VLC vs. Dual-Cure Dental Products

Many dental products are offered in either a dual cure (curable in either self-setting or light activated curing) or VLC (Visible Light Cure only) setting. Selecting which configuation can have long term effects on the success of the restoration. Each offers distinct advantages and can be a practice requirement in particular situations. Let's take a look at what these different advantages can be and examine where these two product options are heading.

Historically, the primary advantages of a VLC product were control over when the product starts to set. Composite resins for example once were provided in self-cure only, with no light cure option. (This required mixing of two parts, recall some of the older composites like Adaptic?) Air bubbles often resulted and the operator was rushed into placing the material before it set up. Beyond these inconveniences, these self-cure composites yellowed over time due to their chemistry.

Composite resins today are almost exclusively offered as VLC only. There is no need to offer these products in a dual cure option. Improved handling, reduction in air bubbles and improved aesthetics are the result. We are seeing now the same enhancements when it comes to some other products. The trend is to eliminate mixing, air incorporation, and simplify use of the product, i.e. no triturators, no special applicators, etc. This focus is particularly true for highly asethetic restorations such as veneers and their cements. (Know of anybody placing self-cure direct composite veneers? - I don't think so). The dual cure products in the veneer cement category are recognized by many leading clinicians to be at a distinct disadvantage. There are some restorations where dual cure products are however still necessary.

In the cementation of a cast metal crown, light access through the crown is not possible, therefore a self-curing cement is required. Porcelain-fused-to metal is another example where light access is not possible. In both cases aesthetics is not the primary concern. (In this example, the light cure chemistry also serves no purpose.) A slightly different situation exists for cementation of endodontic posts, where light access though limited, is still best conducted with dual cure products. In this case however, light curing of the exposed surface allows the procedure to continue without waiting for the much slower self-curing reaction to occur. In this case a self-curing product is required but a dual curing product is an advantage.

Another advantage of light curing versus self-curing is the VLC reaction often results in superior properties compared to the self-cure mode; the material is stronger, harder, has a better surface, and is more completely cured. Where light access is possible, the depth of cure of the product can also be a factor. This means how far will the curing light penetrate through the material and produce a good set. For some products, such as core materials, this can be an issue, when applied in a thickness that exceeds their depth of cure. This concern has been overcome with better curing VLC core materials. Many light cure only core materials have successfully been on the market for several years.

Core applications of limited thickness of only 2-3mm also exist, far below the the depth of cure of these new VLC only products of 5-10 mm. The important point is to check that the depth of cure of such a product exceeds the thickness of the core material that you are placing. For those using the core form technique this may be a factor. Using VLC core materials results in better overall curing, better physical properties, and greater operator efficiency in control and time. In this situation, addition of self-curing components serves no purpose.

Today the most recent advances in VLC products are cements that are intended for all-ceramic restorations. In this situation, the criteria is that the light must be able to penetrate the restoration and result in a complete cure of the cement. For anterior restorations, which are small and light access is excellent, an aesthetic result is highly preferred to the yellowing of the cement that occurs later. In posterior applications, all-ceramic restorations have not yet completely proven themselves, also they tend to require thicker walls due to greater biting forces, and light access is also not as easily achieved.

Some examples of these different dual cure vs. VLC applications are shown in the cases below. Shown first is a core build-up repair of a broken implant abutment. This repair was done with a VLC only core material, saving the abutment and resulting both cost and time savings, not to mention convenience to the patient. The repair was done quickly by light curing only.

Another example is the cementation of an all-ceramic crown. In this instance a highly aesthetic result has occured.










In this example, AURA VLC is being cured beneath a Cerec all-ceramic crown. This illustrates how a ceramic crown acts as a light conductor to illuminate the entire crown surface. This resulted in a good cure and a long lasting restoration. (Photo courtesy of Dr. Paul Schoenbeck-Gorham, NH)

In summary, dual cure products are required where light access is not possible. Self curing products in this instance offer the same benefits as dual cure products. VLC products today provide advantages in physical properties, operator control, and asethetic results. Advances in new light technology, such as high powered lights and LED configurations add to the success of these VLC products. In the future look for more circumstances where VLC products will replace dual cure and self cure products.