Ask Dr. Christensen

Nov. 1, 2002
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 to Dr. Christensen, please send an email to [email protected].

Question ...
In recent years, I have had to accomplish a significant amount of endodontic therapy on teeth that I have restored with crowns. I am wondering if I use enough water spray during tooth cutting. How much is required to cool teeth adequately during tooth-preparation procedures?

Answer from Dr. Christensen ...
There are many factors involved in this question. Numerous parts of the fixed-prosthodontic procedure can injure the dental pulp and cause the need for endodontic therapy. One of the most potentially traumatic challenges in tooth preparation for crowns is inadequate lubrication and cooling while cutting tooth structure. In a clinical study to determine efficiency of rotary-diamond cutting instruments by Clinical Research Associates, CRA found that practicing dentists reported using varying amounts of water when cutting teeth for crown preparations. Some dentists used almost no water spray at all, while others used so much that it was difficult to see the tooth being prepared. Water use ranged from a few cc per minute to 20 cc per minute. On the extreme end of the continuum, some clinicians have suggested that up to 40 cc of water per minute should be used. This amount of water coming from the handpiece makes dental therapy extremely difficult because of visual limitations. Other clinicians use so little water that brown or black burned areas appear on the tooth during cutting. Both of these examples are extreme. I recommend a medium amount of water.

Measure the amount of water that you use while cutting crown preparations by running the handpiece with the water going into a cc-measuring vial for one minute. If you have 5 cc to 10 cc, you are in the median of what others use. However, I have a clinical suggestion for you that will aid in determining the amount of water spray needed. This simple procedure is one I require of dental assistants who work with me, and it is easily accomplished.

Every clinician has seen the gray sludge that accumulates from time to time when cutting tooth preparations. I suggest that as soon as the dental assistant sees any indication of the sludge on the tooth preparation, he or she should deliver a spray of air/water from the syringe to the affected tooth area. This allows the use of minimal water coming from the handpiece for good visibility, yet still keeps the tooth well-lubricated and cool when the water spray is inadequate.

A Practical Clinical Courses video related to this topic has been very popular and useful. Item number V19-38 — "Tooth Preparations for Fixed Prosthodontics" — can be purchased by calling (800) 223-6569, faxing to (801) 226-8637, or visiting

Question ...
I have seen many articles and ads on the CEREC system available from Patterson. The concept interests me, but I am hesitant to put so much money into it. Is the CEREC system reliable and clinically acceptable, or can I do everything it does by using laboratory technicians?

Answer from Dr. Christensen ...
You probably are interested in computer technology since you are inquiring about the CEREC system. The dentists who have been most successful with computerized dentistry are those who have a fascination and ability with computers, or those who are willing to learn. The CEREC device has evolved into a predictable clinical instrument for the production of inlays, onlays, and some crowns. The people who have been instrumental in developing the CEREC concept have had great persistence to weather the many obstacles present when computerized restorative dentistry was introduced. Many other computerized restorative instruments have come and gone, while the CEREC system has undergone continual change and improvement.

Clinical Research Associates has worked with the CEREC device through the entirety of its development. The following observations are related to the clinical and research experience we have gained with the device:

• Yes, the CEREC system is expensive, but lease programs allow a minimal level of financial stress for those interested in obtaining one. After you achieve clinical competency, the CEREC concept helps to pay for itself, since there is not a laboratory bill for the restorations.
• There is a learning period, just as you might expect with any high-tech device. Some time is required to learn the computer aspects of the procedure and the clinical differences between the CEREC technique and typical dentistry.
• You must market the concept to your patients. Many are very interested in saving as much tooth structure as possible, and inlays and onlays are attractive options when compared to crowns. Additionally, patients are fascinated by the computer-directed milling of the restorations, whether crowns or less-aggressive restorations.
• When accomplished well, the restorations fit very well.
• One of the most challenging aspects of the CEREC concept is matching tooth color when the restorations are close to the front of the mouth. However, new color-matching techniques are being developed.
• Over the 10 years that Clinical Research Associates has studied the clinical adequacy of restorations made by the CEREC system, their service record has been very good.

In summary, if you have an interest in the CEREC concept and you are willing to take the time to learn this exciting technique, there are many dentists who have found it to be a viable and financially successful concept. I suggest that you seek out a colleague who has the CEREC system and obtain that doctor's candid opinion and observations about it.

Our Practical Clinical Courses Forum offers my own conclusions and techniques on this topic, as well as demonstrating numerous restorations produced by the CEREC. F0203 — "Computerized Restorative Dentistry" — will be available in February 2003. You may preorder by calling (800) 223-6569 or faxing to (801) 226-8637.

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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