Ask Dr. Christensen

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 e-mail to [email protected].

Question:I have heard that Empress-type (pressed ceramic) veneers are better than fired ceramic veneers. Is that correct?Answer from Dr. ChristensenCeramic veneers have evolved through many stages over the past 15 years. When veneers were introduced, it was recommended that little or no tooth structure be removed; the resulting veneers were large, bulky, and only moderately realistic in appearance. Suggestions for greater tooth reduction have continued until current recommendations for veneer preparations resemble the facial one-half of a typical full-crown preparation. These preparations may be too deep. I suggest that veneer preparations be placed on enamel whenever possible to allow optimum retention to etched enamel and to reduce the chance of postoperative tooth sensitivity. When tooth preparations remove most of the enamel, leaving only a thin amount of enamel for optimum veneer retention, either Empress-type (pressed ceramic) or fired ceramic veneers provide comparable results. However, there are significant differences between the two types of veneers.

Color and translucence — With adequate laboratory support, either type of veneer may provide excellent results. The new Ivoclar d•sign porcelain has greatly improved the beauty of fired ceramic veneers.

Shape and contour — Fired ceramic veneers may be altered at the time of seating with minimal alteration in overall color. The altered surface can be smoothed with Dialite wheels (Brasseler) to simulate a glazed surface. Usually, alteration of pressed ceramic veneers removes the external color and requires further laboratory firing before cementation.

Fit — Pressed ceramic veneers usually fit better than fired ceramic veneers, since pressed ceramic veneers are made from a wax pattern and a "lost wax" mold. Fired ceramic veneers are made from either a refractory model or a platinum matrix on a die, neither of which provides an exact fit. However, the fit of either type is adequate considering the relative insolubility and beauty of resin cements.

Bond to etched enamel — Either type of veneer can have an excellent bond to etched enamel, since the surface of both types may be etched and roughened adequately for optimum retention to resin cement. If tooth preparations are made into dentin, neither type has optimum retention without roughening dentin and placing small irregularities and small bur holes in the dentin.

Laboratory effort — Both types of veneers require significant laboratory expertise.

Conclusions — With proper laboratory support, either type is excellent. I place both forms, but I slightly prefer fired ceramic because of the ease of alteration at seating and the lack of additional laboratory work after the alteration.

More on this subject from Dr. Christensen is available on the video V1584 — "Veneers, All Types." Call Practical Clinical Courses at (800) 223-6569 for information.

QuestionAre sealants now obsolete since air abrasion has become popular?Answer from Dr. ChristensenSome opinion leaders have stated that sealants are "dead" because of the growing popularity of air abrasion. The statement may be true when air abrasion becomes more popular. However, only a minority of practitioners use air abrasion. Although air abrasion is an excellent technique when used correctly, it is still very messy, relatively expensive, and the technique requires dentist involvement instead of staff responsibility. Therefore, air abrasion costs patients more than sealants. Average U.S. costs as reported by Atlanta Dental Consultants, Dental Insurance Today (Vol. 14 #2, 2000) are: Sealant $35 (D1351) and Class 1 Resin $94 (D2385).

However, the current technique used by many practitioners should be re-examined and changed. Most dentists do not clean the plaque off the occlusal tooth surfaces before placing resin sealant. The result is about one-third of the sealants fall off the teeth over a three-year period.

In my opinion, sealants are indicated when the practitioner does not see any caries present on the radiograph or does not receive a high reading on devices such as KaVo's DIAGNOdent, but the groove/fissure looks suspicious. In such cases, I suggest the following procedure:

1. Isolate the suspicious teeth.
2. Clean the plaque off the occlusal surfaces with an air slurry polisher. Examples are the Prophy Jet (Dentsply Professional), Cavi-jet 30 (Dentsply Professional), and the Microprophy (Danville Engineering). If plaque is not properly removed from occlusal surfaces, sealants cannot serve well. Prophy cups, brushes, or wheels do not remove plaque from occlusal grooves.
3. Neutralize the sodium bicarbonate residue left by the air slurry polisher by placing typical phosphoric acid liquid or gel in the grooves for a few seconds.
4. Wash and dry the teeth.
5. Acid-etch the teeth using phosphoric acid or gel for 15 seconds.
6. Wash and dry the teeth.
7. Omit Steps 8 and 9 if a low-viscosity sealant or flowable resin is to be used. Accomplish Steps 8 and 9 if a typical filled restorative resin is to be placed as the sealant.
8. Place any unfilled resin bonding agent to "wet" the etched tooth surface.
9. Blow the bond to a thin layer.
10. J. Place one of the following:

• Sealant
• Flowable resin
• A small amount of fully filled restorative resin pushed into the grooves with a fingertip lubricated with liquid bonding agent. If using these materials, insert Steps 8 and 9 above.

11. Adjust occlusion if required. Try to avoid this step since it requires the dentist.

If you have an air abrasion device, you may prefer to clean out the suspect grooves with air abrasion. However, this requires more time and costs the patient more money.

In my opinion, until and if air abrasion becomes more widely used, sealants, placed properly, are still useful, and the refined concept I have described is acceptable.

More on this subject from Dr. Christensen is available on the video V5178 — "Sealants — Effective & Long-Lasting." Call Practical Clinical Courses at (800) 223-6569 for 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.