Written by Louis Malcmacher, DDS Friday, 31 October 2003 19:00
The history of porcelain veneers is a very simple one. Thin wafers of porcelain were developed to be bonded to tooth structure in order to modify the shape, color, aesthetic scheme, and smile line of the human dentition. Porcelain has an exceptionally strong bond to composite resin through silanation, and thereby to tooth structure. Porcelain has natural translucence, and its ability to be manipulated in the laboratory to create a beautiful transition of colors mimics the polychromatic nature of natural tooth structure. Once properly bonded to enamel, it is very strong, color stable, and has the capacity to last for years. Tissue response to porcelain veneers has proven to be excellent when the proper contours are maintained.
For those of us old enough to remember when porcelain veneers first came into dentistry, laminate veneers were originally adopted to be very conservative treatment. It was a conservative treatment in comparison to the aggressive reduction of tooth structure needed for a porcelain-to-metal crown and conservative in relation to 2 to 3 years’ worth of full-mouth orthodontics. It gained in popularity because of its beauty and ability to conserve tooth structure while providing a very aesthetic result for the patient.
Somehow, the porcelain veneer technique has metamorphosed over the last 10 to 15 years and has changed into a procedure that promotes aggressive reduction in order to achieve a good result. I have personally spoken to many dental educators and some of the more popular dental lecturers in the field about this topic. None of them can quite put their finger on why this change is taking place, other than dentists felt that laboratories more often suggested to them to reduce the bulk of the teeth to give them more room to build the porcelain veneers. Over time, this became the norm. Now, most of the articles about porcelain veneers will routinely suggest very aggressive reduction. These preparations have gone past the porcelain veneer stage and are really 3/4 or 7/8 crown preparations.
Dental laboratory technicians many times suggested more reduction for porcelain veneer cases based on the limitations of the porcelains they used. These porcelains required a greater thickness in order to properly build in color and needed the bulk for strength. The strength referred to here is not the ultimate final strength of porcelain bonded to the tooth, but rather just enough strength to be handled by the dental laboratory technician and by the dentist prior to placement. Those of us who have done porcelain veneers for many years can remember a few cases where we received the porcelain veneers back from the laboratory in a padded case, opened them to try them on the model, and found that 1 or 2 of them were already broken just by being tossed around during the shipping process.
This history of porcelain veneers from conservative or no reduction to aggressive preparation boils down to a matter of different philosophies regarding what the dentist’s relationship should be to dental materials. Should the dental materials that you use dictate how you perform a certain procedure, or should the dental treatment procedure dictate the kind of materials that you’re going to use? My philosophy has always been that the procedure should dictate which dental materials you are going to use and not the other way around.
In other words, when I look at patients as candidates for porcelain veneers, they are either going to require no-preparation or minimal-preparation enameloplasty. If they do need more extensive preparation, then they are certainly a candidate for full crowns rather than 3/4 or 7/8 crowns. Doing a 3/4 crown requires a great deal of expertise as well as a great deal of time. There are many more margins on a 3/4 crown than on a conventional porcelain-to-metal or porcelain jacket crown prep, which makes not only the preparation more difficult but also the placement and especially the finishing much more difficult. It also makes the laboratory aspect much more challenging. If there is a need to reduce the facial of a tooth 0.5 mm or more and to break the interproximal contact, then it is easier and much more predictable for most dentists to go ahead and finish the lingual margin to a full crown, whether using all-ceramic or porcelain-to- metal.
The advantages of a minimal- or no-preparation porcelain veneer are obvious. There is no harm to the pulp and it will result in no postoperative sensitivity. With the enamel intact, the bond strength is the best it can possibly be. There is no question that the strength of our dentin bonding agents is much higher than it ever has been, but there still is no comparison to resin bonding to enamel. Enamel bonding has always been much more predictable, stronger, and more long-lasting.
Minimal preparation may be necessary, depending on a number of factors. These include but are not limited to teeth that are severely rotated, labially inclined, and severely discolored. Minimal preparation is reduction of the enamel, usually to a depth not exceeding 0.5 mm. Every effort is made to maintain the integrity of the enamel and not expose the underlying dentin.
With a no-preparation porcelain veneer technique, we don’t have to worry about managing the dentin. We don’t have to worry about managing the gingiva since we keep these veneers supragingival. Care has to be applied not to overcontour the cervical region of the tooth, which could create a trap for plaque and cause a detrimental tissue response. Imagine the ease with which an impression is taken. Another big advantage to this technique is that there is no temporization. Indeed, the hardest temporary to make and maintain is the porcelain veneer temporary. Then, once it is made, you have to decide how it is going to stay on the teeth, either with spot bonding or by locking into undercuts. We eliminate the need to do this since we have barely changed the patient’s appearance.
The following case study demonstrates a technique for rapid cementation for multiple nonpreparation veneers on a patient. In the past, it was believed that when doing multiple veneers, it was best to seat 2 veneers and take them all the way through the finished procedure before going ahead and seating the next group of veneers. The main disadvantage to that placement sequence was that if the first 2 veneers were off by just a little bit, then the remaining veneers would have difficulty seating. In many cases, by the time you wanted to place the final veneers, you couldn’t even get them onto the teeth. With the technique shown here, all the veneers are seated at the same time to ensure that they are properly placed and to view the overall aesthetics before finishing. They are all then cured and finished at the same time to maximize the placement, aesthetic potential, and artistry of the dentist. In this way, the overall view is assured before the final curing takes place.
The other big advantage is that your instruments for finishing and polishing can all be used at the same time, and the final result is much easier to achieve because you are able to see the entire picture at one time as opposed to sequential phases of 2 veneers each. This saves quite a bit of time when seating multiple veneers.
Important to the success of this technique is the elimination of excess resin cement before the final curing takes place. At this point, dentists should really take their time in removing as much excess cement as possible to ensure that the least amount of finishing is needed. The use of a wet resin brush or a sponge to remove the excess cement also ensures that the margin will still be properly sealed prior to curing. It is not recommended at this juncture to use floss to remove the interproximal excess cement because this can indeed change the position of the veneers prior to light-curing.
Cleaning up the interproximal areas after light-curing is fairly easy. If you have done a very good job using the wet brush technique, then you will be able to floss through most of the contacts easily, removing a little bit of resin flash that has accumulated there. If there is a little bit of resin cement between the teeth, then a Ceri-Saw (Den-Mat) can be used. This is a very thin saw that will help break the interproximal contact but keep the contact intact.
|Figure 1. Patient desires a more aesthetic appearance with no reduction of these virgin teeth.|
Figure 1 shows a patient who was interested in aesthetic improvement with porcelain veneers but had resisted them for many years due to being told that the process could only be achieved with aggressive reduction. The patient was assured that there would be no preparation for this case, and if results were not acceptable, the process was completely reversible and the patient could go back to the original aesthetic condition. Reversibility is only possible when the case requires no preparation. Certainly, with other porcelain veneer techniques that require reduction of the tooth structure, this promise cannot be made.
|Figure 2. Retracted view shows ample room for porcelain addition to close spaces.|
The key to success in a minimal- or no-preparation veneer case is the choice of porcelain. In this case, Cerinate porcelain (Den-Mat) was the choice to achieve the goals here. I prefer it for porcelain veneers as well as any porcelain application because of its high strength, even when it is made very thin. Veneers can be made 0.3 mm thin, and Cerinate porcelain can be handled easily without fear of breakage. This quality along with its natural beauty and translucence makes it the ideal material for these cases.Figure 2 shows the retracted preoperative condition of this patient. A polyvinylsiloxane impression was taken (First Impression, Den-Mat).
|Figure 3. Teeth have been etched and bonding agent is being applied.||Figure 4. Porcelain veneers measuring 0.4 mm thick are being cemented to the teeth.|
|Figure 5. Resin-dipped sponge is used to wipe away excess and seal the margins.||Figure 6. Plasma arc light is activated for 3
seconds from the buccal and 3 seconds from the lingual, per tooth.
The veneers were returned from the laboratory and were measured to be 0.4 mm thick, which is well within a patient’s ability to become accustomed to them. The teeth were etched with 35% phosphoric acid etch (3M ESPE). The teeth were bonded with a self-etching bonding agent (Tenure Unibond, Den-Mat, Figure 3). A resin cement (Ultrabond Plus, Den-Mat) was mixed and applied to the inside of the veneers. The veneers were applied to the teeth before removal of any of the cement was done (Figure 4). A sponge coated with unfilled resin (Biscover, BISCO) was used to remove the excess cement around the teeth before curing was done (Figure 5). The veneers were then cured with a plasma arc light (Virtuoso Sapphire, Den-Mat) for 3 seconds from the buccal and 3 seconds from the lingual (Figure 6).
|Figure 7. Any large excess is flicked off.||Figure 8. A dull 7901 twelve-fluted instrument is used to finish the margin.|
|Figure 9. A superfine flame-shaped diamond is used for final finishing.||Figure 10. Interproximals can be shaped with a very thin Ceri-Saw.|
|Figure 11. A fine interproximal strip is used to finish these areas.||Figure 12. Retracted view shows a nonpreparation porcelain veneer case.|
|Figure 13. A very pleased patient with a nice aesthetic result.|
A Shure 347 instrument (Rocky Mountain Dental) was used to remove gross excess cement after curing (Figure 7). The margins were then finished with a dull 7901 12-fluted carbide bur (SS White), then with a fine composite diamond finishing bur (Revelation Diamonds, SS White, Figures 8 and 9). Note that these margins are slightly supergingival and are finished right up to the tooth structure like any other feather-edged margin. It is also important to note that the veneers were seated together with no separating strips between the teeth. Separating strips have the ability to move the veneers and not allow them to seat completely. A Ceri-Saw (Den-Mat) is a very thin saw used for separating interproximal contacts while still maintaining the contact (Figure 10). A Ceri-Sander (Den-Mat, Figure 11), which is a diamond micro polishing strip, is then used on the interproximals to assure smooth conformity in this area. Figures 12 and 13 show the retracted and relaxed postoperative aesthetic result and a very pleased patient.
Many dentists have complained over the years that porcelain veneers are too hard to do. This is certainly not true when the right porcelains are used for this no-preparation or minimal-preparation porcelain veneer procedure. Porcelain veneers work best as a conservative treatment when little or no preparation of the teeth is needed. This makes the aesthetic treatment easier to do and eliminates complicated steps such as making temporaries and managing the subgingival tissues. It also eliminates any postoperative sensitivity issues because the enamel is left intact, ensuring the best bond possible. Porcelain veneers have a higher rate of acceptance and satisfaction, especially when little or no tooth structure has to be removed.
Dentistry performed by Dr. David Oulette, Santa Maria, Calif. Disclosure: Dr. Oulette receives and a honorarium from Den-Mat for select lectures.
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Disclosure: Dr. Malcmacher receives and a honorarium from Den-Mat for select lectures.
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