Avaliação do platform-switching na perda óssea periimplantar marginal: ensaio clínico controlado randomizado duplo-cego boca dividida

Abstract

The objective of the present randomized controlled clinical study was to evaluate the influence of different implant/abutment horizontal mismatch size on marginal periimplantar bone loss. A total of 12 fully edentulous mandible patients were recruited for this study and received 4 external hexagon implants (Strong SW, SIN® - Implant System, São Paulo, Brazil), with a 4.5 mm of diameter and 13 mm of length, in the region between mentonian forams, to support a fixed total prosthesis. The prosthetic components installed on the implants were mini-abutment, all with 2 mm of height and prosthetic profile of 4.8 mm, with different diameter (4,5 mm - CC, 4, 1 mm - PS41, 3.8 mm - PS38 and 3.3 mm - PS33), thus determining different horizontal mismatches (0.2 mm, 0.35 mm and 0.6 mm) between the implant platform and the abutment (ie platform-switching). At the 1 and 3-year follow-up visits, clinical evaluations were performed (probing pocket depth (PPD), modified gingival index (mGI), and mucosal thickness (MTh). Periapical radiographs were also performed at baseline and 1, 3, 6, 12, 36 months implant placement, using the parallelism technique and a digital sensor (Schick CDR Elite, Schick Technologies, USA). 12 finite element models of a fully edentulous mandible with Ø 4.5 x 13 mm implants, abutments, abutment screws, bar, prosthesis and prosthesis retention screws were constructed, simulating each patient included in the study. Bone equivalent strain (EQV strain) and the abutment screws and prosthesis retaining screws EQV stress a have been evaluated. The PS33 configuration (0.6 mm horizontal adaptation) had a significantly lower bone loss (0.74 ± 0.58 mm) than the CC (1.88 ± 0.41 mm), after 3 years of follow-up and statistically similar to PS38 (0.35 mm horizontal misfit) (1.14 ± 0.94 mm). The DC presented bone loss similar to the PS41 configuration (1.65 ± 0.68 mm). The AEF performed in the present study demonstrated a higher efficiency in the PS in reducing peri-implant bone deformation only for the PS38 configuration. A horizontal mismatch size of less than 0.35 mm, did not result in reduction of the marginal deformations compared to the CC. There were no differences between the groups in any of the clinical parameters evaluated. Thus, within the limitations of the present study it was possible to demonstrate that the efficacy of PS in the preservation of the marginal bone is directly related to the horizontal implant / abutment mismatch size.