Caroliene Meijndert

64 Chapter 4 precision impression material (Provil Novo, Medium fast set, Kulzer Mitsui Chemical Group, Germany). The impression was sent to the dental laboratory to make a screw- retained provisional restoration, that avoided centric and eccentric contact with the antagonist teeth, and which was placed the same day. The provisional restoration consisted of a platform-switched titanium stock abutment with an acrylic resin crown and was torqued to 25 Ncm. Three months later, an impression was made for the construction of a definitive crown. The definitive porcelain fused to zirconia restorations were cemented onto individualized zirconium abutments with a platform-switched, internal conical connection (zirconium CARES® abutment, Institut Straumann AG, Basel, Switzerland) or were designed as screw-retained restorations with a titanium base (Variobase® for single crowns AS, Institut Straumann AG, Basel, Switzerland). In both cases, the screws were tightened to the implant with a torque of 35 Ncm. For screw-retained restorations the inclination of the implant is crucial. In the beginning of the study, therefore, definitive restorations were cement- retained with a separate zirconia abutment and a porcelain-veneered core. During the study angulated screw-channels became available with the possibility to have any restoration screw-retained with porcelain-veneered zirconia abutments. After installing both the provisional and the definitive restorations, oral hygiene instructions were given to the patients. All the prosthetic procedures were carried out by the same prosthodontist (HJAM). Evaluation The clinical, radiographic, photographic and patient centred outcomes were assessed before implant placement (T pre ), one month after definitive restoration placement (T 1 ) and 12 months after definitive restoration placement (T 12 ) by the same observer (CMM). Outcome measures − Implant survival: defined as the percentage of implants that are in place and functional at the time of follow-up. − Marginal bone level change was measured on standard peri-apical radiographs with individually fitting aiming devices (Meijndert et al., 2004) by a trained observer (CMM). The distance from the implant shoulder to the first bone to implant contact was taken on the mesial and the distal side of the implant. − At implant placement, it was noted if the thickness of the labial bone wall was insufficient, i.e. <2 mm (Grunder et al., 2005), and if additional augmentation was needed.