Dental Tribune U.S. Edition

Dental Tribune U.S. Edition | April 2015 a9 Ad The initial virtual design, displayed with a 3-D program, enables the technician to analyze and make note of crucial aspects arising from CAD modeling. Everyone communicates remotely and simultane- ously, with the same images on everyone’s monitors, enabling careful configuration of the structure’s design. With this case, adjustments were made to the volume and extent of future pink flanges of the pros- thetic body and optimized, by advanta- geously varying the position, the retention clips (ball-attachment), embedding them in adequate volume areas within the coun- terbar. To prepare the device for the practice’s functional and esthetic testing, the portion of prosthetic body was partially reduced in thickness using the micromotor, and pink waxwasadded.Testingalsoenablesthepa- tient to clearly see the boundary between the pink gum and the arch of the teeth (Fig. 3). The dentist/specialist checks accu- racy of fit, articulation with the antagonist and functionality of eccentric movements. For the transformation of the esthetics, we use a joint casing in the mold with a sili- cone base sufficient to place the counter- bar. Simple steel wire sections (for hooks) with a diameter of 0.9/1.0 mm applied on the model act as channels for injecting the composite. With this case, once the base silicone mold was isolated and the joint casing lid closed, we were ready to cast the transparent silicone (22 shore hardness). Polymerization of this takes place under pressure (4/6 bar) for 30 minutes (Figs. 4, 5). The counter die, separate from the base, was put aside, and we used the micromo- tor for milling, preparing the cut of the enamel on the model. The aim was to cre- ate sufficient space to be able to insert the characterization between dentin and enamel, with effects and contrasts to high- light transparencies, color and mamelons. Using a second cover (having prepared the injection channels again), we proceeded as in the previous phase to the casting of the transparent silicone. This technique provides obvious advan- tages: First, we will be able to use the initial prototype/model in every way, thus avoid- ing repeating any phases. The material re- ductionfortheenamelcut,carriedoutwith the micromotor, reduces risk of hitting the metal in the structure. With practice, it’s possible to correctly calibrate the volume between dentin and enamel, for inserting the color effects. Going back to the practi- cal phases, we can now free the armor and treat the metal by sandblasting (Al2O3), silicification, salinization and laying of the opaque, curing and self-curing (Figs. 6-8). A first application of colored dentine, with joint casing open, created more depth in the holes of diatoric teeth and in inter- proximalareas.Tointensifythecolorofthe canines, we applied a type of “shell” with a more intense color mass so that the dentin, once thinly injected, reveals a color with a more pronounced tone. Everything was pre-polymerized through a “quick” device to proceed to closing the joint casing. The spout of the syringe was inserted, then starting from one of the more distal injection channels, we extruded the material. Because of the transparency of the counter die, we were able to confirm complete filling of the space with the dentin mass. If necessary, we can use the other channels by progres- sively moving the syringe into the other holes (Figs. 9, 10). The joint casing, being filled in this way, must be kept in the dark for 10 minutes before proceeding with cur- ing, enabling release of any small excess of injected material (Fig. 11). Being able to accurately calibrate the exact amount of material needed to fill the cavity reduces waste. Once curing was complete (a few min- utes is enough), we separated the counter die and, without touching the dentin, cut the injection channels with a scalpel. This characterization phase, with the creation of contrasts by inserting colored and trans- lucent masses, is typically considered the most creative part of the transformation process (Fig. 12). Keeping the surface “dispersion phase” of the pre-polymerized composite intact maximizes adherence of the characteriza- tion and the enamel injected in the coun- ter die (with the complete anatomy of the arch). Again, with the joint casing closed, the transparency enables identification of spaces that need to be filled by injecting enamel through the provided injection channels (similar to Figs. 9–11). As previous- ly noted, it is good practice to let the joint casing “rest” in the dark for 10 minutes to let any excess injected material flow from the channels. Pre-polymerization takes aboutonemin- ute with the cover. Once removed from the mold, the product is again exposed to light asrecommendedbythemanufacturer’sin- structions (Figs. 13–15). Accuracy of the materials used, com- bined with the described transformation system, does not allow chewing mounts to be inserted. The more accurate the model- ing phase, the quicker the finishing times. To coat the gum portion, we first treated and opacified the metal and, to also identi- fy the pink prosthetic body, applied a paste composite by hand (Figs. 16, 17). The product (Figs. 18, 19) still deserved a few considerations. For the retention system used between the bar and the counterbar, we took advan- tage of the accuracy and versatility of the CAD/CAM systems and decided to used a modern interpretation of a “simple ball at- tachment.” Starting from the principle that the nylon retention cap can be replaced at Fig. 20 Fig. 21 ” See INTERACTION, page A12 INDUSTRY CLINICAL

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