Ask Dr. Christensen

Sept. 1, 2004
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].

by Gordon J. Christensen, DDS, MSD, PhD

Question ...

Recently, I cemented several anterior all-ceramic crowns with resin cement, preceded by a total-etch bonding agent. The crowns look wonderful, but the teeth are so sensitive that I may have to remove the crowns. How long should I wait before making that decision, and what can I do to prevent this sensitivity in the future?

Answer from Dr. Christensen ...

You have described a very common problem that has long been a challenge when using resin cements. If a total-etch bonding system is used before the resin cement, the dentinal canals are open to the irritation of whatever material is placed on them. If the primer and the bond of the total-etch system are used adequately, the dentinal canals are again filled with resin tags, and the postoperative tooth sensitivity is minimized or prevented. However, because of the complexity and technique-sensitivity of some of the systems, sealing of the canals is difficult to accomplish on a routine basis in a busy practice. After doing research on the subject — and suffering with several patients who had sensitive teeth after cementing with resin cements — I have the following suggestions:

Don't wait much longer than six weeks before removing the crowns. Waiting longer may require endodontic therapy. When the crowns are removed, cement new provisional restorations with a sedative cement, such as Tempbond.

In the future, use a self-etching primer before cementing with resin cement. The most popular brand of self-etching primer for indirect restorations is ED Primer II from Kuraray, used before cementation with Panavia F 2.0 resin cement. Several versions of this product have had successful use over many years. When self-etching primers are used, the "smear layer" is left on the dentin surface and the acid, primer, and bond of the self-etching primer product are incorporated into the smear layer. The clinical result is usually total prevention of the frustrating postoperative tooth sensitivity. However, even self-etching primers can produce post-operative tooth sensitivity if the primer liquid on the tooth is contaminated by moisture of any type during its use, or if the tooth is dried excessively. Be aware of these precautions.

Recently, a new cement (RelyX Unicem 3M ESPE) was introduced that combines the beneficial effects of self-etching primers with the resin cement in one application instead of two. Rather than applying the liquid self-etch separately from the resin cement, the self-etch is contained within the resin cement. Cementing with this cement does not allow as much potential for contamination of the surface of the tooth preparation during the cementation process. As the restoration is cemented, the cement and its incorporated self-etching primer are expressed from the margins of the restoration, precluding ingress of moisture or other contaminants and eliminating postoperative tooth sensitivity.

One of our newest videos shows use of RelyX Unicem in actual clinical cases using live, close-up digital video. This video — C504A "RelyX Unicem — A Unique Self-Etching Resin Cement" — will update you on this concept and its alternatives. For more information, contact PCC at (800) 223-6569 or visit us online at

Question ...

I have spoken to several general practitioner colleagues who have started doing implant surgery. Is implant surgery within the capabilities of a general practitioner, and, if so, in what locations in the mouth and under what circumstances should a general dentist accomplish implant surgery?

Answer from Dr. Christensen ...

Your question is one of my favorite subjects. I have the following suggestions for you:

1) Take an overall implant course that provides surgical instruction and information about the various brands available.

2) Purchase an implant surgery kit from the company that is most attractive to you. Nobel Biocare, Staumann, and 3I are examples of very popular companies. After taking the implant surgery course, find an appropriate patient who meets the characteristics described below. Treat the first few implant-surgery patients at the end of a clinical day to avoid conflict with your standard schedule while you are learning this procedure.

Assuming that the patient is healthy, cooperative, and interested — and that you have asked for and obtained a signed informed consent agreement with the patient — limit yourself to the following areas as you begin to learn and perfect your technique. Note:.informed consent discussions should include alternatives for treatment, advantages of each, disadvantages of each, risks, costs, and what happens if you do nothing.

* Mandible — The anterior portion of the mandible, extending from 5 mm anterior to the mental foramen, to the same point on the opposite side of the arch. This anatomic area presents very little risk, because there are no major blood vessels or nerves in the area, and the bone is usually of good quality.

* Maxilla — The anterior portion of the maxilla, extending from the anterior border of the maxillary sinus on one side to the same location on the opposite side of the arch. Again, as in the mandible, there are no major blood vessels or nerves in this anatomic area.

As you gain more confidence and experience, you may advance to areas of the mouth that are more difficult, including the maxillary sinus area and the maxillary tuberosity area, as well as the area posterior to the mental foramen on the mandible.

I have long tried to influence general dentists to try simple implant surgery. The majority of general practitioners will remove impacted third molars, but only a few general dentists will place implants. I am told by legal consultants that placement of implants into healthy patients who have a reasonable quantity of bone is far less legally threatening than removal of impacted third molars. As a restorative dentist (prosthodontist), I have been surgically placing implants for many years. I highly recommend to general dentists that they become involved with implant surgery.

Practical Clinical Courses offers courses on implant placement and restoration of implants. Two of our most recent videos show how to initiate yourself into implant surgery or at least to understand it better. These videos are beneficial for both restorative and surgical dentists: V2300, "Making Decisions About Successful Use of Implants" and V2301, "Simplified Implant Surgery." For more information, contact PCC at (800) 223-6569 or visit us online 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.

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