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 e-mail to [email protected].
Q: A colleague of mine insists that I should not use eugenol-containing provisional cements when I am planning to use resin or resin-modified glass ionomer cement as the final cement for long-term restorations. I have heard various opinions on this subject, and I have even seen “peer reviewed” research that supports both sides of the question. What is the correct provisional cement to use in these situations?
A: This question is highly pertinent, and one we frequently hear from attendees of continuing-education courses. You are undoubtedly cementing many crowns and fixed prostheses on a routine basis. If eugenol-containing cements do interfere with the set of the final cement, significant potential damage could be done to patients and your pocketbook. I have researched this subject clinically and in the international literature. I will try to make the answer to your question a practical one.
Most dentists use the following schedule for crowns or fixed prostheses: they prepare teeth for crowns or fixed prostheses on a given day, and the average time that elapses between the tooth-preparation appointment and the final seating of the crown or fixed prosthesis is two weeks or more. This allows adequate laboratory time for the technician to make the restoration.
The time between your use of eugenol-containing cement and your seating of the final restoration holds the answer to your question. If you were to seat a crown with resin cement a day or two after you seated the provisional restorations with eugenol-containing cement, your colleague would be entirely correct about using these cements. The final cement would be severely affected by the free eugenol in the provisional cement.
On the other hand, if your crowns and fixed prostheses are seated two weeks after you have seated the provisional restorations with eugenol-containing cement, there is nothing to worry about. By this time, the free eugenol has been dissipated by chemical integration with the zinc oxide, and the final cement is not affected by the mature eugenol-containing provisional cement. Of course, you should clean any remaining visible particles of mature, set eugenol-containing cement from the tooth preparation surfaces before final cementation.
Another factor is related to your question, and many dentists do not appear to know about what I am going to suggest. Noneugenol-containing provisional cements occasionally create tooth sensitivity while the provisional restoration is being worn. Although this occurs in a small percentage of patients, it is an objectionable characteristic.
You may not be aware that provisional cements now come in several dispensing systems. The conventional two-tube concept popularized by the classic TempBond® is still the most popular delivery system, but the tubes often burst, extruding the cement and making a mess. The cements are also available in small auto-mixing syringes that are easy-to-use and store without leakage. I prefer to use a third type of dispenser. Large auto-mix syringes hold enough provisional cement for many temporary cementations. An example is TempoCem®, and there are many other brands. The negative sensitivity-producing factor related to noneugenol provisional cement has influenced me to use eugenol-containing provisional cements unless the patient has a eugenol allergy or I am going to seat the final restoration only a few days after the provisional restoration was seated.
See our video on provisional restorations and techniques. It includes close-up demonstrations of all types of provisional materials, cements, and techniques. An excellent overview for dentists or dental assistants, it is a great training video.
For more information, ask for DVD V1928, “Effective Provisional Restorations,” contact Practical Clinical Courses at (800) 223-6569, or visit our Web site at www.pccdental.com.
Q:Recently, I seated six pressed-ceramic anterior crowns on a 25-year-old patient. Because I know that pressed ceramic crowns have only moderate strength, I cemented them with resin cement that had a total-etch bonding accompanying the cement. I used the manufacturer-suggested and included bonding agent. After cementation, the patient complained of severe tooth sensitivity. I am concerned that I may have to remove the crowns to reduce or eliminate the tooth sensitivity. Is there anything I can do for this patient? What did I do wrong and how can I avoid the problem in the future?
A: You were correct in using resin cement. Although extremely beautiful, pressed-ceramic crowns have only moderate strength, and they can use the extra, overall strength provided by resin cement. However, your choice of cement brand and bonding agent might have been better.
Our research on resin cements placed on cut dentin has shown that if a total-etch bonding system is used, the dentinal canals must be completely sealed by the bonding agent before cementation or postoperative tooth sensitivity will occur. In a busy practice a complete sealing with the total-etch concept is often difficult to obtain on a routine basis.
In a study CRA did several years ago using resin cement and a total-etch bonding system, 37 percent of the patients experienced postoperative tooth sensitivity in the first year after cementation, and 13 percent required endodontic therapy on the restored teeth. (Clinical Research Associates, Filled Polymer Crowns – 1 & 2 Year Status Reports. CRA Newsletter 1998; 22(10): 1-3.) Let’s avoid that unfortunate problem with the following suggestions.
What could you have done to prevent this problem? 3M ESPE brought a cement named RelyX™ Unicem to market a few years ago. It is a resin cement containing a self-etch primer. Numerous companies have followed their lead and produced similar cements. These cements have the strength of resin, but the sensitivity-preventive characteristics of self-etch bonding systems. Another well-known nonsensitivity-producing resin cement is Panavia F from Kuraray Dental, which comes with a self-etch bonding system applied before placing the resin cement. A similar newer resin is Multilink Automix from Ivoclar/Vivadent. This cement contains a two-component, self-etch bonding system to be applied before the resin cement. It is one of the strongest resin cements on the market, and it has very good radiopacity, which is important under all-ceramic crowns, inlays, and onlays.
What can you do for the unfortunate patient you described in your question? There is a chance that the sensitivity will go away in a few weeks. On a very empirical basis, I have decided that if the tooth sensitivity has not gone away in six weeks, I must remove the restorations and try to sedate the teeth with provisional restorations cemented with zinc-oxide eugenol cement. Even then, some of the teeth will become nonvital.
I wish you success in treating this patient and in avoiding this problem in the future.
