Assessment of flexural strength and fracture of orthodontic mini-implants

•Objective: This study was designed to assess the deformation and fracture of orthodontic miniimplants of different commercial brands by submitting them to loads perpendicularly applied along their lengths. Materials and Methods: A total of 75 mini-implants were divided into five groups (n=15): M (Mondeal, Tuttlingen, Germany), N (Neodent, Curitiba, Brasil), I (INP, São Paulo, Brazil), S (SIN, São Paulo, Brazil), and T (Titanium Fix, São José dos Campos, Brazil). The mini-implants were inserted perpendicularly into swine cortical bones and submitted to mechanical tests using an Emic DL 10.000 universal testing machine at cross-speed of 0.5mm/ min. The different forces required to fracture mini-implants after undergoing 0.5mm, 1mm, 1.5mm and 2mm deformation was assessed. The data were assessed using analysis of variance (ANOVA) and Tukey’s test. Results: Mini-implants in Group S required the greatest forces to deform and fracture. These results were statistically significant in comparison with the othergroups (P<.05) which required lower forces to deform and fracture. Group M yielded the lowest distortion values but with no significant statistical difference compared to Group N (P>.05), whereas Group T required the lowest fracture values with statistical difference compared to Groups M, S and I. Conclusions: It is possible to conclude, based on the results of the present study, that the shape and flexural strength of mini-implants bear direct correlation with each other. Despite their different flexural strength levels all mini-implants proved effective in clinical use.