Ask Dr. Christensen

Sept. 1, 2001
In this monthly feature, Dr. Gordon Christensen addresses the most frequently asked questions from Dental Economics readers.

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 regarding new techniques or products to Dr. Christensen, please send an email to [email protected].

Question ...
Can I use self-etching primers, such as Clearfil SE Bond, with my regular restorative resins from other companies?

Answer from Dr. Christensen ...
Because of their acceptance by dentists around the world, many companies are now developing self-etching primers. Until all companies have self-etching primers specifically designed to be compatible with their restorative resins, the question is a very pertinent one. The most commonly used self-etching primers at this time appear to be:

  • Kuraray's Clearfil SE Bond and Clearfil Liner Bond 2V
  • 3M ESPE Prompt L-Pop

I certainly wish that we had research data on the bond of these popular self-etching primers to all of the restorative resins, sealants, flowables, compomers, and other resins. To date, this research has not been done. I suggest that you run the following simple test in your own office:

  1. Obtain some extracted molar teeth.
  2. Cut the enamel from the occlusal surfaces of the teeth, leaving only dentin on the occlusal surface according to manufacturers' instructions.
  3. Place the bonding agent of your choice on the cut dentin surface.
  4. Place the restorative resin or other test material of your choice on the tooth over the bonding agent.
  5. Cure the resin.
  6. Place the tooth specimen into a cup of water and let it sit for at least 24 hours.
  7. Remove the specimen from the water bath and attempt to remove the resin from the tooth with a sharp instrument.

You will be amazed to see that some of the resins will separate from the tooth specimens with almost no effort. On the other hand, some of the self-etching primers will retain the resins very well.

I believe clinicians would agree that the most important, positive characteristic of dentin bonding agents is not the bond, but the ability of the bond to prevent postoperative tooth sensitivity. However, it is desirable to have both a strong bond and desensitization. When considering bonding agents for large restorations or buildups that are prepared close to the pulp, both bond and desensitization are important.

In our observations to date, Clearfil SE Bond appeared to bond to most resins, while Prompt L-Pop bonded to restorative resins, but did not bond well to many of the build-up materials (see the CRA Web site for complete information — 3M ESPE is changing the product to correct that problem. Clinical Research Associates soon will report the results on a large project related to this important question. In the meantime, you must do your own experimentation with the extracted tooth project.

Question ...
Is the KaVo DIAGNOdent a reliable way to show the presence of occlusal caries, and should I buy it?

Answer from Dr. Christensen ...
At this time, dental radiographs do not show dental caries well. In some of our studies, it was found that typical D- or E-speed radiographic films showed only about one-half of the actual depth of carious lesions when extracted teeth were dissected, and the lesions were observed visually and under a microscope.1,2 The reduced level of diagnostic ability is related to lower levels of radiation used by current radiographic machines. The KaVo DIAGNOdent has been evaluated by CRA, and it has produced very reliable diagnostic results for Class 1 and visible smooth-surface carious lesions. It is not intended to detect Class 2 or 3 lesions. The device works on the concept of red laser penetration into the tooth surface. If the red laser beam on the DIAGNOdent is stopped or impeded by caries, stain, or calculus, the device shows a number, indicating the presence of interference with the laser beam. Obviously, calculus or stain must be removed from suspect teeth before obtaining a DIAGNOdent reading, or the reading will be inaccurate.

As with any electronic device, a learning curve is present, and dentists should expect to spend some time becoming accustomed to the device.

I suggest that dental staff members should be trained on use of the DIAGNOdent to record readings on the status of suspicious pits and fissures on teeth. If the DIAGNOdent readings are high enough, the carious lesions should be restored. If the readings are low, most dentists using the DIAGNOdent prefer to wait until a future recall appointment to test the lesions again. When the DIAGNOdent shows high readings on suspect teeth, the lesions should be restored.

Several other caries-detection devices are being developed. Clinical Research Associates has some of these under evaluation. As the concept continues to mature, we will report the information to the profession. I predict that devices such as the DIAGNOdent will become widely used in the future as the need for more conservative restorative dental procedures increases. It is a valuable adjunct to caries detection and worthy of purchase.

More on this subject from Dr. Christensen is available on the video C501A "Diagnodent — Scientific Diagnosis of Caries" and C501B "Predictable Long-Lasting Class 2 Resin Restorations." Call Practical Clinical Courses at (800) 223-6569 for information.


1 Christensen, G.J. "Dental Radiographs and Caries: A Challenge." JADA 127 (6), pp 792-793, 1996.

2 Christensen, G.J. "Initial Carious Lesions: When Should They Be Restored?" JADA 131 (12), pp 1760-1762, 2000.

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.

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