Ask Dr. Christensen

Oct. 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 ...

When considering placement of tooth-colored inlays and onlays, when should resin be selected for the restoration instead of ceramic?

Answer from Dr. Christensen ...

Tooth-colored inlays and onlays should be more popular than they are at the present time. These restorations are indicated when the facial and lingual surfaces of a tooth to be restored are not carious or otherwise compromised, and the intracoronal tooth structure is carious or has been removed as a result of previous restorations. As you know, this clinical situation occurs many times in the typical dental practice. Most dentists place crowns instead of informing the patient about the availability of tooth-colored inlays or onlays. Perhaps there is an excuse for this behavior. In the past, the materials that were available for these restorations were less than acceptable.

Most patients will accept the following concepts when they are educated about them:
• An onlay or inlay preserves the remaining tooth structure better than a crown.
• The remaining facial and lingual tooth structure are kind to the gingival tissues.
• As the gingival tissues undergo their incessant and predictable recession, the margins of the restorations will not be visible, as with a crown.

In other words, patients like inlays and onlays when their characteristics are explained thoroughly.

Currently, several popular tooth-colored materials have proven to be acceptable for inlay or onlay restorations. Among the acceptable ceramic materials are Empress from Ivoclar Vivadent Inc., and many other similar pressed-ceramic materials; Cerec restorative materials from Patterson (Sirona USA, Inc.), available in both ceramic or resin; and fired-ceramic materials, such as Cerinate from Den-Mat Corporation, or Fortress from Mirage/Chameleon Dental Products Inc.

Many good resin-based composite materials are available, including belleGlass from Kerr Lab, Concept HP from Ivoclar Vivadent Inc., Sinfony from 3M ESPE, Cerec Paradigm from Patterson (Sirona USA, Inc.), and numerous others.

It might seem desirable for a practitioner to select just one brand of restorative ceramic or polymer and use it for all situations. However, consider the following logical reasoning for selection of materials for tooth-colored inlays and onlays. If you are restoring an upper premolar with an inlay or onlay and the lower opposing teeth have ceramic restorations on them (such as porcelain-fused-to metal crowns), doesn't it seem logical to place a ceramic inlay or onlay on the upper premolar? If ceramic is used for the inlay or onlay, the wear characteristics of the new restoration and the previously placed ceramic restoration on the opposing teeth are nearly equal. Over a period of time, the restored teeth on each opposing arch wear at similar rates.

Using similar judgment, when an upper posterior tooth to be restored with an inlay or onlay opposes a gold alloy restoration, or teeth that have been restored with numerous Class II, resin-based composite restorations, doesn't it seem logical to restore the inlay or onlay with indirect resin-based composite? Such wear similarity of opposing restorations affords optimum lack of wear of the opposing gold alloy or composite restorations, and minimal wear of the new premolar resin-based composite inlay or onlay.

For a definitive close-up clinical demonstration, please see our newest edition of V1502, "Tooth-Colored Inlays and Onlays," 4th Edition. Call Practical Clinical Courses at (800) 223-6569 or visit us online at

Question ...

I was told recently by the practitioner to whom I refer patients for surgical placement of implants that "placing a three-unit bridge instead of an implant and a crown is dental malpractice." Is that statement correct, or is he exaggerating?

Answer from Dr. Christensen ...

Over the past decade, implant dentistry has evolved to a highly predictable clinical procedure. Those practitioners involved with implants on a routine basis, including myself, would prefer an implant restored with an abutment and a crown rather than a three-unit fixed partial denture. However, three-unit fixed prostheses have been used successfully for many years with predictability, and many mature dentists still feel more comfortable using fixed prostheses instead of an implant and a crown. As time passes and these older dentists retire and the new generation of dentists replaces them, I predict that use of implants instead of fixed prostheses will become the standard of care.

Additionally, there are situations when replacing a single tooth where a fixed prosthesis may be less expensive than an implant and a crown, and, therefore, more desirable to patients. An example of such a situation is when the potential prosthesis abutments are broken down or heavily restored, and they require crown restorations. In cases where crowns are required on the potential abutment teeth, placement of an implant and a crown instead of a simple three-unit fixed prosthesis costs the patient hundreds of dollars more. Also, some third-party payment companies will pay for three-unit fixed prostheses, but they will not pay for implants.

In cases where conventional fixed or removable prosthodontic dentistry can compete with implants supporting prostheses, patients should be advised of all of the reasons for and against each of the alternatives.

In my opinion, the surgical dentist who advised you that placing three-unit bridges instead of a bridge is dental malpractice is considerably ahead of state-of-the-art thinking in the profession. A well-done, three-unit fixed prosthesis is still an excellent and potentially long-lasting restoration.

PCC's new 60-minute video, V2300, "Making Decisions About Successful Use of Implants," is a must for both surgical and restorative dentists. In my opinion, sometimes implants are not indicated. However, there are more times when treatment-planning for implants is neglected as opposed to over-treatment planned. Let this video guide your decision about when to use implants. Call PCC at (800) 223-6569 or visit our Web site at for further information or to order this highly useful video.

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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