Ask Dr. Christensen

In this monthly feature, Dr. Gordon Christensen addresses the most frequently asked questions from Dental Economics® readers.

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 info@pccdental.com.

Question...

A few months ago, I attended a course on veneers at an “institute.” The instructor suggested that the technique I had been using for veneers was “out of date,” and that I should be cutting tooth preparations deeper than I had done in the past. The speaker stated that this deeper prep technique allowed for better color and easier laboratory construction of the veneers. I am confused because, now that I am using the deeper prep technique, patients are complaining of postoperative tooth sensitivity, and some of the veneers have debonded. What is the best technique for veneers today?

Answer from Dr. Christensen...

I often hear this question from dentists I meet on the lecture circuit. Some laboratories are influencing dentists to cut teeth deeply for veneers because it is easier for them to make the ceramic veneer material the prescribed correct color when the veneer is thick. Additionally, a currently promoted concept of occlusion suggests opening the vertical dimension of occlusion on a relatively routine basis, and placing extensive veneers to allow this vertical dimension opening. Such extensive rehabilitation with veneers requires deep tooth preparations and placement of thick ceramic veneers.

After placing thousands of veneers for more than 20 years, I have strong opinions on the subject, based on both clinical experience and research.

Ceramic veneers were invented to be thin ceramic laminates cemented over minimally prepared or, in some situations, even nonprepared enamel. For nearly 15 years, this concept dominated with success beyond the expectations of most dentists. When done properly, the veneers were more beautiful than crowns - in fact, in many cases, they were almost undetectable. These thin (.2 to .75 mm) veneers were so strong that they actually had to be cut away from the enamel if they had to be removed. Postoperative tooth sensitivity was almost nonexistent.

Along came the deeply cut preps and the thick veneer concept. The correct color was easier to produce. The labs were happier. Occlusion could be built up easier. However, many of the teeth were sensitive after cementation. The strength of the veneer/tooth combination bonded to dentin was extremely weak compared to the veneer/tooth combination with enamel bonded to veneers. Most experienced clinical dentists have noticed that veneers bonded to dentin are relatively easy to remove, if necessary. Dentin bonding becomes weaker with time, while enamel bonding does not! Many of the veneers even come off.

What is the answer?

Ceramic veneers bonded to enamel are definitely not out of date!

In fact, some of the treatment discussed in current dental magazines indicate overprepared veneer preps destined to fail based on the points I have described. In my opinion, if teeth need to be deeply prepared for all-ceramic restorations, veneers are not the correct choice.

Such teeth should be properly prepared for all-ceramic crowns. These crowns should be bonded with resin cement containing self-etching primer such as RelyX Unicem by 3M ESPE or Maxcem by Kerr. For the stronger all-ceramic crowns, resin-modified glass ionomer cements such as RelyX Luting Cement by 3M ESPE or FujiCEM by GC should be used. Such restorations provide high strength, low or no sensitivity, and predictable long-term service. Crowns are superior to veneers in deeply cut situations.

If you are faced with debonding of a veneer from a deeply cut preparation that has been cut in dentin, reseat it in the following manner:

Burn out the cement from the internal portion of the veneer (usually performed by a lab technician).

Etch the internal part of the veneer with hydrofluoric acid (usually done by a lab technician).

Cut all of the remaining resin cement off the tooth preparation without water spray to allow the old cement to be visible.

Using a 1/4-inch round bur, cut about six “potholes” on each side of the tooth, up and down the mesial and distal aspects of the tooth preparation. These holes should be about .75 mm deep and made to be undercut proximally for retention. On cementation, cement goes into the holes and the veneer is retained in place.

Silanate the veneer, place self-etching primer on the prep, and seat the veneer with resin cement.

In summary, veneers should be in enamel unless old restorations or tooth contour demand going into dentin. When significantly deeper preps are necessary, crowns are highly superior to veneers.

PCC has two popular veneer videos that demonstrate veneer-tooth preparation and step-by-step clinical placement of veneers, mostly in enamel. They are V1584, “Veneers - All Types,” and C902B, “Veneers for Lower Anterior Teeth.” For more information, contact Practical Clinical Courses at (800) 223-6569, or visit our Web site at www.pccdental.com.

Question...

I have used several chemicals for pulp-capping. Some have been successful and others have had frequent failures. Is there one best way to cap pulps that will be the most predictable?

Answer from Dr. Christensen...

The “best” method for pulp capping has long been a mystery. Perhaps the most important question is when to cap an exposed pulp. The following statement summarizes my experience on when to cap a pulp: The dentist should be placing a direct restoration on a permanent tooth in a child, youth, or young adult. There should be a small pulp exposure (up to .75 mm), and the restoration should be placed on a previously nonsymptomatic tooth that slowly bleeds normal-looking blood. If the patient is a mature adult, I suggest more caution.

Situations in which pulp-capping probably is not indicated are:

Teeth that were symptomatic before the pulp exposure, with the exception of teeth that had deep caries, and the patient complains of pain only on eating or drinking certain foods.

Teeth that do not bleed freely when the pulp is exposed.

Teeth that have dark-colored or pigmented blood on exposure.

Teeth that are to serve as an abutment for a fixed-partial denture. Accomplishing endodontics through a crown is not desirable.

When the pulp exposure is clearly a large carious exposure of 1 mm or more.

Assuming that the described desirable clinical characteristics are present, what material should be used to cap the pulp? Calcium hydroxide has been the historical choice of clinicians for pulp-capping. But about 15 years ago, several clinicians and researchers strongly condemned calcium hydroxide, and promoted the use of total-etch bonding agents for pulp-capping. When accomplished properly, the bonding agent concept worked well. Speakers and publications on the bonding agent concept were so convincing - and so negative about calcium hydroxide - that some clinicians felt reticent to continue using calcium hydroxide. In spite of the criticism, calcium hydroxide sales continued to be stable. The pendulum has swung in the opposite direction in recent years. Further research on calcium hydroxide has again supported its use for pulp-capping. There appears to be no legitimate reason to avoid calcium hydroxide if you prefer to use it, with Dycal® (Caulk) being the most well-known product. However, I prefer to use a material with less solubility and more strength than the calcium hydroxide preparations.

In the past five years, many clinicians, including myself, have used resin-modified glass ionomer (RMGI) as a pulp-capping material. The most popular products are the light-curing materials, Vitrebond (3M ESPE) and Fuji LINING LC (GC). RMGI materials are essentially self-etching primers heavily filled with glass ionomer particles. They set rapidly using a curing light, and they have significant strength. Using these materials is similar to using the successful bonding agent concept popular several years ago. The difference is that the RMGI products provide a significant thickness over the exposed pulp, allowing placement of subsequent restorative materials without again penetrating the exposed pulp.

After success over several years using the RMGI concept, it is my current choice for pulp- capping. But if you were to study the historical dental literature, you would find almost any dental material - and a few nondental materials - advocated for pulp-exposure capping. The most important consideration is when to cap the pulp.

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.

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