Ask Dr. Christensen

Oct. 1, 2001
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

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 ...Which type of material should I use for repairing posterior crowns with gingival caries on the margins?Answer from Dr. Christensen ...In the past, most repairs of posterior crowns were accomplished with amalgam. However, use of amalgam introduced several elements into the tooth and the resultant eventuality of galvanic reaction, subsequent tarnish, and corrosion. Additionally, there is little or no cariostatic activity with amalgam.

Currently, there are several potential alternative materials for repair of posterior crowns:

Compomers — such as Dyract AP (Caulk) or F2000 (3M/ESPE) — are easy to place, and they release fluoride into the mouth. However, compomers require use of a bonding agent before their placement. The bonding agent seals the dentinal canals inside the tooth preparation. Obviously, if the dentinal canals are sealed with a bonding agent, the tooth preparation cannot receive fluoride from the compomer.

Resin-reinforced glass ionomers — such as Fuji II LC (GC America) or Vitremer Restorative Material (3M/ESPE) — release fluoride not only into the mouth, but into tooth structure. In cases where dental caries activity is high, resin-reinforced glass ionomer is the preferred material because of the cariostatic potential of the material.

Resin-reinforced glass ionomer is about 80 percent glass ionomer and about 20 percent resin. These products cure in three ways. You cure the restoration with light, which cures the portion of the resin accessible to the light, or about 20 percent of the mass. The resin also contains an initiator and catalyst to allow setting of the part of the material not accessible to light. How does the glass ionomer portion set? Glass ionomer sets by an acid-base reaction, which requires several hours to occur. When finishing resin-reinforced glass ionomer, cure the material and wait for a few minutes before trimming the restoration. This waiting time allows the glass ionomer to obtain minimal set before finishing.

Conventional glass ionomers — such as Fuji II or Ketac Fil — can be used for crown repair.

However, resin-reinforced glass ionomer is probably the best choice for crown repair in 2001, because of its ease of use, fluoride-release strength, and low solubility.

Question ...Since there are many people who are allergic to latex, should I eliminate it from my practice?Answer from Dr. Christensen ...It is approximated that as much as 10 percent of the adult population has allergies to latex. We use latex in numerous aspects of dentistry. At this time, I do not see a reason to eliminate all latex from the dental practice.

I recommend that a specific question about latex allergies be on your health questionnaire. This question should be specific: Are you allergic to latex? For those people who have latex allergies, I suggest that dental personnel know which products and materials contain latex and have some alternatives on hand.

The rubber dam technique is essential in many aspects of dentistry. Endodontic therapy accomplished without the use of a rubber dam is not considered acceptable today. What should dentists do to accommodate patients who have latex allergies and need the tooth isolation provided by a rubber dam? Nonlatex rubber dam is available and should be used in those cases. An example of nonlatex rubber dam is the Non-Latex Dental Dam from Coltene/Whaledent.

Using latex gloves when treating latex-allergic patients can cause challenges ranging from soft-tissue irritation to anaphylactic shock. Every office should have some nonlatex gloves available for use when treating these patients. Examples are Touch-n-Tuff (nitrile) by Audra, (800) 445-0170, and Vinyl Exam (vinyl) by Ammex, (800) 274-7354.

Numerous other latex objects are used in dentistry. Please analyze the use of latex in your practice and find substitutes for each of these items. It is predicted that latex allergies will increase.

More information related to this subject from Dr. Christensen is available on the videos V1180 — "Diagnostic Data Collection by Auxiliaries," V2479 — "Infection Control Step-by-Step," and V3534 — "Auxiliary Oriented Rubber Dam Placement." Call Practical Clinical Courses at (800) 223-6569 for more information.

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.

For a review of questions and answers from Dr. Christensen over the past few months, please visit

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