Platform switching versus regular platform implants. Five-year results from a RCT

Background The concept of platform switching suggests an abutment or a supra-structure with a diameter at the implant platform level that is smaller than the implant diameter. This configuration results in a circular horizontal step, which enables a horizontal extension of the biological width. The rationale for platform switching is to locate the micro-gap of the implant–abutment connection away from the vertical bone-to-implant contact area. Aim/Hypothesis To test the hypothesis that platform switching and regular platform implants would have different outcomes in single-tooth replacement against the alternative hypothesis of no difference. Material and Methods This study was designed as a randomised controlled split-mouth trial. Eighteen patients with bilaterally missing single premolars or molars to be restored with implant-supported single crowns, were consecutively enrolled. Implant sites were randomly assigned to be treated according to the platform switching concept (PS group), or with matching implant–abutment diameters (RP group). A total of 36 Nobel Replace Tapered Groovy implants were installed. All the implants were inserted in healed bone, with an insertion torque between 35 and 45 Ncm, according to a one-stage protocol. Both implant types were loaded with a screw-retained temporary crown 3 months after implant insertion. Definitive screw-retained single crowns were delivered 2 months later. Outcome measures were implant and prosthetic survival rates, biological and prosthetic complications, radiographic marginal bone level (MBL) changes, pocket probing depth (PPD) and bleeding on probing (BOP). Results One patient dropped out after five years and no implant failed. No prosthetic complications were recorded. One patient experienced mucosal inflammation with positive BOP (RP group) after 3 months, three patients had bilateral peri-implant mucosal inflammation with positive BOP at 6, 24 and 36 months respectively no other complications were recorded up to 60 months. There were no statistically significant differences between groups for complications (3 18 vs. 4 18+ P = 1.0). At 5 years follow-up mean MBL was 1.24 ± 0.39 mm in the RP group and 1.20 ± 0.21 mm in the PS group, with no statistically significant differences between groups (P = 0.85). At 60 months follow-up mean PPD was 2.58 ± 0.58 mm in the RP group and 2.40 ± 0.72 mm in the PS group with no statistically significant differences between the groups (P = 0.49), mean BOP was 0.90 ± 0.88 mm in the RP group and 0.93 ± 0.97 mm in the PS group with no statistically significant differences between the groups (P = 0.85). Conclusions and Clinical Implications The clinical and radiographic outcomes of implants restored according to the platform- switching concept versus implants restored with the matching implant–abutment diameters are comparable, 5 years after loading.