By Edilia Glenski, DMD
Porcelain veneers are being used with success by an ever-increasing number of dentists. Due to better communication between our profession and the media, the public's awareness of the benefits of this simple cosmetic procedure has created a demand for more dentists who can provide this service.
There are four keys to success with indirect veneers — patient selection, preparation of the tooth, choice of laboratory, and cementation technique. Notice that I did not mention choice of material. The reason for that is simple — the choice of porcelain material is best left up to the laboratory. This may sound sacrilegious to some, but if you have a good lab, the technician will know what to use for best results on that particular case (based on the tooth number, the prep, the occlusion, patient's habits (bruxism, etc.) and other factors.)
There are patients who have unrealistic expectations about cosmetic dentistry, or emotional problems that cause them to be dissatisfied with excellent results. Before you agree to do indirect veneers, carefully interview the patient so that you do not treat someone who will not fully benefit from this procedure.
Around 20 years ago, I did my first set of indirect veneers. I confess that I did so with great trepidation as my experience at the time had been with direct veneers done over unprepped enamel. Minimal reduction was favored at the time and I kept the prep in enamel, did not wrap the incisal edge, and stopped facial of the interproximal contact. I probably removed less than .25 mm of enamel, yet the veneer needed to be at least .5 mm thick, giving the patient a rather "bucky" appearance and "Chicklety" contours. Through this experience, I learned that an overly conservative prep for the sake of saving tooth structure defeats the purpose of doing veneers in the first place.
Preps can successfully be kept minimal when closing diastemas in a case of microdontia, where the teeth are evenly spaced and only slight rotations are present. Unfortunately, most patients who seek cosmetic services have bigger problems they are trying to solve.
Dentists are frequently faced with a crowed, rotated, chipped, discolored, and previously restored dentition that the patient wants transformed into the perfect white smile advertised on TV. In these situations, the preps need to be far more aggressive and can sometimes look more like porcelain crowns than veneers.
Tissue health and prevention of caries are considerations in prep design as well.
Choosing a lab
Given that you have prepped your teeth well and have good records, your first hurdle is over. Now, the partnership you form with a good laboratory will make or break your reputation as a cosmetic dentist.
To find a good lab, I prefer to start my search locally. Ask other dentists whose work you admire for recommendations. Go visit the lab and speak to the ceramist personally. Find out what he or she needs from you in order to do a good job since each ceramist has his or her own preferences for types of records. Look at the work that is currently on the bench, not pre-made samples.
Talk to several technicians from different labs. Discuss the different types of materials they use and which ones they prefer. Tell them what you're looking for, what kind of contacts you like, what you've experienced with different materials in the past, discuss prep design, etc.
Here's the most important thing — can you communicate effectively with the ceramist and can he or she produce the desired result? Keep in mind that it is the dentist's job to properly prepare the teeth and take good, accurate records. Without that, even the best lab can only provide mediocre results.
For predictable success, one must replace any old restorations. Veneer margins should not be placed on an old resin or resin margin as that area will be predisposed to recurrent caries and you risk premature failure of the indirect veneer.
Interproximal margins should be on the tooth's lingual surface and should clear the contact point. Incisal reduction should be 1 mm (if the tooth is to be lengthened) to 1.5 mm (if the existing incisal edge position is not to be changed). Facial reduction is to be done in three planes (incisal, body, and cervical) to a depth of .5 mm, or more in areas where the tooth is excessively protrusive.
Cervical margins should be placed at or slightly (<1 mm) below the edge of the free gingiva.
All internal and external angles should be rounded, not sharp or square, to prevent stress in the porcelain.
Don't skimp on impression material. Take full arch impressions and a good bite registration that indicates the horizontal component of the smile. Supply the lab with pre-op models and photographs that include your chosen shade tab and, if possible, take articulator records.
Temporizing the prepped teeth is the subject of another article. Suffice it to say that most patients expect temporaries, so be sure to do them.
Thanks to free enterprise, competition has generated sufficient research on adhesives. Therefore, most cements currently on the market do a fine job. Similarly, your choice of bonding agent does not need to be any different than what you use for direct resin cases.
The critical issue here is a dry field. Gingival tissue MUST be healthy prior to cementation. In fact, preparation for veneers should not be started until gingival health has been achieved. However, while the patient is in temporaries, he or she may slack off on home care and present with boggy tissue that easily bleeds.
To avoid this cementation nightmare, in addition to oral hygiene instructions, I send patients home with a bottle of a chlorhexidine mouthwash (Peridex™) and a prescription for a four-week supply of Periostat™ (Doxycycline Hyclate 20 mg). Used as directed, this protocol keeps tissues healthy and prevents a watery gingival exudate from interfering with adhesion.
Editor's Note: This is the second of a yearlong series of articles from the American Academy of Cosmetic Dentistry (AACD). The AACD and Dental Equipment & Materials are working together throughout 2004 to bring you articles that will help you in your practice.
Dr. Edilia Glenski graduated from the University of Florida College of Dentistry in 1980. After graduation she served in the U.S. Navy until 1983 and started her own practice in 1984. Dr. Glenski earned her Accredited status from the American Academy of Cosmetic Dentistry in 1996 and currently practices general and cosmetic dentistry in Palm Harbor, Fla. She has lectured and taught hands-on classes internationally and has consulted dentists on management and technical skills. Dr. Glenski can best be reached by email at DrEdilia@GreatSmilePro.com.