Dual Cure Acrylics - Is It Time to Reduce Your Salt 'n Pepper Diet?

Denali Corporation - Jazzy DC Acrylic

The “salt and pepper” technique involves dipping a paint brush into monomer (methyl methacrylate) followed by dipping the brush into powder (PMMA) to form a bead of acrylic. It’s a very tedious and time-consuming process of making or adding to an acrylic appliance, not to mention flasking and processing for 8 hours.

Within the last few years, several light cure only acrylic versions have come on to the market. These products are particularly useful for appliances made outside of the mouth, such as pattern making. Some of these products, however, still require very long curing times in special curing ovens from 5 – 40 minutes! Denali Corporation’s entry to the group is HIRO, a pattern, indexing and registration material. It is light cured by dental wand type curing units in less than 20 seconds! It is dimensionaly stable, can be added to itself and allows continuous addition of material. As a pattern resin, HIRO burns out completely and can be used in making PFM copings, cast crowns as well as implant uses.

HIRO & Jazzy Pattern & Indexing Resin

Denali’s next product in this arena is Jazzy, a Dual Cure Acrylic. With Jazzy’s introduction, I am hard pressed to know why anyone would want a light cure only product. I am told that some find using a double barrel syringe to be too difficult, or simply want to take their time and light cure only when they like. O.K. But once you have tried Jazzy Dual Cure, you will be convinced of all its advantages and more. Jazzy can do several things in only a few minutes that digital printing can only dream about, such as techniques that are best done in the mouth! These include implant abutment registration, implant guides, and pick-up of implant sleeves. Think accuracy counts in implant dentistry?

Like all dual cure products, Jazzy comes in a double barrel syringe with auto-mixing tips. Jazzy bonds well to other acrylics and eliminates the odors of an open bottle of monomer or spills and waste clean-up of excess material. Jazzy sets in about one minute in the mouth and can also be cured on-demand.

As the name suggests we think it’s sophisticated, and innovative, and did I mention is has no heat build-up, therefore no pain, so we think its cool, too.

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Has Calcium Hydroxide Met Its Match from the New Bio-Adhesive Cavity Liners?

Dental practice has for decades utilized calcium hydroxide as a material for pulp capping and cavity lining. This use is based upon: the biological response of the pulp to isolate itself from calcium hydroxide, and that after initial cell necrosis, the pulp produces “reparative” dentin as a barrier between the pulp and the calcium hydroxide.

One of the statements about biological repair that I learned along the way was that “we” have a much better system of dealing with acidic challenges as opposed to basic challenges. Meaning our bodies can deal with acids much better than bases. Feel free to challenge me on this point, or add some factual detail. My primary assertion here is that the “healing” produced by calcium hydroxide may not be the best stimulus to result in an ideal, healthy situation. For example, continuous insult or injury from calcium hydroxide can result in de-vitalization of the tooth and end in complete calcification of the tooth. I hear you, some are already saying maybe that is not a bad thing.

No calcium hydroxide liner can really claim to be bio-compatible, it “works” by killing every cell in sight. Try putting any pH 14 material in a Petrie dish of cells and see what happens next. Thus the need for palliative basing materials such as zinc oxide -eugenol to as we say “quiet down” the pulp. Again, place a nano-scale amount of eugenol in a Petrie dish and see what happens, i.e. eugenol is one of the most toxic compounds known. As a tooth pain relieving treatment this dates back centuries. My premise: as much as I like eugenol, there must be a better way.

Another major disadvantage in use of the calcium hydroxide liners, or even calcium silicate (Portland Type III Cement), is that they have very little or no adhesion to dentin, and as a consequence often come loose when placing a composite material over them, let alone condense an amalgam on top of them, as we once did.

Within the last decade, dental material products now contain needed components to aide in tissue accommodation, such as in re-mineralization with amorphous calcium phosphate (ACP). These compounds have been used in some sealants and in some composites for quite a while. A few companies are now advertising them as “bio-active”.

There has been a new class of cavity liners that have been introduced that follow this approach, one of providing essential components for repair such as calcium, that are bio-compatible, and are also bio-adhesive. Bio-adhesive being defined as a material that is both bio-compatible and has biologically active adhesive components. These new cavity liners are also highly radio-opaque, with an aluminum equivalent of 3.5 mm, meeting the ISO 4049 standard to be classified as radio-opaque, using the more stringent endodontic requirement. This radio-opacity allows them to be easily observed in comparison to dentin and enamel.

Want more? In addition these new cavity liners are truly anti-bacterial, bacteria being a primary cause of sensitivity associated with secondary caries. These new cavity liners handle much better that the older calcium hydroxide liners or calcium silicates, and are esthetic compared to the grey calcium silicate liners.

So, I encourage you to take a look at this new group of cavity liners based upon the biological principles of bio-compatibility and bio-adhesion.

www.DenaliCorporation.com/SuperLiner.htm

 

"I'm Glad I Waited" - Cements Developed for Implants

Many years ago, the field of implantology took major steps towards the success that it is now enjoying. Around 10 years ago, after this success I considered developing a product for the cementation of implant crowns.

I am glad I waited! Today one of the biggest causes of implant failure is due to cement induced peri-implantitis.

There are many reasons why cements are now one of the biggest reasons for implant failure.

From a biological perspective, the tooth socket no longer has a periodontal ligament, a natural barrier that reduces excess cement accumulation.

From a placement perspective implants may not initially be as stable as a natural tooth with potential greater mobility and compression during crown seating, again allowing for excess cement to be extruded into the “sulcus”. Cement visualization may also be complicated by pink colored cements, making excess cement removal difficult.

From a practice perspective, reluctance exists by some to select a permanent cement, and choose to use a temporary cement while keeping the option open to remove the crown, if needed. Temporary cements by design are weak and often crumbly, making again excess cement removal more difficult in having to remove all of these little bits and pieces.

Finally, nearly ALL implant cements are NOT radio-opaque, making their diagnostic observation impossible. I know that some readers may believe their cement is radio-opaque because it says so on the package, I also did at one time. For this proof, I cite  “Radiographic Appearance of Commonly Used Cements in Implant Dentistry”, Pette, G.A., Ganeles, J., and Norkin, F.J., Intl J Periodontics Restorative Dentistry, 2013, Jan-Feb 33(1):61-8., a publication which evaluates this claim. The authors concluded that these cements “are not radiographically detectable at an appropriate sample thickness”.

How would you know if your cement is radio-opaque if you can’t see it? After observing tissue inflammation is not the time to learn that your cement is not radio-opaque. This paper and the development of a new generation of implant cements are based on a 350% level of radio-opacity, not at the < 100% aluminum equivalent that are cited in this paper.

And if this is not enough, in a healing and already compromised environment, almost all implant cements are not anti-bacterial, allowing weak, crumbly, porous excess cement to be a site for bacterial growth.

All of these conditions can lead to inflammation, tissue breakdown, and cement induced peri-implantitis.

So, in 10 years, we have learned a lot as to what an implant cement should provide.

Still wondering about the importance of cement induced peri-implantitis, just look at the websites of some of the leading implant companies to see their cases of peri-implantitis, a problem which I can assure you they want to go away. This is a topic of another blog, someday.

To solve these problems, a current generation of true implant cements has emerged. These products are long-term cements, not weak, soluble, crumbly temporary cements; they are strong, but retrievable; they are enamel or dentin colored; they should be at least 350% aluminum equivalent radio-opaque; and they are anti-bacterial.

I encourage both new practitioners and experienced implantologists to learn more about these cements and avoid the all too common problem of trying to retrieve excess cement that they can not see, until its too late.

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One such product that solves this problem is Harmony Implant Cement.

To learn about its qualities and benefits, please visit www.DenaliCorporation.com.

The Issue: Self-Adhesives vs. Glass Ionomers

The Issue: Self-Adhesives vs. Glass Ionomers

Procedure: Proper Case Selection and Understanding Product Attributes

The Conclusion: Self-Adhesives Alone Should Not Be Compared to Glass Ionomers

In using a product that is labeled as a self-adhesive the manufacturer generally is conveying that it contains acidic monomers that provide enhanced adhesion to tooth or restorative material compared to traditional composites based on BIS-GMA or urethane dimethacrylate alone. The following comparisons are therefore often incorrectly made.

Glass ionomers vs. Self- adhesive Cements – Wrong.

Bonding agents and Traditional composites vs. Self Adhesives – Wrong.

Self- adhesives vs. traditional composites without bonding agents– Correct.

Having initiated the self-adhesive resin group nearly 15 years ago, I have seen all of these incorrect comparisons made over the years, and still prominently done so. The goal of self-adhesives, not to be confused with self-etching, was to provide a more adhesive, filled, composite-like material for practitioners. Some have identified them as composites that contain bonding agents. I am O.K. with this. Self-adhesive chemistry has been applied in sealants, cements, flowable composites, and core materials to name a few applications. The goal was to provide a material that would provide some adhesion, but were never intended, at least on my part, to replace bonding agents. Self-adhesives are not low enough in pH to provide self-etching to the extent needed to be called self-etching like self-etching bonding agents. 

Many highly respected clinicians continue to this day to make this mistake by comparing glass ionomers vs. self adhesive resin cements with respect to achieving maximum tooth adhesion and let’s say crown retention. In this case, the correct comparison if someone is trying to achieve maximum bonding to dentin is to use a bonding agent and a self-adhesive material together and compare that to a glass ionomer.

I can guess why some would want to minimize the self-adhesives, if they desire to promote bonding agents, which may have taken some the market away from them, or glass ionomers, as self-adhesives have also achieved many loyal followers. It is not a coincidence that so many companies offer a self adhesive cement, many of these same companies also sell bonding agents, and even a few of them recommend using their bonding agent with their self adhesive cement. Glass ionomer companies?, not so many, remember sensitivity? That is why self-adhesives hold a valuable place in dentistry. Every practitioner in cementing a crown should recognize when the situation that calls for maximum retention, for example a badly broken down tooth with little remaining walls to bond to. This is a case where crowns coming off or a de-bonding failure is not un-expected. This situation while not being the best outcome is lending support to the implant alternative. Choosing not to use the best material or materials is a mistake. 

Are those of you reading along, actually debating whether dentin bonding agents are the material of choice or at least an equal to glass ionomers in dentin bonding? There is no claim that I am aware that states self-adhesives outperform bonding agents with respect to retention. Why then leap to eliminating bonding agents in comparing self-adhesives alone vs. glass ionomers? I would suggest that this is not a good choice as a clinician to make. If in doubt, always use a bonding agent! In promoting self-adhesives I have never tried to talk anyone out of using their bonding agent. To the contrary, from my testing the best bonding pair is a bonding agent with a self adhesive, this also follows the well-known chemistry adage, that “like likes like”, meaning a bonding agent is more similar, in hydrophilic behavior, to a self adhesive than a traditional composite. This was the whole concept in using monomers that are more hydrophilic compared to BIS-GMA or urethane dimethacrylate in creating the self-adhesives.

Each group of materials has there own drawbacks. Bonding agents when left at the margin are a primary source of leakage. Glass ionomers, being made up of some percentage of water are more soluble than composites, and to be fair, self-adhesives by themselves do not provide the maximum tooth retention. So, where does this leave us? Not all cases require the use of bonding agents, and not every case would be compromised by using a material does not provide the maximum retention, such as glass ionomers. The self-adhesives offer a convenient solution by providing fewer steps, less equipment, and rarely sensitivity when the case is not complicated or compromised. Self-adhesives perform very well when compared to glass ionomers, provided they are not asked to perform more than they were designed or intended to do. So lets not continue to compare apples to oranges (glass ionomers to self adhesive cements or other applications), they are different, unless you are going to bring in the use of bonding agents.

BPA and the FDA

This past month the US Food and Drug Administration (FDA) quietly made a significant decision that effects the dental industry in far reaching ways. The FDA declined to call for further investigation into whether Bis Phenol A (BPA) can cause potential health risk to those that are exposed to it. BPA has been commonly used in a variety of applications, including as a liner for cans that contain food, drugs, or infant formula. The FDA concluded that after more than 40 years of use, without any specific correlation to any known health risk, that BPA did not warrant further investigation at this time.

For several years, some in the dental industry have created for their own benefit, concern whether BPA could cause a health risk. See some of my earlier blogs on BPA.  Note that these same companies are not conducting any research to further understand the issue, only issue warnings, create fear, and make sales. This is done at the same time they knowingly sell other products that contain BPA.

BPA is not a formula ingredient in dental products, however it can be a by-product in the synthesis of BIS-GMA, one of our most common monomers used in many different composites, cements and sealants. In this capacity BPA is often not present at all, or found only in very small quantities, this is unlike the percentages that can be measured in food stored in cans lined with BPA. I hope that this significant decision by the FDA will at least silence those that have created this fear, and possibly get them to change their position on this issue.....(wink).

Dental Material Placement - Intra Oral Observations

Recent trends in dentistry utilizing magnification and improved intra-oral lighting are leading the way to better dentistry. When this trend started, it was common to hear how much better the tooth and soft tissue condition could be observed, as well as how much more in control clinicians felt. This led to micro dentistry and minimally invasive techniques aimed at reducing the amount of healthy tooth structure removed. These techniques have also been applied to pathological conditions improving early diagnosis of potentially harmful tissue lesions.

In the area of dental materials, more accurate placement of materials, using finer brushes, better selection of applicator tips, and careful removal of material flash before curing polymerizable materials has occurred. This focus should improve margins and provide improved gingival health. As part of the greater accuracy achieved in material placement, we should also see a reduction in placement of materials where they do not belong.

A research report to be presented at this years IADR Meeting in San Diego (1), I think emphasizes in clear results the impact of what should be accepted as good placement technique. This study looked at the placement of different material combinations, such as bonding agents with composites, and evaluated their combined contribution to leakage of a restoration. The study demonstrates the need for more careful placement of dental materials clinically for their intended purpose and location.

Common dental materials such as bonding agents, composites, glass ionomers, and self adhesive composites have very different responses to water uptake and leakage. Material responses mimic what has already been shown for products that contain solvents and/or water (now include glass ionomers or resin modified glass ionomers in this group). Fluid transport through the material can occur more rapidly due to this general compositional aspect. This is in contrast to some self adhesive materials (primarily those that are resin based - ie no glass ionomer or solvent within them, including water). A few examples from this study are shown below.

I encourage those of you using loupes in your practice to further document these observations clinically and to utilize careful material placement whenever possible. The take home message from this study is that dentin bonding agents do not belong on exposed enamel margins.

Figure 1.

Bonding agent with composite restoration showing massive leakage around the edge of the composite/bonding agent interface. Note the interior of composite itself is non-stained (white), this is can be viewed as the center top surface.

Figure 2

Glass ionomer with bonding agent. Note in this example the entire treatment area has turned blue, as opposed to Figure 1, in which leakage has occurred around the edges of the composite/bonding agent interface. In this example, leakage has occurred at the glass ionomer/tooth interface AND through the glass ionomer material itself.

Figure 3.
Self adhesive material, AURA Veneer, showing no leakage at the treatment area. The veneer cement treatment area is the white circular area at the bottom center surface. Note: some leakage occurring around the edge of the tooth - non treatment area. Also note that no bonding agent was used.

Please see the IADR presentation, the Abstract in the Journal of Dental Research, or contact me for further details of their study.

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1. "Contribution of different materials to the leakage of restorations", J.O. Stannard, I. F. Stannard, and S. R. Stannard, J. Dent. Res., Special Issue, 89th Annual Meeting, San Diego, CA (March, 2011).

Dental Materials - Evidence Based?

I recently attended a dinner party with a group of dental friends. It was an unusual gathering because among the guests there were a number very successful scientists, engineers and mathematicians. As the evening warmed up we engaged in a conversation about the history of science and business. An older, "highly accomplished" scientist described a feeling that science and engineering in the United States was not progressing as it once did. He felt many of the large corporations were now managed by individuals that did not possess the scientific knowledge about how their own products worked. He said this was unlike the "Golden Years", when companies were managed by product inventors, and management decisions were based upon product performance rather than profits, dividends, or consolidations. Sound familiar?

This got me to thinking about dentistry. Is there a difference between large industrial corporations today and business in the dental field? This is certainly not true in the dental office! Many friends have told me how happy they are not to be in the same situation as some physicians, managed by HMO's or hospital administrators. The independence of dental professionals in the US is a tradition. In corporate dental manufacturing, however I don't think this is true. Within recent years, I have observed that several of the major dental companies no longer employ people that are clinically trained to evaluate their products.

A by-product of this is that long-term clinical studies have nearly disappeared from the dental research community. By this I mean, two year, three year or five year studies on product evaluation. These studies used to be common among the IADR or AADR research presentations. No more! We are told they are too expensive and take too long. Rapid product changes are a consequence of this as well. Consider that the actual product may not be on the market, or even recognizable, when the study results are published. I have heard this lament from other researchers. Dental materials research, once was a hallmark for the concept of evidence-based dentistry. Today I am not so sure this exists anymore. How can we deal with this situation?

What are the consequences of this? I guess on the surface there is mis-leading product information and sometimes product introductions occur without sufficient product testing. The larger impact of this is its effect upon patient care and the reputation of OUR profession. In response to this problem I also observe that many companies are now taking a very limited focus on just their own product and do not engage in the larger aspects of its use in dentistry. These companies are avoiding the bigger picture as to systemic effects or even accompanying product recommendations. Why would they?

So next time you hear of a "new" product or instrument, or become aware of something new to you, I hope you will ask the speaker how the product has been evaluated, how long, and what were the results? In other words, ask about its history. This may sound like having to be a researcher, but those Golden Years for us also appear to be gone.