Inside Dental Technology
July/August 2013, Volume 4, Issue 8
Published by AEGIS Communications
Case Success with the Right Porcelain System
Find full control and comfort with GC Initial™ layering porcelain.
One of the most challenging types of cases for a dental laboratory is a full-arch implant splint. The patient in this case presented with a bar and overdenture, but wanted to convert to a fixed restoration. The author received the case with the model work completed and articulated by the prosthodontist.
The prosthodontist created a verification jig in his office to verify the accuracy of his models and set the vertical (Figure 1). To begin, the author attached premade wax pontics to the abutments for the tooth form portion of the frame, then waxed the tissue or bone portion straight down, keeping it thin where it contacted tissue for reasons of hygiene. The vertical on this case was pushing the limits of a fixed restoration (Figure 2). The author then cast the frame in a noble alloy in four sections. Rather than attempting to make a one-piece casting that would control where and how the joints would be designed, the author “butted” them in the middle and opened them in a V-shape so that the frame would be welded from the inside out, thus preventing hollow welds. The author then heat-treated each section before it was welded, and then heat-treated each welded section before continuing. Each section was then screwed down, and a sprue bar was welded on the top—above the joint—to further secure the section. These sprue bars were then welded directly onto the model (Figure 3).
In the author’s wax, two stubs were incorporated on the distal lingual so that he could later weld a stabilizing bar onto them after the metal was tried in. Dental technicians should never fire the frame as one piece until the bar is welded on, and the four metal stops should be left on the occlusal to help the prosthodontist confirm the occlusion. After firing, the author finished, using only carbide burs (Figure 4).
The six anterior teeth were waxed onto the frame. They were then sent for metal try-in to enable the prosthodontist to confirm the mid-line and incisal edge position while also enabling the patient to approve the basic esthetics, thus helping to avoid a situation where the case would need to be returned after it was layered and glazed for midline, length, or other esthetic changes (Figure 5).
After the frame was tried in and returned to the laboratory, the stabilizing bar was welded to the lingual, sandblasted, and then carefully inspected for pits or porosity that could cause future bubbles. Next, the frame was degassed as one piece. Because the author had added the lingual bar and heat-treated each section before welding, he did not encounter any frame warp or distortion during the layering process, and the frame remained completely passive. Without the use of a lingual bar, it is extremely hard to create a frame that remains passive throughout the entire layering process. With $1,800 of nobel alloy and $1,700 in components invested in this case, it was imperative that the frame did not distort. Any movement would have led to a remake.
The author chose to use GC America’s GC Initial™ layering porcelain (www.gcamerica.com), as it offers minimal shrinkage and is stable for multiple firings, all while portraying extremely easy-to-manipulate characteristics. However, technicians should note that in order to best control shrinkage, they must have proper frame support.
The patient requested a bleached BL3 shade with minimal characteristic, but also wanted it to look natural. This caused quite a conflict. The author opaqued the frame with GC Initial’s bleach opaque on the tooth forms and used A1 on the interproximals and tissue areas (Figure 6).
The first opaque was thin and fired at a higher temperature or a bond coat, and the first porcelain firing was Opacious Dentin only (Figure 7). The author wanted a thinner first bake to ensure that all the porcelain would shrink towards the frame, avoiding future voids. After this step, the frame was completely masked to avoid probing for depth.
The second bake used four powders—Bleached Dentin 1, Dentin A1 for the proximal and cementoenamel joint (CEJ), a window frame of bleach enamel, and Fluo Dentin 91 for mamelons (Figure 8). Bleached enamel and dentin BLD 1 for the tooth forms were used for the third build. A1 dentin was used for the start of the root forms and GM 23 was used for the first tissue layer (Figure 9). The author built in the mesial and distal line angles and the height of contours to keep the contouring with a hand piece to a minimum. The fourth build included tooth form touch-ups and the addition of tissue using a combination of tissue shades. The GC Initial Tissue Porcelain Kit offered a variety of shades, including pink, red, violet, and blanched. When layering the tissue shades, the author covered the start of the root forms with the blanched shades and used the darker tissue shades in between, placing some deep red in selected areas (Figure 10).
Finishing the Restoration
The author also executed two more minor bakes not pictured for a total of six bakes. The soft tissue was then trimmed and evened out, as tissue contours are very important for hygiene. In all cases, ridge laps and convex areas must be kept thin so they can be cleaned with a toothbrush and floss. Improper tissue contours can cause tissue and bone recession, as well as bad breath, in fixed restorations, as flanges and concave areas in fixed restorations are food and bacteria traps (Figure 11). In this case, a final natural appearance was achieved in a two-step process. First, the author applied a glaze and firing to seal the porcelain. After glazing, the author cut off the lingual bar and performed a mechanical polish using rubber wheels and diamond paste, and finished with a Robinson Brush (Figure 12 and Figure 13).
A technician must find a porcelain system that he or she trusts and is comfortable using, as this is crucial to case success. This is not only of the utmost importance for the dental team, but ultimately the patient as well.
Al Hodges, CDT, is the owner of Highland Dental Arts in Waynesburg, KY.
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GC America Inc.
Disclaimer: The preceding material was provided by the manufacturer. The statements and opinions contained therein are solely those of the manufacturer and not of the editors, publisher, or the Editorial Board of Inside Dental Technology.