Structure-properties correlation of new mini-implant models obtained by machining and additive manufacturing

Author(s)

Thaisa Theodoro de Oliveira

• Document type: Master's Dissertation
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Odontologia de Ribeirão Preto (PCARP/BC)
• Defense date: 2020-01-14

Examining board members

Andréa Candido dos Reis; Ana Flávia Sanches Borges; José Fernando Scarelli Lopes; Ligia Antunes Pereira Pinelli

• Advisor: Andréa Candido dos Reis

Abstract

Implantology has made great progress in the rehabilitation of edentulous patients with great bone resorption, with low retention and stability in cases of conventional complete dentures. Mini-implants are an option for patients with narrow alveolar ridges, allowing greater simplicity of surgical procedures, minimizing the need for flaps and grafts, with less postoperative morbidity and reduced cost. The association of mini-implants and new technologies such as additive manufacturing or 3D printing can contribute to advances in dental treatment, allowing the manufacture of future personalized implants, with reduced rehabilitation time and tissue preservation. The objective of the present work was to propose the manufacture of a new mini-implant design to support overdenture through the additive manufacturing technology, and to compare it through the structure-properties correlation with mini-implants obtained by machining. To obtain mini-implants by additive manufacture, technical drawings were prepared by specialized professionals and these were converted into .stl files. The manufacturing was made by Ti6Al4V alloy powder by Selective Laser Fusion (SLM), performed by the REALIZER GmbH SLM 50® equipment. Four models of mini-implants with dimensions of Ø 2.0 mm x 10 mm in length were evaluated: Intra-lock, Helical, Threaded Machined (RUS) and Threaded by Additive Manufacturing (RMA) (n = 10). Physical-chemical characterization was performed through morphological analysis using scanning electron microscopy (SEM); chemical composition via X-ray Dispersive Energy Spectroscopy (EDS); primary stability assessment through insertion torque and pullout test; and stress distribution analysis through photoelastic analysis and digital image correlation (CID), with axial and oblique point loading (inclination of 30 ° models), with loads of 100 N for photoelastic analysis and 250 N axial and 100 N oblique in the CID. The distribution of data was verified by the Kolmogorov-Smirnov test. ANOVA analysis of variance tests with Bonferroni correction and Tukey\'s post-hoc tests, and Kruskal-Wallis non-parametric test were applied. Significance level of 5% (&alpha; = 0.05). It was observed the possibility of obtaining mini-implants through the additive manufacturing technique, without loss of alloy elements or addition of contaminant, maintaining the dimensions of the implant, resulting in a visibly rough surface, but with reduced precision of details compared to machined mini-implants. Regarding the primary stability measured through the insertion torque, the RMA mini-implants showed significantly lower values in relation to the RUS and Intra-lock models (p <0.001), and similar in relation to the Helical; similarly in the pullout test, the RMA model had values similar to the Helical model but with significantly lower values than the RUS and Intra-lock models (p <0.001). Regarding photoelasticity and CID, considering the manufacturing method, it was found that additive manufacturing did not interfere with the stress distribution, being similar to the US Threaded model. Regarding macro design, in general, lower tensions were observed in the cervical third and higher tensions with the oblique inclination of the model. (AU)

• FAPESP's process: 18/04894-0 - Structure-properties correlation of new models of mini-implants obtained by machined and additive manufacturing: mechanical properties
• Grantee: Thaisa Theodoro de Oliveira
• Support Opportunities: Scholarships in Brazil - Master