Targis, ProTec Cem

I have had 2 Targis/Vectris bridges fracture in the pontic area. The framework has remained intact, but the Targis material has fractured to expose the Vectris fibers. One bridge has been functioning well for the past three years. The other was in only six months. The retainers on these bridges are bonded inlays. Do you have any suggestions on how to prevent this from happening again? Any suggestions for alternate materials that might work better?

Michael Miller, DDS

I have had 2 Targis/Vectris bridges fracture in the pontic area. The framework has remained intact, but the Targis material has fractured to expose the Vectris fibers. One bridge has been functioning well for the past three years. The other was in only six months. The retainers on these bridges are bonded inlays. Do you have any suggestions on how to prevent this from happening again? Any suggestions for alternate materials that might work better?

Targis fracturing off Vectris has been reported before. One reason for these failures may be related to improper fabrication technique by your lab. One member of REALITY reported doing approximately 20 Targis/ Vectris bridges - mostly with inlay/onlay retainer designs - over the past three to four years, and all performed superbly.

It seems that Targis needs to be applied to Vectris immediately after the Vectris is polymerized. Otherwise, the bond between the two materials seems to suffer. And, while faulty lab work is certainly possible, the thickness of the Targis layer may also be a culprit.

Occlusal clearance of 2 mm will be best when using Targis over Vectris.

Is Targis 99 less likely to break at the abutment/pontic junction, or less likely to fracture at the Targis/Vectris interface than its predecessor?

It is our understanding that the improvements with Targis 99 relate more to the polishability and shade options with Targis itself, not the bond to Vectris or any other strength aspect.

I tried ProTec Cem to cement Procera and had cement failures with most within the first month. The ProTec Cem did not adhere even slightly to either the crown or the tooth, and I removed it from the crown in one piece. I now have three bottles of liquid and powder that I will not use again.

Another reader wrote: I got on the ProTec Cem bandwagon as soon as it came out. I`m sorry to say that I have experienced approximately a 40 to 50 percent failure rate. All failures exhibited no adhesion to the restoration nor to the tooth. I am an isolation freak and I follow instructions quite well. Personally, 40 percent is way too high for my patients and me, so I got rid of it. Recently I attended an advanced posteriors course and found out that quite a few other doctors were having the same problem.

Our tests showed ProTec Cem has no bond to tooth structure when it is used without an adhesive. Ivoclar has just introduced a conditioner, which is supposed to boost the bond strength of ProTec Cem to the preparation, but we have not yet evaluated its performance.

I used ProTec Cem for my first few Empress 2 cases. None of them came off, but sensitivity was a major issue. By the way, isn`t Vitremer LC contraindicated with all-ceramic crowns because of expansion?

One of our members also reported sensitivity with ProTec Cem, but felt it was it was due to the exposed and uncovered tooth structure (when doing crowns with supragingival margins) being "etched" with Astringedent during the preparation appointment. He reasoned that this etched tooth structure has never been covered with anything to protect it and the dentin tubules are wide open, resulting in sensitivity.

The solution for this doctor was to apply two coats of ED Primer from the Panavia 21 kit. He also reported having no problem with sensitivity when ProTec Cem was used to lute PFM crowns, which, we assume, had subgingival margins.

And, even though Nobel Biocare and 3M have teamed up in recommending the use of RelyX Luting (also known as Vitremer) with Procera AllCeram, we continue to suggest that you use a resin cement with any metal-free restoration, especially one with a preparation that has less-than-perfect mechanical retention.

Panavia 21 with ED primer remains our first choice for Procera AllCeram and In-Ceram.

Dr. 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, Texas. 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.

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