Dental Tribune Indian Edition

4 Dental Tribune Indian Edition - September 2013 Author_Prof.GregoryGeorgeZafi ropoulos, Germany _Introduction Usually, a full denture is delivered following tooth extraction or implant insertion of a fully edentulous arch. A denture is usually used until the final restoration is performed. A well-designed full denture should fulfill the following criteria: 1) correct vertical height and maxilla- mandibular relationship; 2) accurate occlusion; 3) appropriate choice of teeth with regard to shape, length, width and position; 4) adequate lip support, and 5) proper function and aesthetics to meet the patient’s expectations. The final restoration should fulfill or surpass these requirements. Obtaining a correct impression and accurately evaluating the interocclusal relationship (e.g., interocclusal distance, occlusal recor- ding and determination of the exact position of the placed implants) are often challenging and time-consu- ming tasks.1 The aim of the current report is to present an impression and registration technique that allows the transfer of the interocclusal relationship, occ- lusal recording and esthetics that were initially applied to produce a full denture as a template for the recons- truction of the final full-arch implant. _Materials and Methods Following multiple extraction of a non-salvageable rest dentition and the placement of six dental implants in positions #4, #5, #6, #11, #12, #13, a full denture was fabricated. After the extraction sites had healed and denture sores were eliminated, the function and esthetics of the denture was optimized. If necessary, angulations, shape and color of the denture teeth and the shape of the denture base were corrected (Fig. 1a). The resulting denture was used by the patient until the final restoration was delivered. For the final restoration of the maxilla, an implant-retained denture with telescopic crowns as attachments was planned. After the implant was uncovered, the denture was modified to allow sufficient space for the healing abutments. A duplicate of the denture (DentDu) was made out of clear resin (Paladur, Heraeus, Hanau, Germany, Fig. 1b). A trial of the DentDu was performed and minor occlusal discrepancies were corrected (Fig. 1c). Bite records were taken in centric occlusion with modeling resin (pattern resin® , GC, Alsip, IL; Fig. 1c), using the casts of the original denture. Afterwards, the DentDu was placed in an articulator and a controlling of the occlusion was made (Fig. 2a) with the bite records. A pickup transfer system consisting of a titanium impression post and a plastic impression sleeve was employed (Dentegris, Duisburg, Germany, Fig. 2b). The DentDu was carefully modified by creating internal clearance in the area of the implants so that it could be applied as an individualized custom tray. This permitted it to be fully seated when the impression posts were in place. Impressions were generated by a polyether material (Impregum, 3M ESPE, St. Paul, MI). During this process, the DentDu was kept in centric occlusion using the bite records (Fig. 3a). The titanium impression posts were connected with the implant analogues and with the plastic impression sleeves (Dentegris), which were embedded in the impression material (Fig. 3b). A master cast was then fabricated and articulated with the help of the bite records (Fig. 3c, Figs. 4a & 4b). Customizable abutments (Dentegris) were taken to fabricate the implant abutments. Parallelism, angulation, position and shape of the implant abutments were determined using a silicon key fabricated from a matrix of C-silicone (Zeta-labor, Zhermack SpA, Badia Polesine, Italy, Fig. 5). The dentist and the dental technician relied on two alternatives for customized abutments selection: 1) UCLA customizable abutments (UCLA, Dentegris) for casting with a gold alloy (for example, Portadur P4, Au 68.50 %, Wieland, Pforzheim, Germany, Fig. 6a) or 2) platinum- iridium customizable abutments (PTIR, Dentegris) for casting with a chromium cobalt (CrCo) alloy (for example, Ankatit, Anka Guss, Waldaschaff, Germany, Fig. 6b). Aftercasting,thecustomizedimplant abutments were grinded, polished and served as the basis for the fabrication of electroformed puregold copings with a thickness of 0.25 mm (AGC Galvanogold, Au > 99.9 %, Wieland, Fig. 6c).2-4 The framework was then constructed via CAD/CAM. To ensure proper functioning of the framework, a plastic mock-up and a temporary fixed denture (TFD) were milled (ZENO- PMMA, Wieland). The customized implant abutments, the electroformed copings, the mock-up and the TFD were delivered by the dental laboratory for the next clinical session. The abutments were transferred, positioned on the implants and torqued to 35 Nm using a resin transfer key (pattern resin, GC; Figs. 7a & b). From this point on, the customized abutments remained fixed in order to avoid any possible inaccuracies. The electroformed copings were placed on the implant abutments (Fig. 7c). The mock-up was placed over the electroformed copings and the occlusion was checked with the bite records (Figs. 8a & b). A final impression with a polyether impression material (Impregum, 3M ESPE) was taken with electroformed copings. The mock-up was further set up and used for the fabrication of a new (final) master cast. After the impression was taken, the TFD was fixed on the implant abutments using temporary cement (TempBond, Kerr, Orange, CA). It was then left in place until the delivery of the final restoration (Fig. 8c). The new master cast was articulated with the help of the gold copings and the mock-up. The metal framework Impression and Registration Impression and registration for full-arch implant dentures Figure 1A: Full denture in situ. Figure 1C: Trial of the DentDu. Figure 2A: Placement of the DentDu in the articulator. Figure 2B: Pick-up impression system. On the left: titanium impression post (placed on the implant). On the right: plastic impression sleeve (will be left in the impression). Figure 3A: Taking the impression with the DentDu. The bite records were used to de- termine the exact position. Figure 3B: Fabrication of the master cast. Figure 3C: Placement of the cast into the articulator using the bite registrations. Figure 4A: Master cast. Figure 4B:The master cast is placed into the articulator. Figure5:Thecustomizedimplantabutments are fabricated using a matrix of C-silicone. Figure 6A: Gold customized abutments. Figure 6B: Chromium cobalt (CrCo) custo- mized abutments. Figure 6C: Electroformed gold copings. Figure 7C: Electroformed gold copings in situ. Figure 7A & B: The customized abutments are mounted on the implants using a tran- sfer key. Figure 1B: Duplicate (DentDu) of the inte- rim denture. Figure 8C: Temporary fixed denture in situ. Figure 8A & B: Brial of the mock-up.