Are plasma-arc curing lights obsolete?

Michael Miller, DDS

Are plasma-arc curing lights obsolete? My understanding is that they cure at 10 seconds when other lights take 40. Even with only one effective size tip, I can move it over and cure again — and even again if I feel the restoration is too large — and that still is 10-20 seconds faster than the L.E.Demetron 1 (pictured at left).

While it is true that plasma arcs can generally cure faster than halogens, the speed ratio is not always 4:1 (40s to 10s). Many halogens can cure hybrids in 20s (although not at the bottom of the proximal box in a Class II). And, since you often need to overlap cures with plasma arcs, their speed advantage is further reduced. With their high cost, your ROI is also not great. Nevertheless, if you are successfully using a plasma arc, don't throw it in the trash. We merely believe there are more cost-effective curing lights on the current market that give you more bang for your buck.

With regard to the test results of dual-cure components, if one were cementing non-opaque all-ceramic restorations using OptiBond FL and Variolink II, are you saying to eliminate the dual-cure versions of both and simply light cure each line angle and occlusal surface for 40-60 seconds with, say, the 9 mm turbo tip of the Optilux 501?

Also, although we have been using Zenith/DMG's PermaCem for several years in gold-based restorations without any obvious difficulties, if we are to use an adhesive as now recommended, would OptiBond primer alone (light-cured) work, or would another product do this job better?

First, it is much better to light-cure the adhesive before seating the restoration, especially for those that are thicker than 2 mm. The film thickness of OptiBond FL probably precludes this precure. OptiBond Solo Plus, however, has a thinner film thickness and can be precured, but you need to be very conscientious when evaporating the solvent to keep the line angles free of pooled adhesive. The Turbo tip will be of little value, since most of its extra power dissipates rapidly as the distances from the tip to the tooth increases. Using an 11 mm tip would be much better.

Second, when PermaCem is used with a metal-based restoration, a dual-cure/self-cure adhesive such as Prime & Bond NT Dual Cure or Matrixx Cabrio CQ would be much better than merely using OptiBond primer.

Please revisit the problem of black stains under temporary veneers and onlays. I have noticed this phenomenon periodically within the last two years. At the seating appointment, it is not easy to remove. Regular hydrogen peroxide helps, but is not always complete, and may also require ultrasonics and/or subsequent pumice/rubber cup application. I am currently using Luxatemp resin in a preliminary impression for fabrication of temporaries. Veneer temps are either locked into embrasures, or spot bonded with approximately 2 mm etch and Prime & Bond NT on the mid-facial region of the prep. Posterior onlay temps are either cemented with TempBond NE (pictured at left) or spot bonded away from the margins as above. I have not noticed any staining under temp crowns cemented with TempBond NE. I suspect the black staining is due to microleakage under the unbonded margin, perhaps from a chromogenic bacteria.

1. Is the staining caused by bacteria or something else I may be using, such as Ultradent Viscogel?
2. What is the most effective way to remove the staining without affecting the final restoration's bond strength?
3. What is the most effective technique to prevent the staining prior to placing temporaries?

The cause of these types of stains has been discussed many times, with bacteria and iron-containing hemostatics being the two most frequently mentioned offenders. We would recommend trying a non-iron-containing hemostatic and applying a cavity disinfectant such as Consepsis to the preparation prior to placing the provisional. This disinfectant is applied after cleaning and drying the preparation and is not rinsed off. You actually dry the preparation again after applying the disinfectant. While this technique will not reduce leakage, its antimicrobial action seems to minimize discoloration and sensitivity. For posterior, partial coverage restorations, Durelon seals the tooth well and helps with retention. However, it is not as easy to remove as other types of cement.

1. I use Compolute for luting Empress. Will precured OptiBond Solo Plus do as good or better than priming and bonding? Also, will it work with any other dual-cured cement?
2. I like OptiBond Solo Plus very much. Can it be used with any resin cements as Cement-It! or Nexus2?
3. If dual-cure cements perform in a mediocre manner, I guess we will have to rely on self-cure for safe curing in deep areas when luting indirect restorations. Should we go back to Panavia 21?
4. Does L.E. Demetron 1 cure all materials?

Answers to 1 and 2 — OptiBond Solo Plus will work with all dual-cure cements assuming you can get light to the cement-adhesive interface. We believe this is possible if you are using a relatively strong curing light, your restorative material and cement are not overly opaque, and the thickness of your restoration does not exceed 5 mm. However, you could also simplify your life by using a light-cured cement instead of Compolute, which is no longer available anyway.

Answer to 3 — Self-cure is necessary for metal-based restorations, but a light-cured cement should be acceptable for metal-free. We are continuing our research into this issue and have published more results in the 2004 annual edition.

Answer to 4 — No, it will not cure materials that use an initiator other than CQ. The only L.E.D. that seems to cure all materials in the new Ultra-Lume LED 5 by Ultradent (pictured below). We have a report on it in the 2004 annual edition.

Dr. Michael Miller is the publisher of REALITY and REALITY Now, the information source for esthetic dentistry. He is an international lecturer and a fellow of the American Academy of Cosmetic Dentistry, as well as a founding member. He maintains a private practice in Houston. For more information on REALITY and to receive a complimentary issue of his monthly update, REALITY Now, call (800) 544-4999 or visit www.realityesthetics.com.