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Dental Tribune Middle East & Africa Edition No. 5, 2015

lab tribune Dental Tribune Middle East & Africa Edition | September-October 20152C < Page 1C teeth no. 13, 14, 15 and 23, 24, 25 were sheathed with electrofor- med copings (secondary parts) attached to a tertiary structure made of base alloy. The electro- formed copings were cemented to the base alloy structure in the oral cavity to ensure a ten- sion-free fit. Tooth setup was performed according to con- ventional prosthetic principles while the static and functional requirements as well as the pa- tient’s individual expectations were taken into account. Tooth position, smile line, lip volume, phonetics and other criteria were checked in the course of an esthetic try-in (Fig. 1) before fabricating the final denture. Natural-looking artificial gingi- va parts were already achieved in the wax-up and the soft tissue areas were individualized with subtle but effective touches (Figs 2 and 3). Lab procedure After both the dentist and patient had approved the wax-up, the denture was ready to be pro- cessed into acrylic. To perform this task, I used the IvoBase den- ture base system, which allowed me to transfer the wax-up to the final restoration without loss of detail. Investing and boiling out Both flask halves were identical. Prior to investing the model, I placed the flask lid, access for- mer half and filter wax compo- nent in one of the flask halves. After applying a thin coating of petroleum jelly to the inner surfaces of the prepared flasks, I soaked the model with the mounted waxed-up denture with water and isolated it with stone-to-stone separating fluid. The model was now ready for being invested in plaster; a Class III dental stone is recommended for this purpose. I took care to place the model at the centre of the flask and to ensure a space between the anterior margin of the model and flask of approx. 10 mm. To create a flush surface between the edge of the model and the flask housing, I re- moved all surplus plaster whilst it was still soft. The stone surface should be flush with the access former to prevent the plaster from spalling during the subse- quent working procedure. After the stone had hardened, I replaced the access former half with the access former full and positioned the prefabricated injection wax component. As a palate-free denture base was fabricated in the present case, the sprues were pressed onto the maxillary tuberosity. I made sure that the sprue was contigu- ous in all areas of the denture base. Then, I attached what are known as aeriation channels at the anterior region to vent the flask cavity during the injec- tion process. These components were also prefabricated and were easy to connect to the den- ture base. Important: the aeri- ation channels must not come into contact with the flask hous- ing. Next, I coated the teeth and gingival areas with a medium- body addition curing silicone (A- silicone of a shore hardness of 65) and then applied some stip- pling to the silicone before it had set to create a retentive pattern and secure the silicone in the stone. No silicone was applied to the occlusal surfaces and access former. After isolating the stone surface, I positioned the upper flask half and locked the flask halves using the locking clasp. Then, I filled the flask with den- tal stone (Class III) with the help of a vibration device to avoid air bubbles. Excess stone was skimmed off so that a flush sur- face resulted between the stone and flask lid. Once the stone had set, the flask was heated in a water bath at 90°C and then the two flask halves were sepa- rated. The wax was now soft and could be easily removed in large pieces. After the full access former had been taken out, the model and teeth were boiled out with clean boiling water to thor- oughly remove all wax residue. Transfer to acrylic Thebasalsurfacesofthecleaned teeth were roughened with jet medium and mechanical reten- tions applied with a small round bur. After that, I returned the teeth to the silicone key. Next, I applied a thin coating of Sepa- rating Fluid to the stone sur- faces of the cooled flask halves (Fig. 4). Prior to joining the flask halves, I masked the base metal alloy framework with opaquer. For this purpose, I used a pink opaquer for the gingival areas and a tooth-coloured shade for the areas under the telescope teeth. These materials were first applied as a foundation layer and then in a covering layer. Once the framework had been thus prepared, it was placed on the model and secured with wax (Fig. 5). The aeriation filter, centring insert and funnel were inserted and the flask halves as- sembled. The denture base materials are available in seven shades. For the case presented here, I se- lected IvoBase High Impact in shade 34-V. I removed the mon- omer container from the pre- dosed capsule, joined the fluid and powder and mixed the two components to a homogenous mixture. With a few easy manip- ulations I attached the centring insert and flask to the capsule and then placed them into the injector according to the manu- facturer’s instructions. Next, I selected the relevant injection program and then started the in- jection process (Fig. 6). The pro- cess was fully automated and, with the RMR function added, took approx. 65 minutes to com- plete. The RMR function further reduces the already very low content of residual monomer to below one per cent. As the injec- tion and polymerization process were exactly matched to the ma- terial, chemical shrinkage was completely compensated. Once the program had been complete, I removed the flask and cooled with water. Divesting was per- formed under a dental press. The IvoBase System includes a divesting aid to facilitate this process. Having detached the flask halves, I carefully removed the denture from the stone core and separated the capsule us- ing a separating disc (Fig. 7). All waxed-up areas were faithfully reproduced in the acrylic. Completing the denture Now, I directed my full attention to finishing the denture. The advantage of using this system became most apparent at this stage, as hardly any rework- ing was necessary. The finely modelled surface structures and textures of the wax pattern were replicated in the acrylic without loss of detail. In a few quick steps the denture base was ready for final customiza- tion (Fig. 8). With SR Nexco, the artificial gingiva can be given an individual touch and natural- looking characterizations to suit the patient’s expectations. SR Nexco ideally complements the IvoBase denture base material (shade 34 V) (Fig. 9). I applied a light-curing con- ditioner (SR Connect) to the acrylic surface to create an ad- hesive interface that would al- low the application of individual shade characterizations (Figs 10 and 11). After that, I focused on creating subtle details to re- produce a natural depth effect. I customized the vestibular areas and applied fine capillaries on the facial side using a variety of different shades. Key anatomi- cal features should be borne in mind when characterizing soft tissue parts to achieve a life- like reproduction. For instance, keratinized gingiva has a light pink colour because less blood normally flows through it. By contrast, the mucogingival ar- eas receive a far larger supply of blood and are interspersed with fine blood vessels. These details were easy to reproduce with the SR Nexco range of materials. Aspects of three dimensionality including alveoli and festooning were already created in detail in the wax-up and transferred to the acryclic without loss of detail using the IvoBase System. The SR Nexco gingiva materials and my technical skills enabled me to individualize the prosthetic gingiva by applying materials in different shades in a targeted fashion to attain a natural-look- ing final result (Figs 12 and 13). Prior to final light-curing, I cov- ered the entire surface with an oxygen-tight glycerine-based gel (SR Gel) to prevent the for- mation of an inhibition layer. After completing the final po- lymerization process, I polished the surface. The use of goat’s hair brushes, a high-gloss buff and Universal Polishing Paste effectively resulted in a superb- ly smooth and glossy surface, without loss of surface texture or shade characteristics. Result Pink esthetics that very closely resembles healthy soft tissue is the result of this approach. Fine details of texture – such as sub- tle stippling, slightly accentuated alveoli or free gingiva margins – give artificial gingiva a natural appearance. The IvoBase den- ture base material beautifully harmonizes with the SR Nexco composite and together, these two materials create natural light reflections and a dynamic interplay of colours. The com- pact and smooth surface is not only esthetically pleasing but also provides optimum condi- tions for denture hygiene (Figs 14 and 15). Conclusion The IvoBase injection process provides a straightforward method to process waxed up denture bases into high-quality PMMA. Waxed-up setups can be transferred 1:1. Polymerization shrinkage is mostly compen- sated, thus minimizing the effort required by the dental techni- cian. The soft tissue parts can be customized to meet the individ- ual expectations of the patient and to provide dentures with natural-looking pink esthetics. I would like to thank Dr. Rafaela Jenatschke and OA Dr. Tobias Locher/Frankfurt on the Main for the dentistry-related work. Fig. 7: Careful divesting after the fully automated polym- erization process Fig. 12: Characterization: subtle stippling and fine red blood vessels enhance the natural appearance of the pros- thetic gingiva parts. Fig. 14: The tooth replacement harmoniously integrates into the patient’s face and satisfies his esthetic expectations. Fig. 15: Successful interplay between light, shadow and shade. The surface texture modelled in wax has been processed into acrylic without loss of detail using the IvoBase System. The resulting light dynamic properties convey a natural appearance to the artificial gingiva. Fig. 8: Finishing requires only a few steps as the wax-up is processed into the acrylic without loss of accuracy. Abb. 13: The individual SR Nexco materials can be adapt- ed using a disposable sponge. Fig. 9: Light-curing SR Nexco compos- ite can be optimally combined with the IvoBase System to characterize the denture base. Fig. 10: A thin coating of bonding agent is applied to the gingiva-coloured parts,... Fig. 11: ... allowed to react and then cured with light. Carsten Fischer sirius ceramics Lyoner Strasse 44-48 60528 Frankfurt on the Main Germany info@sirius-ceramics.com Contact Information

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