Avaliação da resistência ao cisalhamento de attachments utilizados em tratamento ortodôntico com alinhadores

Abstract

Introduction: Attachments are a fundamental part of orthodontic treatment with aligners and fracture or fall of these devices can cause delays in orthodontic treatment, causing loss of effectiveness of planned movement and/or aligner tracking. Objective: To evaluate the shear strength of resin composites with different polymerization protocols. Methodology: The study sample consisted of 120 bovine lower incisors that were embedded in acrylic resin and used as a basis for making the attachments. A specimen was digitally scanned and the .stl file was transferred to the ArchForm software (San Jose, California, USA) for planning the rectangular attachment (3mm in length, 1.5 in width and 1mm in height). Subsequently, the specimens were 3D printed and the templates were made in an acetate plate (Orthometric, Marília, São Paulo, Brazil) with a thickness of 0.5 mm. The sample was divided into 3 groups (40 teeth in each group) corresponding to Opallis Flow® resins (FGM, Joinville, Paraná, Brazil), GrandioSO Heavy Flow® (VOCO, Porto Alegre, Rio Grande do Sul, Brazil) and Supreme Flowable Restorative® (3M, Sumaré, São Paulo, Brazil), which were divided into subgroups of polymerization time (10 teeth in each subgroup), as follows: 3 seconds (3,200 mW/cm2), 6 seconds (3,200 mW/cm2 ), 20 seconds (1000 mW/cm2) and 40 seconds (1000 mW/cm2). After installing the attachments, the specimens were subjected to shear testing in an Oswaldo Filizola universal testing machine (Oswaldo Filizola, São Paulo, Brazil), model AME5k, using a 5kN load cell and a speed of 1 mm/min until the fracture of the attachment. Results: The shear test data showed that the “resin” factor (VOCO = 29.2a MPa, FGM = 34.4a MPa, 3M = 43b MPa, p = <.001) and “polymerization time” (3s = 31.2a MPa, 6s = 36.6ab MPa, 20s = 33.3ab MPa and 40s = 40.9b MPa, p = .006) showed significant differences between the groups. In addition, it was observed that there was no interaction between the factors “resin” and “polymerization time”. Conclusion: It was observed that the Supreme Flowable Restorative® resin and the polymerization time for 40s showed the highest shear force in the protocol studied.