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Conservative Esthetic Dentistry ...What’s the controversy?

Sept. 1, 2006
More than ever before, we live in a world where people are interested in makeovers to enhance their physical appearance.
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More than ever before, we live in a world where people are interested in makeovers to enhance their physical appearance. Anytime you turn on the television and flip through the channels, you can find programs that feature people receiving cosmetic improvements, including their smiles.

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This presents a golden opportunity for dentists to increase the esthetic portion of their practices by offering procedures such as tooth whitening and porcelain veneers. With increased patient demand, many dentists are searching for the best way to create excellent, long-term esthetic results.

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For more than 25 years, dentists have been placing porcelain veneers using various materials and techniques. In the early days, the porcelain used to fabricate veneers was the same porcelain used to fuse to metal for PFMs. By itself, the porcelain was fragile in a thin layer. Therefore, dental labs had to create thicker veneers that were strong enough to avoid fracturing during fabrication, or chips and fractures from occlusal and functional stresses once bonded to the teeth. To make adequate room for these early veneers, which were approximately 1 mm to 1.5 mm thick, aggressive reduction of the facial and incisal enamel was taught. In most cases, the remaining surface of the teeth was exposed dentin. This often resulted in a compromised ability to create a strong bond and physical support for the veneers. Ultimately, debonding of the veneers resulted because of the exposure of the reduced tooth structure.

Worn dentition
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Historically, we have seen the development of many new porcelains. In addition to the original stacked porcelains, pressed porcelains are available. With pressed porcelains, the laboratory can create restorations that, with some products, are somewhat stronger than the stacked porcelains. They usually have better-adapted margins as well. However, in most cases, pressed porcelain veneers are thicker than their stacked counterparts. This means that more aggressive tooth preparation is required for most pressed porcelains.

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Over the years, certain pressed porcelains have become very popular with dental laboratories across the United States for veneers fabrication. To allow room for these thicker restorations, the labs instructed dentists to perform aggressive veneer preparations, with removal of up to 1.5 mm to 2 mm of enamel and dentin. In turn, dentists got used to the idea of aggressive preparations, with respected clinicians and lecturers teaching the same technique.

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Most dentists have never been overly concerned with these aggressive veneer preparations, often rationalizing that without a good amount of facial reduction, the veneers will be over-contoured, resulting in poor esthetics and the possibility of periodontal problems. Having lectured on the subject of esthetic dentistry for more than 23 years, I have spoken with thousands of dentists. I have observed that dentists find it very natural to do aggressive tooth preparations.

Old PFMs
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From the moment we enter dental school, we are taught to pick up a handpiece and prep teeth. We do this to remove decay, prepare a tooth for a restoration (direct or indirect), adjust occlusion, and many other dental procedures. Dentists have accepted that the invasive removal of often healthy tooth structure is just part of the process.

As pressed porcelains were developed over the years, the requirement to reduce more tooth structure only increased. Pressed porcelain veneers are waxed up, invested, burned out of the investment, and then porcelain - instead of metal - is pressed into the investment. The veneer is then recovered, finished, and characterized. Due to the physical characteristics, other porcelains on the market are not as substantially strong. This could pose an increased risk of fracture during the process of fabrication or occlusal contact after placement.

A new conservative option

Cerinate porcelain is a micro-pressed feldspathic porcelain, which was specifically developed for a minimal- or no-preparation technique for veneers. Because of its exceptional strength even while pressed thin, Cerinate porcelain veneers can be made ultra thin while remaining resilient. Owing to their minimal thickness, just about all veneer cases can be accomplished with no or minimal tooth reduction. When tooth reduction is required, it is largely limited to cosmetic contouring without the necessity for local anesthesia. Many dentists who have been aware of the intense strength of minimal- or no-preparation veneer techniques have been placing these ultra-thin veneers for years with little or no failure and no adverse gingival effects.

Rotated teeth
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There is some controversy regarding the placement of ceramic veneers after minimal tooth reduction. When the veneers are 0.5 mm or less in thickness and the margins are properly finished to a seamless feather edge, the final restorations can be highly esthetic, when properly contoured, and significantly comfortable for the patient.

As noted, there are many situations where tooth reduction is necessary to develop a properly contoured and esthetic result. When veneers are very thin, however, tooth modifications will be extremely conservative and, in most cases, preparation will be limited to the enamel layer. When no sensitive tooth structure is removed, anesthesia is no longer required, and there is no need for provisional restorations. This saves much chair time and eliminates all patient discomfort.

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Minimal- or no-prep veneers have proven successful in several university-based studies. A 14-year study by Yu, et al. (JDRes.1998, 77, 2583) compared the effect on gingival tissue of prep vs. non-prep LUMINEERS and found that both had no adverse effect on the gingiva, and both types were esthetically acceptable during the the study. What it comes down to is proper case selection. Dentists must be educated to recognize when teeth can be esthetically veneered with minimal prep, versus a requirement for aggressive tooth reduction. By avoiding the removal of tooth structure, procedural or postoperative sensitivity is eliminated. It is critical that the dentist attend a seminar - preferably one that includes a hands-on component - where he or she will learn proper techniques in all phases of the veneer procedure.

Adolescent & pre-adolescent teeth
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It is essential to submit accurate study models and include a detailed prescription form when submitting a minimal- or no-prep veneer case. Some cases may require a minimal degree of tooth modification (cosmetic contouring). When reduction is necessary, the lab will duplicate your models, marking one to demonstrate the location and amount of tooth structure to be removed, allowing both the doctor and patient to view the final results. This ensures the esthetic and functional success for a long-lasting smile makeover. If, for some reason, any of the veneers look too “bulky” to the patient, further tooth reduction is always an option. Therefore, when a dentist sends study models to the lab, he or she will be informed whether the case requires no preparation, moderate preparation, or aggressive tooth reduction for successful completion of the case.

In addition to the inherent strength of minimal- or no-prep veneers, another reason for their long-term success - even in high-stress areas - is believed to be the bonding agent and luting system used to place them. Check with the individual porcelain manufacturer for its recommendations.

Five major success or failure factors have always been:Case selection and proper treatment planningChoice of laboratory and the porcelain it is using to fabricate the veneersClinical expertise of the dentist and proper clinical placement and finishing techniqueChoice of bonding agentChoice of porcelain luting systemThe controversy over thick vs. thin veneers and conservative vs. aggressive tooth reduction will likely continue for awhile, but most patients prefer a smile makeover without the destruction of healthy tooth structure or the pain involved. Without this conservative option, most people will forego veneers rather than succumb to a permanent loss of their dental anatomy, requiring ever more dental work for the rest of their lives. With years of proven clinical success, the concept of ultra-thin, ultra-strong porcelain veneers is an important option for dental patients.
Dr. Steven Weinberg is a clinical assistant professor in the Department of Restorative Dentistry at the University of Pennsylvania School of Dental Medicine. He has served on the faculties of four other dental schools’ postgraduate esthetic programs. Dr. Weinberg opened his private practice in New Jersey in 1978 with an emphasis on esthetic and restorative dentistry. He has been lecturing nationally and internationally for more than 22 years. Reach him at (856) 305-0525 or e-mail [email protected].

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