Predictable and Unbreakable Bonds are Fundamental

If you thumb through a typical dental supply catalogue, you might find 30 different adhesive systems or bonding agents. Every material manufacturer has an offering. Direct sale manufacturers also add to the marketplace.

So the million-dollar question is, “What adhesive should I use?” A lot has happened during the past 4 decades in dental bonding. In the 1980s, doctors were exposed to the early market entries. These were typically fourth-generation, 3-component systems used to adhesively bond composite restorations as an alternative to the staple material at the time, amalgam.

Fast forwarding, there has been an explosion in adhesive material science and restorative materials. Now doctors not only bond direct restorations to teeth but they also employ a much broader range of indications across pediatric, adult, and geriatric dentistry. The restorative options range from a variety of composite resins—including viscosity variations, layered options, bulk-fill options, dual-cure materials, bioactive materials, desensitizers, and fiber and core buildup materials—to the expanded use of adhesive cementation of indirect restorations made for the continually evolving modern ceramics and related offshoots. In short, doctors rely more than ever on predictable, reliable, and lasting bonds between tooth and restoration.

The Review

The evaluators at Catapult Education clinically reviewed and tested the Peak Universal Bond adhesive system from Ultradent Products Inc. A smaller subset of evaluators also performed unbiased laboratory comparison testing among several market-leading competitive products.

Figure 1

The Peak system includes Peak Universal as its flagship bonding agent; Peak SE, a self-etching primer; and Ultra-Etch, a 35% phosphoric acid gel etchant (Figures 1-2). This lineup of components allows a doctor to use the Peak system via fifth- or sixth- generation protocols as well as in a hybrid “selective etch” mode.

Figure 2

The Peak system includes Peak Universal as its flagship bonding agent; Peak SE, a self-etching primer; and Ultra-Etch, a 35% phosphoric acid gel etchant (Figures 1-2). This lineup of components allows a doctor to use the Peak system via fifth- or sixth- generation protocols as well as in a hybrid “selective etch” mode.

Figure 3

When enamel is the primary substrate to be bonded (eg, bonding of veneers or shallow, primarily enamel-based preparations such as small class Is, IIIs, or sealants) Ultra-Etch is used for 20 to 30 seconds depending on the clinical presentation of the enamel. (Figure 3)

Figure 4

It is then washed away, and followed with a 10-second brush-on scrub of Peak Universal adhesive to infuse the chemistry into the tooth’s microanatomy (Figure 4).

Figure 5

The adhesive is then air-thinned with progressively increasing air pressure until it presents like a stretched film of cellophane (Figure 5).

Figure 6

The adhesive is light cured appropriately pending curing light intensity and target distance. In short, conventional evidence suggests that the best etch patterns leading to optimal adhesion on enamel can only be attained by using phosphoric acid.

When dentin is the primary substrate to be bonded (eg, large core buildups or monoblock fiber post and core reconstructions and full crowns), Peak SE is scrubbed onto the dentin surface for 20 seconds, evaporated with a few seconds of air stream, and then followed by the same steps as the application of the Peak Universal adhesive (Figure 6).

Figure 7

In short, conventional evidence suggests that the most predictable and highest bond strengths are achieved on dentin through self-etching primer technology. This approach also tends to best mitigate postoperative sensitivity.

Finally, when a prominence of both enamel and dentin are present in a clinical preparation (eg, typical class Is, IIs, Vs, and indirect inlays or onlays), the strategies above are combined. This technique is referred to as selective etching and involves carefully placing phosphoric acid across the enamel borders of a preparation (Figure 7).

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The viscosity and placement precision of Ultra Etch led an evaluator to deem it the “gold standard of etchants.” Once the phosphoric acid is rinsed away, the doctor proceeds with the steps above for delivery of Peak SE to all involved dentin with no concern for overlap onto enamel. The subsequent steps are the same for application of the adhesive. In summary, selective etch approach is used to customize and optimize bonds in most typical clinical scenarios involving both dentin and enamel.

As Catapult Education doctors began to present their findings and feedback on Peak, it quickly became evident how satisfied they were with the outcomes. From general praise on the delivery syringe mechanism (bottle + micro-brush delivery is also available), to notes on restorative outcomes, and finally, confidence in bond performance with regards to the commitment Ultradent Dental Products has as a manufacturer to research and development. This notion of unbiased research proved very important.

Every doctor has seen shear bond strength studies provided by manufacturers in lectures, print, social media, and meeting booths. How can every bonding agent be the best? Every company tries to develop and deliver the best product they possibly can. That said, there is undoubtedly a hierarchy. This is where the smaller subset of evaluators was truly able to investigate the shear bond strength performance of Peak Universal.

We were provided a platform to bring what we deemed our personal preferences in bonding agents. We then prepared and bonded composite test buttons on uniformly prepared dentin sample blocks with no manufacturer involvement. The doctors simply followed manufacturer instructions for each material and compared the outcomes. Without naming the competitors tested (essentially all the major players were in the mix), the outcomes can be generalized as follows. Most products performed in a way that I, as the writer, would rate as “good.” This means their shear bond strength (SBS) values were 25 to 35 MPa. Unfortunately, a few of the products tested did not reach that range, and I would rate them as “inadequate.” However, 2 of the products tested yielded results that were a standard deviation higher than those in the “good” category. These 2 products, which yielded average SBS values approaching 50 MPa included Peak Universal, which had the highest SBS values. In fact, several samples recorded forces of more than 60 MPa being required to shear off the composite buttons.

With this background, when a doctor asks, “What adhesive should I use?” my answer really comes down to posing the question, “How strong do you want your bond to be?” As doctors, we must decide if we want to merely restore teeth above a minimum threshold of strength or to approach as high a value as possible. To make an informed decision, it might help to consider this question. What is the cohesive strength of dentin? Logic says if we are restoring a broken-down tooth, it would be nice to get it back to its original level of integrity. After all, we always say, “Nothing’s as good as virgin tooth structure.” Interestingly, the cohesive strength of dentin, meaning the force needed to break a chunk of dentin away from itself, ranges from 70 to 100 MPa.1 Does this knowledge suddenly reframe how we look at tooth reconstruction? Why wouldn’t we want to rebuild teeth to a level rivaling original strength and integrity?

With the Peak Universal Bond adhesive system, Ultradent has developed a flagship product. This was the reason why so many of our Catapult evaluators gave glowing reviews. Several doctors who were not already using Peak in their practice began doing so when they saw the outcomes. Ultimately, Peak earned a resounding Catapult Vote of Confidence.

Reference

1. Jessop N, Denehy GE, Vargas MA. Dentin shear strength: effect of depth and location. Presented at: IADR/AADR/CADR; 1999; Vancouver, BC. Abstract 342.