and an adhesive.

The etch is phosphoric acid. The primer is a hydrophilic agent designed to bind well with dentin. The adhesive is a hydrophobic agent that binds well with porcelain and composite.

Examples include All-Bond 2 and 3 (Bisco), Bond-It (Pentron), OptiBond FL (Kerr), Syntac (Vivadent), Scotchbond Multi-Purpose Plus (3M), and PermaQuik (Ultradent). "They work," said Dr. Brucia. "They work. They work really, really, really well."

Subsequent systems have not shown the same bond strength, Dr. Brucia said, citing both his own lab tests and published studies.

Fifth-generation adhesive systems attempt to save a step by combining primer and adhesives in the same bottle. "How do you take something that loves water and put it together with something that hates water?" Dr. Brucia asked. "You make the product very acidic."

He compared the notion to combining shampoo and conditioner in one. Sure, it's more convenient, he said, but it doesn't work as well. "Give me a fifth-generation system and I have to concentrate like no tomorrow to make that stuff work well," he said. "If I make a mistake with this product, I get catastrophic results."

One problem, he said, is that this acidic hydrophilic bonding agent can cause an acid-base reaction when it comes in contact with a dual- or self-cured composite. Unless the composite is cured within two minutes of placement, this reaction can prevent it from ever curing. Another problem is that the acidic hydrophilic bonding agent creates osmotic blistering.

As evidence, Dr. Brucia cited research by Indiana University researchers (Operative Dentistry, May-June 2006, Vol. 31:3, pp. 346-353) that found that later-generation bonding systems were more water permeable.

To cope with these problems, various adhesive companies introduced new materials to add to the restorations in the late 1990s, Dr. Brucia said, but none worked. Later innovations haven't helped much either, he added. "If you go down to the exhibit floor, they'll tell you, 'We've fixed it.' Well, why did [they] break it in the first place?"

More recently, adhesive companies began raising the pH in their products. "I shook my head," said Dr. Brucia. "I said, 'Wait. We needed the acidity to keep the hydrophilic and the hydrophobic products together." And sure enough, research showed that the new products weren't very stable.

Lack of stability particularly plagues the seventh-generation systems, in which etch, primer, and adhesive are all combined in a single bottle, he said, citing a study in the American Journal of Dentistry (April 2006, Vol. 19:2; pp. 111-114).

The single-bottle products are so unstable that they have to be kept chilled. "When we're doing a study, we call up the company and ask if we can get some of the product," Dr. Brucia said. "It arrives packed in ice." But adhesives makers often neglect to inform their customers of this problem. "When is the last time you bought a bonding agent and it came packed in ice?"

Study links herpesvirus with endodontic disease

Study links herpesvirus with endodontic disease

Herpesviruses have long been considered the culprits behind many oral diseases. Now a new study has found a link between endodontic disease and the Epstein-Barr virus. The discovery could lead to the development of new preventive and therapeutic treatments for some endodontic diseases.

Epstein-Barr is a form of herpesvirus and a pathogen found in more than 90% of the world's population. It is associated with many diseases, including infectious mononucleosis, malignant lymphomas, and nasopharyngeal carcinoma.

The new study has found that a large number of dental patients with the inflammatory diseases irreversible pulpitis and apical periodontitis also have the Epstein-Barr virus (Journal of Endodontics, December 2008, Vol. 34:12).

Researchers at the Oregon Health & Science University School of Dentistry wrote that their aim was to ascertain the presence of human cytomegalovirus (HCMV), Epstein-Barr virus (EBV), herpes simplex virus 1 (HSV-1), and varicella zoster virus (VZV) in endodontic pathoses. All four forms belong to three different groups of herpesvirus.

The team looked at specimens collected from 19 healthy pulp control patients and 82 patients exhibiting endodontic disease, including those with irreversible pulpitis or apical periodontitis, as well previously treated apical periodontitis. The patients' ages ranged from 15 to 92, with 50 males and 51 females. Specimens were obtained from molars, bicuspids, and anterior teeth.

Researchers studied the DNA and RNA from the specimens to determine the presence of herpesviruses.

EBV DNA was present in patients with endodontic disease in higher percentages (43.9%) compared to the control group (0%), as was EBV RNA (25.6% compared to 0%).

HCMV DNA and RNA were found in high percentages in both endodontic patients (15.9% and 29.3%, respectively) and in healthy controls (42.1% and 10.5%, respectively).

HSV-1 DNA was found in a slightly higher percentage of endodontic patients (13.4%) when compared to healthy controls (5.3%), but these differences were not statistically significant, according to the researchers. No HSV-1 RNA was found in any of the diseased or healthy pulp specimens. Only one patient, exhibiting symptomatic irreversible pulpitis, showed presence of VZV DNA and RNA.

"Our results have indicated that EBV is present in significantly higher frequencies in irreversible pulpitis and apical periodontitis when compared with healthy controls," the authors wrote. "This study supports the premise that EBV, but not HCMV, HSV-1, or VZV, is associated with irreversible pulpitis and apical periodontitis, and may potentially play a role in endodontic disease."

"There have been few prior publications on herpesviruses and endodontic disease -- only one other to my knowledge," said co-author Curtis Machida, Ph.D., a professor in the department of integrative biosciences at the Oregon Health & Science University, in an interview with DrBicuspid.com. "This current study is the first published report linking Epstein-Barr virus and irreversible pulpitis, one prominent form of endodontic disease."

Although the study has statistically significant evidence to prove that the presence of EBV is associated with endodontic pathoses, the fact that it is not found in all endodontic patients allows the interpretation that other microorganisms may serve as co-factors of disease, the researchers noted.

"EBV may represent one important player of irreversible pulpitis, but there are undoubtedly additional co-factors for disease," Machida said. "Endodontic disease is believed to be due to a polymicrobial infection and inflammatory disease. Knowing the full cast of players would obviously and ultimately lead to better and more targeted modes of therapy."

Machida added that the study has been of great interest to academics and professionals within the endodontic field.

Dennis Walling, M.D., an associate professor in the department of microbiology and immunology at the University of Texas Medical Branch, agreed that this is the first study to identify EBV specifically as the herpesvirus associated with endodontic disease. While previous research has linked herpesviruses with endodontic disease, this study extends and strengthens the association with the large number of histologically varied specimens that were studied, he noted.

"The potential significance of finding herpesviruses in periodontal and endodontal diseases is that it forces us to rethink long-held assumptions about the pathogenesis of these diseases originally believed to involve only bacteria," Dr. Walling said. "The interesting idea is that the viruses may act in a way that facilitates bacterial pathogenic potential, perhaps by compromising the local oral defense mechanisms in a way that shifts the host-microbe equilibrium in favor of the resident oral bacteria."

More research is needed to understand the mechanisms, which could lead to the eventual development of new preventive or therapeutic approaches to these diseases.

"However, this area of study still has far too many unanswered questions for anyone to yet know how this finding might be clinically useful," Dr. Walling concluded.

University of Buffalo dental school dean steps down

University of Buffalo dental school dean steps down

The dean of the University of Buffalo School of Dental Medicine is stepping down after serving in his position for seven years, according to a UB Reporter news story.

Richard Buchanan, D.M.D., has previously served in academic and administrative positions at the University of Texas Health Science Center Dental School at San Antonio, New Jersey Dental School, and Baylor College of Dentistry.

"A strong academician in his own right, he has provided the school an important compass in the form of leadership by personal example," said David Dunn, vice president for health sciences, in the news article. "Fortunately, he has agreed to remain in his current position until a national search can be launched and a suitable successor identified and recruited."

 Dentsply International has entered into a definitive agreement with the shareholders of Zhermack of Badia Polesine, Italy, to acquire a majority interest (60%) in the European firm, according to the company. Terms of the deal were not disclosed.

As part of the agreement, the two founders of Zhermack will retain "significant ownership" and continue to manage the business.

Zhermack is a producer of dental impression materials and lab equipment and sells products in more than 100 countries, with an emphasis on Europe, Latin America, Asia, and the Commonwealth of Independent States. The company has manufacturing facilities in Italy and Poland.

"We believe that our polymer-based expertise can contribute to Dentsply's R&D efforts, and as partners, we can continue developing innovative products for the dental profession," said Tiziano Busin, Zhermack's president and founder, in a press release.