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ORAL REHABILITATION prostheses according to grades 2 and 3 of the three grade scale of chipping fractures (13). Both grades indicate that the alteration of the veneer surface cannot be polished without altering the original anatomic form. In contrast, grade 1 of chipping fractures is used if the altered surface does not involve a functional area and with polishing it is possible to maintain the original anatomy. Clinical procedures for FMIZBRs Four to six dental implants (Titanmed, Milde Implants, Bergamo, Italy) were placed in each of the jaws of each patient in a one-stage surgical procedure with the aid of a surgical guide (Fig. 2). Primary stability, with an implant stability quotient (ISQ) (14) of 65 at least, was obtained for all the implants. Wi th the use of a rubber dam for isolation, autopolymerized acrylic resin (Takilon BB, Salmoiraghi srl, Melegnano, Lodi, Italy) was used to isolate the gingiva and to record the location of the titanium temporary abutments (Cylinder, Milde Implants, Bergamo, Italy). All the implants were immediately loaded with an acrylic screw-retained interim prosthesis. The patients were instructed to remain on a soft diet for the subsequent two weeks. After two months, all implants showed good osseointegration at clinical, instrumental (resonance frequency analysis) and radiographic tests. Using a pick-up technique, polyether completearch impression (Impregum/Permadyne, 3M ESPE AG,Seefeld,Germany) was performed in a customized open tray (Apex trays, Megadenta Dentalprodukte Radeberg, Germany). A plaster model (Esthetic-base gold, Dentona AG, Dormund, Germany) was made and used to obtain an anatomical contour wax-up. Soft tissue was reproduced in the impression using vinylpolysiloxane (Gingifast Rigid; Zhermack, Rovigo, Italy). The maxillary relation was taken with a postural facebow (15). The occlusal vertical dimension and an interocclusal centric relation were transferred to the articulator using occlusal rims. Afterward, a verification device was fabricated intraorally to evaluate the accuracy of the definitive cast. Impression copings were connected to the abutments and splinted to each other with acrylic resin (Duralay, Reliance, Dental Mfg. Co. Worth, IL). The verification jig was sectioned and reconnected, unscrewed, and transferred to the definitive cast. Passive fit of the index on the definitive cast was confirmed, and the accuracy of the definitive cast was verified. The wax contour was then impressed on the plaster model. The plaster model, the silicone mask, and then both components together were scanned with a laser scanner (Dental Wings series 3, Dental Wings Inc., Montreal, Canada). The zirconia core was designed with respect to the ceramic support and directly screwed on 1 to 4 mm shoulder multiunit abutments implant connection (3dObjects, Taverne, Switzerland). Using a reverse engineering technique, the STL files were transformed in JGESS 140 files (Geomagic, Research Triangle Park, NC, USA) and modified by using a CAD system (Rhinoceros, Seattle, WA, USA). For all prostheses, the zirconia core was devised also considering the veneering ceramic. The core was covered by a uniform thickness of veneering ceramic, and a maximum of 2 mm of unsupported porcelain was allowed. The connectors within the crowns were designed with a 10 mm2 area at least, as measured by the software used for the CAD technique. A Computer Aided Manufacturing (CAM) system was used to mill the zirconia core in the pre-sintered state (Zirite, Keramo, Tavernerio, Como, Italia). The cores were then sintered (3dObjects, Taverne, Switzerland), and covered by feldspathic porcelain (CZR Noritake Kizai Co. Ldt, Nagoya, Japan). Porcelain fusion was made with zirconium oxide margins by a single master ceramist (SST Dental Clinic, Milano, Italia), following a slow cooling protocol (16, 17). The passive fit of the fixed detachable prostheses on the abutments was evaluated in three ways. First, pressure was applied first on one end abutment and then on the other one (18) to look for movement of the prostheses. A visual check was then carried out, and fit was evaluated with an explorer (19). Passivity was verified with an individual screw (20) in both sides of the end abutments. No movement of the restoration was noticed at finger sensibility, and the restoration remained in its position at the opposite unscrewed end abutment. The fit between the prostheses and all abutments was clinically verified in three dimensions (21). By using 8-mm-wide, 8-mm-thick shim stock foils (Hanel, Roeko, D-89122 Langenau, Germany), occlusal contacts were tested in maximum intercuspation without interferences in lateral excursions, and adjusted as necessary. All prostheses were polished and lustered before final insertion by using a pearl surface paste (Noritake Kizai Co. Ldt, Nagoya, Japan). According to a previously standardized protocol (22), all patients were submitted to functional analysis of their masticatory muscles after the detachable prostheses were hand screwed in the mouth (Fig. 3). At the achievement of a good neuromuscular equilibrium (23, 24), the screw access holes were filled with gutta percha (Temporary stopping, GC) followed by light-cured composite resin (Filtek Z250, 3M ESPE). Follow-up evaluation Clinical events were recorded as irreversible events (failures) or as reversible/ adjustable events (complications) (25). Failures require the replacement or removal of the prosthesis; the causes could be fractures, loss of retention of the prosthesis, loss of osseointegration of the implant, persistent pain. Technical (loss of retention, crown fractures) and biological (periodontal/ STOMA.EDUJ (2014) 1 (2)