April 1, 2013
by Gregory Brambilla, DDS
Nice smile, white teeth, youth and wellness: these are the main needs of people in society nowadays.
The need for beauty has been studied for years and researchers found that there is a strong relation between beauty and self- confidence, ending with better life styles.1-3
This relation has been studied mainly in relation to cosmetic surgery, but the smile has a predominant role in a person’s appearance: “A smile has a tremendous impact on perceptions of one’s attractiveness and one’s personality.”4
The smile is related both to the attractiveness to the opposite sex and to the perception of being intelligent, successful, friendly, happy, sensitive, kind.
These findings may explain why many patients go to see a dentist for esthetics, even more than for illness.
The past 20 years have been the years of veneers, with nice and beautiful smiles going out from dental practices: dentistry has followed the requests of patients.
Still nowadays, thanks to the clear consensus that veneers are successful5, too many patients are treated with a procedure that, sometimes, could be much less invasive and aggressive.
The technique of porcelain laminate veneers found its success in the “easy” procedure of the so called “traditional preparation” with the great advantage of having the whole preparation on enamel and the tooth preparation is quick and leaves the contacts. After this “first” design, the goal of having the best esthetics ever possible pushed practitioners to hide all the margins with the so called “full veneer preparation”: in this case, the junction between tooth and veneer is hidden palatally thanks to the interdental preparation.
All this is practically correct and the scientific literature explains all the pros and cons of tooth preparations, but is it ethically correct?
With the performing materials that the dentists can use nowadays, isn’t it possible to achieve good esthetic results following the principles of “minimal invasiveness” or even “no invasiveness”?
NO-PREP VENEERS PRINCIPLE
Many applications for ceramic veneers are related only to esthetics, such as diastema closures, changing forms, restoring fractured or eroded teeth.
The traditional approach for these situations is to prepare teeth in order to give enough space for the ceramist to do the porcelain veneer, even with interdental preparation in case of diastemas.
Edelhoff and Sorensen6 demonstrated that with a preparation for veneers, teeth are reduced from 16.6% for a buccal preparation to 30.2% for buccal + interproximal + incisal preparation!
For cases where the color is correct and there is only the need to change the form, tooth reduction can be avoided.
The principle is not to harm the sound tissues of teeth but only to bond on tooth surface. The result will be just to add some material to the natural tooth with a “non-invasive technique”.
Adhesion is universally accepted as being reliable on tooth structures, particularly on enamel. This knowledge brings to the consideration that the more enamel is left the better it is, at least for adhesion.
Furthermore, the studies by P. Magne report that whenever enamel is worn and/or removed from tooth surfaces, the tooth flexibility increases and the stress strength decreases.
P. Magne has also demonstrated that restoring a tooth with a veneer can restore the original stress strength of that tooth7: by that, why not reinforce a tooth just adding ceramic?
The patient, an 18-year-old male, asks for a diastema closure (Fig 1.).
Traditionally, the diastema closure is an indication for veneers, in particular if a patient doesn’t accept an orthodontic treatment.
Following what literature indicates, the preparation design is somehow aggressive if we consider that the need of a diastema closure is to “add material” in order to fill an empty space and not to “remove material”.
Many authors agree that esthetics can be achieved if the clinician leaves room to the ceramist to create illusion of space closure and create new “correct anatomic proportion”: this can be done with a “required” preparation to the lingual.5
Suggestions found in the literature start from a tooth reduction of 1mm toward the lingual, going to the interproximal line-angle, to the linguo-proximal line angle, ending at a relation between the depth of preparation and the space to be closed.
Even more, another suggestion is to go deep in the gingival sulcus to have a natural emergence profile and a nice, natural-looking papilla.8
This leads to the consideration that, to achieve a natural mesial straight contour, the recommendation is to have an interproximal margin that goes 1mm subgingivally.5
Going back to the paper of Edelhoff and Sorensen,6 these types of preparation are pretty much aggressive.
If then we consider the age of a patient, and that there is a time limit of the duration of a restoration, the suggested designs of tooth preparation become too expensive in terms of biologic value.9
The first step for the solution of the case has been a pre-visualization with a direct composite mock-up to evaluate the esthetic outcome of the diastema closure (Fig. 2).
Once the patient has evaluated and accepted the suggested result, alginate impressions are taken to evaluate on the stone models if it will be possible to close the diastemas without tooth reduction. In this step, the clinician, together with the ceramist, have considered the natural undercuts of teeth and if there is a way of insertion for the additional veneers. If there is an axis that allows to place the veneers, then the decision is to go for no-prep veneers: a second try-in of the esthetic result is made to see if there are any corrections to be done to the wax-up and the final impressions are taken (Figs. 3 & 4).
On delivery, the fit of the feldspathic porcelain veneers (Creation, Klema; Meiningen, Austria) are checked for form, contact points, and color (Figs. 5 & 6).
For the first try-in, only water is used: this allows us to check if the color is correct and the water is fluid enough to flow under the thin veneers without having any points of pressure that could break the ceramic at this stage.
Ceramics are treated with hydrofluoric acid at 9.7% for 90 seconds, cleaned with phosphoric acid 37% for two minutes and then with an ultrasonic bath for five minutes in alcohol. After this, a silane agent is applied to the surface. This treatment perfectly cleans the etched ceramic surface and achieves a mean micro-tensile bond strength of 46.3 MPa10.
With the rubber dam in place and after checking that the isolation is correct, the teeth are treated for adhesion by sandblasting with 50 μ aluminum-oxide powder (Fig. 8) and application of phosphoric acid on enamel for 15 seconds, rinsing with tap water for 15 seconds.
The use of the rubber dam gives a delicate tissue displacement that allows us to place the margin of the additional veneers into the gingival sulcus: the final result will be a natural emergence profile even without an interproximal tooth preparation, and the “natural straight contact” between the central incisors is achieved.
The veneers have been cemented with a direct composite material (Enamel Plus HRi) pre-heated to 50°C to give both a lower viscosity of the material (which helps in precise and delicate positioning of the veneer and the flow of excesses) and a better ratio of monomer conversion (Fig. 9).12,13 Excesses are cleaned with a scalpel and then polished with rubber burs first, then with a goat wheel and diamond pastes (3 and 1 microns), and finally with a felt-wheel and an aluminum-oxide paste.
The polishing is still done with the rubber dam in pl
ace: this allows an easier and faster procedure protecting the soft tissues from the possible harmful action of burs or wheels.
Final polishing was performed twice: first at the time of delivery (Fig. 10), then after one week.14 Function is controlled, as veneers act just like teeth and have to play an active role in the incisal guidance.
DISCUSSION AND CONCLUSIONS
Esthetic problems can affect self-esteem and the social life of a person. The diastema is one of the esthetic handicaps that can require prosthetic correction.
The “classic” approach to close a diastema is the use of full-prep veneers: this kind of treatment requires a tooth reduction that can sometimes be aggressive, in particular if referred for young patients.
This article presents an alternative approach that tends to the “non-invasive” and the maximum respect of the biologic value of a patient.
The advantages of the additional veneers (or non-prep veneers) is that teeth are not reduced, the adhesion is performed fully on enamel (if teeth are virgin and there is no dentin exposed) giving good warranties of a result that will last for a long time.
The acceptance of patients is even higher vs veneers, as the dentist wil not “drill” their teeth and there will not be the need of anesthesia.
The disadvantage is that this is not an easy procedure and requires strong attention both from the ceramist for the lab procedures (in some spots the veneers can be 0.1 mm thick!) and from the clinician during try-in and cementation.
Another disadvantage of this method is a lack of scientific support: we can refer almost only to case reports, but all the principles on adhesion or veneers or ceramics can be used for this procedure.
Finally, esthetics is not so “perfect” as full-prep veneers as the margins are not hidden to the eye and could be seen, but mainly this is true on a macro view picture and not on normal social life (Fig. 11).
As a conclusion, considering pros and cons, this procedure should be preferred to others more aggressive: even in case of failure or fracture, the clinician will always have the option to again do the same treatment as the first time or to choose a full-prep veneer. OH
Dr Gregory Brambilla is in private practice in Milano, Italy. Info@gregorybrambilla.com
The author thanks the ceramist Mr. Roberto Brambilla for the ceramic work. The author declares not to have any commercial interest for the brands and/or the materials cited in this article.
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