Orthodontic mini-implants (MI) are temporary anchorage devices that have been widely used in dentistry in the last two decades in order to improve control over skeletal anchorage. Titanium alloys (Ti-6Al-4V) are one of the materials of choice for the manufacture of orthodontic mini-implants and are widely used due to their biocompatibility, while stainless steel mini-implants have greater mechanical strength.The objective of this study is to evaluate the differences between the physical and chemical properties of orthodontic mini-implants made of titanium and stainless steel alloys, in order to determine the behavior in relation to primary stability, pullout resistance and concentrations of chemical elements after surface deformation resulting from the pullout test. The study methodology was based on the Checklist for Reporting in vitro Studies - CRIS guidelines. A total of 24 mini-implants will be used, divided into two groups (n=12): stainless steel and titanium. The mini-implants are 2.0 mm in diameter and 12 mm in length, and will be installed in a total of 24 polyurethane blocks, with dimensions of 4.2 cm in thickness, 17.8 cm in width and 6.5 cm in length, with different densities. The polyurethane blocks will be divided into two groups (n=12), referring to titanium (TP) and stainless steel (AP) mini-implants; and divided in relation to density (20 PCF and 40 PCF), being determined n=6 per polyurethane block. The study by Oliscovicz et al., (2013), which evaluated the insertion torque, pullout resistance and resonance frequency of dental implants, was used to obtain parameters for the sample calculation. The primary stability will be evaluated through the evaluation of the insertion torque, through the Kratos digital torquemeter (Kratos Equipamentos Industriais Ltda, Cotia, SP, Brazil). The value at each insertion turn will be measured, and the maximum value obtained will be considered the highest insertion torque. The resonance frequency will be measured through the Osstell® device - to obtain the ISQ stability coefficient (Implant Stability Quotient). Four measurements will be made around each implant, obtaining an average of the values. For analysis of pullout strength, the Universal EMIC Testing Machine model DL-10000N will be used. Each mini-implant will be subjected to an axial traction force with a constant speed of 2 mm/min, and the Tesc 1.13 Software will be used to analyze the results consisting of the 'force × displacement' curve, and the maximum pullout force will be obtained. A SEM equipment with EDS coupled (Carl Zeiss AG - EVO® 50) will be used to analyze the deformation of mini-implants, before installation and after the pullout resistance test. With EDS microanalysis it will be possible to obtain the concentrations of chemical elements. The evaluation of the results will be done through the comparison between the type of specimen and the mini-implant measurements. Cohen's Kappa test will be applied for calibration and quantitative results will be submitted to the Shapiro-Wilk test for data normality analysis. If the data present an unknown distribution (p<0.05), the non-parametric Mann-Whitney tests will be applied to compare groups and the Spearman test to correlate the variables. If the data are normal, Student's T comparison tests will be used, in addition to Pearson's correlation.
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