by Gordon J. Christensen, DDS, MSD, PhD
In this monthly feature, Dr. Gordon Christensen addresses the most frequently asked questions from Dental Economics readers. If you would like to submit a question to Dr. Christensen, please send an email to email@example.com.
I have tried several porcelain repair kits from different companies. Although I have performed the clinical procedures according to the manufacturers' instructions, I have met with failure most of the time. What am I doing wrong?
Answer from Dr. Christensen ...
Please don't feel alone. Most practitioners have had the same results when trying to repair fractured porcelain-fused-to-metal crowns with the materials provided in porcelain repair kits. The use of these kits seems logical: Roughen the underlying metal substructure, place some metal adhesive on the surface, place the appropriate color of tooth-colored resin on the surface, cure it, and finish it. The result usually looks good, but stains soon become evident at the junction of the resin repair and the porcelain. In some cases, the resin repair "falls off" within a few months. This is due to the combination of materials and the differences in coefficient of expansion/contraction of the remaining porcelain and resin restorative material.
I use the porcelain-repair concept only for temporary repairs of fractured tooth-colored crowns, and I advise patients that the repairs are temporary. There are many kits available for these repairs. One that has had good reports from Clinical Research Associates evaluators is the Ultradent Products Porcelain Repair Kit — Ultradent Products, Inc., (800) 552-5512.
There are longer-lasting repairs, but they are more complex and cost the patient more money. I suggest using the technique described in the following question for long-term repair of restorations.
I have not had success with porcelain repair kits. The ads always look promising, but my results have been dismal. What should I use when there is a legitimate need to repair a porcelain-fused-to-metal restoration?
Answer from Dr. Christensen ...
After many years of practice, I have had my share of patients who needed to have porcelain-fused-to-metal restorations repaired. I used the porcelain-repair-with-resin concept as early as 1976. In areas of low stress, the resin repairs occasionally worked for a while, but the characteristic brown line between the repair material and the porcelain gradually appeared. As a result, patients were not satisfied with the appearance of their repaired restoration.
Many factors influence my judgment about whether or not to attempt a restoration repair. If the broken restoration is a single crown, my decision is almost always to replace the crown. If needed, resin repair may be used as a temporary measure until the new crown can be scheduled. If the broken restoration is a multiple-unit restoration, I will consider repair more seriously. The patient must be advised thoroughly about the alternatives for the broken restoration. Only infrequently will I consider repair of the broken restoration with resin. The most adequate repair is an over-crown.
I am surprised that many dentists do not know how to use over-crowns. In my many years of clinical experience, I have had only a few failures with them. Over-crowns are my favorite repairs for broken, multiple-unit porcelain-fused-to-metal restorations.
A caution is necessary, however. Be sure to carefully evaluate the broken restoration to be positive that it is still cemented to the underlying tooth structure. From time to time, broken multiple-unit restorations are loose on one end, and that may be the reason they are broken.
The over-crown technique is relatively simple:
1 Remove the ceramic from the facial and lingual surfaces of the restoration. Leave the connection between the broken unit and the unbroken units intact.
2 Remove as little metal understructure as possible to allow as much strength as possible to remain in the substructure. However, extend the facial margin of the repair crown preparation far enough apically to allow optimum aesthetics for the new over-crown restoration. The preparation will now be a facial-occlusal-lingual or facial-incisal-lingual preparation. When possible, contacting areas with adjacent teeth can be prepared to allow as much retention as possible for the new over-crown restoration.
3 Pack cord as usual on the facial and lingual surfaces of the tooth or pontic involved.
4 Make an impression as usual.
5 Noble or base metal is best for the understructure of the over-crown, since it is stronger than high-noble metal. It also can be thinner, providing a less bulky over-crown.
6 Prescribe an over-crown of the appropriate metal and color from the laboratory technician, and have the over-crown constructed.
7 Try on the over-crown, checking for fit, color, and occlusal contacts. Adjust as necessary.
8 Sandblast the internal surface of the over-crown and the external metal or ceramic surfaces of the preparation. Be careful not to sandblast the gingival tissue, because it will cause bleeding.
9 Using appropriate resin cement — such as Panavia-F from Kuraray America, Inc., (800) 879-1676 — to cement the over-crown into place.
10 Adjust occlusion.
11 Advise the patient of the approximate longevity expectations of the repair.
I have had great clinical success with such repairs. Both the aesthetic and functional results are excellent. Patients save a significant amount of money, and they appreciate the conservative nature of the repair. The cost of the over-crown should be about the same as a normal porcelain-fused-to-metal crown.
Our Practical Clinical Courses video — V19-93, "Long-Term Maintenance and Repair of Fixed Prostheses" — demonstrates the techniques for this and other repair needs in fixed prosthodontics. To purchase a video, call (800) 223-6569, fax (801) 226-8637, or visit our Web site at www.pccdental.com.
Dr. Christensen is a practicing prosthodontist in Provo, Utah. He is the founder and director of Practical Clinical Courses, an international continuing-education organization for dental professionals initiated in 1981. Dr. Christensen is a co-founder (with his wife, Rella) and senior consultant of Clinical Research Associates, which, since 1976, has conducted research in all areas of dentistry and publishes its findings to the dental profession in the well-known CRA Newsletter. He is an adjunct professor at Brigham Young University and the University of Utah. Dr. Christensen has educational videos and hands-on courses on the above topics available through Practical Clinical Courses. Call (800) 223-6569 or (801) 226-6569.
Dr. Christensen's views do not necessarily reflect the opinions of the editorial staff at Dental Economics.