Ask Dr. Christensen

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 info@pccdental.com.

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 info@pccdental.com.

Question …

I am confused about the type of resin cement to use with ceramic veneers. I have been using light-curing resin cement for several years with success. However, I see some of the resin cements for veneers are advertised as dual-cure. Why would I want dual-cure cement for veneers? Should I change to this type of resin cement?

Answer from Dr. Christensen …

Ceramic veneers have been used for many years, and the profession has had enough experience to make some logical conclusions about the indirect veneer technique. Over the years, numerous changes in techniques have occurred. Tooth preparations have changed; some practitioners are preparing teeth for veneers much deeper than in the past. I will answer your questions in relation to both conservative veneer preparations and the deeper veneer preparations now performed by some dentists.

Whenever possible, I prefer conservative tooth preparation and thin ceramic veneers placed on enamel surfaces instead of dentin surfaces. Such veneers have excellent bond to enamel surfaces, preventing veneer dislodgement, and minimal chance of producing postoperative tooth sensitivity. The color of these thin (0.5 to 0.75mm) veneers can be slightly altered by the color of the resin cement. This characteristic is desirable, because it is often necessary to change the color of the veneer to perfectly match surrounding dentition. The color of thicker veneers (1 to 2mm) cannot be altered by cement color.

Some dual-cure cements contain auto-curing polymerization chemicals that cause the cement color to change over time to a darker brown-orange. The underlying cement color can significantly alter the color of thin veneers. If the veneer is thick, the potential minor color change of the cement is not a problem except at the margins. In thick veneer situations, the dual-cure cement may be desirable because of the inability to penetrate thicker veneers with a curing light.

I prefer thin, conservative ceramic veneers, which save tooth structure, have an excellent bond to etched enamel, and can match natural tooth structure nearly exactly. When using conservative veneers, light-cure resin cement is my choice. This allows more time when placing veneers, the ability to remove the veneer before curing if it does not seat well, and no postcementation color change. However, if it is necessary to provide thicker veneers that may inhibit light penetration, consider dual-cure cement.

A recently made Practical Clinical Courses video — V1584, "Veneers – All Types" — has been very popular and useful on this topic. Contact PCC at (800) 223-6569, fax (801) 226-8637, or visit www.pccdental.com.

Question …

I recently made a complete denture for a patient using resin teeth. I was pleased with the result; the denture looked very good to me. The patient returned for an adjustment complaining, "The teeth are dull and will not chew food well." The patient's old denture was a poorly fitting prosthesis with broken porcelain teeth in it. The patient wanted the teeth to be "sharpened." Can porcelain teeth chew better than resin teeth, and should I be using porcelain teeth?

Answer from Dr. Christensen …

Your question is one I hear often. I have encountered the situation you describe many times in my own practice. Yes, porcelain denture teeth give patients the feeling that they "chew better" than resin teeth. Some patients can feel this difference as soon as they eat, while others wear the denture for a while and don't complain until the resin teeth wear down to rounded anatomy.

As you know, fired porcelain is very hard and wear-resistant. When two opposing surfaces of porcelain denture teeth come together, they provide hard, nonyielding contacts that do not wear down into rounded surfaces. Conversely, resin materials are relatively soft compared to porcelain, and soon become rounded and blunt. The result is that patients do not feel the same cutting ability with resin teeth as with porcelain teeth.

Use of porcelain denture teeth has decreased over recent decades. Many dentists do not use them in complete or partial dentures. Porcelain teeth require more laboratory expertise and more time during both the laboratory and the clinical portions of the denture technique. If the denture occlusion is incorrect, it is more difficult to adjust porcelain teeth than resin teeth.

I suggest that if a patient has had porcelain teeth in his or her denture in the past, you should consider using porcelain teeth in the new denture. I remade numerous dentures before I came to this conclusion.

Our Practical Clinical Courses video — V2577, "Partial Dentures – 21st Century" — demonstrates my own conclusions and techniques on this and many other topics related to removable partial dentures. Contact PCC at (800) 223-6569, fax (801) 226-8637, or visit 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.

For a review of questions and answers from Dr. Christensen over the past few months, please visit www.dentaleconomics.com.

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