We have all hoped for better, easier and more complete bonding adhesives, and generations of adhesives have claimed to get us there.
Some have been improvements over their predecessors while others have not. So are the new “universal” bonding agents the answer?
The term universal is being used in three main ways. One refers to the capability of these adhesives to adhere by different application methods, namely self-etch, total etch or selective enamel etch. Another is the capability to be used with all light, dual and self-cure materials. The last is the ability to adhere to all common dental substrates including direct and indirect restorations and repairs.
Kerr's Optibond XTR, Bisco's All Bond Universal, and 3M's Scotchbond Universal can be used by self-etch, total etch and selective enamel etch and are universal in that way. However, Kerr doesn't advertise or recommend using their material in total etch or selective enamel etch mode because their product etches cut and uncut enamel very well and maintains the bond over time. For indirect applications, 3M and Bisco recommend selective or total etch for maximum bond to strength.
All work with light
These three products work with all light, dual and self-cure materials and are universal in this way. The materials work simply and easily with light cure materials. However, there are differences in how they accomplish compatibility with dual and self-cure materials.
Kerr's material is easiest to remember since it will bond with all dual and self-cure materials with no extra steps or materials and it will cure in dark mode. 3M's product needs to have a dual cure activator added when used with dual and self-cure materials unless used with 3M's RelyX Ultimate cement.
3M's product will dark cure only with 3M's RelyX Ultimate cement. Bisco's product does not need a dual cure activator but it does need to be light cured before application of the dual or self-cure material. This Bisco material will not cure in dark mode so if light will not reach the adhesive Bisco recommends using Z-Prime Plus to prime the substrate to be bonded. This is applicable if you want to bond a restoration that light will not pass through (metal or opaque substrate). The adhesive on the tooth needs to be light cured and Z-Prime Plus is applied in the restoration before applying the dual or self-cure cement. The bond strength with Bisco's Z-Prime Plus is lower than Kerr or 3M but still acceptable.
All three adhesives are universal in that they work well when applied to these dental substrates: alumina, resin, glass ceramics, lithium disilicate, zirconia, titanium and other metals. Kerr does it with no additional materials. 3M needs to be used with RelyX Ultimate cement for dark cure or a dual cure activator for dual or self-cure mode if not using RelyX Ultimate. Bisco needs Z-Prime Plus for dark cure.
All have a silane coupling agent
Traditional silane coupling agents and metal and zirconia primers are unstable and lose their activity quickly so the bond strength may be questionable; these new materials are very stable. All of these products have a silane coupling agent and primers (metal and zirconia) included in the formula.
This means that bonding to resin, lithium disilicate, alumina, glass ceramics, zirconia, titanium and other metals no longer requires a separate silane or primer application except with the afore mentioned dark mode use of Bisco + Z-Prime Plus.
Kerr and 3M are filled resins and Bisco is unfilled. Kerr has included a fluoride filler into their product however once any adhesive is set it is unlikely that enough fluoride is released to provide anticaries efficacy. Fillers add a measure of flexibility, which is theorized to assist with retention of stiff materials like nanohybrids and flexible materials like microfils when used in high stress class V areas.
Flexibility is also theorized to allow some stress absorption during polymerization shrinkage that may lower post-op sensitivity. Fillers may also strengthen the hybrid layer. It's important to note that this is all theory.
Follow the instructions
Finally, filled adhesives are usually placed in one application whereas unfilled need two or more applications for good coverage. What we know is if you follow the manufacturer's instructions, all of these materials work very well and do not have sensitivity issues.
Cost is always a factor in controlling overhead and adhesives are expensive when you look at $/ml. In light cure mode Bisco is the least expensive and Kerr is most expensive. When used in dual or self-cure mode with good light penetration Bisco is still least expensive and 3M is most expensive (unless using 3M with RelyX Ultimate cement then Kerr is most expensive). When used in dark mode Kerr is least expensive and 3M is most expensive. Consider the way you use your materials and which is easiest for you.
All three of these universal bonding agents appear to be great materials and improvements on previous materials by reducing steps which limits mistakes, and reducing armamentarium which controls cost. Are these the answer to our bonding needs? I say they're all worth a try.
Robert A. Gallegos DDS, FAGD, Spear Visiting Faculty. [ www.middleburgsmiles.com ]