Analysis of the biomechanical behavior of implant-supported maxillary fixed total prostheses made by milling and 3D printing

Author(s)

Daniele Valente Velôso

• Document type: Master's Dissertation
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2020-02-12

Examining board members

Marcelo Ferraz Mesquita; Luciana Valadares Oliveira; Rafael Leonardo Xediek Consani

• Advisor: Marcelo Ferraz Mesquita

Abstract

The aim of this study was compare the biomechanical behavior of all-on-six concept (Ti-6Al-4V) fixed total prosthesis frameworks obtained by three CAD-CAM techniques: Milling; SLM - Selective Laser Melting and EBM – Electron Beam Melting; and verify the effects the application of ceramic coverage and spark erosion on marginal misfit, screw loosening torque and stress distribution (article 1); and masticatory simulation on marginal misfit and screw loosening torque (article 2). A working model was made from an edentulous maxilla prototype. For the manufacturing of framework (all-on-six) a waxing was performed, digitization and thus created a .stl file for the fabrication of the frameworks for proposals technics (n=5). Marginal misfit was evaluated (single screw test). Then, the initial loosening torque was evaluated (0.1 Ncm) digital torque meter. For stress distribution analysis, the extensometry and photoelastic analysis were performed. All frameworks received the application of ceramic coverage, and then the same tests were applied, as described previously. Afterwards, the frameworks were treated with spark erosion, and were again submitted to the proposed tests. Before and after the masticatory simulation (106 cycles, 2Hz / 150N), all samples were evaluated for marginal misfit values and screw loosening torque. The results were submitted to exploratory analysis and appropriate statistical tests. For article 1 - repeated measures ANOVA, and for article 2, two-way ANOVA; both followed by the Bonferroni HSD test ('alfa' = .05). For marginal misfit (µm), before the ceramic coverage, SLM frameworks presented (mean ± standard deviation) higher values (SLM: 186 ± 21; P < .05), differing from the other groups. After ceramic coverage, the highest results were observed in EBM (223 ± 53; P < .05). The ceramic coverage increased marginal misfit values so much for milling group (P = .002), as much as for EBM (P <.001) frameworks; for SLM (P = .002), the values decreased. Spark erosion showed effect only for the EBM group (P = .005), decreasing the marginal misfit values. For the screw loosening torque (Ncm), the milling group presented higher values to the others groups, regardless of the manufacture stage evaluated. Extensometry analysis (µstrain), both ceramic application and spark erosion promoted increase in values strain for SLM frameworks overtime (initial: 103.17 ± 18.17; after ceramic coverage: 169.61 ± 57.10; after spark erosion: 277.83 ± 85.23, P < .05). Photoelastic analysis (MPa) results showed higher values of stress for SLM frameworks at the initial manufacture stage (milling: 501.73 ± 45.16; SLM: 715.97 ± 50.90; EBM: 511.69 ± 47.84); for the milling group, the ceramics coverage increased the stress values (P = .004), while the opposite was found for the SLM (P = .009); the spark erosion no influence on the stress values (P > .05). The masticatory simulation did not affect the marginal misfit values (P > .05); however, for the screw loosening torque, regardless of the time evaluated, the milling group (P <.05) presented higher values than the other groups, which were similar to each other (P > .05), while the EBM group showed a decrease in screw loosening torque values after masticatory simulation (P > .05). In conclusion, the marginal misfit was modified according to the manufacturing stage; the screw loosening torque was higher in milling frameworks; and the tension is little transmitted to the implant-supported system. Masticatory simulation does not influence marginal misfit values; and the milling frameworks show highest results in screw loosening torque. The frameworks manufacturing in 3D presented favorable biomechanical behavior and its use show up is promising for rehabilitation under the all-on-six concept (AU)

• FAPESP's process: 18/10378-4 - Analysis of the biomechanical behavior of implant-supported maxillary fixed total prostheses made by 2 CAD-CAM additive techniques
• Grantee: Daniele Valente Veloso
• Support Opportunities: Scholarships in Brazil - Master