and 5 other(s)
Background: The etiology of marginal bone loss (MBL) around implants, even if numerous hypotheses have been proposed, remains not completely clarified. Among the various influencing factors, Linkevicius (2015) suggested that MBL around platform-switched implants surrounded by thick soft tissue is lower than around fixtures with thin soft tissue (<2mm height). Moreover, recent studies (Galindo-Moreno 2015; Blanco 2018) demonstrated an inverse correlation between MBL and prosthetic abutment height. Aim: The aim of this randomised study was to analyse the influence of mucosal vertical thickness on MBL around platform-switched implants, by using both short and long prosthetic abutments. Materials and Methods: Forty platform-switched implants with internal connection (Shape 1, i-RES, Switzerland) were placed at crestal level in 40 partially edentulous patients requiring single implant-supported restoration in mandible. After three months of submerged healing, implants were restored with screw-retained prosthetic crowns. Based upon the vertical soft tissue thickness (Fig. 1), patients were divided into two groups - thin soft tissue (<2 mm) or thick soft tissue (>2 mm) - and randomised to receive short (1 mm) or long (3 mm) abutments. Periapical radiographs were performed immediately after implant placement, after delivery of prosthetic restoration and after 6 months of functional loading (Fig. 2). Results: At 6 months, implants with a 1-mm abutment presented significantly greater MBL [0.54 ±0.31 (mesial) and 0.70 ±0.47 (distal) mm] compared to implants with a 3-mm abutment [0.27 ±0.28 (mesial) and 0.36 ±0.34 (distal) mm], regardless of the vertical thickness of the soft tissue (p<0.01 – ANOVA test). Conclusions and clinical implications: Vertical soft tissue thickness seemed not to influence MBL around platform-switched implants with either short or high abutments at six months after prosthetic loading. Conversely, results from the present study highlighted that prosthetic abutment height is a more important factor than soft tissue thickness in influencing MBL. Among the other influencing variables, abutment choice seems to represent an important issue to be considered for a long-term peri-implant tissue stability.
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