Ask Dr. Christensen

I have been using the same composite resin for several years, and I have been satisfied with its service record in my practice. I am confused about the introduction of so many new composites on the market.

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 info@pccdental.com.

Question ...

I have been using the same composite resin for several years, and I have been satisfied with its service record in my practice. I am confused about the introduction of so many new composites on the market. Is it desirable to change from Herculite to a newer resin, or is it acceptable to stay with the older product?

Answer from Dr. Christensen ...

When I entered dentistry many years ago, tooth-colored resin restorations were primitive compared to the resin-based composites of today. They had high polymerization shrinkage, significant discoloration over time, high wear, and high expansion and contraction with temperature changes.

The evolution of resin restorations from these disagreeable characteristics has not been fast, and it was not until about 15 years ago that resin-based composites began to have characteristics that were more acceptable. Glass fillers were added to resin, and the particle size of the fillers in composites was reduced, significantly producing smooth finishing properties. Polymerization shrinkage was reduced but not eliminated, color stability problems were overcome, wear was reduced to slightly more than enamel, and silicon dioxide particles were added to the glass-filled resins to afford better characteristics. Microfill resins were produced that significantly reduced wear and retained very smooth surfaces, and many colors were produced to afford adequate but monotone tooth-color matching properties.

Since about 1985, further changes have been slower coming. In my opinion, the major changes in recent years have been observable but less significant than the earlier advancements. These changes include refinements in filler technology to reduce wear and aesthetic properties; production of both dentin and enamel colors instead of just monotranslucency-colors, which increasing the number and variety of colors; production of translucent colors, addition of bleach colors, and simplification of color matching. In other words, the aesthetic properties of the resins have been greatly improved, but the overall physical properties have not changed as much.

The resin material you mentioned, Herculite by Kerr, was one of the first to have refined properties. It deserved and obtained major use by dentists. It is a classic resin that has been used by many research groups to measure the acceptability of newer resins. *If you are satisfied with this resin, stay with it.* Newer resins, including the excellent Point 4 also from Kerr, offer some desirable characteristics over Herculite, but they are not profound enough to force you to change.

The Practical Clinical Course, "Esthetic Restorative Dentistry," is a two-day, intense, hands-on experience that allows you to try the new resin-based composites and compare them to the older brands, in addition to making veneers, class II resins, and tooth-colored inlays and onlays in a clinical simulation laboratory. Call PCC toll free at (800) 223-6569 for information on the next courses , which will be held September 27-28, 2004. Or, visit our Web site at www.pccdental.com

Question ...

Tooth-colored inlays and onlays seem to be popular. Are they providing adequate service, and if so, when should resin be used, and when should ceramic be used? Additionally, do all-ceramic crowns make better restorations?

Answer from Dr. Christensen ...

Tooth-colored inlays and onlays are receiving more emphasis in dental literature and on the lecture circuit. The materials are better than they were in the past. IPS Empress has proven itself over many years of use, and it is an excellent choice for ceramic inlay and onlays. It is well proven that onlays are stronger restorations than inlays irrespective of the material used. There are numerous ceramic materials comparable to IPS Empress, and I suggest that you ask your technician which type of pressed ceramic he or she uses. They are quite similar and provide excellent aesthetics.

I suggest using ceramic inlays or onlays when other previously placed more extensive restorations are made of ceramic, and I suggest using resin-based composite when other restorations in the mouth are class II composites. This suggestion provides similar materials that occlude with one another instead of ceramic wearing on less wear-resistant composite resin.

There are several excellent choices for resin tooth-colored inlays and onlays. Examples are Concept HP from Ivoclar, recently reintroduced, and well proven in the past, or belleGlass from Kerr, which is a laboratory form of Herculite, also well proven in service.

I suggest using conservative inlay and onlay restorations when teeth have intact facial and lingual enamel surfaces, and crown preparations would require cutting much of the tooth away. However, when the facial and/or lingual surfaces are defective, crowns are a better choice.

Because of the intense interest in all-ceramic restorations, our newest video is V19-99 — "Successful All-Ceramic Crowns and Fixed Prostheses." I also will be giving a hands-on course on Fixed Prosthodontics on August 30-31, 2004. For more information, contact PCC at (800) 226-6569, (801) 226-8637 fax, or visit our Web site at www.pccdental.com.

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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