Combining Technologies for High-Tech Results By: Robert Zena, DMD

In our fast changing profession there have been great strides forward in technology, which have made it possible to fabricate extremely advanced restorations. These restorations are advanced in many ways, not only regarding aesthetics but also materials selection, precise fit, quality assurance, bio-pharmacology, production and cost efficiency.

Case Presentation

The patient is a 75-year-old female retired teacher, who is well educated and has a healthy attitude regarding her oral care. She is nearly edentulous in the Maxilla and wears an upper removable partial denture (Fig. 1). Her chief complaint was mobility of her lower incisors and their unaesthetic appearance. She had a pre-existing periodontal condition of her lower incisors, pockets and horizontal bone loss that had been treated by periodontal osseous surgery and tissue repositioning. After her surgery, a previous dentist splinted the lower anterior teeth with composite resin bonding. Her lower incisors were mobile due to the horizontal bone loss, but her periodontium was restored

Figure 1

to a healthy state after surgical intervention. Her lower incisors are in a natural state, free of restorations, however there are caries under the existing composite bonding splint. Also one of the canines and one of the incisors have de-bonded from the splint. Her periodontal situation was stabilized yet she had a compromised crown to root ratio.

There are several treatment options for the patient, re-implementing composite bonding and splinting, extraction of the lower four incisors and replacement by a fixed bridge, implants or a removable partial denture. Another possibility is to splint all the involved teeth with a fixed prosthesis for stability. Then the patient can keep her teeth with all the advantages of that, such as: proprioception, incising force, phonetics and preservation of the remaining alveolar bone. Another advantage of this type of splint is that if she were to require extraction of a lower incisor at a later date, the root could be sectioned from the splint and removed without disrupting the coronal portion of the splint. Also there is the psychological advantage of keeping her teeth.

It was decided to splint her lower anterior dentition with splinted crowns because of the lost bone and mobility, and the other advantages previously mentioned. The patient presented with lower anterior teeth splinted with composite bonding. The patient presented to me with concerns not only of her difficulty to clean the splints but also her left canine and lateral incisors had de-bonded and she was unhappy with the aesthetics. Her case was chosen for this project because of its high technical demands.That is; loose lower anterior teeth with small dimensions, plus high aesthetic and structural demand essentially the worst of all worlds.

Materials Selection
Core Selection
Because of her periodontal situation, the size of the teeth, the fact the teeth must be splinted, and the aesthetic demands, it was decided to use Captek as a core material. The reasons for this are as follows. Due to the size of the lower anterior teeth, the core material has to be thin and also a good base for porcelain. The core must be veneered in a thin dimension without fear of de-bonding or being unaesthetic. The material needed to be bacteriostatic to minimize the plaque accumulation near the already compromised periodontium. This was critical to her long-term success. Captek would be a wise choice for her because it would decrease the plaque associated with her restorations and facilitate her hygiene, can be fabricated in thin dimensions, has no oxides and is a very aesthetic base, good compatibility with Heraceram and is strong enough to be able to support the splint biomechanically but also strong enough to be converted to a six-unit bridge with only the canines as abutment teeth, should the patient loose the incisors over time.

The form of the teeth would be much more anatomical because of the thin dimensions of the copings and their ability to be covered with opaque in one coat, and the thin veneering ceramic layers. With conventional castings they have the ability to be finished down to thin dimensions but the distance from the tooth surface to the coping’s external surface is usually increased by air trapped under wax patterns, die spacers, die lubricants, inconsistencies in casting dimensions, casting shrinkage, investment expansions etc. The porcelain layers on conventional metals must also be thicker due to the oxides of the metals discoloring the ceramic. The other advantage is there needs to be less tooth reduction in the preparations rendering the teeth relatively stronger. This is also a strong advantage when dealing with the small dimensions of the lower incisors.

The bacteriostatic effect of the Captek material is clinically relevant for periodontally involved teeth, not only for the decreased plaque formation but also the increased longevity of the teeth. The core also needed to be strong and capable of being assembled in a very accurate way into a six-unit splinted structure. In other words one that fits extremely well on six abutments simultaneously, after being assembled into one unit. There is only one core-material, which fulfills all of these requirements, Captek. It is strong, can be post-soldered accurately, has no oxide, can be fabricated in very thin dimensions and is bacteriostatic.

Veneering Ceramic
The porcelain had to be extremely aesthetic and have the light properties to look natural in a very thin dimension due to the size of the lower anterior teeth. This case was selected because of the high technical demands of the situation. It was the hardest situation with the greatest demands of the materials employed. Heraceram was selected because of its light properties strength and its bond strength to Captek. It was decision based upon the demands for the patient and the core selection. Heraceram would be the perfect material due to its excellent results with Captek and its smooth surface which is more compatible to the soft tissues and opposing dentition than any other rough surfaced ceramic. Also the light transmission and the fluorescence of the opaque could render extremely aesthetic results in a very small thickness.

Laboratory Selection
Selection of the laboratory is the next choice that must be made. The laboratory must have the capability to produce a highly accurate coping not only on an individual abutment but must also have the technology to splint all six abutments into a fixed bridge with no loss of accuracy. They must have a quality assurance system where the case could be sent with the confidence that a returning restoration will fit accurately and look aesthetic. MicroDental was chosen due to their highly efficient Captek team. They are dedicated to producing accurate restorations on a consistent basis and one of their teams only produces Captek copings. In other words that team specializes in producing Captek copings in large quantities which are uniform in quality and accuracy.

Case Sequencing
After the assessment of all the clinical factors the teeth were prepared for a six-unit fixed partial denture. Careful attention was paid to the parallelism of the preparations, as well as the apical positioning of the margins. The final marginal position is just at the CEJ. This is very important because the teeth naturally taper apical to this position rendering less available tooth structure for reduction. This also eliminates margins close to the tissues so there will be no inflammatory response from this marginal position. There is no root sensitivity in this case and the patient’s oral hygiene is remarkably good. The preparations were made according to the guidelines suggested by Captek. This includes a deep chamfer margin with reduction for porcelain and metal, approximately 1.5mm of facial reduction was strived for but not always attainable because of the size and relative positions of the teeth. Because of the small size of the lower anterior dentition the preparations tested the skills of the operator (Fig. 2). Any clefting on the facial of the incisors at the marginal areas was also reduced apical to the clefting, however complete obliteration of the clefts was not desirable. These undercuts could be easily blocked out in the master dies. Impression making was also facilitated by the marginal positions insuring a tight seal of all the teeth.

Figure 2

Figure 3

Next an impression was made and dies prepared for the case. Note the gingival health of the dentition after removal of old composites and fabrication of temporaries (Fig. 3). The incisal positions of the preparations follow the lip lines for enhanced esthetics. The dies were copied in a silicone mold and a refractory material poured. Refactory die of one of the abutment teeth. Next the P material is adapted to the die and blended smooth. Careful attention is made to insure marginal fit. Die with adapted P material is then placed into the Capress where it is pressed under pressure to further smooth and adapt the P material to an even thickness. P material after pressing, note the smooth continuous surface (Fig. 6). P material after firing, resulting in a porous core ready for influx of 22k gold (Fig. 7). The G material is then adapted to the core and fired (Fig. 8). After firing the coping is then trimmed and smoothed (Fig. 9). Next Inflow material is added to the coping and fired to resurface coping from finishing. The coping is then placed over plastic sheet onto master die. Plastic is also placed over the coping on the master die. The die is then placed into a swedger. Comparing the coping before and after swedging. Note the much better marginal adaption after swedging (Figs. 10 and 11). Captek copings after swedging ready for placement on the master model. All copings in position on solid model. Note precision of fits. Copings are then captured pulled and placed into a soldering investment. Copings in soldering investment with wax removed (Fig. 12). Capcon placed in connector area. Capcon placed at remaining connectors (Fig. 13). Fixed framework with six abutments soldered together. Close view of dense connector (Fig. 14). Capbond applied to framework to insure proper color and bonding of the Heraceram (Fig. 15). Capbond makes a perfect surface for porcelain bonding. Framework is now ready for porcelain application. Opaque application, because of the rich color and surface of the coping, the past opaque covers easily in one thin coat. After firing the opaque takes on a low sheen color dense layer which is ideal as base for the overlaying ceramics (Fig. 16).

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Next the neck colors are added near the marginal areas. This layer is a simple task with the Matrix System.

The ceramic build-up to full contour, careful attention must be paid to color layering and the final form. Particular care with the incisal details of color and form is essential to final aesthetics.

Closer look at the incisal form both during the build-up and after first firing. Many factors must be allowed for, especially the shrinkage of the ceramic after the first bake.

Frontal view of build-up and first bake, all aesthetic details must be incorporated initially, for example the check-lines.

A view of the left side shows more color and effects. Notice again the check lines and also the incisal opalescence of the canine and how light is gathered to the incisal edge just as nature.

The right view of the case (Figs. 17 and 18).

Frontal view of the final ceramic bridge. Nice aesthetics with a strong base (Fig. 19).

Lingual view displays the excellent aesthetics of the incisal edges. These effects are simple with the Heraceram porcelain (Fig. 20).

Measuring the full mid facial thickness of the metal and ceramic. The total thickness is 1mm. This is nearly impossible to accomplish with this aesthetic result of the Heraceram and also the strength of the Captek, with an alternative system (Figs. 21 and 22).

Frontal view of final work showing good aesthetics with a very nice surface.

Lingual view of the final work. Each tooth has its own characterization.

Restoration in the mouth. Notice how the light is refracted along the root and the ceramic of the canine in the same manner. This is because of the light properties of the Heraceram (Figs. 23 and 24).

Lingual and frontal views of ceramic in vivo. Light refraction of incisal is again like nature.

Bridge in its natural environment, comfortable with the surrounding light and color.

Nice view along the incisal edges in vivo.

Restoration of the lower anterior teeth, in harmony with the lips and the upper teeth (Fig. 25).

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Conclusion
This case was selected to illustrate how advanced technologies could be combined to render the best results for a clinically demanding case with difficult demands. These difficulties were overcome with technology that a few years ago wouldn’t have been possible to solve in such an aesthetic biocompatible manner. Patients’ dental needs are becoming better managed through our technology. It has made quantum leaps forward and it has brought clinical care to new heights. Clinicians, manufacturers, and technicians must meet new demands in keeping up with technology and implementing it into our profession. The new challenges will be met by even better technology. New horizons lie ahead for us to focus upon.

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Robert Zena, DMD, maintains a private prosthodontic practice in Louisville, Ky., and serves as an Associate Clinical Professor in the Postgraduate Prosthodontic Program at the University of Louisville, Louisville, Ky. He lectures internationally on ceramic restorations, has contributed to one book, and serves on the editorial review board of Practical Periodontics & Esthetic Dentistry, Spectrum, and The Journal of Multidiciplinary Collaboration in Prosthodontics. He has also served as a consultant to various companies in the dental industry.

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