Fusion Plus, Total-etch adhesive
To condition the preparation, enamel and dentin are etched with phosphoric acid first. As a second step, a one-bottle adhesive is applied. While this has been a simplification of the application procedure, one had to realize soon that total-etch adhesives required an optimal application technique and rigorous moisture control for clinical success. This is illustrated by the often discussed question: “How wet is wet?” The complete removal of the smear layer also increased the risk of postoperative sensitivities with this group of adhesives. Nevertheless, the development of monomers specifically designed for dental adhesives started with the total-etch adhesives. Such adhesion promoting monomers typically contain polyacrylic acid, phosphoric acid or phosphonic acid groups functionalized with one or more polymerizable methacrylate groups.
One might expect that some of the older systems would disappear with the progress from multi-component to all-in-one self-etching adhesives. However, the sales numbers of these four general types of adhesives immediately show that the multi-component systems did not disappear. While the two-component self-etching and the all-in-one adhesives exhibited the largest market growth since 2003, one-bottle total-etch adhesives still found increased use.
The Technology of Fusion Plus, Total-Etch Bonding Adhesive Hydrolytically stable monomers from Phosphate groups exhibit a high level of affinity to positively charged ions. Because of their chemistry, these groups lend themselves to being used in dentin adhesives. For this purpose, the phosphoric acid group is coupled to a methacrylate group. Because of its affinity to positively charged ions, the phosphoric acid group bonds to the calcium of enamel and dentin, while the methacrylate group establishes a chemical bond with the other polymerizable components of the adhesive.
For this purpose, most manufacturers use what are known as phosphoric ester compounds. These compounds, however, demonstrate one drawback: The C-O-P bond is not hydrolytically stable. Therefore phosphonic acid compound as an adhesive monomer is an ideal composnent. This compound is decidedly more stable, as the phosphorous atom directly bonds with a carbon atom (C-P).
High monomer content
Fusion Plus, Total-Etch Adhesive stands out amongst other adhesives because of its exceptionally high monomer content. While other adhesives contain up to 80% solvent (Prime & Bond NT), the solvent content in Fusion Plus, Total-Etch Adhesive is as low as 20%. Fusion Plus, Total-Etch Adhesive's high monomer content (>79%) facilitates the thorough polymerization of the adhesive resin layer. Consequently, users no longer have to use strong blasts of air to disperse the adhesive layer in order to allow the solvent to evaporate. This earlier drying procedure presented the risk of blowing away adhesive monomers and excessively thinning the adhesive layer. Fusion Plus, Total-Etch Adhesive requires only a weak stream of air to disperse the material to an even layer.
The success of an adhesive restoration, such as a composite filling, is dependent on many factors. The most important of all is certainly the skill of the dentist in placing such a restoration. Nevertheless, materials properties and performance also contribute to the quality of the restoration to some extent.
Most composites on the market have achieved a state-of-the.art that the mere clinical survival of a restoration is no longer a question of material choice. Of course, there are still considerable differences in, e.g., convenient handling properties for the dentist, tendency to accumulate plaque and stains or maintenance of a good surface gloss over a long time.
In contrast to dental composites, there are still considerable differences in performance among dental adhesives. This is impressively illustrated by recent reviews on clinical trials on posterior restorations and adhesives. Posterior restorations using up-to-date composite materials mostly show annual failure rates of less than 3%. In contrast, annual failure rates of adhesive restorations in non-carious Class V lesions vary between 0 – 48%. Furthermore, one-step self-etch adhesives (all-in-one) exhibited significantly higher annual failure rates than multi-component, two-step total-etch and two-step self-etch adhesives. Hence, a dentist’s choice of a clinically proven adhesive can substantially contribute to the success of his restorations.
Clinical trials with dental restorative materials require years until conclusive results are obtained or significant differences between products become apparent. During the development of a new adhesive it is therefore impossible to consider clinical data for decisions between several experimental variants. Furthermore, due to the typically very small numbers of similar dental restorations a patient needs at a time, it is mostly impossible to include more than one control product in a clinical trial.
Considering the above, it becomes obvious that laboratory investigations simulating the clinical application are the only means available to compare a new product with previous clinically proven products or with competitive products. Bond strength measurements on enamel and dentin and marginal quality or tightness are the most frequently used laboratory methods to predict the clinical performance of dental adhesives.
Fusion Plus, Total Etch Adhesive has been on the market since 2004. Therefore, many investigations with this product are available.Some examples are presented below.
Bond Strength Testing
Shear bond strength to dentin and enamel in comparison with other Total Etch adhesives. The shear bond strength of different commercially available
Total Etch adhesives was measured on bovine dentin and enamel according to ISO TR 11405. The handling procedure correspondents to the respective Instructions for Use. The bond strength was determined after storage in water at 37 °C for 24 hrs.
Under these conditions it could be shown that Fusion Plus, Total Etch Adhesive belongs to the group of Total Etch adhesives with the highest bond strength values to dentin and enamel.