April 2013, Volume 9, Issue 4
Published by AEGIS Communications
The Art of Natural-Looking Ceramic Restorations
Shape, color, and texture of gingiva and dentition play roles in esthetics
A 60-year-old man presented to the prosthodontist in an edentulous state, ready to replace his mandibular arch with a permanent, fixed, long-span implant bridge restoration. He was content to temporarily repair his maxillary region with a provisional bridge due to budget constraints, but he intended to replace the teeth at some point in the near future. An oral surgeon performed the implant surgery, and the patient returned to the prosthodontist for the final restorations after the appropriate healing had taken place. This case study outlines and explains the laboratory protocol that was followed in the fabrication of the bridge to achieve the best possible ceramic work and esthetic outcome.
When prescribing a full mouth denture case, a face-bow is always recommended for accuracy (Figure 1). Using a Panadent ( www.panadent.com) articulator with a stick bite, the clinician was able to record his observation that the patient’s midline was slightly off. He was also able to observe and verify the horizontal reading. The case was then sent to the laboratory, where models were poured up and articulated.
Impression copings were placed before the impression was taken (Figure 2). With the full arch mandibular impression, the implants took various angles and positions due to the density of the patient’s bone.
For the maxillary edentulous area, the author’s plan was to fabricate a temporary denture to engage with the lower area (Figure 3). The guide needed to be perfectly aligned and the occlusion was checked for bite verification. Before creation of the provisional denture, the impression was taken, the model poured up, and the denture was sent for processing. Because this case would also involve a mandibular cement-retained bridge, an impression was taken for the mandibular arch (Figure 4).
After taking the impression, the temporary abutments were placed for the provisional denture while the patient awaited his permanent restoration (Figure 5). The laboratory fabricated a temporary denture, which was placed and engaged with a wire connection to the implants to protect against fracture (Figure 6). The patient was informed that he would wear the temporary denture for a period of 3 to 4 weeks.
Before processing the maxillary provisional denture, the technician noted the midline while matching the central teeth in line with the lower arch models (Figure 7). The CAD/CAM-designed titanium abutments were fabricated at the GC Milling Center (Figure 8). The six abutments were created with excellent margin integrity design. Placed on the model for a fit check, a Primotec ( www.primotecusa.com) light-curing gel verification index was positioned over the implants. The clinician would later place the verification jig in the mouth for a try-in and fit check.
After finishing the final frame design, the laboratory technician tried the two restorations on the model to check the occlusion and fit (Figure 9) and then sent the entire package to the clinician for a wax try-in for the maxillary and a frame check for the mandibular. Gel served as the stop line for the touching occlusion of the denture teeth to control and verify vertical dimension in the mouth before continuing with the fabrication of the final restoration.
Color and Shape
Once verification was completed, the case was sent back to the laboratory for further processing. The technician applied GC Initial™ MC (GC America, www.gcamerica.com) to the mandibular framework (Figure 10). After the gingiva and enamel color were applied together, the teeth were fabricated with a natural-looking embrasure design. The perpendicular horizontal line was identical in measurement for the mandible. The denture teeth were reset to provide perfect occlusion with no interference so that the teeth would not fracture or move.
The final porcelain buildup was applied in a neutral color and fired (Figure 11). The color used for the base was A2. With a large case such as this one, it is possible to provide more detail in the final color of the restoration and overlay it with a clear color. The technician concentrated on matching the age of the patient’s dentition using a subtle orange/brown tone to avoid a fake or unnatural white appearance in the final restoration.
Before the final firing, the technician created color-coded texture lines and lobe designs that would help create a 3-dimensional appearance in the final restoration (Figure 12). Black lines indicated places where more grinding would be needed to create a look of depth or shadow. Red lines indicated lobe or contour design that was farther out in front, as in the reflection area. The goal was to fabricate a triangular shape and indentation for a life-like quality. The artistry involved in this type of porcelain work comes from trying to mimic the natural attributes of human dentition in terms of shape and color. It also relates to the size of the teeth the clinician decided upon and the amount of space left between teeth to create an illusion of width. The indentations between the teeth intentionally vary somewhat in size; this follows nature’s way of creating perfect imperfection.
The other important consideration for this porcelain work was the appearance of the gingival tissue. Accurate representation is essential to the development of the mandibular area, because without 6 mm to 8 mm of porcelain fused to ceramic, the gingival area will look too thin and the teeth too large. In the author’s opinion, that is the key to an esthetic denture case. Subtle gum tissue can be created using various colors besides pink. When a variety of colors are involved, compensating with enamel overlay can create natural color and contour to exactly mimic the appearance of natural tissue. As with the teeth, the design has to be considered and orchestrated carefully with an understanding of surface texture; again, colored markings can indicate depth and incisal table creation.
In this case, the top teeth were built from canine to canine, after which the premolars and molars were added. Each section was built with an eye toward emulating the imperfections found naturally in dentition. Figure 13 shows the results of the final restoration with the incisal one third in a whitish color and an orange/brown coloration covering the rest of the tooth surfaces. In addition to this natural coloring, the use of convex and concave contouring lends a life-like appearance. The contour of the premolar is “out” to support the lower lip.
Figure 14 shows the tissue color and incisal translucency details of the restoration immediately after insertion. With the patient biting each surface together, the temporary denture in the maxillary and the permanent in the mandibular are juxtaposed (Figure 15). The color differentiation is obvious, with the teeth on the upper arch being more yellow in appearance. The patient did not care for the temporary tooth color, but was assured that a formula that matches the mandibular restoration would be used for his future permanent denture teeth.
It is the author’s contention that if technicians do not pay attention to the gingival tissue area when creating a restoration, the attention paid to the denture teeth will not have as great an impact. Fixed, edentulous, ceramic cases must be considered from the gingiva to the dentition. Denture technicians have known this for years, but ceramic technicians often are less aware of the importance of the gingiva. Without the application of several colors, the tissue color will not look natural and will not enhance the beauty of the teeth.
Patients’ tissue color will vary according to age and will present as thin, thick, irregular, bulky, red, pink, or even white on top, depending on the patient. Careful observation will improve a ceramist’s ability to create natural, beautiful-looking restorations in the final analysis.
Joseph L. Caruso, DDS, MS
Luke S. Kahng, CDT
LSK121 Oral Prosthetics