Anna Gabriella Camacho Presotto1, Valentim Adelino Ricardo Barão2, Cláudia Lopes Brilhante Bhering3, Marcelo Ferraz Mesquita4. 1. Doctoral student, Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas (Unicamp), Piracicaba, Brazil. 2. Assistant Professor, Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas (Unicamp), Piracicaba, Brazil. Electronic address: vbarao@unicamp.br. 3. Assistant Professor, Department of Restorative Dentistry, School of Dentistry, Federal University of Minas Gerais (UFMG), Belo Horizonte, Brazil. 4. Professor, Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas (Unicamp), Piracicaba, Brazil.
Abstract
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 (α=.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 (μm) (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 μstrain) than casting (225.5 ±142.8 MPa; 226.95 ±55.4 μstrain) and SMB milling (218.6 ±101.7 MPa; 289.7 ±89.3 μstrain) (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 methods.
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 (α=.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 (μm) (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 μstrain) than casting (225.5 ±142.8 MPa; 226.95 ±55.4 μstrain) and SMB milling (218.6 ±101.7 MPa; 289.7 ±89.3 μstrain) (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 methods.