Aesthetics

Predictable Pressed Ceramic Anterior Restorations: Clinical Observations

Dentistry Today April 1, 20027 Mins read4.1k Views

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The purpose of this article is to help the clinician categorize and differentiate anterior cases with potential problems from those that are more routine, by presenting guidelines for the predictable and profitable use of pressable ceramics. When complications are foreseen before the case is presented, treatment can be economically planned.

BACKGROUND: PRESSABLE CERAMICS
Pressed ceramic restorations are an invaluable part of an aesthetic practice. Each restorative material has its own advantages. These are some of the advantages the author attributes to pressed ceramic restorations:

Restorations made from pressed ceramics have better margins and are much stronger than feldspathic porcelain restorations.
Compared with porcelain-fused-to-gold crowns or ceramic crowns with milled cores, pressed ceramic crowns have greater translucency and generally blend better with adjacent teeth.
Uncomplicated cases are easy for the laboratory to restore.
Pressed ceramic restorations are fabricated by a sophisticated lost wax technique. A pattern is waxed onto a die, which is then invested and burned out. Small ceramic discs called ingots are melted to a honey-like consistency and then pressed into that pattern (Figure 1).


Figure 1. Five different shade 110 ceramic ingots.	Figure 2. Note opaque PFM crown with exposed margin.

Figure 3. A single Empress I crown greatly improves the patient’s smile.	Figure 4. Tooth No. 8 is darker than the adjacent teeth.

Figure 5. Note the volume of porcelain that will be required.	Figure 6. Completed restoration.

Figure 7. Pre-op.	Figure 8. Note the prep size and the volume of porcelain that will be required.

Figure 9. Completed restoration.	Figure 10. Two discolored composites.

The dentist selects the desired tooth shade and the shade of the prepared tooth, the “stump shade.” Using this information, the lab makes a die from the appropriately colored stump material and selects the opacity level of the ingot that will produce the desired hue and intensity in the restoration. The ceramic ingots not only come in different shades, but also in different levels of opacity. The selection of the opacity of the ingot used to fabricate the restoration is equally important as the shade selection. The opacity level is generally selected by the lab technician.

The most commonly used pressed ceramic restorations are fabricated from full-contour wax-ups and then stained after pressing. More complicated cases require a higher strength core to be pressed first, then porcelain is added to the core in a traditional layering technique as is used in porcelain-fused-to-gold restorations. These cores offer varying levels of opacity to block color variations or conceal tooth size discrepancies.

IPS Empress (Ivoclar Vivadent) is the author’s choice for pressed ceramic restorations. The principles that apply to the Empress system can be applied to other ceramic systems.

Generally, layered pressed ceramics are more opaque than full-contoured pressed ceramics. Thus, full-contoured pressed restorations can frequently produce a more natural-appearing restoration because of greater translucency when significant color alteration is not required. In addition, with full-contoured pressed ceramics, the laboratory technician can produce a very aesthetic restoration with less effort than with alternative materials.

The skill level and effort required by the laboratory technician to produce a layered all-ceramic restoration is much higher than with the more translucent full-contour restorations.

TECHNIQUE TIPS
The most common variables that affect the aesthetic outcome of proposed restorations include the color and the volume of remaining tooth structure following preparation and the position of the gingival margin relative to the lip and adjacent teeth.

In preparing incisors, the objective is to have as much dentin remaining in the prepared tooth as possible and for the preps of mirror image teeth to be the same size.

The preparation of teeth for veneers with pressed ceramic materials requires more tooth reduction than does a feldspathic porcelain restoration. (If possible, some enamel should remain on the facial aspect of the tooth.) The molten ceramic must have adequate thickness to flow (1 mm is the manufacturer’s recommendation), and will not reproduce sharp angles. Preparations must have adequate reduction, and all corners and angles should be rounded.

Pressed ceramic full-crown preparations require less facial reduction, but more lingual preparation than a porcelain-fused-to-gold crown. Thus, with pressed ceramic that can be bonded to the teeth, a modified 3/4 crown is frequently the restoration of choice as opposed to a full crown in the anterior region. This conserves tooth structure and allows the initial lingual contact to be on enamel.

COLOR MATCHING AND COMPLICATIONS
You are essentially replacing the enamel with a material that refracts the reflected dentin color and draws color from the adjacent teeth as light passes through the incisal and interproximal areas, which are translucent and opalescent. This creates the illusion of a natural tooth when the laboratory technician has matched the surface texture and contour of the adjacent teeth.

If you have adequate dentin of the right color, the most transparent ingots look more natural. (The most transparent ceramic ingots used in dentistry are about 25% opaque.) However, when an excessive amount of tooth structure is missing, the crown appears gray with a translucent restoration. Using a more opaque core and then adding a more translucent porcelain to the surface solves this problem. This is illustrated in the following examples.

RESTORING SINGLE CENTRAL INCISORS IS UNPREDICTABLE
In the first case presented, when this old PFM crown was removed there was an adequate amount of tooth structure remaining, and the dentin color was good. An Empress I crown was fabricated from a translucent, 25% opacified ingot, and an ideal shade match was achieved. However, prior to removing the old crown there was no way to predict the difficulty of this restoration (Figures 2 and 3).


Figure 11. Two 50% opacified Empress veneers.	Figure 12. Diastema with a PFM crown.

Figure 13. Two Empress II crowns.	Figure 14. Six chipped and stained composites.

Figure 15. Six Empress I veneers.	Figure 16. Discolored composites with an angled incisal plane.

Figure 17. Six teeth prepared for modified 3/4 crowns.	Figure 18. Patient’s smile with six Empress II 3/4 crowns.

Figure 19. Often peg lateral incisors require minimal preparation.	Figure 20. Empress I veneer at day of insertion.

In the next example, crowning a single central incisor, which was slightly darker because of a degenerated pulp, seemed ideal for a pressed ceramic crown, as shown in Figure 4. The tooth was slightly rotated, thus requiring more tooth structure to be removed from the distal than in an ideal preparation, as shown in Figure 5. A layered, 25% opacified crown was fabricated, but discarded at try-in as it was too translucent and thus low in value. A second crown using a more opaque, 50% opacified core with glass-ceramic layering was seated as the final restoration, as shown in Figure 6.

If a crown is too low in value it must be remade. Thus, the lab will generally select an ingot that is slightly too opaque, but will produce a satisfactory restoration. If you want the most aesthetic restoration possible for a tooth, more than one crown may be necessary, which translates into an increased lab cost.

SIZE MATTERS!
Adjacent teeth may be identical in color, but one tooth can be shorter because of a traumatic fracture. One tooth may have undergone more reduction to correct misalignment, or from a previous crown. Often, these teeth will look totally different when restored with Empress crowns pressed from the same ingot. This is because of the translucency and opalescence of Empress I. The beauty of this porcelain is that light passes through it. However, if there is not enough dentin to reflect some light back, that translucency which creates the illusion of a healthy vital tooth when present on the incisal and interproximal causes the entire crown to appear gray.

As an example, replacing the all-ceramic crown shown in Figures 7 through 9, which fractured after root canal therapy, was a challenge as there was very little tooth structure remaining and the exact material used to restore the adjacent crown was unknown. A shade 110, 50% opacified ingot was selected for the core material. Often, a crown made from this more opaque ingot will appear brighter than the adjacent tooth. This crown was slightly too bright and was returned to the lab where color modifications were made before the crown was seated.

I tell patients that if they want a perfect match they should restore both central incisors. If they just wish to restore one tooth they should expect to have more than one crown made (remakes that will probably be necessary to achieve desired aesthetics), and the fee for this tooth is just slightly less than doing both teeth. That said, I do restore many single central incisors successfully, but often not profitably.

PREDICTABLE PROCEDURES ARE PROFITABLE

Following are some predictable case examples.

Closing spaces for multiple mirror image teeth is very predictable provided the prepared teeth are the same color. Whether you are doing 2, 4, 6, 8, or 10 teeth, you control the size and shape of the preparations even when old crowns are being replaced. The crowns are all made from the same ceramic ingots, so they will have similar color, and reflective and translucent areas for the paired teeth will be very similar. The lab, with your instructions, controls shape, contours, and surface texture.

As shown in Figures 10 and 11, replacing the discolored composite on these two central incisors involved restoring adjacent teeth, which were different in color when the composite was removed. Empress I, shade 110, was used; an ingot that is 50% opacified was selected, and the color differences were concealed.

The case shown in Figures 12 and 13 illustrates two crowns using 50% opacified cores with layered translucent porcelain to replace a PFM crown and close a diastema.

Figures 14 and 15 show a case where six old composites were removed. The gingival contours and crown lengths were altered periodontally, and six translucent veneers made from 25% opacified ingots were placed.

Some cases that appear complicated at first can be very predictable. In the case shown in Figures 16 through 18, composites had been used to mask tetracycline stains and close spaces. The patient did not show any margins when smiling and had an anterior open bite. Thus, adding incisal length to the short teeth will not create occlusal problems, and gingival margins will not be a cosmetic issue in the future.

The patient was restored with six 3/4 Empress II crowns using cores made from ceramic ingots that are approximately 75% opacified. He now shows his teeth when he smiles, and is very pleased with the natural appearance of his teeth.

Restoring a peg lateral is the one case where restoring a single anterior tooth is predictable and profitable, as illustrated in Figures 19 and 20. The tooth is practically prepared before you begin. The color matches the adjacent teeth, and most of the enamel will remain on the tooth, so you have great bond strength and no flexing of the tooth in excursive movements. This tooth was restored with Empress I. A TI 25% opacified shade 110 material was used. This case could also easily be restored with a feldspathic porcelain laminate. (Generally an acceptable shade match for any single upper lateral incisor is not too difficult.)

CONCLUSION
When teeth are in the correct position, the color is good, and there is minimal tooth reduction, dental laboratories can easily produce an exceptional aesthetic restoration with the most translucent pressable ceramic materials. Ceramic cores with varying levels of opacity should be used for more complicated cases. This material requires significantly more skill and effort by the laboratory technician.

More complicated aesthetic cases require a partnership between the dentist and the laboratory technician. Skilled partnerships can produce aesthetic restorations with pressed ceramics, milled porcelain cores, or porcelain-fused-to-gold restorations. Let the situation and your combined skills determine the material to be used.

Acknowledgment
The author would like to thank Ken Rockwell of Rockwell Laboratories for the high-quality laboratory work and his technical advice.

Dr. DeLopez maintains a private practice in Tallahassee, Fla, with an emphasis on restorative and cosmetic dentistry. He is the former president of the Leon County Dental Association. He can be contacted at drtomd@comcast.net.