Ask Dr. Christensen

Feb. 1, 2004
Over the past several years, I have placed many Class II, resin-based composite restorations. Overall, they work very well, and I enjoy the technique, the materials, and the aesthetic results.

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 protected].

Question ...

Over the past several years, I have placed many Class II, resin-based composite restorations. Overall, they work very well, and I enjoy the technique, the materials, and the aesthetic results. However, some patients complain of slight to severe post-operative sensitivity in their restorations, and some teeth require endodontic therapy. I am changing to self-etching primers, which I have been told reduce or eliminate post-operative tooth sensitivity. When the sensitivity is present, is it better to replace the restorations immediately or to wait a period of time? If waiting is advisable, how long should I wait before redoing the restorations when sensitivity is present?

Answer from Dr. Christensen ...

You are well advised to change to self-etching primer. Most practitioners who have changed from total-etch to self-etching primers for Class II resin restorations have almost eliminated post-operative tooth sensitivity. I feel that your problem will be reduced significantly, if not eliminated.

Post-operative tooth sensitivity can be caused by numerous factors. Among them are: Occlusion too high on the new restoration, tooth preparation very close to the pulp, previously present pulpal degeneration, trauma caused by the tooth preparation, partially polymerized resin, improper priming of the dentin surfaces on the internal of the tooth preparation, a new or old crack in the tooth, or several other reasons.

Waiting a long time after pain manifests can cause increased pulp degeneration, increased pain, and eventual endodontic need, or partial healing of the pulp and reduction or elimination of the pain. When deciding what to do, it is impossible to determine whether to replace the restoration or to wait for a while. From years of experience, I have set a time limit of six weeks to wait before removing the restoration or beginning endodontic therapy, or both. Of course, there are causes for many deviations from the six-week guideline. If the patient demands that something be done, you must remove the restoration sooner. If other negative signs or symptoms appear that conclude the restoration is defective, or the tooth requires endodontic therapy, it is foolish to wait for six weeks. When the restoration is removed, most practitioners place a provisional restoration that is zinc-oxide/eugenol based. Usually the pain disappears. If it does not go away within one or two days, the tooth probably needs endodontic therapy, followed by a new restoration or crown.

Two of our videos will further answer your questions on this topic — C901A, "You Need Self-Etching Primers," and C501B, "Predictable Long-Lasting Class II Resin Restorations." For more information, contact PCC at (800) 223-6569, fax (801) 226-8637, or visit our Web site at

Question ...

After placing a direct placement restoration or a crown, I have been making a radiograph of the area to determine if overhangs are present. Is this an advisable practice? Some of my colleagues tell me that they never make radiographs after completing restorations.

Answer from Dr. Christensen ...

Many years ago I accomplished a research project that changed my beliefs on the subject of evaluation of margins by using radiographs. Before the project, I thought that radiographs would show a subgingival margin opening. To my frustration, the research project showed that the margin had to be grossly open before that opening was confirmed on the radiograph. Since then, I have made some rules for my own use of radiographs to evaluate open or closed margins or overhangs. Proper positioning of a radiograph can show some characteristics of margins, or seating of restorations. However, the best evaluation is to visualize the margin. Try to retract the gingiva with an instrument or a cord to see if there is an overhanging restoration or an open margin. You may have to turn the patient's head quite significantly to see the interproximal margin. Using unwaxed thin floss, such as Glide, which is available in any grocery store or pharmacy, is an excellent test for overhangs or even significantly open margins.

In summary, I suggest that radiographs show only large overhangs or grossly open margins, and visual observation is a much better method to determine if a margin is open or closed.

The following video shows proper positioning of radiographs for most situations and is a must for staff members — V1158, "Simple, Fast, High Quality Dental Radiographs" (Intraoral). For more information, contact PCC at (800) 223-6569, fax (801) 226-8637, or visit our Web site at

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.

Next month in Dental Economics ...

Dr. Joe Blaes looks at "The Veneer Case From Hell," while authors Patrick Wahl, DMD and Lorraine Hollet discuss "Colossal Case Acceptance." Also coming up: Informative features on digital imaging, implementing the paperless office, and improving customer service for your patients.

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