Dimensional precision of implant-supported frameworks fabricated by 3D printing

Statement of problem. Selective laser melting (SLM) is a promising additive technology for clinical practice, but data on dimensional precision assessed by marginal fit combined with stress and strain investigations of implant-supported fixed partial dentures (FPDs) are lacking. Purpose. The purpose of this in vitro study was to verify whether the SLM additive manufacturing technology provides better dimensional precision for 3-unit FPD frameworks than subtractive manufacturing with soft metal block (SMB) milling and the standard casting technique. Material and methods. Thirty 3-unit implant-supported FPDs with Co-Cr frameworks were made by the casting, SMB milling, and SLM methods (n=10). The marginal fit between the framework and the implant abutment was evaluated with photoelastic (PH) and strain gauge (SG) models. Stress and strain in the implant-supported system were measured by quantitative PH and SG analyses after prosthetic screw tightening. Data were subjected to the Kruskal-Wallis test, Mann-Whitney U test, and Spearman correlation test (alpha=.05). Results. The framework manufacturing method affected the marginal fit (P<.001), stress, and strain values (P<.05). The SLM group showed the best mean +/- standard deviation marginal fit (mu m) (PH model: 8.4 +/- 3.2; SG model: 6.9 +/- 2.1) in comparison with SMB milling (PH model: 42.3 +/- 15.7; SG model: 41.3 +/- 15.3) and casting (PH model: 43.5 +/- 27.8; SG model: 41.3 +/- 24.6) (P<.05). SLM showed lower mean +/- standard deviation stress and strain values (60.3 +/- 11.6 MPa; 91.4 +/- 11.1 mu strain) than casting (225.5 +/- 142.8 MPa; 226.95 +/- 55.4 mu strain) and SMB milling (218.6 +/- 101.7 MPa; 289.7 +/- 89.3 mu strain) (P<.05). A positive correlation was observed between fit and stress or strain for all groups (P<.05). Conclusions. Three-unit FPD frameworks made using the SLM technology showed better dimensional precision than those obtained with the casting or SMB milling methods12113845COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPnão tem2016/23490-