Special Print 2009 – Becker J. et al.

improved guiding. Through the horizontal platform the distance between the implant-abutment interface and the alveolar crest is increased and hence the hypothe- sized influence of the inflammatory cell infiltrate on bone resorption is decreased. Another advantage of the platform switching design could be the gain of surface area at the platform of the implant. This surface gain may facilitate the soft tissue to attach and to reduce bone resorption since less surface area is now required at the implant neck (Lazzara and Porter, 2006). Further- more there is some preliminary evidence that this spe- cific implant-abutment configuration decreases stress translation to the crestal bone-implant interface (Maeda et al., 2007; Schrotenboer et al., 2008) and thus reduces bone loss. Two animal studies were performed to investigate the principle of platform switching with CAMLOG im- plants. The first experimental dog study indicated that a cir- cumferential horizontal platform of 0.5mm prevents the apical downgrowth of the barrier epithelium over an observation period of 28 days and therefore slightly better preserved the crestal alveolar bone at the implant (Becker et al., 2007). The second platform switching study in dogs was conducted over a period of 6 months to obtain long term data on the maintenance of soft and hard tissue at the implant (Becker et al., submitted). The second gen- eration of CAMLOG ® SCREW-LINE Promote ® plus im- plants (K-Series; ø 3.8mm; L11mm, Fig. 1) were inserted acording to the standard surgical protocol approxi- mately 0.4mm above bone level after mucosal incision with mucoperiosteal flaps in the posterior region of the mandibles (Fig. 2). At least 1mm residual thickness of the alveolar bone crest at both buccal and lingual as- pects of each implant site was preserved. Wide-body matching healing abutments (ø3.8mm, H4mm, stand- ard configuration) and non-matching (ø3.2mm, H4mm, platform switching configuration) randomly assigned in a split-mouth design were connected and served ei- ther as control or test implants with a circumferential horizontal platform of 0.3mm, respectively. The histological examination after 4 weeks of heal- ing revealed that at both test and control implants a mature woven bone was formed spanning the gap between the adjacent alveolar bone and the implant surface. Considering the initial insertion depth, first appearance of crestal bone changes could be observed in both groups without reaching statistical significance. Fig. 2 Surgical procedure (pictures by courtesy of J. Becker and F. Schwarz) Fig. 2a Implants (K-Series) inserted 0.4mm supracrestal according to the standard surgical protocol Fig. 2b Inserted implant covered with a nonmatching healing abutment (platform switching) Fig. 2c Implants with healing abutments were left to heal in a transgingival position